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MPEG transport stream (MPEG-TS, MTS) or simply transport stream (TS) is a standard
digital container format A container format (informally, sometimes called a wrapper) or metafile is a file format A file format is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal ide ...
for transmission and storage of
audio Audio most commonly refers to sound In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion ( ...
,
video Video is an electronic Electronic may refer to: *Electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active d ...
, and
Program and System Information Protocol The Program and System Information Protocol (PSIP) is the MPEG The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechn ...
(PSIP) data. It is used in broadcast systems such as DVB,
ATSC Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that ...
and
IPTV Internet Protocol television (IPTV) is the delivery of television Television, sometimes shortened to TV or telly, is a telecommunication Media (communication), medium used for transmitting moving images in grayscale, black-and-white ...

IPTV
. Transport stream specifies a container format encapsulating packetized elementary streams, with
error correction In information theory Information theory is the scientific study of the quantification (science), quantification, computer data storage, storage, and telecommunication, communication of Digital data, digital information. The field was fun ...
and synchronization pattern features for maintaining transmission integrity when the
communication channel A communication channel refers either to a physical transmission medium A transmission medium is a system or substance that can mediate the propagation of signal In signal processing Signal processing is an electrical engineering ...
carrying the stream is degraded. Transport streams differ from the similarly-named
MPEG program stream Program stream (PS or MPEG-PS) is a container format for multiplexing In telecommunications Telecommunication is the transmission of information by various types of technologies over , radio, , or other systems. It has its origin in ...
in several important ways: program streams are designed for reasonably reliable media, such as discs (like
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital elect ...

DVD
s), while transport streams are designed for less
reliable Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), Data reliability, a property of some disk arrays in computer storage * High availability * Reliability (computer ...
transmission, namely
terrestrial Terrestrial refers to things related to land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is situated at elevations above sea level (variable over geologic time frames) and consists main ...
or satellite broadcast. Further, a transport stream may carry multiple programs. Transport stream is specified in ''
MPEG-2 MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU 260px, ITU Monument, Bern The International Telecommunication Union is a specialized agency of the United Nations responsible for all matters related to information and communicati ...
Part 1, Systems'', formally known as ''
ISO/IEC ISO/IEC JTC 1, entitled "Information technology", is a joint technical committee (JTC) of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Its purpose is to develop, maintain and pr ...
standard 13818-1'' or ''
ITU-T The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications Telecommunication is the transmission of information by various types of technologies over , radio, , or other systems. It has its origin ...
Rec. H.222.0''.


Overview

A transport stream encapsulates a number of other substreams, often packetized elementary streams (PESs) which in turn wrap the main data stream using the MPEG codec or any number of non-MPEG codecs (such as AC3 or DTS audio, and
MJPEG Motion JPEG (M-JPEG or MJPEG) is a video compression format A video coding format (or sometimes video compression format) is a content representation format for storage or transmission of digital video content (such as in a data file or bits ...
or
JPEG 2000 JPEG 2000 (JP2) is an image compression Image compression is a type of data compression In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such a ...
video), text and pictures for subtitles, tables identifying the streams, and even broadcaster-specific information such as an
electronic program guide Electronic programming guides (EPGs) and interactive programming guides (IPGs) are menu-based systems that provide users of television, radio Radio is the technology of signaling and telecommunication, communicating using radio waves. R ...

electronic program guide
. Many streams are often mixed together, such as several different television channels, or multiple
angles The Angles ( ang, Ængle, ; la, Angli; german: Angeln) were one of the main Germanic peoples The Germanic peoples were a historical group of people living in Central Europe and Scandinavia. Since the 19th century, they have traditional ...
of a movie. Each stream is chopped into (at most) 188-byte sections and interleaved together; because of the tiny packet size, streams can be interleaved with less latency and greater error resilience compared to program streams and other common containers such as AVI, MOV/ MP4, and , which generally wrap each frame into one packet. This is particularly important for videoconferencing, where large frames may introduce unacceptable audio delay. Transport streams tend to be broadcast as
constant bitrate Constant bitrate (CBR) is a term used in telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, electromagnetic systems. ...
(CBR) and filled with padding bytes when not enough data exists.


Elements


Packet

A
network packet In telecommunications and computer networking, a network packet is a formatted unit of Data (computing), data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the ''Payload ...
is the basic unit of data in a transport stream, and a transport stream is merely a sequence of packets. Each packet starts with a
sync byte In computer networks, a syncword, sync character, sync sequence or preamble is used to synchronize a data transmission by indicating the end of header (computing), header information and the start of data. The syncword is a known sequence of d ...
and a
header Header may refer to: Computers and engineering * Header (computing)In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the h ...
, that may be followed with optional additional headers; the rest of the packet consists of
payload Payload is the object or the entity which is being carried by an aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy ...
. All header fields are read as
big-endian In computing, endianness is the order or sequence of bytes of a word (data type), word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most significan ...
. Packets are 188 bytes in length, but the communication medium may add additional information. The 188-byte packet size was originally chosen for compatibility with Asynchronous Transfer Mode (ATM) systems.


Packet identifier (PID)

Each table or elementary stream in a transport stream is identified by a 13-bit packet identifier (PID). A
demultiplexer In electronics, a multiplexer (or mux; spelled sometimes as multiplexor), also known as a data selector, is a device that selects between several Analog signal, analog or Digital signal (electronics), digital input signals and forwards the sel ...
extracts elementary streams from the transport stream in part by looking for packets identified by the same PID. In most applications,
time-division multiplexing Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fracti ...
will be used to decide how often a particular PID appears in the transport stream.


