The M2TS file extension is associated with BDAV MPEG-2 transport stream used on Blu-Ray discs. The BDAV Container format is based on the standard MPEG-2 TS (transport stream) Both Blu-ray and HD DVD use transport streams, compared to DVD's program streams, to store video, audio, and other streams. This allows multiple video programs to be stored in the same file so they can be played back simultaneously, giving a Picture In Picture effect. BDAV was designed in part to provide compatibility between AVCHD digital camcorders and Blu-ray players. It's comparable to the DVD formats used for standalone DVD recorders, DVD+VR and DVD-VR because it's designed primarily for authoring simple Video/Audio content with no menus.