Sound/video desynchronization in playback

[LST]

Hi there,

I solved the problem. By opening a case with Avid Customer care, I was advised to downgrade the Video Desktop BM driver to the version 11.4.1, and miraculously everything became stable and working with the SYNC X and the Decklink Studio 4K

So, I did a replacement of the SYNC X by my MUTEC iclock dp in video ref and in word clock, for check the sync and it's work !

To finish, i tested severals video codecs (prores 422, prores 422 proxy, DNx36,...), it's work too !

I will keep an eye on this in the next few weeks in case it goes adrift again.

Anyway, thank you for your help,

I hope that this topic will be useful for other users of Pro Tools !

Regards,

LST

[Frank Kruse]

Yeah, see post #7 of this thread about BM v11.4.1.
Glad you got it sorted.
I still don't understand how you genlock the card with PAL BlackBurst but maybe that card is able to cross sync SD PAL to HD Video, not sure. My BM card will not gen lock HD QT to PAL BB but whatever floats your boat...

Does the BM Desktop video setup menu say "LOCKED" under the Ref Input menu? I'm curious.

The fact that's still valid from what I wrote earlier: Your PT rig will not lock/sync to your master clock without a SYNC HD or SYNC X involved. Which is not a problem per se unless you want 100% sync with zero drift but you could actually lose the Mutec altogether as it's not really doing anything. PT is ignoring that clock the way you have set that up at the moment. Yes it's clocking the audio interface of but PT will still not align the audio to the video frames. It needs the SYNC HD oder SYNC X to know that.

Frank.

[LST]

Hi Franck,

I think that the Decklink Studio 4K is able to cross sync SD PAL to HD video because in BM Desktop Video Setup menu say "LOCKED PAL" under the Ref Input menu..
Anyway, you're right on Sync X / Sync HD with PT. But I think that my setup haven't need external sync because all is "in the box". There are no machines to work with satellites mode. So basically, I think that can I disconnect the MUTEC because I don't need external sync and all should work with MTRX internal clock.
Don't you think?

LST

[Frank Kruse]

That's great about the BM card. Didn't know the 4k can do that.

But yes, you'd need a SYNC HD for that or a SYNC X. Without these units your PT will simply run in start trigger mode and be within a random amount +- of about one frame every time you hit play.

So wether you run the Mutec or not should not make a difference in terms of video/audio locking as your audio is essentially started at a "random" point around the exact frame edge.

Generally: PT will *only* sync audio 100% to video frame-edges with the SYNC and when using video ref as the clock source. There's no other way for PT to "know" when a frame edge is played back by your video card. PT needs that info in order to play your audio with the same timing on that grid every time you hit play.

Wether or not you want 100% frame accurate sync is up to you. In your current setup losing the mutec should make no difference.

[smurfyou]

I think Frank and I have both said it but here it is again.

You need the SYNC-X / SYNCHD to be certain you have frame sync. It's the only way.

IMO You have a console, a serious IO, and a projector. Big investment that would be a shame to have unreliable sync. Don't think of it as locking to external sync. You're correct you don't need that. It's locking Pro Tool's timeline to your video output. Lock that, figure out your offset with your preferred codec using Sync-One2 (or Catchin' Sync). Then you won't have to worry about what you're seeing and hearing.

[LST]

Hi,

Thank you Franck and smurfyou for your advice and for your help. I take note and I put it in a corner of my head.

See you on an other topic!

LST