Subject: Re: [linux-audio-dev] MIDI sync issues; mmc, mtc, ...
From: Kai Vehmanen (kaiv_AT_wakkanet.fi)
Date: Wed Dec 20 2000 - 22:21:01 EET
On Tue, 19 Dec 2000, Paul Barton-Davis wrote:
>> And selecting among the various sync mechanisms is another difficult
>> issue. Plain midi clock has little meaning for a digital audio
> you need two kinds of sync:
> 1) SMPTE/MTC for location searching and general "wall clock" sync
> 2) word clock for ensuring that the sample clocks run at the
> same speed.
[...]
> with both of these in place, i think things work very well.
Yes, I understand this is the optimal case for syncing two digital
devices. But unfortunately the above is not possible in many cases.
Hmm, I guess what I'm aiming at with this is: what level (or techniques)
of syncronization are useful for end-users? I mean, I could implement a
weird midi-clock based thing, that would surely make my feature list a
little longer, but I'm not sure whether it is useful for some one. :)
Now MMC (and plain MIDI start/stop/continue) seems like something really
easy to implement, but I'm curious to find out what uses there are for
it. If it turns out to fit lots of uses, well, I'll implement it and might
even provide such luxories as documentation and examples! :)
I seach through some daw-related web sites, and stumbled on this
(Roland's VS1680 site):
--cut--
Synchronisation is well catered for, too -- the VS1680 can function as
MIDI Time Code (MTC) and MIDI Machine Control (MMC) master or slave. It
can even transmit MIDI clock, but since MIDI clock is simply a series of
pulses, it is not possible to synchronise the VS's audio to incoming
clock, basically because there's no way for it to know when the next pulse
will arrive. The VS provides an additional track, the sync track, for
recording MIDI clock from an external sequencer, and if you wish to align
the song's measure, beat and tempo with another MIDI recorder, a tempo map
can be made. The unit has an internal metronome or can send clicks to
external MIDI gear."
[...]
"The manual provides guidelines for synchronisation to Cakewalk Pro Audio
where Cakewalk is MMC master and MTC slave. For audio sequencers which can
transmit MTC, it's probably best to set the VS as MTC slave, so that
onboard audio from the computer stays in sync with its MIDI and with the
audio of the VS. This method has worked reliably for me for some time,
providing the VS receives a stable source of MIDI Time Code."
--cut--
This suggests that MTC is usable for syncing a hardware audio device to
software MTC-master. Oh well, more about MTC in the next message...
-- . http://www.eca.cx ... [ audio software for linux ] /\ . . http://www.eca.cx/sculpscape [ my armchair-tunes mp3/ra/wav ]
This archive was generated by hypermail 2b28 : Thu Dec 21 2000 - 14:18:01 EET