JPS5927505B2 - Two-dimensional sequential encoding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an encoding method used for efficiently transmitting or storing binary signals such as black and white binary facsimile signals.

Conventionally, as a method for encoding binary facsimile signals, (
1) A run-length encoding method in which the signals obtained by scanning are converted into a time series, and then the sizes of the continuous lengths of white and black (run length RL) are sequentially and alternately encoded and transmitted.
2) A method has been proposed in which signals of a plurality of scanning lines, for example, two, are collectively encoded.

However, the method (1) has low compression efficiency because it does not utilize the property that facsimile signals have a strong correlation in the direction perpendicular to the scanning line direction (vertical). Also,
Method (2) uses vertical correlation for signals of several scanning lines that are encoded at once, but does not use correlation with other scanning line signals, so ( Although the compression effect was greater than that of method 1), it was not sufficient. The inventors of the present invention have solved these drawbacks of the conventional method, and with a relatively small amount of memory and simple circuits or means, the redundancy of facsimile signals can be removed and the amount of codes to be transmitted, that is, the number of bits, can be significantly compressed. We previously proposed a two-dimensional sequential encoding method that enables
No. 2) The present invention furthermore provides two-dimensional sequential encoding which makes it possible to reduce the amount of information or signals to be transmitted, thereby shortening the transmission time, and also to reduce the amount of memory when storing or processing information. The aim is to provide a method.

In the present invention, the positions (hereinafter referred to as addresses) of information change pixels (hereinafter referred to as change pixels) having a binary signal value different from the immediately preceding pixel in a facsimile signal are sequentially encoded. Relative from one changed pixel selected from nearby changed pixels on the same scanning line (hereinafter referred to as the encoding line) as the changed pixel (hereinafter referred to as the encoding line) or on the scanning line immediately before the encoding line (hereinafter referred to as the reference line) It is encoded using the approximate number of pixels (hereinafter referred to as distance).

FIGS. 1, 2, and 3 are diagrams showing examples of facsimile signals, in which small frames without hatching indicate white pixels, and small frames with hatching indicate black pixels. First, the encoding starting pixel A.

and other change pixels are defined as follows. AO: starting pixel on the encoding line that is the starting point of encoding, a1: A on the encoding line.

A2: The next changed pixel after A on the encoding line, b1: A on the reference line. occurs after the pixel directly above A. The first changed pixel that takes a binary signal value different from B2: the next changed pixel after B on the reference line, the encoding procedure is as follows: the pixels on the encoding line and the reference line are Sequential matching is performed, and changed pixels on both scanning lines are detected and encoded.

(Step 1): When two changed pixels B, b2 on the reference line are detected before changed pixel A on the encoding line (second
(see figure), this state is set as the first mode (hereinafter referred to as pass mode), Bl and b2 are encoded with the pass mode code ゛1110゛゜ [see the pass mode column of Table 1 (a)], and the next encoding is performed. The starting pixel for is set to pixel AJ on the encoding line directly below B2.

(Procedure 2): If the changed pixel A on the encoding line is detected before B2 among the two changed pixels B1 and b2 on the reference line (see FIGS. 3A and B), the distance is A.

The second mode (hereinafter defined as horizontal mode) is to encode al and distance Ala2, and this is encoded according to Table 1 (a), and the mode code ``111F'' is added to the bit number [AOa,]. + [Ala2].Here, MH (AOal) and MH (Ala2) in Table 1 (a)
is the value indicated by MH(Xy) in Table 1(b). X and y indicate the previous and subsequent pixels in the parentheses, respectively. The third step is to encode the distance Blal and the distance B2a2 at the same time.
mode (hereinafter referred to as vertical mode), and if it is encoded according to Table 1 (a), the number of bits [Bla,] + [B2
a2].

Here, D(n) is determined as shown in Table 1 (c) according to the value n in parentheses. In the "Vertical mode" column of Table 1, ``-'' means that pixel a1 is detected before B (or A2 than B2), and 8+'' means that pixel a1 is detected before b1 (
Or A2 is detected after B2).

