[alsa-devel] Using MMAP feature

Clemens Ladisch clemens at ladisch.de
Mon Jul 23 16:46:44 CEST 2012

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alberto Villa wrote:
> Il 23/07/2012 12:38, Clemens Ladisch ha scritto:
>> alberto Villa wrote:
>>> Hello,
>>> I'm going to use the MMAP feature of ALSA.
>> Why do you need to do this?
> I need to use MMAP because we are running on an embedded system and we
> want to optimize its operations.

What exactly do you want to optimize?  In most cases, mmap is no faster
than snd_pcm_write; using mmap make sense only if the samples are
generated dynamically without storing them in a userspace buffer.

> It was necessary to use snd_pcm_wait() before snd_pcm_begin(), may be
> this the reason?

If you never wait, the buffer will be filled eventually.


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