JPS5816666B2 - Redundancy reduction coding transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a redundancy reduction coding transmission system, in particular, for example, in the transmission of facsimile signals, an input screen or the like is scanned and decomposed into pixels having one of two levels.
Redundancy of the input screen, etc. is reduced by encoding the state of a pixel area having a first level between the first scan line immediately before the scan line to be encoded and the second scan line to be encoded. Redundancy suppression coding transmission method that suppresses and efficiently encodes pixel information that has two levels, such as facsimile signals, can be coded using the following three methods, depending on how much correlation between scanning lines is used. Can be classified into types.

The first is a one-dimensional processing method that does not utilize the correlation between scanning lines, the second is a two-dimensional batch processing method that utilizes the correlation between a plurality of limited scanning lines, and the third is a method that uses the correlation between adjacent scanning lines. This is a two-dimensional sequential processing method that sequentially uses the correlations of

The two-dimensional sequential processing method is a method that attempts to utilize the two-dimensional correlation of the input screen as much as possible, and is a method that can be expected to have an extremely high redundancy suppression effect compared to other processing methods.

Conventional seven methods include Picture Band
widthCompression (1972 Go
(Published by Rden & Breach), pages 224-22
C and G on page 8.

An Efficien by B eau de tte et al.
t Facsimile System for Wea
Systems such as the one described in the paper entitled ``Ther Graphics'' are known.

That is, a first state where the 10th run touching the first level run on the second scan line is not on the first scan line, and a first state where the 10th run touching the first level run on the first scan line is not on the first scan line. a second state in which no runs of levels are on the second scan line, and only one first level run on the first scan line and only one first level run on the second scan line; A method is known in which three adjacent third states are identified and each state is encoded.

However, in the above method, only one
A state in which two or more first level runs on a second scan line touch each other, or a state in which two or more first level runs on a second scan line touch each other, or a single first level run on a second scan line and a single first level run on a second scan line touch each other. 2 on the line
Since the encoding method is simple, it has a drawback that it cannot effectively encode complex conditions such as a condition in which more than 10 first level thins are in contact with each other.

The present invention alleviates these drawbacks and provides a complex structure of the pixel area with the first level between the first scan line and the second scan line so that even complex screens can be encoded effectively. The system also newly identifies and encodes states, and the drawings will be described in detail below.

The person in Figure 1, the person in Figure 2, and the person in Figure 5 are examples of pixel information for two scanning lines to be encoded, respectively.
FIGS. B to 5B each represent the encoding mode in the form of a function.

Reference numerals 1, 6, 8, 10, and 12 in the figure are the first scanning line immediately before the scanning line to be encoded, respectively;
7, 9, 11, and 13 are the second scanning lines to be encoded.

Further, 3 is a pixel having a first level, and 4 is a pixel having a second level.

5 is the scanning direction, and in the following it will be assumed that scanning starts from the pressure to the right, but generality is not lost by this.

Figure 1: The person is at the first level on the second scanning line 2
This is an example of a first state (hereinafter referred to as pattern 1) in which the first level run that is in contact with 2 M "14 is not on the first scanning line 1.

Specifically, the pixel area indicated by ■ in the figure is pattern l, 1 is the pixel area of the previous pattern, and ■ is the pixel area of the next pattern.

For the following explanation, four reference points P1 in one pattern are used.
．． P2, Ql, and Q2 are defined as follows.

Pl: Position of the pixel having the leftmost first level on the first scanning line 1, 6, 8...12 P22 Second scanning line 2, 7, 9...・The position Q of the pixel having the first level on the leftmost side on 13 and the position Q2 of the pixel having the first level on the rightmost side on the first scanning line 1, 6, 8...12 2. The position of the pixel having the rightmost first level on the second scanning line 2, 7, 9, . . . 13 and Q4-P3 are defined as follows.

Q4: Point p on the right side between Ql and Q2
3: Drop 1 Diagram A that is on the left side of p, and P2
, point Q21 is the reference point Q2 of the previous pattern, and point P3□ is the reference point P3 of the next pattern.

In pattern 1, the run lengths of the first and second levels between points Q21 and patO on the second scan line 2 are encoded.

One method for doing this is to perform run-length encoding from immediately after the point Q2□ to immediately before the point P3°.

In other words, the run length in figure 1 is 111 s 131 □
. This is a method of encoding ``13 #1149115.

As a second method, first, 2n run lengths are sequentially calculated from in of the first level run between points Q2□ and P31 and the run length of the second level immediately after Q2□. There is a method of encoding the 2n+1th gin and not encoding it.

In other words, the number of runs at the first level in Figure 1 is n=2, and the value of n and 111 j 1121113 j 1
14 is encoded, and 115 is a method that is not encoded.

In the following pattern 1, encoding is performed using the second method.

At this time, the code word of pattern 1 has the following structure.

P(1)N(n)L(71)L(72)--L(1
2n) However, P(1): Code word representing pattern 1 N(n) Code word representing number n of two runs L(A): Code word representing run length l In the case of the pixel arrangement shown in FIG. 1A, becomes a code word as shown in FIG. 1B.

