[alsa-devel] How does ALSA detect underrun in OSS emulation?

[Timur Tabi]

Can someone explain to me the exact method that ALSA uses to detect underrun 
with OSS emulation?  I have a driver that reports underrun on almost every 
period when I use OSS emulation and I'm playing with a non-supported sample 
rate.  So I'm assuming that maybe my hardware is playing the audio too fast or 
too slow, and the driver is returning periods before ALSA expects them.  What I 
don't understand is: how does ALSA know that a period was finished too early. 
Does it use a timer, or is it purely application driven?

-- 
Timur Tabi
Linux kernel developer at Freescale