Pioneer DV-S5, Service Manual

Page: 82 / 87

82
DV-05, DV-S5
7.4 CIRCUIT DESCRIPTION
7.4.1 VIDEO SIGNAL PROCESSING BLOCK
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CXD1854Q Block
The major processing functions of the CXD1854Q block are:
(1) Field-correlative cyclic digital noise reduction
(2) Block noise reduction
(3) Horizontal contour compression
These functions are performed for the Y signal and not performed
for the C signal.
(1) Field Correlative Cyclic Digital Noise Reduction
For eight-bit digital video data input to the CXD1854Q, noise
reduction is achieved through the subtraction of data of one field
from the corresponding data one field before. This data is stored in
a buffer zone where the subtraction process takes place and this
buffer zone is a 512Kbit DRAM.
The noise signal detected as a result is sent to a non-linear circuit. If
the difference is larger than a specific value, it is regarded as “a
change in picture,” and no canceling calculation is made.
(2) Block Noise Reduction
The Horizontal Block Noise components in the field which are
generated through DCT for the MPEG encoding are rejected.
They are detected through comparing input data between blocks.
The noise signal detected as a result is sent to a non-linear circuit. If
the difference is larger than a specific value, it is regarded as “a
change in picture,” and no canceling calculation is made.
(3) Horizontal Contour Compensations
This is performed by emphasizing components in the region of
2.3MHz.
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MC44724A Block
The digital video encoder MC44724A changes the digital component
signals to analog video signals (Y signal, C signal, Cr signal and Cb
signal).
It is added the digital video encoder for the digital processing of
CXD1854Q.