Introduction
Today every subscriber wants smooth playback of videos for real time video applications. They do not want any type of interception or delay in the delivery of videos or programs.
So this is mandatory for a service provider to offer smooth playback of videos and programs because it denotes the quality of service. To understand more about it in this article we will discuss what is PCR, how much important PCR is for proper delivery of real time video services to subscribers and PCR Monitoring.
What Is PCR
PCR stands for Program Clock Reference. PCRs are transmitted from transmitter side to synchronize the Transmitter System Time Clock with Receiver System Time Clock. PCRs are transmitted in maximum interval of 100 miliseconds.
In Other Words PCR is 16 bit command and status register. it is 27 MHz clock reference inserted in the encoder side for smooth playback of programs without any latency at decoder side for real time applications.
Thus PCR PIDs are also inserted in multiplexer side which contains a piece of information. So this piece of information is used to measure the jitter. A Jitter denotes the inaccuracies in the Program Clock Reference. PCR Jitter Schemes are used to avoid the jitter or we can say PCR correction is used to make output jitter value close to input jitter value. By doing so it avoids the latency.
PCR’s accuracy in encoder denoted by PCR_AC
PCR’s Drift rate in encoder denoted by PCR_DR
PCR’s Frequency Offset denoted by PCR_FO
PCR’s Overall Jitter denoted by PCR_OJ
PCR Monitoring
In the PCR monitoring system delay in the transport stream is measured. In other words PCR reach position is measured at receiver end that how close it is. Based on PCR position PCR errors are measured.
There are various kinds of devices available in the market for PCR monitoring. In which some of smart monitoring devices automatically detect the PCR errors and generate a alarm for it. While on the other side we need to manually check the PCR errors.
There are some low cost PCR monitoring devices. These devices are connected to the computer via USB port. These cheap monitoring devices uses the computer power to read the stream for PCR monitoring.
A Stream Analyzer is used to do the PCR Monitoring. In PCR’s Monitoring the PCR accuracy test is only for testing of Multiplexer and Encoder.
Conclusion Of Program Clock Reference
As we have discussed above a PCR is 27 MHz program clock reference PID is inserted in multiplexer or encoder for smooth video playback at decoder for real time video applications. A proper implementation of PCR PID mean no any latency. Inaccuracies in the PCR denoted by jitter. A dectak device is used for PCR monitoring.
Know More About What Is PSI SI Tables
