If the file has no extension (e.g., just AgADgwADyby5Vw ), rename it and add .mkv to the end to make it playable.
To give you more specific advice on this file, could you tell me: AgADgwADyby5Vw.mkv
Matroska Video, a flexible, open-standard video container format that can hold a high number of video, audio, picture, or subtitle tracks in one file [1]. If the file has no extension (e
Because MKV files can use various codecs, you need a player that supports a wide range of formats. just AgADgwADyby5Vw )