VHS to PC Capture Calibration ...

[JasonCA]

Hi Everyone,

So I have the following hardware to start with:

JVC VHS (4MB TBC) -----> TBC-1000 -----> ATI TV Wonder 600 USB

I am using S-Video cables.

Now, what's the proper way of sending a signal from the VHS to PC to show that the picture/video quality is good for things like:
1) Sharpness
2) Color (what about color space?)
3) Dark levels (making sure black is really mapped to black on the PC).
4) ...etc

For instance, is there a calibration picture I can send from the VHS player to the PC? How do I know the colors are correct? How do I know, for instance, red from the VHS is really red on the PC, green from VHS is really correct green on PC, ...etc? How do I know that black is shown the PC as trully black when it's black on the VHS?

Do I use a software based vectorscope to calibrate the VHS somehow? Do I use a software based waveform monitor to measure levels?

How does one go about proving that what comes from the VHS is going properly into the PC? Calibration charts? Whatever looks right? Or are there more proper ways of calibrating the transfer of VHS to the PC? What should be my workflow be?

Any thoughts on this would be great!

Thanks!

[jagabo]

You could get a calibration tape and use it to set levels, colors, etc. But unless everything you are capturing is recorded with a calibrated system you'll find that different tapes have different levels, colors, etc. So you need to adjust the settings for each individual recording. And since most recordings don't include calibration charts you just have to eyeball what looks right. I've used a graphedit capture graph and AviSynth as a tool for adjusting levels. But that doesn't work for all capture devices. You can capture short segments then examine them with an editor. Go back and adjust the capture settings, examine the caps again, etc. But that's pretty tedious.

[sanlyn]

VirtualDub capture mode has a histogram that can be used to check input levels. But remember that dark frame borders will throw it off at bthe dark end. Still, it can give you quick picture of blacks and brights levels. There are also VDUb controls for brightness/contrast that work at capture time. With such software filters, however, it's best not to correct color or do any sharpening during capture. Besides slowing down the capture process, sharpening VHS also sharpens tape noise making it difficult to remove. Once you've set some basic levels, turn off the histogram view, capture a short bit of video, and check it with histograms, etc., in VirtualDub to see how it goes. If you had an AVT-8710 TBC instead of the TBC-1000, you'd have some very basic but useable hardware-based image controls on the TBC.

The chances that you'll get an entirely clean, totally color-corrected capture from VHS is pretty slim. Much of it will likely look OK, but a lot of it will need further processing.