[FFmpeg-user] Dolby E decoder

[Mike Brown]

On Fri, Sep 08, 2017 at 09:34:50AM +0200, Paul B Mahol wrote:
> On 9/8/17, Mike Brown <brown at mrvideo.vidiot.com> wrote:
> > On Fri, Sep 08, 2017 at 12:54:12AM +0200, Carl Eugen Hoyos wrote:
> >> (Sorry, my knowledge of SMPTE 337M is limited but I know that so far,
> >> this is the only "format" for which FFmpeg supports Dolby-E, and that
> >> adding support for other formats will be possible but hasn't been
> >> done yet.)
> >
> > From what I understand, reading the synopsis of SMPTE-337M, is that it is
> > not a container specifically for Dolby-E.  I couldn't anything out of it to
> > indicate that it can even handle Dolby-E.
> >
> > That said, I do deal with SMPTE-302M, which is the spec for which Dolby-E is
> > applied to Transport Streams.  In my case satellite feeds (not for the
> > consumer).  The spec talks about MPEG-2 TS streams, but it applies to H.264
> > streams as well.
> >
> > Right now, I use ffmpeg to extract the stream into a 2-ch WAVE file, in
> > which
> > I use in another program to extract the audio into 6 mono WAVE files.  I
> > then
> > use ffmpeg to encode a AC3 file.
> >
> > Are you saying that I can use ffmpeg and get to a final ac3 file in a single
> > step?
> 
> No, you would need to copy audio to raw container, this raw container would be
> then detected as Dolby-E.
> 
> ffmpeg -i input.wav -c:a copy -f u8 out.u8
> 
> ffmpeg -i out.u8 -c:a ac3 .....

Could this not be done as a series of pipes:

ffmpeg -i input.ts -map 0:2 -c:a pcm_s24le -f wav - | \
ffmpeg -i - -c:a copy -f u24le - | \
ffmpeg -drc_scale 0 -i - -c:a ac3 -ab 640k -center_mixlev 0.707 output.ac3

Will the 5.1 audio be mapped correctly?

The Dolby-E is 24bit, not 8.

MB
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