Glossary¶
Brief definitions of digital broadcasting and network transmission terms that are used in the manual and in the interface without explanation.
MPEG-TS transport stream¶
- SPTS¶
Single Program Transport Stream — a transport stream with a single program (one TV channel). The streamer’s basic unit of work (SPTS streams).
- MPTS¶
Multi Program Transport Stream — a transport stream with several programs, for example a DVB multiplex (MPTS streams).
- PID¶
Packet Identifier — a 13-bit number in the header of every transport stream packet. Packets of one component — video, audio, a service table — carry the same PID. PID 8191 is reserved for null (NULL) packets.
- PAT¶
Program Association Table — the table of the stream’s programs, always on PID 0. For each program it gives the program number and the PID of its PMT table.
- PMT¶
Program Map Table — the table of a program’s composition: the PIDs of video, audio, subtitles and data, as well as the PID on which the PCR stamps are carried.
- NIT¶
Network Information Table — the DVB network table: the network parameters and the composition of its transport streams. Carried on PID 16.
- CC¶
Continuity Counter — a 4-bit continuity counter in the packet header, separate for each PID. A skipped value means packet loss, so CC errors are the first sign of delivery problems (Analyzer).
- PCR¶
Program Clock Reference — the program’s reference time stamps at a frequency of 27 MHz. From them the receiver recovers the transmitter’s clock frequency. The analyzer measures PCR interval, drift and accuracy (Analyzer).
- PTS¶
- DTS¶
Presentation Time Stamp and Decoding Time Stamp — the presentation and decoding time stamps of a frame in the PES header, at a frequency of 90 kHz. DTS differs from PTS only for frames that are decoded earlier than they are presented.
Network and delivery¶
- Unicast¶
Delivery of a stream to a single recipient address.
- Multicast¶
Delivery of a stream to a group address (range 224.0.0.0–239.255.255.255): the stream is sent into the network once, and copies are received by everyone who has subscribed to the group. The receiver announces the subscription via the IGMP protocol; switches and routers must support multicast. The source-specific multicast (SSM) variant additionally specifies the source address.
- Listener¶
- Caller¶
The two sides of a PS1 and SRT connection. The listener waits for a connection on its own port; the caller connects to a remote address itself. Which side transmits the stream does not depend on this (SRT).
