Ensemble Designs BrightEye 71 HD/SD 8 Channel Analog Audio Embedder/Disembedder - Manual (Page 25)

www.ensembledesigns.com BrightEye 71 and 71-F - Page 25
HD/SD 8 Channel Analog Audio Embedder/Disembedder User Guide TM BrightEye 71 and 71-F
Luminance
The “black & white” content of the image. Human vision has 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.
Multi-mode
Multi-mode optical fibers have a larger diameter core (either 50 or 62.5 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 bit rate of the
data stream. 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
two endpoint devices have any electrical connection to each other. This can be very advantageous
in large facilities where problems with ground loops appear. Secondly, and most importantly, an
optical interface can carry a signal for many kilometers or miles without any degradation or loss in the
recovered signal. Copper is barely useful at distances of just 1000 feet.
Oversampling
A technique to perform digital sampling at a multiple of the required sample rate. This has the
advantage of raising the Nyquist Rate (the maximum frequency which can be reproduced by a given
sample rate) much higher than the desired passband. This allows more easily realized anti-aliasing
filters.
PAL
During the early days of color television in North America, European broadcasters developed a
competing system called Phase Alternation by Line. This slightly more complex system is better able
to withstand the differential gain and phase errors that appear in amplifiers and transmission systems.
(Engineers at the BBC claim that it stands for Perfection At Last.)
Progressive
An image scanning technique which progresses through all of the lines in a frame in a single pass.
Computer monitors all use progressive displays. This contrasts to the interlace technique common to
television systems.