[alsa-devel] dsnoop issues

[Takashi Iwai]

At Fri, 27 Apr 2007 13:27:00 +0100,
Gordon Miller wrote:
> 
> Hi
> 
> All my snd_pcm_readi calls return too few frames. Also when I switch to 
> stereo, the sound is muted. I cannot change this by adjusting period & 
> buffer sizes. dsnoop is enabled by default. The documentation for 
> snd_pcm_readi says that the only way that the frame count can be short 
> is because of a signal or xrun. Well this clearly isn't the case.

Actually, the documentation is wrong, IMO.  The typical behavior of
read syscall is that it returns a value actually read by that call.
It doesn't guarantee whether the requested size is filled, and can be
shorter than requested.  As snd_pcm_readi() emulates the read syscall,
it should behave in that way.

The blocking mode means that the function waits until the threshold
(watermark) condition is fulfilled.


Takashi