@pepone I talked with our multimedia team and one possible explanation could be that the video has been compressed with limited color range [16..235] instead of full range [0..255] . This is a video encoder setting for the source video. In general it depends on the encoder you use to create the content.
The settings of the surface used for the player could also have an effect - for example if it's sRRGB vs. RGB - but we recommend checking the encoding of the video content first.
I tried different video codecs (VP8) but the problem still exists.
You guys can see it for yourself if you try to render a video to an additive shader -
and it's doesn't look like a 16...235 RGB problem, cause the brightness seems to be +20% or more.
I use a special sprite shader now to dim the brightness to 75% now and add 400% contrast -
then it looks similar to what it should naturally - but this not really shows the shine and glow I use
in the videos and would like to present in the holographic projections.