[FFmpeg-user] How to extract core DTS / DCA stream from a DTS 96/24 stream without re-encoding

[Moritz Barsnick]

On Sat, May 19, 2018 at 14:21:47 +0100, Onetel wrote:

> I tried that as well but the output is just a duplicate of the DTS
> 96/24 stream, and has the same low volume problem as the original
> stream:

That's interesting. I found a different sample, and ffmpeg indeed isn't
capable of "reducing" it.

I was in doubt whether 96/24 was an extension, but at least Wikipedia
confirms:
"DTS 96/24 is implemented as a core DTS stream plus an extension
containing the deltas to enable 96/24 sound reproduction." I'm not sure
that means that the extensions need to be there, or whether they are
optional.

If there are extensions in there, there seems to be a shortcoming in
ffmpeg's dca_core bitstream filter.

BTW, if you use ffmpeg's decoder (and thereby re-encode, of course), it
does have the option:
  -core_only         <boolean>    .D..A.... Decode core only without extensions (default false)

I haven't checked whether that works though...

Cheers,
Moritz