Sync problems

[the19thbear]

Hi. I have a Rosendahl Nanoclock HD, avid omni interface and a black magic decklink SDI.
I am working on a 1080/24 project.

The Rosendahl spits out Tri level sync to my black magic card. The black magic app says "locked" under REF in.
In the black magic app i have set the ouput to 1080/24
The Rosendahl outputs this as well.
My omni interface is recieving masterclock via WC from the Rosendahl as well. It locks up fine.

I have the "Sync-One2" box to check sync.
If i set my video offset in PT to "0", i and measure with the syncOne2, the sync is very solid, but always off with 296ms. I type that in and check again, perfect sync, only drifting about 001 ms up/down, coolness.

The problem is, if i do many measurements in a row, the start offset is different about 1 out of 4 times. And its off with about 40ms.
Everything is locked, it seems, and i can see that the sync is steady, but the offset changes.

All the tests have been made with the 1080/24 Prores files fomr synOne2. I have tried DNxHD versions as well. Same problem.

Any suggestions?
Thanks!:)

[Frank Kruse]

This is because you are not using an AVID Sync HD. This is the only way to get perfect edge sync lock between picture and sound in PT. The Sync HD communicates the timing to your PT session via the serial interface to the HD card (HDn- or HDX-card). In your setup this is not happening.

The random span (or offset) you are seeing is because picture and PT TC (start sample for when your clips are fired) are not aligned to the frame edge of your master clock.

I have the same setup but with a GEN10 and a Sync HD and I get the offset down to 1ms with zero drift or span.

So in your setup you won't see any drift even when you run your film for 24 hours or days but the start-trigger might not always be 100% edge-alined so that offset will stay till you stop and press play again. The error will be random depending on when exactly you press play. There's no way for your session to "know" which sample exactly is meant to be played at the edge of each frame coming because it doesn't "know" which sample of the WC belongs to which frame edge of the video. As a result the random error will always be between one sample and just below one frame. You can only achieve perfect sync when you feed your video-card AND ProTools with TriLevel sync via a Sync HD.

It has nothing to do with the video card or Rosendahl. It's simply because you are not using a Sync HD.

Your setup is definitely better than running video card and converter entirely free. You're system won't drift after you hit play but there will always be a certain statistically random offset between 0 and 1frame (the 40ms your are seeing).

Frank.

[the19thbear]

Makes total sense! Thanks a lot. I am setting up sync HDs in 2 other studios here, I'll let you know how it goes.
And wow. The sync Hd+ gen10+black magic is such a hassle to set up if you want to change frame rate. I can't believe avid hasn't made a box that has everything inside, and is software controlled! But that's another rant
Thanks for helping me out.


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[Frank Kruse]

Originally Posted by the19thbear

Makes total sense! Thanks a lot. I am setting up sync HDs in 2 other studios here, I'll let you know how it goes.
And wow. The sync Hd+ gen10+black magic is such a hassle to set up if you want to change frame rate. I can't believe avid hasn't made a box that has everything inside, and is software controlled! But that's another rant
Thanks for helping me out.


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Well you can control the Sync HD directly from the session setup window. The only annoyance is the Gen 10's DIP-switches (we call those a 'mouse piano' here in Germany). But since you own a beautiful Rosendahl that's much easier for you ;-)

98% of my work is 24P 1080P, some is 23.98 and vey rarely 25P so luckily I don't have to play the "mouse piano" on the Gen10 that often.

If you have to switch rates very often or even multiple time per day I wouldn't recommend a Gen10 anyway.

But with your Nanosyncs you're all set anyway...

F.

BTW: You don't have to switch the output of the BM around in the BM driver. That's just if you want to cross-convert the output. Just leave it set to no conversion. You don't need to set anything on the BM card when you switch frame rate.

[the19thbear]

Yup. The nanosync is easy:) I don't think we have any word for those switches in danish. But "musse-klaver" would definently make sense
The last couple of years we have been producing tv series in 25 frames, and now it seems like everything is shifting to 24. I think it's just the "in between" part that's bad.
But thanks again. I plan on working on the sync hds on Monday.
tschüss (that's pretty much all I remember from my German lessons)


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[smurfyou]

I just want to thank you, I'm going to start calling DIP switches a mouse piano. Makes them less annoying.

[Postman]

+1

"Mouse piano" ist Ausgezeichnet, thanks for that!

[the19thbear]

Hi again.

2 things:

1:
The rosendahl setup:
When i am testing with a 720 file, pro tools always still says 1080. Should i be bothered by that? It doesnt matter what output i set the decklink software to, in PT it still says 1080. This only happes with sync one2's test file in 720/24.
When i use a 720/25, pro tools reports correctly that the video is running at 720/25.

I have tested with other 720/24 videos, and its the same problem, so it doesnt seem like its a problem with sync one2s video file.



2:Another setup that consists of:
Sync HD. Aja Gen10. Avid omni. Black magic decklink.
I have the sync HD and omni loop synced.

I have tri level sync from aja gen10 going to sync HD "video ref in". It also goes to decklink "video ref in". Black magic software says "LOCKED" under REF in.
In pro tools i go to "session setup". I set "clock reference" to Video Ref. I set Positional ref to "auto LTC/VITC". Video "ref format" to 1080 - 24. "Video In Format" to PAL.

With my video offset set to "0" and reading with the sync-one2 i get readings from 391 to 420. And that is the offset. It seems like the "blips" are timed and in sync, but that the offset changes.

Everything on the sync HD seems to lock up fine. i get green lights at "REF present, "Locked" and a yellow light at "speed cal", which indicates that everything is ok. The sync HD is set as "loop master".

The only thing i can think of is "positional reference". That might be the issue. I have tried different settings, but no luck. I have pressed the "LTC", right next to the "MTC" button in the transport control, and it sends the right timecode to the sync hd, but only on start, and then the sync hd timecode stays there. They dont display the current timecode... but that might be a completely different thing. I dont care about displaying the timecode on the sync HD display. I just want everything to be in time.

Thanks again!

[the19thbear]

No one?
:)

[Frank Kruse]

Hi,

did you positively install the BMv10.4.3 driver? The 400ms offset sounds like you haven't. It's rather huge. (almost 10 frames). Mine is at about 100ms with 25P 1080P DNxHD36 QTs. But the exact number will also depend on the rest of your chain (projector, TV, splitters, repeaters in between etc.). Having a large offset isn't per se problematic but if you still have the new driver installed that can cause all sorts of other sync issues hence the question.

When you use 720 QTs you also need to set the master-clock to 720 and the Sync HD to 720 sync. They all have to match. Double check your DIP switches on the Gen10 again. The manual is quite confusing when it comes to the dip switches. But I guess you know that.
There's also a chance that the test-its you are using are weird.

I am currently using 1080P 25FPS QTs and my system locks to +-1ms and zero span.
Maybe your test-QT is encoded in a weird way. Try transcoding it again via QTpro.

A note about 720 24.00fps QTs: If I remember correctly the card can only output true 24fps when using 1080P QTs. This is info from many years back so I don't know if it's still the case. I never use 720 resolution so I can't say for sure.

Frank.