Blackmagic Design SDI and HDMI for input and preview monitoring

It says in the Shotcut Hardware List of Features ’ * Blackmagic Design SDI and HDMI for input and preview monitoring’. Please could someone explain what this means? I have an Intensity 4K Pro capture card in my HP Z800, and a Decklink HD Extreme in my HP Z840 so would love to know how to use Shotcut with these devices.

Settings > Player > External Monitoring will list your devices to use for simultaneous preview output (can be clip in Source player or timeline). You must be using a Settings > Video Mode that is compatible with your device. For example, my old DeckLink does not handle 1080p60. In that case View > Application Log will show something like

[Error ] [consumer decklink] Profile is not compatible with decklink.

I did not test capture today, but that is what “input” means. See File > Open Other > SDI/HDMI. Shotcut has direct API support for Blackmagic Design peripherals as opposed to appearing as a Windows webcam or audio input (although those are available too in Audio/Video Device). The way capture works in Shotcut is similar to a clip transcode workflow: you open something without using Playlist or Timeline and then you export it. You should use an export preset that is not heavy; so that typically excludes HEVC via software, VP9, and AV1. After you open a device, it shows in Shotcut’s Source player so that you can verify it is working. Then, the bottom of Export shows Capture File instead of Export File. In any case, click it, a file save dialog appears, and then capture starts in the background. Click the same button now labeled Stop Capture to stop it. Finally, the captured file should open up in the Shotcut Source player.

Thank you for the very helpful info. I managed to get the preview from my Intensity Pro 4k card, but when I tried Capture File using either MPEG2, mp4, MJPEG, DV or WMV Stock presets all I got were files with INVALID written in the frame. The same happened when I tried HuffYUV from the lossless presets.
Media Express which I usually use for the Intensity card captures uncompressed AVI or MJPEG so I was surprised MJPEG didn’t work with Shotcut capture.
Do you have any suggestions which presets would work with this card?

Ok I would not be surprised if capture is broken. It is an old low priority feature rarely used or tested.