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[FFmpeg-devel,2/2] lavfi: Add blurriness filter

Message ID 00ca6f6f-fc18-8b6b-1ff0-f24db7f3714b@mail.de
State New
Headers show
Series [FFmpeg-devel,1/2] lafi/vf_edgedetect: Move some common functions into seperate file | expand

Checks

Context Check Description
andriy/configurex86 warning Failed to apply patch
andriy/configureppc warning Failed to apply patch

Commit Message

Thilo Borgmann Nov. 30, 2021, 1:14 p.m. UTC
Hi,

$subject

-Thilo
From 0fa76024cf921df8a6df77a3860faab9669d0a2e Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Tue, 30 Nov 2021 00:17:44 +0100
Subject: [PATCH 2/2] lavfi: Add blurriness filter

---
 doc/filters.texi            |  55 ++++++
 libavfilter/Makefile        |   1 +
 libavfilter/allfilters.c    |   1 +
 libavfilter/vf_blurriness.c | 366 ++++++++++++++++++++++++++++++++++++
 4 files changed, 423 insertions(+)
 create mode 100644 libavfilter/vf_blurriness.c

Comments

Marton Balint Nov. 30, 2021, 4:11 p.m. UTC | #1
On Tue, 30 Nov 2021, Thilo Borgmann wrote:

> Hi,
>
> $subject

Can you name this blurdetect to be more in line with existing similar 
filters? (blackdetect, freezedetect)

Thanks,
Marton
Thilo Borgmann Nov. 30, 2021, 5:19 p.m. UTC | #2
Am 30.11.21 um 17:11 schrieb Marton Balint:
> 
> 
> On Tue, 30 Nov 2021, Thilo Borgmann wrote:
> 
>> Hi,
>>
>> $subject
> 
> Can you name this blurdetect to be more in line with existing similar filters? (blackdetect, freezedetect)

Totally will in the next version.

Thanks,
Thilo
Thilo Borgmann April 4, 2022, 10:25 a.m. UTC | #3
Hi,

v3 updated to current HEAD.

Named blurdetect filter now.
Minor fixes on allocation and removed -f option.

-Thilo
From 1c81cf6f0586a3cc670e6d8354f35e5bdbe2a282 Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Mon, 4 Apr 2022 12:21:14 +0200
Subject: [PATCH v3 2/2] lavfi: Add blurdetect filter

---
 doc/filters.texi            |  49 +++++
 libavfilter/Makefile        |   1 +
 libavfilter/allfilters.c    |   1 +
 libavfilter/vf_blurdetect.c | 368 ++++++++++++++++++++++++++++++++++++
 4 files changed, 419 insertions(+)
 create mode 100644 libavfilter/vf_blurdetect.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 636c80dbff..f15fb719d5 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -7990,6 +7990,55 @@ tblend=all_mode=grainextract
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@anchor{blurdetect}
+@section blurdetect
+
+Determines blurriness of frames without altering the input frames.
+
+Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric."
+Allows for a block-based abbreviation.
+
+The filter accepts the following options:
+
+@table @option
+@item low
+@item high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be chosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+
+@item radius
+Define the radius to search around an edge pixel for local maxima.
+
+@item block_pct
+Determine blurriness only for the most significant blocks, given in percentage.
+
+@item block_width
+Determine blurriness for blocks of width @var{block_width}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_height}.
+
+@item block_height
+Determine blurriness for blocks of height @var{block_height}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_width}.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Determine blur for 80% of most significant 32x32 blocks:
+@example
+blurdetect=block_width=32:block_height=32:block_pct=80
+@end example
+@end itemize
+
 @section bm3d
 
 Denoise frames using Block-Matching 3D algorithm.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 006e59b2bd..6332a6f799 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -195,6 +195,7 @@ OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o framesync.o
 OBJS-$(CONFIG_BLEND_VULKAN_FILTER)           += vf_blend_vulkan.o framesync.o vulkan.o vulkan_filter.o
+OBJS-$(CONFIG_BLURDETECT_FILTER)             += vf_blurdetect.o edge_common.o
 OBJS-$(CONFIG_BM3D_FILTER)                   += vf_bm3d.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o boxblur.o
 OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 9fbaaacf47..2667d153ad 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -183,6 +183,7 @@ extern const AVFilter ff_vf_blackdetect;
 extern const AVFilter ff_vf_blackframe;
 extern const AVFilter ff_vf_blend;
 extern const AVFilter ff_vf_blend_vulkan;
+extern const AVFilter ff_vf_blurdetect;
 extern const AVFilter ff_vf_bm3d;
 extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
diff --git a/libavfilter/vf_blurdetect.c b/libavfilter/vf_blurdetect.c
new file mode 100644
index 0000000000..050cec9529
--- /dev/null
+++ b/libavfilter/vf_blurdetect.c
@@ -0,0 +1,368 @@
+/*
+ * Copyright (c) 2021 Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * No-reference blurdetect filter
+ *
+ * Implementing:
+ * Marziliano, Pina, et al. "A no-reference perceptual blur metric." Proceedings.
+ * International conference on image processing. Vol. 3. IEEE, 2002.
+ * https://infoscience.epfl.ch/record/111802/files/14%20A%20no-reference%20perceptual%20blur%20metric.pdf
+ *
+ * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixelutils.h"
+#include "libavutil/motion_vector.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "edge_common.h"
+
+static int comp(const void *a,const void *b)
+{
+    float x = *(float*)a;
+    float y = *(float*)b;
+    if (x > y) return  1;
+    if (x < y) return -1;
+    return 0;
+}
+
+typedef struct BLRContext {
+    const AVClass *class;
+
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    int     radius;        // radius during local maxima detection
+    int     block_pct;     // percentage of "sharpest" blocks in the image to use for bluriness calculation
+    int     block_width;   // width for block abbreviation
+    int     block_height;  // height for block abbreviation
+
+    double   blur_total;
+    uint64_t nb_frames;
+
+    float    *blks;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+} BLRContext;
+
+#define OFFSET(x) offsetof(BLRContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption blr_options[] = {
+    { "high",          "set high threshold", OFFSET(high), AV_OPT_TYPE_FLOAT, {.dbl=30/255.}, 0, 1, FLAGS },
+    { "low",           "set low threshold",  OFFSET(low),  AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "radius",        "search radius for maxima detection", OFFSET(radius), AV_OPT_TYPE_INT, {.i64=50}, 1, 100, FLAGS },
+    { "block_pct",     "block pooling threshold when calculating blurriness", OFFSET(block_pct), AV_OPT_TYPE_INT, {.i64=80}, 1, 100, FLAGS },
+    { "block_width",   "block size for block-based abbreviation of blurriness", OFFSET(block_width), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "block_height",  "block size for block-based abbreviation of blurriness", OFFSET(block_height), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blr);
+
+static av_cold int blr_init(AVFilterContext *ctx)
+{
+    BLRContext *blr = ctx->priv;
+
+    blr->low_u8  = blr->low  * 255. + .5;
+    blr->high_u8 = blr->high * 255. + .5;
+
+    return 0;
+}
+
+static int blr_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx    = inlink->dst;
+    BLRContext      *blr    = ctx->priv;
+    const int       bufsize = inlink->w * inlink->h;
+
+    if (blr->block_width  < 1 || blr->block_height < 1) {
+        blr->block_width  = inlink->w;
+        blr->block_height = inlink->h;
+    }
+
+    blr->tmpbuf     = av_malloc(bufsize);
+    blr->filterbuf  = av_malloc(bufsize);
+    blr->gradients  = av_calloc(bufsize, sizeof(*blr->gradients));
+    blr->directions = av_malloc(bufsize);
+    blr->blks       = av_calloc((inlink->w / blr->block_width) * (inlink->h / blr->block_height),
+                                sizeof(*blr->blks));
+
+    if (!blr->tmpbuf || !blr->filterbuf || !blr->gradients ||
+        !blr->directions || !blr->blks)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+// edge width is defined as the distance between surrounding maxima of the edge pixel
+static float edge_width(BLRContext *blr, int i, int j, int8_t dir, int w, int h,
+                        int edge, const uint8_t *src, int src_linesize)
+{
+    float width = 0;
+    int dX, dY;
+    int sign;
+    int tmp;
+    int p1;
+    int p2;
+    int k, x, y;
+    int edge1;
+    int edge2;
+    float luma1 = 0.0; // average luma difference per edge pixel
+    float luma2 = 0.0;
+    int radius = blr->radius;
+
+    switch(dir)
+    {
+    case DIRECTION_HORIZONTAL: dX = 1; dY =  0; break;
+    case DIRECTION_VERTICAL:   dX = 0; dY =  1; break;
+    case DIRECTION_45UP:       dX = 1; dY = -1; break;
+    case DIRECTION_45DOWN:     dX = 1; dY =  1; break;
+    }
+    if (dir == DIRECTION_HORIZONTAL) return 0;
+
+    // determines if search in direction dX/dY is looking for a maximum or minimum
+    sign = src[j * src_linesize + i] > src[(j - dY) * src_linesize + i - dX] ? 1 : -1;
+
+    // search in -(dX/dY) direction
+    for (k = 0; k < radius; k++)
+    {
+        x = i - k*dX;
+        y = j - k*dY;
+        p1 = y * src_linesize + x;
+        x -= dX;
+        y -= dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp <= 0) // local maximum found
+            break;
+
+        luma1 += tmp;
+    }
+    if (k > 0) luma1 /= k;
+    edge1 = k;
+    width += k;
+
+    // search in +(dX/dY) direction
+    for (k = 0; k < radius; k++)
+    {
+        x = i + k * dX;
+        y = j + k * dY;
+        p1 = y * src_linesize + x;
+        x += dX;
+        y += dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp >= 0) // local maximum found
+            break;
+
+        luma2 -= tmp;
+    }
+    if (k > 0) luma2 /= k;
+    edge2 = k;
+    width += k;
+
+    // for 45 degree directions approximate edge width in pixel units: 0.7 ~= sqrt(2)/2
+    if (dir == DIRECTION_45UP || dir == DIRECTION_45DOWN)
+        width *= 0.7;
+
+    return width;
+}
+
+static float calculate_blur(BLRContext *blr, int w, int h,
+                            uint8_t* dir, int dir_linesize,
+                            uint8_t* dst, int dst_linesize,
+                            uint8_t* src, int src_linesize)
+{
+    float total_width = 0.0;
+    int block_count;
+    float block_total_width;
+
+    int i, j;
+    int blkcnt = 0;
+
+    float *blks = blr->blks;
+    int block_pct = blr->block_pct;
+    float block_pool_threshold = block_pct / 100.0;
+
+    int block_width  = blr->block_width;
+    int block_height = blr->block_height;
+    int brows = h / block_height;
+    int bcols = w / block_width;
+
+    for (int blkj = 0; blkj < brows; blkj++) {
+        for (int blki = 0; blki < bcols; blki++) {
+            block_total_width = 0;
+            block_count = 0;
+            for (int inj = 0; inj < block_height; inj++) {
+                for (int ini = 0; ini < block_width; ini++) {
+                    i = blki * block_width + ini;
+                    j = blkj * block_height + inj;
+
+                    if (dst[j * dst_linesize + i] > 0) {
+                        float width = edge_width(blr, i, j, dir[j*dir_linesize+i],
+                                                 w, h, dst[j*dst_linesize+i],
+                                                 src, src_linesize);
+                        if (width > 0.001) { // throw away zeros
+                            block_count++;
+                            block_total_width += width;
+                        }
+                    }
+                }
+            }
+            // if not enough edge pixels in a block, consider it smooth
+            if (block_total_width >= 2) {
+                blks[blkcnt] = block_total_width / block_count;
+                blkcnt++;
+            }
+        }
+    }
+
+    // simple block pooling by sorting and keeping the sharper blocks
+    qsort(blks, blkcnt, sizeof(*blks), comp);
+    blkcnt = ceil(blkcnt * block_pool_threshold);
+    for (int i = 0; i < blkcnt; i++) {
+        total_width += blks[i];
+    }
+
+    return  total_width / blkcnt;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    av_dict_set(metadata, key, value, 0);
+}
+
+static int blr_filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BLRContext *blr      = ctx->priv;
+
+    const int w = inlink->w;
+    const int h = inlink->h;
+
+    uint8_t *tmpbuf     = blr->tmpbuf;
+    uint8_t *filterbuf  = blr->filterbuf;
+    uint16_t *gradients = blr->gradients;
+    int8_t *directions  = blr->directions;
+
+    float blur;
+    AVDictionary **metadata;
+    metadata = &in->metadata;
+
+    // gaussian filter to reduce noise
+    ff_gaussian_blur(w, h,
+                     filterbuf,  w,
+                     in->data[0], in->linesize[0]);
+
+    // compute the 16-bits gradients and directions for the next step
+    ff_sobel(w, h, gradients, w, directions, w, filterbuf, w);
+
+    // non_maximum_suppression() will actually keep & clip what's necessary and
+    // ignore the rest, so we need a clean output buffer
+    memset(tmpbuf, 0, w * h);
+    ff_non_maximum_suppression(w, h, tmpbuf, w, directions, w, gradients, w);
+
+
+    // keep high values, or low values surrounded by high values
+    ff_double_threshold(blr->low_u8, blr->high_u8, w, h,
+                              tmpbuf, w, tmpbuf, w);
+
+
+    blur = calculate_blur(blr, w, h, directions, w,
+                          tmpbuf, w, filterbuf, w);
+
+    blr->blur_total += blur;
+
+    // write stats
+    av_log(ctx, AV_LOG_VERBOSE, "blur: %.7f\n", blur);
+
+    set_meta(metadata, "lavfi.blur", blur);
+
+    blr->nb_frames++;
+
+    return ff_filter_frame(ctx->outputs[0], in);
+}
+
+static av_cold void blr_uninit(AVFilterContext *ctx)
+{
+    BLRContext *blr = ctx->priv;
+
+    if (blr->nb_frames > 0) {
+        int nb_frames = blr->nb_frames;
+        av_log(ctx, AV_LOG_INFO, "blur mean: %.7f\n",
+               blr->blur_total / nb_frames);
+    }
+
+    av_freep(&blr->tmpbuf);
+    av_freep(&blr->filterbuf);
+    av_freep(&blr->gradients);
+    av_freep(&blr->directions);
+    av_freep(&blr->blks);
+}
+
+static const enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
+
+static const AVFilterPad blr_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = blr_config_input,
+        .filter_frame = blr_filter_frame,
+    },
+};
+
+static const AVFilterPad blr_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+AVFilter ff_vf_blurdetect = {
+    .name          = "blurdetect",
+    .description   = NULL_IF_CONFIG_SMALL("Blurdetect filter."),
+    .priv_size     = sizeof(BLRContext),
+    .init          = blr_init,
+    .uninit        = blr_uninit,
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    FILTER_INPUTS(blr_inputs),
+    FILTER_OUTPUTS(blr_outputs),
+    .priv_class    = &blr_class,
+    .flags         = AVFILTER_FLAG_METADATA_ONLY,
+};
+
Paul B Mahol April 4, 2022, 10:42 a.m. UTC | #4
On Mon, Apr 4, 2022 at 12:25 PM Thilo Borgmann <thilo.borgmann@mail.de>
wrote:

> Hi,
>
> v3 updated to current HEAD.
>
> Named blurdetect filter now.
> Minor fixes on allocation and removed -f option.
>

Please make this per plane filtering, with default to measure only first
plane.


