[FFmpeg-devel] [PATCH v3] avcodec/h264: fixed qp table attach for h264

[Timothee <timothee.informatique@regaud-chapuy.fr>]

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Context from the first version :

> 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`

Andreas :
> 1. Commits should be small atomic units; changes to different libraries
> in the same commit are almost always not of this type.
> 2. Both ff_h264_decode_mb_cabac() and ff_h264_decode_mb_cavlc() already
> set qscale_table on their own (on success), so that all the changes to
> h264_slice.c seem completely redundant.
>
> - Andreas

Here is a new version of the patch without the redundant lines.

Thanks,

Timothée

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From 422e8dbdc3d79b24c6ccb11b7f384fc08406ee74 Mon Sep 17 00:00:00 2001
From: Timothee <timothee.informatique@regaud-chapuy.fr>
Date: Fri, 13 Jun 2025 14:21:28 +0200
Subject: [PATCH] avcodec/h264: fixed qp table attach for h264

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/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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