Programs

Transport stream has a concept of ''programs''. Every program is described by a program map table (PMT). The elementary streams associated with that program have PIDs listed in the PMT. Another PID is associated with the PMT itself. For instance, a transport stream used in digital television might contain three programs, to represent three television channels. Suppose each channel consists of one video stream, one or two audio streams, and any necessary metadata. A receiver wishing to decode one of the three channels merely has to decode the payloads of each PID associated with its program. It can discard the contents of all other PIDs. A transport stream with more than one program is referred to as a multi-program transport stream (MPTS). A single program transport stream is referred to as a single-program transport stream (SPTS).


Program specific information

There are 4 program specific information (PSI) tables: program association (PAT), program map (PMT), conditional access (CAT), and network information (NIT). The MPEG-2 specification does not specify the format of the CAT and NIT.


PCR

To enable a decoder to present synchronized content, such as audio tracks matching the associated video, at least once each 100 ms, a ''program clock reference'' (PCR) is transmitted in the adaptation field of an MPEG-2 transport stream packet. The PID with the PCR for an MPEG-2 program is identified by the ''pcr_pid'' value in the associated PMT. The value of the PCR, when properly used, is employed to generate a ''system_timing_clock'' in the decoder. The system time clock (STC) decoder, when properly implemented, provides a highly accurate time base that is used to synchronize audio and video elementary streams. Timing in MPEG-2 references this clock. For example, the
presentation time stamp The presentation timestamp (PTS) is a timestamp metadata Field (computer science), field in an MPEG transport stream or MPEG program stream that is used to achieve synchronization of programs' separate elementary streams (for example Video, Audio, S ...
(PTS) is intended to be relative to the PCR. The first 33 bits are based on a 90 kHz clock. The last 9 bits are based on a 27 MHz clock. The maximum jitter permitted for the PCR is .


Null packets

Some transmission schemes, such as those in
ATSC Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that ...
and DVB, impose strict constant bitrate requirements on the transport stream. In order to ensure that the stream maintains a constant bitrate, a multiplexer may need to insert some additional packets. The PID 0x1FFF is reserved for this purpose. The payload of null packets is all zeroes, and the receiver is expected to ignore its contents.


Use in digital video cameras

Transport Stream was originally designed for broadcast. Later it was adapted for use with digital video cameras, recorders and players by adding a 4-byte timecode (TC) field to the standard 188-byte packets, resulting in a 192-byte packet. This is what is informally called
M2TS M2TS is a filename extension used for the Blu-ray Disc Audio-Video (BDAV) MPEG-2 Transport Stream (M2TS) container A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shi ...
stream. The
Blu-ray Disc Association The Blu-ray Disc Association (BDA) is the industry consortium A consortium (plural: consortia) is an association Association may refer to: *Club (organization), an association of two or more people united by a common interest or goal *Trade as ...
calls it " BDAV MPEG-2 transport stream". JVC called it
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when used in HDD-based camcorders like GZ-HD7. The timecode allows quick access to any part of the stream either from a media player, or from a non-linear video editing system. It is also used to synchronize video streams from several cameras in a
multiple-camera setup The multiple-camera setup, multiple-camera mode of production, multi-camera or simply multicam is a method of filmmaking and video production Video production is the process of producing video Video is an electronic Electronic may re ...
.


Use in Blu-ray

Blu-ray Disc video titles authored with menu support are in the Blu-ray Disc Movie (BDMV) format and contain audio, video, and other streams in a BDAV container, which is based on the MPEG-2 transport stream format.Afterdawn.co
Glossary – BD-MV (Blu-ray Movie) and BDAV container
, Retrieved on 26 July 2009
Afterdawn.co
Glossary – BDAV container
Retrieved on 26 July 2009
Blu-ray Disc video uses these modified MPEG-2 transport streams, compared to DVD's program streams that don't have the extra transport overhead. There is also the BDAV (Blu-ray Disc Audio/Visual) format, the consumer-oriented alternative to the BDMV format used for movie releases. The BDAV format is used on
Blu-ray Disc recordable Blu-ray Disc Recordable (BD-R) refers to two direct to disc optical disc recording technologies Optical disc authoring Optical disc authoring, including DVD authoring, DVD and Optical disc authoring#Blu-ray Disc, Blu-ray Disc authoring, ...
for audio/video recording. Blu-ray Disc employs the MPEG-2 transport stream recording method. This enables transport streams of a BDAV converted digital broadcast to be recorded as they are with minimal alteration of the packets. It also enables simple stream cut style editing of a BDAV converted digital broadcast that is recorded as is and where the data can be edited just by discarding unwanted packets from the stream. Although it is quite natural, a function for high-speed and easy-to-use retrieval is built in.Blu-ray Disc Association (August 2004
Blu-ray Disc Format, White paper
(PDF) Page 22, Retrieved on 28 July 2009


See also

*
MPEG media transport MPEG media transport (MMT), specified as ISO The International Organization for Standardization (ISO ) is an international standard An international standard is a technical standard A technical standard is an established norm Norm, the Nor ...
(MMT) *
Real-time Transport Protocol The Real-time Transport Protocol (RTP) is a network protocol for delivering audio and video over IP networks. RTP is used in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications ...
(RTP) *
Unidirectional Lightweight Encapsulation {{IPstack The Unidirectional Lightweight Encapsulation (ULE) is a Data link layer protocol for the transportation of network layer packets over MPEG transport streams. Because of the very low protocol overhead, it is especially suited for IP over ...
(ULE)


Notes


References


External links


ITU-T H.222.0 , ISO/IEC 13818-1 Systems Spec Documents

Latest free copy of the spec, October 2014



TSDuck
– Free open-source tool to manipulate MPEG transport streams. {{DEFAULTSORT:Mpeg Transport Stream ATSC Digital container formats MPEG-2 ITU-T recommendations