188 bytes
Container & packets
The transport stream packet size. Four times the 47-byte ATM AAL-1 payload, chosen when ATM was expected to carry broadcast.
🛠️ Interactive Tool
DVB & Transport Stream Glossary
95 terms drawn from the sheets on this shelf, each defined plainly and linked to wherever it is covered properly. 38 of them carry a Watch out note, because the term is routinely used to mean something it does not — those are the ones worth reading even if you know the word.
All terms
204 bytes
Container & packets
188 bytes plus 16 bytes of Reed-Solomon parity, as carried over a satellite link.
Watch out: Quote the 204-byte bitrate when sizing a transponder and the 188-byte figure when sizing an IP link — they describe the same stream.
ABR Adaptive Bitrate
Delivery & IP
Offering several renditions so a client can switch quality as its bandwidth changes.
AC-3 / E-AC-3 / AC-4
Codecs
Dolby audio codecs carried in DVB, identified by descriptor rather than by stream type.
Adaptation field
Container & packets
An optional variable-length header extension carrying the PCR, discontinuity and random-access flags, splice countdown and stuffing.
Watch out: Each of its fields is present only when its flag is set, so it must be walked in order rather than read at fixed offsets.
AVC / H.264 Advanced Video Coding
Codecs
The dominant HD broadcast video codec. Carried in a transport stream as stream type 0x1B.
AWGN Additive White Gaussian Noise
Modulation & RF
The idealised channel model the MODCOD tables assume. A satellite link approximates it; a terrestrial one does not.
BAT Bouquet Association Table
Signalling
Groups services into commercial bouquets, which may span multiple transports.
BBFrame Baseband Frame
Encapsulation
The DVB-S2 layer between FEC and the transport stream. Raw BBFrame mode has the demodulator emit these instead of de-encapsulating in hardware.
Watch out: Hardware MIS de-encapsulation drops roughly 9 % on a bursty T2-MI feed, which destroys the whole-packet T2-MI CRC and yields an undecodable inner multiplex on an RF-perfect carrier.
BISS Basic Interoperable Scrambling System
Conditional access
The EBU's contribution-feed answer to CA: modes 0, 1, E and CA. BISS2 replaced CSA1 with CISSA and DES with AES-128.
BISS-CA
Conditional access
BISS with in-stream key exchange, combining AES-128 and RSA to grant and revoke individual decoders in real time. Open and royalty-free.
C/N Carrier-to-Noise ratio
Modulation & RF
Carrier power over noise power in a stated bandwidth.
Watch out: Meaningless without the bandwidth. In symbol-rate bandwidth C/N equals Es/N0; in occupied bandwidth it is lower by 10·log₁₀(1+α).
CA Conditional Access
Conditional access
The proprietary layer that delivers scrambling keys only to entitled receivers.
Watch out: Distinct from scrambling, which is standardised and interoperable. Almost every CA confusion comes from collapsing the two.
CA_descriptor tag 0x09
Signalling
Carries a CA system identifier and the PID where that system's messages live.
Watch out: Placement decides meaning: in the CAT it points at EMMs; in a PMT it points at ECMs. Same tag, same structure, different referent.
CAID CA System Identifier
Conditional access
The 16-bit value identifying which CA system a CA_descriptor refers to.
CAM Conditional Access Module
Conditional access
The card carrying the CA system's secure logic, typically with a smartcard.
Watch out: Only legacy modules require a CI slot adjacent to the tuner. Professional multi-CAM equipment descrambles an IP-delivered MPTS perfectly well.
CAT Conditional Access Table
Signalling
On PID 1. Lists the CA systems present in the multiplex and where their EMM streams are.
Watch out: Required but empty for BISS modes 1 and E — an empty CAT on a BISS feed is correct, not a fault.
CDN Content Delivery Network
Delivery & IP
Distributed caches that serve segments close to viewers.
CI / CI+ Common Interface
Conditional access
The slot standard for a descrambling module in a tuner or receiver. CI+ adds link protection and requires certificates.
