Video fundamentals / Reference
Audiovisual Systems Glossary
Live-visual systems combine vocabulary from video, audio, networking, graphics and show control. These short definitions describe how the terms are used in this portfolio; they are starting points, not substitutes for the current standard or manufacturer documentation.
Playback and image
- Codec
A method for encoding and decoding media. The codec is not the same as the file container or extension.
- Media server
A hardware and software system prepared to store, process, control and output visual media for a show or installation.
- Pixel
The smallest addressable picture element in a raster image or display. Pixel count alone does not describe physical size, brightness or perceived detail.
- Chroma sampling
The way a video signal represents color detail relative to brightness detail, commonly written as 4:4:4, 4:2:2 or 4:2:0.
- Bit depth
The number of discrete values available to represent a channel. Higher bit depth can preserve smoother gradients, but increases data and processing requirements.
Displays and signal paths
- EDID
Extended Display Identification Data. A display uses it to communicate supported formats and capabilities to a source.
- HDCP
High-bandwidth Digital Content Protection. Compatible devices authenticate before protected digital content is displayed.
- Projection mapping
The process of aligning visual content to the geometry of a physical surface rather than treating the output as one conventional rectangle.
- Edge blend
An overlapping and compensation process used to make adjacent projected images appear as one larger image.
- Canvas
The complete pixel space created for a composition, which may be divided among several outputs and physical surfaces.
Timing and synchronization
- Timecode
A positional address expressed as hours, minutes, seconds and frames. It tells a system where it is on a timeline.
- LTC
Linear Timecode. Timecode encoded as an audio-like signal and delivered to a compatible input.
- MTC
MIDI Timecode. Time information transmitted using MIDI messages.
- Genlock
Synchronization of a video device or output to an external timing reference.
- Frame lock
Hardware alignment of frame refresh across multiple display outputs or systems.
- Word clock
A reference used to align digital-audio sample timing between compatible devices.
Control
- MIDI
A protocol widely used to send notes, control changes, transport and other performance data between devices and applications.
- OSC
Open Sound Control. A network-oriented messaging format commonly used to control parameters in media and show systems.
- DMX
A control protocol associated with lighting and show devices. Supported functions depend on the receiving hardware or software.
- Cue
A defined action or group of actions executed at a particular show moment.