| AAC — Advanced Audio Coding |
Lossy audio compression standard used in MPEG-4. Widely used in HLS and OTT streams. Variants include HE-AAC v1 and v2 for low-bitrate applications. |
| AC-3 — Audio Codec 3 |
Dolby Digital compressed audio standard. Used in DVB, ATSC, and Blu-ray. |
| Acknowledgment |
Confirmation by an operator that an alarm event has been received, reviewed, and actioned. Acknowledged alarms remain in the log but are visually distinguished from unacknowledged ones. |
| AES3 |
Balanced digital audio interface standard (AES/EBU) used to carry PCM audio between professional broadcast equipment. |
| ARQ — Automatic Repeat reQuest |
Error correction method where the receiver requests retransmission of lost or corrupted packets. Used in SRT and some RTP profiles. |
| ASI — Asynchronous Serial Interface |
Physical coaxial interface for carrying DVB MPEG-2 Transport Streams at 270 Mbps. Common in broadcast playout and headend equipment. |
| Artifact |
Visible distortion in a video image resulting from encoding errors, transmission errors, or signal degradation. Examples: blockiness, ringing, mosquito noise. |
| AVC — Advanced Video Coding |
H.264 video compression standard (ITU-T H.264 / ISO/IEC 14496-10). Dominant codec for broadcast, OTT, and contribution. |
| BER — Bit Error Rate |
Ratio of incorrectly received bits to the total number of transmitted bits. A key RF and transmission quality indicator. |
| BISS — Basic Interoperable Scrambling System |
Simple CA system used for encrypting contribution and distribution feeds. Defined by EBU. |
| Black frame |
A video frame where all luma (Y) values are at or near minimum level. Indicates signal loss, encoder failure, or intentional fade-to-black. Detected by MultiProbe using the BlackLevel metric. |
| CA — Conditional Access |
System that controls subscriber access to encrypted broadcast content using ECM and EMM messages. |
| CAT — Conditional Access Table |
PSI table (PID 0x0001) listing the CA systems used in the transport stream and their associated EMM PIDs. |
| CBR — Constant Bit Rate |
Encoding mode where the output bitrate is fixed regardless of content complexity. Required for traditional broadcast transmission. |
| CDN — Content Delivery Network |
Distributed network of servers delivering OTT content to end users with low latency and high availability. |
| Continuity counter |
4-bit field in each TS packet header (values 0–15) that increments per PID. Gaps or repetitions indicate packet loss or insertion errors — a TR 101 290 Priority I check. |
| Control word |
Encryption key periodically delivered via ECM to authorized receivers for descrambling CA-protected content. Typically changes every 10 seconds. |
| CRC — Cyclic Redundancy Check |
Error detection code appended to MPEG-2 PSI/SI tables. A CRC error indicates table corruption or transmission error — a TR 101 290 Priority II check. |
| DASH — Dynamic Adaptive Streaming over HTTP |
OTT adaptive streaming standard (ISO/IEC 23009). The manifest file (MPD) describes available representations at different bitrates. |
| DCT — Discrete Cosine Transform |
Mathematical transform at the core of MPEG video compression. Converts spatial pixel blocks into frequency coefficients for quantization. |
| DF — Delay Factor |
MDI metric (RFC 4445) expressing the buffer depth in milliseconds required to absorb jitter and deliver continuous, loss-free playout. |
| DTS — Decoding Time Stamp |
PES header timestamp indicating when a decoder should begin decoding a packet, in units of 1/90000 seconds. |
| DVB — Digital Video Broadcasting |
Family of open ETSI standards for digital television transmission over satellite (DVB-S/S2), cable (DVB-C), and terrestrial (DVB-T/T2). |
| DVB-T2 |
Second-generation DVB terrestrial standard with higher capacity than DVB-T. Uses OFDM modulation, LDPC FEC, and supports multiple PLPs. |
| EAC-3 — Enhanced AC-3 |
Dolby Digital Plus — extended version of AC-3 with higher bitrate efficiency. Used in OTT and Blu-ray. |
| EBU — European Broadcasting Union |
Organization of public service broadcasters. Publishes technical standards including EBU R128 loudness recommendation. |
| ECM — Entitlement Control Message |
