Canon fax basic 2000 서비스 매뉴얼
G3 FACSIMILE COMMUNICATIONS
5–28
4.3.6 Effect of MR coding scheme
The table shows the size of compressed data by the MR coding scheme and
the MH coding scheme.
In the document example in Fig. 5-23, the compression ratio becomes
about 71% as shown in the following formula by the MR coding scheme
compared with the MH coding scheme.
Data size by MR coding / Data size by MH coding = 278/390 = 0.7128 ...
Approx. 71%
In actual coding of the document, the compression ratio becomes between
about 70% to 90% depending on the pattern of the document and the
line density.
4.4
MMR Coding Scheme
MMR stands for Modified Modified READ, and somewhat resembles the
MR coding scheme. By MMR, coding starts from a white line, and there
are no restrictions in parameter K. In other words, the initial line is taken to
the be the reference line, and only differences from the previous line are
coded by MR right until the end of the page. For this reason, as a condition
for use of MMR, MMR is limited to instances where error-free communi-
cations can be assured. So, with G3 facsimiles, MMR is used only in com-
described later.
Table 5-7 Comparison of the Effect by MR Coding and MH Coding
MR coding
MH coding
1st line
43 bits
41 bits
2nd line
14 bits
29 bits
3rd line
56 bits
56 bits
4th line
34 bits
54 bits
5th line
55 bits
54 bits
6th line
22 bits
54 bits
7th line
24 bits
48 bits
8th line
30 bits
54 bits
Total
278 bits
390 bits