JPS59119971A - Decoding system - Google Patents

Abstract

PURPOSE:To shorten the coding processing time by storing a table showing a bit pattern and its corresponding run length for each bit length and then extracting successively the bits more by one out of a coding bit train to compare them with the bit pattern. CONSTITUTION:The coding part 6' of a facsimile receiver consists of a processing part 8', an address register 9 and a memory 11'. The memory 11' stores the 1st table showing the bit patterns and their corresponding run lengths and the 2nd table showing the head address for each bit length of the 1st table respectively for each bit length. A bit train to be decoded is extracted out of the coded bit train. Then both the 1st and 2nd tables are used to read out a bit pattern having corresponding bit length from this bit length. Both patterns are compared with each other. If the coincidence is obtained between these bit patterns, the run length is delivered. While the bit train to be decoded is increased by a bit if no coincidence is obtained.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a decoding unit of a facsimile receiving apparatus that decodes a run-length encoded bit string to obtain a run length, and relates to a decoding unit that can shorten the decoding processing time. Regarding the method.

(b) Background of the technology In facsimile communication, in order to compress the bandwidth, a white bit pattern area 2 and a black bit pattern area 2 are placed between flag areas 1 and 1' indicating breaks in one line, as shown in the encoded bit string shown in Figure 1. ,
pattern area 3, white vinyl.

As shown in code pattern area 4, a black and white alternating bit pattern area is provided starting from a white bit pattern area, and within this area, a run length representing the number of white or black bits (including 0) is set for each run length. If it is black, it is encoded in 4 to 12 bits, and if it is black, it is encoded in 2 to 13 bits.
The receiving side decodes this to determine the run length and displays it in black and white. Note that this encoded bit pattern does not have the same bit pattern with the same number of bits, and in text or drawings transmitted by facsimile, one line is white, then black, then white. Furthermore, even if the next part of the classification flag area 1 is black, it is initially represented as white and the number of bits is 0, so that it can be determined whether it is white or black.

(C) Prior Art and Problems Fig. 2 is a block diagram showing the configuration of a facsimile receiving device based on a conventional decoding section; Fig. 3 is a block diagram of a conventional decoding reference table; The figure shows a flowchart of a conventional program.

In the figure, 5 is a receiving section, 6 is a decoding section, 7 is an output section, 8 is a processing section, 9 is an address register, 1o is a table counter,
11 is Memo IJ, 121-1. Data area, 13 bit pattern area, 14 program area, 15! /'i
16 is a table area, 16 is a run length area, 17 is a bit length area, 18 is a bit pattern area, and 19 is a run length area.

The transmitted encoded bit string shown in FIG. The table area 15 of the 0 decoding unit 6 that outputs black bits stores two decoding reference tables, one for white and one for black, as shown in FIG. A program shown in the flowchart is stored.

The decoding reference beam shown in FIG. 3 does not have a white or black run length, but includes a bit pattern area 18, a bit length area 17 indicating the bit length of this bit pattern, and a run length area 19 indicating the run length of this bit pattern. The lines showing these are e, N of the thin length type.
There are only Next, when determining the 2nd length, for example in the case of white, a description will be given according to the flowchart of FIG. The input white encoded bit string shown in FIG. 1 is stored in the data area 12 under the control of the processing section 8. Next, the processing section 8 resets the table counter 10, loads the 7' program stored in the program area 14, and performs subsequent operations according to this program. The white bit pattern stored in data area 12! 1l11
The next bit is taken out one bit at a time, the next two bits are taken out, the next bit is three bits, and so on, an address signal is sent through the address register 9, and the address signal is transferred to the bit pattern area 13. Each time this l bit is transferred, the address signals from the 1st row to the Nth row of the decoding reference table in the table area 15 are sequentially transmitted via the address register 9, and the bit length area 17 of the decoding reference table is 0 In this case, the bit length is the same, otherwise, the table counter O receives the address signals from 1b to N row 1 of the decoding reference table and adds 1 to the output level and the count number is N. Continue comparing until If the bit lengths are the same, compare the contents of the bit pattern area 18 corresponding to the bit length with the contents of the bit pattern area 13, and if they are not the same, the count value of the table counter 0 is further sequentially counted until the same bit length is found. The above operation is continued until the table count number reaches N by adding 1.

