- Action safe
- The area inside a 3.5% margin on each side of the frame (93% of width and height under EBU R 95). Keep important action inside it. More →
- Alpha channel
- A fourth image channel that stores transparency. Transparent PNG lower thirds and WebM/ProRes 4444 overlays carry alpha so only the graphic shows over video.
- Aspect ratio
- Width divided by height. 16:9 is the HD/UHD standard, 9:16 is vertical social video, 4:3 is legacy SD. More →
- B-roll
- Supporting footage cut over a voice-over or interview, such as shots of a location or an object being discussed.
- Bitrate
- How much data per second a video or audio stream uses, usually in Mbps or kbps. Higher bitrate means better quality and bigger files. More →
- Browser source
- An OBS (and Streamlabs, vMix web input) source that renders a web page as a transparent layer. Used for tickers, lower thirds and alerts. More →
- Bug
- The small persistent logo in a corner of the screen, also called a DOG (digital on-screen graphic). Keep it inside title safe.
- CBR (constant bitrate)
- Encoding at a fixed bitrate. Live platforms such as YouTube recommend CBR for streaming because it keeps the connection load predictable.
- Chroma key
- Replacing a uniform coloured background (green or blue) with another image. The basis of every virtual set. More →
- Chroma subsampling
- Storing colour at lower resolution than brightness. 4:2:2 keeps more colour detail than 4:2:0, which gives cleaner key edges.
- Crawl
- Text that moves horizontally across the screen, usually at the bottom. Often called a ticker. More →
- Drop-frame timecode
- A timecode counting method for 29.97 fps video that skips frame numbers (not frames) so that the timecode stays in step with clock time. Written with a semicolon, e.g. 00:59:59;29.
- EBU R 95
- The European Broadcasting Union recommendation that defines action-safe (93%) and graphics-safe (90%) areas for 16:9 production. More →
- EBU R 128
- The European loudness recommendation for broadcast. It sets a programme loudness target of −23 LUFS.
- Frame rate
- Frames per second. 25/50 fps in most of Europe, 29.97/59.94 fps in North America and Japan. Match graphics and loops to the programme rate. More →
- Garbage matte
- A rough mask that removes everything outside the green screen (stands, lights, ceiling) before the keyer does the fine work.
- Genlock
- Synchronising cameras, LED processors and graphics to a common reference signal so frames line up and LED walls do not flicker on camera.
- GOP / keyframe interval
- The distance between full keyframes in a compressed stream. YouTube recommends a 2-second keyframe interval for live streams. More →
- IFB
- Interruptible foldback: the earpiece feed that lets a producer talk to a presenter over the programme audio.
- Interlaced
- Video in which each frame is split into two fields of alternating lines (the "i" in 1080i). Most streaming is progressive ("p").
- Key and fill
- A pair of signals from a graphics system: the fill carries the picture, the key carries its transparency. A vision mixer combines them over video.
- LED volume
- A stage surrounded by LED walls that display a real-time 3D environment behind the talent, instead of a green screen. More →
- Light wrap
- A compositing trick that lets a little background light spill onto the edges of a keyed presenter so they sit naturally in the scene.
- Lower third
- A graphic in the lower part of the frame that names the person speaking or the topic. Usually on screen for a few seconds. More →
- LUFS
- Loudness Units relative to Full Scale, the measurement used by loudness standards such as EBU R 128.
- Moiré
- A wavy interference pattern that appears when a camera sensor records a fine regular pattern, such as the pixels of an LED wall. More →
- Multiview
- A monitor that shows many sources (cameras, graphics, programme, preview) in a grid. Standard in control rooms and in software like vMix.
- NDI
- Network Device Interface, a protocol for sending low-latency video between devices and software over an ordinary IP network.
- Overscan
- The part of the picture that older TVs cropped off. The reason safe areas exist. More →
- Pixel pitch
- The distance between the centres of two LED pixels, in millimetres. Smaller pitch means higher resolution and closer possible camera distance. More →
- Progressive
- Video in which each frame is drawn in full (the "p" in 1080p). The default for streaming and modern production.
- Rec. 709
- The ITU colour standard for HD video. YouTube recommends Rec. 709 for SDR live streams.
- RTMP / RTMPS
- The protocol most platforms use to ingest live streams. RTMPS is the encrypted version.
- Rundown
- The running order of a show: every story, segment and graphic with its timing.
- Safe area
- Any of the guide rectangles (action safe, title safe) that keep important content away from the frame edges. More →
- SDI
- Serial Digital Interface, the coaxial cable standard used to carry uncompressed video in broadcast facilities.
- SOT
- Sound on tape: a clip of someone speaking, with their own audio, inside a news item.
- Spill
- Green (or blue) light reflected from the screen onto the presenter, which makes edges hard to key. More →
- SRT
- Secure Reliable Transport, an open-source protocol for sending live video over unpredictable internet connections.
- Stand-up
- A reporter speaking directly to camera on location, also called a piece to camera.
- Stinger transition
- A short animated graphic that covers the cut between two scenes. OBS supports stingers as video files with alpha.
- Tally light
- The red light on a camera that tells the presenter it is live on air.
- Teleprompter
- A device or app that scrolls the script in front of the camera lens so the presenter can read while looking into the lens. More →
- Ticker
- A band of scrolling text with headlines or data, usually at the bottom of the screen. Also called a crawl. More →
- Timecode
- A label for every frame in HH:MM:SS:FF form (hours, minutes, seconds, frames), standardised by SMPTE.
- Title safe
- The area inside a 5% margin on each side (90% of the frame under EBU R 95), where text and logos should sit. Also called graphics safe. More →
- Virtual set
- A computer-generated studio that replaces a green screen behind the presenter, either as a still, a loop or a tracked real-time 3D scene. More →
- Vision mixer
- The device or software (also called a switcher) that cuts between cameras and sources and adds keys and transitions.
- VO
- Voice-over: a presenter reading over pictures, without the reporter appearing on screen.
Reference
Broadcast glossary
49 terms from the control room, the green-screen studio and the streaming encoder, explained in a sentence or two, with links to the tool or guide where each one matters.