How to mix two PCM channels with ALSA

How to mix two PCM channels with ALSA

[itxEpsilon]

Dear Alsa developers:

I'm trying to write a simple application 
for mixing two PCM sound channels in
C++. Could anyone provide me a 
quick example about how to implement
this operation?

Thank you in advance.
Itx

Re: How to mix two PCM channels with ALSA

[Clemens Ladisch]

itxEpsilon wrote:
> I'm trying to write a simple application
> for mixing two PCM sound channels in
> C++. Could anyone provide me a
> quick example about how to implement
> this operation?

  outputSample[i] = inputChannel1[i] + inputChannel2[i];

What does this have to do with ALSA?


Regards,
Clemens

Re: How to mix two PCM channels with ALSA

[itxEpsilon]

Clemens Ladisch <clemens <at> ladisch.de> writes:

> 
> itxEpsilon wrote:
> > I'm trying to write a simple application
> > for mixing two PCM sound channels in
> > C++. Could anyone provide me a
> > quick example about how to implement
> > this operation?
> 
>   outputSample[i] = inputChannel1[i] + inputChannel2[i];
> 
> What does this have to do with ALSA?
> 
> Regards,
> Clemens
> 

Hi,
That's no my question, I'd like to know how is performed with the ALSA API.

i.e. 

playSound(buffer1);
playSound(buffer2);

is it implicitly mixed when playing two buffers by hardware?

Thanks.
Carlos.

Re: How to mix two PCM channels with ALSA

[Clemens Ladisch]

itxEpsilon wrote:
> I'd like to know how is performed with the ALSA API.
>
> playSound(buffer1);
> playSound(buffer2);
>
> is it implicitly mixed when playing two buffers by hardware?

Yes, if the hardware actually support this (nowadays, none does), or if
ALSA is configured to use software mixing through dmix or PulseAudio
(which are enabled by default in most distributions).


Regards,
Clemens