[FFmpeg-devel] [PATCH] avcodec/h264: fixed qp table attach for h264

* [FFmpeg-devel] [PATCH] avcodec/h264: fixed qp table attach for h264
@ 2025-06-13 12:37 Timothee
  2025-06-13 20:52 ` Michael Niedermayer
  0 siblings, 1 reply; 2+ messages in thread
From: Timothee @ 2025-06-13 12:37 UTC (permalink / raw)
  To: ffmpeg-devel

Hello,

Here is a patch where I fixed the attach of per-macroblock qp tables for 
H.264. It was implemented for MPEG2 so I have only extended it.

I tested the functionality with the codecview filter using the following 
command: `./ffmpeg -export_side_data 4 -i input.mp4 -vf codecview=qp=1 
output.mp4`

FATE passes.

Thanks,
Timothée

Signed-off-by: Timothee <timothee.informatique@regaud-chapuy.fr>
---
  libavcodec/h264_slice.c | 16 ++++++++++++----
  libavfilter/qp_table.c  |  3 ++-
  libavfilter/qp_table.h  |  1 +
  3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index 7e53e38cca..f217c58837 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -2615,8 +2615,10 @@ static int decode_slice(struct AVCodecContext 
*avctx, void *arg)
               ret = ff_h264_decode_mb_cabac(h, sl);
  -            if (ret >= 0)
+            if (ret >= 0) {
                  ff_h264_hl_decode_mb(h, sl);
+                h->cur_pic.qscale_table[sl->mb_xy] = sl->qscale;
+            }
               // FIXME optimal? or let mb_decode decode 16x32 ?
              if (ret >= 0 && FRAME_MBAFF(h)) {
@@ -2624,8 +2626,10 @@ static int decode_slice(struct AVCodecContext 
*avctx, void *arg)
                   ret = ff_h264_decode_mb_cabac(h, sl);
  -                if (ret >= 0)
+                if (ret >= 0) {
                      ff_h264_hl_decode_mb(h, sl);
+                    h->cur_pic.qscale_table[sl->mb_xy] = sl->qscale;
+                }
                  sl->mb_y--;
              }
              eos = get_cabac_terminate(&sl->cabac);
@@ -2686,16 +2690,20 @@ static int decode_slice(struct AVCodecContext 
*avctx, void *arg)
               ret = ff_h264_decode_mb_cavlc(h, sl);
  -            if (ret >= 0)
+            if (ret >= 0) {
                  ff_h264_hl_decode_mb(h, sl);
+                h->cur_pic.qscale_table[sl->mb_xy] = sl->qscale;
+            }
               // FIXME optimal? or let mb_decode decode 16x32 ?
              if (ret >= 0 && FRAME_MBAFF(h)) {
                  sl->mb_y++;
                  ret = ff_h264_decode_mb_cavlc(h, sl);
  -                if (ret >= 0)
+                if (ret >= 0) {
                      ff_h264_hl_decode_mb(h, sl);
+                    h->cur_pic.qscale_table[sl->mb_xy] = sl->qscale;
+                }
                  sl->mb_y--;
              }
  diff --git a/libavfilter/qp_table.c b/libavfilter/qp_table.c
index 8137dc019f..a99b99e77a 100644
--- a/libavfilter/qp_table.c
+++ b/libavfilter/qp_table.c
@@ -40,7 +40,8 @@ int ff_qp_table_extract(AVFrame *frame, int8_t 
**table, int *table_w, int *table
      if (!sd)
          return 0;
      par = (AVVideoEncParams*)sd->data;
-    if (par->type != AV_VIDEO_ENC_PARAMS_MPEG2 ||
+    if ((par->type != AV_VIDEO_ENC_PARAMS_MPEG2
+       && par->type != AV_VIDEO_ENC_PARAMS_H264) ||
          (par->nb_blocks != 0 && par->nb_blocks != nb_mb))
          return AVERROR(ENOSYS);
  diff --git a/libavfilter/qp_table.h b/libavfilter/qp_table.h
index 4407bacb0e..c1a80d1830 100644
--- a/libavfilter/qp_table.h
+++ b/libavfilter/qp_table.h
@@ -40,6 +40,7 @@ static inline int ff_norm_qscale(int qscale, enum 
AVVideoEncParamsType type)
  {
      switch (type) {
      case AV_VIDEO_ENC_PARAMS_MPEG2: return qscale >> 1;
+    case AV_VIDEO_ENC_PARAMS_H264:  return qscale;
      }
      return qscale;
  }
-- 
2.39.5

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