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Video Processing Block
Tuner
The Micro controls the tuner through the use of data and clock communi-
cations. Both share in the TV station tuning functions:
TV Tuning Functions
Micro
Data output identifies TV bands
(Low/high VHF, UHF, Cable) and TV
channel.
Data output uses AFT feedback to fine-
tune the TV station.
Uses TV video sync to ID an active TV
station (auto programming).
Memorizes the location of active TV
stations (external memory IC).
Video Inputs
In the 20" and smaller screen size BA-4 chassis, video input selection is
performed by the Jungle IC. As many as three video inputs are available
for the user to select from:
•
Tuner video
•
Video 1 – composite or S video
•
Video 2 – composite video only
When the S video 1 jack is present in a model, the composite video 1
input signal must pass through the S video jack. The composite video 1
signal leaves the jack at the luminance (Y) line to the Jungle IC. When S
video 1 is input, the round S video plug grounds the SW input to the
Jungle IC so it knows to route the separate Y and C inputs differently.
In the 27" screen BA-4 chassis, there maybe an additional video input
and video output jack. Therefore, a video switcher IC is used before
entering the Y/C Jungle IC as composite video or Y & C (S video).
Tuner
Uses input data to change the internal
local oscillator frequency for station
selection.
Outputs center of station AFT voltage.
Outputs TV video and audio signal
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Digital Comb Filter
Some TV models have a digital comb filter connected to the Y/C Jungle
IC. These models must be identified to the Jungle IC so it knows to route
composite video (V) out to the filter and receive luminance (Y) / color (C)
information from the filter as a departure from the internal video-process-
ing path. Data from the Micro identifies the presence of the external
comb filter. This data comes from ID codes found in the Micro and memory
IC. The technician can access them from the service mode (further infor-
mation is in the service manual).
The purpose of a comb filter is to separate a composite video signal's
luminance (Y) information from its color (C) information. Digital comb
filters have gone further. There are currently four types of comb filters
available on the TV market:
1. Analog Comb Filter - This type of filter will help increase the picture
resolution to above 330 lines.
2. Digital Comb Filter – This performs the same function, but the sepa-
ration is done in the digital domain.
3. Digital 2-D Adaptive Comb Filter – This filter employs a memory to
analyze the picture information in two dimensions (2-D), vertically
and horizontally.
The result is not only Y/C separation, but also higher resolution than
a standard digital comb filter by simulating detail and reduction of dot
crawl. The word "Adaptive" indicates that the digital processing is
constantly analyzing and selecting the best algorithm available in the
filter.
4. Digital 3-D Adaptive Comb Filter – This filter is an improvement over
the 2-D that only processed information within that field. The 3-D
filter analyzes information over frames to compare and eliminate noise,
interference and irregularities, as well as separate the Y from the C.
Different digital filters are used in different models of Sony TVs.
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