[FFmpeg-devel] avfilter: implement halve filter

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 9ab65eb..a986322 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -250,6 +250,7 @@  OBJS-$(CONFIG_RANDOM_FILTER)                 += vf_random.o
 OBJS-$(CONFIG_READVITC_FILTER)               += vf_readvitc.o
 OBJS-$(CONFIG_REALTIME_FILTER)               += f_realtime.o
 OBJS-$(CONFIG_REMAP_FILTER)                  += vf_remap.o framesync.o
+OBJS-$(CONFIG_HALVE_FILTER)                  += vf_halve.o framesync.o
 OBJS-$(CONFIG_REMOVEGRAIN_FILTER)            += vf_removegrain.o
 OBJS-$(CONFIG_REMOVELOGO_FILTER)             += bbox.o lswsutils.o lavfutils.o vf_removelogo.o
 OBJS-$(CONFIG_REPEATFIELDS_FILTER)           += vf_repeatfields.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 2c37818..0b9b69c 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -265,6 +265,7 @@  void avfilter_register_all(void)
     REGISTER_FILTER(READVITC,       readvitc,       vf);
     REGISTER_FILTER(REALTIME,       realtime,       vf);
     REGISTER_FILTER(REMAP,          remap,          vf);
+    REGISTER_FILTER(HALVE,          halve,          vf);
     REGISTER_FILTER(REMOVEGRAIN,    removegrain,    vf);
     REGISTER_FILTER(REMOVELOGO,     removelogo,     vf);
     REGISTER_FILTER(REPEATFIELDS,   repeatfields,   vf);
diff --git a/libavfilter/vf_halve.c b/libavfilter/vf_halve.c
new file mode 100644
index 0000000..dd77eb8
--- /dev/null
+++ b/libavfilter/vf_halve.c
@@ -0,0 +1,367 @@ 
+/*
+ * Copyright (c) 2016 Floris Sluiter
+ *
+ * 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
+ * Pixel halve filter
+ * This filter makes the target image exactly halve in size in x and y
+ * dimension of the source image by summing the corresponding four source
+ * pixels.
+ */
+
+#include "libavutil/imgutils.h"
+#include "libavutil/pixdesc.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "framesync.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct HalveContext {
+    const AVClass *class;
+    int nb_planes;
+    int nb_components;
+    int step;
+    FFFrameSync fs;
+    void (*halve_slice)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
+} HalveContext;
+
+#define OFFSET(x) offsetof(HalveContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption halve_options[] = {
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(halve);
+
+typedef struct ThreadData {
+    AVFrame *in, *out;
+    int nb_planes;
+    int nb_components;
+    int step;
+} ThreadData;
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_YUVA444P,
+        AV_PIX_FMT_YUV444P,
+        AV_PIX_FMT_YUVJ444P,
+        AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
+        AV_PIX_FMT_ARGB, AV_PIX_FMT_ABGR, AV_PIX_FMT_RGBA, AV_PIX_FMT_BGRA,
+        AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRAP,
+        AV_PIX_FMT_YUV444P9, AV_PIX_FMT_YUV444P10, AV_PIX_FMT_YUV444P12,
+        AV_PIX_FMT_YUV444P14, AV_PIX_FMT_YUV444P16,
+        AV_PIX_FMT_YUVA444P9, AV_PIX_FMT_YUVA444P10, AV_PIX_FMT_YUVA444P16,
+        AV_PIX_FMT_GBRP9, AV_PIX_FMT_GBRP10, AV_PIX_FMT_GBRP12,
+        AV_PIX_FMT_GBRP14, AV_PIX_FMT_GBRP16,
+        AV_PIX_FMT_GBRAP10, AV_PIX_FMT_GBRAP12, AV_PIX_FMT_GBRAP16,
+        AV_PIX_FMT_RGB48, AV_PIX_FMT_BGR48,
+        AV_PIX_FMT_RGBA64, AV_PIX_FMT_BGRA64,
+        AV_PIX_FMT_NONE
+    };
+    AVFilterFormats *pix_formats = NULL;
+    int ret;
+
+    if (!(pix_formats = ff_make_format_list(pix_fmts))) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+    if ((ret = ff_formats_ref(pix_formats, &ctx->inputs[0]->out_formats)) < 0 ||
+        (ret = ff_formats_ref(pix_formats, &ctx->outputs[0]->in_formats)) < 0)
+        goto fail;
+    return 0;
+fail:
+    if (pix_formats)
+        av_freep(&pix_formats->formats);
+    av_freep(&pix_formats);
+    return ret;
+}
+
+/**
+ * halve_planar algorithm expects planes of same size
+ * pixels are copied from source to target using :
+ * Target_frame[y][x] = Source_frame[ ymap[y][x] ][ [xmap[y][x] ];
+ */