> -Thilo_______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
Thilo Borgmann April 5, 2022, 8:56 a.m. UTC | #5
Hi,

>> v3 updated to current HEAD.
>>
>> Named blurdetect filter now.
>> Minor fixes on allocation and removed -f option.
>>
> 
> Please make this per plane filtering, with default to measure only first
> plane.

done in v4.

(Will add Changelog, version.h and fate test once the filter itself looks ok)

Thanks,
Thilo
From 6411603fe86d4fb6a781aec2ff48e48be12d269e Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Tue, 5 Apr 2022 10:54:19 +0200
Subject: [PATCH v4 2/2] lavfi: Add blurdetect filter

---
 doc/filters.texi            |  52 +++++
 libavfilter/Makefile        |   1 +
 libavfilter/allfilters.c    |   1 +
 libavfilter/vf_blurdetect.c | 394 ++++++++++++++++++++++++++++++++++++
 4 files changed, 448 insertions(+)
 create mode 100644 libavfilter/vf_blurdetect.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 636c80dbff..c6d4537804 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -7990,6 +7990,58 @@ tblend=all_mode=grainextract
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@anchor{blurdetect}
+@section blurdetect
+
+Determines blurriness of frames without altering the input frames.
+
+Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric."
+Allows for a block-based abbreviation.
+
+The filter accepts the following options:
+
+@table @option
+@item low
+@item high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be chosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+
+@item radius
+Define the radius to search around an edge pixel for local maxima.
+
+@item block_pct
+Determine blurriness only for the most significant blocks, given in percentage.
+
+@item block_width
+Determine blurriness for blocks of width @var{block_width}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_height}.
+
+@item block_height
+Determine blurriness for blocks of height @var{block_height}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_width}.
+
+@item planes
+Set planes to filter. Default is first only.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Determine blur for 80% of most significant 32x32 blocks:
+@example
+blurdetect=block_width=32:block_height=32:block_pct=80
+@end example
+@end itemize
+
 @section bm3d
 
 Denoise frames using Block-Matching 3D algorithm.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 006e59b2bd..6332a6f799 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -195,6 +195,7 @@ OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o framesync.o
 OBJS-$(CONFIG_BLEND_VULKAN_FILTER)           += vf_blend_vulkan.o framesync.o vulkan.o vulkan_filter.o
+OBJS-$(CONFIG_BLURDETECT_FILTER)             += vf_blurdetect.o edge_common.o
 OBJS-$(CONFIG_BM3D_FILTER)                   += vf_bm3d.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o boxblur.o
 OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 9fbaaacf47..2667d153ad 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -183,6 +183,7 @@ extern const AVFilter ff_vf_blackdetect;
 extern const AVFilter ff_vf_blackframe;
 extern const AVFilter ff_vf_blend;
 extern const AVFilter ff_vf_blend_vulkan;
+extern const AVFilter ff_vf_blurdetect;
 extern const AVFilter ff_vf_bm3d;
 extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
diff --git a/libavfilter/vf_blurdetect.c b/libavfilter/vf_blurdetect.c
new file mode 100644
index 0000000000..71e46fa962
--- /dev/null
+++ b/libavfilter/vf_blurdetect.c
@@ -0,0 +1,394 @@
+/*
+ * Copyright (c) 2021 Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * No-reference blurdetect filter
+ *
+ * Implementing:
+ * Marziliano, Pina, et al. "A no-reference perceptual blur metric." Proceedings.
+ * International conference on image processing. Vol. 3. IEEE, 2002.
+ * https://infoscience.epfl.ch/record/111802/files/14%20A%20no-reference%20perceptual%20blur%20metric.pdf
+ *
+ * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixelutils.h"
+#include "libavutil/motion_vector.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "edge_common.h"
+
+static int comp(const void *a,const void *b)
+{
+    float x = *(float*)a;
+    float y = *(float*)b;
+    if (x > y) return  1;
+    if (x < y) return -1;
+    return 0;
+}
+
+typedef struct BLRContext {
+    const AVClass *class;
+
+    int hsub, vsub;
+    int nb_planes;
+
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    int     radius;        // radius during local maxima detection
+    int     block_pct;     // percentage of "sharpest" blocks in the image to use for bluriness calculation
+    int     block_width;   // width for block abbreviation
+    int     block_height;  // height for block abbreviation
+    int     planes;        // number of planes to filter
+
+    double   blur_total;
+    uint64_t nb_frames;
+
+    float    *blks;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+} BLRContext;
+
+#define OFFSET(x) offsetof(BLRContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption blr_options[] = {
+    { "high",          "set high threshold", OFFSET(high), AV_OPT_TYPE_FLOAT, {.dbl=30/255.}, 0, 1, FLAGS },
+    { "low",           "set low threshold",  OFFSET(low),  AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "radius",        "search radius for maxima detection", OFFSET(radius), AV_OPT_TYPE_INT, {.i64=50}, 1, 100, FLAGS },
+    { "block_pct",     "block pooling threshold when calculating blurriness", OFFSET(block_pct), AV_OPT_TYPE_INT, {.i64=80}, 1, 100, FLAGS },
+    { "block_width",   "block size for block-based abbreviation of blurriness", OFFSET(block_width), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "block_height",  "block size for block-based abbreviation of blurriness", OFFSET(block_height), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "planes",        "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT, {.i64=1}, 0, 15, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blr);
+
+static av_cold int blr_init(AVFilterContext *ctx)
+{
+    BLRContext *blr = ctx->priv;
+
+    blr->low_u8  = blr->low  * 255. + .5;
+    blr->high_u8 = blr->high * 255. + .5;
+
+    return 0;
+}
+
+static int blr_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BLRContext      *blr = ctx->priv;
+    const int bufsize    = inlink->w * inlink->h;
+    const AVPixFmtDescriptor *pix_desc;
+
+    pix_desc = av_pix_fmt_desc_get(inlink->format);
+    blr->hsub = pix_desc->log2_chroma_w;
+    blr->vsub = pix_desc->log2_chroma_h;
+    blr->nb_planes = av_pix_fmt_count_planes(inlink->format);
+
+    if (blr->block_width  < 1 || blr->block_height < 1) {
+        blr->block_width  = inlink->w;
+        blr->block_height = inlink->h;
+    }
+
+    blr->tmpbuf     = av_malloc(bufsize);
+    blr->filterbuf  = av_malloc(bufsize);
+    blr->gradients  = av_calloc(bufsize, sizeof(*blr->gradients));
+    blr->directions = av_malloc(bufsize);
+    blr->blks       = av_calloc((inlink->w / blr->block_width) * (inlink->h / blr->block_height),
+                                sizeof(*blr->blks));
+
+    if (!blr->tmpbuf || !blr->filterbuf || !blr->gradients ||
+        !blr->directions || !blr->blks)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+// edge width is defined as the distance between surrounding maxima of the edge pixel
+static float edge_width(BLRContext *blr, int i, int j, int8_t dir, int w, int h,
+                        int edge, const uint8_t *src, int src_linesize)
+{
+    float width = 0;
+    int dX, dY;
+    int sign;
+    int tmp;
+    int p1;
+    int p2;
+    int k, x, y;
+    int edge1;
+    int edge2;
+    float luma1 = 0.0; // average luma difference per edge pixel
+    float luma2 = 0.0;
+    int radius = blr->radius;
+
+    switch(dir)
+    {
+    case DIRECTION_HORIZONTAL: dX = 1; dY =  0; break;
+    case DIRECTION_VERTICAL:   dX = 0; dY =  1; break;
+    case DIRECTION_45UP:       dX = 1; dY = -1; break;
+    case DIRECTION_45DOWN:     dX = 1; dY =  1; break;
+    }
+    if (dir == DIRECTION_HORIZONTAL) return 0;
+
+    // determines if search in direction dX/dY is looking for a maximum or minimum
+    sign = src[j * src_linesize + i] > src[(j - dY) * src_linesize + i - dX] ? 1 : -1;
+
+    // search in -(dX/dY) direction
+    for (k = 0; k < radius; k++)
+    {
+        x = i - k*dX;
+        y = j - k*dY;
+        p1 = y * src_linesize + x;
+        x -= dX;
+        y -= dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp <= 0) // local maximum found
+            break;
+
+        luma1 += tmp;
+    }
+    if (k > 0) luma1 /= k;
+    edge1 = k;
+    width += k;
+
+    // search in +(dX/dY) direction
+    for (k = 0; k < radius; k++)
+    {
+        x = i + k * dX;
+        y = j + k * dY;
+        p1 = y * src_linesize + x;
+        x += dX;
+        y += dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp >= 0) // local maximum found
+            break;
+
+        luma2 -= tmp;
+    }
+    if (k > 0) luma2 /= k;
+    edge2 = k;
+    width += k;
+
+    // for 45 degree directions approximate edge width in pixel units: 0.7 ~= sqrt(2)/2
+    if (dir == DIRECTION_45UP || dir == DIRECTION_45DOWN)
+        width *= 0.7;
+
+    return width;
+}
+
+static float calculate_blur(BLRContext *blr, int w, int h, int hsub, int vsub,
+                            uint8_t* dir, int dir_linesize,
+                            uint8_t* dst, int dst_linesize,
+                            uint8_t* src, int src_linesize)
+{
+    float total_width = 0.0;
+    int block_count;
+    double block_total_width;
+
+    int i, j;
+    int blkcnt = 0;
+
+    float *blks = blr->blks;
+    float block_pool_threshold = blr->block_pct / 100.0;
+
+    int block_width  = AV_CEIL_RSHIFT(blr->block_width,  hsub);
+    int block_height = AV_CEIL_RSHIFT(blr->block_height, vsub);
+    int brows = h / block_height;
+    int bcols = w / block_width;
+
+    for (int blkj = 0; blkj < brows; blkj++) {
+        for (int blki = 0; blki < bcols; blki++) {
+            block_total_width = 0.0;
+            block_count = 0;
+            for (int inj = 0; inj < block_height; inj++) {
+                for (int ini = 0; ini < block_width; ini++) {
+                    i = blki * block_width + ini;
+                    j = blkj * block_height + inj;
+
+                    if (dst[j * dst_linesize + i] > 0) {
+                        float width = edge_width(blr, i, j, dir[j*dir_linesize+i],
+                                                 w, h, dst[j*dst_linesize+i],
+                                                 src, src_linesize);
+                        if (width > 0.001) { // throw away zeros
+                            block_count++;
+                            block_total_width += width;
+                        }
+                    }
+                }
+            }
+            // if not enough edge pixels in a block, consider it smooth
+            if (block_total_width >= 2) {
+                blks[blkcnt] = block_total_width / block_count;
+                blkcnt++;
+            }
+        }
+    }
+
+    // simple block pooling by sorting and keeping the sharper blocks
+    qsort(blks, blkcnt, sizeof(*blks), comp);
+    blkcnt = ceil(blkcnt * block_pool_threshold);
+    for (int i = 0; i < blkcnt; i++) {
+        total_width += blks[i];
+    }
+
+    return  total_width / blkcnt;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    av_dict_set(metadata, key, value, 0);
+}
+
+static int blr_filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx  = inlink->dst;
+    BLRContext *blr       = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+
+    const int inw = inlink->w;
+    const int inh = inlink->h;
+
+    uint8_t *tmpbuf     = blr->tmpbuf;
+    uint8_t *filterbuf  = blr->filterbuf;
+    uint16_t *gradients = blr->gradients;
+    int8_t *directions  = blr->directions;
+
+    float blur = 0.0f;
+    int nplanes = 0;
+    AVDictionary **metadata;
+    metadata = &in->metadata;
+
+    for (int plane = 0; plane < blr->nb_planes; plane++) {
+        int hsub = plane == 1 || plane == 2 ? blr->hsub : 0;
+        int vsub = plane == 1 || plane == 2 ? blr->vsub : 0;
+        int w = AV_CEIL_RSHIFT(inw, hsub);
+        int h = AV_CEIL_RSHIFT(inh, vsub);
+
+        if (!((1 << plane) & blr->planes))
+            continue;
+
+        nplanes++;
+
+        // gaussian filter to reduce noise
+        ff_gaussian_blur(w, h,
+                         filterbuf,  w,
+                         in->data[plane], in->linesize[plane]);
+
+        // compute the 16-bits gradients and directions for the next step
+        ff_sobel(w, h, gradients, w, directions, w, filterbuf, w);
+
+        // non_maximum_suppression() will actually keep & clip what's necessary and
+        // ignore the rest, so we need a clean output buffer
+        memset(tmpbuf, 0, inw * inh);
+        ff_non_maximum_suppression(w, h, tmpbuf, w, directions, w, gradients, w);
+
+
+        // keep high values, or low values surrounded by high values
+        ff_double_threshold(blr->low_u8, blr->high_u8, w, h,
+                            tmpbuf, w, tmpbuf, w);
+
+        blur += calculate_blur(blr, w, h, hsub, vsub, directions, w,
+                              tmpbuf, w, filterbuf, w);
+    }
+
+    if (nplanes)
+        blur /= nplanes;
+
+    blr->blur_total += blur;
+
+    // write stats
+    av_log(ctx, AV_LOG_VERBOSE, "blur: %.7f\n", blur);
+
+    set_meta(metadata, "lavfi.blur", blur);
+
+    blr->nb_frames++;
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void blr_uninit(AVFilterContext *ctx)
+{
+    BLRContext *blr = ctx->priv;
+
+    if (blr->nb_frames > 0) {
+        int nb_frames = blr->nb_frames;
+        av_log(ctx, AV_LOG_INFO, "blur mean: %.7f\n",
+               blr->blur_total / nb_frames);
+    }
+
+    av_freep(&blr->tmpbuf);
+    av_freep(&blr->filterbuf);
+    av_freep(&blr->gradients);
+    av_freep(&blr->directions);
+    av_freep(&blr->blks);
+}
+
+static const enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
+
+static const AVFilterPad blr_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = blr_config_input,
+        .filter_frame = blr_filter_frame,
+    },
+};
+
+static const AVFilterPad blr_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+AVFilter ff_vf_blurdetect = {
+    .name          = "blurdetect",
+    .description   = NULL_IF_CONFIG_SMALL("Blurdetect filter."),
+    .priv_size     = sizeof(BLRContext),
+    .init          = blr_init,
+    .uninit        = blr_uninit,
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    FILTER_INPUTS(blr_inputs),
+    FILTER_OUTPUTS(blr_outputs),
+    .priv_class    = &blr_class,
+    .flags         = AVFILTER_FLAG_METADATA_ONLY,
+};
+
Thilo Borgmann April 14, 2022, 8:08 a.m. UTC | #6
Am 05.04.22 um 10:56 schrieb Thilo Borgmann:
> Hi,
> 
>>> v3 updated to current HEAD.
>>>
>>> Named blurdetect filter now.
>>> Minor fixes on allocation and removed -f option.
>>>
>>
>> Please make this per plane filtering, with default to measure only first
>> plane.
> 
> done in v4.
> 
> (Will add Changelog, version.h and fate test once the filter itself looks ok)

Ping.

