[FFmpeg-devel] [PATCH v7 3/3] avcodec/mpeg12dec: Add CPB coded side data

[Michael Niedermayer]

On Thu, Feb 20, 2020 at 11:22:33AM +0000, Gaullier Nicolas wrote:
> > De : ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> De la part de Michael Niedermayer
> > Envoyé : vendredi 7 février 2020 23:39
> > À : FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> > Objet : Re: [FFmpeg-devel] [PATCH v7 3/3] avcodec/mpeg12dec: Add CPB coded side data
> > 
> > On Wed, Jan 15, 2020 at 12:42:13AM +0100, Nicolas Gaullier wrote:
> > > This fixes mpeg2video stream copies to mpeg muxer like this:
> > >   ffmpeg -i xdcamhd.mxf -c:v copy output.mpg
> > > ---
> > >  libavcodec/mpeg12dec.c       | 7 +++++++
> > >  tests/ref/fate/mxf-probe-d10 | 3 +++
> > >  tests/ref/fate/ts-demux      | 2 +-
> > >  3 files changed, 11 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c index
> > > 17f9495a1d..48ac14fafa 100644
> > > --- a/libavcodec/mpeg12dec.c
> > > +++ b/libavcodec/mpeg12dec.c
> > > @@ -1398,6 +1398,7 @@ static void mpeg_decode_sequence_extension(Mpeg1Context *s1)
> > >      MpegEncContext *s = &s1->mpeg_enc_ctx;
> > >      int horiz_size_ext, vert_size_ext;
> > >      int bit_rate_ext;
> > > +    AVCPBProperties *cpb_props;
> > >
> > >      skip_bits(&s->gb, 1); /* profile and level esc*/
> > >      s->avctx->profile       = get_bits(&s->gb, 3);
> > > @@ -1429,6 +1430,12 @@ static void mpeg_decode_sequence_extension(Mpeg1Context *s1)
> > >      ff_dlog(s->avctx, "sequence extension\n");
> > >      s->codec_id = s->avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
> > >
> > > +    if (cpb_props = ff_add_cpb_side_data(s->avctx)) {
> > > +        cpb_props->buffer_size = FFMAX(cpb_props->buffer_size, s->avctx->rc_buffer_size);
> > > +        if (s->bit_rate != 0x3FFFF*400)
> > > +            cpb_props->max_bitrate = FFMAX(cpb_props->max_bitrate, s->bit_rate);
> > > +    }
> > 
> > why does this not export exactly the numbers as read from the header?
> > 
> > thx
> The header values are expressed in units of 400bit/s, and the native value 0x3FFFF is reserved, in case of MPEG-1 (but the code is shared), for vbr signalling.
> This is not very nice to read, but this is how it is implemented in current code.

you misunderstand, why do you take the maximum of several things instead of
exporting the value from the header ?

Thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

"I am not trying to be anyone's saviour, I'm trying to think about the
 future and not be sad" - Elon Musk

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20200221/cfd8e7bb/attachment.sig>