CA message embedded in the TS carrying the encrypted control word for content decryption. |
| EEWS — Extended Emergency Warning System |
Japanese broadcast emergency alert system, extension of EWS with additional regional targeting capability. |
| EIT — Event Information Table |
SI table (PID 0x0012) carrying EPG schedule data: program titles, times, and descriptions. |
| EMM — Entitlement Management Message |
CA message managing subscriber entitlements — activating, deactivating, or updating access rights for individual smart cards. |
| ES — Elementary Stream |
The raw encoded output of a single encoder: one video, audio, or data stream, before being packetized into PES and multiplexed into a TS. |
| EWS — Emergency Warning System |
Japanese broadcast emergency alert system. EWS/EEWS signals are carried in MPEG-2 TS and monitored by MultiProbe for presence and integrity. |
| FEC — Forward Error Correction |
Redundancy data added to a transmission so the receiver can detect and correct errors without retransmission. Used in DVB (LDPC) and IP protocols (SMPTE 2022). |
| Frozen frame |
Condition where consecutive video frames are identical or near-identical, indicating encoder freeze or signal loss upstream. Detected by MultiProbe using the FrozenLevel metric. |
| GOP — Group of Pictures |
Sequence of video frames between two consecutive I-frames. Defines the random access interval and affects compression efficiency and latency. Typical broadcast GOP: 12–25 frames. |
| HDR — High Dynamic Range |
Video format with extended luminance range and wider color gamut. Standards include HDR10, HLG, and Dolby Vision. |
| HEVC — High Efficiency Video Coding |
H.265 video compression standard (ITU-T H.265 / ISO/IEC 23008-2). Approximately twice the compression efficiency of AVC at equivalent quality. |
| HLS — HTTP Live Streaming |
Apple's adaptive OTT streaming protocol (RFC 8216). Uses M3U8 playlists and segmented media files. Dominant protocol for live and VOD OTT delivery. |
| I-frame — Intra-coded frame |
A video frame encoded entirely without reference to any other frame. Acts as a random access point. Also called an IDR frame in H.264/HEVC. |
| Inset / Local inset |
Temporary substitution of broadcast content (e.g. a program or advertisement) with alternative local content, triggered by a splice command (SCTE-35/104) embedded in the signal. |
| IPTV — Internet Protocol Television |
Delivery of television content over managed IP networks, as opposed to OTT which uses the public internet. |
| IRD — Integrated Receiver Decoder |
Device that receives, demodulates, decodes, and outputs digital broadcast signals. Used in professional headends and consumer set-top boxes. |
| ITU-R BS.1770 |
ITU recommendation defining the algorithm for measuring programme loudness and true-peak audio level. Basis for EBU R128. |
| Jitter |
Variation in packet inter-arrival times, or variation in the interval between consecutive PCR timestamps. Excessive jitter requires larger playout buffers and can cause decoder instability. |
| LKFS — Loudness K-weighted relative to Full Scale |
Loudness unit defined in ITU-R BS.1770. Numerically equivalent to LUFS. Used to express integrated programme loudness. |
| Loudness |
Perceptual measure of audio signal strength expressed in LUFS or LKFS. Measured as integrated (I), short-term (S), and momentary (M) per ITU-R BS.1770. |
| LU — Loudness Unit |
Unit equal to 1 dB in loudness measurements. Used to express the difference between a measured loudness and a target level. |
| LUFS — Loudness Units relative to Full Scale |
Loudness measurement unit equivalent to LKFS. EBU R128 broadcast target: −23 LUFS integrated. |
| MDI — Media Delivery Index |
RFC 4445 standard defining two metrics for IP media stream quality: Delay Factor (DF) and Media Loss Rate (MLR). |
| MLR — Media Loss Rate |
MDI metric expressing the rate of media packet loss as a fraction of the nominal bitrate. Any non-zero value indicates packet loss in the IP network. |
| MPEG-2 |
MPEG systems and video compression standard (ISO/IEC 13818). Basis of DVB transport streams. Video codec also known as H.262. |
| MPTS — Multi-Program Transport Stream |
