Add subtitle feature on recorded videos

[yaposebastien]

This feature can improve the understanding of those interesting contents for person with disabilities or language barrier.

[soonum]

Thanks @yaposebastien.
I think there is quite of work to achieve that, thus I hope it would be implemented on v0.5 or v0.6 release.

Since we've discussed this matter IRL, I'd like to come back on this subject more thoroughly.
First of all, I think this is a great accessiblity feature, it would surely help hearing-impaired people and watchers without sound-system.

We discussed about the ability to display live subtitles. But by looking at the issue title, tell me if I'm worng, you think about having subtitles burnt onto the recorded video feed. If that's so then I don't think this is a good idea especially for post-processing purpose (scaling, colours treatment, and so on...).
On the other hand, we could totally imagine subtitles being displayed only on the live video feed while the locally recorded feed is stored without it. For doing so, one would have to type what's being said during the streaming session at a good pace to minimize any delay.

Besides several questions popped up into my mind :

• Would the subtitle typer be the one who's running the session?
  Maybe it worths to build an additionnal (lightweight) mode like subtitle-typer so that you can have one person focusing on the onging session (video framing, audio levels, ...) and another one just focused on subtitles typing on another computer.
• Should we keep a record of what's been typed on the local machine?
  That way the full transcription of a session would be available immediately after it has been stopped. Then it can be used in post-production and be integrated as you wish.

Tell what you think about it, I'd love to know if you have different ideas or even more interesting feature to come up with.
I'm sure @sudoman has also some stuff to say about this feature.