CISSA Common IPTV Software-oriented Scrambling Algorithm
Conditional access
AES-128 in CBC mode with a constant IV, specified for DVB-IPTV. Fully public, so implementable in software by anyone.
Watch out: Encrypts whole 16-byte blocks, leaving the trailing 1–15 bytes in the clear. Plaintext-looking tail bytes are not evidence a packet is unscrambled.
CMAF / ISOBMFF Common Media Application Format / ISO Base Media File Format
Delivery & IP
The segment container used by DASH and modern HLS, in place of transport stream.
Continuity counter CC
Container & packets
A 4-bit per-PID counter that increments on each payload-carrying packet, used to detect loss.
Watch out: It wraps every 16. A loss of exactly 16 packets gives an observed step of 1 and is completely invisible; a loss of 15 is reported as a duplicate. Measured, not theorised.
Control word CW
Conditional access
The symmetric key the scrambler uses. 64-bit for CSA v1 and v2, 128-bit for CSA v3 and CISSA.
Crypto period CP
Conditional access
The span during which one control word is in use, after which the key changes.
Watch out: Shortening it for security makes ECM delivery timing harder, because it reduces the time available for the round trip.
DDCI Decoupled Common Interface
Conditional access
Addressing a CI slot independently of the tuner that received the stream, so a stream from one source can be descrambled elsewhere.
Descriptor
Signalling
A tagged, variable-length structure carried inside tables, conveying everything from service names to audio codecs.
Watch out: The same tag can mean different things depending on which table and which loop it sits in.
DVB-CSA Common Scrambling Algorithm
Conditional access
The broadcast scrambling algorithm. v1 and v2 use a 64-bit control word; v3 uses 128-bit, built from an AES-128 variant plus the DVB-confidential XRC.
Watch out: CSA v1 is the default a receiver must assume when no scrambling_descriptor is present — often not what is actually in use.
Eb/N0
Modulation & RF
Energy per information bit over noise power spectral density. Eb/N0 = Es/N0 − 10·log₁₀(η).
Watch out: QPSK 1/4 has Es/N0 of −2,35 dB and Eb/N0 of +0,75 dB — the same link. A carrier really can sit below the noise floor.
ECM Entitlement Control Message
Conditional access
Carries the control word for the current and next crypto period, encrypted under CA keys, with the access criteria. Repeated every few seconds.
ECMG / EMMG ECM / EMM Generator
Conditional access
CA-vendor components that turn control words into ECMs and subscriber data into EMMs.
EIT Event Information Table
Signalling
The electronic programme guide: what is on now, next, and on schedule.
EMM Entitlement Management Message
Conditional access
Carries subscriber entitlements to an individual receiver or group. Cycled over hours to weeks.
Watch out: Because entitlements persist, a broken EMM path shows no symptom for days, then fails services in expiry-date order rather than fault order.
Es/N0
Modulation & RF
Energy per transmitted symbol over noise power spectral density. The quantity the DVB MODCOD tables give.
Even / odd key
Conditional access
Two key registers, selected by a bit in each packet header, so a key change needs no timing precision from the receiver.
Watch out: Rhythmic breakup tracking the crypto period means one parity is failing — a key delivery problem, not signal.
FEC Forward Error Correction
Modulation & RF
Redundancy added so the receiver can repair errors. DVB-S used convolutional plus Reed-Solomon; DVB-S2 uses LDPC plus BCH.
FECFRAME
Modulation & RF
The block the LDPC code operates on. Normal is 64 800 bits; short is 16 200, with S2X adding medium 30 780 and other lengths.
Watch out: Short FECFRAMEs cost 0,2 to 0,3 dB more than the tabulated figures, per the standard.
FEF Future Extension Frame
Encapsulation
A gap deliberately left in a DVB-T2 frame structure for other uses. Signalled by its own T2-MI packet types.
