On Wed, 2010-07-14 at 14:12 -0700, Devin Anderson wrote: > On Wed, Jul 14, 2010 at 12:43 PM, Ralf Mardorf > <ralf.mard...@alice-dsl.net> wrote: > > On Wed, 2010-07-14 at 12:30 -0700, Devin Anderson wrote: > >> On Wed, Jul 14, 2010 at 10:29 AM, Ralf Mardorf > >> <ralf.mard...@alice-dsl.net> wrote: > >> > >> > Hi :) > >> > > >> > delayed by a thunder-storm I could do another test. > >> > --snip-- > >> > >> So, what you're saying is that your MIDI device and software synth > >> sync up less and less as you raise the period size. > > > > Yes :). > > > >> I had presupposed > >> before that your MIDI device was triggering *after* your software > >> synth, but it occurs to me that it might be the other way around. Do > >> you hear the audio from your software synth first, or from your MIDI > >> device? > > > > I can't say it today, now I do some office work. I had the impression > > that it might vary. Sometimes the virtual drum sampler and sometimes the > > standalone drum sampler was played earlier, I need to check this ASAP. > > For older tests with my USB MIDI device it was exactly that way, that > > jitter had positive and negative delay. At least the recorded waveforms > > of external MIDI equipment (when I used USB MIDI, now I'm using PCI > > MIDI), were recorded by Qtractor, before theoretically the MIDI event > > was send ;). Note! Qtractor had no latency compensation, all recorded > > audio of external MIDI instruments should have (positive) delay, but > > negative delay. > > If it ends up being the case that your MIDI device is being triggered > before your software synth, then I'm guessing that the issue here is > not MIDI jitter. I'm guessing the issue is that the latency that's > imposed by JACK on incoming and outgoing audio is not imposed on > incoming and outgoing ALSA MIDI. So, while the audio coming out of > the software synth is delayed by a certain amount of frames imposed by > JACK, the audio coming out of your MIDI device is only delayed by the > latency of the ALSA drivers, the latency of the MIDI ports, the > latency of your MIDI device. > > This would certainly explain why the problem gets worse as you raise > the period size, and could explain why you had positive and negative > delay in your older USB MIDI tests, as the reported MIDI jitter in > your tests was *far* worse in your older tests than it is now. > > At the moment, I happen to be doing some work in JACK 2 that could > potentially solve this issue by enabling MIDI to sync more closely > with audio, so I'm very curious to know if my suspicions are correct. > Please keep me updated. :)
Should I build JACK dummy packages for 64 Studio and daily get JACK2 from svn co http://subversion.jackaudio.org/jack/jack2/trunk/jackmp ? I wonder if this should be cross-posted to LAD? On LAD and the 64 Studio list are people with much knowledge and your reply might hit the nail on the head. - Ralf _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev