garageCube

If I make a video with only black pixels (rgb = 0, 0, 0), then Madmapper converts this into (rgb = 1, 0, 1). This is also the case when you screenshot the media quad with the black video enabled on it, so the rendering process doesn't keep it purely black. This messes up the sampling from a Spout projector output for led strips, because the led strips turn slightly purple instead of being turned off. In an actual video, some parts of the led strip should light up while the rest should stay dark, but the rest becomes purple now.

Madmapper 3.7.11.

Do you experience the same issues on MadMapper 5 or 6?

I only have this version of Madmapper. But since I wanted to have the output be linear with the video, I set the responsitivity to 0%. Setting it to 4% makes it very close to linear behavior but gets rid of this issue, as black is now black again.

This is a color space profile, video is encoded in YUV not RGB. The conversion depends on color profile. With FFMPEG you can choose your color profile in your movie parameters. If possible MadMapper detects the color profile automatically but depending on the encoder it might not be specified in movie file or the wrong profile is specified. By testing different color profiles you should be able to find the right one.
If not, please share the movie in question and we'll investigate (you can send a cloud link in private message or contact support@madmapper.com)