This free, open-source player supports almost all codecs and container formats, making it ideal for .mkv files [3].
This usually suggests the file was originally an MKV that was remuxed (converted) to MP4, or it is a file with a dual extension, which can sometimes cause playback issues. 2. How to Play the File If the file isn't opening properly: FSDSS-027.mkv.mp4
What is the with the file (e.g., won't play, wrong format)? What device are you trying to play it on? With more details, I can provide a more tailored solution. This free, open-source player supports almost all codecs