[Speex-dev] Speex Resampler quality

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Thu Feb 14 12:53:18 PST 2008

Premkiran Mannava a écrit :
> I just built a sample application with speex resampler in linux and I
> tried to resample 8K sine wave tone mono to 48k using
> speex_resample_process_int.  I am using a tool called EAQUAL for audio
> quality.  

That's in general not very reliable. You can get PEAQ to say all sorts
of silly things.

> I find the quality of Speex resampler to be decreasing when I
> increase the quality q of the resampler init function.  Can some one
> give me pointers regarding this?? 

I strongly suspect that it's just not compensating for the delay
introduced by the resampler. Because higher quality means higher delay,
you'd find that PEAQ doesn't like it when you increase the resampler
quality. You can easily remove the delay (well, not remove it but skip
the zeros it produces) by calling speex_resampler_skip_zeros() once,
before you start the processing.

> As per the API, if the quality factor
> is increased, it is assumed that the quality should increase which is no
> the way I observed with my console application

Did you actually *listen* to the result?

> Can some one give me pointers to any doc available on the algorithm of
> Speex resampler?

The resampler.c file (get a recent version) has all the info/links I
have on that algo.


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