BrightEye 90-A HD Up/Down/Cross Converter and ARC with Analog Audio
BrightEye 90-A - Page 36
IEC
The International Electrotechnical Commission provides a wide range of
worldwide standards. They have provided standardization of the AC power
connection to products by means of an IEC line cord. The connection point uses
three flat contact blades in a triangular arrangement, set in a rectangular
connector. The IEC specification does not dictate line voltage or frequency.
Therefore, the user must take care to verify that a device either has a universal
input (capable of 90 to 230 volts, either 50 or 60 Hz), or that a line voltage switch,
if present, is set correctly.
Interlace
Human vision can be fooled to see motion by presenting a series of images, each
with a small change relative to the previous image. In order to eliminate the
flicker, our eyes need to see more than 30 images per second. This is
accomplished in television systems by dividing the lines that make up each video
frame (which run at 25 or 30 frames per second) into two fields. All of the odd-
numbered lines are transmitted in the first field, the even-numbered lines are in
the second field. In this way, the repetition rate is 50 or 60 Hz, without using
more bandwidth. This trick has worked well for years, but it introduces other
temporal artifacts. Motion pictures use a slightly different technique to raise the
repetition rate from the original 24 frames that make up each second of film—
they just project each one twice.
IRE
Video level is measured on the IRE scale, where 0 IRE is black, and 100 IRE is
full white. The actual voltages that these levels correspond to can vary between
formats.
ITU-R 601
This is the principal standard for standard definition component digital video. It
defines the luminance and color difference coding system that is also referred to
as 4:2:2. The standard applies to both PAL and NTSC derived signals. They both
will result in an image that contains 720 pixels horizontally, with 486 vertical
pixels in NTSC, and 576 vertically in PAL. Both systems use a sample clock rate
of 27 Mhz, and are serialized at 270 Mb/s.
Jitter
Serial digital signals (either video or audio) are subject to the effects of jitter. This
refers to the instantaneous error that can occur from one bit to the next in the
exact position of each digital transition. Although the signal may be at the correct
frequency on average, in the interim it varies. Some bits come slightly early,
others come slightly late. The measurement of this jitter is given either as the
amount of time uncertainty or as the fraction of a bit width. For 270 Mb/s SD
video, the 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.
