jPlayer is obsolete
The jPlayer library has not been updated in two years. I have not found any active work. It never supported subtitles, and it seems it will never do.
The most complete alternative is VideoJS. It supports tracks (subtitles and captions), languages, covers, the skinning is pure CSS and there is an online skin designer, there are a ton of plugins and development is active. The biggest downside (other than the porting work itself) is the license: Apache 2.0, which is incompatible with the GPLv2.
What is the plan for the future?