If I'm not mistaken the timing for your audio is coming from your sound card not your system clock. The gettimeofday is from the system clock. They probably won't match. Of course, I could be totally in the dark ;-)
Jan On Sun, 2003-12-14 at 08:07, Chris Cannam wrote: > > 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 ------------------------------------------------------- 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
