#52 Support for on-the-fly XSUB generation

[Radovan Skolnik]

I found that PS3 (and other players) now support XSUB streams for subtitles - see http://en.wikipedia.org/wiki/DivX#DivXSubtitles.28XSUB.29 It would be great to add support for on-the-fly XSUB addition from .srt or .idx/.sub files (via transcoding?). It basically means to create additional stream holding the subtitles when streaming video.