AAC (Advanced Audio Coding) — An audio coding standard considered the current state-of-the-art in general audio coding and the natural successor to MP3. AAC is part of the MPEG-4 multimedia standard, which uses MP4 as the container format.
Adaptive Streaming — A technology designed to provide the highest available quality for each specific user. Adaptive streaming technologies are almost exclusively based on HTTP and designed to work efficiently over large distributed HTTP networks such as the Internet. They work by detecting a user's bandwidth and CPU capacity in real time and adjusting the quality of the media stream accordingly.
API — An application programming interface.
AVC/H.264 — A widely adopted video coding standard that emerged as the result of joint development by the International Telecommunication Union Video Coding Experts Group (ITU-T VCEG) and ISO MPEG. This standard is known as H.264 (ITU-T name), MPEG-4 Part 10 (ISO/IEC 14496-10), or MPEG-4 Advanced Video Coding (AVC).
AVI (Audio/Video Interleaved) — A file format standard developed by Microsoft in which audio and video data are interleaved (alternated) with each other. During playback, the soundtrack is synchronized with the video.
Bandwidth — The range of frequencies within a band, or the data transfer capacity of a network connection, typically measured in bits per second.
Birate — The rate of video/audio data transfer, measured in kilobits per second (kbps). The higher the bitrate, the more disk space is occupied and typically the better the quality.
CAVLC, CABAC — Context-Adaptive Variable Length Coding (CAVLC) and Context-Adaptive Binary Arithmetic Coding (CABAC) are two methods for entropy coding of the bitstream syntax (macroblock type, motion vectors, reference index, etc.). CAVLC is the default compression method in AVC/H.264. CABAC is a more powerful compression method that can reduce the bit rate by an additional 10-15% (especially at high bit rates). Both methods provide lossless compression and therefore do not harm quality; however, using CABAC slows down both encoding and decoding processes.
CDN (content delivery network, or content distribution network) — A geographically distributed network of proxy servers and their data centers. The goal is to provide high availability and performance by distributing the service spatially relative to end-users.
Closed Captions — Textual video overlays that are not normally visible, as opposed to open captions, which are a permanent part of the picture. Captions are usually a textual representation of the spoken audio. In the United States, the official NTSC Closed Caption standard requires that all TVs larger than 13 inches include circuitry to decode and display caption information stored on line 21 of the video signal. DVD-Video can provide closed caption data, but the subpicture format is preferred for its versatility.
Codec — a Coder/decoder or compression/decompression software or hardware module. Codecs are used to encode and decode (or compress and decompress) various types of data that would otherwise use up a huge amount of disk space, such as raw sound and video files. Codecs can be used with either streaming (live media data) or file-based (AVI, WAV, MP4, etc.) content.
CPU (central processing unit) — An electronic circuitry within a computer that executes instructions that make up a computer program. The CPU performs basic arithmetic, logic, controlling, and input/output operations specified by the instructions in the program.
Deinterlace — The process of converting an interlaced video stream into a progressive one.
Demultiplexing — The opposite of multiplexing. In this process, a combined audio/video stream is separated into its component streams.
DirectShow® — Microsoft® DirectShow® is an architecture for streaming media on the Microsoft Windows® platform.
DirectX — Microsoft® DirectX® is a set of low-level application programming interfaces (APIs) for creating games and other high-performance multimedia applications. It includes support for two-dimensional (2-D) and three-dimensional (3-D) graphics, sound effects and music, input devices, and networked applications such as multiplayer games.
DTV (Digital Television) — A television technology that can carry more channels than analog TV in the same bandwidth and to receive high-definition TV programs.
Digital Video Broadcasting (DVB) — A set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium.
DXVA — Microsoft DirectX Video Acceleration. DXVA is a specification for hardware acceleration of digital video decoding processing.
Elementary stream (ES) — A single video or audio stream without container. For instance a basic MPEG-2 video stream (M2V or MPV) is an MPEG-2 ES, and on the audio side we have AC3, MP2, etc. Most DVD authoring programs require an ES as input.
GOP — Group Of Pictures in MPEG streams.
GPU (graphics processing unit) — A specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. Modern GPUs are very efficient at manipulating computer graphics and image processing. Their highly parallel structure makes them more efficient than general-purpose central processing units (CPUs) for algorithms that process large blocks of data in parallel.
HASP key (software protection dongle) — An electronic copy protection and content protection device. When connected to a computer or other electronics, they unlock software functionality or decode the content.
HDTV (High-Definition Television) — A type of digital television broadcasting format that provides much better resolution than televisions based on the NTSC standard. It transmits widescreen pictures with more detail and quality than those found in standard analog television, or other digital television formats. HDTV is considered to be the highest quality DTV format available.
