[FFmpeg-devel] [PATCH] flvdec: set need_context_update when changing codec id

[Michael Niedermayer]

On Thu, Nov 24, 2016 at 01:37:17AM +0100, Andreas Cadhalpun wrote:
> On 23.11.2016 03:26, Michael Niedermayer wrote:
> > On Fri, Nov 04, 2016 at 10:28:20PM +0100, Andreas Cadhalpun wrote:
> >> Otherwise the codec context and codecpar might disagree on the codec id,
> >> triggering asserts in av_parser_parse2.
> >>
> >> Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
> >> ---
> >>  libavformat/flvdec.c | 16 ++++++++++++----
> >>  1 file changed, 12 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
> >> index e53c345..4ba7fc8 100644
> >> --- a/libavformat/flvdec.c
> >> +++ b/libavformat/flvdec.c
> >> @@ -289,7 +289,9 @@ static int flv_same_video_codec(AVCodecParameters *vpar, int flags)
> >>  static int flv_set_video_codec(AVFormatContext *s, AVStream *vstream,
> >>                                 int flv_codecid, int read)
> >>  {
> >> +    int ret = 0;
> >>      AVCodecParameters *par = vstream->codecpar;
> >> +    enum AVCodecID old_codec_id = vstream->codecpar->codec_id;
> >>      switch (flv_codecid) {
> >>      case FLV_CODECID_H263:
> >>          par->codec_id = AV_CODEC_ID_FLV1;
> >> @@ -317,20 +319,26 @@ static int flv_set_video_codec(AVFormatContext *s, AVStream *vstream,
> >>              else
> >>                  avio_skip(s->pb, 1);
> >>          }
> >> -        return 1;     // 1 byte body size adjustment for flv_read_packet()
> >> +        ret = 1;     // 1 byte body size adjustment for flv_read_packet()
> >> +        break;
> >>      case FLV_CODECID_H264:
> >>          par->codec_id = AV_CODEC_ID_H264;
> >>          vstream->need_parsing = AVSTREAM_PARSE_HEADERS;
> >> -        return 3;     // not 4, reading packet type will consume one byte
> >> +        ret = 3;     // not 4, reading packet type will consume one byte
> >> +        break;
> >>      case FLV_CODECID_MPEG4:
> >>          par->codec_id = AV_CODEC_ID_MPEG4;
> >> -        return 3;
> >> +        ret = 3;
> >> +        break;
> >>      default:
> >>          avpriv_request_sample(s, "Video codec (%x)", flv_codecid);
> >>          par->codec_tag = flv_codecid;
> >>      }
> >>  
> >> -    return 0;
> >> +    if (par->codec_id != old_codec_id)
> >> +        vstream->internal->need_context_update = 1;
> > 
> > If this occurs only for fuzzed samples then rejecting the change
> > with a request for a sample seems better
> >
> > changing teh codec_id midstream like this could, seems problematic
> > changing at at header time might be ok if that works better than not
> > changing it for some real sample
> 
> This happens for almost every file, because at the beginning the codec_id
> is AV_CODEC_ID_NONE. However, usually need_context_update is already
> set from avformat_new_stream, so a change can be rejected, if this
> is not the case. Patch doing that attached.

the code i tested prviously checked for AV_CODEC_ID_NONE but this is
probably ok too

thx
8...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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