The ISO base media file format (ISOBMFF) is a container file format that defines a general structure for files that contain time-based multimedia data such as video and audio.It is standardized in ISO/IEC 14496-12, a.k.a. MPEG-4 Part 12, and was formerly also published as ISO/IEC 15444-12, a.k.a. JPEG 2000 Part 12.