samples each of R-Y and B-Y, giving less chrominance (color) bandwidth in relation to luminance. This compares with 4:4:4 sampling where full same bandwidth is given to all three channels – in this case usually sampled as RGB. The term 4:2:2 originated from the ITU-R BT.601 digital video sampling where 4:2:2 sampling is the standard for digital studio equipment. The origin of the term is steeped in digital history and should strictly only be used to describe a specific format of standard definition digital television sampling. However, it is widely used to describe the sampling frequency ratios of image components (Y, B-Y, R-Y) of HD, film and other image formats. See also: 13.5 MHz, Co-sited sampling, Digital keying, ITU-R BT.601, ITU-R BT.709, Nyquist
4:2:2:4
This is the same as 4:2:2 but with the key signal (alpha channel) included as the fourth component, also sampled at 13.5 MHz (74.25 MHz at HD). See also: Dual link
A B C D E F G H I J
K L
M N O P Q R S T U V
W X Y Z
4:3 The aspect ratio of PAL and NTSC traditional television pictures, originally chosen to match 35mm film. All broadcast television pictures were 4:3 until the introduction of high definition when a wider image was considered to be more absorbing for viewers. For display tube manufacturers the most efficient aspect ratio would be 1:1 – square – as this is inherently the strongest, uses less glass and weighs less. 16:9 tubes are more expensive to produce. Such restraints do not apply to panels basic on LED, Plasma or SED technologies.
4:4:4 One of the ratios of sampling frequencies used to digitize the luminance and color difference components (Y, B-Y, R-Y) or, more usually, the RGB components of a video signal. In this ratio there is always an equal number of samples of all components. RGB 4:4:4 is commonly used in standard computer platform-based equipment, when scanning film or for high-end post including that used for cinematography. In the converged media world, big screen requirements for cinema demand a new high level of picture quality. Film is commonly scanned in RGB for digital intermediate and effects work, and recorded directly to disks. The signal is then kept in the RGB form all the way through the DI process to the film recorder – making the best use of the full RGB data. For the rapidly growing market of digital cinema exhibition the DCI has recommended X´Y´Z´chromaticity which can be derived from RGB using a 3D LUT. See also: 2K, X´Y´Z´, Digital intermediate, Dual link
4:4:4:4
As 4:4:4, except that the key signal (a.k.a. alpha channel) is included as a fourth component, also sampled at 13.5 MHz (74.25 MHz at HD). See also: Dual link
422P@ML See MPEG-2
4fsc A sampling rate locked to four times the frequency of color subcarrier (fsc). Its use is declining as all new digital equipment is based on component video where color subcarrier does not exist and sampling clock signals are derived from the line frequency. See also: Component video A 4K See Film formats
5.1 Audio See Discrete 5.1 Audio
50P and 60P These indicate a video format that has 50 or 60 progressive frames per second and usually refers to high definition. The original digital television standards only included progressive frame rates above 30 Hz for image sizes up to 720 lines – thus limiting the total video data. More recently this has been expanded up to 60 Hz for the larger 1080-line television standards to provide the best of the best – the maximum HD image size with a fast rate for rendition of fast action and progressive frames for optimum vertical resolution (better than interlaced scans). The baseband signal produces twice the data rates of the equivalent interlaced (50I and 60I) formats, pushing up equipment specifications. See also: SDI (3G SDI)
601
See ITU-R BT.601 709
See ITU-R BT.709 7.1
See Discrete 5.1 Audio
8 VSB/16 VSB See VSB AAC
Advanced Audio Coding, a codec originally known as MPEG-2 NBC (non-backwards compatible), is considered the successor to MP3, with about 25 percent efficiency improvement. However this performance has more recently been considerably enhanced with aacPlus, also known as High Efficiency AAC (HE-AAC), and included in MPEG-4 and delivers CD quality stereo at 48 kb/s and 5.1 surround sound at 128 kb/s. Websites: (AAC)
www.audiocoding.com, (aacPlus)
www.codingtechnologies.com
AAF
The Advanced Authoring Format – an industry initiative, launched in 1998, to create a file interchange standard for the easy sharing of media data and metadata among digital production tools and content creation applications, regardless of platform. It includes EBU/SMPTE metadata and management of pluggable effects and codecs. It allows open connections between equipment where video, audio and metadata, including information on how the content is composed, where it came from, etc., are transferred. It can fulfill the role of an all-embracing EDL or offer the basis for a media archive that any AAF-enabled system can use. In 2007 AAF Association, Inc. changed its name to Advanced Media Workflow Association (AMWA), with direction and focus on file-based workflows including AAF, MXF and other formats Website:
www.aafassociation.org
AB Axis (x, y, z)
Used to describe the three-dimensional axes set at right angles to each other, available in DVE manipulations. At normal x lies across the screen left to right, y up the screen bottom to top and z points into the screen. Depending on the power of the equipment and the complexity of the DVE move, several hierarchical sets of xyz axes may be in use at one time. For example, one set may be referred to the screen, another to the picture, a third offset to some point in space (reference axis) and a fourth global axis controlling any number of objects together. See also: DVE, Keyframe
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GLOSSARY OF TERMS
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