[LAD] timers

Sat Nov 7 13:36:58 UTC 2009

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
>>>
>>>       
>>       
>> _______________________________________________
>> 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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