[speex-dev] Complexity vs BitRate

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Thu May 6 22:59:54 PDT 2004

> 1. Does the complexity setting override the quality setting, or does
> increasing the complexity only lower the rate at a given quality?
> Or would setting both higher increase the quality more?

Complexity is completely orthogonal. You have VBR that selects the
bit-rate necessary for each frame and then all complexity does is that
for a certain bit-rate it can *slightly* increase/decrease quality
depending on how much CPU you're willing to put (quality 3 is usually
good for most purposes).

> 2. What sort of impact would setting quality as high as
> possible have on the data rate?  Is there a theoretical upper bound
> on the VBR data rate (assuming no ABR average rate was set?).

The highest bit-rate you can get with VBR is simply the highest CBR
bit-rate, so 24.6 kbps for narrowband. Of course, the bit-rate will
usually be lower.


Jean-Marc Valin
Université de Sherbrooke, Québec, Canada

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