Drifting Video offset

[HDXSound]

Hi,

I'm experiencing drifting video sync offsets when working on my rig (large audiopost sessions). It varies from 8 to 14 quarter frames.
I run on internal clock source which might be causing this.
All my video is on a separate SSD harddisk.
And i use the AJA IO Express for video with DNXHD Prores Proxies.
DNXHD36 give me worse results.

Would buying a Avid Sync HD IO solve my issues?
Would i need to connect the sync IO to the AJA Express?
Can someone chime me in on the best way to fix it?
Thank you!

[Frank Kruse]

Just buy an AJA card and your problems will go away. Oops, you already got one, sorry.



Just kidding obviously.

The only way to ultimately fix this is to genlock your rig with a SYNC HD and feed it and your video card a common tri-level sync signal.
Anything else will always be "more or less" sync. Thing is: Does the AJA Express have a sync ref-in at all?

But I must say the span you are seeing is quite big between 8 and 14 qf. Keep in mind you will get different offsets for both different codecs AND frame rates AND resolution. Even different settings on your TV/projector can cause different offsets.

Frank.

[HDXSound]

Thanks!

[Frank Kruse]

That said, you will still get different offsets for different codecs, frame rates, resolutions even when everything's genlocked.

The SYNC HD will only prevent the system from drifting and will bring the start error down to sub-frame (near sample) accuracy. The offset however will stay and will be different for every format. There's no way around that.

F.

[Schottlandru]

HDXSound,

as I have been experiencing a weird variable video sync offset issue myself, the next time to fire up your session and it is a NEW offset again - could you please to to the Playback Engine settings, change your disk cache settings, press OK, and measure again?
Does the offset change?
I've had this issue for a while - anything from 30ms (which used to be my standard with DNxHD) to 50, to -30 to ...

Changing the playback engine settings/disk cache or even just opening and OKing that menu seems to "recalcualte" PT internal playback latencies.

DLY compensation and Session Delay however all remain the same.
It might be a plugin. Bouncing/rerecording all happens in sync though, so it seems more like flakey video buffers or whatever...

This is with desktop video however. On a Win10 machine. I am a rebel, yes.
(Happened on Win7 too. Oh and it's PT11 as well as 12).

Haven't opened a support case... yet... But have posted here on the DUC before and it seems a rare issue. Or maybe rarely discovered...

Andrew

[quadraphonics]

Do you have a SyncIO or Sync HD?

Originally Posted by Schottlandru

HDXSound,

as I have been experiencing a weird variable video sync offset issue myself, the next time to fire up your session and it is a NEW offset again - could you please to to the Playback Engine settings, change your disk cache settings, press OK, and measure again?
Does the offset change?
I've had this issue for a while - anything from 30ms (which used to be my standard with DNxHD) to 50, to -30 to ...

Changing the playback engine settings/disk cache or even just opening and OKing that menu seems to "recalcualte" PT internal playback latencies.

DLY compensation and Session Delay however all remain the same.
It might be a plugin. Bouncing/rerecording all happens in sync though, so it seems more like flakey video buffers or whatever...

This is with desktop video however. On a Win10 machine. I am a rebel, yes.
(Happened on Win7 too. Oh and it's PT11 as well as 12).

Haven't opened a support case... yet... But have posted here on the DUC before and it seems a rare issue. Or maybe rarely discovered...

Andrew

[HDXSound]

I can verify the offset changes when messing with the playback engine but that would expected behavior right?

@quadraphonics i have either. I run internal clock.

[Frank Kruse]

Originally Posted by Schottlandru

HDXSound,

as I have been experiencing a weird variable video sync offset issue myself, the next time to fire up your session and it is a NEW offset again - could you please to to the Playback Engine settings, change your disk cache settings, press OK, and measure again?
Does the offset change?
I've had this issue for a while - anything from 30ms (which used to be my standard with DNxHD) to 50, to -30 to ...

Changing the playback engine settings/disk cache or even just opening and OKing that menu seems to "recalcualte" PT internal playback latencies.

DLY compensation and Session Delay however all remain the same.
It might be a plugin. Bouncing/rerecording all happens in sync though, so it seems more like flakey video buffers or whatever...

This is with desktop video however. On a Win10 machine. I am a rebel, yes.
(Happened on Win7 too. Oh and it's PT11 as well as 12).

Haven't opened a support case... yet... But have posted here on the DUC before and it seems a rare issue. Or maybe rarely discovered...

Andrew

Hi there,

actually you will get all sorts of offsets **every time you hit play** when your system is not genlocked. The 30ms to 50ms is the typical +- around 1 frame start error.

anything around +- 1 frame (40ms) is normal for a non-genlocked system. PT and the card can not know when exactly to start the picture relating to that exact audio unless you clock them with a common master-clock.

When you genlock everything you will STILL get an overall offset but it will be constant for a given QT format and frame-rate.

F.

[Schottlandru]

Neither sync I/O nor HD here.

HDXSound, why would opening and closing the playback engine settings mess with the current offset? If I am only changing disk cache at most?
Buffer stays the same, same driver, same all.
Something is screwing with the internal timing, even without changing anything.

I see that as a real issue - it can (and has) happen(ed) mid session...


@Frank - I get your comment and know what you are getting at BUT I have consistent sync within +- 10-20ms (that is 1/4 to 1/2 frame) whenever I hit play. Actuall more towards the 10ms side of it. This same offset stays until I change the playback engine settings. Or reload the session.
(This didn't use to be that way, was better with older 11 and 10, I remember - but that was older systems and drivers too.)
I know what you are getting at with the "non-referenced" system - BUT since my video output is 60Hz (desktop), it means it is not +- 1 frame but rather +-1/2 to 1/3. Thus my roughly 15ms jumping sync.
I can live with that very well actually as playback is smooth when editing once the general offset has been corrected.

This is another issue. It is inconsistent offset, a 'constant' offset, with ever session / engine initialization. And it has been as much as 80ms difference from session to session - same project.

[HDXSound]

Sphottlandru, i'll check first thing in the morning.
I do know the offsets do vary for me upon each start.
Changing playback engine crashes my session, do need 1014 cache and 256...
Ordered a sync HD and AJA today.