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Note about File Recorder and "With alpha" checkbox

CasparCG Server, Client and development

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Note about File Recorder and "With alpha" checkbox

Postby Helge Norberg » 14 Feb 2017, 11:31

I just wanted to clarify something about using the File Recorder item (ffmpeg_consumer) and "With alpha" option:

The file where the fill is recorded will have premultiplied color data unless the video channel has straight-alpha-output enabled.

The thing to consider is that when playing back a separate fill/key file pair (the key in the _A file) CasparCG always expects straight alpha so it will be multiplied again by the mixer.

So my tip is that if "With alpha" is used with the intention of playing back in CasparCG, straight_alpha_output needs to be enabled during recording, and disabled later.
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Re: Note about File Recorder and "With alpha" checkbox

Postby Jesper Stærkær » 14 Feb 2017, 13:43

Oh, I din't know that it expected straight alpha. Perhaps premultiplied/straight could be a parameter for the FFMPEG producer?
Jesper Stærkær
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Re: Note about File Recorder and "With alpha" checkbox

Postby Jesper Stærkær » 14 Feb 2017, 13:46

Thank you though, it's great having this kind of information!
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