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

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

[Hendrik Leppkes]

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 ||
-- 
2.40.1.windows.1

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

[Timo Rothenpieler]

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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