> De : ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> De la part de Michael
> Niedermayer
> Envoyé : vendredi 7 février 2020 23:39
> À : FFmpeg development discussions and patches <ffmpeg-devel@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.
Nicolas
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