Specifications

CHAPTER 2 OPERATION AND TIMING
2-42
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1999 CANON INC. CANON SUPER G3 FAX BOARD-F1 REV.0 MAY 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Reference:
If a match is made, the line being processed will be referred to as “being typical.” If a non-match
is made, on the other hand, the line will be referred to as “not being typical.”
When making a prediction for the first line of an image, the background is used as representing
the immediately preceding line.
b. Figure 2-403 shows model templates (enclosed by thick lines). Combinations of pixels (pixel
pattern; 10 bits) are communicated to the arithmetic coding block.
All 1-bit pixel patterns of the template exist within the learning table, and are used by the
arithmetic coding block when referring to prediction levels of pixels in question and status
numbers in the learning table according to each pixel pattern.
Figure 2-403 Model Templates
Reference:
The choice between the 3-line model template and the 2-line model template is determined by
LRLTWO found within the 2-level image header (BIH).
A pixel represented by “?” is a pixel to be coded, and is outside the template.
A pixel represented by “AT” is a special pixel called an “AT pixel.”
An AT pixel makes a template adaptable by changing its position, and will prove to be highly
effective when coding an image consisting of cyclic lines (e.g., dither image).
The position of the AT pixel in the diagram is the initial position of any AT pixel. The board,
however, will keep the AT pixel at its initial position so that it will not make use of an adaptable
type template.
AT
3-line model template
?
AT
2-line model template
?