[FFmpeg-devel] [PATCH 2/3] avformat: Support s337m in mxf/wav/w64

[Carl Eugen Hoyos]

Am Di., 30. Juli 2019 um 21:04 Uhr schrieb Tomas Härdin <tjoppen at acc.umu.se>:
>
> tis 2019-07-30 klockan 15:24 +0200 skrev Carl Eugen Hoyos:
> >
> >
> > > Am 30.07.2019 um 14:02 schrieb Tomas Härdin <tjoppen at acc.umu.se>:
> > >
> > > fre 2019-07-26 klockan 18:45 +0200 skrev Nicolas Gaullier:
> > >
> > > > diff --git a/libavformat/wavdec.c b/libavformat/wavdec.c
> > > > index 52194f54ef..501c21f220 100644
> > > > --- a/libavformat/wavdec.c
> > > > +++ b/libavformat/wavdec.c
> > > > @@ -41,6 +41,7 @@
> > > > #include "riff.h"
> > > > #include "w64.h"
> > > > #include "spdif.h"
> > > > +#include "s337m.h"
> > > >
> > > > typedef struct WAVDemuxContext {
> > > >     const AVClass *class;
> > > > @@ -593,6 +594,8 @@ break_loop:
> > > >     } else if (st->codecpar->codec_id == AV_CODEC_ID_ADPCM_MS &&
> > > > st-
> > > > > codecpar->channels > 2) {
> > > >         st->codecpar->block_align *= st->codecpar->channels;
> > > >     }
> > > > +    if (s->dolby_e_probe)
> > > > +        s337m_probe_stream(s, &st);
> > >
> > > The same goes here - these codecs should have corresponding TwoCCs.
> >
> > There is definitely no TwoCCs for these kind of files, same as for
> > DTS and AC-3. (I don't know about Dolby E in mxf.)
>
> MXF has a UL registered for Dolby-E:
> urn:smpte:ul:060e2b34.04010101.04020202.03021c00
> We should continue to reject files that don't use it

Imo, we should auto-detect as much as possible as it was done in
FFmpeg for the last decade.

> > A probe function is definitely needed, it maybe should be more
> > similar to existing lavfi probe functions though.
>
> It's easy enough to probe this in .wav since it only involved reading a
> few bytes from the data chunk, even if a proper TwoCC would be highly
> preferable.

There is no TwoCC.

> Both these situation could be handled by avformat_find_stream_info() if
> there's some way to detect that a file is using AES3 in advance, and
> delay setting codec_id until the first audio packet has been inspected

First step is a demuxer, wav can then use the probe function.

Carl Eugen