An MPEG-2 TS carrying multiple services within a single bitstream. Typical for DVB broadcast multiplexes. |
| NAL — Network Abstraction Layer |
Packetization layer in H.264 and HEVC wrapping encoded video data into NAL units for transport or storage. |
| NDI — Network Device Interface |
NewTek/Vizrt protocol for transmitting uncompressed or lightly compressed video and audio over standard LAN at low latency. |
| NIT — Network Information Table |
DVB SI table (PID 0x0010) describing physical delivery system parameters: frequency, modulation, FEC rates. |
| NTP — Network Time Protocol |
UDP-based protocol (RFC 5905) for synchronizing clocks across IP networks. Used by MultiProbe nodes for timestamp accuracy. |
| Null packet |
TS packet with PID 0x1FFF and no meaningful payload. Used to pad a CBR transport stream to its nominal bitrate. |
| OTT — Over-The-Top |
Delivery of video and audio content over the public internet, bypassing traditional broadcast and cable distribution infrastructure. |
| PAT — Program Association Table |
Mandatory PSI table at PID 0x0000 mapping program numbers to PMT PIDs. Its absence triggers a Priority I TR 101 290 error. |
| PCR — Program Clock Reference |
42-bit timestamp embedded in the MPEG-2 TS adaptation field. Used by decoders to recover the encoder's 27 MHz system clock. PCR accuracy, jitter, and discontinuities are Priority I/II TR 101 290 checks. |
| PCR accuracy |
Deviation of PCR timestamp values from the ideal 27 MHz encoder clock. Maximum allowed deviation per ITU-T H.222.0: ±500 ns. |
| PCR discontinuity |
Abrupt non-sequential change in PCR values not signaled by the discontinuity indicator flag. Indicates a splice error or stream assembly problem. |
| PCR jitter |
Variation in the interval between consecutive PCR timestamps. Caused by network jitter in IP-based TS delivery or muxer timing instability. |
| PES — Packetized Elementary Stream |
An ES wrapped with a header containing PTS and/or DTS timestamps. PES packets are split into 188-byte TS packets for transport. |
| PID — Packet Identifier |
13-bit field (0x0000–0x1FFF) in the TS packet header identifying the logical stream to which the packet belongs. |
| PLP — Physical Layer Pipe |
In DVB-T2 and DVB-S2X, an independently coded data pipe within a single RF channel, allowing different services to use different modulation and code rates. |
| PMT — Program Map Table |
PSI table listing the PID assignments for all components of a service: video, audio, PCR, and data. |
| PSI — Program Specific Information |
The mandatory set of MPEG-2 TS tables required for demultiplexing: PAT, PMT, CAT, and TSDT. |
| PTS — Presentation Time Stamp |
33-bit timestamp in the PES header indicating when a decoded audio or video frame should be presented, in units of 1/90000 seconds. |
| QoE — Quality of Experience |
Perceptual measure of end-to-end service quality from the viewer's perspective. Encompasses video quality (artifacts, black, freeze), audio quality (silence, loudness), and availability. |
| QoS — Quality of Service |
Network-level performance metric encompassing bandwidth, latency, jitter, and packet loss. |
| RTMP — Real-Time Messaging Protocol |
Adobe streaming protocol for low-latency live video ingest to media servers. Widely used for contribution from encoders to CDN origins. |
| RTP — Real-time Transport Protocol |
IETF standard (RFC 3550) for real-time delivery of audio and video over IP using UDP. |
| RTSP — Real Time Streaming Protocol |
IETF standard (RFC 7826) for controlling real-time media streams. Acts as a network remote control for media servers. |
| Scrambling |
Encryption of TS packet payloads using a CA system. Scrambled packets require the correct control word for decoding. |
| SCTE-35 |
Standard defining the digital cueing message format for program insertion signaling in MPEG-2 TS. Used for ad insertion, blackout control, and content replacement. |
| SCTE-104 |
Standard defining the interface between automation systems and compression systems for splice signal injection. The studio-side counterpart to SCTE-35. |
| SDI — Serial Digital Interface |
SMPTE family of standards for uncompressed digital video over 75-ohm coaxial cable. Variants: SD-SDI (270 Mbps), HD-SDI (1.485 Gbps), 3G-SDI (2.97 Gbps), 12G-SDI (11.88 Gbps). |
