[FFmpeg-user] Dolby E decoder

[Paul B Mahol]

On 9/8/17, Mike Brown <brown at mrvideo.vidiot.com> wrote:
> 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.

Doesn't matter, your example will not work, try it.