HEVC/H.265 (High Efficiency Video Coding) — A video compression standard designed as part of the MPEG-H project as a successor to the widely used Advanced Video Coding (AVC, H.264, or MPEG-4 Part 10). In comparison to AVC, HEVC offers from 25% to 50% better data compression at the same level of video quality or substantially improved video quality at the same bit rate. It supports resolutions up to 8192×4320, including 8K UHD, and unlike the primarily 8-bit AVC, HEVC's higher fidelity Main10 profile has been incorporated into nearly all supporting hardware.
HLS (HTTP Live Streaming) — An HTTP-based adaptive bitrate streaming communications protocol developed by Apple Inc. and released in 2009. Support for the protocol is widespread in media players, web browsers, mobile devices, and streaming media servers.
Inter prediction — The process of predicting blocks of pixels based on temporal dependency between two or more frames. Also referred to as Temporal prediction.
Interlaced — A video storage mode. An interlaced video stream does not contain frames (pictures as we know them) but fields with each field containing half of the lines of one frame (all even or all odd lines).
Intra prediction — The process of predicting blocks of pixels based on spatial dependency (i.e. within the frame). Also referred to as Spatial prediction.
IPTV (Internet Protocol television) — The delivery of television content over IP networks. This contrasts with delivery through traditional terrestrial, satellite, and cable television formats. IPTV offers the ability to stream the source media continuously. As a result, a client media player can begin playing the content (such as a TV channel) almost immediately. IPTV is widely deployed in subscriber-based telecommunications networks with high-speed access channels into end-user premises via set-top boxes or other customer-premises equipment.
ISO (International Organization for Standardization) — An independent, non-governmental international organization that develops standards. ISO also provides publicly available MPEG standard documents, reference software, and conformance streams.
Latency — The time difference between when a particular video frame is captured by a device (camera, playout, encoder, etc.) and when this frame is played on an end user's screen.
Macroblock — A processing unit in image and video compression formats based on linear block transforms, typically the discrete cosine transform (DCT). Formats that are based on macroblocks include JPEG (where they are called MCU blocks), H.261, MPEG-1 Part 2, H.262/MPEG-2 Part 2, H.263, MPEG-4 Part 2, and H.264/MPEG-4 AVC. In H.265/HEVC, the macroblock as a basic processing unit has been replaced by the coding tree unit.
Middleware — Software that connects two or more software applications, so they can be compatible with each other and then exchange data.
Motion estimation — The process of estimating motion vectors during the encoding process.
MP3 (formally MPEG Audio Layer III) — A coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the US and elsewhere.
MP4 — A file format designed for storing MPEG-4 data.
MPEG (The Moving Picture Experts Group) — A working group of ISO/IEC in charge of the development of international standards for compression, decompression, processing, and coded representation of moving pictures, audio and their combination.
MPEG-1 — An audio and video compression format developed by Moving Pictures Expert Group. Official description: Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s.
MPEG-2 — Audio and video compression format developed by ISO/IEC/JTC/SC29/WG11, also known as ISO/IEC 13818. The MPEG-2 video coding standard is primarily aimed at coding of CCIR-601 or higher resolution video with fairly high quality at challenging bitrates of 4 to 9 Mbit/s. It aims at providing CCIR/ITU-R quality for NTSC, PAL, and SECAM, while also supporting HDTV quality, at data rates above 10 Mbit/s, real-time transmission, and progressive and interlaced scan sources.
MPEG-4 SP/ASP (Simple profile/Advanced simple profile) — A standard for graphics and video compression that is based on MPEG-1 and MPEG-2 and Apple QuickTime technology. Wavelet-based MPEG-4 files are smaller than JPEG or QuickTime files, so they are designed to transmit video and images over a narrower bandwidth and can mix video with text, graphics and 2-D and 3-D animation layers. MPEG-4 was standardized in October 1998 in the ISO/IEC document 14496.
MPEG-DASH — An adaptive bitrate streaming technique that enables high quality streaming of media content over the Internet delivered from conventional HTTP web servers. Similar to Apple's HLS solution, MPEG-DASH works by breaking the content into a sequence of small segments, which are served over HTTP. Each segment contains a short interval of playback time of content that is potentially many hours in duration, such as a movie or the live broadcast of a sports event. The content is made available at a variety of different bit rates.
MPTS (multi-program transport stream) — A type of transport stream containing more than one program. MPTS has become widely used in DVB and ATSC broadcast systems. Typically, MPTS has a constant bitrate with a fixed value and is aimed at the transmission of a group of programs (multiplex) using one frequency of terrestrial, cable, or satellite broadcasting.
Multiplexing — The process of combining multiple signals into one signal, over a shared medium.
OTT (over-the-top) — A streaming media service offered directly to viewers via the Internet. OTT bypasses cable, broadcast, and satellite television platforms, the companies that traditionally act as a controller or distributor of such content.
