I am trying to output 4 signals via SDI over a Blackmagic Decklink 8k Pro card, then into 4 separate projectors at 1920x1080. I have a Blackmagic Multiview 4 in-line to see a reference for each output, and today I noticed that the 4 outputs were not synced up. I have a couple of questions:
Is it more efficient to output 4 individual 1080p signals on 4 separate Video Device Out TOPs, or 1 4k signal using quad-link to a single Video Device Out TOP? Would the latter solve my sync issues?
Is it necessary to add a Timecode CHOP within the Video Device Out TOP? And if so, is a Clock CHOP and a Timer CHOP into a Select CHOP (renaming channels to ‘hour’, ‘minute’, ‘second’, and ‘frame’) the correct way to do this?
Additionally, if going with a single 4k image and quad-lock the Video Device Out TOP/SDI outputs is the better method, is there a good method for cropping 7680x1080 content to fit onto a 3840x2160 screen? I was experimenting with a Grid SOP and splitting it into 4 quadrants, then using a Light COMP to project a part of the image onto each quadrant, though I can’t get it to work and I’m wondering if there is a better method.
First, I am not sure that the best method to output four HD stream would be via video out device Top.
I would prefer a proper graphic card, outputing four HD 60 fps image or 1 UHD image splitted in four HD with a window Comp, thats the usual method in TD.
Black magic card are good if you want to be sure about the norms of the video (Rec-709, 23.97 fps etc.) but not so useful to project multiple videos. I you need long cable, its better to use HDbaseT via RJ45.
Second, the process of using a Grid Sop with light Comp seems very complicate for a simple task.
I would use crop Top and resolution Top to resize image.
Its easier if you publish a capture of your project and what is your system (laptop/desktop, mac/Windows, AMD/nVidia etc.)
Have a nice day,
Hi Jacques, thanks for the response. My system is the following:
i9 10900X (3.7Ghz)
RTX A4000 (16GB RAM)
Blackmagic Decklink 8k Pro
Running Windows 11
I hadn’t considered HDbaseT since I’m not very familiar with it. The Decklink SDI out requires the least amount of conversion since my projectors will be SDI in. They have an option for HDbaseT, so I will have to explore that a little bit, but like I said I have very little experience with it and I wouldn’t know the best box(es) to get.
I think you’re correct that my Grid SOP and Light COMP method is overcomplicated.
The easiest way (for me) would be to use one output of your A4000 with your UHD composite.
Depending of the cable length, I would use HDMI (max 20 m) or HDbaseT (max 100m) and a splitter like Datapath to obtain four HD images in perfect synch.
Concerning the crop, here is a simple example of what can be done.
cropUHD.toe (3.8 KB)
Yes, the way to get synced outputs would be to use a quad-link 4k setup to be quadrant based (not 2SI/TSI/Two sample interleave)
Although blackmagic does have a system to sync up individual outputs, we don’t yet support it, sorry.
Thank you for the response, this method is working well so far.