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cross jamming tc


Jack Norflus
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I was in a situation today where I had one camera not accepting 29.97nd TC while all the other were accepting in. It would however only take 23.98.

So essentially cross jamming the TC.

Then I started second guessing myself and I started looking into crossing jamming and how it works and why or why not this is a good choice. Then and I started looking to get more info on cross jamming and i couldnt find any good solid clear information on cross jamming.

Any enlightenment or links would be great. I don't need or want any info about how or why the camera wouldn't accept 29.97 I'm curious about cross jamming.

Thanks

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Hey, Jack:

most devices actually jam on the :00 frame of a second.

the integer frame rates are all cross-jam compatible, they just divide a "second" into different numbers of frames.  the same for the non-integer (.1% pulled down) TC rates, they have a slightly different "second", a little bit longer, but still jamming on the :00 frame, while theyare dividing that "second" into different fractions (frames)

 

disclaimer: there may be some devices that are more "fussy", and won't accept a jam from a different frame rate.

further disclaimer: workflow test advised

Edited by studiomprd
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Yes, although I've never tried 25>30, not sure how that would come up.  However there is still the issue of how the TC you are making will be used.  Ballpark ref for a manual sync?  OK.  Auto sync in Resolve etc--some trouble.  And there will still be issues with having clips with differing frame rates in the project when they export for audio post.  None of this is your problem--the camera is not working properly, so the cross jam is the best you can do as far as I know.

 

philp

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Yes, although I've never tried 25>30, not sure how that would come up.  However there is still the issue of how the TC you are making will be used.  Ballpark ref for a manual sync?  OK.  Auto sync in Resolve etc--some trouble.  And there will still be issues with having clips with differing frame rates in the project when they export for audio post.  None of this is your problem--the camera is not working properly, so the cross jam is the best you can do as far as I know.

 

philp

BINGO.. Cross jam attempt on Red Dragon= manual approximate sync, and grumbles from Post on show using Resolve 10 to create dailies

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NFL Films records audio at 29.97NDF, but all there cameras (no longer shooting film) Arri Alexa, F55, Amira shoot at 23.98 and will barf at any other code into them. Standard OP is to set recorder at 29nd and Denecke sync box at 23.98 and cross jam.

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Cross Jamming should not cause much intestinal distress.  Either 23.9  or 29.9 will allow for a solid sound sync regardless of weather sound is at 23.9 or 29.9.  Ambient Lockits are quite happy cross jamming, and understanding that the Arri Alexa/Amira/Amigo/Adios have Ambient innards in their TC generators will be quite happy cross jamming from/to 29.9 or 23.9.   May I suggest that we do an empirical test to assure these assumptions.  Test, Prep, Shoot as decreed by a celestial deity.  Ownership of these concepts is pretty easy to come by.... please test test test.... great comfort will smother you in down quilts at the end.

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I agree, but in cases like that fire breathing red dragon, its the only way so far ive been able to get the happy green tc with an erx. I believe cross jamming could help with erx's or any sync boxes where cameras have problems accepting them. If your recorder and camera are both set to match tc rates like 23.98 for example, cross jam the box for the camera to 29.97 and see if you get success.

Ken

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Resolve 11 allows manual syncing (like in an NLE), this will not cheer DITs and Asst. Editors who have to do that work (manually) within time-budgets written for autosyncing….

 

philp

In network drama series world you do not EVER update software/firmware during a season.  The manual syncing is an often performed fix when Resolve and the Arri metadata don't communicate perfectly.  which is several times a week on a two camera scripted show.  They tested several Dragon and Non Dragon Epics as potential alternate/extra/vfx cameras... and were very unhappy about the TC prospects.  Workarounds are not desired, conformity to offsite post workflow is required.

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Cross Jamming should not cause much intestinal distress.  Either 23.9  or 29.9 will allow for a solid sound sync regardless of weather sound is at 23.9 or 29.9.  Ambient Lockits are quite happy cross jamming, and understanding that the Arri Alexa/Amira/Amigo/Adios have Ambient innards in their TC generators will be quite happy cross jamming from/to 29.9 or 23.9.   May I suggest that we do an empirical test to assure these assumptions.  Test, Prep, Shoot as decreed by a celestial deity.  Ownership of these concepts is pretty easy to come by.... please test test test.... great comfort will smother you in down quilts at the end.

 

I don't know what you said, but I like the way you said it!

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Rob, just curious as to the particular situation you were experiencing problems with the F55. I worked with one yesterday and it took a jam from my 664 at 23.976 no problem. I was hard wired to it for timecode and audio. It was a full day of sit down interviews no mobile shooting. I have not yet worked with an F55 where I had to attach my sync box.

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