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Thread: NDI Broadcast from Unreal. Does alpha transparency work?

  1. #1
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    Question NDI Broadcast from Unreal. Does alpha transparency work?

    So I've been testing the NDI SDK for Unreal and it's very nice but I can't seem to figure out how to get it to output with alpha transparency.

    I'm just starting out with Unreal so I'm not sure if it's a limitation of the NDI plugin or I just don't know how to properly configure it for alpha support. Any guidance here would be greatly appreciated!

  2. #2
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    Give this video a shot: https://youtu.be/Vwr1MMVBqo0

  3. #3
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    Thanks for trying to help but that video doesn't cover anything having to do with alpha channel support in the NDI plugin and doesn't deal with output to NDI at all.
    It's a tutorial where he brings in green screen footage via NDI and then chroma keys it in Unreal engine.

    - - - Updated - - -

    To be clear. My ultimate goal/desire here. Be able to output from Unreal engine to NDI with full alpha support. Meaning things like even bloom work.

  4. #4
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    Hi Tox,

    Did you ever have any success here?

    I am looking into the same thing and am stuck too.

    I have managed to get the alpha transparency working on a incoming NDI feed to unreal, but am struggling with the output. See attatached image which has a NDI source with transparency working inside unreal

    Has anyone from NDI confirmed that it is possible to include alpha from unreal?

    My theories currently are
    • The render target knows it's alpha mask so if there is a way to broadcast that separately then key/fill would be possible
    • the composure tool seems to be the solution for those with hardware capture cards, it can also output to a render target
    • I'm just missing something that includes the render target's alpha in the ndi broadcast


    I've posted in the Unreal developers group too to see if anyone has any sensible suggestions.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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ID:	148840   Click image for larger version. 

Name:	ndiout.png 
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ID:	148841  

  5. #5
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    No I didn't. I ended up moving to Unity for my project as I found Unreal to be unnecessarily complex.

  6. #6
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    Find
    Code:
    NDI_video_frame.FourCC = NDIlib_FourCC_type_BGRX;
    in the plugin source code and change it to
    Code:
    NDI_video_frame.FourCC = NDIlib_FourCC_type_BGRA;
    . It's a wonder that they didn't set it that way in the first place.

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