While trying to track down the source of some poor timing in sequencing, I've noticed that my ALSA sequencer queue timer has a tendency to fall suddenly behind.
I have a little test program (available on request) that just starts a queue and every second or so compares the queue timer against real time as returned by gettimeofday(). It doesn't mind if the two don't quite match, but it does complain if the difference between the two timers changes dramatically between two sample points. When I run it, it never lasts for more than about a minute before the ALSA queue timer suddenly slips by anything from 10 to 60 milliseconds. This is a non-low-latency kernel so I'm not surprised that there may be some occasional timing issues, but 60ms is a lot on an unloaded machine, and I am vaguely surprised that the timer doesn't notice it's fallen behind and recover -- instead all events on the queue continue to be delivered late forever. This obviously makes for some disconcerting audible effects. The system is SuSE 9.0 on a dual 2GHz Athlon using SuSE's stock SMP kernel. I have tried both ALSA 0.9.6 (from SuSE) and 1.0.0rc2 drivers and libraries. I haven't managed to reproduce it using a PlanetCCRMA SMP kernel on the same machine, nor on my uniprocessor laptop. I've surveyed a few other people on rosegarden-devel and nobody's corroborated my findings, so I guess it might be related to using a dual-processor machine. Any thoughts on this, anyone? I'm finding it a little depressing that I can't play even a minute of 4/4 beats from an ALSA test program without the timing slipping audibly at least once. I'm ready to delve cluelessly into the timer code to take a look, but (glancing at alsa-kernel/core/timer.c) I'm not at all sure how far I'd get... Chris ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. Does SourceForge.net help you be more productive? Does it help you create better code? SHARE THE LOVE, and help us help YOU! Click Here: http://sourceforge.net/donate/ _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
