[FFmpeg-devel] [PATCH] mp3enc: Fix Xing tag identification string for CBR files

[Tobias Rapp]

Michael Niedermayer wrote:
> > diff --git a/libavformat/mp3enc.c b/libavformat/mp3enc.c
> > index 29c0780..cb61e37 100644
> > --- a/libavformat/mp3enc.c
> > +++ b/libavformat/mp3enc.c
> > @@ -180,7 +180,11 @@ static int mp3_write_xing(AVFormatContext *s)
> >  
> >      avio_wb32(s->pb, header);
> >      ffio_fill(s->pb, 0, xing_offset);
> > -    avio_wb32(s->pb, MKBETAG('X', 'i', 'n', 'g'));
> > +    /* use "Xing" identification string for VBR files and "Info" for CBR */
> > +    if (codec->flags & CODEC_FLAG_QSCALE) 
> 
> This is problematic as this flag will only be set reliable on encoding
> but not on transcoding (-acodec copy)
> 
> better would be to update the tag in mp3_fix_xing() at the end
> after storing all packets if they all "match"/dont "match" in size

Good catch. Have reworked the patch to look at all the packet headers and
decide for CBR/VBR.

Regards,
Tobias
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