Next, compare the number of encoded bits obtained in this way,
One of the encoding modes is finally selected and adopted under the following conditions.

a) Condition: It is determined that there is a strong correlation with reference pixels Bl and b2, and the third mode, that is, vertical mode, is determined, and distances Bla and B2a are determined.
2 is encoded as an encoded output signal, and a new starting pixel is moved to the position of A2.

For example, in the case of FIG.
The conditions U2Q2 are satisfied, and the encoded signals of pixels a1 and A2 become 1001100F'.

b) When the following conditions are satisfied, the encoding change pixel Al, a2 is the starting pixel A.

, and the changed pixel a1, respectively, are determined to have a strong correlation,
It is decided to encode in the second mode, that is, the horizontal mode, and the horizontal mode code "1111" is followed by the distance A.al
and Ala2, and the new starting pixel is set to A2
Move to the position. For example, in the case of FIG. 3B, the condition is satisfied, and the encoded outputs of pixels a1 and A2 are ゜11110111'2 and ``10'', respectively.

In the above description, conditional expressions (a) and (b) have been used as conditions for selecting and adopting the horizontal mode and the vertical mode, but selection can also be made using other conditional expressions.

For example, or the distance A before encoding.

al, ala2 and Bal la B2a2 may be used.

Note that the code table in Table 1 uses MH codes (Modified Huffman codes, specifically CCITT Recommendation T.4) as an example.
Although the present invention is not limited to the use of such codes, it goes without saying that general variable length codes can be used.

Furthermore, in (procedure 1), pixel A.

The changed pixel directly above a1 is not considered as Bl or b2, but is pixel A. or the changed pixel directly above pixel a1 is included in B,, b2, or pixel A. ，
pixel B if it is not more than n (n is an integer) pixels away from a.
The conditions can be changed so that it is not considered as l and b2. As explained above, in the present invention, addresses of encoded change pixels are sequentially encoded in pairs, but the addresses are selected from change pixels that have already been encoded on the encoding line or the reference line. , are encoded pair by pair using the relative distance from the changed pixel.

Next, although not directly related to the gist of the present invention, an example of boundary conditions used when implementing the present invention will be briefly explained.

(1) Encoding of scanning line starting end pixel The first change pixel to be encoded on each line is always a change pixel from white to black.

Therefore, when the first pixel is black, the first pixel is set as the first change pixel, or the first pixel is forced to be white.

Also, the first starting pixel A on each encoded line.

is set at the position of the first pixel. (2) Encoding of scanning line end pixel The end pixel of each line (according to CCITT Recommendation T.4, one line has 1728 pixels as standard) is encoded as if there is a changed pixel next to it.

Next, an example of a circuit for realizing the present invention according to the above principle will be explained.

FIG. 4A shows an example of the encoding device of the present invention, where 1 is an input terminal for a sampled facsimile signal, and 2 and 3 are each an input terminal for a sampled facsimile signal.
A line memory records line signals, 4 is a memory that stores the starting pixel, 5 is an address control circuit that controls the address of the memory, 6 is an exclusive logic circuit (EOR), 7 is an OR circuit, 11 and 12 are each In the encoded line and reference line change pixel detection circuits, 21, 22, 23 and 24 are change pixels Al, a2, bl and B2, respectively.
25 and 26 are Blal and B2a2 direction detection circuits, 31, 32, 33 and 34 are counters,
40 is a pass mode detection circuit; 51, 52, 53, 54 and 55 are encoding circuits; 60 is a comparison circuit for comparing the number of encoded bits; 71, 72, 73, 74, 75 and 76
are gates, 81 and 82 are address counters of B2 and a2, respectively, and 83 is A.

An address register, 90 a signal synthesis circuit, and 100 an output terminal. Note that some descriptions of the memory shift pulse circuit, counter counting clock pulse circuit, etc. are omitted from the figure for the sake of simplicity, but this does not affect the understanding of the essence of the operation of the present invention.

Next, a more detailed configuration and operation of this embodiment will be explained.

