[vorbis-dev] patents and separate entropy coding

Monty xiphmont at xiph.org
Fri Dec 15 12:37:58 PST 2000

> 	Claim # 10
> 	10. A coding process according to claim 9, further comprising the
> steps of: 
> 	utilizing different code tables for different spectral ranges; and 
> 	setting borders between the different spectral ranges dependent upon
> the signal. 
> Since Vorbis does not separate the frequency ranges via a filter bank, it
> cannot use "different code tables for different spectral ranges".  Right?

It does not do it in the transform stage, but multiple ranges, for the
sake of vector classification, can be done later.  Vorbis can
subdivide the spectrum into arbitrary partitions and choose, in each
frame, different codebooks for any of them.  So, we implement a system
that does in fact work out to be a superset of this claim.  (However,
this patent is already inapplicable due to other claims, and if it
weren't, would apply equally to TwinVQ/VQF and several others).


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