Decklink Duo 2 FPS when input/output at the same time

edited May 2017 in MAIN
We are exploring the possibility of using the Blackmagic Decklink Duo 2 PCIe cards to add additional I/O to Millumin. We have had great success with using them as inputs; however, using them as outputs poses an issue. All I/O references are 1080p@59.94

I have consistently observed an issue where the FPS of the outputs drop as low as 15fps when using multiple outputs from a single DeckLink Duo 2 card.
  • With a single input and output live on the same card the output drops to 30fps.
  • >1 input and only one output drops the output to 15-20fps.
  • One output with no inputs results in an output at 60fps.
  • 4 inputs and no (decklink) outputs results in 60fps (when using DVI out, for example).
Is this a Millumin issue or a Blackmagic issue? Are there any known solutions?


  • Hello @michaelvoccola,

    Millumin is using libraries provided by Blackmagic, so it should have the same performances as their own applications.

    However, if you're using your Decklink Duo on a chassis via Thunderbolt, having data coming in and out could be an issue. Could be : you should ask Blackmagic about this setup, since they are the only one to be able to reply about such hardware questions (if it's your case of course).

    Best. Philippe
  • Hello.

    I have a same issue.

     When use deckling duo2 all as input, it's OK. however use them as output, FPS drop to15~30fps( it seems to be related with
    number of output and resolution).

    My environment is below
      MBP 15" 2017(16GB RAM, Radeon Pro 560 8MB)
      Sonnet Echo Express lll.

    Is the any solution?

  • Hello @sab

    Have you tried updating the Blackmagic driver to the last version on their web site ? 
    What external box do you have exactly ? Is there something else inside (soundcard, graphic card... ) ? 

    If you mac recognise the output correctly and that the image goes throught it, could you ask Blackmagic about this issue as Millumin uses their driver, we don't have much control on that. 


    Antoine M*
  • Hello@antoineM

    Thanks for your reply and sorry for my late reply.

    I have update the blackmagic driver to the latest version and image goes through it.
    My external box is  "Sonnet echo express III”  and there are no any other cards inside.

    I’ll ask to black magic about this issue.


  • Hello,

    I am using decklink duo with a Sonnet echo express SE TB2 with no problems.

    The setup is : one input from blackmagic camera and one or two outputs @ 1080i60 on a 2016 27" iMac. Also working on my 2011 MBP. Both inputs and outputs have to be at the same frame rate.

    Should be a blackmagic driver problem. Try to downgrade driver until you found the one is working. I think 10.7 or 10.8 should work fine.


  • I can confirm that this has been an issue since at least 2014. 
    I always assumed that it was because the BMD cards do not have any "acceleration" and are meant to be used as a reference single output and not in mixed configurations.
    Also, the first post mentions a Decklink Duo 2 which can not output 1080 50 or 60p. 
    I actually have an event this week where I will be using Decklink 4K Pro and an older 3dExtreme, both of which can output 1080p 50 so I will try them as an additional output to see if it affects the framerate. It would always be nice to have an additional output!
  • Hello@camig

    I've try to downgrade BMD driver to 10.7, but I got same issue.
    I guess because I use decklink duo"2"  not decklink duo.

    Thanks for your suggestion,Anyway!
  • Hello @sab,

    Have you contacted Blackmagic support ? Maybe there is a limitation when using both inputs and outputs.
    From what I know (not 100% sure), Decklink Duo is just 2 Blackmagic cards stacked together. But such cards aren't ful-duplex, so you cannot use them as input/output at the same time (so maybe there is an order to choose what are the inputs and what are the outputs in the Decklink Duo).

    Best. Philippe
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