PROGRAM CLOCK REFERENCE (PCR): While the MPEG are transmit in the transport stream so the program clock reference is also transmit as a time information source in the receiver/decoder. The program clock reference is use for decoder for proper synchronization. The correctly free from error and successfully PCR is acquire is a precondition so the exact data or information can be shown in the receiver or decoder. Generally, the transport stream is use for lengthy distance. Additionally, without being affected by the 27 MHZ clock is used for encoding. So, the encoder clock frequency is not exactly same as the decoder clock frequency. This problem can be resolve by the insertion of the program clock reference (PCR). PCR explanation and use: The PCR is a timing information in the transport stream and the program clock reference is frequently transmitted with each and every program of the transport stream for proper synchronization between the encoder and the decoder. The PCR values of a program are perfectly assigned to the Packet identification i.e. With the aim to proper synchronization with the broadcasting satellite Television TV, a program clock reference (PCR) timestamp is embedded within the transport stream packet. This timestamp is enable to keep the proper synch to the receiver device time clock with the transmitting device time clock. This is to make sure that the photo is present at the proper time within the receiver’s show unit. If those clocks are not properly synch or get out of sync, both the images of the encoder side and the decoder side are present too speedy and the image buffer will underflow, or they may be present too sluggish and the buffer will overflow Figure 7 indicates how the PCR is utilized by the decoder to recreate a remote version of the 27-MHz clock for every program. The encoder clocks power a continuously strolling binary counter, and the value of those counters are sampled periodically and located inside the header adaptation fields as the PCR. Every encoder produces packets having a unique PID. The decoder acknowledges the packets with the proper PID for the chosen program and ignores others. On the decoder, a VCO generates a nominal 27-MHz clock and this drives a nearby PCR counter. The local PCR is in comparison with the PCR from the packet header, and the difference is the PCR section errors. this mistake is filtered to manipulate the VCO that finally will carry the local PCR count number into step with the header PCRs. Substantial VCO filtering guarantees that jitter in PCR transmission does not modulate the clock. PCR Monitoring: The PCR monitoring consist of the following parts which are shown below the measurement is defined under the following and it has to be achieved constantly or periodically. ? PCR repetition error: The PCR value is obtained at minimum forty per Millisecond. ? PCR discontinuity indicator error: This error can happen if the difference between two consecutive PCR values is out of range 100ms. ? PCR accuracy error: This is happens if the distinction between the present or current day PCR value and the value which is described within the TS. PCR Transmission: In the transport stream with each and every program the PCR is dispatch. The PCR values have a unique PID that is packet identification so every program consist a unique PID which is transmitted in the transport stream. The PID is available in the program map table (PMT), basically the video elementary stream PID of the program is useful for the transmission in transport stream packets. It’s not a mandatory that each transport stream (TS) stream packet have a PID with the PCR value and it is to be insert at the exact time in the decoder at forty per hundred millisecond because of this, the PCR value is transmitted in an elective field of the extendable header (adaptation field) inside the transport stream packet. The PCR value is made up of two combination that is PCR base and PCR extension. The PCR is a 42 bit lengthy with the 27 MHZ frequency. Since, the PCR base is a 33 bit value and the rest remaining is 9 bit value of extension. ? Adaptation_field_length: This is an 8-bit field lengthy which is used to define the bytes ranges in the fields following the adaptation field length. ? Discontinuity_indicator: There are two possibilities available in this field. If it is set to zero it means discontinuity state is false and if it is set to one ii means the discontinuity state is proper. Hence, it is a 1 bit field. ? Random_access_indicator: It’s is shown the random get entry with the identical PID, transport stream packets and it also shown the present transport stream packet. ? PCR_flag: There are two possibilities in this field if it is one it means adaptation field contain a PCR field and if it is zero it means adaptation field ? OPCR_flag : There are two possibilities in this field if it is one it means adaptation field contain a OPCR field coded in 2 elements and if it is zero it means adaptation field doesn’t contain a OPCR field. The PCR is a forty two bit long which is divided into two parts that is PCR base and PCR extension (ext). The first part of PCR is a PCR base and it is a 33 bit value and the rest part of PCR is PCR ext and it is a 9 bit value which is coded in the element. The PCR base and extension is notify like PCR_base and PCR_ext. Hence, the PCR is a total forty two bit long with the 27 MHZ frequency which should be match to the decoder clock for proper synch. ? Original_Program_Clock_Reference: The optionally OPCR is a forty two bit long which is divided into two parts that is PCR base and PCR extension (ext). The first part of PCR is an OPCR base and it is a 33 bit value and the rest part of PCR is OPCR ext and it is a 9 bit value which is coded in the two element. The PCR base and extension is notify like OPCR_base and OPCR_ext. Hence, the OPCR is a total forty two bit long with the 27 MHZ frequency which should be match to the decoder clock for proper synch. PMT (PROGRAM MAP TABLE): This table give the information related to the program such as program number. It also give the information of the packet identification like which packet contain the data like it’s a audio data, video data etc. program map table each and every related PID is available. Some useful syntax and number of bits mnemonic in the program map section or program map table (PMT) are shown in table number 6. The PCR PID i.e., Program Clock Reference packet identification is available in program map table and the program map table is available in program specific information i.e., PSI and So, we can say that it is a hierarchy tree of transport stream. Semantic meaning of fields in Transport Stream program outline: ? Table_id: It is set to 0x02 for the TS program and it is an eight bit. ? Section_syntax_indicator: It is set to one and it is an one bit field. ? Section_length: The starting two bits will be ’00’.the section length field consisting of the CRC because the ending 10 bits define the range of bytes. ? Program_number: It is present that which program is dedicated to the program map PID and, which program have the TS. ? Current_next_indicator: This is consist of two parts if it is one it means TS program map section dispatched is presently applicable. While if it is set to zero it means TS program map section dispatched is not presently applicable. Since, it is a 1 bit field. ? PCR_PID: In the transport stream the PCR is a thirteen bit field which give the particular information that this PCR field is valid for a particular program number. The value will be 0x1fff if no PCR is available. ? Program_info_length: The starting bit is ’00’ and the ending bit is 10 it present the range of bytes. Hence, it is a 12 bit field. ? Stream_type: It shows the stream type like our programs have which type of stream either it is an audio PID, video PID etc in the transport stream packet.