A quick background: I'm developing a VOIP program for an embedded system. In the first phase of the program everything was event driven. Basically ask ALSA for samples, encode them, and send them via UDP to the connected client. On the other end, receive the packet, decode, play the samples. After setting the correct value for the start_threshold function everything worked great no xruns at all. Now in the second phase, events are timed due to specification requirements. The same Alsa setup code is used yet xruns (mostly underruns) are all over the place. The underruns are periodic and can be reduced by increasing the period size and number of periods (this also increases the latency obviously and is undersirable) but never removed completely.

My question is how to reduce/remove the xruns. I am not currently at a point where installing a real-time OS or patching to get these features is possible. Also, when aplay/arecord is run on the system, no xruns occur. Finally, the CPU is not being overloaded, actually in the second phase the CPU usage is much less. Any help/suggestions are greatly appreciated. Thanks in advance!