First, the facsimile signal to be encoded is 1 from input terminal 1.
The data is recorded in the encoding line memory 2 line by line.

At this time, as the reference line signal, the previous line signal stored in the encoded line memory 2 is transferred to the reference line memory 3 and recorded. The AO memory 4 has a starting pixel A. information is recorded. The encoding line memory 2 and the reference line memory 3 are controlled by the address control circuit 5 to set the starting pixel A.

The facsimile signals are simultaneously read out sequentially from the positions. The signal read out bit by bit from the encoded line memory 2 enters a changed pixel detection circuit 11. This circuit is the fourth
As shown in FIG.
is transmitted to the a1 detection circuit 21 (flip-flop).
As a result, the Alp line of the a1 detection circuit 21 changes from t゜O'2 to ゞTF', and the Aln line changes from 1r' to ゞO''.
The A2 detection circuit 22 adds "1" to the A2p line when the first changed pixel detection circuit 11 detects a changed pixel after the a1 detection circuit 21 detects a1 (Alp is "1"). This is a flip-flop that outputs.a1 detection circuit 21
The Alp output of the A2 detection circuit 22 and the A2p output of the A2 detection circuit 22 are A, respectively. a, counter 31 and A, a2 counter 32
can be conveyed to. This A. The address control circuit 5 of the al counter 31 is A. Counting of pulses is started from the time when A1 is set, and counting is stopped when "1" is received from the output Alp of the a1 detection circuit 21. (The number of pixels from AO to a1 is counted.) Also, the Ala2 counter 32
When the A1 detection circuit 21 detects a1, that is, pulse counting is started by "F" of the Alp line, and the A2 detection circuit 21 starts counting pulses.
A2 is detected at 2, and counting is stopped by the 1F'' signal from A2p, so counters 31 and 32 each have A.

The counts of A, and Ala2 were recorded;
The signal is transmitted to the al encoding circuit 51 and the Ala2 encoding circuit 52. The encoding circuits 51 and 52 perform encoding using code tables as shown in the horizontal mode column and MH(Xy) column of Table 1.

Next, regarding the encoding of b1, from the reference line memory 3 to 1
The signal read out bit by bit is transmitted to the changed pixel detection circuit 12.

Here, a changed pixel is detected, and the information is A in the EOR circuit 6. Starting pixel A of memory 4. If it is different, the b1 detection circuit 23 detects it as b1, and the output of the BlP line changes from ゛l'' to 8F゜, and Bl
It is transmitted to the al counter 33. After B, is detected (
Similarly, when the B2 detection circuit 24 detects B2, this output is transmitted to the B2a2 counter 34.

In addition, the Blal counter 33 contains B, and the Blal of the detection circuit 23
The outputs from the P line and the Alp line of the a1 detection circuit 21 are added, and the address control circuit 5 is activated by the first 1F signal.
Start counting pulses from , and stop counting at the following ゛1゜.

Note that these B, BlP and A of the detection circuits 23 and Alp line outputs of the detection circuits 21 are similarly applied to the B and al direction detection circuits 25. This Bla, direction detection circuit 25 has a circuit configuration as shown in FIG. 4C, and Ffl'2 of the BlP line is A,
8+ if it precedes or is simultaneous with T' of the p-line
This is a circuit composed of a flip-flop and a gate that outputs ``1'' on the `` line, and vice versa, outputs ``1'' on the 6-'' line. The +゛゜1-゛ signal whose direction is not detected by the B, al direction detection circuit 25 is encoded by the Blal encoding circuit 53 as shown in the vertical mode column of Table 1.

Similarly, for B2, the B2a2 counter 34 and the B2
The B2a2 pixel number and direction obtained by the a2 direction detection circuit 26 are encoded by the B2a2 encoding circuit 54.

As described above, AOa,, a, a2, b, al, and B2a2 are encoded by the respective encoding circuits 51, 52, 53, and 54. The comparison circuit 60 compares the number of bits obtained, and here the comparison condition [AOal]+[Ala2]≧
Depending on whether [B, a,] + [B2a2] holds true or not,
Is 11゛ output on the output side line of the comparison circuit 60?
(vertical mode), "1" is output on the h line (horizontal mode).

