MPEG-2 Program Streams, also referred to as MPEG or MPEG-2 PS or sometimes just PS, are the standard format for storing MPEG-2 video muxed with other streams. This format is optimized for efficient storage, and is the basis for how DVD-Video VOBs are muxed. The format is based on MPEG-1's System Streams.
Program streams use Time Domain multiplexing, meaning that the video and audio files are split into smaller pieces and a small amount of video is followed in the PS file by audio of the same duration, which is followed by the next bit of video and audio of the same length, etc, ...
Each piece of an individual elementary stream in a PS file has timing information created during the muxing process which tells the decoder their position in time relative to the beginning of the file. That way the decoder can keep all streams synchronized during playback.
Due to a lack of design consideration for reliable network transmission without loss of data, Program Streams aren't suitable for Streaming applications like IPTV or Digital Television
