Re: [Alsa-user] Read and write with different output sizes

[Elias Kokkinis]

Dear all,

after some further research into the matter, it seems I have to do some 
asynchronous capture/playback with ALSA.

I have searched for examples and found this site:
http://alumnos.elo.utfsm.cl/~yanez/alsa-sample-programs/
where two example programs are included.

microphone.c and speaker.c which use almost all available input/output modes in 
ALSA. The interesting thing is that you can run both programs concatenated 
since they write and read to the standard output and create a simple audio 
loop-back. 

I have tested different configurations and the configuration I want works with 
direct and asynchronous read/write with mmap and read/write with poll.

Now I have taken the bits and pieces of those to programs and I have tried to 
create a single program that will read and write with different buffer sizes. I 
can't seem to be able to "reroute" the write from the standard output [these 
programs use write() and read()] to a buffer, or the read from the standard 
input to a buffer. 

Any ideas? Comments? 

I thank everyone for their time,
Elias

On 16 Jan 2012, at 12:53, Elias Kokkinis wrote:

> Hello all,
> 
> I am posting a question I previously posted in alsa-devel, but did not get 
> the expected feedback.
> 
> I am using alsa drivers in an OMAP3530 processor to do some audio processing. 
> I am implementing a typical speech enhancement algorithm with overlap-add. I 
> use a window length of 2048 samples and an overlap of 1024 samples. That 
> means I need to use an input (capture) buffer of 2048 and an output 
> (playback) buffer of 1024. Can this be configured in alsa? Can the playback 
> and capture streams have different buffer sizes, but operate at the same 
> sample rate (e.g. 44100Hz)?
> 
> Best regards,
> Elias
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