[CELT-dev] Surround Sound

Kip Warner kip at thevertigo.com
Tue Dec 28 17:19:22 PST 2010

On Tue, 2010-12-28 at 03:26 -0500, Gregory Maxwell wrote:
> Monty documented the process of adding coupling in a number of posts
> at http://people.xiph.org/~xiphmont/demo/ (under surround
> optimization). The pages also include a number of demo surround vorbis
> files.

This is great. The problem I suppose is that there are probably still no
receivers on the market that can decode a vorbis stream, but usually
only things like DTS or AC3. But that may change one day.

> > From what I know of the CELT codec, it handles either only mono or
> > stereo. Is that correct?
> Correct.
> In our (now defunct) RTP draft we specified a signaling and mapping
> scheme to setup surround using mono/stereo CELT instances[1].  It's
> been my intention to update our Ogg mapping for CELT to support the
> same, but I'm currently waiting on seeing how multichannel is signaled
> with Opus.
> [1] http://tools.ietf.org/html/draft-valin-celt-rtp-profile-01

It looks as though the mechanism is in place. One clarification that may
have already been made but that slipped my eyes, the mapping parameter
used for multichannel doesn't appear to specify a character encoding. I
am assuming these are null terminated 8-bit ASCII sequences, but if it
hasn't been explicitly mentioned already, it would probably not be a bad

Thanks Greg.

Kip Warner -- Software Engineer
OpenPGP encrypted/signed mail preferred
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