-Thilo
Thilo Borgmann April 23, 2022, 1:32 p.m. UTC | #7
Hi,

>>>> v3 updated to current HEAD.
>>>>
>>>> Named blurdetect filter now.
>>>> Minor fixes on allocation and removed -f option.
>>>>
>>>
>>> Please make this per plane filtering, with default to measure only first
>>> plane.
>>
>> done in v4.
>>
>> (Will add Changelog, version.h and fate test once the filter itself looks ok)
> 
> Ping.

v5 according to IRC comments.

-Thilo
From be0bed07d36d957caf328f91a6cd0402c27fb6b4 Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Sat, 23 Apr 2022 15:29:36 +0200
Subject: [PATCH v5 2/2] lavfi: Add blurdetect filter

---
 doc/filters.texi            |  52 +++++
 libavfilter/Makefile        |   1 +
 libavfilter/allfilters.c    |   1 +
 libavfilter/vf_blurdetect.c | 395 ++++++++++++++++++++++++++++++++++++
 4 files changed, 449 insertions(+)
 create mode 100644 libavfilter/vf_blurdetect.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 636c80dbff..c6d4537804 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -7990,6 +7990,58 @@ tblend=all_mode=grainextract
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@anchor{blurdetect}
+@section blurdetect
+
+Determines blurriness of frames without altering the input frames.
+
+Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric."
+Allows for a block-based abbreviation.
+
+The filter accepts the following options:
+
+@table @option
+@item low
+@item high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be chosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+
+@item radius
+Define the radius to search around an edge pixel for local maxima.
+
+@item block_pct
+Determine blurriness only for the most significant blocks, given in percentage.
+
+@item block_width
+Determine blurriness for blocks of width @var{block_width}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_height}.
+
+@item block_height
+Determine blurriness for blocks of height @var{block_height}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_width}.
+
+@item planes
+Set planes to filter. Default is first only.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Determine blur for 80% of most significant 32x32 blocks:
+@example
+blurdetect=block_width=32:block_height=32:block_pct=80
+@end example
+@end itemize
+
 @section bm3d
 
 Denoise frames using Block-Matching 3D algorithm.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 006e59b2bd..6332a6f799 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -195,6 +195,7 @@ OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o framesync.o
 OBJS-$(CONFIG_BLEND_VULKAN_FILTER)           += vf_blend_vulkan.o framesync.o vulkan.o vulkan_filter.o
+OBJS-$(CONFIG_BLURDETECT_FILTER)             += vf_blurdetect.o edge_common.o
 OBJS-$(CONFIG_BM3D_FILTER)                   += vf_bm3d.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o boxblur.o
 OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 9fbaaacf47..2667d153ad 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -183,6 +183,7 @@ extern const AVFilter ff_vf_blackdetect;
 extern const AVFilter ff_vf_blackframe;
 extern const AVFilter ff_vf_blend;
 extern const AVFilter ff_vf_blend_vulkan;
+extern const AVFilter ff_vf_blurdetect;
 extern const AVFilter ff_vf_bm3d;
 extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
diff --git a/libavfilter/vf_blurdetect.c b/libavfilter/vf_blurdetect.c
new file mode 100644
index 0000000000..c74f45ccb8
--- /dev/null
+++ b/libavfilter/vf_blurdetect.c
@@ -0,0 +1,395 @@
+/*
+ * Copyright (c) 2021 Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * No-reference blurdetect filter
+ *
+ * Implementing:
+ * Marziliano, Pina, et al. "A no-reference perceptual blur metric." Proceedings.
+ * International conference on image processing. Vol. 3. IEEE, 2002.
+ * https://infoscience.epfl.ch/record/111802/files/14%20A%20no-reference%20perceptual%20blur%20metric.pdf
+ *
+ * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixelutils.h"
+#include "libavutil/motion_vector.h"
+#include "libavutil/qsort.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "edge_common.h"
+
+static int comp(const float *a,const float *b)
+{
+    return FFDIFFSIGN(*a, *b);
+}
+
+typedef struct BLRContext {
+    const AVClass *class;
+
+    int hsub, vsub;
+    int nb_planes;
+
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    int     radius;        // radius during local maxima detection
+    int     block_pct;     // percentage of "sharpest" blocks in the image to use for bluriness calculation
+    int     block_width;   // width for block abbreviation
+    int     block_height;  // height for block abbreviation
+    int     planes;        // number of planes to filter
+
+    double   blur_total;
+    uint64_t nb_frames;
+
+    float    *blks;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+} BLRContext;
+
+#define OFFSET(x) offsetof(BLRContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption blurdetect_options[] = {
+    { "high",          "set high threshold", OFFSET(high), AV_OPT_TYPE_FLOAT, {.dbl=30/255.}, 0, 1, FLAGS },
+    { "low",           "set low threshold",  OFFSET(low),  AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "radius",        "search radius for maxima detection", OFFSET(radius), AV_OPT_TYPE_INT, {.i64=50}, 1, 100, FLAGS },
+    { "block_pct",     "block pooling threshold when calculating blurriness", OFFSET(block_pct), AV_OPT_TYPE_INT, {.i64=80}, 1, 100, FLAGS },
+    { "block_width",   "block size for block-based abbreviation of blurriness", OFFSET(block_width), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "block_height",  "block size for block-based abbreviation of blurriness", OFFSET(block_height), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "planes",        "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT, {.i64=1}, 0, 15, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blurdetect);
+
+static av_cold int blurdetect_init(AVFilterContext *ctx)
+{
+    BLRContext *s = ctx->priv;
+
+    s->low_u8  = s->low  * 255. + .5;
+    s->high_u8 = s->high * 255. + .5;
+
+    return 0;
+}
+
+static int blurdetect_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BLRContext      *s   = ctx->priv;
+    const int bufsize    = inlink->w * inlink->h;
+    const AVPixFmtDescriptor *pix_desc;
+
+    pix_desc = av_pix_fmt_desc_get(inlink->format);
+    s->hsub = pix_desc->log2_chroma_w;
+    s->vsub = pix_desc->log2_chroma_h;
+    s->nb_planes = av_pix_fmt_count_planes(inlink->format);
+
+    if (s->block_width  < 1 || s->block_height < 1) {
+        s->block_width  = inlink->w;
+        s->block_height = inlink->h;
+    }
+
+    s->tmpbuf     = av_malloc(bufsize);
+    s->filterbuf  = av_malloc(bufsize);
+    s->gradients  = av_calloc(bufsize, sizeof(*s->gradients));
+    s->directions = av_malloc(bufsize);
+    s->blks       = av_calloc((inlink->w / s->block_width) * (inlink->h / s->block_height),
+                              sizeof(*s->blks));
+
+    if (!s->tmpbuf || !s->filterbuf || !s->gradients || !s->directions || !s->blks)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+// edge width is defined as the distance between surrounding maxima of the edge pixel
+static float edge_width(BLRContext *blr, int i, int j, int8_t dir, int w, int h,
+                        int edge, const uint8_t *src, int src_linesize)
+{
+    float width = 0;
+    int dX, dY;
+    int sign;
+    int tmp;
+    int p1;
+    int p2;
+    int k, x, y;
+    int edge1;
+    int edge2;
+    float luma1 = 0.0; // average luma difference per edge pixel
+    float luma2 = 0.0;
+    int radius = blr->radius;
+
+    switch(dir) {
+    case DIRECTION_HORIZONTAL: dX = 1; dY =  0; break;
+    case DIRECTION_VERTICAL:   dX = 0; dY =  1; break;
+    case DIRECTION_45UP:       dX = 1; dY = -1; break;
+    case DIRECTION_45DOWN:     dX = 1; dY =  1; break;
+    }
+    if (dir == DIRECTION_HORIZONTAL) return 0;
+
+    // determines if search in direction dX/dY is looking for a maximum or minimum
+    sign = src[j * src_linesize + i] > src[(j - dY) * src_linesize + i - dX] ? 1 : -1;
+
+    // search in -(dX/dY) direction
+    for (k = 0; k < radius; k++) {
+        x = i - k*dX;
+        y = j - k*dY;
+        p1 = y * src_linesize + x;
+        x -= dX;
+        y -= dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp <= 0) // local maximum found
+            break;
+
+        luma1 += tmp;
+    }
+    if (k > 0) luma1 /= k;
+    edge1 = k;
+    width += k;
+
+    // search in +(dX/dY) direction
+    for (k = 0; k < radius; k++) {
+        x = i + k * dX;
+        y = j + k * dY;
+        p1 = y * src_linesize + x;
+        x += dX;
+        y += dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp >= 0) // local maximum found
+            break;
+
+        luma2 -= tmp;
+    }
+    if (k > 0) luma2 /= k;
+    edge2 = k;
+    width += k;
+
+    // for 45 degree directions approximate edge width in pixel units: 0.7 ~= sqrt(2)/2
+    if (dir == DIRECTION_45UP || dir == DIRECTION_45DOWN)
+        width *= 0.7;
+
+    return width;
+}
+
+static float calculate_blur(BLRContext *s, int w, int h, int hsub, int vsub,
+                            uint8_t* dir, int dir_linesize,
+                            uint8_t* dst, int dst_linesize,
+                            uint8_t* src, int src_linesize)
+{
+    float total_width = 0.0;
+    int block_count;
+    double block_total_width;
+
+    int i, j;
+    int blkcnt = 0;
+
+    float *blks = s->blks;
+    float block_pool_threshold = s->block_pct / 100.0;
+
+    int block_width  = AV_CEIL_RSHIFT(s->block_width,  hsub);
+    int block_height = AV_CEIL_RSHIFT(s->block_height, vsub);
+    int brows = h / block_height;
+    int bcols = w / block_width;
+
+    for (int blkj = 0; blkj < brows; blkj++) {
+        for (int blki = 0; blki < bcols; blki++) {
+            block_total_width = 0.0;
+            block_count = 0;
+            for (int inj = 0; inj < block_height; inj++) {
+                for (int ini = 0; ini < block_width; ini++) {
+                    i = blki * block_width + ini;
+                    j = blkj * block_height + inj;
+
+                    if (dst[j * dst_linesize + i] > 0) {
+                        float width = edge_width(s, i, j, dir[j*dir_linesize+i],
+                                                 w, h, dst[j*dst_linesize+i],
+                                                 src, src_linesize);
+                        if (width > 0.001) { // throw away zeros
+                            block_count++;
+                            block_total_width += width;
+                        }
+                    }
+                }
+            }
+            // if not enough edge pixels in a block, consider it smooth
+            if (block_total_width >= 2) {
+                blks[blkcnt] = block_total_width / block_count;
+                blkcnt++;
+            }
+        }
+    }
+
+    // simple block pooling by sorting and keeping the sharper blocks
+    AV_QSORT(blks, blkcnt, float, comp);
+    blkcnt = ceil(blkcnt * block_pool_threshold);
+    for (int i = 0; i < blkcnt; i++) {
+        total_width += blks[i];
+    }
+
+    return  total_width / blkcnt;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    av_dict_set(metadata, key, value, 0);
+}
+
+static int blurdetect_filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx  = inlink->dst;
+    BLRContext *s         = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+
+    const int inw = inlink->w;
+    const int inh = inlink->h;
+
+    uint8_t *tmpbuf     = s->tmpbuf;
+    uint8_t *filterbuf  = s->filterbuf;
+    uint16_t *gradients = s->gradients;
+    int8_t *directions  = s->directions;
+
+    float blur = 0.0f;
+    int nplanes = 0;
+    AVDictionary **metadata;
+    metadata = &in->metadata;
+
+    for (int plane = 0; plane < s->nb_planes; plane++) {
+        int hsub = plane == 1 || plane == 2 ? s->hsub : 0;
+        int vsub = plane == 1 || plane == 2 ? s->vsub : 0;
+        int w = AV_CEIL_RSHIFT(inw, hsub);
+        int h = AV_CEIL_RSHIFT(inh, vsub);
+
+        if (!((1 << plane) & s->planes))
+            continue;
+
+        nplanes++;
+
+        // gaussian filter to reduce noise
+        ff_gaussian_blur(w, h,
+                         filterbuf,  w,
+                         in->data[plane], in->linesize[plane]);
+
+        // compute the 16-bits gradients and directions for the next step
+        ff_sobel(w, h, gradients, w, directions, w, filterbuf, w);
+
+        // non_maximum_suppression() will actually keep & clip what's necessary and
+        // ignore the rest, so we need a clean output buffer
+        memset(tmpbuf, 0, inw * inh);
+        ff_non_maximum_suppression(w, h, tmpbuf, w, directions, w, gradients, w);
+
+
+        // keep high values, or low values surrounded by high values
+        ff_double_threshold(s->low_u8, s->high_u8, w, h,
+                            tmpbuf, w, tmpbuf, w);
+
+        blur += calculate_blur(s, w, h, hsub, vsub, directions, w,
+                              tmpbuf, w, filterbuf, w);
+    }
+
+    if (nplanes)
+        blur /= nplanes;
+
+    s->blur_total += blur;
+
+    // write stats
+    av_log(ctx, AV_LOG_VERBOSE, "blur: %.7f\n", blur);
+
+    set_meta(metadata, "lavfi.blur", blur);
+
+    s->nb_frames = inlink->frame_count_in;
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void blurdetect_uninit(AVFilterContext *ctx)
+{
+    BLRContext *s = ctx->priv;
+
+    if (s->nb_frames > 0) {
+        av_log(ctx, AV_LOG_INFO, "blur mean: %.7f\n",
+               s->blur_total / s->nb_frames);
+    }
+
+    av_freep(&s->tmpbuf);
+    av_freep(&s->filterbuf);
+    av_freep(&s->gradients);
+    av_freep(&s->directions);
+    av_freep(&s->blks);
+}
+
+static const enum AVPixelFormat pix_fmts[] = {
+    AV_PIX_FMT_GRAY8,
+    AV_PIX_FMT_GBRP,     AV_PIX_FMT_GBRAP,
+    AV_PIX_FMT_YUV422P,  AV_PIX_FMT_YUV420P,
+    AV_PIX_FMT_YUV444P,  AV_PIX_FMT_YUV440P,
+    AV_PIX_FMT_YUV411P,  AV_PIX_FMT_YUV410P,
+    AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUVJ420P,
+    AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ444P,
+    AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
+    AV_PIX_FMT_NONE };
+
+static const AVFilterPad blurdetect_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = blurdetect_config_input,
+        .filter_frame = blurdetect_filter_frame,
+    },
+};
+
+static const AVFilterPad blurdetect_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+const AVFilter ff_vf_blurdetect = {
+    .name          = "blurdetect",
+    .description   = NULL_IF_CONFIG_SMALL("Blurdetect filter."),
+    .priv_size     = sizeof(BLRContext),
+    .init          = blurdetect_init,
+    .uninit        = blurdetect_uninit,
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    FILTER_INPUTS(blurdetect_inputs),
+    FILTER_OUTPUTS(blurdetect_outputs),
+    .priv_class    = &blurdetect_class,
+    .flags         = AVFILTER_FLAG_METADATA_ONLY,
+};
+
Thilo Borgmann April 24, 2022, 5:28 p.m. UTC | #8
Am 23.04.22 um 15:32 schrieb Thilo Borgmann:
> Hi,
> 
>>>>> v3 updated to current HEAD.
>>>>>
>>>>> Named blurdetect filter now.
>>>>> Minor fixes on allocation and removed -f option.
>>>>>
>>>>
>>>> Please make this per plane filtering, with default to measure only first
>>>> plane.
>>>
>>> done in v4.
>>>
>>> (Will add Changelog, version.h and fate test once the filter itself looks ok)
>>
>> Ping.
> 
> v5 according to IRC comments.

