A Brief Delta Glossary

<< Click to Display Table of Contents >>

Navigation:  »No topics above this level«

A Brief Delta Glossary

Term

Context

Explanation

29.97

media

NTSC standard, the TV broadcast video framerate, originating from early colour TV transmission problems between chrominance and audio carrier signal phasing at 30 fps. Resolved through use of drop frame timecoding.

3D active

display

Active 3D separates left and right eye images by displaying them as alternate frames, with synchronised battery-operated shutter glasses to allow eyes also only to see alternately.

3D passive

display

In passive 3D, left and right eye images are separated by cross-polarisation of alternate pixel rows by the projectors, and glasses with polarising lenses in opposing axes. Effectively the eyes see alternate rows.

Art-Net

show creation

A UDP communications protocol for DMX512-A lighting control and for remote device management (RDM).

azimuth

projection

See heading.

blend

display

Overlapping projectors are used to create seamless continuous display. Edge blending adjusts the amount of overlap and consequent increased intensity of the overlapped display area. A single channel, mesh or textured image can also be blended to soften its edges. In Delta, blends can also be shaped and fully characterised.

canvas

display

The total area or display surface to be covered by projection media by a DeltaServer show.

carving

media

A means of reducing overall server load by cutting media frames down to just the area required per channel. Typically employed for large dome displays.

channel

display

The feed route, in or out, of media, or part of total media of a multi-channel system (audio channel, L / R / Rear / etc.; projection channel covering part of the canvas, or display panel area).

channel view

display

The section of a canvas ‘seen’ by a display or projection channel.

chroma key

show creation

Sets which colour will become transparent to layers below.

composition mode

display

The arrangement of compacted media frame elements on a canvas.

display

display

The total surface receiving a visual channel or arrangement of channels.

distortion: point

display

Distortion of a surface by the displacement of a node or nodes to affect an area of the surface.

distortion: surface

display

Smooth overall distortion of an image or channel around midlines or corners.

distortion: timeline

display

Bowing, skewing and stretching an image or channel.

dome mode

display

Projection of media onto a spherical or elliptical surface.

drop frame

media

In order to match video at 29.97 fps with real time clocks at 30 fps, this time code drops two frames every minute, on the minute, except every tenth minute. Drop frame timecode is written with a semi-colon HH:MM:SS;FF

EDID

display

Extended Display Identification Data. A metadata format describing properties and capabilities of a display device for communicating to a video source (graphics card), thus maximising compatibility without the need for manual configuration.

EDID emulation

display

Also called ‘spoofing’, the graphics card can read a proxy source rather than the actual display’s EDID. Delta Media Servers use software EDID emulation to maintain the required grouping arrangement on working displays should one (or more) display fail. If the display EDIDs are not emulated, and connection between server and a display is broken, then the display arrangement reverts to single display mode, causing media distortion across the working displays, or black output across multiple displays.

effect

show creation

Manipulation of an image or channel to change its appearance; any form from fading to Notch effects.

elevation

projection

See pitch.

enumerate

general

When Delta programs generate lists of servers, media &c.

eyepoint

display

The point from which a display is ideally viewed; the viewpoint from which media has been designed.

foot-lamberts (ftL)

projection

A measure of the amount of light reflected per square foot by a screen. SMPTE recommends 16 ftL as the level for a dark theatre. This would increase to maybe 60 ftL in situations of high ambient light.

frame rate

display

The rate at which a frame-based video sequence is meant to be played back, expressing frames per second (fps). For an audio track, the video playback rate to which it is synchronised in production. SMPTE LTC timecode tracks have standard frame rates.

In DeltaServer, media assets run on a timeline with its own defined framerate. For smooth playback, the Delta timeline frame rate should match or be a multiple of the display refresh rate (e.g. the timeline/content could be 25 fps, while the output refresh is 50 Hz). See also refresh rate.

frustum

projection

The pyramidal section representing the field of view of a projector or camera.

genlock

time & timing

The synchronisation of devices by linking them to a common timing signal.

group

system

A master-slave(s) relationship of two or more servers to synchronise their timing.

heading

projection

Angular displacement ‘west’ of ‘north’ (0-180° -ve) or ‘east’ of ‘north’ (0-180° +ve) where ‘north’ is straight ahead of the projector / observer. In movement, equivalent to yaw; in astronomy, azimuth.

house sync

time & timing

Method by which an signal generator produces the time reference (clock signal) for all genlocked servers in group, together with their channel outputs and devices. The signal may be a square-wave pulse or word clock for audio synchronisation.

interactive view

projection

In dome and mesh mode, moves the model around to enable the viewpoint to be changed in DeltaGUI and the playback window.

layer

show creation

Also sublayer: render priority of simultaneous media.

location

display

Co-ordinates of media on a canvas, relative to the top-left corner or centre.

LTC timecode

time & timing

LTC Timecode, or longitudinal timecode, is a SMPTE standard (see SMPTE 12M specification) for encoding a timecode on an analog audio waveform. It is called longitudinal, because it was originally recorded lengthwise alongside other audio/video tracks on audio tape or film. In the digital world, it is more often handled as a separate audio track element that would be played in sync with other audio/video tracks, or used as a positional reference signal sent out from one device to another via an audio output, and an interpreting input at one or more receivers. These receivers can then ‘chase’ the source. LTC timecode has a disadvantage in that it cannot be read in a static state, because the timecode is rolled out over time (longitudinally), so the audio signal must be ‘rolling’ for a receiver to interpret it, and receivers require some short amount of ‘pre-roll’ time before they lock to the signal.  The standardised timebases for LTC time are 23.98, 24, 25, 30 drop-frame, and 30 non-drop.

