[LAD] timers

Sat Nov 7 13:45:31 UTC 2009

Ralf,

It depends how ALSA was compiled in the kernel. Here is my kernel config related to this matter:

CONFIG_SND=m
CONFIG_SND_TIMER=m
CONFIG_SND_PCM=m
CONFIG_SND_HWDEP=m
CONFIG_SND_RAWMIDI=m
CONFIG_SND_SEQUENCER=m
CONFIG_SND_SEQ_DUMMY=m
# CONFIG_SND_MIXER_OSS is not set
# CONFIG_SND_PCM_OSS is not set
# CONFIG_SND_SEQUENCER_OSS is not set
CONFIG_SND_HRTIMER=m
CONFIG_SND_SEQ_HRTIMER_DEFAULT=y

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: "James Warden" <warjamy at yahoo.com>
> Cc: "Emanuel Rumpf" <xbran at web.de>, linux-audio-dev at lists.linuxaudio.org
> Date: Saturday, November 7, 2009, 8:36 AM
> Thank you Emanuel for this thread :)
> thank you James for the information :)
> 
> hopefully this might narrow down my trouble with MIDI
> jitter for external equipment, OTOH I don't have any MIDI
> jitter for MIDI internal Linux. ALSA MIDI and JACK MIDI
> seems to be fine what ever timer I use, this means there is
> absolutely no jitter when using a Linux sequencer to control
> a Linux synth. Jitter only occurs when using my USB
> MIDInterface to control external MIDI equipment.
> Unfortunately I can't get my Envy24's MPU working.
> 
> There seems to be no hrtimer available yet:
> 
> $ lsmod | grep snd_hrtimer
> $ lsmod | grep timer
> snd_timer             
> 22024  2 snd_pcm,snd_seq
> snd               
>     63800  21
> snd_ice1712,snd_ak4xxx_adda,snd_cs8427,snd_ac97_codec,snd_i2c,snd_mpu401_uart,snd_usb_audio,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_hwdep,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
> $ uname -a
> Linux 64studio 2.6.29-1-multimedia-amd64 #1 SMP PREEMPT RT
> Thu Feb 26 16:18:05 UTC 2009 x86_64 GNU/Linux
> 
> Before I start googleing. Is this a feature for 2.6.31
> only? I'm still not able to boot the .31 kernel-rt from the
> Suse 11.2 RC repository and compiling for Suse also failed,
> but in the past I never had trouble to build kernel-rt for
> Debian/ Ubuntu based 64 Studio. Maybe I should try to build
> a kernel .31 for 64 Studio? Or is it just a module I need to
> add? Or is my hardware missing something?
> 
> Going to use Google now.
> 
> Bye,
> Ralf
> 
> James Warden wrote:
> > 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 at yahoo.com>
> wrote:
> > 
> >   
> >> From: James Warden <warjamy at yahoo.com>
> >> Subject: Re: [LAD] timers
> >> To: "Emanuel Rumpf" <xbran at web.de>,
> "Ralf Mardorf" <ralf.mardorf at alice-dsl.net>
> >> Cc: linux-audio-dev at 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 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
> >>>
> _______________________________________________
> >>> Linux-audio-dev mailing list
> >>> Linux-audio-dev at lists.linuxaudio.org
> >>> http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
> >>> 
> >>>       
> >>   
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> >> http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
> >> 
> >>     
> > 
> > 
> >       
> >   
> 
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