Chess.mkv.mp4

How a media player handles depends entirely on its internal data, not the extension:

These are digital "wrappers" that hold video streams, audio streams, subtitles, and metadata. CHESS.mkv.mp4

To understand this file, one must distinguish between containers and codecs: How a media player handles depends entirely on

The secondary (and active) extension indicating an MPEG-4 Part 14 container. 2. Container vs. Codec and metadata. To understand this file