What exactly am I supposed to be seeing with the AVIsynth videoscope?

[fmctm1sw]

Haven't been here in many years, I can't believe I remembered my password. The analog to DVD bug has gotten me again and I've been doing a lot of reading on IRE levels. To make a long story short, I just need to know what I am looking for on this videoscope plug in.

My setup: Toshiba A-SB88 and a Victor VX-200 VCR. These are quality Japanese market VCRs I picked up while stationed there years ago. I have them running through a Primeimage TBC/Freeze II. At the end is a Canopus ADVC-50.

What I am starting with is getting the the IRE level right. My VCRs (NTSC Japan) are outputting 0 IRE (assumed) and my ADVC-50 is set at 0 IRE as well. The Primeimage TBC also has a setup level control

The photos represent adjustments to the setup level of the TBC. I took a number of screen grabs at unity (0 setup I must assume) and increments of increasing and decreasing the setup level. The setup appears to have a range of around +/-30. Here's the pictures, you tell me....

Hmmm, I'm trying to figure out how to get text in between the photos..

The first image is my Toshiba at 0 setup.
The second image is my Toshiba at +20 setup.
The third image is my Toshiba at -20 setup.

[fmctm1sw]

From the Victor...

The first image is my Victor at 0 setup.
The second image is my Victor at +20 setup.
The third image is my Victor at -20 setup.

[jagabo]

You want the blackest black to be at Y=16, the brightest brights to be a Y=235. Unfortunately, VideoScope() doesn't mark those regions. Histogram() does, so try TurnRight().Histogram().TurnLeft(). That will give you the waveform monitor at the top. Or if you want it at the bottom:

function HistogramOnBottom(clip vid)
{
    top = vid
    TurnRight(vid).Histogram().TurnLeft()
    bot = Crop(0, 0, width, 256).ColorYUV(off_y=-16).ColorYUV(gamma_y=200).ColorYUV(off_y=16)
    StackVertical(top, bot)
}

That also increases the gamma so that it more closely resembles VideoScope().

The first image in the first post looks like it may be right. But that particular shot appears to have been screwed up before you got to it. Check other shots. And you need to be sure the capture device isn't responsible for crushing darks and brights before it gives them to you.

Don't use Info() before VideoScope() or the yellow text will mess up the waveform graph.

[fmctm1sw]

Many thanks jugabo. I was able to get a histogram up but not able to get that function working. Does that go in the .avs file? I grabbed a few shots from the actual movie, those above images are from the intro stuff (advertisements, etc). I think I can work the setup level to get the blackest blacks OR the whitest whites, just not both at the same time. This is a -10 setup level.

edit: I may be able to stretch that brightness with "tweak..."

[fmctm1sw]

I tweaked that last photo. Here's the result...

edit: I think I have enough to go on for now. I can probably bring down those super high brights in my Victor VCR with tweak as well.

[jagabo]

Yes, as long as you aren't completely crushing darks or brights you can use Tweak() or ColorYUV() for final adjustments.

To use my HistogramOnBottom() function you include it in your script then call it:

function HistogramOnBottom(clip vid)
{
    top = vid
    TurnRight(vid).Histogram().TurnLeft()
    bot = Crop(0, 0, width, 256).ColorYUV(off_y=-16).ColorYUV(gamma_y=200).ColorYUV(off_y=16)
    StackVertical(top, bot)
}

WhateverSource()
HistogramOnBottom()

If you put the function in an AVSI file in AviSynth's plugins folder it will be available to every script without explicitly adding it.

I usually prefer a horizontal waveform (HistogramOnBottom() or the TurnR/Hist/TurnL sequence) because then you can more easily see the front and back porch (the black bars at the far left and right) and because it's what you would see when watching the analog waveform on an oscilloscope. Those are good hints about where Y=16 should be. Of course, on some bad recording you'll want to ignore them and just adjust to the main picture.

[Skiller]

I would not recommend using Tweak or Levels because they work in 8 Bit precision only. You can see what damage Tweak did to the levels in the tweaked screenshot: the histogram now exhibits streaks. These manifest visually in banding, particularly in darker scenes on flat surfaces and on fades to and from black or white (not so much if the video is very grainy, but still).

Better use SmoothAdjust. It's a high bitdeph substitute for the built-in functions.

[fmctm1sw]

I appreciate the help gentlemen...

Between the setup and level settings on my time base corrector and the use of smoothtweak, I'm pretty satisfied with the blacks and whites. The next challenge will be figuring out how to get the colors right..