opus - Jan 2011 - Stereo <-> Mono

Hi,
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?

Thanks

Best Regards
Riccardo 


Riccardo Micci
Senior DSP Engineer, Wireless Group 
Cambridge Consultants
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Cambridge, CB4 0DW, England
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riccardo.micci at cambridgeconsultants.com
www.CambridgeConsultants.com
 





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> 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.