User:Bharathwaaj/ISO/IEC 13818

ISO/IEC 13818 is an ISO standard, published in 13 November 1994 for generic coding of moving pictures and audio. It addresses the combining of one or more elementary streams of video and audio, as well as other data, into single or multiple streams which are suitable for storage or transmission. This system specifies two forms of coding:

1. Transport Stream

2. Program Stream

Program Stream
The program stream results from combining one or more streams of PES packets, which have a common time base, into a single stream. A single program can also be made into separate program streams with a common time base.The Program Stream is designed for use in relatively error-free environments and is suitable for applications which may involve software processing of system information such as interactive multi-media applications. Program Stream packets may be of variable and relatively great length.

Transport Stream
The Transport Stream is a format which is used to combine one or more programs with one or more independent time bases into a single stream. PES packets made up of elementary streams that form a program share a common timebase. The Transport Stream is designed for storage or transmission in error prone and noisy environments. Transport Stream packets are 188 bytes in length.

Program and Transport Streams are designed for different applications and their definitions do not strictly follow a layered model. It is possible and reasonable to convert from one to the other; however, one is not a subset or superset of the other. In particular, extracting the contents of a program from a Transport Stream and creating a valid Program Stream is possible and is accomplished through the common interchange format of PES packets, but not all of the fields needed in a Program Stream are contained within the Transport Stream; some must be derived. The Transport Stream may be used to span a range of layers in a layered model, and is designed for efficiency and ease of implementation in high bandwidth applications.

Packetized Elementary Stream
PES packets are the logical units of Transport and Program Stream. Their size is variable and is usually larger than the size of a TS Packet. A PES Stream is usually formed by continuous sequence of PES packets obtained as bytes from the elementary stream. The resultant PES Stream will include fields like Elementary Clock Stream Reference (ECSR) and Elementary Stream Rate (ESR).