v6 (1/2 and 2/2) according to IRC comments. LGTM'd there, applying soon.

Added Changelog, version.h, FATE.

Thanks!
Thilo
From c90120255bff305ce76c7677c9063d94c3bb99f7 Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Tue, 30 Nov 2021 00:16:52 +0100
Subject: [PATCH v6 1/2] lafi/vf_edgedetect: Move some common functions into
 seperate file

---
 libavfilter/Makefile        |   2 +-
 libavfilter/edge_common.c   | 181 +++++++++++++++++++++++++++++++++++
 libavfilter/edge_common.h   | 107 +++++++++++++++++++++
 libavfilter/vf_edgedetect.c | 183 ++----------------------------------
 4 files changed, 296 insertions(+), 177 deletions(-)
 create mode 100644 libavfilter/edge_common.c
 create mode 100644 libavfilter/edge_common.h

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 32521a4836..38ca379e5a 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -266,7 +266,7 @@ OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o
 OBJS-$(CONFIG_DRAWGRAPH_FILTER)              += f_drawgraph.o
 OBJS-$(CONFIG_DRAWGRID_FILTER)               += vf_drawbox.o
 OBJS-$(CONFIG_DRAWTEXT_FILTER)               += vf_drawtext.o
-OBJS-$(CONFIG_EDGEDETECT_FILTER)             += vf_edgedetect.o
+OBJS-$(CONFIG_EDGEDETECT_FILTER)             += vf_edgedetect.o edge_common.o
 OBJS-$(CONFIG_ELBG_FILTER)                   += vf_elbg.o
 OBJS-$(CONFIG_ENTROPY_FILTER)                += vf_entropy.o
 OBJS-$(CONFIG_EPX_FILTER)                    += vf_epx.o
diff --git a/libavfilter/edge_common.c b/libavfilter/edge_common.c
new file mode 100644
index 0000000000..d72e8521cd
--- /dev/null
+++ b/libavfilter/edge_common.c
@@ -0,0 +1,181 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "edge_common.h"
+
+// Internal helper for ff_sobel()
+static int get_rounded_direction(int gx, int gy)
+{
+    /* reference angles:
+     *   tan( pi/8) = sqrt(2)-1
+     *   tan(3pi/8) = sqrt(2)+1
+     * Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
+     * <ref-angle>, or more simply Gy against <ref-angle>*Gx
+     *
+     * Gx and Gy bounds = [-1020;1020], using 16-bit arithmetic:
+     *   round((sqrt(2)-1) * (1<<16)) =  27146
+     *   round((sqrt(2)+1) * (1<<16)) = 158218
+     */
+    if (gx) {
+        int tanpi8gx, tan3pi8gx;
+
+        if (gx < 0)
+            gx = -gx, gy = -gy;
+        gy *= (1 << 16);
+        tanpi8gx  =  27146 * gx;
+        tan3pi8gx = 158218 * gx;
+        if (gy > -tan3pi8gx && gy < -tanpi8gx)  return DIRECTION_45UP;
+        if (gy > -tanpi8gx  && gy <  tanpi8gx)  return DIRECTION_HORIZONTAL;
+        if (gy >  tanpi8gx  && gy <  tan3pi8gx) return DIRECTION_45DOWN;
+    }
+    return DIRECTION_VERTICAL;
+}
+
+// Simple sobel operator to get rounded gradients
+void ff_sobel(int w, int h,
+                    uint16_t *dst, int dst_linesize,
+                    int8_t *dir, int dir_linesize,
+                    const uint8_t *src, int src_linesize)
+{
+    int i, j;
+
+    for (j = 1; j < h - 1; j++) {
+        dst += dst_linesize;
+        dir += dir_linesize;
+        src += src_linesize;
+        for (i = 1; i < w - 1; i++) {
+            const int gx =
+                -1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1]
+                -2*src[                i-1] + 2*src[                i+1]
+                -1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1];
+            const int gy =
+                -1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1]
+                -2*src[-src_linesize + i  ] + 2*src[ src_linesize + i  ]
+                -1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1];
+
+            dst[i] = FFABS(gx) + FFABS(gy);
+            dir[i] = get_rounded_direction(gx, gy);
+        }
+    }
+}
+
+// Filters rounded gradients to drop all non-maxima
+// Expects gradients generated by ff_sobel()
+// Expects zero's destination buffer
+void ff_non_maximum_suppression(int w, int h,
+                                      uint8_t *dst, int dst_linesize,
+                                      const int8_t *dir, int dir_linesize,
+                                      const uint16_t *src, int src_linesize)
+{
+    int i, j;
+
+#define COPY_MAXIMA(ay, ax, by, bx) do {                \
+    if (src[i] > src[(ay)*src_linesize + i+(ax)] &&     \
+        src[i] > src[(by)*src_linesize + i+(bx)])       \
+        dst[i] = av_clip_uint8(src[i]);                 \
+} while (0)
+
+    for (j = 1; j < h - 1; j++) {
+        dst += dst_linesize;
+        dir += dir_linesize;
+        src += src_linesize;
+        for (i = 1; i < w - 1; i++) {
+            switch (dir[i]) {
+            case DIRECTION_45UP:        COPY_MAXIMA( 1, -1, -1,  1); break;
+            case DIRECTION_45DOWN:      COPY_MAXIMA(-1, -1,  1,  1); break;
+            case DIRECTION_HORIZONTAL:  COPY_MAXIMA( 0, -1,  0,  1); break;
+            case DIRECTION_VERTICAL:    COPY_MAXIMA(-1,  0,  1,  0); break;
+            }
+        }
+    }
+}
+
+// Filter to keep all pixels > high, and keep all pixels > low where all surrounding pixels > high
+void ff_double_threshold(int low, int high, int w, int h,
+                               uint8_t *dst, int dst_linesize,
+                               const uint8_t *src, int src_linesize)
+{
+    int i, j;
+
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+            if (src[i] > high) {
+                dst[i] = src[i];
+                continue;
+            }
+
+            if (!(!i || i == w - 1 || !j || j == h - 1) &&
+                src[i] > low &&
+                (src[-src_linesize + i-1] > high ||
+                 src[-src_linesize + i  ] > high ||
+                 src[-src_linesize + i+1] > high ||
+                 src[                i-1] > high ||
+                 src[                i+1] > high ||
+                 src[ src_linesize + i-1] > high ||
+                 src[ src_linesize + i  ] > high ||
+                 src[ src_linesize + i+1] > high))
+                dst[i] = src[i];
+            else
+                dst[i] = 0;
+        }
+        dst += dst_linesize;
+        src += src_linesize;
+    }
+}
+
+// Applies gaussian blur, using 5x5 kernels, sigma = 1.4
+void ff_gaussian_blur(int w, int h,
+                      uint8_t *dst, int dst_linesize,
+                      const uint8_t *src, int src_linesize)
+{
+    int i, j;
+
+    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
+    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
+    for (j = 2; j < h - 2; j++) {
+        dst[0] = src[0];
+        dst[1] = src[1];
+        for (i = 2; i < w - 2; i++) {
+            /* Gaussian mask of size 5x5 with sigma = 1.4 */
+            dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2
+                    + (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4
+                    + (src[-2*src_linesize + i  ] + src[2*src_linesize + i  ]) * 5
+                    + (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4
+                    + (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2
+
+                    + (src[  -src_linesize + i-2] + src[  src_linesize + i-2]) *  4
+                    + (src[  -src_linesize + i-1] + src[  src_linesize + i-1]) *  9
+                    + (src[  -src_linesize + i  ] + src[  src_linesize + i  ]) * 12
+                    + (src[  -src_linesize + i+1] + src[  src_linesize + i+1]) *  9
+                    + (src[  -src_linesize + i+2] + src[  src_linesize + i+2]) *  4
+
+                    + src[i-2] *  5
+                    + src[i-1] * 12
+                    + src[i  ] * 15
+                    + src[i+1] * 12
+                    + src[i+2] *  5) / 159;
+        }
+        dst[i    ] = src[i    ];
+        dst[i + 1] = src[i + 1];
+
+        dst += dst_linesize;
+        src += src_linesize;
+    }
+    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
+    memcpy(dst, src, w);
+}
diff --git a/libavfilter/edge_common.h b/libavfilter/edge_common.h
new file mode 100644
index 0000000000..87c143f2b8
--- /dev/null
+++ b/libavfilter/edge_common.h
@@ -0,0 +1,107 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * common functions for edge detection
+ */
+
+#ifndef AVFILTER_EDGE_COMMON_H
+#define AVFILTER_EDGE_COMMON_H
+
+#include "avfilter.h"
+
+/**
+ * @brief Rounded directions used in av_image_sobel()
+ */
+enum AVRoundedDirection {
+    DIRECTION_45UP,
+    DIRECTION_45DOWN,
+    DIRECTION_HORIZONTAL,
+    DIRECTION_VERTICAL,
+};
+
+/**
+ * Simple sobel operator to get rounded gradients
+ *
+ * @param w             the width of the image in pixels
+ * @param h             the height of the image in pixels
+ * @param dst           data pointers to magnitude image
+ * @param dst_linesize  linesizes for the magnitude image
+ * @param dir           data pointers to direction image
+ * @param dir_linesize  linesizes for the direction image
+ * @param src           data pointers to source image
+ * @param src_linesize  linesizes for the source image
+ */
+void ff_sobel(int w, int h,
+              uint16_t *dst, int dst_linesize,
+              int8_t *dir, int dir_linesize,
+              const uint8_t *src, int src_linesize);
+
+/**
+ * Filters rounded gradients to drop all non-maxima pixels in the magnitude image
+ * Expects gradients generated by av_image_sobel()
+ * Expects zero's in the destination buffer dst
+ *
+ * @param w             the width of the image in pixels
+ * @param h             the height of the image in pixels
+ * @param dst           data pointers to magnitude image
+ * @param dst_linesize  linesizes for the magnitude image
+ * @param dir           data pointers to direction image
+ * @param dir_linesize  linesizes for the direction image
+ * @param src           data pointers to source image
+ * @param src_linesize  linesizes for the source image
+ */
+void ff_non_maximum_suppression(int w, int h,
+                                uint8_t *dst, int dst_linesize,
+                                const int8_t *dir, int dir_linesize,
+                                const uint16_t *src, int src_linesize);
+
+/**
+ * Filters all pixels in src to keep all pixels > high,
+ * and keep all pixels > low where all surrounding pixels > high
+ *
+ * @param low           the low threshold value
+ * @param high          the hegh threshold value
+ * @param w             the width of the image in pixels
+ * @param h             the height of the image in pixels
+ * @param dst           data pointers to destination image
+ * @param dst_linesize  linesizes for the destination image
+ * @param src           data pointers to source image
+ * @param src_linesize  linesizes for the source image
+ */
+void ff_double_threshold(int low, int high, int w, int h,
+                         uint8_t *dst, int dst_linesize,
+                         const uint8_t *src, int src_linesize);
+
+/**
+ * Applies gaussian blur.
+ * 5x5 kernels, sigma = 1.4
+ *
+ * @param w             the width of the image in pixels
+ * @param h             the height of the image in pixels
+ * @param dst           data pointers to destination image
+ * @param dst_linesize  linesizes for the destination image
+ * @param src           data pointers to source image
+ * @param src_linesize  linesizes for the source image
+ */
+void ff_gaussian_blur(int w, int h,
+                      uint8_t *dst, int dst_linesize,
+                      const uint8_t *src, int src_linesize);
+
+#endif
diff --git a/libavfilter/vf_edgedetect.c b/libavfilter/vf_edgedetect.c
index 3eea34e325..90390ceb3e 100644
--- a/libavfilter/vf_edgedetect.c
+++ b/libavfilter/vf_edgedetect.c
@@ -32,6 +32,7 @@
 #include "formats.h"
 #include "internal.h"
 #include "video.h"
+#include "edge_common.h"
 
 #define PLANE_R 0x4
 #define PLANE_G 0x1
@@ -139,176 +140,6 @@ static int config_props(AVFilterLink *inlink)
     return 0;
 }
 
