MPEG systems synchronize media by inserting time stamps at the sending device. A program clock reference - PCR- is a source of timing information that is used to coordinate the decoding and sequencing of media streams (elementary streams) that are contained in a program stream.

Because some frames (such as b-frames) must be decoded using information from frames that are received at a later time, a decoding time sequence may be used. A decode time stamp is reference timing values that are included in MPEG packet elementary streams (digital audio, video or data) that are used to control the time alignment of media within a program for decoding.

A presentation time stamp - PTS - is reference timing values that are included in MPEG packet elementary streams (digital audio, video or data) that are used to control the time alignment of media within a program.