| SDT — Service Description Table |
DVB SI table (PID 0x0011) carrying service names, provider names, and service type descriptors. |
| SI — Service Information |
DVB extension to MPEG-2 PSI providing additional tables: NIT, SDT, EIT, BAT, TDT, TOT. Required for EPG, frequency planning, and regional services. |
| Silence |
Audio condition where the signal level falls below a defined threshold for a defined duration. Indicates audio loss, mute insertion, or encoder failure. |
| SLA — Service Level Agreement |
Contractual commitment defining minimum acceptable service availability and quality. |
| SPTS — Single-Program Transport Stream |
An MPEG-2 TS carrying exactly one service. Common in contribution, distribution, and OTT origin packaging. |
| SRT — Secure Reliable Transport |
Open-source low-latency streaming protocol by Haivision. Combines ARQ error correction with AES encryption. |
| SSIM — Structural Similarity Index Measure |
Perceptual video quality metric comparing structural information between a reference and a degraded image. Range 0–1; higher is better. |
| ST 2110 — SMPTE ST 2110 |
Suite of SMPTE standards for professional uncompressed media (video, audio, ancillary data) over managed IP networks using RTP/UDP. Replaces SDI in IP-native broadcast facilities. |
| ST 2110-20 |
SMPTE ST 2110 Part 20 — Uncompressed Active Video. Defines RTP packetization for uncompressed video streams. |
| ST 2110-30 |
SMPTE ST 2110 Part 30 — PCM Digital Audio. Defines RTP packetization for uncompressed audio channels. |
| ST 2110-40 |
SMPTE ST 2110 Part 40 — Ancillary Data. Carries VANC/HANC data including closed captions, timecode, and tally. |
| Stuffing bitrate |
The portion of a CBR transport stream occupied by null packets (PID 0x1FFF), used to maintain a constant total bitrate. |
| Studio signal |
An uncompressed audio or video signal as used within a broadcast facility, such as SDI or SMPTE ST 2110. |
| Splice point |
A designated location in a video stream where content can be seamlessly replaced, signaled by SCTE-35 or SCTE-104 messages. |
| T2-MI — T2 Modulator Interface |
Interface standard for feeding DVB-T2 modulator input over IP or ASI. Encapsulates T2 frames including multiple PLPs in an MPEG-2 TS wrapper. |
| Tally |
Signal or visual indicator showing which camera or source is currently on-air. In MultiProbe, used as a label associated with a monitoring object. |
| TDT — Time and Date Table |
DVB SI table carrying the current UTC time, used by receivers for clock synchronization. |
| TOT — Time Offset Table |
DVB SI table carrying UTC time plus local time offset and DST information. |
| TR 101 290 — ETSI TR 101 290 |
ETSI measurement guideline defining error checks for DVB transport streams in three priority levels: Priority I (critical — causes service loss), Priority II (quality impairments), Priority III (informational). Primary reference for TS quality monitoring. |
| True peak |
Maximum instantaneous audio signal level including inter-sample peaks. Must not exceed −1 dBTP for broadcast distribution per EBU R128. |
| TSDT — Transport Stream Description Table |
PSI table (PID 0x0002) carrying TS-level descriptors such as scrambling system information. |
| TTFB — Time to First Byte |
Latency between sending an HTTP request and receiving the first byte of the response. A key OTT delivery quality indicator. |
| UDP — User Datagram Protocol |
Lightweight connectionless IP transport protocol. Used for multicast and unicast TS-over-IP delivery. Provides no error correction — packet loss is permanent. |
| UHD — Ultra High Definition |
Video resolution of 3840×2160 (4K) or 7680×4320 (8K) as defined by ITU-R BT.2020. |
| VBR — Variable Bit Rate |
Encoding mode where bitrate varies with content complexity. More efficient than CBR but requires buffering for fixed-capacity channels. |
| VMAF — Video Multimethod Assessment Fusion |
Perceptual video quality metric developed by Netflix. Combines multiple quality metrics into a single score (0–100) using a machine learning model. |
| VoD — Video on Demand |
Content delivery model where viewers select and watch content at any time, as opposed to linear broadcast. |