Re: [FFmpeg-devel] [PATCH] flvdec: fix size desync when reading timestamp offsets

[Timo Rothenpieler <timo@rothenpieler.org>]

On 25.07.2023 01:41, Hendrik Leppkes wrote:
> The size offset was previously being accounted for in flv_set_video_codec
> for h264 and mpeg4, instead of being directly accounted for in the spot
> where its read, which desynced on HEVC streams.
> 
> For clarity, move the size offset directly to the parsing, similar to
> how its done for all other header fields.
> ---
>   libavformat/flvdec.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
> index a6a94a4021..3fe21622f7 100644
> --- a/libavformat/flvdec.c
> +++ b/libavformat/flvdec.c
> @@ -407,11 +407,9 @@ static int flv_set_video_codec(AVFormatContext *s, AVStream *vstream,
>       case FLV_CODECID_H264:
>           par->codec_id = AV_CODEC_ID_H264;
>           vstreami->need_parsing = AVSTREAM_PARSE_HEADERS;
> -        ret = 3;     // not 4, reading packet type will consume one byte
>           break;
>       case FLV_CODECID_MPEG4:
>           par->codec_id = AV_CODEC_ID_MPEG4;
> -        ret = 3;
>           break;
>       default:
>           avpriv_request_sample(s, "Video codec (%x)", flv_codecid);
> @@ -1321,6 +1319,7 @@ retry_duration:
>                          "invalid timestamps %"PRId64" %"PRId64"\n", dts, pts);
>                   dts = pts = AV_NOPTS_VALUE;
>               }
> +            size -= 3;
>           }
>           if (type == 0 && (!st->codecpar->extradata || st->codecpar->codec_id == AV_CODEC_ID_AAC ||
>               st->codecpar->codec_id == AV_CODEC_ID_H264 || st->codecpar->codec_id == AV_CODEC_ID_HEVC ||

tested with both h264 and hevc input, works fine
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