[Vorbis] Mono encoding w/ a stereo source.

[John Edwards]

Michael Smith wrote:
> On 11/16/05, Ian A. Underwood <agentgrn at dcne.net> wrote:
>> I'm not sure since this is what I got from Lou at SpacialAudio:
>>
>> "We do not merge the channels for the encoding - this is all done by
>> Ogg.  A simple method is usually to just add the left channel to the
>> right to get the mono channel.  Although this is the correct way
>> theoretically, in pratice it sounds too loud.  Thus I guess this is what
>> they are doing in the Ogg encoder."
> 
> What I said was a simple fact. Libvorbis has, internally, no
> capabilities to produce a mono encoding from anything other than a
> mono input. Libvorbis does not do downmixing ever, under any
> circumstances - there's simply no code there to do it.
> 
> So, either this person was confused, and gave you an incorrect answer,
> or perhaps they're using some third-party wrapper library around
> libvorbis that does the downmixing - in that latter case, they might
> not be aware that the wrapper library is doing the downmixing (from
> your report, apparently incorrectly), and not libvorbis.
> 
> Since we don't know anything about how they're using libvorbis, we
> can't really do more than what I've said above - which is just
> guessing.
> 
> Feel free to point the SpatialAudio people in my direction if they're
> still confused about this.
> 

Unless, of course, someone is using the reference encoder which does 
offer downmixing by adding the left and right channels and halving the 
result.

John