When the above conditional expression is satisfied and the vertical mode is established, the V line of the comparator circuit 60 becomes "F" and the gates 73 and 74 are opened. The output signal then passes through gate 74 to B
The encoded output signals of the 2a2 encoding circuit 54 are sequentially transmitted to the signal synthesis circuit 90. On the other hand, when the above conditional expression does not hold and the mode is set to horizontal mode, and 0F' is output to the h line of the comparator circuit 60, the gates 71 and 72 are opened. The encoded output signal of the al encoding circuit 51 and the encoded output signal of the Ala2 encoding circuit 52 are sequentially applied to the signal synthesis circuit 90 via gates 71 and 72. Next is pass mode,
This means that the B2P line output of the B2 detection circuit 24 and the Aln line output of the a1 detection circuit 21 are added to the pass mode detection circuit 40, and when a1 is not detected (Aln is ``2''), if B2 is detected (B2p is `` r'), this is determined to be the pass mode, and "1" is output to the output line p of the pass mode encoding circuit 40, thereby causing the pass mode encoding circuit 55 to write the pass mode code FllllO in Table 1. '2 is generated and transmitted to the signal synthesis circuit 90.

The signal synthesis circuit 90 synthesizes the encoded output signals applied from the pass mode encoding circuit 55 and the gates 71 , 72 , 73 , and 74 , converts it into an output signal series, and sends it out from the output line 100 .

When the encoding in the pass mode or vertical or horizontal mode described above is completed, the next new starting pixel A is generated.

It is necessary to configure the settings. Therefore, the B2 address counter 81 receives a pulse from the address control circuit 5. Count the number of pixels from B2 to B2. Also, the A2 address counter 82 is A. Similarly, count the number of pixels from A2 to A2.
Note that these counters 81 and 82 are connected to the address control circuit 5.
So A.

Counting starts when scanning starts from , and the B2 address counter 81 outputs "1" on the B2P line of the B2 detection circuit 24, and the A2 address counter 82 outputs A
Counting is stopped at the output ``1'' of the A2p line of the 2 detection circuit 22, but which of these is selected as the new starting pixel A depends on the mode. In other words, if it is the pass mode, the pass mode detection circuit 40 gate 7 by the P output of
6 is opened and the output of B2 address counter 81 is A.

It is transmitted to the address register 83, and in the vertical or horizontal mode, the gate 75 is opened via the OR circuit 7 by the V or h output ``1'' of the comparator circuit 60, and the output of the A2 address counter 82 is A.Address register 83 It is transmitted to
This A. The information in the address register 83 is added to the address control circuit 5 for this new A. Encoding operation resumes from. Note that the address control circuit 5 has the configuration shown in FIG. 1
The information in line memories 2 and 3 is increased by 43
A of register in 0.

Read one bit at a time from the address. A again. Each time information is received from the address register 83, a new starting pixel is set to A. The data is transmitted to the memory 4 via the encoding line memory 2. This concludes the explanation of the encoding device, but in order to simplify the explanation, in these explanations, the conditions for setting the detection circuits, registers, counters, etc. are not particularly described, and although they are not shown in the figures, there are some important points for these circuits. What you need (b1
Detection circuit 23, B2 detection circuit 24, A, detection circuit 21,
A2 detection circuit 22, counters 81, 82, direction detection circuits 25, 26, counters 31, 32, 33, 34, etc.) are A
.

It is assumed that the value is reset each time the value is newly set. Further, the intermittent operation of the present encoding device is managed by the address control circuit 5, but the operation is always A.

The address is monitored by the address control circuit 5, and when the AO address reaches the end pixel of one line, encoding is stopped, the AO address is newly set to the start pixel of one line, and encoding of the subsequent line is restarted. Next is the decoding operation, which is sequentially performed by the reverse operation of the encoding.

An example of a decoding device is shown in FIG. 5A.

In the figure, 201 is an input terminal, 202 is an input buffer memory,
203 is a mode code identification circuit, 211 is a reference line memory, and 212 is a decoding line memory. 213 is A.

