ossaudiodev problem: sawtooth noise

Gabriel Genellina gagsl-py2 at yahoo.com.ar
Thu Jan 22 23:58:14 CET 2009

En Mon, 19 Jan 2009 21:57:04 -0200, Peter Pearson  
<ppearson at nowhere.invalid> escribió:

> The following code uses ossaudiodev to read 1000 values from
> my sound card at a rate of 12,000 samples per second:
> When I select a sample rate that is not a power of 2 times
> 3000 samples/second, a strong and very regular sawtooth is
> superimposed on the signal.  At some sampling frequencies,
> it appears as a rising sawtooth, and at other sampling
> frequencies it is a declining sawtooth, so I'm presumably
> lost in some aliasing wilderness.  As best I can tell,
> it's a 48 KHz sawtooth.

That could be a hardware and/or driver limitation. By example, an  
AC97-compliant chipset may provide a fixed rate of 48000 samples/second --  
any sample rate conversion must be done by other means, if possible at all.

Gabriel Genellina

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