You can have a try on Brorsoft Video Converter to set an optima preset for PS4 for playback without any issue.

@onyrew: A fast method is to change MKV to MP4 format with Handbrake or a professional video converter like Brorsoft Video Converter if you need.

It's a painful experience when users wanna watch VOB files on PS3. That's because PS3 doesn't support VOB format. So if you would like to play VOB on PS3 freely, converting VOB to PS3 compatible format is your ideal choice.