SYNC HD clock source

[chuckbutler]

Greetings,

We have a SYNC HD on our system because we do a fair amount of ADR work and need to be able to generate or lock to TC when working with remote facilities.

Back in the day we were working with 3/4" and Beta decks, so we were using LYNX modules, with everything (including the SYNC HD) referenced to blackburst. But now we're working exclusively with QT movies; all the external video gear is gone.

My question is this: since we are no longer referencing the SYNC HD to blackburst, I'm wondering if there's really much difference between having the SYNC HD be the loop master and having, say, one of our (blue) 192 i/o's as loop master. Is there any significant improvement in the SYNC HD clock over the interface? I mean, if there is I can't really hear it, but maybe there are other issues I'm not considering?

Thanks for any thoughts.

[Postman]

Without a genlocked video output for QuickTime video, such as you'd get from MOJO or Blackmagic Decklink, and no external gear to lock to, and no need to varispeed, SyncHD serves no purpose. Video and audio will generally stay in sync within a frame (if you've got a recent cpu and the QuickTime movie codec/resolution is not overly demanding). Pro Tools will drag the video along with audio so there is not worry of long term drift. It certainly wouldn't hurt the AD converters jitter performance.

Operating that way makes lipsync a little too sloppy for my tastes but many people do it. It is very cost effective.

[matt-o-]

Originally Posted by Postman

Without a genlocked video output for QuickTime video, such as you'd get from MOJO or Blackmagic Decklink, and no external gear to lock to, and no need to varispeed, SyncHD serves no purpose. Video and audio will generally stay in sync within a frame (if you've got a recent cpu and the QuickTime movie codec/resolution is not overly demanding). Pro Tools will drag the video along with audio so there is not worry of long term drift. It certainly wouldn't hurt the AD converters jitter performance.

Operating that way makes lipsync a little too sloppy for my tastes but many people do it. It is very cost effective.

Is it still true, that while chasing to TC or generating TC ProTools syncs more precise (with Sync IO or HD)?

[Postman]

Is it still true, that while chasing to TC or generating TC ProTools syncs more precise (with Sync IO or HD)?

I confess I have not actually checked with PT10. It is certainly true in all earlier versions. Doing one of those things has always forced Pro Tools audio to be "frame edge" aware of an external video reference signal

[matt-o-]

Originally Posted by Postman

I confess I have not actually checked with PT10. It is certainly true in all earlier versions. Doing one of those things has always forced Pro Tools audio to be "frame edge" aware of an external video reference signal

Thanks. One further question: frame edge alignment to an external video reference only or to Quicktime Videos in floating windows as well?

[Postman]

external video reference only
QT floating windows are unpredictable on the sub-frame level. The "mechanics" of typical graphic card outputs, combined with the flexible treatment of video by QuickTime, defeats any attempts to align Pro Tools audio to video with subframe accuracy. Pro Tools cannot know exactly where frames edges are. Therefore when using a floating QT window, audio will be out of sync by a random amount of subframes.

[chuckbutler]

Thanks for the thoughts. Our work isn't critical enough that I'm worried about subframe accuracy. The SYNC HD does continue to serve a purpose, however, in that we typically act as "master" during ADR sessions, so the SYNC HD generates LTC that we send by ISDN to the remote ("slave") facility.

My question was more about clocking though, not about video sync. I just want to know if the clock in the SYNC HD is in some way superior to that in the 192 i/o.

[Frank Kruse]

It´s rather academical for but if you want to know exactly read this:

http://akmedia.digidesign.com/suppor...tter_30957.pdf

or take a short-cut to the conclusion on the last page.

[clusterer]

Originally Posted by Frank Kruse

It´s rather academical for but if you want to know exactly read this:

http://akmedia.digidesign.com/suppor...tter_30957.pdf

or take a short-cut to the conclusion on the last page.

hi frank,
the link is dead; could you please point to this pdf again? thnx!!

[Frank Kruse]

Originally Posted by clusterer

hi frank,
the link is dead; could you please point to this pdf again? thnx!!

weird. worked fine when I posted it.

here again

http://akmedia.digidesign.com/suppor...tter_30957.pdf

If that doesn't work paste the link into google. it should find it.