Re: [linux-audio-dev] midi events in jack callback (was: Reborn)

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Subject: Re: [linux-audio-dev] midi events in jack callback (was: Reborn)
From: Martijn Sipkema (msipkema_AT_sipkema-digital.com)
Date: Fri Aug 16 2002 - 18:17:50 EEST


> >Haven't written anything using MIDI and JACK (or LADSPA), but would it be
poss
> >ible to have a such system as with Cubase where the softsynths are
plugins whi
> >ch receive time-stamped MIDI events (time-stamp is an offset from the
block be
> >ginning in samples).

Either this (use audio sample clock) or use a common clock, i.e. have a UST
timestamp
for every MIDI message and audio buffer (audio frame time can then be
estimated).
IMHO the latter is better.

> >The MIDI-through events that come into sequencer from the
> > external MIDI (in) port always have an offset of zero so the synth
renders th
> >e data starting from the first sample in that block.

This is not the right approach as it will cause jitter.

[...]
> 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".

I agree, however HZ=1000 should be usable for MIDI even without patches
for improved scheduling. I believe HZ=1000 is in 2.5?

--martijn


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