FIG. 2A shows a second state (hereinafter referred to as pattern 2) in which there is no first level run on the second scanning line 7 that is in contact with a first level line on the first scanning line 6.

This is an example of the case.

At this time, the reference point P1'Q1 is the point P1□s in Fig. 2A, respectively.
Q1 becomes □.

The reference point P2°Q2 is pseudo-positioned as a pixel position P2□ immediately below the point P12 and a pixel position Q2□ that is one position to the left of the pixel immediately below the point Q1□, respectively.

By assuming point Q2 in this way, if pattern 1 occurs immediately after pattern 2, the level of the first run of pattern 1 can always be the second level.

The code word of pattern 2 is as shown in FIG. 2B.

P(2) is a code word representing pattern 2. Figure 3A
is a third state (hereinafter referred to as pattern 3) in which only one first level run on the first scanning line 8 and only one first level run on the second scanning line 9 touch. Here is an example.

In this example, reference point P1. P2. Q1. Q2 becomes each point P13 # P23 j Qt3 M Q23.

In pattern 3, points pts and P23 and points Q1B and Q2
The respective relative distances d13 and d23 of 3 are encoded.

In other words, the code word of pattern 3 has the following structure.

P(3) D (dla) D (d23) However, P(3): Code word representing pattern 3 D(d): Code word representing relative distance d13"P23 PI3 d23""Q23 Qt3 To Figure 3 An example of encoding in the case of a pixel array is shown in FIG. 3B.

FIG. 4A shows a fourth state (hereinafter referred to as "first level runs") in which only one first level line on the first scan line 10 and two or more first level runs on the second scan line 11 touch each other. An example of pattern 4) is shown below.

In this example, the reference points P1-P2-Qt-Q2 are each P
14°P24 j Q14 j Q24.

In pattern 4, the relative distance d14 between points P14 and P24
, and the number of runs of the second level on the second scan line 11 n1 run length of the first and second levels between points P24 and Q24, i.e. 714 t
'24 s '34 m'44 j '45 are respectively encoded.

In other words, the code word of pattern 4 has the following structure.

P(4)D(d14)N(n)”(11)L(12)
""L('2n+1) where P(4): code word representing pattern 4 d14=P24 PI3 An example of encoding in the case of the pixel array shown in FIG. 4A is shown in FIG. 4B.

FIG. 5A shows a fifth state (hereinafter referred to as "the fifth state") in which only one first level syn on the second scanning line 13 and two or more first level syns on the first scanning line 12 are in contact with each other. An example of pattern 5) is shown below.

In this example, the reference points P1-P2 and Qt-Q2 are respectively the points P1. .

p25s Qt5 s Q25.

Further, the leftmost pixel of the second first level run on the first scanning line 12 is assumed to be P1'.

In FIG. 5A, the reference point P1' is the point P1. '.

In pattern 5, the relative distance d1 between points P15 and P25
5 and point P1. ' and Q2. The relative distance of "15" is encoded.

In other words, the code word of pattern 5 has the following structure.

P(5) D (dl, ) L (71, +1) However, P(5): Code word representing pattern 5 At1=Q2s P15' An example of encoding for the pixel array in FIG. 5A is shown in FIG. 5B. show.

In an actual screen, patterns that do not correspond to any of the above five patterns also occur.

Examples are shown in FIGS. 6 and 7.

The symbols 14 and 17 in the figure are the first scanning lines, is and ia, respectively.
represent the second scan line, respectively.

In the case of the example shown in FIG. 6, a cut is made at a portion indicated by a broken line 16, and encoding is performed by dividing the pattern into two patterns (2) and (V).

Further, in the case of the example shown in FIG. 7, a cut is made at a portion indicated by a broken line 19, and encoding is performed by dividing into two patterns (■) and (2).

In other words, cutting is performed at a portion on the first scanning line where the pixel level changes from the second level to the first level.

FIG. 8 shows an embodiment of the symbol PO+00 representing the pattern.

The code length of pattern 3, which has a statistically high frequency of occurrence, is made the shortest, and the code length of pattern 4.5, which has a low frequency of occurrence, is made relatively long.

The relative distances d13 j d2B m d149 d15, etc. take positive, negative, or zero values.

Therefore, cases other than D (o) are further expressed as follows.

D(d) = S(g) L(ldl) where S(g) 20 or - code word L(A') 2 code word ldl representing length l: absolute value of d D(o), An example of the code for S(g) is shown in FIG.

Statistically, the relative distance values are concentrated near zero and are most often zero, so the shortest code is assigned to D(o).

An example of the code word L(1) representing the length l is shown in FIG.

Since the distribution of length l has a distribution in which the smaller value of l occurs more frequently and is proportional to the reciprocal of the logarithm of l, the code assignment as shown in FIG. 10 is appropriate.

An example of a code word N(n) representing the number n of runs is shown in FIG.

Since the number of runs n has a distribution close to an exponential distribution, the 11th
The code assignment shown in the figure is appropriate.

