[FFmpeg-devel,2/2] lavc/libx264: add mb_info option

From 2afd999f38fc3a7c3f56aba1d874de00bc9575ba Mon Sep 17 00:00:00 2001
From: Elias Carotti <eliascrt _at_ amazon _dot_ it>
Date: Tue, 20 Jun 2023 19:29:08 +0200
Subject: [PATCH 2/2] lavc/libx264: add mb_info option

Pass the information about unchanged parts of the frame by means of the
AVVideoHint side data.
---
 Changelog            |  1 +
 doc/APIchanges       |  3 ++
 libavcodec/libx264.c | 91 ++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/version.h |  2 +-
 4 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/Changelog b/Changelog
index 9cf3df8d6f..ec1b848b04 100644
--- a/Changelog
+++ b/Changelog
@@ -21,6 +21,7 @@  version <next>:
 - Essential Video Coding frame merge bsf
 - bwdif_cuda filter
 - Microsoft RLE video encoder
+- support for the P_SKIP hinting to speed up libx264 encoding

 version 6.0:
 - Radiance HDR image support
diff --git a/doc/APIchanges b/doc/APIchanges
index bfe04556d2..02723f5db7 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,9 @@  The last version increases of all libraries were on 2023-02-09

 API changes, most recent first:

+2023-06-21 - xxxxxxxxxx - lavc 60.22.100 - libx264.c
+  Add mb_info option.
+
 2023-06-21 - xxxxxxxxxx - lavu 58.14.100 - video_hint.h
   Add AVVideoHint API.

diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
index 5736f1efa7..c42e7ad39d 100644
--- a/libavcodec/libx264.c
+++ b/libavcodec/libx264.c
@@ -30,6 +30,7 @@ 
 #include "libavutil/stereo3d.h"
 #include "libavutil/time.h"
 #include "libavutil/intreadwrite.h"
+#include "libavutil/video_hint.h"
 #include "avcodec.h"
 #include "codec_internal.h"
 #include "encode.h"
@@ -48,6 +49,9 @@ 
 // from x264.h, for quant_offsets, Macroblocks are 16x16
 // blocks of pixels (with respect to the luma plane)
 #define MB_SIZE 16
+#define MB_LSIZE 4
+#define MB_FLOOR(x)      ((x) >> (MB_LSIZE))
+#define MB_CEIL(x)       MB_FLOOR((x) + (MB_SIZE - 1))

 typedef struct X264Opaque {
 #if FF_API_REORDERED_OPAQUE
@@ -123,6 +127,8 @@  typedef struct X264Context {
      * encounter a frame with ROI side data.
      */
     int roi_warned;
+
+    int mb_info;
 } X264Context;

 static void X264_log(void *p, int level, const char *fmt, va_list args)
@@ -295,6 +301,7 @@  static void free_picture(x264_picture_t *pic)
         av_free(pic->extra_sei.payloads[i].payload);
     av_freep(&pic->extra_sei.payloads);
     av_freep(&pic->prop.quant_offsets);
+    av_freep(&pic->prop.mb_info);
     pic->extra_sei.num_payloads = 0;
 }

@@ -320,6 +327,74 @@  static enum AVPixelFormat csp_to_pixfmt(int csp)
     return AV_PIX_FMT_NONE;
 }

