Honeywell HDVR, Справочное руководство, Страница: 220 / 238

Rev 1.00 202 Document 900.0261
04/05
Video Formats and Digital Video
The NTSC definition of video black is not standardized. In North America it is defined as 7.5
IRE units and anything below that level is considered black. In Japan video black is defined
as 0 IRE. An IRE unit is 1% of the voltage difference from black to white. Thus 100 IRE is
completely white and 0 IRE is completely black.
NTSC features:
• 525 horizontal lines per frame, 485 of which form the picture
• 30 frames per second (fps)
PAL
PAL (Phase Alternate Line) was developed in Germany and is used in many parts of the
world that use an alternating current of 50 Hz. PAL improves some of the NTSC limitations;
in particular, the hue errors.
PAL features:
• 625 horizontal lines per frame, 576 of which form the picture
• 25 frames per second.
Composite Video and S-Video
Color video picture signals have four basic components:
• Luminance (brightness)
• Three chrominance (color values)—red, green, blue
These four elements can be combined in several different ways to produce a video signal.
Composite Video
Composite video combines both luminance and chrominance portions of the signal into
one signal for transmission along one wire. This is the most common type of signal used
by home video systems. Broadcast signals also consist of composite video signals that
follow one of the composite video broadcast standards (NTSC, PAL, SECAM). These
standards specify how the luminance, chrominance, blanking pulses, sync pulses, and
color burst information are combined.
S-Video
S-Video (separated video) signals transmit the luminance and the chrominance information
separately. This type of video signal is also called Y/C (luminance/chrominance) or ‘color
under’. This system improves picture quality by keeping any signal interaction and
subsequent degradation to a minimum.