Alpha output

Is there a way to output the alpha channel on a separate output, using one media file with an embedded alpha channel? (Hap Q Alpha specifically)

Probably something obvious I'm overlooking, but unable to find it so far.



  • hello @thekdoggy

    For now, this is not possible to send the alpha channel to a projector. 
    But if you output Millumin via syphon, the alpha will be exported. 

    Just by curiosity, why do you want to send the alpha channel on a separate output? 

  • for a split key on an external mixer.
  • It is possible!
    I've done this before to feed key/fill signals into a mixer.

    You need a layer with a white color card.
    On top of this layer you need another layer with your video which has the alpha channel.
    Then set this layer's blend mode to alpha matte.
    Be sure to use copy layers or you get out of sync.

    Et voila...

  • We are testing Millumin as a playback solution. We would like to set up Millumin playback such that the Video Output from Canvas 1 can be a Downstream Key on our Switcher/Mixer (Blackmagic ATEM 2 ME), such that when a video cue is done playing, or a frame doesn’t contain any content, Millumin output would be transparent rather than black, and the underlying I-Mag cameras would be automatically visible. (This is how we do playback with Mimo Live). However Mimo Live talks directly to an Ultra Studio 4K via Thunderbolt, which can output a Key and Fill signal separately to the switcher.

    Trying to figure out how to get Millumin to “disappear” when there is no content. We tried making a solid white graphic, putting that in the media pool of the Switcher, and using that as the “Key Source” and the Millumin Output as the “Key Fill”, but when the video ends, or we go to an empty frame, it still outputs black instead of being transparent.

    I saw this thread, but as we're just learning Millumin, there wasn't enough specific detailed information for us to understand how to implant...

    1) Are you saying the the White Card layer  would have the blend mode se to alpha matte, or the Video layer?
    2) Do these need to be two separate canvas outputs from the machine as Key and Fill into the mixer, or is this a single output where the video layer disappears when there is no content?
    3) The video doesn't contain any Alpha Channel per se, we just want the layer to be transparent when there is no video playing

    Thanks for any feedback.


    :You need a layer with  but as we are just learning Millumin, there wasn't quite enough information for us to understand exactly what to
  • Hello @arigolan,

    Do you want to achieve something like in this video ? If so, you could use the chroma-tab in the Blackmagic ATEM Software Control.
    To try this out, send an output from your computer/Millumin to the ATEM, with a solid color, let's say pure green. Then adjust the chroma in ATEM Software so the feed becomes transparent : when achieve, you can use this color in a background-layer in Millumin, so it appears transparent on the final ATEM compositing.
    Does it make sense ? Have a look to the attached projet to get an idea.

    Best. Philippe

    PS : if you are beginning with Millumin, feel free to read the first tutorial here
  • Hi Philippe,

    Thanks for your response. We figured it out. There were no "cut out" alpha channels as part of the video, we just wanted the output from Millumin to disappear after a video cue was completed. As the Blackmagic Deckling cards we're using output black when there is no signal, we simply had to add a white card on a separate canvas going to a separate output to be used as the Key Source.
  • Hi, sorry to bring this up again, but is the twin output setup possible with Key and Fill?

    Chroma Key (via green) is not good enough anymore. What if your lower third has green in it?

    A proper Key/Fill twin output scenario would be much better.

  • Hello @frozenwaffles,

    At least for now, Millumin cannot do this with only one canvas. A solution would be to create 3 canvases :

    • one for the content sending its frames via Syphon
    • one for the fill and one for the key, receiving the Syphon feed and outputting to the right SDI

    To separate the colors and the alpha, you can use the following effects (to be installed "~/Library/Millumin/ISF-effects", see tutorial) :

    Of course, we are aware that a "one canvas" solution would be far better. Be sure we are thinking about implementing this. In the meantime, please feel free to vote for this idea.

    Best. Philippe

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