I'm considering using avisynth to make color and contrast adjustments, which I believe will be constant for the entire film. Assuming I can provide a frame from the bad source (A) and a frame from the correct source (B), is there any software that can just tell me what sort of changes avisynth needs to do to convert A to B, or is it just a matter of guessing until you find the adjustment that works?
I have an Excel spreadsheet that might be of use to you.
Basically, you pick a few pixels from source (A) and enter the "observed" YUV values into the spreadsheet. You then take the YUV values for the same areas from source (B) and enter the "target" YUV values - what the colours should be. You then adjust various parameters (using Excel's Solver if you wish) to get the observed and target as close as possible.
These parameters can then be exported to a ColorYUV command in AviSynth.
The procedure works best with test cards which have large areas of solid colour. A complex picture may be harder to match.
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I'd be interested in that. Since I believe I need to apply the exact same adjustment to all frames, I believe I would just need to find some frames with solid colors from Source A and Source B to get a good result for the whole thing.