-static void gaussian_blur(AVFilterContext *ctx, int w, int h,
-                                uint8_t *dst, int dst_linesize,
-                          const uint8_t *src, int src_linesize)
-{
-    int i, j;
-
-    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
-    if (h > 1) {
-        memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
-    }
-    for (j = 2; j < h - 2; j++) {
-        dst[0] = src[0];
-        if (w > 1)
-            dst[1] = src[1];
-        for (i = 2; i < w - 2; i++) {
-            /* Gaussian mask of size 5x5 with sigma = 1.4 */
-            dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2
-                    + (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4
-                    + (src[-2*src_linesize + i  ] + src[2*src_linesize + i  ]) * 5
-                    + (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4
-                    + (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2
-
-                    + (src[  -src_linesize + i-2] + src[  src_linesize + i-2]) *  4
-                    + (src[  -src_linesize + i-1] + src[  src_linesize + i-1]) *  9
-                    + (src[  -src_linesize + i  ] + src[  src_linesize + i  ]) * 12
-                    + (src[  -src_linesize + i+1] + src[  src_linesize + i+1]) *  9
-                    + (src[  -src_linesize + i+2] + src[  src_linesize + i+2]) *  4
-
-                    + src[i-2] *  5
-                    + src[i-1] * 12
-                    + src[i  ] * 15
-                    + src[i+1] * 12
-                    + src[i+2] *  5) / 159;
-        }
-        if (w > 2)
-            dst[i    ] = src[i    ];
-        if (w > 3)
-            dst[i + 1] = src[i + 1];
-
-        dst += dst_linesize;
-        src += src_linesize;
-    }
-    if (h > 2) {
-        memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
-    }
-    if (h > 3)
-        memcpy(dst, src, w);
-}
-
-enum {
-    DIRECTION_45UP,
-    DIRECTION_45DOWN,
-    DIRECTION_HORIZONTAL,
-    DIRECTION_VERTICAL,
-};
-
-static int get_rounded_direction(int gx, int gy)
-{
-    /* reference angles:
-     *   tan( pi/8) = sqrt(2)-1
-     *   tan(3pi/8) = sqrt(2)+1
-     * Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
-     * <ref-angle>, or more simply Gy against <ref-angle>*Gx
-     *
-     * Gx and Gy bounds = [-1020;1020], using 16-bit arithmetic:
-     *   round((sqrt(2)-1) * (1<<16)) =  27146
-     *   round((sqrt(2)+1) * (1<<16)) = 158218
-     */
-    if (gx) {
-        int tanpi8gx, tan3pi8gx;
-
-        if (gx < 0)
-            gx = -gx, gy = -gy;
-        gy *= (1 << 16);
-        tanpi8gx  =  27146 * gx;
-        tan3pi8gx = 158218 * gx;
-        if (gy > -tan3pi8gx && gy < -tanpi8gx)  return DIRECTION_45UP;
-        if (gy > -tanpi8gx  && gy <  tanpi8gx)  return DIRECTION_HORIZONTAL;
-        if (gy >  tanpi8gx  && gy <  tan3pi8gx) return DIRECTION_45DOWN;
-    }
-    return DIRECTION_VERTICAL;
-}
-
-static void sobel(int w, int h,
-                       uint16_t *dst, int dst_linesize,
-                         int8_t *dir, int dir_linesize,
-                  const uint8_t *src, int src_linesize)
-{
-    int i, j;
-
-    for (j = 1; j < h - 1; j++) {
-        dst += dst_linesize;
-        dir += dir_linesize;
-        src += src_linesize;
-        for (i = 1; i < w - 1; i++) {
-            const int gx =
-                -1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1]
-                -2*src[                i-1] + 2*src[                i+1]
-                -1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1];
-            const int gy =
-                -1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1]
-                -2*src[-src_linesize + i  ] + 2*src[ src_linesize + i  ]
-                -1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1];
-
-            dst[i] = FFABS(gx) + FFABS(gy);
-            dir[i] = get_rounded_direction(gx, gy);
-        }
-    }
-}
-
-static void non_maximum_suppression(int w, int h,
-                                          uint8_t  *dst, int dst_linesize,
-                                    const  int8_t  *dir, int dir_linesize,
-                                    const uint16_t *src, int src_linesize)
-{
-    int i, j;
-
-#define COPY_MAXIMA(ay, ax, by, bx) do {                \
-    if (src[i] > src[(ay)*src_linesize + i+(ax)] &&     \
-        src[i] > src[(by)*src_linesize + i+(bx)])       \
-        dst[i] = av_clip_uint8(src[i]);                 \
-} while (0)
-
-    for (j = 1; j < h - 1; j++) {
-        dst += dst_linesize;
-        dir += dir_linesize;
-        src += src_linesize;
-        for (i = 1; i < w - 1; i++) {
-            switch (dir[i]) {
-            case DIRECTION_45UP:        COPY_MAXIMA( 1, -1, -1,  1); break;
-            case DIRECTION_45DOWN:      COPY_MAXIMA(-1, -1,  1,  1); break;
-            case DIRECTION_HORIZONTAL:  COPY_MAXIMA( 0, -1,  0,  1); break;
-            case DIRECTION_VERTICAL:    COPY_MAXIMA(-1,  0,  1,  0); break;
-            }
-        }
-    }
-}
-
-static void double_threshold(int low, int high, int w, int h,
-                                   uint8_t *dst, int dst_linesize,
-                             const uint8_t *src, int src_linesize)
-{
-    int i, j;
-
-    for (j = 0; j < h; j++) {
-        for (i = 0; i < w; i++) {
-            if (src[i] > high) {
-                dst[i] = src[i];
-                continue;
-            }
-
-            if (!(!i || i == w - 1 || !j || j == h - 1) &&
-                src[i] > low &&
-                (src[-src_linesize + i-1] > high ||
-                 src[-src_linesize + i  ] > high ||
-                 src[-src_linesize + i+1] > high ||
-                 src[                i-1] > high ||
-                 src[                i+1] > high ||
-                 src[ src_linesize + i-1] > high ||
-                 src[ src_linesize + i  ] > high ||
-                 src[ src_linesize + i+1] > high))
-                dst[i] = src[i];
-            else
-                dst[i] = 0;
-        }
-        dst += dst_linesize;
-        src += src_linesize;
-    }
-}
-
 static void color_mix(int w, int h,
                             uint8_t *dst, int dst_linesize,
                       const uint8_t *src, int src_linesize)
@@ -360,12 +191,12 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
         }
 
         /* gaussian filter to reduce noise  */
-        gaussian_blur(ctx, width, height,
-                      tmpbuf,      width,
-                      in->data[p], in->linesize[p]);
+        ff_gaussian_blur(width, height,
+                         tmpbuf,      width,
+                         in->data[p], in->linesize[p]);
 
         /* compute the 16-bits gradients and directions for the next step */
-        sobel(width, height,
+        ff_sobel(width, height,
               gradients, width,
               directions,width,
               tmpbuf,    width);
@@ -373,13 +204,13 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
         /* non_maximum_suppression() will actually keep & clip what's necessary and
          * ignore the rest, so we need a clean output buffer */
         memset(tmpbuf, 0, width * height);
-        non_maximum_suppression(width, height,
+        ff_non_maximum_suppression(width, height,
                                 tmpbuf,    width,
                                 directions,width,
                                 gradients, width);
 
         /* keep high values, or low values surrounded by high values */
-        double_threshold(edgedetect->low_u8, edgedetect->high_u8,
+        ff_double_threshold(edgedetect->low_u8, edgedetect->high_u8,
                          width, height,
                          out->data[p], out->linesize[p],
                          tmpbuf,       width);
Thilo Borgmann April 24, 2022, 10:03 p.m. UTC | #9
Am 24.04.22 um 19:28 schrieb Thilo Borgmann:
> Am 23.04.22 um 15:32 schrieb Thilo Borgmann:
>> Hi,
>>
>>>>>> v3 updated to current HEAD.
>>>>>>
>>>>>> Named blurdetect filter now.
>>>>>> Minor fixes on allocation and removed -f option.
>>>>>>
>>>>>
>>>>> Please make this per plane filtering, with default to measure only first
>>>>> plane.
>>>>
>>>> done in v4.
>>>>
>>>> (Will add Changelog, version.h and fate test once the filter itself looks ok)
>>>
>>> Ping.
>>
>> v5 according to IRC comments.
> 
> v6 (1/2 and 2/2) according to IRC comments. LGTM'd there, applying soon.
> 
> Added Changelog, version.h, FATE.

v7: removed useless debug garbage. Still applying soon.

-Thilo
From 2879cfd94358aa977dd7f4314f931fb782750f96 Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Mon, 25 Apr 2022 00:01:51 +0200
Subject: [PATCH v7 2/2] lavfi: Add blurdetect filter

---
 Changelog                                   |   1 +
 doc/filters.texi                            |  52 +++
 libavfilter/Makefile                        |   1 +
 libavfilter/allfilters.c                    |   1 +
 libavfilter/version.h                       |   2 +-
 libavfilter/vf_blurdetect.c                 | 395 ++++++++++++++++++++
 tests/fate/filter-video.mak                 |   3 +
 tests/ref/fate/filter-refcmp-blurdetect-yuv |  10 +
 8 files changed, 464 insertions(+), 1 deletion(-)
 create mode 100644 libavfilter/vf_blurdetect.c
 create mode 100644 tests/ref/fate/filter-refcmp-blurdetect-yuv

diff --git a/Changelog b/Changelog
index 7a63e3d1ee..4d467eb741 100644
--- a/Changelog
+++ b/Changelog
@@ -13,6 +13,7 @@ version 5.1:
 - pixelize video filter
 - colormap video filter
 - colorchart video source filter
+- blurdetect filter
 
 
 version 5.0:
diff --git a/doc/filters.texi b/doc/filters.texi
index c8699b9099..499f3adcd9 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -7997,6 +7997,58 @@ tblend=all_mode=grainextract
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@anchor{blurdetect}
+@section blurdetect
+
+Determines blurriness of frames without altering the input frames.
+
+Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric."
+Allows for a block-based abbreviation.
+
+The filter accepts the following options:
+
+@table @option
+@item low
+@item high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be chosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+
+@item radius
+Define the radius to search around an edge pixel for local maxima.
+
+@item block_pct
+Determine blurriness only for the most significant blocks, given in percentage.
+
+@item block_width
+Determine blurriness for blocks of width @var{block_width}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_height}.
+
+@item block_height
+Determine blurriness for blocks of height @var{block_height}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_width}.
+
+@item planes
+Set planes to filter. Default is first only.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Determine blur for 80% of most significant 32x32 blocks:
+@example
+blurdetect=block_width=32:block_height=32:block_pct=80
+@end example
+@end itemize
+
 @section bm3d
 
 Denoise frames using Block-Matching 3D algorithm.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 38ca379e5a..1db097b464 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -195,6 +195,7 @@ OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o framesync.o
 OBJS-$(CONFIG_BLEND_VULKAN_FILTER)           += vf_blend_vulkan.o framesync.o vulkan.o vulkan_filter.o
+OBJS-$(CONFIG_BLURDETECT_FILTER)             += vf_blurdetect.o edge_common.o
 OBJS-$(CONFIG_BM3D_FILTER)                   += vf_bm3d.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o boxblur.o
 OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 36fa3ae8d7..2ad523fd0f 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -183,6 +183,7 @@ extern const AVFilter ff_vf_blackdetect;
 extern const AVFilter ff_vf_blackframe;
 extern const AVFilter ff_vf_blend;
 extern const AVFilter ff_vf_blend_vulkan;
+extern const AVFilter ff_vf_blurdetect;
 extern const AVFilter ff_vf_bm3d;
 extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
diff --git a/libavfilter/version.h b/libavfilter/version.h
index 9add1658e5..8f1b16969a 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFILTER_VERSION_MINOR  36
+#define LIBAVFILTER_VERSION_MINOR  37
 #define LIBAVFILTER_VERSION_MICRO 100
 
