Layer clip with straight alpha

  • casparcg version 2.3.3
  • Clip Codec: Quicktime RLE 32 bit (with Alpha Channel)
  • Alpha Type: Straight Alpha

The wiki tells sources should be premultiplied to have clean video layering inside casparcg

Is there any way to layer video with straight alpha, too?

You can use the Straight Alpha Mixer command.

seems not to work:

[2022-09-15 18:05:16.227] [info]    Received message from 127.0.0.1: MIXER 1 STRAIGHT_ALPHA_OUTPUT 1\r\n
[2022-09-15 18:05:16.227] [info]    Sent message to 127.0.0.1:400 ERROR\r\nMIXER 1 STRAIGHT_ALPHA_OUTPUT 1\r\n

I changed my config file, too. But this seems not to have any influence, also.

<mixer>
    <blend-modes>          true</blend-modes>
    <straight-alpha>       true</straight-alpha>
    <chroma-key>           true</chroma-key>
    <mipmapping_default_on>true</mipmapping_default_on>
</mixer>

I would expect ffmpeg to know that its straight alpha and to auto convert it.
Or perhaps using an ffmpeg filter to do that conversion will work? I dont know the syntax for that

I don’t know if it works with these spaces:

<mixer>
    <blend-modes>          true</blend-modes>
    <straight-alpha>       true</straight-alpha>
    <chroma-key>           true</chroma-key>
    <mipmapping_default_on>true</mipmapping_default_on>
</mixer>

Would you mind trying:

<mixer>
    <blend-modes>true</blend-modes>
    <straight-alpha>true</straight-alpha>
    <chroma-key>true</chroma-key>
    <mipmapping_default_on>true</mipmapping_default_on>
</mixer>

Im pretty sure any support for mixing or outputting straight alpha got removed in 2.2

Seems like that. Removing the spaces in my config file didn’t solve it.

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