[CELT-dev] Stereo <-> Mono
Timothy B. Terriberry
tterribe at xiph.org
Wed Jan 12 10:12:21 PST 2011
> Does Celt (in particular version 0.7.1) exploits correlation between the
> two channels in stereo mode?
> In practice, is it possible to use the two channels as two mono signals
> without affecting quality?
CELT does indeed use a variant of mid-side stereo to exploit correlation
between channels. Version 0.7.1 in particular did not switch to
intensity mode in the higher bands, so it should not be _terrible_ if
fed two mono signals, but a) you won't get much, if any, savings in
bitrate compared to using two independent streams if things really are
uncorrelated, and b) in all cases CELT decides whether or not to use
short blocks on a frame-by-frame basis, so there will definitely be some
quality loss if the transients do not appear in the same place.
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