An elementary stream (ES) as defined by the
MPEG
The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...
communication protocol is usually the output of an
audio encoder
An audio codec is a device or computer program capable of encoding or decoding a digital data stream (a codec) that encodes or decodes audio. In software, an audio codec is a computer program implementing an algorithm that compresses and decompres ...
or
video encoder
A video decoder is an electronic circuit, often contained within a single integrated circuit chip, that converts base-band analog video signals to digital video. Video decoders commonly allow programmable control over video characteristics such as ...
. An ES contains only one kind of data (e.g. audio, video, or closed caption). An elementary stream is often referred to as "elementary", "data", "audio", or "video"
bitstream
A bitstream (or bit stream), also known as binary sequence, is a sequence of bits.
A bytestream is a sequence of bytes. Typically, each byte is an 8-bit quantity, and so the term octet stream is sometimes used interchangeably. An octet may ...
s or streams. The format of the elementary stream depends upon the codec or data carried in the stream, but will often carry a common header when
packetized into a
packetized elementary stream.
Header for MPEG-2 video elementary stream
General layout of MPEG-1 audio elementary stream
The digitized sound signal is divided up into blocks of 384 samples in Layer I and 1152 samples in
Layers II and
III. The sound sample block is encoded within an audio frame:
* header
* error check
* audio data
* ancillary data
The header of a frame contains general information such as the MPEG Layer, the
sampling frequency
In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples".
A sample is a value of the signal at a point in time and/or sp ...
, the number of channels, whether the frame is
CRC protected, whether the sound is the original:
Although most of this information may be the same for all frames, MPEG decided to give each audio frame such a header in order to simplify synchronization and bitstream editing.
See also
*
MP3
MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...
*
Packetized elementary stream
*
MPEG program stream
Program stream (PS or MPEG-PS) is a container format for multiplexing digital audio, video and more. The PS format is specified in MPEG-1 Part 1 (ISO/IEC 11172-1) and MPEG-2 Part 1, Systems (ISO/IEC standard 13818-1/ITU-T H.222.0). The MPEG-2 ...
*
MPEG transport stream
MPEG transport stream (MPEG-TS, MTS) or simply transport stream (TS) is a standard digital container format for transmission and storage of audio, video, and Program and System Information Protocol (PSIP) data. It is used in broadcast systems ...
External links
ISO/IEC 11172-3:1993 Information technology -- Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s -- Part 3: Audio
{{Compression formats
MPEG