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How to use a video with an alpha channel inside vMix
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Joined: 7/21/2020(UTC) Posts: 9  Location: Brisbane Was thanked: 1 time(s) in 1 post(s)
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I am trying to create a video with an alpha channel that can be used as an overlay, either directly as an overlay or as a layer. I have created several test videos in DaVinci Resolve that do have alpha channels, but none are recognised when bringing them into vMix. What video format is required to do this?
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Joined: 10/6/2020(UTC) Posts: 98  Was thanked: 21 time(s) in 21 post(s)
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ProRes 4444 files are supported, but the high datarate can mean very large files and, if you have several long files, they can significantly add to the GPU memory load. For a short clip as an Overlay or Stinger, a PNG image sequence works nicely. For medium-length clips (say 10-30 seconds) I tend to stick with ProRes and, if I'm dealing with multiple, longer clips, I prefer to move playback to another system and use an NDI feed with alpha.
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Joined: 7/21/2020(UTC) Posts: 9 Location: Brisbane Was thanked: 1 time(s) in 1 post(s)
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Originally Posted by: matkeane  ProRes 4444 files are supported, but the high datarate can mean very large files and, if you have several long files, they can significantly add to the GPU memory load. For a short clip as an Overlay or Stinger, a PNG image sequence works nicely. For medium-length clips (say 10-30 seconds) I tend to stick with ProRes and, if I'm dealing with multiple, longer clips, I prefer to move playback to another system and use an NDI feed with alpha. Thanks Mat, The files I am working on at the moment are short, but I am not sure how to get DaVinci Resolve to create ProRes 4444. I am working on a Win10 box like most other people running vMix. The closest I can find to ProRes 4444 is QuickTime with DNxHR Codec and the export Alpha box ticked. How did you create the ProRes files? Darryl
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Joined: 10/6/2020(UTC) Posts: 98 Was thanked: 21 time(s) in 21 post(s)
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Ah, yeah sorry, forgot to say that I do most of my content creation on a Mac, so ProRes is an obvious choice. Having said that I believe there are some 3rd party encoders which support ProRes. I don't know if Adobe Media Encoder supports ProRes on Windows but I'm pretty sure FFmpeg can create ProRes cross-platform with the right incantations. Having said that, if you don't have Adobe tools installed and don't fancy messing with the command line, I'd probably start by transcoding your DNxHR files to image sequences and see how you get on in vMix.
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Joined: 11/4/2022(UTC) Posts: 1  Location: Łódź
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In case anyone came here for something of an answer: 8-bit DNxHR + compressed alpha is the way to go for 4K projects if you want/need more than 3-4 sources playing at the same time. MOV wrapped uncompressed RLE RGBA and ProRes 4444 place a 3-4x bigger burden on the system (CPU) and easily max out even high performance machines.
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Joined: 11/8/2023(UTC) Posts: 3  Location: Bujanovac
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Originally Posted by: MatiasPL In case anyone came here for something of an answer: 8-bit DNxHR + compressed alpha is the way to go for 4K projects if you want/need more than 3-4 sources playing at the same time. MOV wrapped uncompressed RLE RGBA and ProRes 4444 place a 3-4x bigger burden on the system (CPU) and easily max out even high performance machines. I have tried exporting a graphic from After Effects with the DNxHR 8-bit SQ (Alpha: Compressed) with both STRAIGHT & PRE-MULTIPLIED options and it works fine when I re-import the rendered file back in After Effects, but in Vmix the transparent areas show up as black. I have tried ticking the "This video contains an alpha channel" box, but it still doesn't work. Any ideas on how to fix this issue?
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Joined: 1/13/2010(UTC) Posts: 5,202  Location: Gold Coast, Australia Was thanked: 4260 time(s) in 1516 post(s)
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DNxHR is not supported by vMix due to licensing issues. Instead use a format like ProRes with Alpha, or most other MOV formats with alpha. For best performance and CPU usage however, using image sequences is recommended: https://www.vmix.com/kno...o-into-an-image-sequence
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 1 user thanked admin for this useful post.
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Rank: Newbie
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Joined: 11/8/2023(UTC) Posts: 3 Location: Bujanovac
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Originally Posted by: admin DNxHR is not supported by vMix due to licensing issues. Instead use a format like ProRes with Alpha, or most other MOV formats with alpha. For best performance and CPU usage however, using image sequences is recommended: https://www.vmix.com/kno...o-into-an-image-sequence Thanks for the response!
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