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To record the quantitated numeric values more efficiently, they will be coded.
To make coding easier, the quantitated value of macro blocks will be scanned
in a zigzag pattern or alternately.

1

Because there are a multitude of zeros (unnecessary information) in quantitated value,
it does not show all the zeros.  What it shows, for example, is “six 0s” when there are 6
consecutive zeros.

2

Code is shown in binary numbers.  Frequently showing numbers gets the shortest code,
and rarely appearing numbers get longer code in order to decrease the overall amount of
data.

Compression of moving pictures is done the same it is for still pictures.
Pictures are divided in macro blocks, and the movement changes on each block is “detected”,
“predicted” and “corrected”. Also, assuming there are many occasions when entire pictures will
be replaced by different ones, non-compressed original pictures (I picture) and less compressed
pictures (P picture) are inserted in frames at regular intervals.  The pictures between them will
be inserted between these frames by predicting former and latter I and P pictures.

When an entire picture changes (random search, etc.), “detection”, “prediction” and
“correction” of the movement cannot be made.
Therefore, original pictures (intra = I picture) are inserted at intervals of every 6 to 15
frames and predicted pictures (P picture) from I picture every 2 to 6 frames.
Also, mutually predicted pictures among the I and P picture (bi-directionally = B picture)
are inserted between these I and P pictures.
B pictures (frames) on 1 ~ 2 below are predicted and made from I picture (frames) and P
pictures on 0 and 3.

The system detects each macro block and compares the current picture to the past
memorized ones, and compiles data about the direction and distance of movement vectors.

1

2

3

4

3

4

5

*

6

*

* * *

It detects which square (block) corresponds to this one in the previous picture and measures the
moved amount and directional vectors.

There are parts similar in previous and successive pictures.  Therefore, it is not necessary
to transfer every bit of information on the current picture, since similar parts of the previous
picture can be used.
To determine what content of the current picture is to be transferred, prediction is made by
comparing the amount and direction of movement in the previously memorized picture and
the current one.
Then, only the parts with margin of error, meaning the parts that changed and/or were
added, are recorded.

When the part without a pit continues to track a disc, it becomes difficult to create a laser spot to
follow based on a pit.  Also, it is difficult to judge how many 0s and 1s are being followed.
Therefore, it is necessary to limit the length of the part without a pit on the track.  That means, it
is necessary to limit the succession of 0s and 1s.
8/16 modulation converts the original 8 bit data into 16 bit to limit the succession of “0s” or “1s”
from 3 to 11.  Also, NRZI modulation makes both of the pit edges a “1”.  With this, code reading
and recording density accuracy increases.  (See below)

●

Move OL up and down to focus on the disc pit.

●

Disc (DVD) face shake  

±

 300

µ

m

Accuracy of Turn Table  150

µ

m p-p

_

Suppression under 

±

 0.23

µ

m

●

Move the Object Lens between the internal and external circumference (at a right-angle to
the track) to place the beam on the track.

●

Disc (DVD) core 100

µ

m p-p

Core at TT, fastened 50

µ

m p-p

_

Suppression under 

±

 0.022

µ

m

●

Because the object lens’ movement is small (about 

±

 0.35m/m in the tracking direction), the

entire pick-up is moved near the target track with the thread motor.

●

In normal reproduction, it is necessary to make a fine movement, in which the object lens
stays around a free neutral point.  In this case, it is necessary to make a high-speed move in
order to suppress object lens vibration.