Ensemble Designs 9670 Audio Automatic Gain and Loudness Control and 9690 Audio Compliance and Monitoring Software - Manual (Page 28)

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Avenue 9670 - page 28
LevelTrack™ Audio Loudness Control AGC Software Option
allowable jitter is 740 picoseconds, or 0.2 UI (Unit Interval – one bit width). For 1.485 Gb/s HD, the
same 0.2UI spec corresponds to just 135 pico seconds.
Luminance
The “black & white” content of the image. Human vision had more acuity in luminance, so television
systems generally devote more bandwidth to the luminance content. In component systems, the
luminance is referred to as Y.
MPEG
The Moving Picture Experts Group is an industry group that develops standards for the compression
of moving pictures for television. Their work is an on-going effort. The understanding of image
processing and information theory is constantly expanding. And the raw bandwidth of both the
hardware and software used for this work is ever increasing. Accordingly, the compression methods
available today are far superior to the algorithms that originally made the real-time compression and
decompression of television possible. Today, there are many variations of these techniques, and the
term MPEG has to some extent become a broad generic label.
Metadata
This word comes from the Greek, meta means ‘beyond’ or ‘after’. When used as a prefix to ‘data’, it can
be thought of as ‘data about the data’. In other words, the metadata in a data stream tells you about
that data – but it is not the data itself. In the television industry, this word is sometimes used correctly
when, for example, we label as metadata the timecode which accompanies a video signal. That
timecode tells you something about the video, i.e. when it was shot, but the timecode in and of itself
is of no interest. But in our industry’s usual slovenly way in matters linguistic, the term metadata has
also come to be used to describe data that is associated with the primary video in a datastream. So
embedded audio will (incorrectly) be called metadata when it tells us nothing at all about the pictures.
Multi-mode
Multi-mode fibers have a larger diameter core than single mode fibers (either 50 or 62.5 microns
compared to 9 microns), and a correspondingly larger aperture. It is much easier to couple light energy
into a multi-mode fiber, but internal reflections will cause multiple “modes” of the signal to propagate
down the fiber. This will degrade the ability of the fiber to be used over long distances.
See also Single Mode.
NTSC
The color television encoding system used in North America was originally defined by the National
Television Standards Committee. This American standard has also been adopted by Canada, Mexico,
Japan, Korea, and Taiwan. (This standard is referred to disparagingly as Never Twice Same Color.)
Optical
An optical interface between two devices carries data by modulating a light source. This light source
is typically a laser or laser diode (similar to an LED) which is turned on and off at the bitrate of the
datastream. The light is carried from one device to another through a glass fiber. The fiber’s core acts
as a waveguide or lightpipe to carry the light energy from one end to another. Optical transmission
has two very significant advantages over metallic copper cables. Firstly, it does not require that the