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Software Timecode etc.


curleysound

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This came from another thread. With all of the HD recording going on out there, a lot of mixers are now recording directly to Laptop computers. Of course, the folks with Deva, Cantaar etc. don't have this issue, but apparently the time clocks on computers are not accurate. I am wondering if anyone has attempted to make a timecode generator that creates code not dependant on the computers internal clock? I imagine that this could be done some other way, but I'm not a software engineer. In the mean time, we have denecke GR-1s and Ambients and Horitas, but what would be better than just pulling out the laptop or Mac Mini, a mixer and a mic, and running some software that has sample-accurate time code, and not needing anything else? Maybe someone has developed a replacement clock for them that can support that type of accuracy?

Tom

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You are correct that the Mac clock is way too inaccurate for sync work, as are the onboard clocks in MOTU etc interface boxes.  I've used either a Denecke SB2 or the TC output from a SD recorder (or, formerly, a TCDAT) to drive the MOTU box, which then puts the computer in sync w/ the code.  The TC in ths case comes to an audio input, and you tell the MOTU box which input to look at (in the set up page).  Metacorder can record TC coming from the Mac's audio input, and this will work fine if the FW interface is already clocked to that code. 

Really--do not rely on the computer's internal clock (what you mean by Boom Recorder's own TC generator) for any recording you have to sync to anything else. I've been burned by this--it really does not work.  You must clock the interface you are using to a much more stable clock than that of the computer.

Philip Perkins

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Hello Tom,

I agree with Philip. Using the internal clock for timecode generation would have a lot of jitter, even when you feed the computer a GPS time signal or better. The jitter will be around 2 ms for Linux on PC hardware, which would not be nice for timecode signals.

One could generate timecode with as basis the sample rate of the audio device like the MOTU, but as Philip explains, on its own MOTU devices although having low jitter, is not accurate and will drift continues from the wall-time clock.

If one would have a audio interface that has an non drifting sample rate clock, or a audio interface clocked with a word clock. It would be possible to generate a good timecode signal.

Cheers,

  Take

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Ambient has a new device that looks very promissing for this application: LL-601 "Lanc Logger".

Watch it at the NAB video, part 3, near the end:

http://www.recordingartsforum.com/ubb/Forum25/HTML/000002.html

LANC ---> MIDI TC

MIDI TC ---> SMPTE TC

And it has a LockIt inside

I guess it can also do LANC ---> SMPTE TC

It writes a log report from the takes on the camera too! It lists the TC of all takes I guess.

No sudoku in it.

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You are correct that the Mac clock is way too inaccurate for sync work, as are the onboard clocks in MOTU etc interface boxes.  I've used either a Denecke SB2 or the TC output from a SD recorder (or, formerly, a TCDAT) to drive the MOTU box, which then puts the computer in sync w/ the code.  The TC in ths case comes to an audio input, and you tell the MOTU box which input to look at (in the set up page).  Metacorder can record TC coming from the Mac's audio input, and this will work fine if the FW interface is already clocked to that code. 

Really--do not rely on the computer's internal clock (what you mean by Boom Recorder's own TC generator) for any recording you have to sync to anything else. I've been burned by this--it really does not work.  You must clock the interface you are using to a much more stable clock than that of the computer.

Philip Perkins

100% Correct.

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