Questions about .mkv format video support

[luckyaduGithub]

When you need to convert .mkv video, the warning "Unrecognized file type" often appears. Anyone else having the same problem?

[nagadomi]

The reason for that error is that the mimetype for .mkv is not defined in your OS.
It is defined in my test Windows env, but there may be cases where it is not.

I changed to make .mkv explicitly defined. Run update.bat and try again.

[luckyaduGithub]

Awesome, thanks a lot for the fix!