video sync offset - no quarter frame precision

[Gregor B.]

Dear All,

I am currently running into a strange issue with Pro Tools 2020.5 and video via blackmagic: Whenever I set the video sync offset in Pro Tools, I will only see changes for every 4 quarterframes. In other words, I step from 11 to 10 qf - no change, from 10 to 9 qf - no change, 9 to 8 qf - video will delay by a full frame.
This is confirmed with external devices such as Syncheck 3 as well as CathinSync. Will now continue troubleshooting in terms of drivers as wall as PT versions.

Meanwhile: Has anyone ever seen this behavior?

All the best,
Gregor

[Farhoof]

Originally Posted by Gregor B.

Meanwhile: Has anyone ever seen this behavior?

Yes, it's been like this since forever.

Could be different with an HD IO and video ref input.
Also, without video ref, every time you press play the sync might be a little different, but within a frame though. Based on personal experience, this changes depending on the Decklink driver version which has a dark history of being terrible.

[devinemke]

it has been explained to me by various Avid humans that if your Pro Tools system is locked to video reference (via the SYNC I/O for example) that your Video Sync Offset will always be rounded up/down to the nearest frame edge, thus no quarter frame granularity. the only way to have quarter frame accuracy is to not lock your system to video reference (using internal, or some other clock reference).

hope this helps

[Farhoof]

I don't have it locked to video ref on my edit rig. It is still rounded to whole frames. It's been like this since at least PT 8 HD and even on the old canopus firewire output (pre-decklink).

[Frank Kruse]

Originally Posted by Gregor B.

Dear All,

I am currently running into a strange issue with Pro Tools 2020.5 and video via blackmagic: Whenever I set the video sync offset in Pro Tools, I will only see changes for every 4 quarterframes. In other words, I step from 11 to 10 qf - no change, from 10 to 9 qf - no change, 9 to 8 qf - video will delay by a full frame.
This is confirmed with external devices such as Syncheck 3 as well as CathinSync. Will now continue troubleshooting in terms of drivers as wall as PT versions.

Meanwhile: Has anyone ever seen this behavior?

All the best,
Gregor

Hi Gregor,

same here. that's normal if your rig is fully gen-locked. You can't offset the video in between frame values when the clocking is forcing it to a full frame grid. I think it's even mentioned in the offset window (?). It will round to the nearest full frame no matter what you enter.

The remaining sub-frame error I compensate with the lip-sync delay in my speaker processor.

F.