 
diff --git a/libavfilter/vf_blurdetect.c b/libavfilter/vf_blurdetect.c
new file mode 100644
index 0000000000..7c0f5ce68a
--- /dev/null
+++ b/libavfilter/vf_blurdetect.c
@@ -0,0 +1,395 @@
+/*
+ * Copyright (c) 2021 Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * No-reference blurdetect filter
+ *
+ * Implementing:
+ * Marziliano, Pina, et al. "A no-reference perceptual blur metric." Proceedings.
+ * International conference on image processing. Vol. 3. IEEE, 2002.
+ * https://infoscience.epfl.ch/record/111802/files/14%20A%20no-reference%20perceptual%20blur%20metric.pdf
+ *
+ * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixelutils.h"
+#include "libavutil/motion_vector.h"
+#include "libavutil/qsort.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "edge_common.h"
+
+static int comp(const float *a,const float *b)
+{
+    return FFDIFFSIGN(*a, *b);
+}
+
+typedef struct BLRContext {
+    const AVClass *class;
+
+    int hsub, vsub;
+    int nb_planes;
+
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    int     radius;        // radius during local maxima detection
+    int     block_pct;     // percentage of "sharpest" blocks in the image to use for bluriness calculation
+    int     block_width;   // width for block abbreviation
+    int     block_height;  // height for block abbreviation
+    int     planes;        // number of planes to filter
+
+    double   blur_total;
+    uint64_t nb_frames;
+
+    float    *blks;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+} BLRContext;
+
+#define OFFSET(x) offsetof(BLRContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption blurdetect_options[] = {
+    { "high",          "set high threshold", OFFSET(high), AV_OPT_TYPE_FLOAT, {.dbl=30/255.}, 0, 1, FLAGS },
+    { "low",           "set low threshold",  OFFSET(low),  AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "radius",        "search radius for maxima detection", OFFSET(radius), AV_OPT_TYPE_INT, {.i64=50}, 1, 100, FLAGS },
+    { "block_pct",     "block pooling threshold when calculating blurriness", OFFSET(block_pct), AV_OPT_TYPE_INT, {.i64=80}, 1, 100, FLAGS },
+    { "block_width",   "block size for block-based abbreviation of blurriness", OFFSET(block_width), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "block_height",  "block size for block-based abbreviation of blurriness", OFFSET(block_height), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "planes",        "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT, {.i64=1}, 0, 15, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blurdetect);
+
+static av_cold int blurdetect_init(AVFilterContext *ctx)
+{
+    BLRContext *s = ctx->priv;
+
+    s->low_u8  = s->low  * 255. + .5;
+    s->high_u8 = s->high * 255. + .5;
+
+    return 0;
+}
+
+static int blurdetect_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BLRContext      *s   = ctx->priv;
+    const int bufsize    = inlink->w * inlink->h;
+    const AVPixFmtDescriptor *pix_desc;
+
+    pix_desc = av_pix_fmt_desc_get(inlink->format);
+    s->hsub = pix_desc->log2_chroma_w;
+    s->vsub = pix_desc->log2_chroma_h;
+    s->nb_planes = av_pix_fmt_count_planes(inlink->format);
+
+    if (s->block_width  < 1 || s->block_height < 1) {
+        s->block_width  = inlink->w;
+        s->block_height = inlink->h;
+    }
+
+    s->tmpbuf     = av_malloc(bufsize);
+    s->filterbuf  = av_malloc(bufsize);
+    s->gradients  = av_calloc(bufsize, sizeof(*s->gradients));
+    s->directions = av_malloc(bufsize);
+    s->blks       = av_calloc((inlink->w / s->block_width) * (inlink->h / s->block_height),
+                              sizeof(*s->blks));
+
+    if (!s->tmpbuf || !s->filterbuf || !s->gradients || !s->directions || !s->blks)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+// edge width is defined as the distance between surrounding maxima of the edge pixel
+static float edge_width(BLRContext *blr, int i, int j, int8_t dir, int w, int h,
+                        int edge, const uint8_t *src, int src_linesize)
+{
+    float width = 0;
+    int dX, dY;
+    int sign;
+    int tmp;
+    int p1;
+    int p2;
+    int k, x, y;
+    int edge1;
+    int edge2;
+    float luma1 = 0.0; // average luma difference per edge pixel
+    float luma2 = 0.0;
+    int radius = blr->radius;
+
+    switch(dir) {
+    case DIRECTION_HORIZONTAL: dX = 1; dY =  0; break;
+    case DIRECTION_VERTICAL:   dX = 0; dY =  1; break;
+    case DIRECTION_45UP:       dX = 1; dY = -1; break;
+    case DIRECTION_45DOWN:     dX = 1; dY =  1; break;
+    }
+
+    // determines if search in direction dX/dY is looking for a maximum or minimum
+    sign = src[j * src_linesize + i] > src[(j - dY) * src_linesize + i - dX] ? 1 : -1;
+
+    // search in -(dX/dY) direction
+    for (k = 0; k < radius; k++) {
+        x = i - k*dX;
+        y = j - k*dY;
+        p1 = y * src_linesize + x;
+        x -= dX;
+        y -= dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp <= 0) // local maximum found
+            break;
+
+        luma1 += tmp;
+    }
+    if (k > 0) luma1 /= k;
+    edge1 = k;
+    width += k;
+
+    // search in +(dX/dY) direction
+    for (k = 0; k < radius; k++) {
+        x = i + k * dX;
+        y = j + k * dY;
+        p1 = y * src_linesize + x;
+        x += dX;
+        y += dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp >= 0) // local maximum found
+            break;
+
+        luma2 -= tmp;
+    }
+    if (k > 0) luma2 /= k;
+    edge2 = k;
+    width += k;
+
+    // for 45 degree directions approximate edge width in pixel units: 0.7 ~= sqrt(2)/2
+    if (dir == DIRECTION_45UP || dir == DIRECTION_45DOWN)
+        width *= 0.7;
+
+    return width;
+}
+
+static float calculate_blur(BLRContext *s, int w, int h, int hsub, int vsub,
+                            uint8_t* dir, int dir_linesize,
+                            uint8_t* dst, int dst_linesize,
+                            uint8_t* src, int src_linesize)
+{
+    float total_width = 0.0;
+    int block_count;
+    double block_total_width;
+
+    int i, j;
+    int blkcnt = 0;
+
+    float *blks = s->blks;
+    float block_pool_threshold = s->block_pct / 100.0;
+
+    int block_width  = AV_CEIL_RSHIFT(s->block_width,  hsub);
+    int block_height = AV_CEIL_RSHIFT(s->block_height, vsub);
+    int brows = h / block_height;
+    int bcols = w / block_width;
+
+    for (int blkj = 0; blkj < brows; blkj++) {
+        for (int blki = 0; blki < bcols; blki++) {
+            block_total_width = 0.0;
+            block_count = 0;
+            for (int inj = 0; inj < block_height; inj++) {
+                for (int ini = 0; ini < block_width; ini++) {
+                    i = blki * block_width + ini;
+                    j = blkj * block_height + inj;
+
+                    if (dst[j * dst_linesize + i] > 0) {
+                        float width = edge_width(s, i, j, dir[j*dir_linesize+i],
+                                                 w, h, dst[j*dst_linesize+i],
+                                                 src, src_linesize);
+                        if (width > 0.001) { // throw away zeros
+                            block_count++;
+                            block_total_width += width;
+                        }
+                    }
+                }
+            }
+            // if not enough edge pixels in a block, consider it smooth
+            if (block_total_width >= 2) {
+                blks[blkcnt] = block_total_width / block_count;
+                blkcnt++;
+            }
+        }
+    }
+
+    // simple block pooling by sorting and keeping the sharper blocks
+    AV_QSORT(blks, blkcnt, float, comp);
+    blkcnt = ceil(blkcnt * block_pool_threshold);
+    for (int i = 0; i < blkcnt; i++) {
+        total_width += blks[i];
+    }
+
+    return  total_width / blkcnt;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    av_dict_set(metadata, key, value, 0);
+}
+
+static int blurdetect_filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx  = inlink->dst;
+    BLRContext *s         = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+
+    const int inw = inlink->w;
+    const int inh = inlink->h;
+
+    uint8_t *tmpbuf     = s->tmpbuf;
+    uint8_t *filterbuf  = s->filterbuf;
+    uint16_t *gradients = s->gradients;
+    int8_t *directions  = s->directions;
+
+    float blur = 0.0f;
+    int nplanes = 0;
+    AVDictionary **metadata;
+    metadata = &in->metadata;
+
+    for (int plane = 0; plane < s->nb_planes; plane++) {
+        int hsub = plane == 1 || plane == 2 ? s->hsub : 0;
+        int vsub = plane == 1 || plane == 2 ? s->vsub : 0;
+        int w = AV_CEIL_RSHIFT(inw, hsub);
+        int h = AV_CEIL_RSHIFT(inh, vsub);
+
+        if (!((1 << plane) & s->planes))
+            continue;
+
+        nplanes++;
+
+        // gaussian filter to reduce noise
+        ff_gaussian_blur(w, h,
+                         filterbuf,  w,
+                         in->data[plane], in->linesize[plane]);
+
+        // compute the 16-bits gradients and directions for the next step
+        ff_sobel(w, h, gradients, w, directions, w, filterbuf, w);
+
+        // non_maximum_suppression() will actually keep & clip what's necessary and
+        // ignore the rest, so we need a clean output buffer
+        memset(tmpbuf, 0, inw * inh);
+        ff_non_maximum_suppression(w, h, tmpbuf, w, directions, w, gradients, w);
+
+
+        // keep high values, or low values surrounded by high values
+        ff_double_threshold(s->low_u8, s->high_u8, w, h,
+                            tmpbuf, w, tmpbuf, w);
+
+        blur += calculate_blur(s, w, h, hsub, vsub, directions, w,
+                              tmpbuf, w, filterbuf, w);
+    }
+
+    if (nplanes)
+        blur /= nplanes;
+
+    s->blur_total += blur;
+
+    // write stats
+    av_log(ctx, AV_LOG_VERBOSE, "blur: %.7f\n", blur);
+
+    set_meta(metadata, "lavfi.blur", blur);
+
+    s->nb_frames = inlink->frame_count_in;
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void blurdetect_uninit(AVFilterContext *ctx)
+{
+    BLRContext *s = ctx->priv;
+
+    if (s->nb_frames > 0) {
+        av_log(ctx, AV_LOG_INFO, "blur mean: %.7f\n",
+               s->blur_total / s->nb_frames);
+    }
+
+    av_freep(&s->tmpbuf);
+    av_freep(&s->filterbuf);
+    av_freep(&s->gradients);
+    av_freep(&s->directions);
+    av_freep(&s->blks);
+}
+
+static const enum AVPixelFormat pix_fmts[] = {
+    AV_PIX_FMT_GRAY8,
+    AV_PIX_FMT_GBRP,     AV_PIX_FMT_GBRAP,
+    AV_PIX_FMT_YUV422P,  AV_PIX_FMT_YUV420P,
+    AV_PIX_FMT_YUV444P,  AV_PIX_FMT_YUV440P,
+    AV_PIX_FMT_YUV411P,  AV_PIX_FMT_YUV410P,
+    AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUVJ420P,
+    AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ444P,
+    AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
+    AV_PIX_FMT_NONE
+};
+
+static const AVFilterPad blurdetect_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = blurdetect_config_input,
+        .filter_frame = blurdetect_filter_frame,
+    },
+};
+
+static const AVFilterPad blurdetect_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+const AVFilter ff_vf_blurdetect = {
+    .name          = "blurdetect",
+    .description   = NULL_IF_CONFIG_SMALL("Blurdetect filter."),
+    .priv_size     = sizeof(BLRContext),
+    .init          = blurdetect_init,
+    .uninit        = blurdetect_uninit,
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    FILTER_INPUTS(blurdetect_inputs),
+    FILTER_OUTPUTS(blurdetect_outputs),
+    .priv_class    = &blurdetect_class,
+    .flags         = AVFILTER_FLAG_METADATA_ONLY,
+};
+
diff --git a/tests/fate/filter-video.mak b/tests/fate/filter-video.mak
index 6c0d8df032..68f4c084f8 100644
--- a/tests/fate/filter-video.mak
+++ b/tests/fate/filter-video.mak
@@ -867,6 +867,9 @@ fate-filter-meta-4560-rotate0: CMD = framecrc -auto_conversion_filters -flags +b
 
 REFCMP_DEPS = FFMPEG LAVFI_INDEV TESTSRC2_FILTER AVGBLUR_FILTER METADATA_FILTER
 
+FATE_FILTER-$(call ALLYES, $(REFCMP_DEPS) BLURDETECT_FILTER) += fate-filter-refcmp-blurdetect-yuv
+fate-filter-refcmp-blurdetect-yuv: CMD = cmp_metadata blurdetect yuv420p 0.015
+
 FATE_FILTER-$(call ALLYES, $(REFCMP_DEPS) PSNR_FILTER) += fate-filter-refcmp-psnr-rgb
 fate-filter-refcmp-psnr-rgb: CMD = refcmp_metadata psnr rgb24 0.002
 
diff --git a/tests/ref/fate/filter-refcmp-blurdetect-yuv b/tests/ref/fate/filter-refcmp-blurdetect-yuv
new file mode 100644
index 0000000000..a64a9a07ba
--- /dev/null
+++ b/tests/ref/fate/filter-refcmp-blurdetect-yuv
@@ -0,0 +1,10 @@
+frame:0    pts:0       pts_time:0
+lavfi.blur=4.480640
+frame:1    pts:1       pts_time:1
+lavfi.blur=4.569398
+frame:2    pts:2       pts_time:2
+lavfi.blur=4.609386
+frame:3    pts:3       pts_time:3
+lavfi.blur=4.357340
+frame:4    pts:4       pts_time:4
+lavfi.blur=4.392871
Thilo Borgmann April 24, 2022, 10:08 p.m. UTC | #10
Am 25.04.22 um 00:03 schrieb Thilo Borgmann:
> Am 24.04.22 um 19:28 schrieb Thilo Borgmann:
>> Am 23.04.22 um 15:32 schrieb Thilo Borgmann:
>>> Hi,
>>>
>>>>>>> v3 updated to current HEAD.
>>>>>>>
>>>>>>> Named blurdetect filter now.
>>>>>>> Minor fixes on allocation and removed -f option.
>>>>>>>
>>>>>>
>>>>>> Please make this per plane filtering, with default to measure only first
>>>>>> plane.
>>>>>
>>>>> done in v4.
>>>>>
>>>>> (Will add Changelog, version.h and fate test once the filter itself looks ok)
>>>>
>>>> Ping.
>>>
>>> v5 according to IRC comments.
>>
>> v6 (1/2 and 2/2) according to IRC comments. LGTM'd there, applying soon.
>>
>> Added Changelog, version.h, FATE.
> 
> v7: removed useless debug garbage. Still applying soon.

v8: and now even with adapted FATE.

-Thilo
From 72f1631e8994e15eac58c5c9a8c0fcf14ef627ad Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Mon, 25 Apr 2022 00:07:04 +0200
Subject: [PATCH v8 2/2] lavfi: Add blurdetect filter

---
 Changelog                                   |   1 +
 doc/filters.texi                            |  52 +++
 libavfilter/Makefile                        |   1 +
 libavfilter/allfilters.c                    |   1 +
 libavfilter/version.h                       |   2 +-
 libavfilter/vf_blurdetect.c                 | 395 ++++++++++++++++++++
 tests/fate/filter-video.mak                 |   3 +
 tests/ref/fate/filter-refcmp-blurdetect-yuv |  10 +
 8 files changed, 464 insertions(+), 1 deletion(-)
 create mode 100644 libavfilter/vf_blurdetect.c
 create mode 100644 tests/ref/fate/filter-refcmp-blurdetect-yuv

diff --git a/Changelog b/Changelog
index 7a63e3d1ee..4d467eb741 100644
--- a/Changelog
+++ b/Changelog
@@ -13,6 +13,7 @@ version 5.1:
 - pixelize video filter
 - colormap video filter
 - colorchart video source filter
+- blurdetect filter
 
 
 version 5.0:
diff --git a/doc/filters.texi b/doc/filters.texi
index c8699b9099..499f3adcd9 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -7997,6 +7997,58 @@ tblend=all_mode=grainextract
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@anchor{blurdetect}
+@section blurdetect
+
+Determines blurriness of frames without altering the input frames.
+
+Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric."
+Allows for a block-based abbreviation.
+
+The filter accepts the following options:
+
+@table @option
+@item low
+@item high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be chosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+
+@item radius
+Define the radius to search around an edge pixel for local maxima.
+
+@item block_pct
+Determine blurriness only for the most significant blocks, given in percentage.
+
+@item block_width
+Determine blurriness for blocks of width @var{block_width}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_height}.
+
+@item block_height
+Determine blurriness for blocks of height @var{block_height}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_width}.
+
+@item planes
+Set planes to filter. Default is first only.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Determine blur for 80% of most significant 32x32 blocks:
+@example
+blurdetect=block_width=32:block_height=32:block_pct=80
+@end example
+@end itemize
+
 @section bm3d
 
