[alsa-devel] pointer callback question

[Takashi Iwai]

At Thu, 12 Feb 2009 18:50:45 +0100,
Tim Blechmann wrote:
> 
> hi all,
> 
> one question about the pointer callback.
> 
> the docs say:
> >  This callback is called when the PCM middle layer inquires the current
> >  hardware position on the buffer. The position must be returned in
> frames,
> >  ranging from 0 to buffer_size - 1.
> 
> i am using a ringbuffer to communicate with my audio device. but when
> the position is reset to 0, alsa requests to stop the stream
> (SNDRV_PCM_TRIGGER_STOP).
> 
> the brief log is (4 periods of 64 frames):
> stream_pointer at 64
> stream_pointer at 128
> stream_pointer at 192
> stream_pointer at 256

This is invalid.  The pointer callback must return 0 in this case.
The value the pointer callback returns is between 0 and buffer_size-1.


Takashi

> stream_pointer at 0
> 
> after returning 0, a stop is requested.
> 
> am i missing something?
> thanks, tim
> 
> -- 
> tim at klingt.org
> http://tim.klingt.org
> 
> Contrary to general belief, an artist is never ahead of his time but
> most people are far behind theirs.
>   Edgar Varèse
>