What happens when a device is Jammed with TC?

[SonicBoomPole]

Fine people of the internet I pose this scenario to you:

 

I own a MOTU Traveler MK1, not MK3. It claims it will "resolve" to SMPTE via any audio input and send out SMPTE via any output.

 

The software it ships with, the MOTU Firewire SMPTE console, controls all of the SMPTE options as you'd imagine. The frame rate selection does not include 23.98 fps but only 24, 25, 29.97 DF/NDF or 30 DF/NDF. Digital Performer 5 also has this same limitation as does my older version of Nuendo.

 

I also own a 664. I have jammed the Traveler from my 664 at 23.98 fps and it seems to hold sync for an hour or so in my brief test when the Traveler is set for true 24 fps SMPTE. I have yet to try to jam the 664 from the Traveler to confirm that is stays 23.98 out of the MOTU but that is my main question.

 

I know this is not technically correct. I was curious if, despite the settings, that the MOTU actually just accepts the incoming external TC as is and outputs TC according to the source or if it forces a true 24fps flag on the stream.

 

Basically I'm wondering what actually occurs when one device jams another with TC. Is it the source that sets the stream or the receiving end that confirms/interprets the stream or both.

 

Any insight would be really helpful. I've searched Google and this site (via Google) and have not found the specific answer to my question. Thanks!

 

 

[studiomprd]

" 30 DF/NDF. "

danger:  there is no SMPTE/EBU standard for any 30DF timecode; there are several proprietary implementations...

 

" I know this is not technically correct. "

you are technically correct...

 

" if, despite the settings, that the MOTU actually just accepts the incoming external TC as is and outputs TC according to the source or if it forces a true 24fps flag on the stream. "

that would be <old cap>

" what actually occurs when one device jams another with TC. "

assuming (    ) proper implementation of SMPTE/EBU standards, and proper operation...

the jammed unit accepts and adopts the incoming timecode value as its own, and continues generating its own TC from that value,  although it continues to use its own settings (rate)... the "jam" occurs at the 00 frame of a second

[Philip Perkins]

All that's happening in the sort of jam you are doing is that the internal TC counter of the MOTU box adopts the current TC address of the incoming ext TC as its current TC time and counts on from there.  The Traveler, having an internal clock that is not at all accurate, won't "hold" the jam you just did for more than a few minutes exactly if you disconnect the TC after the jam.  If you leave the external TC hooked up to the Traveler, AND you tell it to make the TC its clock source then it will stay in sync with the external device (like yr 664) indefinitely--I did recordings of over 3 hours this way with up to 4 MOTU boxes taking EXT TC from a 744 or 702, and the sync was perfect.   A more proper way to do this would be to feed the Traveler BOTH TC and WC from your 664, and have the Traveler clock itself to the incoming WC.

 

philp

[SonicBoomPole]

Mike, I had planned on contacting MOTU today if I didn't get anything here. Though I hear that their support is less than stellar. I guess my 30 fps was a typo or brain fart, please excuse me sir. Thanks for clearing things up.

 

Phil, thank you so much! That is exactly what I was hoping to get in the way of an answer. I was hoping you'd chime in on this.

 

I was assuming that the traveler would default to its own settings unless TC was constantly being fed to it in addition to WC as Phil stated above. Good to know that is an option that works. Reading up on old posts here I'm well aware that the clock in the MOTU is far from accurate when compared to the 664 or similar. I was hoping to be able to use the Traveler to provide TC for music video playback shoots or live concerts.

[Philip Perkins]

I would not recommend using the Traveler TC for concert work--long term clock accuracy is not something it can do w/o a stable ext WC signal.

 

philp