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[linux-audio-dev] A sequencer example

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krampenschiesser＠freenet.de

15 Jan 2006 15 Jan '06

5:46 a.m.

Does someone have a very simple sequencer example? Something sending one note in 4/4? I don't get along with the timing of the alsa sequencer. I hope you can help me. Scar -- All the evidence concerning the universe has not yet been collected, so there's still hope.

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Florian Schmidt

15 Jan 15 Jan

7:12 a.m.

On Sun, 15 Jan 2006 10:46:14 +0100 krampenschiesser(a)freenet.de wrote:

Does someone have a very simple sequencer example? Something sending one note in 4/4? I don't get along with the timing of the alsa sequencer. I hope you can help me. Scar

Hi, i don't know whether you want to send midi events directly or schedule them via alsa_seq. If the former case have a look at my small test programs in this tarball http://affenbande.org/~tapas/midi_timer-1.tgz There's two programs in that tarball, one using the RTC for timing and the other using the system timer and usleep() (the RTC based one does achieve better accuracy). Both programs simply try to send a stream of note-on events at very regular intervals. If you want to use alsa_seq's queues to schedule events for delivery at a later time, you probably might have a look at rosegarden. Have fun, Flo -- Palimm Palimm! http://tapas.affenbande.org

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Chris Cannam

7:20 a.m.

On Sunday 15 Jan 2006 11:12, Florian Schmidt wrote:

If you want to use alsa_seq's queues to schedule events for delivery at a later time, you probably might have a look at rosegarden.

There's a file base/test/seq/generator.c in the Rosegarden source tree that does basically what was described using the sequencer queue. It does however schedule in real-time rather than beats (and so does Rosegarden itself). http://cvs.sourceforge.net/viewcvs.py/rosegarden/base/test/seq/generator.c?… Chris

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mlang

9:22 a.m.

Chris Cannam <cannam(a)all-day-breakfast.com> writes:

On Sunday 15 Jan 2006 11:12, Florian Schmidt wrote:

If you want to use alsa_seq's queues to schedule events for delivery at a later time, you probably might have a look at rosegarden.

There's a file base/test/seq/generator.c in the Rosegarden source tree that does basically what was described using the sequencer queue. It does however schedule in real-time rather than beats (and so does Rosegarden itself). http://cvs.sourceforge.net/viewcvs.py/rosegarden/base/test/seq/generator.c?…

Pretty intersting, I just ran this and noticed it (the diff between queue and gettimeofday time) drifts about 70 usecs per second. Is this normal expected behaviour, or another reason to hate the day I decided to buy a X2 CPU? P.S.: ANyone got any hard facts on the TSC SMP issues? 2.6.15 is definitely worse for me than 2.6.14, things that used to work just dont anymore. -- CYa, Mario

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Lee Revell

9:48 a.m.

On Sun, 2006-01-15 at 14:23 +0100, mlang wrote:

Chris Cannam <cannam(a)all-day-breakfast.com> writes:

On Sunday 15 Jan 2006 11:12, Florian Schmidt wrote:

If you want to use alsa_seq's queues to schedule events for delivery at a later time, you probably might have a look at rosegarden.

There's a file base/test/seq/generator.c in the Rosegarden source tree that does basically what was described using the sequencer queue. It does however schedule in real-time rather than beats (and so does Rosegarden itself). http://cvs.sourceforge.net/viewcvs.py/rosegarden/base/test/seq/generator.c?…

Pretty intersting, I just ran this and noticed it (the diff between queue and gettimeofday time) drifts about 70 usecs per second. Is this normal expected behaviour, or another reason to hate the day I decided to buy a X2 CPU? P.S.: ANyone got any hard facts on the TSC SMP issues? 2.6.15 is definitely worse for me than 2.6.14, things that used to work just dont anymore.

Yes, the TSC is useless on these machines, but the kernel can work around it. You need JACK patched to use clock_gettime() for jack_get_microseconds. This really should be in JACK CVS by now, if it is not already. Lee

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mlang

2:27 p.m.

Lee Revell <rlrevell(a)joe-job.com> writes:

On Sun, 2006-01-15 at 14:23 +0100, mlang wrote:

Chris Cannam <cannam(a)all-day-breakfast.com> writes:

On Sunday 15 Jan 2006 11:12, Florian Schmidt wrote:

If you want to use alsa_seq's queues to schedule events for delivery at a later time, you probably might have a look at rosegarden.

There's a file base/test/seq/generator.c in the Rosegarden source tree that does basically what was described using the sequencer queue. It does however schedule in real-time rather than beats (and so does Rosegarden itself). http://cvs.sourceforge.net/viewcvs.py/rosegarden/base/test/seq/generator.c?…

Pretty intersting, I just ran this and noticed it (the diff between queue and gettimeofday time) drifts about 70 usecs per second. Is this normal expected behaviour, or another reason to hate the day I decided to buy a X2 CPU? P.S.: ANyone got any hard facts on the TSC SMP issues? 2.6.15 is definitely worse for me than 2.6.14, things that used to work just dont anymore.

