Set when adaptation extension data is present Set when transport private data is present Set when splice countdown field is present
Set when this stream should be considered "high priority" Set when the stream may be decoded without errors from this point Set if current TS packet is in a discontinuity state with respect to either the continuity counter or the program clock reference Number of bytes in the adaptation field immediately following this byte Payload may be PES packets, program specific information (below), or other data. Present if adaptation field control is 01 or 11. Present if adaptation field control is 10 or 11. Incremented per-PID, only when a payload flag is set. Sequence number of payload packets (0x00 to 0x0F) within each stream (except PID 8191) Packet Identifier, describing the payload data.ġ1 – adaptation field followed by payload, Set when the current packet has a higher priority than other packets with the same PID. This field allows a receiver that started reading mid transmission to know when it can start extracting data. The first byte of the payload will indicate where this new payload unit starts. Set when this packet contains the first byte of a new payload unit. Set when a demodulator can't correct errors from FEC data indicating the packet is corrupt. The 188-byte packet size was originally chosen for compatibility with Asynchronous Transfer Mode (ATM) systems. Packets are 188 bytes in length, but the communication medium may add additional information. All header fields are read as big-endian. Each packet starts with a sync byte and a header, that may be followed with optional additional headers the rest of the packet consists of payload. Elements Packet Ī network packet is the basic unit of data in a transport stream, and a transport stream is merely a sequence of packets. Transport streams tend to be broadcast as constant bitrate (CBR) and filled with padding bytes when not enough data exists. This is particularly important for videoconferencing, where large frames may introduce unacceptable audio delay. Many streams are often mixed together, such as several different television channels, or multiple angles of a movie.Įach 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 MKV, which generally wrap each frame into one packet. The receiver parses and decodes one of the streams.Ī 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 or JPEG 2000 video), text and pictures for subtitles, tables identifying the streams, and even broadcaster-specific information such as an electronic program guide. Multiple MPEG programs are combined then sent to a transmitting antenna. Transport stream is specified in MPEG-2 Part 1, Systems, formally known as ISO/IEC standard 13818-1 or ITU-T Rec.
Further, a transport stream may carry multiple programs. Transport streams differ from the similarly-named MPEG program stream in several important ways: program streams are designed for reasonably reliable media, such as discs (like DVDs), while transport streams are designed for less reliable transmission, namely terrestrial or satellite broadcast. Transport stream specifies a container format encapsulating packetized elementary streams, with error correction and synchronization pattern features for maintaining transmission integrity when the communication channel carrying the stream is degraded. It is used in broadcast systems such as DVB, ATSC and IPTV. 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.
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