Re: CAClock and MIDI Clock
Re: CAClock and MIDI Clock
- Subject: Re: CAClock and MIDI Clock
- From: Evan Olcott <email@hidden>
- Date: Fri, 10 Oct 2008 09:34:04 -0500
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
Yea, I'm not so worried about the current time at this point, I'm
still just trying to control beat clocks. Duly noted however.
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.
Actually, this isn't what I'm observing:
1. A MIDI receiving app (Rax 3) builds virtual input ports
2. I load up Kurt's fantastic MIDI Monitor
- set it up to "spy" on one of Rax's ports
3. I start up my MIDI Clock utility
- creates a CAClock, no error
- I add one of Rax's ports to the CAClock for MIDI clock delivery -
IMMEDIATELY clock begins to send
- I click "start", a "start" message is sent and clock keeps going
- I click "stop", a "stop" message is sent (with a 0 timestamp), and
clock keeps on going
- I click "start" again, "continue" and "song pointer" messages are
sent, and clock keeps going
- I click "stop", a "stop" message is sent (with a 0 timestamp), and
clock keeps on going
I think I see an inherent conflict with "time keeps moving" like
you're saying above and starting and stopping clock. The messages are
indeed bracketed by start/stop messages, but as soon as there's a MIDI
endpoint to send to, the clock rolls right on out and doesn't stop.
Isn't MIDI clock supposed to stop sending after a stop message? Or am
I wrong? I could have sworn I read that that's how it's supposed to be
interpreted...
Additionally, how do I tell the CAClock the difference between a
"start" message and a "continue" message to send when I call
CAClockStart? It seems to just sorta "know", but what if I want to
start at the beginning? Does that have to do with CASetCurrentTime?
I'll hold off on the rest of the tempo conversation, but I DO want to
get back to it - I gotta understand this part of it first. I feel like
I'm missing some philosophical understanding of how this is supposed
to work.
Ev
Technical Knowledge Officer
Head Programmer/Designer
Audiofile Engineering
http://www.audiofile-engineering.com/
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