PAL (Phase Alternating Line) — The dominant television standard in Europe. The United States uses a different standard, NTSC. Whereas NTSC delivers 525 lines of resolution at 60 half-frames per second, PAL delivers 625 lines at 50 half-frames per second. Many video adapters that enable computer monitors to be used as television screens support both NTSC and PAL signals.
PES (Packetized Elementary Stream) — A continuous sequence of PES packets of one elementary stream with one stream ID. When PES packets are used to form a PES stream, they shall include Elementary Stream Clock Reference (ESCR) fields and Elementary Stream Rate (ES Rate) fields.
Program stream — A format similar to MPEG-1 Systems Multiplex. It results from combining one or more Packetized Elementary Streams (PES), which have a common time base, into a single stream. The Program Stream is designed for use in relatively error-free environments and is suitable for applications that may involve software processing. Program stream packets may be of variable and relatively great length. The MPEG-2 Program Stream is defined in the (ISO/IEC 13818-1).
PSNR (peak signal-to-noise ratio) — The ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation. Because many signals have a very wide dynamic range, PSNR is usually expressed as a logarithmic quantity using the decibel scale.
Quality of service (QoS) — The description or measurement of the overall performance of a service. To quantitatively measure the quality of service, several related aspects of the network service are often considered, such as packet loss, delay, jitter, etc.
Quality of Experience (QoE) — A measure of the delight or annoyance of a customer's experiences with a service.
Quick Sync Video — Intel's brand for its dedicated video encoding and decoding hardware core.
Redundancy — An automatic switch to the redundant source or server in case of errors.
RTMP (Real-Time Messaging Protocol) — A protocol originally developed by Macromedia (now Adobe) for real-time streaming of video, audio, and data between a server and Flash player. Today, RTMP is used to deliver content from an encoder to an online video host. While once proprietary, RTMP is now an open specification.
RTP — An Internet-standard protocol for the transport of real-time data, including audio and video. It can be used for media-on-demand as well as interactive services such as Internet telephony. RTP consists of data and a control part. The latter is called RTCP.
RTSP — A network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between endpoints.
RTT (Round Trip Time) — The amount of time it takes for a signal to be sent plus the amount of time it takes for an acknowledgement of that signal to be received. This time delay includes the propagation times for the paths between the two communication endpoints.
SCTE (Society of Cable Telecommunications Engineers) — An organization that develops training for cable television installers and engineers; in this role, it is analogous to the Society of Broadcast Engineers for broadcast television. SCTE is also an ANSI-recognized standards-developing organization for the cable industry.
SDK — Software development kit.
Set-Top-Box (STB) — A device that connects to a television and some external source of signal, and turns the signal into content then displayed on the screen.
SoC (System on a Chip) — An integrated circuit that integrates all or most components of a computer or other electronic system. These components almost always include a central processing unit (CPU), memory, input/output ports and secondary storage, often alongside other components such as radio modems and a GPU — all on a single substrate or microchip.
SPTS (single program transport stream) — A type of transport stream containing only one program. It has become widely used for broadcasting channels in IPTV networks and over the Internet. Typically, SPTS has a variable bitrate to save traffic (by removing padding) and improve picture quality. Each MPTS/SPTS transport stream includes video streams, audio streams, and additional user and service metadata such as teletext, subtitles, program listings or guides, etc.
SRT (Secure Reliable Transport) — A protocol developed by Haivision in 2012. The protocol operates on the basis of UDT (UDP-based Data Transfer Protocol) and ARQ packet recovery technology. It supports AES-128 and AES-256 encryption. In addition to listener (server) mode, it supports caller (client) and rendezvous (when both sides initiate a connection) modes, which allows connections to be established through firewalls and NAT.
Subpicture — Graphic bitmap overlays used in DVD-Video to create subtitles, captions, karaoke lyrics, menu highlighting effects, and so on.
Transport stream — The Transport Stream combines one or more Packetized Elementary Streams (PES) with one or more independent time bases into a single stream. Elementary streams sharing a common timebase form a program. The Transport Stream is designed for use in environments where errors are likely, such as storage or transmission in lossy or noisy media. Transport stream packets are 188 bytes long. The MPEG-2 transport stream is defined in the ISO/IEC standard (13818-1).
VOD (Video on Demand) — A system that allows users to select and watch video content over a network as part of an interactive television system. VoD systems either “stream” content, allowing viewing while the video is being downloaded, or “download” it in which the program is brought in its entirety to a set-top box before viewing starts.
YUV — A color encoding system used in video. YUV formats fall into two distinct groups, the packed formats where Y, U (Cb) and V (Cr) samples are packed together into macropixels which are stored in a single array, and the planar formats where each component is stored as a separate array, the final image being a fusing of the three separate planes.