If you need to change the file format for compatibility (e.g., to MP4 for a TV) or change its name:
If the file has no extension (e.g., just AgADgwADyby5Vw ), rename it and add .mkv to the end to make it playable. AgADgwADyby5Vw.mkv
You can right-click the file and rename it to something descriptive like my_video.mkv without damaging it. Conversion (Using VLC): Go to Media > Convert / Save . Add the AgADgwADyby5Vw.mkv file. If you need to change the file format for compatibility (e