fixing brightness/contrast of black & white dvd

[x264]

Hi i have a dvd of Samurai Assassin 1965 which looks very bright to me when i watch it with vlc. How do i fix the contrast/brightness with avisynth?










samples:

http://www54.zippyshare.com/v/bWm5GcMp/file.html

[manono]

It " looks very bright"? That's hardly proof positive. Add 'Histogram()' or 'ColorYUV(Analyze=True).Limiter(Show="Luma")' to your script and prove it conclusively. Using the second test, if you see globs of green, then the whites are blown out and the contrast needs adjusting.

It doesn't look that way to me, though. You can use the Levels command to lower the levels (make it look 'darker'), and the Tweak filter to adjust the contrast, as in:

Tweak(Cont=0.9,Coring=False)

The parameters are interdependent. For example, lowering the contrast should probably also be matched by a slight increase in the brightness.

DVDTalk didn't like the quality of the DVD at all:

https://www.dvdtalk.com/reviews/14721/samurai-assassin/

[raffriff42]

Whites too low, not enough contrast in highlights.


[Attachment 44577 - Click to enlarge]


[Attachment 44578 - Click to enlarge]

ImageSource(...)
ConvertToYV24

## expand range:
Levels(0, 1.0, 180, 0, 255)

## lower midrange (inverse gamma)
Invert
Levels(0, 2.5, 255, 0, 255)
Invert

## expand range again
Levels(6, 1.0, 200, 0, 255)

Histogram
return Last

[x264]

It " looks very bright"? That's hardly proof positive. Add 'Histogram()' or 'ColorYUV(Analyze=True).Limiter(Show="Luma")' to your script and prove it conclusively. Using the second test, if you see globs of green, then the whites are blown out and the contrast needs adjusting.

When i added ColorYUV(Analyze=True).Limiter(Show="Luma") to my script i saw red blocks in avspmod.

Whites too low, not enough contrast in highlights.

ImageSource(...)
ConvertToYV24

## expand range:
Levels(0, 1.0, 180, 0, 255)

## lower midrange (inverse gamma)
Invert
Levels(0, 2.5, 255, 0, 255)
Invert

## expand range again
Levels(6, 1.0, 200, 0, 255)

Histogram
return Last

thank you riffraff for the code. The video looks good now

[jagabo]

Whites too low, not enough contrast in highlights.

ImageSource(...)
ConvertToYV24

## expand range:
Levels(0, 1.0, 180, 0, 255)

## lower midrange (inverse gamma)
Invert
Levels(0, 2.5, 255, 0, 255)
Invert

## expand range again
Levels(6, 1.0, 200, 0, 255)

Histogram
return Last

thank you riffraff for the code. The video looks good now

That is going to crush blacks and blow out some of the brighter shots. You need to tone it down a little. I did:

Invert() # negative
ColorYUV(gain_y=125, off_y=-101) # contrast stretch to full range Y
ColorYUV(gamma_y=30) # gamma adjustment to bring out details in the brights
Invert() # back to positive
ColorYUV(gamma_y=30) # gamma adjustment to bring out detaiils in the darks
ColorYUV(gain_y=-40, off_y=16) # final adjustment back to limited range Y

[manono]

When i added ColorYUV(Analyze=True).Limiter(Show="Luma") to my script i saw red blocks in avspmod.

Which tells you the black levels are crushed. Green blocks tell you the whites are blown out which, apparently, isn't happening here. In fact, it appears your claim that the film "looks very bright to me" is misleading. Maybe you have your player and/or video card set up incorrectly.

[johnmeyer]

Watching in VLC (or any other media player) can sometimes give you brightness that does not actually reflect how the video itself should look, if played on another player.

The only way to know if your video really needs to be modified is to put it into an NLE and use its histogram, waveform, or vectorscope display (if it has one) to see the actual brightness distribution.

There are settings in VLC, and also in your graphic card overlay settings, that can change how the video looks.