[FFmpeg-devel] [PATCH 7/8] avformat/mpegtsenc: add registration descriptor for AC-3 and EAC3

[lance.lmwang at gmail.com]

On Sun, Aug 23, 2020 at 03:04:10PM +0200, Marton Balint wrote:
> 
> 
> On Sun, 23 Aug 2020, lance.lmwang at gmail.com wrote:
> 
> > On Sun, Aug 23, 2020 at 10:17:01AM +0200, Marton Balint wrote:
> > > 
> > > 
> > > On Sun, 23 Aug 2020, lance.lmwang at gmail.com wrote:
> > > 
> > > > On Sat, Aug 22, 2020 at 07:27:30PM +0200, Marton Balint wrote:
> > > > > > > > > On Sat, 22 Aug 2020, lance.lmwang at gmail.com wrote:
> > > > > > > > On Wed, Jul 22, 2020 at 11:27:38PM +0800,
> > > lance.lmwang at gmail.com wrote:
> > > > > > > From: Limin Wang <lance.lmwang at gmail.com>
> > > > > > > > > copy the atsc ac3 audio in ts like below:
> > > > > > > ./ffmpeg -i atsc_audio.ts -c:v copy -c:a copy out.ts
> > > > > > > Stream #0:6[0x64](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 192 kb/s
> > > > > > > > > ./ffmpeg -i out.ts
> > > > > > > Before:
> > > > > > > Stream #0:1[0x101](eng): Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, stereo, fltp, 192 kb/s
> > > > > > > > > After applied patch:
> > > > > > > Stream #0:1[0x101](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 192 kb/s
> > > > > > > > > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > > > > > > ---
> > > > > > >  libavformat/mpegtsenc.c | 5 +++++
> > > > > > >  1 file changed, 5 insertions(+)
> > > > > > > > > diff --git a/libavformat/mpegtsenc.c
> > > > > b/libavformat/mpegtsenc.c
> > > > > > > index a5b45fb..f060ea6 100644
> > > > > > > --- a/libavformat/mpegtsenc.c
> > > > > > > +++ b/libavformat/mpegtsenc.c
> > > > > > > @@ -535,6 +535,11 @@ static int mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
> > > > > > >                      *q++=1; // 1 byte, all flags sets to 0
> > > > > > >                      *q++=0; // omit all fields...
> > > > > > >                  }
> > > > > > > +            } else {
> > > > > > > +                if (codec_id == AV_CODEC_ID_AC3)
> > > > > > > +                    put_registration_descriptor(&q, MKTAG('A', 'C', '-', '3'));
> > > > > > > +                else if (codec_id == AV_CODEC_ID_EAC3)
> > > > > > > +                    put_registration_descriptor(&q, MKTAG('E', 'A', 'C', '3'));
> > > > > > >              }
> > > > > > >              if (codec_id == AV_CODEC_ID_S302M)
> > > > > > >                  put_registration_descriptor(&q, MKTAG('B', 'S', 'S', 'D'));
> > > > > > > -- > > 1.8.3.1
> > > > > > > > > ping the patch, as I'll submit patch to support atsc ac3
> > > > > descriptor after that.
> > > > > > > Why is this patch needed?
> > > > > > >
> > > https://www.atsc.org/wp-content/uploads/2015/03/A52-2018-1.pdf
> > > > > > > does not seem to require the use of MPEG2 registration
> > > descriptor for ATSC.
> > > > > > > I am not saying this is patch is bad, but some valid reason
> > > should be found
> > > > > to justify it, and the fact that AC3 fourcc is reported is irrelevant, that
> > > > > is just fourcc, it can be anything.
> > > > > Most of my atsc ac3 sample write the mpeg2 descriptor, so I want
> > > to keep it when copy
> > > > the audio stream.
> > > 
> > > There are system B samples out there which also has the descriptor. So why
> > > not write it to system B as well by that reasoning?
> > 
> > Where to download such samples, most of my system sample don't write the
> > mpeg2 descriptor, that's why I haven't add it for system B.
> 
> A lot of samples are in http://samples.ffmpeg.org:
> 
> MPEG2/subcc/HK_DVB_w_subtitle.ts
> MPEG2/subcc/HK_DVB_sample.ts
> ffmpeg-bugs/trac/ticket2086/teletextsubtitles.ts
> ffmpeg-bugs/trac/ticket5453/vlc_cut.ts
> ffmpeg-bugs/trac/ticket2838/BDAV recorded video sample.ts
> samples/ffmpeg-bugs/trac/ticket3186/Lilyhammer_sample.ts
> samples/ffmpeg-bugs/trac/ticket5453/vlc_cut.ts
> ffmpeg-bugs/trac/ticket4469/Kodi-Reports-Error-with-DVB-Multilanguage-Subtitles.ts
> ffmpeg-bugs/roundup/issue1294/hd_from_ksng_090726b.ts
> V-codecs/h264/PAFF/Grey.ts
> 
> These should all be 25 fps, so most likely not ATSC...
> The Hungarian DVB-T broadcaster also uses the descriptor.

OK, I'll update to add the descriptor for both system B and ATSC.

> 
> Regards,
> Marton
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-- 
Thanks,
Limin Wang