This operation continues until a turn with the same bit length and the same number of bits as the bit pattern transferred to the bit pattern area 13 is found. If the same bit pattern with the same bit length is found, the contents of the corresponding run length area 19 are transmitted via the address register 9 by the address signal of the gin length area 16 in FIG. 2, and the run length is stored. However, in this method, N rows of the decoding reference table are compared every time the number of bits to be transferred to the pit nozzle (turn area 13) increases by one, so the run length is determined by (a certain pit) length. If it is, the comparison is not made after that, so in this case, N rows are not looked at.) The search step is almost txN (
t is the bit length that determined the run length), and p in the worst case is approximately KxN (K is 12 for white and 13 for black), which has the disadvantage that the processing time for encoding the run length becomes long. -) (d) Object of the Invention In view of the above drawbacks, an object of the present invention is to provide a decoding method that can shorten the processing time for decoding run lengths.

(e) Structure of the Invention In order to achieve the above object, the present invention stores bit patterns for each bit length in a storage device in a decoding unit of a facsimile receiving device that decodes a run-length encoded bit string to obtain a run length. A first table representing the corresponding run length and a second table representing the start address for each bit length of the first table are stored, and the encoded bit string is stored. From the number of bits of the first bit string extracted one bit at a time, the second table is searched to find the first address that matches the number of bits. The encoded bit string of the bit length of the table and the first
If there is no match, it extracts 1 bit more than the encoded bit string and repeats the above operation, and if a match is found, it compares the bit string of the first table. This decoding method is characterized by finding a run length corresponding to this bit pattern.

An embodiment of the invention will be described below with reference to the drawings. Fifth
The figure is a block diagram showing the configuration of a facsimile receiving apparatus mainly including a decoding section according to an embodiment of the present invention, FIG. (J3) is a table diagram showing the correspondence of run lengths to bit patterns with the same bit length for each bit length. FIG. 7 shows a flowchart of a decoding program according to an embodiment of the present invention.

Components in FIG. 5 that have the same functions as those in FIG. 2 are indicated by the same symbols. 6
' is the decoding unit, 8 processing unit, 11' is the memory, 4' is the program area, 20.21 is the table area, 22 in Figure 6 is the bit length area, and 23 is the beginning of the table for each bit length. address area shown, 24 is a bit pattern area, 2
5 indicates the run length area, nl is the number of bit pattern types when the bit pattern has the largest number of bits plus 1, and n11 is the bit pattern when the bit pattern has the largest number of bits. It is the number of types plus 1, and the 13-bit 0# shown in the 49th entry. There are two tables shown in Figure 6 (A) (f3), one for white and one for black, and the table for white and heat shown in (A) is the fifth table.
The white and heat tables shown in (c) in the table area 21 of the figure are stored in the table area 20 of FIG. 6th
In the bit length area 22 in the figure, the number of bits in the bit pattern is from the smallest to the largest, for example, 4 to 1 for white.
In the bit pattern area 24, all bit patterns with the same number of bits are shown in order from the one with the least bit a, and the boundary between the same number of bits and the number of bits with one more bit is 13 bits. It is indicated by zero. Further, the start addresses of bit patterns having the same bit length are shown in the address area 23 indicating the start of the table for each bit length. Furthermore, the run length corresponding to the bit pattern is shown in the run length area 25 corresponding to the bit pattern.

The program shown in the flowchart of FIG. 7 is stored in the program area 14' of FIG.

