Subject: Re: [linux-audio-dev] Utility for recording audio track with midi clock
From: Tim Goetze (tim_AT_quitte.de)
Date: Thu Jul 01 2004 - 17:32:15 EEST
[Paul Davis]
>until the high resolution clock timers patch is solid enough to be
>used by any system, there is no way to schedule MIDI output with this
>kind of resolution, and if you can't schedule it, then the receiver of
>your MIDI clock signal will see a lot of jitter and may refuse to lock
>to it. Even if it locks, its not clear what it will do with the jitter.
fwiw, i'm achieving quite satisfying results driving MIDI out from a
1024 Hz RTC thread, with external hardware locking steadily onto the
output MIDI clock stream, even at tempi up to 240 bpm.
MIDI out jitter is about the audio block size at max. DSP load (~1.3
ms) during audio processing cycles, a fraction of a millisecond for
the difference between 1024 Hz and the wanted MIDI clock frequency
otherwise; however this seems to be no problem for the hardware
attached (a fairly recent synthesizer and infrequently an aging cheap
drum machine).
at lower RTC frequencies, the jitter effect on the MIDI h/w becomes
noticeable (erratic rubato) but it still locks on.
thus, i must disagree with your 'no way'.
tim
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