Memories, 221, 222 are address control circuits, 231,
232, 233 and 234 are decoding circuits, 240 are changed pixel detection circuits, 251, 252 are B, detection circuits and B2 detection circuits, respectively, 261, 263, 265 are adders, 262, 264 are subtracters, 271, 272 is a counter, 281, 282, 283, 284, 285, 286
and 287 are gates, 291, 292, 29 respectively
4,295 is an OR circuit, 293 is an exclusive OR circuit (E
OR), 300 is A. A register 310 is an output terminal. Now, the encoded input signal from the input terminal 201 is temporarily stored in the buffer memory 202. The mode code identification circuit 203 has the configuration shown in FIG. Vertical mode v is identified. Now, if this signal is ゞ1110'', it is identified as pass mode and the output of P line is set as ゛1゛゛.If the signal is ゛1111゛, it is recognized as horizontal mode and the output of H line is set as ゛1゛. In vertical mode, if the signal of the first word is either ゞTO'', ゞTlOO'', or 61100'2, the B, al direction is identified as... and the output of the V1+ line is ゞF'. If this signal is 'TlOf' or 110F', the direction of B, al is identified as (d), and the output of the V1 line is set to '1'. Also, regarding the second word, the above Similarly, in this case, the ゞF' signal is output to the V2+ or V2 line in the direction of B2a2.

The identification of the first word Blal first and the second word B2a2 later is performed by the operation of the flip-flop and two gates shown in FIG. 5B.

The address control circuit 221 has a configuration shown in FIG.
-, and A added by SaO when either V2+ or V2- becomes "1".

A pulse is applied to the reference line memory 211 to shift the memory contents one bit at a time starting at address 300. By the way, when the P line card F' of the identification circuit 203 is selected (that is, in the pass mode), the address control circuit 221
. The contents of the reference line memory 211 are sequentially shifted from the address , and detection of B, , b2 is started. Note that information on the previous line is stored in advance in the reference line memory 211 via the encoding line memory 212. The changed pixel detection circuit 240 has the same configuration as that in FIG. 4B described above, and outputs an output signal every time there is a pixel different from the previous pixel in the signal series added from the reference line memory 211.

When the output of 240 is "1", the pixel that changes is A. If the polarity is different from that, the output "1" is applied to B and the detection circuit 251 (AND circuit) via the EOR circuit 293, and the output of the BlP line becomes 1F. The AObl counter 272 receives a pulse from the address control circuit 221 and
Count the number of pixels from O to B. Further, after b1 is detected by the b1 detection circuit 251, the change pixel detection circuit 251 further detects b1.
If the next changed pixel is detected in step 40, the B2 detection circuit 25
2 assumes that the output of the B2P line is 1. This circuit 252 is composed of a flip-flop and an AND circuit.
Next is A.

The b2 counter 271 receives a pulse A from the address control circuit 221. Count the number of pixels from B2 to B2. Furthermore, the address control circuit 221 temporarily stops sending out the shift pulse due to the output 'F' of the 2P line. AOb2 counter 2
The information of A.

It is added to register 300. Next, when the V1+ or V1 line of the mode code identification circuit 203 becomes ``1'' (first word of vertical mode), the output of the OR circuit 291 ゛TF
' is the address control circuit 221 and the Bral decoding circuit 23
Join 1.

As a result, the above-mentioned decoding regarding b1 is executed.
The count of the bl counter 272 is A of b1. This will indicate the address for. In addition, the Blal decoding circuit 231
reads out one word worth of signals from the input buffer memory 202 and decodes them.

This decoded value is sent to A by the adder 261. A is added to the value of the bl counter 272 and is also added to the value of the bl counter 272 by the subtracter 262.
b, is subtracted from the value of the counter 272. When the output V1+ of the mode code identification circuit 203 is 1, the gate 284
is opened and the information from the adder 261 is applied to the address control circuit 222 via the OR circuit 294.

