PR #21224 opened by James Almer (jamrial) URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21224 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21224.patch
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 This PR supersedes #21215. >From 27fa209cf5f2b995828926e863ce11f1e531881f Mon Sep 17 00:00:00 2001 From: James Almer <[email protected]> Date: Tue, 16 Dec 2025 19:20:40 -0300 Subject: [PATCH] avformat/demux: ensure avformat_find_stream_info updates internal stream contexts 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 <[email protected]> --- libavformat/demux.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/libavformat/demux.c b/libavformat/demux.c index 934eb80553..b1918d2110 100644 --- a/libavformat/demux.c +++ b/libavformat/demux.c @@ -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); @@ -2682,6 +2692,13 @@ 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]; -- 2.49.1 _______________________________________________ ffmpeg-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
