[vorbis-dev] Why LSP?

[Jean-Marc Valin]

(Disclaimer: this is not an LPC vs. LSP question)

After looking at the Vorbis code I was wondering why you were using LSP to
quantize the spectral envelope instead of simply quantizing the cepstrum
(DCT(log(envelope))) or modified cepstrum (DCT(envelope.^alpha)). To me it seems
like when the information is already in the frequency domain, there's no need to
go back to LPC. Also, I think a DCT can be faster that a Levinson-Durbin
recursion. This is why I'd like to know whether there's a special reason I'm not
aware of for quantizing the LSP.

        Jean-Marc


-- 
Jean-Marc Valin
Universite de Sherbrooke - Genie Electrique
valj01 at gel.usherb.ca

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