jit.grab working with Decklink Mini, but not with Decklink Duo 2


    Apr 06 2021 | 9:48 pm
    First post, hello everyone! Also, new to Max MSP. Please be kind : ) I have this weird problem with my Blackmagic Capture Cards. I have in the same PC a Decklink Mini (1 Channel SDI) and a Decklink Duo 2 (4 Channel SDI). Just working with the help example for jit.grab, I'm able to get a 1080p25 camera input via jit grab from the Decklink Mini, using the [native] driver. If however I plug the exact same signal into the Decklink Duo 2, and select its [native] driver, jit.grab throws this error message:
    jit.grab: blackmagic device unable to find valid video input format - closing stream
    I've tried to pick the video format manually to no avail. With the Mini, the format is just selected automatically. I'm using BM Video Desktop 12.0 and the latest firmware, as well as the latest version of Max. Would be grateful for any ideas or pointers!

    • Apr 07 2021 | 2:12 pm
      I forgot to add, video capture works with all other programs - Resolume, OBS, even Blackspout which seems it's from a couple of years ago .. One thing that has changed in BM Desktop video is that the SDI stream format only seems to get displayed now once an application is capturing it, e.g. when I open the camera stream in OBS, the Input format reads 1080p25, but when I close OBS, it goes back to - . That does not help with troubleshooting this issue here of course .. Capturing a webcam works.
    • Apr 07 2021 | 3:10 pm
      Seen here working with Decklink Mini
      Seen here working with Decklink Mini
    • Apr 07 2021 | 3:11 pm
      Not working with Duo
      Not working with Duo
    • Apr 07 2021 | 3:48 pm
      few things to make sure of. On Windows only a single application is allowed to open a capture device at a time, so if you have another app opened that has grabbed the device, it will fail. Another thing to note is the autoformat detection is pretty flakey, so I would not rely on that. Lastly, if I remember correctly it's not exactly obvious which device corresponds to which input.
      I would do a quick test by restarting the machine, opening Max, and and then try to open the device each device with the format already set to the one you know works. If you're sure that's not working, then you can follow up with me privately and I'll try updating the sdk we link to and send you an update. No idea if that will make a difference but we can try. email link in my profile.
      on the other hand, if the blackspout thing works, that may be the best option, since it will process the stream in a separate process and therefore make better use of your system resources.