7 Nov
2009
7 Nov
'09
8:39 a.m.
I forgot to add that snd_hrtimer is used by jackd.
If I turn jackd off, the snd_hrtimer module is not used:
$ lsmod | grep timer
snd_hrtimer 2148 0 ## <<< not used
snd_timer 17408 3 snd_hrtimer,snd_seq,snd_pcm
J.
--- On Sat, 11/7/09, James Warden <warjamy(a)yahoo.com> wrote:
From: James Warden <warjamy(a)yahoo.com>
Subject: Re: [LAD] timers
To: "Emanuel Rumpf" <xbran(a)web.de>de>, "Ralf Mardorf"
<ralf.mardorf(a)alice-dsl.net>
Cc: linux-audio-dev(a)lists.linuxaudio.org
Date: Saturday, November 7, 2009, 7:34 AM
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(a)alice-dsl.net>
wrote:
From: Ralf Mardorf
<ralf.mardorf(a)alice-dsl.net>
Subject: Re: [LAD] timers
To: "Emanuel Rumpf" <xbran(a)web.de>
Cc: linux-audio-dev(a)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@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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