[LAD] timers

[James Warden]

Hi guys,

Here is what I have:


$ cat /proc/asound/timers
G0: system timer : 1000.000us (10000000 ticks)
G3: HR timer : 0.001us (1000000000 ticks)
  Client sequencer queue 0 : running
P1-0-0: PCM playback 1-0-0 : SLAVE
P1-0-1: PCM capture 1-0-1 : SLAVE

Ralf, you do not benefit from a high res timer. See how much more precise the HR timer is from the output above. Check which snd timer you have loaded:

$ lsmod | grep timer

snd_hrtimer             2148  1
snd_timer              17408  3 snd_hrtimer,snd_seq,snd_pcm

Of course, your h/w should have a HR timer:

$ ll /dev/hpet
crw-rw---- 1 root audio 10, 228 2009-11-05 12:59 /dev/hpet

you can specify the clock source to jackd:

$ jackd --help
...
[ --clocksource OR -c [ c(ycle) | h(pet) | s(ystem) ]
...



J.


--- On Sat, 11/7/09, Ralf Mardorf <ralf.mardorf at alice-dsl.net> wrote:

> From: Ralf Mardorf <ralf.mardorf at alice-dsl.net>
> Subject: Re: [LAD] timers
> To: "Emanuel Rumpf" <xbran at web.de>
> Cc: linux-audio-dev at lists.linuxaudio.org
> Date: Saturday, November 7, 2009, 7:04 AM
> Emanuel Rumpf wrote:
> > Hi
> >
> > I'm confused about all the timers.
> >
> > There is:
> > - system timer
> > - hpet (high precision event timer)
> > - hr-timer (high resolution timer)
> > - rtc (real time clock)
> > - cyclic (what's that? a coded loop?)
> > - anything else ?
> >
> >
> > What is the relation of all these ?
> > Which hardware devices are actually used by those ?
> > Which is the prefered timer for sequencing ? hr-timer
> / rtc ?
> >   
> 
> If hardware is fine with Linux real-time audio, if I
> understand 
> correctly, the preferred timer for MIDI sequencers is
> (should be) system 
> timer at ! 1000 Hz ! For my hardware, that has got problems
> with 
> real-time audio, it's PCM playback and PCM capture. Using
> this timers 
> MIDI jitter will decrease a little bit.
> 
> This is the output I get for 64 Studio 3.0-beta3:
> 
> spinymouse-sudo at 64studio:~$ cat /proc/asound/timers
> G0: system timer : 1000.000us (10000000 ticks)
> P0-0-0: PCM playback 0-0-0 : SLAVE
> P0-0-1: PCM capture 0-0-1 : SLAVE
>   Client sequencer queue 0 : stopped
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