Microsoft have updated the Xbox Video app for Windows Phone 8.1 adding a couple of nice features. The update adds support for SRT subtitles on personal videos so if you use subtitles on your videos Windows Phone 8.1 now supports that. The other new feature is you can now delete downloaded movies or TV shows from your phone freeing up space. There is also the usual polish and general improvements.
Details from Microsoft:
This update (version 1.6.315.0 on Windows Phone 8 and 2.6.315.0 on Windows Phone 8.1) includes:
SRT subtitle support for personal videos (Windows Phone 8.1 only)
Better delete: easily delete downloaded movies and TV episodes from your phone or remove a movie or TV show from your phone’s collection
Polish fixes and general improvements