Here, what is different from the conventional example is the method of determining the run length, so the operation of determining the run length in the decoding section 6' will be explained using the case of white as an example and according to the flowchart of FIG. 7. The input white encoded bit string shown in FIG. 1 is stored in the data area 12 under the control of the processing section 8'. Next, the processing section 8' reads out the program stored in the program area 14' and performs subsequent operations according to this program. From the white bit pattern stored in the data area 12, extract 1 bit more, such as 2 bits after 1 bit, 3 bits after G, send an address signal via the address register 9, and transfer it to the bit pattern area 13. do. This transferred pi.

When the number of bits reaches 4 bits, a 4-bit address signal is sent to the bit length area 2 of the table area 20 in FIG.
The address indicating the top of the table in section C is read out, and the pattern of no. If they do not match, the 4-bit bit patterns are compared one after another until the point I is reached. If the same bit pattern does not exist, the number of bits to be transferred to the bit pattern area 13 is set to l.
5 bits in the bit length area 22 is increased in the same manner as above.
B.

6 (4), and reads the corresponding address indicating the head of the table.
) are sequentially read out and compared up to the bit pattern with 13 consecutive zeros. 1. Increase the number of bits of the bit pattern to be compared by one pit and repeat the comparison If the same bit pattern as the bit pattern transferred to the bit pattern area 13 in FIG.
The address of the run length area 16 of the fifth prisoner is transmitted via the address register 9, the run length is stored, and the run length is sent to the output section 7.

Therefore, in this method, the number of steps to determine the run length is approximately the same (t is the bit length used to determine the run length, ni
is the number of bit patterns with the same number of bits + 1, n
i is 4 bits, and it is almost the same whether it is 13 bits or 4 bits)
This is smaller than the number N of all types of bit patterns, and even in the worst case, the number of steps is Σn1 = N + cl (K is 12 for white, 13 for black, ct is 9 for white, In the case of 12), the number of steps is much smaller than in the conventional case.

Therefore, the processing time for decoding the run length becomes very short.

(g) Effects of the Invention As explained in detail above, the present invention has the effect of greatly shortening the processing time when decoding run lengths in the decoding section of a facsimile receiving device.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of an encoded pit string, Figure 2 is a block diagram showing the configuration of a conventional facsimile receiving device mainly consisting of a decoding section, and Figure 3 is a configuration diagram of a conventional decoding reference table. ,
FIG. 4 is a flowchart of a program in the conventional example, FIG. 5 is a block diagram showing the configuration of a facsimile receiving apparatus mainly consisting of a decoding section according to an embodiment of the present invention, and FIG. A block diagram of a decoding reference table according to an embodiment of the invention, and FIG. 7 shows a flowchart of a decoding program according to an embodiment of the present invention. In the figure, 1.1' is a flag area indicating a break in one line, and 2
, 4 is a white bit pattern area, 3 is a black bit pattern area, 5 is a receiving section, 6.6' is a decoding section, 7 is an output section, 8
, 8' is a processing unit, 9 is an address register, 10 is an id table counter, 11.11'U memory, 12 is a data area, 13.18.24 is a bit pattern area, 14.1
4' is a program area, 15°20.21 is a table area, 16 is a run length area, 17,221Ii is a length area, 19.25 is a run length area, and 23 is an address area indicating the head of the table.

Claims (1)

[Claims] In a decoding unit of a facsimile receiving device that decodes a run-length encoded bit string to obtain a syn-length,
A first table representing a bit pattern for each bit length and a run length corresponding thereto, and a second table representing a start address for each bit length of the first table for each bit length are stored in a storage device. Then, from the number of bits of the first bit string, which is extracted one by one from the encoded bit string, refer to the second table to find the start address that matches the number of bits. The coded bit string of the bit length in the first table is compared with the first bit string sequentially from the first address, and if there is no match, the coded bit string is compared until a match is found. A decoding method characterized in that the above operation is repeated by extracting one bit at a time, and if a match is found, the run length or run length corresponding to this bit pattern in the first table is determined. 0