 The following corporations filed declarations with ISO saying they held patents for the MPEG-1 Video (ISO/IEC-11172-2) format, although all such patents have since expired.Part 1 of the MPEG-1 standard covers "systems", and is defined in ISO/IEC-11172-1.MPEG-1 Systems specifies the logical layout and methods used to store the encoded audio, video, and other data into a standard bitstream, and to maintain synchronization between the different contents.