FIG. 12 shows an embodiment of the encoder portion of the present invention, in which reference numeral 20 indicates an input line such as a facsimile signal having two levels, and 21 indicates an input line for inputting pixel information of the first scanning line.
A first line memory 22 stores pixel information for a scanning line, and a second line memory 22 stores pixel information for one scanning line.
23 is a line memory address control circuit that controls writing and reading of the line memories 1 and 2; 24 is a line memory address control circuit that controls writing and reading of the line memories 1 and 2; 25 is a mode register that stores mode changes for one line; 26 is a pattern identification circuit; 27
is mode run length measurement circuit, 28, 29, 30
, 31.32 are encodings for patterns 1, 2, 3, 4.5, respectively.

The circuit 33 represents a signal line for outputting encoded information.

Pixel information for one scanning line is stored in the line memory 22, and under the control of the line memory address control circuit 23, information for one pixel from each of the line memory 21 and line 1 memory 22 is stored in the mode determination circuit 24. The mode at that position is determined.

There are four types of modes because the pixels of the first scanning line and the second scanning line each have two levels.

If the previous mode and the current mode are different, the new mode is sequentially stored in the mode register 25.

This operation is performed for one scanning line.

During this time, the outputs of the line memories 21 and 22 are configured to be fed back to the input side.

However, after the above operation is completed, the line memory 21
゜220 The contents return to their initial state.

In the second operation, the contents of the mode register 25 are read by the pattern identification circuit 26, pattern identification is performed, the contents of the line memories 21 and 22 are read again, and the output of the mode run length measurement circuit is referred to. while performing encoding corresponding to each pattern.

In this way, by scanning the line memories 21 and 22 twice for one scanning line, it becomes possible to encode the pixel information stored in the line memory 22.

When the encoding for one scanning line is completed, the line memory 22
The contents of the input signal line 20 are transferred to the line memory 21.
pixel information for one new scanning line is stored in the line memory 22.

Thereafter, by repeating the above operations, it becomes possible to encode one screen.

As described above, according to the present invention, the state of the pixel area having the first level is encoded between the first scan line immediately before the scan line to be encoded and the second scan line to be encoded. In a redundancy suppression coding transmission method that transmits a redundancy reduction code, a state in which a single first-level run on a first scanning line and two or more first-level runs on a second scanning line are in contact with each other. The correlation between the scan lines is determined by encoding the state in which a single first level run on the second scan line and two or more first level runs on the first scan line touch each other. It can be used effectively to perform redundancy suppression encoding extremely efficiently even on complex screens, and can be effectively used for band compression transmission of facsimile signals and the like.

In this specification, pixel levels are made to correspond to the first level and the second level, but it goes without saying that it is arbitrary whether the first level corresponds to the white level or the black level. stomach.

It goes without saying that in this specification, "one transmission" includes information being transferred within the same device.

[Brief explanation of the drawing]

Figure 1 A, B, Figure 2 A, B, Figure 3 A, B, Figure 4 A
, B and FIGS. 5A and 5B are explanatory diagrams each showing an example of a pixel area to be encoded and an example of its encoding in the form of a function. FIGS. Explanatory diagram illustrating the state of cutting and encoding into combinations of pixel areas, No. 8
11 to 11 show an embodiment of code assignment to each encoding function, and FIG. 12 shows an embodiment of the configuration of an encoder used in the encoded transmission system of the present invention. In the figure, 1.6, 8.10.12 are the first scanning lines, 2,
7, 9, 11.13 are the second scanning lines, 3 is the pixel having the first level, 4 is the pixel having the second level, 2
1.22 is a line memory, 23 is a line memory address control circuit, 24 is a mode determination circuit, 25 is a mode register, 26 is a pattern identification circuit, 2T is a mode run length measurement circuit, 28 to 32 represent pattern encoding circuits, respectively.

Claims (1)

[Scope of Claims] 1. A screen is scanned and decomposed into pixels of a first level and a second level, and encoding is to be performed while referring to information on the first scanning line immediately before the scanning line to be encoded. Redundancy suppression encoding that encodes and transmits the state of a pixel area having a first level between the first scan line and the second scan line in order to encode information on a second scan line. In the transmission system, at least a state in which a single first level run on a first scanning line is in contact with two or more first level runs on a second scanning line, and a state in which a single first level run on a first scanning line is in contact with two or more first level runs on a second scanning line; An identification function is provided to identify a state in which only one first level run is in contact with two or more first level runs on the first scanning line, and each of the above states is encoded and transmitted. A redundancy suppression coding transmission system characterized by: 2. The first line adjacent to the first level run on the first scan line.
A state in which a run of level 1 is not on the second scan line, a state in which a run of the first level that is in contact with a run of the first level on the second scan line is not on the first scan line, and a state in which the run of the first level is not on the first scan line An identification function is provided to identify a state in which a single first level run on a line and a single first level run on a second scanning line are in contact with each other, and each of the above states is coded. 2. The redundancy reduction coding transmission system according to claim 1, wherein the redundancy reduction coding transmission method is characterized in that the redundancy reduction coding transmission method is transmitted after being encoded.