[QLab] MTC syncing

[Drew Dalzell]

I'm working on a setup where I've got three Qlab machines all chasing
an incoming MIDI Timecode signal. It looks like they only trigger a
start from the incoming MIDI and do not actually sync to it. Is this
true?

Drew
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[Sean Dougall]

Hi Drew,

Yes, MTC is only used for triggering the start; timecode (MTC and LTC)
are both too low-resolution and prone to jitter to be used reliably as
a clock source. If you need sample-accurate synchronization over long
cues, you'll need to resolve all three audio interfaces to a common
clock source (via word clock, for example).

(On rereading the question, that might not be what you're asking. If
you're wondering about whether QLab can chase events when timecode
comes in starting in the middle of a cue, the answer is no; this would
currently require doing timecode math on every cue in the workspace
whenever timecode starts, and cause too much overhead.)

Cheers,
Sean

[Drew Dalzell]

Drat.

Is there any plan for this? I've been doing it for quite a few years
in SFX and it will happily chase a clock and pickup from anywhere in
the stream and then stay in sync or free run when I lost sync
depending upon how it is set up.

I'd even be willing to use LTC if it were the only way, though MTC is
usually higher resolution since it actually goes down to subframes and
SMPTE only specifies resolution down to frame.

Drew

[Sean Dougall]

Hi Drew,

It's a definite possibility for a future release, but it may take some
figuring out. (LTC has the same limitation as MTC in this sense.) Of
course, feel free to file an enhancement request! You can do so at http://tracker.figure53.com/
.

(Tangent: In terms of subframe resolution, LTC displayed with timecode
bits can actually specify down to 1/80 of a frame, as opposed to MTC's
1/4 frame. QLab doesn't currently allow this, but if it would be
useful, that might be another candidate for an enhancement request.)

Best,
Sean

On Sep 20, 2009, at 3:46 PM, Drew Dalzell wrote:

> Drat.
>
> Is there any plan for this? I've been doing it for quite a few
> years in SFX and it will happily chase a clock and pickup from
> anywhere in the stream and then stay in sync or free run when I lost
> sync depending upon how it is set up.
>
> I'd even be willing to use LTC if it were the only way, though MTC
> is usually higher resolution since it actually goes down to
> subframes and SMPTE only specifies resolution down to frame.
>
> Drew

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