Re: [FFmpeg-devel] [PATCH] avfilter/codecview: Enable QP visualization for H.264

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

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Context from the first version : Subject was "avcodec/h264: fixed qp table attach for h264"


> 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`

Here is the new version of the patch.

I have remove the unnecessary line in qp_table.h and changed the commit 
message.

Timothee

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From 74b3fc3cc9f10a9483b3ca1c838d69fe4cb6c3ba Mon Sep 17 00:00:00 2001
From: Timothee <timothee.informatique@regaud-chapuy.fr>
Date: Thu, 19 Jun 2025 11:23:45 +0200
Subject: [PATCH] avfilter/codecview: Enable QP visualization for H.264

The codecviewfilter, when used with qp=1, did not display quantization parameter values for H.264 streams because the QP table extraction was restricted to MPEG-2 video.

This patch enables H.264 support by updating ff_qp_table_extractto accept AV_VIDEO_ENC_PARAMS_H264. This allows for correct QP overlay on H.264 video

Signed-off-by: Timothee <timothee.informatique@regaud-chapuy.fr>
---
 libavfilter/qp_table.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavfilter/qp_table.c b/libavfilter/qp_table.c
index 8137dc019f..abe46e810b 100644
--- a/libavfilter/qp_table.c
+++ b/libavfilter/qp_table.c
@@ -39,8 +39,9 @@ int ff_qp_table_extract(AVFrame *frame, int8_t **table, int *table_w, int *table
     sd = av_frame_get_side_data(frame, AV_FRAME_DATA_VIDEO_ENC_PARAMS);
     if (!sd)
         return 0;
-    par = (AVVideoEncParams*)sd->data;
-    if (par->type != AV_VIDEO_ENC_PARAMS_MPEG2 ||
+    par = (AVVideoEncParams *)sd->data;
+    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);
 
-- 
2.39.5


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