There is only one file type that uses the .MQV extension:
Sony Movie Format File
Proprietary movie format used by Sony devices, such as the the Clie PDA; similar to a .MP4 video file, but uses a different encoding method; playable with Apple QuickTime Player 6 or later.
MQV files can be played within the Palm OS using Sony Movie Player.
Updated: March 28, 2008