"Filter to adjust frame color level" or something like this...

[UNICO]

Hi there,

after encoding Terminator 3, I noticed that in the resulting DivX the dark scenes look pretty much darker than the DVD... as it is a pain to change monitor's brightness/contrast or to configure the decoder properties manually, I wonder if there is a filter to do something like Photoshop "Automatic Levels" command and callibrate the contrast/brightness/color levels/whatever and produce frames that look good... nor too dark neither too light...

sorry for my crap english

Help please

Joan

[sh0dan]

There is no generic way of doing this. Auto Levels work on single images, but look quite bad on movies. If you want to see why, try using:

ColorYUV(autogain=true)

[trevlac]

I would think you need to change the gamma/brightness. A TV's gamma and black level are usually out of wack. DVD's are most likely created with this in mind.

I am far from an expert on this, but I've been trying to learn. Here is what certain controls/changes do. Maybe that would give you a good idea of what to change. Note: there are only 3 changes to make. They may have different names, be combined in a filter, and not work in the exact same way from filter to filter.

brightness/blacklevel (the little sun on your monitor controls)

additive
Color runs from 0-255. Changes to brightness move everything up and down the scale. Moving up, Blacks become grey, off white becomes bright white. Everything that goes off the scale is set to the top/bottom number. That is a loss of info, but not a terrible thing.

contrast/gain/white level (the 1/2 circle on a monitor)
multiply
Color runs from 0-255. Changes to contrast move everything up while keeping black at 0. In effect, you streatch your picture range. If you assume your scenes all have black and bright white, an auto gain will streatch all colors along the full range. I guess it takes the high and matches it to 255. More contrast makes a picture look better because you can see distinctions between 10 and 20 better than between 10 and 11.

gamma
exponent
To make a long story short, on a scale of 0-255, 128 is generally not in the middle. This is good because we see changes in the lower range better than in the top end. It also has to do with how a monitor/tv works. So if you use an exponent <1 to adjust a normalized (0/255 to 255/255) range, you get more values in the lower range. Lowering the gamma increases the number of values in the lower end at the scarfice of the top end.

Your TV's blacklevel and gamma are most likely higher and lower (respectively) than your monitors. This means that the whole scale appears darker on your monitor, and that there is less contrast in the darker range on your monitor.

Please Note: If you change gamma on the video (vs the monitor), you are compressing ranges that have more info and streatching ranges that don't. AKA, you spread out the mid to dark shades, but there is no info in between. You shrink the range in the high end and lose any colors in between. I'm not saying this is bad, or even noticable.

At least that is how I understand it to work. You should test before you take may word on it. :D

[UNICO]

Thanks for your answers guys

Joan

[GrofLuigi]

Slightly offtopic, but something i've been wondering about a long time.

When you buy a new monitor, you get a driver disc, which usualy contains (only) an ICC (color correction) profile, which basically defines the gamma of the monitor.
Does anyone know is such a profile (or driver) exists for generic CRT display (a TV)? For example, when using an NVidia GFX card with TVout, windows installs its "default monitor" on the TV output. IMO, this would be a perfect place to apply proper gamma correction for video signal and once for all solve all the problems and gripes with "darker video".

GL