Program stream (PS or MPEG-PS) is a container format for multiplexing digital audio, video and more.
The MPEG-2 Program Stream is analogous and similar to ISO/IEC 11172 Systems layer and it is forward compatible.
It is designed for reasonably reliable media such as disks, in contrast to MPEG transport stream which is for data transmission in which loss of data is likely.
Program streams have variable size records and minimal use of start codes which would make over the air reception difficult, but has less overhead.
[citation needed] The MPEG-2 Program stream has provisions for non-standard data (e.g. AC-3 audio or subtitles) in the form of so-called private streams.