Subject: Re: [linux-audio-dev] midi events in jack callback (was: Reborn)
From: Billy Biggs (vektor_AT_dumbterm.net)
Date: Fri Aug 16 2002 - 17:04:35 EEST
Paul Davis (pbd_AT_op.net):
> none of this, alas, addresses the more fundamental question of how to
> do the timing correctly. without something like the hard-timer patch,
> its more or less impossible to do MIDI sequencing correctly under
> linux. of course, you can do it "well enough" with existing
> mechanisms, but the reason most people haven't noticed this yet is
> that there is fairly strong division between audio + MIDI software.
> its only when *this* MIDI event needs to be delivered at audio frame N
> that you start to see the problems. there is no way to accurately
> schedule anything under Linux with hard-timers unless by accurately
> you mean either "resolution = HZ" or "resolution = RTC Hz" or
> "resolution = audio interrupt frequency".
What do you think the solution is? Someone on #lad mentioned that
ardour apparently outputs MIDI clock sync. How do you swing that one?
Right now, all of my MIDI messages are output with reasonably constant
latency clocked from a remote MIDI clock: effectively software MIDI
thru. This + close-to-realtime audio means that my PC will hopefully
output correct on both MIDI and audio in sync with constant latency,
using my drum machine or hard disk recorder as the clock source.
-- Billy Biggs vektor_AT_dumbterm.net
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