[FFmpeg-devel] [PATCH] avcodec/h264_slice: don't force ff_get_format unconditionally after flush (PR #20921)

[Zhao Zhili via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20921 opened by Zhao Zhili (quink)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20921
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20921.patch

h->context_initialized is zero after flush, which triggers call to
ff_get_format unconditionally. ff_get_format can be heavy with
ff_hwaccel_uninit and hwaccel_init. For example, it takes 20 ms on
macOS with videotoolbox. ff_get_format should not be called if
nothing changed. ff_get_format is guarantee to be called at the
first time and when video information changed with
(must_reinit || needs_reinit).

Fix #20760.


>From 239f14c80fa93587dbb2681ae0a5dfb670a24e93 Mon Sep 17 00:00:00 2001
From: Zhao Zhili <zhilizhao@tencent.com>
Date: Fri, 14 Nov 2025 23:46:04 +0800
Subject: [PATCH] avcodec/h264_slice: don't force ff_get_format unconditionally
 after flush

h->context_initialized is zero after flush, which triggers call to
ff_get_format unconditionally. ff_get_format can be heavy with
ff_hwaccel_uninit and hwaccel_init. For example, it takes 20 ms on
macOS with videotoolbox. ff_get_format should not be called if
nothing changed. ff_get_format is guarantee to be called at the
first time and when video information changed with
(must_reinit || needs_reinit).

Fix #20760.
---
 libavcodec/h264_slice.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index 7e53e38cca..4bce9b9228 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -1150,7 +1150,7 @@ static int h264_init_ps(H264Context *h, const H264SliceContext *sl, int first_sl
         if (flush_changes)
             ff_h264_flush_change(h);
 
-        if ((ret = get_pixel_format(h, 1)) < 0)
+        if ((ret = get_pixel_format(h, must_reinit || needs_reinit)) < 0)
             return ret;
         h->avctx->pix_fmt = ret;
 
-- 
2.49.1

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