Several ways to do this.. An easy with is to use the Mask feature in the pan/crop tool. Other ways include adding a track above and re-size/reposition a solid color black media generator.
I would also like to try that to experiment with video noise phasing, one track upon another but the entire clip would have to be able to be phase shifted linearly in relation to the other. Might work then again might not. I figured it would need just a teeny bit to get a different noise print per frame.
I don't think that will work if you're using the same clip both times. You would have to have captured the original scene on two different tapes simultaneously. If you're simply using the same clip shifted slightly then Vegas will quantize them when rendering and you'll end up with identical frames lined up with each other, which won't make any difference.
1) You cannot trim 1/3 of a frame, I guess you could make a clip run for 1/3 of a frame less (the entire clipe would have to be reampled) so long as the next clip (which would also have to be resampled) started at a 2/3 frame offset). Ultimately though you must output complete frames. You can of course trim audio by 1/3 of a frame.
2) If you want to try an interesting and simple way to cancel noise or clean up very dodgy video try using motion blur. The effect produces frame integration. Obviously if you have a lot of motion you may not like the result but in some situations MB can be a real lifesaver.
I've had old VHS where the titles had hideous chroma flagging and noise, with 10 frames of MB it looked pristine, the background shots looked rather ethereal but overall it looked way better. Sometimes I've used MB and masked say moving lips, a bit of fiddling around but results were totally convincing.
Bob.
The main objective (for me) would be to take an old VHS tape full of noise and garbage and make it look like a mini-DV tape through processing. I think someone will eventually come up with something even if the processor cost is a couple million. Even on the same lines as Sonic Foundry Noise reduction for audio, take a small sample of the video noise with a circle then push the button, wallah!