MP4 is an extension defined by MPEG-4 video standard and AAC audio standard. It is a container that supports all kinds of media such as video, audio, subtitles, 2D and 3D graphics. It is possible to open MP4 file with almost any player on Windows but on Mac you should use a plug-in or just convert the file to another format.

MTS is a high definition video extension developed by Sony and Panasonic companies for their high-definition consumer video cameras. Later these companies joined their forces in the Blu-ray Disc Association. AVCHD technology supports 720p and 1080i resolution. The format uses MPEG-2 or MPEG-4 codec for video compression and Dolby Digital AC-3 for audio compression. Blu-Ray players can playback MTS videos without compression.