+static void halve_planar_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    const ThreadData *td = (ThreadData*)arg;
+    const AVFrame *in  = td->in;
+    const AVFrame *out = td->out;
+    int x , y, plane;
+
+    for (plane = 0; plane < td->nb_planes ; plane++) {
+        uint8_t *dst        = out->data[plane];
+        const int dlinesize  = out->linesize[plane];
+        const uint8_t *src  = in->data[plane];
+        const int slinesize  = in->linesize[plane];
+        for (y = 0; y < out->height; y++) {
+            for (x = 0; x < out->width; x++, ++dst, src += 2) {
+                dst[0] = (uint8_t)(
+                    (
+                        (uint16_t)(src[0]) +
+                        (uint16_t)(src[slinesize]) +
+                        (uint16_t)(src[1]) +
+                        (uint16_t)(src[slinesize + 1])
+                    ) >> 2);
+            }
+            src  += 2 * slinesize - in->width;
+            dst  += dlinesize - out->width;
+        }
+    }
+}
+
+static void halve_planar16_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    const ThreadData *td = (ThreadData*)arg;
+    const AVFrame *in  = td->in;
+    const AVFrame *out = td->out;
+    int x , y, plane;
+
+    for (plane = 0; plane < td->nb_planes ; plane++) {
+        uint16_t *dst        = (uint16_t *)out->data[plane];
+        const int dlinesize  = out->linesize[plane] / 2;
+        const uint16_t *src  = (const uint16_t *)in->data[plane];
+        const int slinesize  = in->linesize[plane] / 2;
+        for (y = 0; y < out->height; y++) {
+            for (x = 0; x < out->width; x++, ++dst, ++src) {
+                dst[0] = (uint16_t)(
+                    (
+                        (uint32_t)(src[0]) +
+                        (uint32_t)(src[slinesize]) +
+                        (uint32_t)(src[1]) +
+                        (uint32_t)(src[slinesize + 1])
+                    ) >> 2);
+            }
+            src  += 2 * slinesize - in->width;
+            dst  += dlinesize - out->width;
+        }
+    }
+}
+
+
+
+/**
+ * halve_packed algorithm expects pixels with both padded bits (step) and
+ * number of components correctly set.
+ * pixels are copied from source to target using :
+ * Target_frame[y][x] = Source_frame[ ymap[y][x] ][ [xmap[y][x] ];
+ */
+static void halve_packed_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    const ThreadData *td = (ThreadData*)arg;
+    const AVFrame *in  = td->in;
+    const AVFrame *out = td->out;
+    uint8_t *dst = out->data[0];
+    const uint8_t *src  = in->data[0];
+    const int dlinesize = out->linesize[0];
+    const int slinesize = in->linesize[0];
+    const int step = td->step;
+    int c, x, y;
+
+    for (y = 0; y < out->height; y++) {
+        for (x = 0; x < out->width; x++, dst += step, src += step) {
+            for (c = 0; c < td->nb_components; ++c) {
+                dst[c] = (uint8_t)(
+                    (
+                        (uint16_t)(src[c]) +
+                        (uint16_t)(src[slinesize + c]) +
+                        (uint16_t)(src[step + c]) +
+                        (uint16_t)(src[slinesize + step + c])
+                    ) >> 2);
+            }
+        }
+        src  += 2 * slinesize - in->width * step;
+        dst  += dlinesize - out->width * step;
+    }
+}
+
+static void halve_packed16_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    const ThreadData *td = (ThreadData*)arg;
+    const AVFrame *in  = td->in;
+    const AVFrame *out = td->out;
+    uint16_t *dst = (uint16_t *)out->data[0];
+    const uint16_t *src  = (const uint16_t *)in->data[0];
+    const int dlinesize = out->linesize[0] / 2;
+    const int slinesize = in->linesize[0] / 2;
+    const int step = td->step / 2;
+    int c, x, y;
+
+    for (y = 0; y < out->height; y++) {
+        for (x = 0; x < out->width; x++, dst += step, src += step) {
+            for (c = 0; c < td->nb_components; ++c) {
+                dst[c] = (uint16_t)(
+                    (
+                        (uint32_t)(src[c]) +