LTC chasing

time & timing

Synchronising playback to a reference LTC audio signal.

luma key

show creation

Sets which monochrome luminance value will become transparent to layers below.

lumen (lm)

projection

SI or ANSI unit of total amount of emitted visible light. Used as a measure of projector brightness. Higher brightness generally implies higher available contrast.

Lux (lx)

projection

The unit of luminance (1 lx = 1 lm/m2) but see screen gain.

master

system

The server assigned to determine the timeline activity of a group.

mesh

display

A polygon mesh is a 3D graphic surface contructed from faces joined by straight common edges. The end of an edge is a vertex, so a mesh can also be described as the set of vertices that define a polyhedral 3D surface.

mesh mode

display

The Delta display mode for mapping media onto a 3D surface based on a computer graphics object model of it.

MPCDI

display

Multiple Projection Common Data Interchange. A VESA standard data format for projection calibration systems to communicate with devices in a multi-display configuration to produce seamless displays. (Version 1, 2013; Version 2, 2015)

NDI®

comms

Network Device Interface developed by NewTek. A royalty-free IP standard for allowing multiple video streams on a shared connection. NDI supports high quality, low latency, frame-accurate video over standard Ethernet networks.

node

display

Any selectable intersection point on a geometric grid or mesh.

non-drop frame (NDF)

media

30 fps timecode video source played back at 29.97 fps. Note that being played more slowly this drifts from real time.

pitch

projection

Angular displacement above (0-180° +ve) or below (0-180° -ve) the horizon from the observer / projector. Also referred to as altitude or elevation.

preview

show review

Web-based view of the Delta playback window.

real time

show creation

Real time clocks (RTC) ‘tell the time’ rather than relative time displacement. DeltaRealTime is an application that enables gaming-style assets in real time to be integrated into timeline playback media.

refresh rate

display

Refresh rate is the number of times an output image is drawn, per second, whether in a digital projector, an LED display panel or a monitor display. Expressed as frequency, e.g. 60 Hz. See also frame rate.

reserve timeline

show creation

Delta can fade from the current playing timeline to a Reserve Timeline to enable fading back to a different position in the current timeline.

roll

projection

Angular displacement around the north (normal forward) axis, anticlockise (0-180° -ve), clockwise (0-180° +ve).

screen gain

projection

Ratio of projected light to screen-reflected light, usually in the same axis. As the viewing angle increases away from this axis, gain will decrease (the screen appears progressively less bright). A gain of 0.8 means 80% of the projected light is reflected back. A screen with a gain higher than 1 implies that the reflected light is focused to a narrower angle than the incident light (which also means a narrower viewing angle). The highest gain screens can cause hot spots and reflect colours unequally. Lower gain screens will reduce light scatter in a dome theatre, for example 0.55. For ‘screen brightness’:

lumens ÷ screen area × screen gain = ftL (see also foot-lamberts.)

slave

system

A server assigned to follow the playback activity of a master server.

SMPTE

 

Society of Motion Picture & Television Engineers: professional membership and standards-setting association (www.smpte.org)

spline

show creation

A linear path described by Bezier curves for a resource to move along.

tearing

time & timing

Display image discontinuity caused by display synchronisation problems.

timecode (SMPTE)

time & timing

An 80-bit data format in HH:MM:SS:FF (the range of frames FF being the number of frames per second).

timecode (generic)

time & timing

A coded signal which carries timecode positional information for coordination of devices. The most common formats of timecode signal are LTC and VITC.

timeline

show creation

A space in DeltaGUI measured in SMPTE timecode along which layers of media, effects and controls can be arranged to create a show or part of a show.

timing mode

time & timing

In Delta: display a Delta timeline in SMPTE, frames or seconds.

transition

show creation

Any time-spanned effect moving from one visual state to another, e.g. fade, transparency, morph

vertex

media

A point of intersection in a 3D graphical model where edges or polygonal faces meet.

vertex group

media

A group of linked vertices in a graphical model; can be one element in an .obj file.

VESA

 

Video Electronics Standards Association

viewport

display

The visible portion of a total image or canvas.

VITC Timecode

time & timing

VITC Timecode, or vertical interleave timecode, is a SMPTE standard for encoding a timecode signal into the vertical blanking interval of a video signal. VITC has a very similar payload definition to LTC, but has the advantage of being able to be read back even when the video is playing back very slow or stopped. Whilst often used in production, VITC is very uncommonly used for Pro AV device positional coordination today, because it requires embedding in a video signal versus a more easily processable audio waveform.

warp

display

Alter the geometry of a display channel or image, mainly to match flat media to a non-flat display surface.

WebRTC

show review

Web Real-Time Communication streams Delta playback over IP for viewing in a web browser.

word clock

time & timing

A digital audio signal designed for keeping digital audio devices in sync with a constant, precisely-timed bit-rate of 44.1 or 48 kHz.

zenith

projection

The point directly overhead of the projector / observer (pitch = 90°).

^ top of page