 Denoise frames using Block-Matching 3D algorithm.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 38ca379e5a..1db097b464 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -195,6 +195,7 @@ OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o framesync.o
 OBJS-$(CONFIG_BLEND_VULKAN_FILTER)           += vf_blend_vulkan.o framesync.o vulkan.o vulkan_filter.o
+OBJS-$(CONFIG_BLURDETECT_FILTER)             += vf_blurdetect.o edge_common.o
 OBJS-$(CONFIG_BM3D_FILTER)                   += vf_bm3d.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o boxblur.o
 OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 36fa3ae8d7..2ad523fd0f 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -183,6 +183,7 @@ extern const AVFilter ff_vf_blackdetect;
 extern const AVFilter ff_vf_blackframe;
 extern const AVFilter ff_vf_blend;
 extern const AVFilter ff_vf_blend_vulkan;
+extern const AVFilter ff_vf_blurdetect;
 extern const AVFilter ff_vf_bm3d;
 extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
diff --git a/libavfilter/version.h b/libavfilter/version.h
index 9add1658e5..8f1b16969a 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFILTER_VERSION_MINOR  36
+#define LIBAVFILTER_VERSION_MINOR  37
 #define LIBAVFILTER_VERSION_MICRO 100
 
 
diff --git a/libavfilter/vf_blurdetect.c b/libavfilter/vf_blurdetect.c
new file mode 100644
index 0000000000..7c0f5ce68a
--- /dev/null
+++ b/libavfilter/vf_blurdetect.c
@@ -0,0 +1,395 @@
+/*
+ * Copyright (c) 2021 Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * No-reference blurdetect filter
+ *
+ * Implementing:
+ * Marziliano, Pina, et al. "A no-reference perceptual blur metric." Proceedings.
+ * International conference on image processing. Vol. 3. IEEE, 2002.
+ * https://infoscience.epfl.ch/record/111802/files/14%20A%20no-reference%20perceptual%20blur%20metric.pdf
+ *
+ * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixelutils.h"
+#include "libavutil/motion_vector.h"
+#include "libavutil/qsort.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "edge_common.h"
+
+static int comp(const float *a,const float *b)
+{
+    return FFDIFFSIGN(*a, *b);
+}
+
+typedef struct BLRContext {
+    const AVClass *class;
+
+    int hsub, vsub;
+    int nb_planes;
+
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    int     radius;        // radius during local maxima detection
+    int     block_pct;     // percentage of "sharpest" blocks in the image to use for bluriness calculation
+    int     block_width;   // width for block abbreviation
+    int     block_height;  // height for block abbreviation
+    int     planes;        // number of planes to filter
+
+    double   blur_total;
+    uint64_t nb_frames;
+
+    float    *blks;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+} BLRContext;
+
+#define OFFSET(x) offsetof(BLRContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption blurdetect_options[] = {
+    { "high",          "set high threshold", OFFSET(high), AV_OPT_TYPE_FLOAT, {.dbl=30/255.}, 0, 1, FLAGS },
+    { "low",           "set low threshold",  OFFSET(low),  AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "radius",        "search radius for maxima detection", OFFSET(radius), AV_OPT_TYPE_INT, {.i64=50}, 1, 100, FLAGS },
+    { "block_pct",     "block pooling threshold when calculating blurriness", OFFSET(block_pct), AV_OPT_TYPE_INT, {.i64=80}, 1, 100, FLAGS },
+    { "block_width",   "block size for block-based abbreviation of blurriness", OFFSET(block_width), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "block_height",  "block size for block-based abbreviation of blurriness", OFFSET(block_height), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "planes",        "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT, {.i64=1}, 0, 15, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blurdetect);
+
+static av_cold int blurdetect_init(AVFilterContext *ctx)
+{
+    BLRContext *s = ctx->priv;
+
+    s->low_u8  = s->low  * 255. + .5;
+    s->high_u8 = s->high * 255. + .5;
+
+    return 0;
+}
+
+static int blurdetect_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BLRContext      *s   = ctx->priv;
+    const int bufsize    = inlink->w * inlink->h;
+    const AVPixFmtDescriptor *pix_desc;
+
+    pix_desc = av_pix_fmt_desc_get(inlink->format);
+    s->hsub = pix_desc->log2_chroma_w;
+    s->vsub = pix_desc->log2_chroma_h;
+    s->nb_planes = av_pix_fmt_count_planes(inlink->format);
+
+    if (s->block_width  < 1 || s->block_height < 1) {
+        s->block_width  = inlink->w;
+        s->block_height = inlink->h;
+    }
+
+    s->tmpbuf     = av_malloc(bufsize);
+    s->filterbuf  = av_malloc(bufsize);
+    s->gradients  = av_calloc(bufsize, sizeof(*s->gradients));
+    s->directions = av_malloc(bufsize);
+    s->blks       = av_calloc((inlink->w / s->block_width) * (inlink->h / s->block_height),
+                              sizeof(*s->blks));
+
+    if (!s->tmpbuf || !s->filterbuf || !s->gradients || !s->directions || !s->blks)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+// edge width is defined as the distance between surrounding maxima of the edge pixel
+static float edge_width(BLRContext *blr, int i, int j, int8_t dir, int w, int h,
+                        int edge, const uint8_t *src, int src_linesize)
+{
+    float width = 0;
+    int dX, dY;
+    int sign;
+    int tmp;
+    int p1;
+    int p2;
+    int k, x, y;
+    int edge1;
+    int edge2;
+    float luma1 = 0.0; // average luma difference per edge pixel
+    float luma2 = 0.0;
+    int radius = blr->radius;
+
+    switch(dir) {
+    case DIRECTION_HORIZONTAL: dX = 1; dY =  0; break;
+    case DIRECTION_VERTICAL:   dX = 0; dY =  1; break;
+    case DIRECTION_45UP:       dX = 1; dY = -1; break;
+    case DIRECTION_45DOWN:     dX = 1; dY =  1; break;
+    }
+
+    // determines if search in direction dX/dY is looking for a maximum or minimum
+    sign = src[j * src_linesize + i] > src[(j - dY) * src_linesize + i - dX] ? 1 : -1;
+
+    // search in -(dX/dY) direction
+    for (k = 0; k < radius; k++) {
+        x = i - k*dX;
+        y = j - k*dY;
+        p1 = y * src_linesize + x;
+        x -= dX;
+        y -= dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp <= 0) // local maximum found
+            break;
+
+        luma1 += tmp;
+    }
+    if (k > 0) luma1 /= k;
+    edge1 = k;
+    width += k;
+
+    // search in +(dX/dY) direction
+    for (k = 0; k < radius; k++) {
+        x = i + k * dX;
+        y = j + k * dY;
+        p1 = y * src_linesize + x;
+        x += dX;
+        y += dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp >= 0) // local maximum found
+            break;
+
+        luma2 -= tmp;
+    }
+    if (k > 0) luma2 /= k;
+    edge2 = k;
+    width += k;
+
+    // for 45 degree directions approximate edge width in pixel units: 0.7 ~= sqrt(2)/2
+    if (dir == DIRECTION_45UP || dir == DIRECTION_45DOWN)
+        width *= 0.7;
+
+    return width;
+}
+
+static float calculate_blur(BLRContext *s, int w, int h, int hsub, int vsub,
+                            uint8_t* dir, int dir_linesize,
+                            uint8_t* dst, int dst_linesize,
+                            uint8_t* src, int src_linesize)
+{
+    float total_width = 0.0;
+    int block_count;
+    double block_total_width;
+
+    int i, j;
+    int blkcnt = 0;
+
+    float *blks = s->blks;
+    float block_pool_threshold = s->block_pct / 100.0;
+
+    int block_width  = AV_CEIL_RSHIFT(s->block_width,  hsub);
+    int block_height = AV_CEIL_RSHIFT(s->block_height, vsub);
+    int brows = h / block_height;
+    int bcols = w / block_width;
+
+    for (int blkj = 0; blkj < brows; blkj++) {
+        for (int blki = 0; blki < bcols; blki++) {
+            block_total_width = 0.0;
+            block_count = 0;
+            for (int inj = 0; inj < block_height; inj++) {
+                for (int ini = 0; ini < block_width; ini++) {
+                    i = blki * block_width + ini;
+                    j = blkj * block_height + inj;
+
+                    if (dst[j * dst_linesize + i] > 0) {
+                        float width = edge_width(s, i, j, dir[j*dir_linesize+i],
+                                                 w, h, dst[j*dst_linesize+i],
+                                                 src, src_linesize);
+                        if (width > 0.001) { // throw away zeros
+                            block_count++;
+                            block_total_width += width;
+                        }
+                    }
+                }
+            }
+            // if not enough edge pixels in a block, consider it smooth
+            if (block_total_width >= 2) {
+                blks[blkcnt] = block_total_width / block_count;
+                blkcnt++;
+            }
+        }
+    }
+
+    // simple block pooling by sorting and keeping the sharper blocks
+    AV_QSORT(blks, blkcnt, float, comp);
+    blkcnt = ceil(blkcnt * block_pool_threshold);
+    for (int i = 0; i < blkcnt; i++) {
+        total_width += blks[i];
+    }
+
+    return  total_width / blkcnt;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    av_dict_set(metadata, key, value, 0);
+}
+
+static int blurdetect_filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx  = inlink->dst;
+    BLRContext *s         = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+
+    const int inw = inlink->w;
+    const int inh = inlink->h;
+
+    uint8_t *tmpbuf     = s->tmpbuf;
+    uint8_t *filterbuf  = s->filterbuf;
+    uint16_t *gradients = s->gradients;
+    int8_t *directions  = s->directions;
+
+    float blur = 0.0f;
+    int nplanes = 0;
+    AVDictionary **metadata;
+    metadata = &in->metadata;
+
+    for (int plane = 0; plane < s->nb_planes; plane++) {
+        int hsub = plane == 1 || plane == 2 ? s->hsub : 0;
+        int vsub = plane == 1 || plane == 2 ? s->vsub : 0;
+        int w = AV_CEIL_RSHIFT(inw, hsub);
+        int h = AV_CEIL_RSHIFT(inh, vsub);
+
+        if (!((1 << plane) & s->planes))
+            continue;
+
+        nplanes++;
+
+        // gaussian filter to reduce noise
+        ff_gaussian_blur(w, h,
+                         filterbuf,  w,
+                         in->data[plane], in->linesize[plane]);
+
+        // compute the 16-bits gradients and directions for the next step
+        ff_sobel(w, h, gradients, w, directions, w, filterbuf, w);
+
+        // non_maximum_suppression() will actually keep & clip what's necessary and
+        // ignore the rest, so we need a clean output buffer
+        memset(tmpbuf, 0, inw * inh);
+        ff_non_maximum_suppression(w, h, tmpbuf, w, directions, w, gradients, w);
+
+
+        // keep high values, or low values surrounded by high values
+        ff_double_threshold(s->low_u8, s->high_u8, w, h,
+                            tmpbuf, w, tmpbuf, w);
+
+        blur += calculate_blur(s, w, h, hsub, vsub, directions, w,
+                              tmpbuf, w, filterbuf, w);
+    }
+
+    if (nplanes)
+        blur /= nplanes;
+
+    s->blur_total += blur;
+
+    // write stats
+    av_log(ctx, AV_LOG_VERBOSE, "blur: %.7f\n", blur);
+
+    set_meta(metadata, "lavfi.blur", blur);
+
+    s->nb_frames = inlink->frame_count_in;
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void blurdetect_uninit(AVFilterContext *ctx)
+{
+    BLRContext *s = ctx->priv;
+
+    if (s->nb_frames > 0) {
+        av_log(ctx, AV_LOG_INFO, "blur mean: %.7f\n",
+               s->blur_total / s->nb_frames);
+    }
+
+    av_freep(&s->tmpbuf);
+    av_freep(&s->filterbuf);
+    av_freep(&s->gradients);
+    av_freep(&s->directions);
+    av_freep(&s->blks);
+}
+
+static const enum AVPixelFormat pix_fmts[] = {
+    AV_PIX_FMT_GRAY8,
+    AV_PIX_FMT_GBRP,     AV_PIX_FMT_GBRAP,
+    AV_PIX_FMT_YUV422P,  AV_PIX_FMT_YUV420P,
+    AV_PIX_FMT_YUV444P,  AV_PIX_FMT_YUV440P,
+    AV_PIX_FMT_YUV411P,  AV_PIX_FMT_YUV410P,
+    AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUVJ420P,
+    AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ444P,
+    AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
+    AV_PIX_FMT_NONE
+};
+
+static const AVFilterPad blurdetect_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = blurdetect_config_input,
+        .filter_frame = blurdetect_filter_frame,
+    },
+};
+
+static const AVFilterPad blurdetect_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+const AVFilter ff_vf_blurdetect = {
+    .name          = "blurdetect",
+    .description   = NULL_IF_CONFIG_SMALL("Blurdetect filter."),
+    .priv_size     = sizeof(BLRContext),
+    .init          = blurdetect_init,
+    .uninit        = blurdetect_uninit,
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    FILTER_INPUTS(blurdetect_inputs),
+    FILTER_OUTPUTS(blurdetect_outputs),
+    .priv_class    = &blurdetect_class,
+    .flags         = AVFILTER_FLAG_METADATA_ONLY,
+};
+
diff --git a/tests/fate/filter-video.mak b/tests/fate/filter-video.mak
index 6c0d8df032..68f4c084f8 100644
--- a/tests/fate/filter-video.mak
+++ b/tests/fate/filter-video.mak
@@ -867,6 +867,9 @@ fate-filter-meta-4560-rotate0: CMD = framecrc -auto_conversion_filters -flags +b
 
 REFCMP_DEPS = FFMPEG LAVFI_INDEV TESTSRC2_FILTER AVGBLUR_FILTER METADATA_FILTER
 
+FATE_FILTER-$(call ALLYES, $(REFCMP_DEPS) BLURDETECT_FILTER) += fate-filter-refcmp-blurdetect-yuv
+fate-filter-refcmp-blurdetect-yuv: CMD = cmp_metadata blurdetect yuv420p 0.015
+
 FATE_FILTER-$(call ALLYES, $(REFCMP_DEPS) PSNR_FILTER) += fate-filter-refcmp-psnr-rgb
 fate-filter-refcmp-psnr-rgb: CMD = refcmp_metadata psnr rgb24 0.002
 
diff --git a/tests/ref/fate/filter-refcmp-blurdetect-yuv b/tests/ref/fate/filter-refcmp-blurdetect-yuv
new file mode 100644
index 0000000000..426321db0c
--- /dev/null
+++ b/tests/ref/fate/filter-refcmp-blurdetect-yuv
@@ -0,0 +1,10 @@
+frame:0    pts:0       pts_time:0
+lavfi.blur=4.499666
+frame:1    pts:1       pts_time:1
+lavfi.blur=4.677492
+frame:2    pts:2       pts_time:2
+lavfi.blur=4.735711
+frame:3    pts:3       pts_time:3
+lavfi.blur=4.532343
+frame:4    pts:4       pts_time:4
+lavfi.blur=4.532660
Thilo Borgmann April 25, 2022, 6:52 p.m. UTC | #11
Am 25.04.22 um 00:08 schrieb Thilo Borgmann:
> Am 25.04.22 um 00:03 schrieb Thilo Borgmann:
>> Am 24.04.22 um 19:28 schrieb Thilo Borgmann:
>>> Am 23.04.22 um 15:32 schrieb Thilo Borgmann:
>>>> Hi,
>>>>
>>>>>>>> v3 updated to current HEAD.
>>>>>>>>
>>>>>>>> Named blurdetect filter now.
>>>>>>>> Minor fixes on allocation and removed -f option.
>>>>>>>>
>>>>>>>
>>>>>>> Please make this per plane filtering, with default to measure only first
>>>>>>> plane.
>>>>>>
>>>>>> done in v4.
>>>>>>
>>>>>> (Will add Changelog, version.h and fate test once the filter itself looks ok)
>>>>>
>>>>> Ping.
>>>>
>>>> v5 according to IRC comments.
>>>
>>> v6 (1/2 and 2/2) according to IRC comments. LGTM'd there, applying soon.
>>>
>>> Added Changelog, version.h, FATE.
>>
>> v7: removed useless debug garbage. Still applying soon.
> 
> v8: and now even with adapted FATE.