+static void av_always_inline mbinfo_compute_changed_coords(const AVVideoRect *rect,
+                                                           int *min_x,
+                                                           int *max_x,
+                                                           int *min_y,
+                                                           int *max_y)
+{
+    *min_y = MB_FLOOR(rect->y);
+    *max_y = MB_CEIL(rect->y + rect->height);
+    *min_x = MB_FLOOR(rect->x);
+    *max_x = MB_CEIL(rect->x + rect->width);
+}
+
+static void av_always_inline mbinfo_compute_constant_coords(const AVVideoRect *rect,
+                                                            int *min_x,
+                                                            int *max_x,
+                                                            int *min_y,
+                                                            int *max_y)
+{
+    *min_y = MB_CEIL(rect->y);
+    *max_y = MB_FLOOR(rect->y + rect->height);
+    *min_x = MB_CEIL(rect->x);
+    *max_x = MB_FLOOR(rect->x + rect->width);
+}
+
+static int setup_mb_info(AVCodecContext *ctx, x264_picture_t *pic,
+                         const AVFrame *frame,
+                         const AVVideoHint *info)
+{
+    int mb_width = (frame->width + MB_SIZE - 1) / MB_SIZE;
+    int mb_height = (frame->height + MB_SIZE - 1) / MB_SIZE;
+
+    const AVVideoRect *mbinfo_rects;
+    int nb_rects;
+    uint8_t *mbinfo;
+
+    mbinfo_rects = (const AVVideoRect *)av_video_hint_rects(info);
+    nb_rects = info->nb_rects;
+
+    mbinfo = av_calloc(mb_width * mb_height, sizeof(*mbinfo));
+    if (!mbinfo)
+        return AVERROR(ENOMEM);
+
+#define COMPUTE_MBINFO(mbinfo_filler_, mbinfo_marker_, compute_coords_fn_) \
+    memset(mbinfo, mbinfo_filler_, sizeof(*mbinfo) * mb_width * mb_height); \
+                                                                        \
+    for (int i = 0; i < nb_rects; i++) {                                \
+        int min_x, max_x, min_y, max_y;                                 \
+                                                                        \
+        compute_coords_fn_(mbinfo_rects, &min_x, &max_x, &min_y, &max_y); \
+        for (int mb_y = min_y; mb_y < max_y; ++mb_y) {                  \
+            memset(mbinfo + mb_y * mb_width + min_x, mbinfo_marker_, max_x - min_x); \
+        }                                                               \
+                                                                        \
+        mbinfo_rects++;                                                 \
+    }                                                                   \
+
+    if (info->type == AV_VIDEO_HINT_CHANGED) {
+        COMPUTE_MBINFO(X264_MBINFO_CONSTANT, 0, mbinfo_compute_changed_coords);
+    } else /* if (info->type == AV_VIDEO_HINT_CHANGED) */ {
+        COMPUTE_MBINFO(0, X264_MBINFO_CONSTANT, mbinfo_compute_constant_coords);
+    }
+
+    pic->prop.mb_info = mbinfo;
+    pic->prop.mb_info_free = av_free;
+
+    return 0;
+}
+
 static int setup_roi(AVCodecContext *ctx, x264_picture_t *pic, int bit_depth,
                      const AVFrame *frame, const uint8_t *data, size_t size)
 {
@@ -404,6 +479,7 @@  static int setup_frame(AVCodecContext *ctx, const AVFrame *frame,
     int64_t wallclock = 0;
     int bit_depth, ret;
     AVFrameSideData *sd;
+    AVFrameSideData *mbinfo_sd;

     *ppic = NULL;
     if (!frame)
@@ -499,6 +575,17 @@  FF_ENABLE_DEPRECATION_WARNINGS
             goto fail;
     }

+    mbinfo_sd = av_frame_get_side_data(frame, AV_FRAME_DATA_VIDEO_HINT);
+    if (mbinfo_sd) {
+        int ret = setup_mb_info(ctx, pic, frame, (const AVVideoHint *)mbinfo_sd->data);
+        if (ret < 0) {
+            /* No need to fail here, this is not fatal. We just proceed with no
+             * mb_info and log a message */
+
+            av_log(ctx, AV_LOG_WARNING, "setup_mb_info failed with error: %s\n", av_err2str(ret));
+        }
+    }
+
     if (x4->udu_sei) {
         for (int j = 0; j < frame->nb_side_data; j++) {
             AVFrameSideData *side_data = frame->side_data[j];
@@ -1102,6 +1189,9 @@  FF_ENABLE_DEPRECATION_WARNINGS
         }
     }

+    x4->params.analyse.b_mb_info = x4->mb_info;
+    x4->params.analyse.b_fast_pskip = 1;
+
     // update AVCodecContext with x264 parameters
     avctx->has_b_frames = x4->params.i_bframe ?
         x4->params.i_bframe_pyramid ? 2 : 1 : 0;
@@ -1311,6 +1401,7 @@  static const AVOption options[] = {
     { "noise_reduction", "Noise reduction",                               OFFSET(noise_reduction), AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX, VE },
     { "udu_sei",      "Use user data unregistered SEI if available",      OFFSET(udu_sei),  AV_OPT_TYPE_BOOL,   { .i64 = 0 }, 0, 1, VE },
     { "x264-params",  "Override the x264 configuration using a :-separated list of key=value parameters", OFFSET(x264_params), AV_OPT_TYPE_DICT, { 0 }, 0, 0, VE },
+    { "mb_info",      "Set mb_info data through AVSideData, only useful when used from the API", OFFSET(mb_info), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, VE },
     { NULL },
 };

diff --git a/libavcodec/version.h b/libavcodec/version.h
index da6f3a84ac..9411511e04 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@ 

 #include "version_major.h"

-#define LIBAVCODEC_VERSION_MINOR  21
+#define LIBAVCODEC_VERSION_MINOR  22
 #define LIBAVCODEC_VERSION_MICRO 100

 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
--
2.34.1