Webcams again

[Tim]

On Thu, 2007-02-01 at 14:08 +0000, Anne Wilson wrote:
> Axel, what's your feelings about the fact that the sliders for hue and colour 
> don't work?  Brightness and contrast work well.  Do you think it's an 
> upstream driver bug, or something else?

If the person writing the software thinks in the normal way, hue should
really only have an effect when you're messing with a video input source
that encodes hue in a shiftable way (e.g. NTSC).  Hue or tint errors are
an NTSC video error (carrier rotated out of phase).  Other non-NTSC
systems, such as raw data from an image sensor don't work in that way.

Likewise, being able to turn colour saturation up and down should only
work if you had a video-signal as source, one that uses an encoded
colour scheme.  If you had the raw red, green & blue, colour data from
an image sensor, you'd have to go out of your way to make it possible to
turn the colour saturation up and down.

Colour balance (whether a picture is tinted by lighting conditions), is
another situation yet again.  That involves adjusting the level or red
and or blue signal from the camera, compensating against the amounts of
red and blue in the local light source, so pictures aren't tinted
artificially.