[Speex-dev] Differences between ACELP and CELP.... Reloaded

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Fri Mar 11 11:59:10 PST 2005


The A in ACELP stands for algebraic. It means that the fixed codebook
(cb_search.c) is not "real" codebook (as contained in the *table.c
files), but rather an algebraic (implicit) one, where each entry can be
computed directly from the codebook index. The main advantage of ACELP
lies in the fact that the search is much faster, which allows larger
codebook for the same complexity. 

In terms of Speex, implementing ACELP would mean replacing cb_search.c
and most likely changing a bit how the fixed codebook gain is
implemented too. Not that I would recommend it anyway, but since you


Le lundi 07 mars 2005 à 18:10 +0000, John Villar a écrit :
> And the main point of interest is the following: how much difference in 
> SPEEX terms would it be if it were developed with ACELP in mind? (not 
> that i would do an aSpeex codec implementing ACELP, just to know and 
> point my efforts)
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Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
Université de Sherbrooke

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