VHS capture has too much gamma/brightness

[kitanai]

My VHS capture shows too much gamma or contrast (I think) on some tapes. That is: a slight blue background will appear almost white on the PC screen, whereas on TV it looks fine.

Not to forget: these tapes were in NTSC, once. A friend of mine made a copy to PAL. So I try to record a PAL tape, that was originally NTSC. (I know, sounds horrible ;) )

Is there someone who can give me a hint how to use TWEAK(x,x,x,x) in AviSyth or even better has some idea what causes this behavior?!?

Up to now, I came up with: Tweak(hue=0.0, sat=0.90, bright=10.0, cont=0.7). Take a look at before and after (keep in mind, this is supposed to be some kind of blue!):

http://www.nt-internet.de/doom9/wall01.jpg and http://www.nt-internet.de/doom9/wall02.jpg

Thanks for helping!

Unfortunately, I cannot capture an original TV image to post :(

[rfmmars]

The word Gamma is not correct useage. Gamma is the log distortion of the brightness curve. Are you looking at a TV or video monitor fed buy your capture device when capping? If not you can't expect to get the balance right for TV viewing.

On most devices there is a contrast and brightness setting, and if there is a Gamma adjust, it is for the CPU only, has nothing to do with the capture. Does the tape have Macrovision?

richard

www.photorecall.net

[kitanai]

Well, it is not a commercial tape, so no Macrovision!

I play the tape on a consumer VCR and watch simultaniously on TV and PC while capturing. I tried to connect via composite and the Tuner (svideo is not available). Both connections show the same picture on PC (first one above). However, on TV the picture looks good and normal.

I recorded other tapes before (which were "pure and original" PAL) and I never experienced these kinds of problems before. Of course, some color-adjustments and filtering is necessary ;) By the way: PAL-60 captures of all-NTSC-tapes are good quality, too.

My guess: the mixture of an original NTSC tape converted to PAL. But why... :confused:

My intension is to backup my old tape archive as MPEG4 on DVD-R. The first tapes were fine and look very good. Now, I am stuck :(

[rfmmars]

What kind of effect does changing the brightness and contrast have when capturing?

richard

[kitanai]

Where do want me change it? The VCR has no option to change these settings, its output seems to be fine according to the TV screen.

I could imagine to make use of these sliders in VirtualVCR which I use for capturing. I will give it a try and will report back later!

Of course, I surely want to come up with a final solution, but I am also interested in what causes this behavior...

[rfmmars]

In your capture card software there should be these adjustments.

richard

[kitanai]

Found the sliders, and this is what I finally came up with:
http://www.nt-internet.de/doom9/wall03.jpg

Not as good as on TV, but very close. To sum up: bright areas are too bright, dark ones too dark. I was not fully able to correct this, but I found some place in between.

Do you have any idea what the source of this distortion might be (as I said before, "normal" tapes play great on PC) :confused:

[toysoldier]

Try to use this virtualdub filter :colorequ.vdf,
I have use it,it's very easy and direct see edit effect.

this is download address:

http://www.hlinke.de/colorequ.zip