[alsa-devel] ALSA buffer query

[Jaroslav Kysela]

On Thu, 11 Nov 2010, Irfan Shaikh wrote:

> Thanks for reply,
>
> Please tell me if my understanding is correct
>
> 1) Check number of frames ready to be written in DMA area - using snd_pcm_avail_update
> 2) Call snd_pcm_mmap_begin(snd_pcm_t  * pcm, const snd_pcm_channel_area_t ** areas, snd_pcm_uframes_t * offset, snd_pcm_uframes_t * frames)
>
>     (what does offfset specify here ?)

Offset to areas.

> 3) I need to fill my audio data to be played in area  {Please tell me if this is correct}

Yes.

> 4) snd_pcm_mmap_commit(pcm_handle, offset, frames);
>
>     Please tell me is my understanding correct to play my audio buffer 
> on ASLA playback device.

You may consult the pcm.c example for all transfer methods:

http://git.alsa-project.org/?p=alsa-lib.git;a=blob_plain;f=test/pcm.c;hb=HEAD

 					Jaroslav

-----
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.