Sony DTV-01, Руководство пользователя

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21
Inputs
RF Inputs
There are three independent RF inputs which allow the user to have cable,
an outdoor antenna aimed for VHF and UHF stations and another an-
tenna oriented for digital TV stations. Each RF input has a channel num-
bers assigned to it:
R F C h a n n e l N u m b e r A s s ig n m e n t
I n p u t C h a n n e l N u m b e r s
C a b le 1 - 1 2 5
V H F / U H F 2 - 1 3 / 1 4 - 6 9
D T V 1 - 9 9
They are selected from the ANT remote control button.
Composite Video
This is a single video 1, 2, or 3 input cable that carries the combined Y
and C signal. The TV/Video remote control button selects it. This com-
posite signal requires the receiver to first separate the two components,
usually using a comb filter. The chroma is demodulated into individual
color components, such as RGB, before the color information can be used.
These additional processing steps reduce resolution and could add noise,
but composite video is a convenient method of transporting a video sig-
nal.
P M 3 3 9 4 , F L U K E & P H I L I P S
ch3
ch2
ch1
C H 1 ! 5 . 0 0 V ~
CH2!1.00 V~ L=121
C H 3 ! 5 0 0 m V = C H P M T B 1 0 . 0 u s - 1 . 0 8 d v c h 1 p
1
2
3
This scope shot is taken of a video signal that produces a blue screen.
The top waveform is composite video and contains a combined signal.
The middle waveform is the chroma signal from the S video output. It
contains the burst after the retrace blanking area. The bottom waveform
is the luminance signal containing the H sync pulse below the base line.
S Video Input
The S input refers to Separate Video inputs consisting of independent
luminance (Y) and chroma (C) signals and a shield wire for each. They
are input using a 5 pin standard connector. The fifth pin serves to close a
switch in the jack that identifies the presence of the S video plug. The S
Video signal is selected instead of the composite video 1-3 when the S
video plug is detected.
The S video’s luminance signal is the picture’s brightness level signal.
This Y input signal also carries both of the horizontal and vertical sync
pulses. The chroma signal contains the color information phase refer-
enced to the burst frequency of 3.58MHz. This C input contains 8 cycles
of reference burst signal in the open retrace interval. The chroma signal
requires demodulation into individual color components such as RGB
before the color information can be used.
Component Video
Conversion
Video can be made of four components:
·
Luminance or Y which defines the brightness level and
·
Color, which is made of three components, called R-Y, B-Y and G-Y.
We can mathematically calculate the fourth component (G-Y) from the
others so only three components are required for video:
Assuming R+B+G = Y, and (R-Y)+Y = R, then (G-Y) = -R-B.
The manufacture of the G-Y signal can be performed in an electric matrix
consisting of summing op amps for adding (+) and subtractive op amps
for the difference of the two signals (-). By adding the (inverted) signals,
the last G-Y component can be derived.