Pushed, thanks!

-Thilo
diff mbox series

Patch

diff --git a/doc/filters.texi b/doc/filters.texi
index b4f888c14d..d066041e21 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -7712,6 +7712,61 @@  tblend=all_mode=grainextract
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@anchor{blurriness}
+@section blurriness
+
+Determines blurriness of frames without altering the input frames.
+
+Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric."
+Allows for a block-based abbreviation.
+
+The filter accepts the following options:
+
+@table @option
+@item low
+@item high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be chosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+
+@item radius
+Define the radius to search around an edge pixel for local maxima.
+
+@item block_pct
+Determine blurriness only for the most significant blocks, given in percentage.
+
+@item block_width
+Determine blurriness for blocks of width @var{block_width}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_height}.
+
+@item block_height
+Determine blurriness for blocks of height @var{block_height}. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of @var{block_width}.
+
+@item stats_file, f
+If specified the filter will use the named file to save the PSNR of
+each individual frame. When filename equals "-" the data is sent to
+standard output.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Determine blurriness for 80% of most significant 32x32 blocks and write to stdout:
+@example
+blurriness=block_width=32:block_height=32:block_pct=80:f=-
+@end example
+@end itemize
+
+
 @section bm3d
 
 Denoise frames using Block-Matching 3D algorithm.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 1b559539ba..8dd1b2a947 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -188,6 +188,7 @@  OBJS-$(CONFIG_BITPLANENOISE_FILTER)          += vf_bitplanenoise.o
 OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o framesync.o
+OBJS-$(CONFIG_BLURRINESS_FILTER)             += vf_blurriness.o edge_common.o
 OBJS-$(CONFIG_BM3D_FILTER)                   += vf_bm3d.o framesync.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o boxblur.o
 OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index f250020159..121e37391d 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -180,6 +180,7 @@  extern const AVFilter ff_vf_bitplanenoise;
 extern const AVFilter ff_vf_blackdetect;
 extern const AVFilter ff_vf_blackframe;
 extern const AVFilter ff_vf_blend;
+extern const AVFilter ff_vf_blurriness;
 extern const AVFilter ff_vf_bm3d;
 extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
diff --git a/libavfilter/vf_blurriness.c b/libavfilter/vf_blurriness.c
new file mode 100644
index 0000000000..71b72d7211
--- /dev/null
+++ b/libavfilter/vf_blurriness.c
@@ -0,0 +1,366 @@ 
+/*
+ * Copyright (c) 2021 Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * No-reference blurriness metric filter
+ *
+ * Implementing:
+ * Marziliano, Pina, et al. "A no-reference perceptual blur metric." Proceedings.
+ * International conference on image processing. Vol. 3. IEEE, 2002.
+ * https://infoscience.epfl.ch/record/111802/files/14%20A%20no-reference%20perceptual%20blur%20metric.pdf
+ *
+ * @author Thilo Borgmann <thilo.borgmann _at_ mail.de>
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixelutils.h"
+#include "libavutil/motion_vector.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "edge_common.h"
+
+static int comp(const void *a,const void *b)
+{
+    float x = *(float*)a;
+    float y = *(float*)b;
+    if (x > y) return  1;
+    if (x < y) return -1;
+    return 0;
+}
+
+typedef struct BLRContext {
+    const AVClass *class;
+
+    float   low, high;
+    uint8_t low_u8, high_u8;
+    int     radius;        // radius during local maxima detection
+    int     block_pct;     // percentage of "sharpest" blocks in the image to use for bluriness calculation
+    int     block_width;   // width for block abbreviation
+    int     block_height;  // height for block abbreviation
+
+    float    blur_total;
+    uint64_t nb_frames;
+
+    float    *blks;
+    uint8_t  *filterbuf;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+} BLRContext;
+
+#define OFFSET(x) offsetof(BLRContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption blr_options[] = {
+    { "high",          "set high threshold", OFFSET(high), AV_OPT_TYPE_FLOAT, {.dbl=30/255.}, 0, 1, FLAGS },
+    { "low",           "set low threshold",  OFFSET(low),  AV_OPT_TYPE_FLOAT, {.dbl=15/255.}, 0, 1, FLAGS },
+    { "radius",        "search radius for maxima detection", OFFSET(radius), AV_OPT_TYPE_INT, {.i64=50}, 1, 100, FLAGS },
+    { "block_pct",     "block pooling threshold when calculating blurriness", OFFSET(block_pct), AV_OPT_TYPE_INT, {.i64=80}, 1, 100, FLAGS },
+    { "block_width",   "block size for block-based abbreviation of blurriness", OFFSET(block_width), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { "block_height",  "block size for block-based abbreviation of blurriness", OFFSET(block_height), AV_OPT_TYPE_INT, {.i64=-1}, -1, INT_MAX, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blr);
+
+static av_cold int blr_init(AVFilterContext *ctx)
+{
+    BLRContext *blr = ctx->priv;
+
+    blr->low_u8  = blr->low  * 255. + .5;
+    blr->high_u8 = blr->high * 255. + .5;
+
+    return 0;
+}
+
+static int blr_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx    = inlink->dst;
+    BLRContext      *blr    = ctx->priv;
+    const int       bufsize = inlink->w * inlink->h;
+
+    if (blr->block_width  < 1 || blr->block_height < 1) {
+        blr->block_width  = inlink->w;
+        blr->block_height = inlink->h;
+    }
+
+    blr->tmpbuf     = av_malloc(bufsize);
+    blr->filterbuf  = av_malloc(bufsize);
+    blr->gradients  = av_calloc(bufsize, sizeof(*blr->gradients));
+    blr->directions = av_malloc(bufsize);
+    if (!blr->tmpbuf || !blr->filterbuf || !blr->gradients || !blr->directions)
+        return AVERROR(ENOMEM);
+
+    blr->blks = av_calloc((inlink->w / blr->block_width) * (inlink->h / blr->block_height),
+                          sizeof(*blr->blks));
+
+    return 0;
+}
+
+// edge width is defined as the distance between surrounding maxima of the edge pixel
+static float edge_width(BLRContext *blr, int i, int j, int8_t dir, int w, int h,
+                        int edge, const uint8_t *src, int src_linesize)
+{
+    float width = 0;
+    int dX, dY;
+    int sign;
+    int tmp;
+    int p1;
+    int p2;
+    int k, x, y;
+    int edge1;
+    int edge2;
+    float luma1 = 0.0; // average luma difference per edge pixel
+    float luma2 = 0.0;
+    int radius = blr->radius;
+
+    switch(dir)
+    {
+    case DIRECTION_HORIZONTAL: dX = 1; dY =  0; break;
+    case DIRECTION_VERTICAL:   dX = 0; dY =  1; break;
+    case DIRECTION_45UP:       dX = 1; dY = -1; break;
+    case DIRECTION_45DOWN:     dX = 1; dY =  1; break;
+    }
+    if (dir == DIRECTION_HORIZONTAL) return 0;
+
+    // determines if search in direction dX/dY is looking for a maximum or minimum
+    sign = src[j * src_linesize + i] > src[(j - dY) * src_linesize + i - dX] ? 1 : -1;
+
+    // search in -(dX/dY) direction
+    for (k = 0; k < radius; k++)
+    {
+        x = i - k*dX;
+        y = j - k*dY;
+        p1 = y * src_linesize + x;
+        x -= dX;
+        y -= dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp <= 0) // local maximum found
+            break;
+
+        luma1 += tmp;
+    }
+    if (k > 0) luma1 /= k;
+    edge1 = k;
+    width += k;
+
+    // search in +(dX/dY) direction
+    for (k = 0; k < radius; k++)
+    {
+        x = i + k * dX;
+        y = j + k * dY;
+        p1 = y * src_linesize + x;
+        x += dX;
+        y += dY;
+        p2 = y * src_linesize + x;
+        if (x < 0 || x >= w || y < 0 || y >= h)
+            return 0;
+
+        tmp = (src[p1] - src[p2]) * sign;
+
+        if (tmp >= 0) // local maximum found
+            break;
+
+        luma2 -= tmp;
+    }
+    if (k > 0) luma2 /= k;
+    edge2 = k;
+    width += k;
+
+    // for 45 degree directions approximate edge width in pixel units: 0.7 ~= sqrt(2)/2
+    if (dir == DIRECTION_45UP || dir == DIRECTION_45DOWN)
+        width *= 0.7;
+
+    return width;
+}
+
+static float calculate_blur(BLRContext *blr, int w, int h,
+                            uint8_t* dir, int dir_linesize,
+                            uint8_t* dst, int dst_linesize,
+                            uint8_t* src, int src_linesize)
+{
+    float total_width = 0.0;
+    int block_count;
+    float block_total_width;
+
+    int i, j;
+    int blkcnt = 0;
+
+    float *blks = blr->blks;
+    int block_pct = blr->block_pct;
+    float block_pool_threshold = block_pct / 100.0;
+
+    int block_width  = blr->block_width;
+    int block_height = blr->block_height;
+    int brows = h / block_height;
+    int bcols = w / block_width;
+
+    for (int blkj = 0; blkj < brows; blkj++) {
+        for (int blki = 0; blki < bcols; blki++) {
+            block_total_width = 0;
+            block_count = 0;
+            for (int inj = 0; inj < block_height; inj++) {
+                for (int ini = 0; ini < block_width; ini++) {
+                    i = blki * block_width + ini;
+                    j = blkj * block_height + inj;
+
+                    if (dst[j * dst_linesize + i] > 0) {
+                        float width = edge_width(blr, i, j, dir[j*dir_linesize+i],
+                                                 w, h, dst[j*dst_linesize+i],
+                                                 src, src_linesize);
+                        if (width > 0.001) { // throw away zeros
+                            block_count++;
+                            block_total_width += width;
+                        }
+                    }
+                }
+            }
+            // if not enough edge pixels in a block, consider it smooth
+            if (block_total_width >= 2) {
+                blks[blkcnt] = block_total_width / block_count;
+                blkcnt++;
+            }
+        }
+    }
+
+    // simple block pooling by sorting and keeping the sharper blocks
+    qsort(blks, blkcnt, sizeof(*blks), comp);
+    blkcnt = ceil(blkcnt * block_pool_threshold);
+    for (int i = 0; i < blkcnt; i++) {
+        total_width += blks[i];
+    }
+
+    return  total_width / blkcnt;
+}
+
+static void set_meta(AVDictionary **metadata, const char *key, float d)
+{
+    char value[128];
+    snprintf(value, sizeof(value), "%f", d);
+    av_dict_set(metadata, key, value, 0);
+}
+
+static int blr_filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BLRContext *blr      = ctx->priv;
+
+    const int w = inlink->w;
+    const int h = inlink->h;
+
+    uint8_t *tmpbuf     = blr->tmpbuf;
+    uint8_t *filterbuf  = blr->filterbuf;
+    uint16_t *gradients = blr->gradients;
+    int8_t *directions  = blr->directions;
+
+    float blur;
+    AVDictionary **metadata;
+    metadata = &in->metadata;
+
+    // gaussian filter to reduce noise
+    ff_gaussian_blur(w, h,
+                     filterbuf,  w,
+                     in->data[0], in->linesize[0]);
+
+    // compute the 16-bits gradients and directions for the next step
+    ff_sobel(w, h, gradients, w, directions, w, filterbuf, w);
+
+    // non_maximum_suppression() will actually keep & clip what's necessary and
+    // ignore the rest, so we need a clean output buffer
+    memset(tmpbuf, 0, w * h);
+    ff_non_maximum_suppression(w, h, tmpbuf, w, directions, w, gradients, w);
+
+
+    // keep high values, or low values surrounded by high values
+    ff_double_threshold(blr->low_u8, blr->high_u8, w, h,
+                              tmpbuf, w, tmpbuf, w);
+
+
+    blur = calculate_blur(blr, w, h, directions, w,
+                          tmpbuf, w, filterbuf, w);
+
+    blr->blur_total += blur;
+
+    // write stats
+    av_log(ctx, AV_LOG_VERBOSE, "blur: %.7f\n", blur);
+
+    set_meta(metadata, "lavfi.blur", blur);
+
+    blr->nb_frames++;
+
+    return ff_filter_frame(ctx->outputs[0], in);
+}
+
+static av_cold void blr_uninit(AVFilterContext *ctx)
+{
+    BLRContext *blr = ctx->priv;
+
+    if (blr->nb_frames > 0) {
+        int nb_frames = blr->nb_frames;
+        av_log(ctx, AV_LOG_INFO, "blur mean: %.7f\n",
+               blr->blur_total / nb_frames);
+    }
+
+    av_freep(&blr->tmpbuf);
+    av_freep(&blr->filterbuf);
+    av_freep(&blr->gradients);
+    av_freep(&blr->directions);
+    av_freep(&blr->blks);
+}
+
+static const enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
+
+static const AVFilterPad blr_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = blr_config_input,
+        .filter_frame = blr_filter_frame,
+    },
+};
+
+static const AVFilterPad blr_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+AVFilter ff_vf_blurriness = {
+    .name          = "blurriness",
+    .description   = NULL_IF_CONFIG_SMALL("Blurriness metric filter."),
+    .priv_size     = sizeof(BLRContext),
+    .init          = blr_init,
+    .uninit        = blr_uninit,
+    FILTER_PIXFMTS_ARRAY(pix_fmts),
+    FILTER_INPUTS(blr_inputs),
+    FILTER_OUTPUTS(blr_outputs),
+    .priv_class    = &blr_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
+};