[alsa-devel] Controling wave amplitude using alsa api !! (pcm interface ???????)

John L. Utz III jutz at dmx.com
Tue Aug 4 19:08:12 CEST 2009

Guilherme Longo wrote:
> Hi all!
> Mates, I am following the example PCM.C that I found at alsa web site. 
> its a sine wave generator.
> I am looking for a control that alsa provides to control the amplitude 
> of the wave.
> As I could found so for, there is just frequency control... I didn't 
> find any amplitude control.

This line int pcm.c is not amplitude control?

unsigned int maxval = (1 << (snd_pcm_format_width(format) - 1)) - 1;

it's an int, so you probably need to alter this a bit to allow you to
have arbitrary control over the amplitude (ie: multiply by a float less
than 1.0)



> * I don't want to control the volume using alsamixer or even my sound... 
> I want to generate a wave with predefined amplitude.
> Does anyone could give me a little help??
> Thanks a lot!
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