Re: CAClock and MIDI Clock
Re: CAClock and MIDI Clock
- Subject: Re: CAClock and MIDI Clock
- From: Doug Wyatt <email@hidden>
- Date: Thu, 9 Oct 2008 23:51:38 -0700
On Oct 9, 2008, at 19:58 , Evan Olcott wrote:
I'm not sure I understand what's going on with the sending of MIDI
clocks via the CAClock. (I haven't even tapped into the MTC stuff
yet, but I will once I understand this). There is no M in RTFM in
this case, so I came here:
I want to send MIDI clocks to a given MIDI endpoint by using
CAClock. So far so good.
A few issues I can't seem to resolve:
1) The clock seems to ALWAYS run regardless of CAClockStart or
CAClockStop.
Don't ask for the current time when the clock is stopped :-) Time
keeps moving, though in another release maybe it won't, but knowing
that it's stopped, you don't have to ask the question that results in
a disturbing answer :-P
I assume this is because these methods start and stop the *media
timeline* and not the timebase.
Correct.
This also makes me assume that the MIDI clocks are based on the
timebase alone, and so if the MIDI endpoint exists, the clocks will
be sent as long as the CAClock exists. The only way to stop it being
sent to a particular MIDI endpoint is if it's not on the list for
CAClock in the first place. Is this a correct assumption?
No. MIDI clocks are sent to mark the progression through the media
timeline, bracketed by the appropriate start and stop messages when
clock starts and stops.
2) It also seems as though tempo changes have no effect on the MIDI
clock.
... on the clock being sent? You should be able to create a tempo map
or call SetCurrentTempo, send clock through or to a device with MIDI
activity indicators and watch the rate of blinking change with the
tempo. No hardware? Try a MIDI monitor and satisfy yourself that the
time between the F8 messages changes :-P
Or if you have Logic or another MIDI sequencer, route your outgoing
clock messages to it through the IAC driver and see what it does.
I can't even yet confirm that tempo changes are happening, since I
am really only using the CAClock for the MIDI clock/MTC, and I won't
really be using the media timeline (I don't think). The clocks run
at a nice, steady 120bpm. How does one change the tempo that the
MIDI clocks get sent?
Well, there's SetCurrentTempo but read the caveat about its
interaction with the tempo map. Depending on what you're doing, you
might want to set a tempo map consisting of exactly one entry.
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