Proxy editing

Submitted by Jeff F.T. @jeff

Description

Proxy editing is the ability to swap clips by a "proxy" version that is more suited for editing, and then using the original, full-quality clip to do the render.

It's definitely a very nice feature when you have HD footage and your computer is not beefy enough to handle realtime playback.

This should be integrated into pitivi's set of features so that it works transparently and reliably for users that want to use this feature.

To some extent, all it really amounts to is:

• batch encoding clips into low resolution, easily seekable/editable clips
• automatically replacing the URIs in the project with different URIs
• dynamically swapping them again when rendering
• build the ability to do all that in the GUI

I've never used proxy editing myself, and I'm unsure if:
A- proxies should be automatically replaced by their originals at render-time
B- the user must manually ask (with a gui of some sort) to "replace all the clips to their originals"

Approach A seems to make more sense to me at first glance.