Problem description: mkv videos are unsupported. Supporting legacy formats like avi or wmf is nice but no one uses those today. It would be very important for LO to be able to deal with mkv.
Steps to reproduce:
1. open LO presentation
2. go to menu Tools > Media Player
3. select "open" and select a mkv file
Current behavior: The format of the selected file is not supported.
Expected behavior: File opening fine.
Operating System: Mac OS X
Impress does not support _any_ video format.
It relies on OS components to play video and audio formats,
such as GStreamer on Linux, QuickTime on Mac and
DirectWhatever on Windows.
If you install the right codecs in the OS then it should work.