[mythtv-users] Resubjected: Oversaturated TV-Out

[Matt]

I looked around on the net a bit, lots of references to bleeding, 
blooming, oversaturation.

This page, although vague, seems to describe the problem. (red being the 
worst for me)

http://www.camcorderinfo.com/info/colorguide.htm

I think the problem is that the DAC's the manufacturers are using on the 
video cards are producing voltages that are too high for NTSC or S-video 
specs.
Normally, this could easily be corrected with software.  However, these 
poorly supported or reverse-engineered drivers that we are using lack 
that polish.

Now, I'm thinking that the easiest way out may be to do it with 
hardware.  Those of you who are using S-video out on your card might be 
able to stop the problem with a hacked S-video cable using a resistor 
attenuation on the chrominance or luminance portion of the cable. 
 That's pure speculation though, I have no idea what effect that would 
have on the picture.

My G400 has no S-video, so I might try something more ambitious.  I 
might try building this soft-limiter shown in figure 4

http://www.linear.com/pdf/an57.pdf

The schematic looks friendly, and the chip is available from digikey. 
 It probably won't have the effect that I want it to, but it'll be a 
cool experiment anyway.


side note: Figure 12 looks pretty cool too



Craig Paterson wrote:

>On Fri, 2003-08-01 at 11:24, Aaron Stewart wrote:
>
>>Supposedly under Win****, there's a setting for Color Correction, so it
>>either handles it in software (which I doubt), or there's a register you
>>can call to turn it on -- but once again, NVidia's blatant disrespect of
>>the GPL (and they're using GNU tools to make!!!) makes it extremely
>>difficult to figure out which register that is :/..
>>
>>>>I like my G400, the only problem that I have with it right now is with 
>>>>the color/saturation; red is way too saturated
>>>>
>>>I have the same issue with my nForce2 M/B.  All posts to the nforce linux
>>>boards have been resoundingly ignored, so I have been considering a scan
>>>converter or something equally drastic.
>>>
>>>Anyone know a magic bullet for oversaturated TV-Output?  Specifically for
>>>nvidia and/or G400's?
>>>
>
>I also have this problem, using the onboard GF4 MX video of a Shuttle
>SN41G2. Adjusting the gamma (to 1.45) in XF86Config and playing with the
>inputs on my PVR-250 hacks around the issue a little, but not enough. As
>a result, recorded video is significantly lower viewing quality than
>off-air.
>
>Anyone who knows lots about signals on cables, DACs, those sorts of
>things want to comment on what causes this? (Even though it's a little
>OT, since if there are generic steps to take it might be useful to many
>users.)
>
>Craig.
>
>
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