HE-AAC High-Efficiency Advanced Audio Coding
Codecs
A widely used broadcast audio codec, also signalled by descriptor.
HEVC / H.265 High Efficiency Video Coding
Codecs
The UHD broadcast video codec, carried as stream type 0x24.
Watch out: An HEVC service still rides inside an MPEG-2 Transport Stream. Container and codec are different questions.
HLS / DASH HTTP Live Streaming / Dynamic Adaptive Streaming over HTTP
Delivery & IP
Segmented adaptive-bitrate delivery over HTTP, used for consumer streaming.
Watch out: DVB-DASH and DVB-I use ISOBMFF and CMAF segments, not transport stream. Do not point a TS demux at a CMAF segment.
IGMP Internet Group Management Protocol
Delivery & IP
How a receiver joins and leaves a multicast group.
Implementation margin
Modulation & RF
The gap between a real receiver and the ideal simulated one the standard tabulates.
Watch out: Comes from the receiver's datasheet, not from any standard. Margin is bought with bandwidth — 3 dB of unnecessary margin can cost a third of your capacity.
ISI Input Stream Identifier
Modulation & RF
Selects one transport stream from a multistream (MIS) carrier where several share the same physical carrier.
Watch out: Omit it on a multistream carrier and you get nothing usable. The failure looks like a signal problem.
LDPC Low-Density Parity-Check
Modulation & RF
The inner code in DVB-S2 and later, responsible for performance close to the theoretical limit.
Watch out: Produces a threshold cliff rather than graceful degradation: half a decibel above threshold is perfect, half a decibel below fails almost completely.
LNB Low-Noise Block downconverter
Modulation & RF
The unit at the dish that amplifies the satellite signal and shifts it to a lower intermediate frequency.
Watch out: Its phase noise is a real cost at high-order APSK, and it is excluded from the standard's ideal figures.
Locked tuner
Delivery & IP
A tuner locked to a satellite position and one frequency at a time — both selectable, and changeable, from your client area — kept in a hot state so no tuning delay applies, and shared between clients.
Watch out: Nothing is filtered for you — pids=all or an explicit list is client-controlled per session. Cannot scan for new transponders; you can analyse only the services on that frequency.
MIS Multiple Input Stream
Modulation & RF
A DVB-S2 carrier bearing several independent transport streams, selected by ISI.
MODCOD Modulation and Coding
Modulation & RF
A modulation and code-rate pair, such as 8PSK 2/3, which together set spectral efficiency and the required carrier-to-noise ratio.
MPE Multi-Protocol Encapsulation
Encapsulation
Carrying IP datagrams inside a transport stream.
MPEG-2 Transport Stream MPEG-2 TS, ISO/IEC 13818-1
Container & packets
The container format that carries DVB broadcast: a continuous sequence of fixed 188-byte packets, each tagged with a PID.
Watch out: Names MPEG-2 Systems (ISO/IEC 13818-1), not MPEG-2 Video (13818-2). An H.265 UHD service is HEVC video inside an MPEG-2 Transport Stream — both at once.
MPTS / SPTS Multi- / Single-Programme Transport Stream
Container & packets
A stream carrying several services, versus one carrying a single service.
Multicast
Delivery & IP
One-to-many IP delivery, where the network replicates packets and receivers join a group via IGMP.
NIT Network Information Table
Signalling
Describes the physical network — transports, frequencies and delivery parameters.
Null packet PID 0x1FFF
Container & packets
Stuffing. Carries no information and exists to pad a stream to a constant bitrate.
Watch out: Never scrambled and never carries data. A null packet marked as scrambled is a fault.
PAT Program Association Table
Signalling
On PID 0. Lists every service in the multiplex and the PID of each service's PMT. The entry point to everything.
PCR Program Clock Reference
Container & packets
The transmitter's clock, sent in the adaptation field so receivers can lock to it. A 33-bit base at 90 kHz plus a 9-bit extension at 27 MHz: PCR = base × 300 + ext.
