Sony DVP S9000ES User Manual download pdf (Page 8)

Sony’s Motion Adaptive Field Noise Reduction uses new

technology to overcome the old compromises. Thanks to the

new circuit, the DVP-S9000ES can achieve very high signal-to-

noise ratio, very high resolution and very accurate motion

— all at the same time!

To overcome motion artifacts, the Sony design actively analyzes

the fields for movement. The system divides the image into

blocks of 4 pixels high by 16 pixels wide. This specific

rectangular shape is based on the understanding that most

movement in video images is horizontal. In blocks where no

large changes are detected between fields, the system applies

conventional noise reduction.

When large changes are detected between fields, the system

automatically searches for block movement. The search

“window” is 11 pixels high by 31 pixels wide.

By finding matches for blocks that have moved, Sony’s Motion

Adaptive Field Noise Reduction makes it possible to apply noise

to areas of screen movement, in addition to the still background.

The system compares data from the two fields by a mathematical

method called the Hadamard transform. Noise, in the form of

differential luminance (Y) signals, is analyzed in blocks one

pixel high by 8 pixels wide. The Hadamard transform converts

the noise into an easily processed frequency distribution. To

reduce errors, eight operations are performed for each pixel. The

average of the eight values is then used. A limiter is then used to

extract noise from the converted signals. Than a reverse

Hadamard transform generates an error-correction signal that is

added to the video signal to suppress noise.

In addition, Sony’s Motion Adaptive Field Noise Reduction

performs the same process for noise in the color difference

channels, C

and C

. Since luminance and color difference

signals are separately processed, their noise reduction can be

individually optimized.

The mathematics of this noise reduction process may be

complex, but the results are easy to appreciate. The circuit

accomplishes three formerly elusive goals simultaneously:

1. Clean noise-free images on both moving portions and still

portions of the screen.

2. The full resolution of the DVD.

3. Clear and natural image movement, without ghosting or other

motion artifacts.

Another characteristic limitation of MPEG-2 compression is

block noise. This is the tendency for delicately shaded picture

areas to be rendered as solid rectangles of color. Instead of a

continuous contour of color on the cheek of an actress, fading

softly into shadow, you see subtle squares of approximately

correct color. Block noise is most apparent at the edges where

squares meet. This effect is also called mosquito wings, because

it can appear as subtle discoloration in tiny slices of the picture

and just as quickly disappear.

Sony’s MPEG Image Processor mounts a sophisticated, compre-

hensive attack on block noise. The aim of Sony’s system is to

identify those areas of subtle gradation of tone — the areas most

prone to block noise — analyze the gradations and reconstruct

the abrupt steps of tone as more linear, more gradual slopes.

The principal challenge here is to distinguish legitimate steps in

the picture tone (signal) from the unwanted, artificial steps

(block noise). This separation of wanted and unwanted steps is

made easier because the block borders area always at the same

places on the screen. Their location is a fixed attribute of the

MPEG-2 compression used in the DVD format.

The DVD format divides the screen into 2,700 blocks (90 hori-

zontal by 30 vertical). Each block measures 8 pixels horizontal

by 8 pixels vertical. They’re shown as vertical rectangles because

of interlace scanning. To judge for block noise, the MPEG Image

Processor establishes the three pixels to the left and right of the

Block Noise Reduction

Fig. 7: Sony’s Motion Adaptive Field noise reduction identifies and suppresses noise

across the entire screen area — in moving parts of the picture as well as the motionless

background. The process uses advanced motion detection and a Hadamard transform to

suppress noise without sacrificing detail or generating motion artifacts.

Fig. 6:

Sony analyzes the video fields for movement by dividing the fields

into blocks that are 4 pixels high by 16 pixels wide. When big changes

are detected between two fields, Sony’s MPEG Image Processor

determines that there is screen movement. The system attempts to match

the block across a search window that extends four pixels up, three pixels

down, eight pixels to the left and seven to the right.

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Sony DVP S9000ES User Manual Page 8

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