[linux-audio-dev] jack_process and pitch-shifting

Olivier Guilyardi ml at xung.org
Sat Apr 23 06:23:09 EDT 2005

Erik de Castro Lopo wrote:

>Last time I looked, libsoundtouch used linear interpolation for
>doing vary speed. Linear interpolation is evil. Here is a table
>from a talk I presented a the audio minconf attached the LCA.
>Linear interpolation is simply no damn good unless you are *positive*
>the maximum frequency in your source material is less that 0.06 of
>the sample rate. For any real world signal, this is simply not the 
My guess was good, then, about libsamplerate providing better quality.

>Secondly, I think the pitch shifter in libsoundtouch works by doing
>time stretching first and then vary speed on top of that (someone
>please correct me if I am wrong). In this is the case, it might be
>possible to replace the second vary speed stage with the vary
>speed from libsamplerate.
Together with a Jackbeat user, we agreed that varying the speed is 
enough. We don't need (lo-fi) pitch-shifting. I'll stick with libsamplerate.

By the way, thanks for your work !


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