[FFmpeg-devel] [PATCH 1/2] avcodec/mlp_parser: don't try to combine frames when full frames are provided

[wm4]

On Fri, 19 Jan 2018 20:30:59 -0300
James Almer <jamrial at gmail.com> wrote:

> On 1/19/2018 5:06 PM, wm4 wrote:
> > On Fri, 19 Jan 2018 16:51:45 -0300
> > James Almer <jamrial at gmail.com> wrote:
> >   
> >> Attempting full frame reconstruction is unnecessary for containers
> >> like Matroska, so just skip it altogether.
> >>
> >> Signed-off-by: James Almer <jamrial at gmail.com>
> >> ---
> >>  libavcodec/mlp_parser.c | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/libavcodec/mlp_parser.c b/libavcodec/mlp_parser.c
> >> index 3c0330f777..4827354f18 100644
> >> --- a/libavcodec/mlp_parser.c
> >> +++ b/libavcodec/mlp_parser.c
> >> @@ -256,6 +256,9 @@ static int mlp_parse(AVCodecParserContext *s,
> >>      if (buf_size == 0)
> >>          return 0;
> >>  
> >> +    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
> >> +        next = buf_size;
> >> +    } else {
> >>      if (!mp->in_sync) {
> >>          // Not in sync - find a major sync header
> >>  
> >> @@ -315,6 +318,7 @@ static int mlp_parse(AVCodecParserContext *s,
> >>      }
> >>  
> >>      mp->bytes_left = 0;
> >> +    }
> >>  
> >>      sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
> >>    
> > 
> > Not so sure about this. I think some mkv TrueHD files contain packets
> > that are not properly starting on frame boundaries. But I don't really
> > remember.  
> 
> As in badly muxed files? Couldn't the same thing happen with any other
> codec? We're not bothering to consider such cases in other parses as far
> as i could see.

From my hazy memory, this also happened with mp3, although the Matroska
demuxer explicitly forces full parsing for that codec.