Soft Subtitles and mp4/mov subtitles

Is there any way of adding subtitles to a video without having to re-encode them? I think this is called soft-subtitles.

Also, I have a bunch of mp4/mov files. I tried to add subtitles on those videos by re-encoding them and it did not work. The subtitles files are in the same folder with the same name as the videos. Does it only works to avi files?

Adding soft subtitles is not supported in the current versions 2.6 and 2.7. It will be added to version 3.0