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DeckLink SDI 4K dropping/skipping frames

PostPosted: Sun Jan 21, 2018 8:09 pm
by Angel Moran
I have a strange issue with a pair of DeckLink SDI 4K cards installed in different workstations.

When I try to capture video from a workstation to the other using Media Express, I get a "Media express could not capture the clip. One or more frames were dropped" error. It may happen after a few seconds or minutes, but it eventually happens.

To test things out, I have created a video with TC burned and have modified one of the code samples to capture the video without drops and I have found that, once in a while, the captured video is repeating one frame, then skipping one. So, when I watch the resulting video, it reads:

...
00:00:15:10
00:00:15:11
00:00:15:12
00:00:15:12
00:00:15:13
00:00:15:15
00:00:15:16
...

So it's repeating frame 00:00:15:12 and skipping frame 00:00:15:14. I don't know if it's the playing or the capturing device, but something fishy is going on. Funny enough, it happens less in 4K25p format than in 1080p50.

I use 10.9.7 drivers on a windows 10 machine with 16GB or RAM and i7-7700 CPU.

I'm at a loss of what may be going on.

Re: DeckLink SDI 4K dropping/skipping frames

PostPosted: Mon Jan 29, 2018 10:14 pm
by Jodon Karlik
Just spent months debugging something similar with a client and solved it minutes ago. So here's a suggestion: Are you sure the card is plugged into a port that is receiving enough PCIe lanes?

If you're on Windows:

Go to Device Manager. Right-Click on your DeckLink 4K Pro card. Click Properties... Click Details tab. Choose the Property you want to look at in this tab is "PCI current link width". If it's not 8, you're not getting enough PCIe lanes to keep up with 4K content.

Re: DeckLink SDI 4K dropping/skipping frames

PostPosted: Mon Jan 29, 2018 10:21 pm
by Xtreemtec
Wow this is usefull info!! Thank you Jodon!

Re: DeckLink SDI 4K dropping/skipping frames

PostPosted: Fri Feb 02, 2018 11:49 am
by Angel Moran
Thanks a lot Jodon!

That looked promising, so I checked and it's getting 4 lanes (which, by the way, is what the box for the SDI 4K card claims you need). So, to be sure, got rid of all other PCI cards (graphics and network), plugged the card into a x16 slot and I'm getting the same problem. It gets 4 lanes and seems to be running fine... but the problem persists.

Just updated drivers to 10.9.10, no luck neither...

I have found that even the InputLoopThrough sample, with does pretty much nothing at all, is dropping frames too, so it seems it may be a problem with either the card not been able to keep up when capturing and streaming at the same time, or maybe the problem is with windows 10?