I am using Logic Pro 9 to output Midi Time Code to trigger events on a lighting console. When outputting at regular speed everything syncs up fine, the audio track syncs to the lighting console and the events are triggered accordingly.
You mean the Lighting console/computer syncs to the computer that has audio output and MTC output, right?
When using Varispeed I don't think MTC would, or should change, in fact I'm sure that's the case. Changing the speed of the audio only shortens (or lengthens) the speed and pitch of the audio within a static time frame. MTC defines the static time frame you're working within.
That is... if I'm reading your question correctly.
Everything changes speed as the playbar travels, not just audio, midi tracks play faster, the counter counts faster. It's a global speed change. Midi notes are being played back faster and MTC is in the midi signal. What we're trying to figure out is what data is coming from the Midi out from Logic at those variable speeds. Example: at higher speeds, is the MTC data still coming out in quarter frames (4-bit pieces, instead of a full frame 32-bit long burst)? What does the MTC look like during varispeed coming out of Logic? This is more of a question for an Apple/Logic software engineer... any out there?
It doesn't matter that the MIDI tracks play faster... MTC does NOT change with Varispeed enabled, MTC is a constant and is Time oriented. I just tested this between the two computers in my studio and saw no difference in MTC output with Varispeed + MIDI enabled, I tried several different speed percentages both faster and slower.
MIDI output is a separate entity from MTC, they are not tied together.
MIDI Clock may change (I didn't test that). MIDI Clock is beat/measure oriented.
So, my answer is... MTC looks the same.
It's possible an Apple/Emagic person may respond here but I think you may have to call support to get a final answer.