program clock reference (digital-TV) (PCR)

With digital TV, the transport stream( TS) consists of a large number of multiplexed TV programs, each of which must be synchronized on the receiving side. Each individual decoder must be synchronized to the received TV signal. This synchronization is performed using the Program Clock Reference ( PCR).

The Program Clock Reference (PCR) is transmitted as a time stamp in the program stream( PS) from digital TV. The decoder derives its reference time from it.

The Program Clock Reference is decisive for synchronizing the System Time Clock( STC) between transmitter and receiver. Synchronization can be affected by delay times within the system, for example if the link goes over several links and the delay times change. In addition, the Program Clock Reference can be affected by multiplexing multiple program streams.

If it is a program stream with MPEG-2, then the clock reference is 27 MHz, from which the decoder on the receiving side also derives 27 MHz as the System Time Clock (STC) for its synchronization.