+                        (uint32_t)(src[slinesize + c]) +
+                        (uint32_t)(src[step + c]) +
+                        (uint32_t)(src[slinesize + step + c])
+                    ) >> 2);
+            }
+        }
+        src  += 2 * slinesize - in->width * step;
+        dst  += dlinesize - out->width * step;
+    }
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    HalveContext *s = ctx->priv;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+
+    s->nb_planes = av_pix_fmt_count_planes(inlink->format);
+    s->nb_components = desc->nb_components;
+
+    if (desc->comp[0].depth == 8) {
+        if (s->nb_planes > 1 || s->nb_components == 1) {
+            s->halve_slice = halve_planar_slice;
+        } else {
+            s->halve_slice = halve_packed_slice;
+        }
+    } else {
+        if (s->nb_planes > 1 || s->nb_components == 1) {
+            s->halve_slice = halve_planar16_slice;
+        } else {
+            s->halve_slice = halve_packed16_slice;
+        }
+    }
+
+    s->step = av_get_padded_bits_per_pixel(desc) >> 3;
+    return 0;
+}
+
+static int process_frame(FFFrameSync *fs)
+{
+    AVFilterContext *ctx = fs->parent;
+    HalveContext *s = fs->opaque;
+    AVFilterLink *outlink = ctx->outputs[0];
+    AVFrame *out, *in;
+    int ret;
+
+    if ((ret = ff_framesync_get_frame(&s->fs, 0, &in,   0)) < 0)
+        return ret;
+
+    if (ctx->is_disabled) {
+        out = av_frame_clone(in);
+        if (!out)
+            return AVERROR(ENOMEM);
+    } else {
+        ThreadData td;
+
+        out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+        if (!out)
+            return AVERROR(ENOMEM);
+        av_frame_copy_props(out, in);
+
+        td.in  = in;
+        td.out = out;
+        td.nb_planes = s->nb_planes;
+        td.nb_components = s->nb_components;
+        td.step = s->step;
+        ctx->internal->execute(ctx, s->halve_slice, &td, NULL, FFMIN(outlink->h, ctx->graph->nb_threads));
+    }
+    out->pts = av_rescale_q(in->pts, s->fs.time_base, outlink->time_base);
+
+    return ff_filter_frame(outlink, out);
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    HalveContext *s = ctx->priv;
+    AVFilterLink *srclink = ctx->inputs[0];
+    FFFrameSyncIn *in;
+    int ret;
+
+    outlink->w = srclink->w / 2;
+    outlink->h = srclink->h / 2;
+    outlink->time_base = srclink->time_base;
+    outlink->sample_aspect_ratio = srclink->sample_aspect_ratio;
+    outlink->frame_rate = srclink->frame_rate;
+
+    ret = ff_framesync_init(&s->fs, ctx, 1);
+    if (ret < 0)
+        return ret;
+
+    in = s->fs.in;
+    in[0].time_base = srclink->time_base;
+    in[0].sync   = 2;
+    in[0].before = EXT_STOP;
+    in[0].after  = EXT_STOP;
+    s->fs.opaque   = s;
+    s->fs.on_event = process_frame;
+
+    return ff_framesync_configure(&s->fs);
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
+{
+    HalveContext *s = inlink->dst->priv;
+    return ff_framesync_filter_frame(&s->fs, inlink, buf);
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    HalveContext *s = outlink->src->priv;
+    return ff_framesync_request_frame(&s->fs, outlink);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    HalveContext *s = ctx->priv;
+
+    ff_framesync_uninit(&s->fs);
+}
+
+static const AVFilterPad halve_inputs[] = {
+    {
+        .name         = "source",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+        .config_props = config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad halve_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_output,
+        .request_frame = request_frame,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_halve = {
+    .name          = "halve",
+    .description   = NULL_IF_CONFIG_SMALL("Halve image"),
+    .priv_size     = sizeof(HalveContext),
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .inputs        = halve_inputs,
+    .outputs       = halve_outputs,
+    .priv_class    = &halve_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
+};