What is a PES Audio Bitstream?

PES stands for Packetised Elementary Stream.

The term arises from the MPEG audio compression specification: specifically, in MPEG-2 system layer documentation (draft ISO/IEC 13818-1 "MPEG-2 system layer documentation").

The system layer part of MPEG-2 defines how one or more 'elementary streams' of video, audio or other data may be combined into single or multiple streams for storage or transmission. Two sorts of 'stream' are defined: the Transport Stream and the Program Stream - each is optmimised for a different set of applications but both use time stamps to synchronize the decoding and presentation of the video and audio information, while ensuring that data buffers in the decoders do not overflow or underflow.

A 'stream' implies a continuous stream of data - bits or bytes - much as in the UNIX concept of a stream. For communications, streams could tie up a communications link for a long time so a stream of data is often split up into short sections called 'packets' which can then be sent separately - perhaps over many different circuits - and then be reassembled at the receiver into the required continuous stream. A 'stream' split up into 'packets' can be called a 'Packetised Elementary Stream'.