Sound/video desynchronization in playback

[LST]

Hi,
First of all, excuse my English, I hope I'll be understandable... I have a mixing auditorium with :
- Avid S4
- Avid MTRX in video ref
- Avid NEXIS
- MacPro with macOS Catalina
- Blackmagic Design Decklink Studio 4K
- MUTEC iclock dp (video ref)
- JVC video projector

I explain my problem to you, I work with a sound engineer for film mixing and here is the history of what happened :

First thing a little bit strange...
- Copy of the video on the NEXIS, copy session on intern SSD and opening session : ProTools frozen on opening without error message, nor milling...
- New session, import session data : same
- New session, import session data without video, and import video on NEXIS in a second step : PT OK

Here the big problem... :
Sound/image desynchronization on a continuous reading (8 to 12 de-synchronizations suddenly on a 1h50 reading)

Buffer size: 1024 samples
Delay Compensation : On
I restart iclock + MTRX + Mac : same result.
I uncheck GPU Enable in ProTools preference : same result.
Test with an Apple ProRes 422 video, Apple ProRes proxy, DNxHD video: same result.
I tried to pass the video track from FULL Quality to 10bit quality then to Draft : same result.
I can open the Decklink Video Setup preferences from the video track in ProTools, and the video ref is locked to PAL.
Changing the Decklink Video Setup “default video standard” setting to 1080p50 instead of 1080i50: same result.

I tested with another session, another film: everything works fine
Test in sound editing (mac mini) : work fine, so the codec video is fine.

Another problem maybe related...
Video doesn't start sometimes when starting playback, it remains frozen, it starts on the second playback start.

When the video freezes on the videoprojector, it also freezes in the video window of the PT (cmd+9)

I would like to Update 12.2.2 of the Decklink 4K Studio: would correct a problem preventing the synchro start of playback but not Catalina compatible and therefore protools...

Can iClock be at fault? Settings rather vague on the SD/HD settings... Not a lot of menus... but the settings/connections seem coherent.

Globally, I have big doubts about the Blackmagic video capture card...

Do you have any ideas ?

I remain at your disposal for any further information. Thanks in advance everyone !!!!

LST

[smurfyou]

I’m not sure the iClock is doing anything for you. I don’t think Pro Tools will lock to any video ref except Sync HD or Sync X.

Even without video sync there should be no drift. Only a slight sync offset for every play. But Decklink cards especially with older Blackmagic software were notorious for random sync drift. I’m not sure which versions are acceptable. Hopefully somebody else can chime in. I switched to Aja.

That still does not explain Pro Tools freezing upon loading video from Nexis. There can be some stuttering and dropped frames if it is a high bitrate video and your bandwidth is suffering. I don’t know what could cause the freezing though. Do you have another SSD so you can play video locally?

[LST]

Thank you for your response. For me, iClock is a Ref Video HD.

I can try to play the video on another SSD locally, indeed. But I don't think it will be better.

But yes... I think that AJA would solve all my problems...

[Frank Kruse]

As been said:

Without a SYNC HD or SYNC X your ref generator is not going to do anything. It might be feeding a clock to your video card but PT won't lock to it without a SYNC interface attached and set to video ref.

But it sounds like you are using a PAL sync signal (old school black burst) for the BM card or did I misunderstand?. Just asking because when running HD the card wants to see a trilevel HD sync signal, so maybe that's cause your problems? Just a thought. I think your MUTEC box is an old black burst generator, no? If yes I would disconnect that entirely and try again.

[fork-media]

having suffered similar issues I found Video Sync by non lethal applications very useful - you can try it for free for 14 days

may solve your problems.

[LST]

Thank you for your response.

So, for you MUTEC iclockdp is useless ? Indeed, the clock uses a PAL sync signal for the Decklink BM and you're right... in Session setup ProTools > Sync Setup > no avid synchronization peripheral present.

The link for the iclock manual : https://www.manualslib.com/manual/13...ec-Iclock.html

Here are the iclock settings (generator sync) :
VIDEO OUT1 & VIDEO OUT2 :
REF : INTERN
FORMAT : PAL
VIDEO TYPE : BLACK + BURST
SD/HD Video Out 1 is connected to MTRX
SD/HD Video Out 2 is connected to BM Decklink Studio 4K

Here are the DADman (MTRX) sync. settings : LOCKED
Sync source : Video
Sync out : Work Clock
Sync term : High Z
Digi dli (smpls) : 5

I did a lot of other tests today.

1_try to switch "REF : INTERN" to "REF : HD-P-1"

2_completely disconnect the MUTEC iclock and switch to the DADman (MTRX) sync source in "internal" mode, instead of "video ref"

3_increase cache size to 54GB instead of 40GB in playback engine (ProTools)

4_disable compensation delay in Pro Tools

5_Desktop Video Setup 12.2 not being Catalina compatible. I close Pro Tools, uninstall Desktop Video Setup 12.1, and downgrade to 11.7

I still have to try to play the video on another external SSD and try Video Sync by non lethal applications, but I'm starting to despair. I feel like I'm going to have to change the iClock to a SYNC X and change the BM to an AJA !

Thank for your help !!

LST