PES Packetised Elementary Stream
Container & packets
The wrapper around audio, video and subtitle data, up to 65536 bytes, split across many TS packets.
PID Packet Identifier
Container & packets
A 13-bit label in every packet header identifying which stream the payload belongs to. 8192 possible values.
PID 8192
Container & packets
An out-of-range sentinel — 13 bits can only express 0–8191 — used by SAT>IP to mean all PIDs rather than a real stream.
PLP Physical Layer Pipe
Encapsulation
An independently modulated and coded stream within a DVB-T2 signal. One T2-MI feed can carry several.
Watch out: If an expected service is missing from an extracted stream, check the PLP before the PID.
PLS Physical Layer Scrambling
Modulation & RF
A scrambling sequence, identified by a code and a mode (gold or root), needed alongside ISI to lock a multistream carrier.
Watch out: This is not conditional access — it protects nothing. And plsm takes a name: a numeric value is read as root mode, re-derives the code, and never locks.
PMT Program Map Table
Signalling
Per service. Lists the elementary streams that make up that service, their stream types and descriptors, and the PCR PID.
PSI Program Specific Information
Signalling
The MPEG-defined signalling tables: PAT, PMT, CAT and TSDT.
PTS / DTS Presentation / Decode Time Stamp
Container & packets
When a frame should be presented, and when it should be decoded. Carried in the PES header, paced against the PCR.
PUSI Payload Unit Start Indicator
Container & packets
A header bit meaning a PES packet or a section begins in this payload.
QEF Quasi-Error-Free
Modulation & RF
The quality target every DVB-S2 threshold is quoted at: under one uncorrected error-event per transmission hour for a 5 Mbit/s service, about PER < 10⁻⁷.
Watch out: DVB-S2X tables instead use FER = 10⁻⁵ — a different metric on a different object. Do not compare S2 and S2X figures at the third decimal.
QPSK / 8PSK / APSK
Modulation & RF
Phase- and amplitude-modulation constellations. DVB-S2 spans QPSK to 32APSK; S2X extends to 256APSK.
Watch out: Higher order is not simply less robust: 8PSK 3/5 beats QPSK 9/10 by 0,92 dB at the same throughput. 'Lower order is more robust' holds only at equal code rate.
RIST Reliable Internet Stream Transport
Delivery & IP
A standards-based alternative to SRT for the same problem.
Roll-off α
Modulation & RF
The excess bandwidth beyond the Nyquist minimum. Occupied bandwidth is Rs × (1 + α).
RTP / UDP / TCP
Delivery & IP
The transport layers a stream can ride on. RTP adds a sequence number, which detects loss the continuity counter cannot.
RTSP Real Time Streaming Protocol
Delivery & IP
The session control protocol SAT>IP uses to set up and tear down streams, typically on port 554.
SAT>IP
Delivery & IP
A protocol for delivering satellite tuner output over IP, letting clients tune a remote tuner by URL and receive the transport stream.
Scrambling
Conditional access
The standardised layer that encrypts packet payloads with a symmetric control word.
SCS SimulCrypt Synchronizer
Conditional access
The head-end orchestrator: obtains control words, feeds the ECMGs, synchronises ECMs to crypto periods and drives the scrambler.
SDT Service Description Table
Signalling
Carries service names, provider names, service types and running status.
Section
Container & packets
The wrapper used for signalling tables rather than media. Maximum 4096 bytes, with a CRC32 and a version number.
SI Service Information
Signalling
The DVB-defined signalling tables layered on top of PSI: NIT, SDT, BAT, EIT, TDT, TOT and others.
SimulCrypt
Conditional access
Scrambling content once with one control word and handing that word to several CA systems, each generating its own ECM stream.
Watch out: The cost is signalling bandwidth, not another copy of the video.
Spectral efficiency η
Modulation & RF
Bits carried per transmitted symbol, for a given MODCOD.
