Canon FACSIMILE BASIC 2000 Service Manual page 181

LSZ, A2=A1-LSZ, and A3=A2-LSZ.
In the case of an inaccurate prediction, range A=LSZ.
*3 Actually, hexadecimal 8000.
*4 Actually, the hexadecimal value will be shifted to the left two times,
and thehexadecimal will be over 8000.
Next, the encoding for continuos accurate predictions will be simply
explained.
The assumptions below will be made for easy understanding.
The value of an accurate LSZ will be decimal 100 in all statuses.
Range A will have limits of decimal 8000 to 10000, and when range A
is below decimal 8000, the lead encoding bit will be pushed out, and
the encoded image data will be output.
At this time, Range A will be adjusted so that it is over decimal 8000
(decimal 1000 added).
An accurate range will be MPS, and an inaccurate range will be LPS.
RANGE
LPS
10000
Range
Range
A1
A2
MPS MPS
8000
Pixel No.
1 2
encoded
Accurate
Yes Yes
Encoding
0 0
position
Range initial
10000 9900
position
Renormalization
New initial
position
LSZ 100 100
Range A
9900 9800
Encoding
No No
output
Output
encoding
Fig. 5-32 When Predictions are Continually Accurate
In this case, the encoding 1 bit is output for the first time when Range A
falls becomes less than 8000 in the 21st pixel.
The following output encoding is shortened and its compression increased.
G3 FACSIMILE COMMUNICATIONS
LPS
MPS MPS MPS MPS
MPS
3 4 5 6
Yes Yes Yes Yes
0 0 0 0
9800 9700 9600 9500
100 100 100 100
9700 9600 9500 9400
No No No No
8900
Renormalization
MPS
MPS MPS
19 20 21 22
Yes Yes Yes Yes
0 0 0 0
8200 8100 8000 7900 8900
1000
8900
100 100 100 100
8100 8000 7900 8800
No No Yes No
1 bit 0
5–39
1
2
3
4
5
6
ït
çi