Is it possible to reverse an "auto levels" type of processing?

[Fuzzplug Jones]

My primary editor is Vegas 5 so I'd especially appreciate tips for that platform.

I just pulled a tape from 2001 into the digital domain. It was shot on a crappy consumer-level Video8 camera. As I do with all my stuff now, I recorded it to my Canon ZR100 and then "captured" it into AVI over firewire.

The video looks exactly as it did when it was shot and.. well, that's kind of the problem. That old Video8 camera had a sort of AGC in the video circut, as I guess most of them do, but in this particular video it's pretty bad. If something brightly-colored happens to move through the frame, a very noticible darkening of the rest of the frame occurs. For this particular video, I would prefer that the bright object was a little washed-out as opposed to watching the background fade in and out.

I know this is what an auto-levels plugin does (and in fact, adding one makes the problem twice as bad). My question is, is there ANY way to "reverse" the phenomenon? I was hoping maybe there was a way to have an auto-levels plugin look at a specific area of the frame (say, a corner where the background is almost always visible) and set the levels of the entire frame based on THAT. However, I am clueless as to how to proceed.

Any takers? I searched before I posted and nothing came up, but if I missed something relevant feel free to link it.

Thanks much,
-Mark

[edDV]

Not likely:

The camcorder was running the auto iris based on some kind of center weighted average algorithm. 8bit video requires picking a minority of real world luminance into the narrow CCD dynamic range. For DV this is 219 levels (16-235 plus overshoots).

If you run in auto iris and shot something bright in the center, everything else is pushed down to dark gray or clipped to black. All you can do is play with the levels or color correction filters and keyframe to the timeline manually.

[Fuzzplug Jones]

Okay. I kind of knew I could do it "the hard way" but I always like to make sure there isn't some stupidly easy way instead.

[dphirschler]

This may sound crazy, but an Avisynth script with some manual labor would fix it. Consider this theory:

videoclip1 is your original clip.
videoclip2 is a copy that corrects for the worst of the darkening... but the "normal" parts will be too bright.

Now all you have to do is write a function that slowly dissolves from one into the other. Match the time of the dissolve to the time it takes the AGC to ramp up.

The coding should be somewhat trivial. It's manually identifying each bad part that will be laborious. Still if it's worth it, it's worth it.


Darryl