edit video and audio frame by frame with pitivi or any other software: how?

While I don't have an answer to help you with Ubuntu, as I am really new to this operating system, I am equally searching for the same kind of answer you are. However, I do use an extremely powerful movie editing program in Windows which I haven't found anything more powerful than it still after a couple of years of searching. The name of the program is "Vegas Movie Studio" and while their is 3 basic versions of the program that I am aware of, you can try it for free for 30 days. They say it's the same software that the big movie companies use to produce the movies we buy on DVD today.

If you can find any program on Ubuntu that even comes close to this, I will be very excited because it's the one and only reason I am still stuck with Windows, at least for now. I hope that helps you...

Your question is unclear. Please clarify what you mean by frames. PiTiVi lets you zoom into the timeline up to the frame level.

Compton: please do not hijack questions/threads to suggest proprietary software. Open your own threads if you have specific questions. At the moment, the closest you'll get to Vegas on Linux is KDEnlive.

Jean: PiTiVi lets me zoom into the timeline upto the frame level. Yes, how do I edit the content of each of several frames? The frame contents are not identical because there is an animation part and a static part. Only I wish to mask an arrow symbol in the static part which the visiting audience mistakenly thinks can be activated as in a touch screen.

Compton: I have come out of WIndows 7 to enjoy the UBUNTU experience. As said by Jean it may not be advisable to use the forum for suggesting proprietary software. It will be nice to get exposed to equally efficient UBUNTU software rather than go to Windows mode back again! Thanks anyway, but I will wait for Jean's suggestion. Well, perhaps you will try KDEnlive!! There are several kind souls in UBUNTU forum to show the way to less experienced users. Isn't that great?!

As I understand it, you want to use an animated mask or use some sort of compositing/special effects that is animated over time. You're basically looking for an alternative to Adobe's "After Effects" (or to some extent Vegas/Final Cut).

As far as I know, there is no video editing software on Linux that can do that currently, except maybe if you consider Cinepaint (if that thing is still alive?) or Blender. *Maybe* KDEnlive can do it, but I'm not sure. "Removing" stuff from the image is a pretty advanced feature.