AU, plugin tempo, musical time information
AU, plugin tempo, musical time information
- Subject: AU, plugin tempo, musical time information
- From: Paul Davis <email@hidden>
- Date: Mon, 2 Nov 2009 12:22:39 -0400
hi there. i'm the lead developer of Ardour and the original author of
JACK. i'm in the middle of implementing support for host callbacks in
Ardour's AU support, and the best documentation i've been able to find
so far on the data provided by the "getMusicalTime" callback includes
this paragraph:
>For a change from 3/4 to 4/8 the value of the beat does not change
>(thus, a 4/8 time sig will still have 2 beat values for that measure -
>the value of the beat unit does not change as the time signature
>changes). In common practise a beat is generally associated with a
>quarter note.
(from the documentation in the Developers/.../AudioUnits area)
This is quite a strange assumption. I've spoken to several experienced
musicians and this is absolutely the opposite of their sense of
musical time. If the meter shifts to 8, then a beat is an 1/8th note,
not a 1/4. If you were working on a piece entirely in 5/8 time, you
would not count in 1/4's but 1/8ths.
How to reconcile this commentary with this observation? Ardour counts
beats according to the meter, so in the example given in the doc, the
3/4 bar has 3 1/4 note beats, the 4/8 bar has 4 1/8th note beats and
the position at the end of the 2nd bar is 7 beats into the timeline,
not 5. Should the out argument in the host callback really be
considered as "quarter notes from timeline start" rather than "beats
from timeline start?"
One other related question. the "getTransportState" callback includes
a field to indicate whether or not the transport has changed. But the
documentation does not specify what it might have changed relative to.
The last callback?
thanks,
--p
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