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  #1  
Old 02-18-2015, 08:28 AM
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reichman reichman is offline
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Default Video Sync Offset in PT11 not that useful

In the reference manual it says:

"When using a video peripheral which is locked to video reference, offsets will be rounded to the nearest full frame."

The Syncheck reveals this to be true, but with an AJA T-Tap (not a genlockable device) it is also true. In my project studio, settings of zero get me under 0.1 frames discrepancy (pretty good). But in our main studio, Syncheck reports a consistent 0.4 frame, or about 20ms discrepancy. You can't correct for this using the video sync offset window! So I resorted to using a Time Adjuster plug-in on the 5.1 monitoring bus. A little weird.

That's the bad news. The good news is that PT11 without genlock is much, much tighter than PT10 without genlock. The Syncheck results suggest that you don't need to genlock if all you're doing is playback.

Using a Mac Pro 6,1, PTHD 11.3.1, and an AJA T-Tap.
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Last edited by reichman; 02-18-2015 at 10:44 AM. Reason: Time Adjuster, not Time Delay
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  #2  
Old 02-18-2015, 09:59 AM
tom_lowe tom_lowe is offline
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Default Re: Video Sync Offset in PT11 not that useful

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Originally Posted by reichman View Post
In the reference manual it says:

"When using a video peripheral which is locked to video reference, offsets will be rounded to the nearest full frame."
hasn't that always been the case? Good that PT11 without genlock is good enough for playback.
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Old 02-18-2015, 10:42 AM
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reichman reichman is offline
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Default Re: Video Sync Offset in PT11 not that useful

Yes, I think that always has been the case, but my discovery was that even the cheapo AJA T-Tap without genlock is rounding to the nearest frame. If you have a subframe discrepancy, you must use Time Adjuster, you can't use the Video Sync Offset window.
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Old 02-18-2015, 11:22 AM
tom_lowe tom_lowe is offline
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Default Re: Video Sync Offset in PT11 not that useful

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Originally Posted by reichman View Post
Yes, I think that always has been the case, but my discovery was that even the cheapo AJA T-Tap without genlock is rounding to the nearest frame. If you have a subframe discrepancy, you must use Time Adjuster, you can't use the Video Sync Offset window.
Ah that is odd. I wonder if it's getting some sort of clock from the T-Tap. be interesting to see if the same happens with Blackmagic Intensity range which also have no ref.
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Old 02-21-2015, 02:31 AM
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Default Re: Video Sync Offset in PT11 not that useful

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Originally Posted by reichman View Post
Yes, I think that always has been the case, but my discovery was that even the cheapo AJA T-Tap without genlock is rounding to the nearest frame. If you have a subframe discrepancy, you must use Time Adjuster, you can't use the Video Sync Offset window.
We consider to transfer one of out room to MP 6.1 too. So it might be more general rather specific your system question.
Have you contacted Aja about this issue? Their support is pretty good.
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Old 02-21-2015, 10:27 AM
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Post Re: Video Sync Offset in PT11 not that useful

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Originally Posted by tom_lowe View Post
hasn't that always been the case?
When playing back via a video peripheral, yes. Whether it is PT 10 with the QuickTime video engine or PT 11 with the Avid Video Engine, the offset is always rounded to the nearest whole frame. This means that there is +/- 0.5 frames of error. Research has shown that erring on the side of having video lead audio is less distracting than having audio lead video.

Just remember to not use that TimeAdjuster when bouncing to QuickTime or laying back to tape. Otherwise, your deliverable could be out of sync.
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Old 02-27-2015, 08:20 PM
cananball cananball is offline
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Default Re: Video Sync Offset in PT11 not that useful

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Originally Posted by Chief Technician View Post
When playing back via a video peripheral, yes. Whether it is PT 10 with the QuickTime video engine or PT 11 with the Avid Video Engine, the offset is always rounded to the nearest whole frame. This means that there is +/- 0.5 frames of error. Research has shown that erring on the side of having video lead audio is less distracting than having audio lead video.

Just remember to not use that TimeAdjuster when bouncing to QuickTime or laying back to tape. Otherwise, your deliverable could be out of sync.
Silly to offer quarter frame adjustment if it's just going to round it to a full frame.

That being said I've found the quicktime sync via a BM card so consistent when properly offset I feel no need for genlock, especially if while genlocked it's still going to round off. I can get it within a 16th of a frame consistently without it.
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Old 02-28-2015, 10:22 AM
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Post Re: Video Sync Offset in PT11 not that useful

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Originally Posted by cananball View Post
Silly to offer quarter frame adjustment if it's just going to round it to a full frame.
You get quarter frame accuracy with Pro Tools v10 if you playback in the QuickTime video window on a computer display. Otherwise, the offset is rounded to the nearest whole frame.
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Old 08-03-2015, 01:50 PM
Burmansound Burmansound is offline
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Default Re: Video Sync Offset in PT11 not that useful

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Originally Posted by tom_lowe View Post
Ah that is odd. I wonder if it's getting some sort of clock from the T-Tap. be interesting to see if the same happens with Blackmagic Intensity range which also have no ref.
I finally got around to checking our PT 12 systems with the Syncheck II. We use the Blackmagic Intensity Pro cards, and the result is very stable. With our previous setup, the Canopus with PT 9, it was all over the place, sometimes locking almost a frame out, and constantly drifting. Now it is stable within a ms or 2 with no genlock. Adjusting milliseconds, it doesn't change until you go above or below 20 ms. Anything between -20 and +20 keeps it at zero. At a setting of +21 ms, Syncheck reads +32 ms (about 1 video frame). At a setting of -21 ms, Syncheck reads -49 ms (a little over 1 film frame). We have delay for our projector built into our B-chain (crossovers), so the 1 frame resolution isn't a problem for us. When I first saw the ms setting, I thought "This is awesome!" Too bad it doesn't work.
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Old 08-03-2015, 09:49 PM
ggegan ggegan is offline
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Default Re: Video Sync Offset in PT11 not that useful

I thought I read somewhere that slaving both the Sync HD and a video card to a reference signal in PT11 and 12 locks the audio and video to the frame edge. If that is true, there would be no need for quarter frame adjustments.
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