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avformat/demux: ensure avformat_find_stream_info updates internal stream contexts

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read_frame_internal() may result in a stream being modified without also
returning a packet from it. Given said function only bothered to update the
internal stream context for the returned packet, the result would be a desync
between the stream's AVCodecParameters and the internal AVCodecContext.

This change makes sure all streams are updated within the
avformat_find_stream_info() loop.

Fixes #YWH-PGM40646-20

Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit c9c95f6f32)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
James Almer 2025-12-16 19:20:40 -03:00 • committed by Michael Niedermayer
parent 5b3ca5240c
commit 246c55de06
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1 changed files with 17 additions and 0 deletions
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17
libavformat/demux.c
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@ -186,6 +186,8 @@ static int init_input(AVFormatContext *s, const char *filename,
s, 0, s->format_probesize);
}
static int codec_close(FFStream *sti);
static int update_stream_avctx(AVFormatContext *s)
{
int ret;
@ -196,6 +198,14 @@ static int update_stream_avctx(AVFormatContext *s)
if (!sti->need_context_update)
continue;
if (avcodec_is_open(sti->avctx)) {
av_log(s, AV_LOG_DEBUG, "Demuxer context update while decoder is open, closing and trying to re-open\n");
ret = codec_close(sti);
sti->info->found_decoder = 0;
if (ret < 0)
return ret;
}
/* close parser, because it depends on the codec */
if (sti->parser && sti->avctx->codec_id != st->codecpar->codec_id) {
av_parser_close(sti->parser);
@ -2641,6 +2651,13 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
break;
}
/* read_frame_internal() in a previous iteration of this loop may
* have made changes to streams without returning a packet for them.
* Handle that here. */
ret = update_stream_avctx(ic);
if (ret < 0)
goto unref_then_goto_end;
/* check if one codec still needs to be handled */
for (i = 0; i < ic->nb_streams; i++) {
AVStream *const st = ic->streams[i];