Example use case: for the PiTiVi tutorial, I intend to make me and the computer talk, both in English (both not our native languages!), and some viewers may have trouble understanding our respective acccents.

Here is a nifty idea to make PiTiVi a killer NLE: integrate the workflow of subtitling: allow adding "subtitle" tracks. Those tracks would be a third kind of track (vs audio tracks and video tracks). They would allow only one specific kind of clip to be inserted in it, that is, a "subtitle clip".

Each subtitle clip would behave like a generic clip in the sense that you can move it left and right on the timeline and trim its starting/ending point by dragging its left/right edges.

Selecting the clip would reveal a small gtk.entry (or text field?) below the timeline that allows editing the text (no dialog, that would be overkill). The text would be plain-text, so nothing complicated on that front; we want this to be compatible with plaintext subtitle formats.

Creating subtitles would be simple: the user can click a button and a subtitle clip would be added to the current subtitle track, at the cursor position. If no such button is available, an alternate way (which is just as easy, but needs to be documented for end-users) is that to add a subtitle clip, you select a region of the subtitle track and start typing directly.

In the end, the user has two choices:
- export a subtitle track manually, to .srt or something
- render the project, with a container format that embeds those subtitles (such as mkv, and perhaps ogv and mp4?)

Subtitles should take into account ripple/rollover edits, I guess.