Mpeg2Dec (3) - Contrast and Brightness

[kilg0r3]

Hi, there!

I just noticed that there is a large difference in brightness and contrast between a dvd viwed in windvd (the video preferences set to 'original') and the mpeg2dec output, previewd in virtaldub and mplayer. The image in windvd and other media players is much brighter and has more contrast.

I know how to correct this using levels() and or tweak(). My question is only: Is it allways like that. and: Why is this so?

Stupid me, never checked that, i.e., all my encodes so far are to dark. Strange how stupid one can be :()

[fccHandler]

I don't really know the answer to your question, but I do know that the MPEG2 extensions provide a way for the encoding software to specify (from a set of limited choices) the matrix coefficients that were used during the color conversion to MPEG YCbCr. If the encoder doesn't specify its coefficients, then the decoder uses a default matrix; in addition, the MPEG2 default is different from the MPEG1 default. And yes, I've seen DVDs that specify matrix coefficients other than the default ("Bedazzled" for instance).

Ideally the decoder should use the inverse of the matrix specified by the encoder (if any) to convert to RGB, or else the colors won't appear as the encoder intended.

Of course, if you're avoiding YUV-RGB conversions then none of this applies to you, but I figured I'd mention it anyway.

Cheers. :)

[sh0dan]

Originally posted by kilg0r3
Stupid me, never checked that, i.e., all my encodes so far are to dark. Strange how stupid one can be :()
... or WinDVD overcontrast your images - which is most likely the case. ;)

If you want AviSynth to upscale luma, use ColorYUV("levels="tv->pc") - this is however not correct IMO.

[Gaia]

I had similiar problems and reason was my gfx card drivers . If you have Nvidia card it's most likely drivers. Your encodes might be fine. I fixed it buy installing older drivers. Latest Nvidia drivers have very strange default colour settings for overlay.

[FuPP]

"The image in windvd and other media players is much brighter and has more contrast."

One can see the same problem converting the video to svcd and viewing it with a standalone dvd player (dark image). So I don't think it is a driver problem. I suspect it is linked to the decoding process. Does it exist a way to automatically correct levels and saturation ?

ColorYUV("levels="tv->pc") can help but is not always enough to correct that problem.

FuPP.