[mythtvnz] mythtvnz Digest, Vol 21, Issue 29

[Robert (MythTV)]

Hi Aaron,

> Colours don’t look natural. Broadcast video uses colour levels in the 
> range 16 – 235, while PCs use a colour range 0 – 255. So my graphics 
> card is sending out video as 0 – 255, however the TV has now switched 
> itself to “broadcast” mode and is interpreting the colours in the 
> range 16-255. Which means, the colours at the top and bottom end of 
> the range are all collapsed together. Darks and lights have lost a lot 
> of definition and contrast. Again, high end TVs often have the ability 
> to allow the user to switch colour modes – the Sony Bravia V Series 
> does not. (Although I did find that going into the TV menu Picture > 
> Advanced Settings > Colour Mode and changing to Wide did help a lot.) 
> The only way (I think) to fix this properly is to get the video driver 
> to scale the colour levels on output.
>

To help out with your video issues (and anyone else who wants exact 
colour corrections), I've made a Open Office spreadsheet which can 
calculate the output Colour Lookup Table (CLUT) from nVidia Cards 
according to the nVidia X Server Settings dialog, under X Server Color 
Correction. While this isn't an exact/correct tabular expansion of the 
CLUT, it will give you a quite workable compromise solution.

Enter the values into the spreadsheet, and it'll generate the table of 
output values, so you can get an exact result instead of trying to guess 
visually, or see if the range has been expanded properly.

Download it from here:
http://www.isolutions.co.nz/nVidia_CLUT.ods

At a guess, you could try these values to get an expanded range 
approximating what you need. I haven't tried this out, but it appears to 
do what you would want. Otherwise, just try out numbers in the sheet, 
and adjust until you get the CLUT results you want.

*Brightness* 	-0.0250
*Contrast* 	-0.0600
*Gamma* 	1.1000


Hope it helps compensate for the TV's omissions.

Regards,
    Robert.

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