In the course of debugging some issues in a plug-in of ours, I have
found that Logic delivers MIDI messages later than expected. This
wreaks havoc with our arpeggiator, which syncs itself exactly with
the transport position information reported by the AU host.
To be sure of my suspicion, I created a small test AU which exposes
the issue...
Based on the values returned by HostCallback_GetBeatAndTempo() and
the startFrame of the each MIDI event, it calculates the exact start
beat of the MIDI note event and how late it is (assuming the note was
intended to start on a beat).
It found that under Logic Pro 7.2.3, the notes are between 1 and 22
samples late.
Under Logic Pro 8.0.0 (and GarageBand 4.1.1), the notes are either 21
or 22 samples late (at 44.1 kHz) or 24 samples late (at 48 kHz).
In all three the very first note (on the first beat) in a track is
scheduled on time.
Maybe I'm doing something wrong - I'd be happy if someone could prove
it!
If not, is this a known bug in Logic / GarageBand?
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