[alsa-devel] DMA buffer gets played only once
markus.franke at s2002.tu-chemnitz.de
Thu Sep 6 08:10:46 CEST 2007
Trent Piepho wrote:
> You need to make sure the buffer size is an integer multiple of the period
> size if you wrap like this.
Yeah I have to take care of this but right now my buffersize is 32768
bytes and the period size is 4096 bytes which should work I think.
> I found that ALSA would call TRIGGER_STOP if it detected an overrun.
Yeah that's right. I guess this is my case because xrun() is getting
called somewhere. So how can I fix this underrun problem?
> Check the value returned for every call of your pointer callback. I found out
> that ALSA was calling the pointer callback before the first IRQ, which was
> something I hadn't planned on and the values confused ALSA.
That's not my case. pcm_pointer gets called after the first DMA
transaction is finished. (DMA transfer finished callback gets called
before pcm_pointer) Also the values which are returned by pcm_pointer
look quite reasonable. (see also my very first posting in this thread,
look for the printk's "pcm_pointer returns <value>")
Thanks for your effort,
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