Dark movies with green bias

[jp2510]

My HTPC produces great picture for watching DVD's, but whenever the scene is dark (i.e. a dimly lit room/nightime/etc) black appears to have quite a strong green bias. Has anyone come across this with their setup, and how might i fix this?

The effect is slightly better when watching through PowerDVD, but still noticeable. (The effect is present with ALL dark scenes in any DVD/TV program)

I am aware that my GPU is not VMR9 compatible - could that be the anwser? When the same DVD's etc are streamed to my laptop they look beautiful.

Thanks for any ideas

Windows Media Center 2005
1800+ XP
Geforce4 Ti 4200 128mb
S-Video output to junky 32" standard TV

[MTyson]

Have you tried going to Power DVD's video configuration of the Red, Blue & Green? Try lowering the green or raising blue and/or green.

[miketech]

Be careful w/ green bias. Do all your movies look that way? A lot of movies are green.
Matrix series,the ring and many more. Don't forget to calibrate your display too!

[Cush1978]

Add my .02, I've noticed that in ZoomPlayer with FFDShow using VMR9 (which is what I calibrated to), I see green when the scenes fade to black. In PowerDVD, they look perfectly black. No idea why!

Cush

[jp2510]

Yes unfortunately all my movies look this way.

With regards to altering the video config colours, i'm not sure this is the solution because in a norma well-lit scene, the colours all appear perfect - true to life and as they are supposed to. It only occurs in those dark scenes and, as Cush1978 has experienced, when the scene fades to black.

What about the lack of VMR9 support from my vid card? I would hate to go out and buy a new card to see no change (though a major upgrade is looming anyway i suppose :D )

[hdkhang]

Could just be your viewing device, not all of them will track grayscale perfectly all the way down to the lower IRE ranges, in fact very few do. VMR9 doesn't make the colours more correct per say, it simply is a means of producing video levels instead of PC levels out of a PC and at a higher precision than Overlay. You mention they are present in TV signals as well, is that tv from the PC or from your TV tuner/DTV-STB? In any case you'd want to calibrate your set, the human eye is a very poor measuring instrument in isolation.

@Cush
You might have a version of FFDShow that pushes green under certain filter configurations :) Disable FFDShow under ZP and if the problem goes away, try using another version of FFDShow.

Cheers...
Duy-Khang Hoang

[Cush1978]

Hrm, I'll give that a shot. I'm using the SSE2 optimizes "Andy" version because newer versions maxed out my 2.4GHz CPU. Still, I'll see if it makes a difference. I'm currently just using a blur/denoise and a resize with output at YV12.

Cush

[jp2510]

Duy-Khang: The TV signal is from a STB (digital cable) via coaxial through my PVR-500MCE.

It could be the viewing device - 5yr old 32" RCA TV (F32648) - and i am having to use s-video. I really hope it isnt though, since this is very annoying and a nice TV upgrade would be drastically more expensive than the HTPC upgrade. The wife hasn't caved in on that one sadly.... yet.

[Vern Dias]

You must resize to 1.5X or 2X or you will get the green push (and some other very subtle problems) with many versions of ffdshow.

Vern

[jp2510]

Vern: I hope this will work for Cush. Personally i'm not using FFDShow.

hdkhang (and everyone else), can you recommend some calibration software? Thanks.

[Vern Dias]

Unfortunately, it takes more than software to get the job done correctly. I suggest you search for ISF on google.

Either AVIA or DVE (Digital Video Essentials) will fulfill the software end of your needs.

Vern

[jp2510]

Thanks Vern. I was afraid you would say that.

Will check out your suggestions. This green push/bias is very annoying.

[hdkhang]

I guess you could just try the DVE/AVIA approach for now, if the results are somewhat satisfactory you could live with it for the time being. ISF calibration is very valuable but not enough people can justify the cost, most would rather put that portion of the cost towards budgeting for a better TV to begin with, but what defines better TV is where we scratch our heads. Say you have the same budget for two options, 100% of funds towards the TV or reduce the funds for the TV by the amount it takes to get it ISF calibrated... it could be that the cheaper TV calibrated may exceed the more expensive TV, or it could be that the cheaper TV has no hope of keeping up with the more expensive TV and a calibration disc. Hard to gauge. At least when you take the time to play around with DVE/AVIA you might have more of a clue as to what to look for should you decide down the road to upgrade your viewing device.

On a side note, PowerDVD may be giving you less green push due to some colour settings it defaults to.

Also worth trying if all else fails is to see if any versions of the nVidia drivers allow you to adjust individual colour curves, that might offset some, though it should be a last resort as it might introduce other errors of its own, but it would then be up to you to decide whether or not that tradeoff is worthwhile etc.

Cheers...
Duy-Khang Hoang

[Vern Dias]

see if any versions of the nVidia drivers allow you to adjust individual colour curves

All recent versions do. Go to advanced mode on the color correction menu.

The problem with this is that if the CRT bias is maladjusted so the the green gun is never cut off, nothing you do with the incoming signal will help.

Vern