Blackmagic Decklink offsets. SYNC.

[twopike]

DUC,

I recently "upgraded" from using the DVI output of my macpro (intel xeon quad; 10.5.8; PT HD7.4.2) to feed the projector. Pro tools video offset set to 4 quarter frames for the frame delay in the DLP. OK, picture quality not bad, sync not bad but variable colours are wrong this is a mac graphics card/quicktime issue i am told FINE. I wanted proper genlocked High quality HD picture like grading quality due to client expectations. I know about the little Matrox box that will deal with colours but still it is not frame edge aligned.

SO, now we are os x 10.6.3 HD 8.1cs2 same machine but with a blackmagic decklink the 3D one. My DLP has DVI in only so SDI out decklink through a blackmagic SDI-DVI converter gives me picture (HDMI out does not work with my projector colour spacing issues agin).

The problem is SYNC. The offset for every single combination of quicktime codec/framerate/resolution is different. Even if I restrict acceptable file types to the top four (Apple pro res, DnX, M/P jpeg, DV) and assume they will always be at 720p so I don't have to resize in blackmagic prefs (which will alter the latency) I still have 23.98, 24, 25, 29.97, which means 16 different offsets to syncheck plus in reality 720, 1080, 576, resolutions which makes 48 possible offsets which is completely insane.

I am hoping that something is vastly wrong with this because even if I did grind my way through these tests and compile a chart we often receive odd file types and have no time to recode them and are stuck having to guess the offsett. VERY unprofessional. I thought the decklink would really improve the studio but it has made it endlessly complicated and we are constantly insecure of sync.

I am hoping that somebody else has a clever work around or a better way of working or a better software arrangement for my setup. I read that 10.6 has not been good for video, there are also many firmware versions for the decklink card etc...

The expensive video options are out (V cube meridian etc) so I need to make it work with what I have really.

thanks

[Danny Caccavo]

One thing I *can* tell you about the Blackmagic card is that if you have it genlocked, the "Video Sync Offset" setting in Pro Tools behaves oddly. Essentially, you can only offset by one frame at a time - changing the quarter frame adjustment by one or two will sometimes make it lock up a frame earlier or later, depending.
What you have to do is find the "sweet spot" where the sync is consistent (and at or slightly behind the audio), stick to that Video Sync Offset, and delay your audio monitor path to make it perfect.

dc

[twopike]

Thanks Danny,

that has made it harder to work out, it wants a frame edge one side or the other if you try to give a half frame offset it will be jumping between no offset and one frame. I have decided to just stick to one codec (apple pro res 422) work out the offsets for each frame rate and put up with it. I don't believe in offsetting audio (I know this is very standard practice) but I think a fader movement should not have a delayed result no matter how small. We sometimes run into automation issues that do just that (AMS-DFC) so I like to feel certain of that fact. Why are there no digital video delay units on the market that can do subframe delays??

(please let me know if there are!)

[EvilTuna7]

Bumping this thread.

Having the same issue as twopike mentioned above. Every different frame rate requires a different video offset and beyond that, sessions with higher system delays (more tracks and plugins) require a different video offset compared to a smaller session, even when they both have the same frame rate. Any help would be much appreciated!