Yes, the TSC is useless on these machines, but the kernel can work around it. You need JACK patched to use clock_gettime() for jack_get_microseconds.

THis doesn't make sense to me, either the kernel can work around it properly *OR* we have to patch userland. -- CYa, Mario

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Lee Revell

2:36 p.m.

On Sun, 2006-01-15 at 19:28 +0100, mlang wrote:

Lee Revell <rlrevell(a)joe-job.com> writes:

On Sun, 2006-01-15 at 14:23 +0100, mlang wrote:

Chris Cannam <cannam(a)all-day-breakfast.com> writes:

On Sunday 15 Jan 2006 11:12, Florian Schmidt wrote: > If you want to use alsa_seq's queues to schedule events for delivery > at a later time, you probably might have a look at rosegarden. There's a file base/test/seq/generator.c in the Rosegarden source tree that does basically what was described using the sequencer queue. It does however schedule in real-time rather than beats (and so does Rosegarden itself). http://cvs.sourceforge.net/viewcvs.py/rosegarden/base/test/seq/generator.c?…

Pretty intersting, I just ran this and noticed it (the diff between queue and gettimeofday time) drifts about 70 usecs per second. Is this normal expected behaviour, or another reason to hate the day I decided to buy a X2 CPU? P.S.: ANyone got any hard facts on the TSC SMP issues? 2.6.15 is definitely worse for me than 2.6.14, things that used to work just dont anymore.

Yes, the TSC is useless on these machines, but the kernel can work around it. You need JACK patched to use clock_gettime() for jack_get_microseconds.

THis doesn't make sense to me, either the kernel can work around it properly *OR* we have to patch userland.

The kernel can work around it for the purposes of its own internal timekeeping, so that clock_gettime() and gettimeofday() return the correct results. But the kernel can't do anything if JACK uses rdtsc directly, as the TSCs remain unsynced, kernel workaround or no. So the kernel has to be changed to report the correct values when userspace calls clock_gettime(), but JACK also has to be changed to use clock_gettime() in place of rdtsc. Lee

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Dave Robillard

17 Jan 17 Jan

3:24 p.m.

On Sun, 2006-15-01 at 14:23 +0100, mlang wrote:

Chris Cannam <cannam(a)all-day-breakfast.com> writes:

On Sunday 15 Jan 2006 11:12, Florian Schmidt wrote:

If you want to use alsa_seq's queues to schedule events for delivery at a later time, you probably might have a look at rosegarden.

There's a file base/test/seq/generator.c in the Rosegarden source tree that does basically what was described using the sequencer queue. It does however schedule in real-time rather than beats (and so does Rosegarden itself). http://cvs.sourceforge.net/viewcvs.py/rosegarden/base/test/seq/generator.c?…

Pretty intersting, I just ran this and noticed it (the diff between queue and gettimeofday time) drifts about 70 usecs per second. Is this normal expected behaviour, or another reason to hate the day I decided to buy a X2 CPU? P.S.: ANyone got any hard facts on the TSC SMP issues? 2.6.15 is definitely worse for me than 2.6.14, things that used to work just dont anymore.

I just bought a shiny new X2 3800+ and am dealing with all this garbage as well. Extremely unimpressed with the whole situation in general, but anyway.... Right now I'm booting my kernel with clock=pmtmr and I've applied the attached patch to Jack and things seem to be working fine, at least superficially. -DR- P.S. Someone (who I forget) was having problems with Om and every action taking _seconds_ to produce a visible/audible response. This was the source of that problem, for the record.

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Paul Davis

3:32 p.m.

P.S. Someone (who I forget) was having problems with Om and every action taking _seconds_ to produce a visible/audible response. This was the source of that problem, for the record.

"The time that an action may take to occur will depend on how long it takes your operating system to schedule a thread onto the same processor as the one used to schedule the action. This is indeterminate." :))

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Lee Revell

6:56 p.m.

Paul, is that clock_gettime patch in JACK CVS yet? It appears that the kernel has been fixed as of 2.6.15. Lee

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Peter Brinkmann

15 Jan 15 Jan

8:19 a.m.

On Sun, Jan 15, 2006 at 10:46:14AM +0100, krampenschiesser(a)freenet.de wrote:

Does someone have a very simple sequencer example? Something sending one note in 4/4? I don't get along with the timing of the alsa sequencer. I hope you can help me. Scar

I learned this stuff by staring at Matthias Nagorni's miniArp. You can find it at http://www.suse.com/~mana/miniArp.c. Hope this helps, Peter

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participants (8)

Chris Cannam
Dave Robillard
Florian Schmidt
krampenschiesser＠freenet.de
Lee Revell
mlang
Paul Davis
Peter Brinkmann