Subject: Re: [ecasound] A question, a weird problem and a bug
From: Kai Vehmanen (kaiv@wakkanet.fi)
Date: Mon Apr 16 2001 - 23:12:13 EEST
On Wed, 21 Mar 2001, S. Massy wrote:
> a bit surprised to find out that the amount of cpu power in use varied
> greatly whereas it remains relatively stable for normal operations
> (simple playback for example). Actually it follows a very constant pattern
> where the amount of cpu time in use climbs steadily before falling
> back. I don't have the exact intermediate values but it always seem to
> reach up to 25% of the cpu as its max value and 0.1% as its
Did you have double-buffering mode enabled? When -z:db
is enabled, disk thread wakes up once in a while, runs
at full disk speed to fill up the buffers, and then
returns back to sleep.
> created through /proc (which is top -d 0.01) Well, I ran top updating
> its info from /proc every hundredth of a second for five minutes (it
> was also using up to 70% of the cpu power) and ecasound remained rock
> solid, no xrun. Then I just exited top and typed "ps" and BANG, xrun!
> Anyone having a possible explanation for this? I realize it is most
> likely related to alsa, still, it seems weird, doesn't it?
Huh, beats me. :) I'd bet my money on a kernel-related
latency problem.
> Finally I noticed that whenever an xrun occurs and alsa device is used
> for playback, the playback does not resume and the following is
> printed:
> ALSA lib pcm_hw.c:254:(snd_pcm_hw_start) SNDRV_PCM_IOCTL_START failed:File descriptor in bad state
> The processing continues but what is sent to that particular device is
> not heard. I have to issue a "stop" then "start" for the device to be
> properly initialized once again. As I understand it, when encountering
> an xrun and in -z:noxruns mode, ecasound stops and restart in an
> attempt to get everything back into sync. Is it possible that there's
> a bug in the code supposed to reinitialize the alsa device performing
> playback?
It should restart ALSA devices properly after an xrun. Oh well, I'll
check the related ecasound code once ALSA 0.9.x API documentation gets
ready.
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