Watch out: Tabulated values assume no pilots and are normalised to symbol-rate bandwidth. Divide by (1+α) for efficiency per Hz of occupied spectrum.
SRT Secure Reliable Transport
Delivery & IP
A retransmission-based protocol for carrying streams reliably over lossy networks, with a configurable latency budget.
stream_type
Signalling
A byte in the PMT nominally identifying what an elementary stream contains.
Watch out: Frequently does not identify the codec. DVB audio is commonly signalled as 0x06 'private data' with the real codec named by a descriptor — read only the stream type and you may conclude a service has no audio.
Symbol rate Rs
Modulation & RF
Symbols per second on the carrier, in Msym/s or ksym/s. Useful bitrate is Rs × η.
T2-MI DVB-T2 Modulator Interface
Encapsulation
A DVB-T2 signal encapsulated inside a transport stream for delivery to a modulator — a transport stream inside a transport stream.
Watch out: Its payload_len field is expressed in bits, not bytes, and its 32-bit CRC covers header, payload and padding together.
table_id
Signalling
The byte identifying which table a section belongs to — 0x00 PAT, 0x01 CAT, 0x02 PMT, 0x42 SDT actual, and so on.
TDT / TOT Time and Date / Time Offset Table
Signalling
UTC time, and local offset plus daylight-saving information.
TEI Transport Error Indicator
Container & packets
A header bit set by the demodulator when forward error correction could not repair the packet.
Watch out: Set by demodulators, never by software that merely corrupts bytes. Payload corruption leaves this flag clear.
TR 101 290 ETSI TR 101 290
Tooling
The DVB measurement guidelines, defining the three priority levels of monitored errors.
TS packet
Container & packets
The unit of a transport stream: 188 bytes — a 4-byte header, an optional adaptation field, and up to 184 bytes of payload.
tsanalyze
Tooling
Produces a full analysis report for a stream: services, PIDs, bitrates, errors and scrambling.
Watch out: The first number to read is Unreferenced. Non-zero means PIDs carry data no PMT declares.
TSDuck
Tooling
An open-source transport stream toolkit: one pipeline command, tsp, plus about forty standalone utilities.
tsp
Tooling
The transport stream processor. One input plugin, a chain of packet-processing plugins, one output plugin — tsp -I … -P … -O ….
Watch out: Order matters, and plugin option names are not shared between plugins. tsp -P <plugin> --help is authoritative.
Unlocked tuner
Delivery & IP
A private tuner fixed to a satellite position but free to tune any transponder on it, in a cold state.
Watch out: Suited to scanning and EPG harvesting. Tuning takes time, and it carries no weather backup.
VCM / ACM Variable / Adaptive Coding and Modulation
Modulation & RF
Changing MODCOD per frame — by configuration, or in response to measured link conditions.
VL-SNR Very Low Signal-to-Noise Ratio
Modulation & RF
DVB-S2X modes using π/2 BPSK and very low code rates, reaching −9,9 dB Es/N0.
VVC Versatile Video Coding
Codecs
The successor to HEVC. Present in DVB specifications, with published test content rather than broad deployment.
Nothing matches. Try a shorter search, or clear the category filter.
How to use this
Everything is rendered on the page, so your browser's own find-in-page works and search engines can read every entry. The search box filters as you type across the term, its expansion and its definition. Category chips narrow by area, and ⚠️ Commonly confused shows only the entries with a caveat — a short list of the mistakes that cause the most wasted time in this field.
Every term links to the sheet that treats it properly. Nothing here is a substitute for the standard: where a definition matters to a design decision, the sheets cite the specification and this page points at them.
Related
- MPEG Transport Stream Explained — the container and its fields
- PSI/SI Tables & Descriptors — every table and descriptor tag
- DVB Standards & C/N Reference — the MODCOD tables and the three ratios
- Conditional Access & DVB SimulCrypt — scrambling against key distribution
- The TSDuck Cookbook — measuring all of it
- TS Packet Analyzer and DVB Bitrate Calculator