On the other hand, the output V1- of the mode code identification circuit 203 is ゛F'
At this time, the gate 285 is opened and the information from the subtracter 262 is applied to the address control circuit 222 via the OR circuit 294. Similarly, for the second word in the vertical mode, depending on V2+ or V2-, the output 1F' of the OR circuit 292 is applied to the address control circuit 221 and the B2a2 decoding circuit 232, thereby starting the decoding of B2. The count of the AOb2 counter 271 is A of B2.

This will indicate the address for. Further, the B2a2 decoding circuit 232 reads out the next one word worth of signals from the input buffer memory 202 and decodes them. This decoded value is converted to A by the adder 263. A is added to the value of the b2 counter 271, and is also added to the value of the b2 counter 271 by the subtracter 264. bl counter 27
It is subtracted from the value of 1. When the output V2 of the mode code identification circuit 203 + 1°, the gate 286 opens and the information from the adder 263 is applied to the address control circuit 222 via the OR circuit 295. A through 6F° (opened at output). It is also added to the register 300. Similarly, if the output V2 of the mode code identification circuit 203 is "r", the gate 287
is opened, and the information of the subtracter 264 is applied to the address control circuit 222 via the OR circuit 295 and the information of the subtracter 264 is applied to the address control circuit 222 via the OR circuit 295.
via A.

It is also added to the register 300. The address control circuit 222 has the configuration shown in FIG.

All the information from A to just before A. and A,
The information is A. At the same time, the address of A2 is determined using the information transmitted via the OR circuit 295, and all the information from A on the decoding line memory 212 to just before A2 is made to be the same as A. , and the information of A2 is inverted with respect to the information of a1. Next, when the h line of the mode code identification circuit 203 becomes 1F" (horizontal mode)
, AOa, decoding circuit 233 and Ala2 decoding circuit 23
4 sequentially reads two words worth of signals from the input buffer memory 202 and reads the first word A.

a. It is decoded by the decoding circuit 233, and its output is applied to the address control circuit 222. The next word is decoded by the Ala2 decoding circuit 234, and the values of these two decoded words are added by the adder 265 and then applied to the address control circuit 222. It is also added to the A. register 300 via the A. A.

A for all pixels from to just before a1. After inverting a1, all the information from a1 to just before A2 is made the same as a1, and the information in A2 is inverted with respect to the information in a1. AO register 300 is A2 or B
2 addresses one after another, and the A2 or B2 address is the new A.

It becomes the address. This new information is stored in address control circuit 2.
A newly added to 21,222. Set the address and restart decoding. Note that the output of the address control circuit 222 is transmitted to the decoding line memory 212 and output from the output terminal 310.

In the decoding device described above, the conditions for setting the detection circuits, registers, counters, etc. are not described, nor are they shown in the diagram, but the necessary circuits (decoding circuits 231, 232, 233, 234, counter 271
, 272, adders 261, 263, 265, subtracter 26
2, 263, detection circuits 251, 252, etc.) is A.

It shall be reset each time a new address is established. Also, the end of one line is A. by monitoring the address by the address control circuit 222;
When the address of AO becomes the address of the end pixel of one line, decoding is terminated and encoding of the subsequent line is restarted. In the embodiment described above, in order to improve the encoding efficiency of the information source, the horizontal or vertical mode was selected by comparing the , and two changing pixels were always encoded as a pair. First, we compare [AOal] and [B, al] and write [AOa,] [Blal]...
When the condition a) is satisfied, the above-mentioned \1υ11/
- \111t/ 1\1171/? \1 Otsu 1 Otsu/ Depending on whether the condition of \5' is met or not,
It is conceivable to select either horizontal mode or vertical mode and encode two changed pixels.

In this case, if the conditions of [AOal] and [Blal] are not satisfied, naturally only [Blal] is encoded and output, and a1 is set as the new starting pixel A.

shall be. In these cases, the selection criteria for each mode becomes more strict, so that the encoding efficiency is further improved than in the above-mentioned cases. An example of this case will be described below.

In FIG. 6, the pixel is moved to position A2. When this holds true, the mode is set to horizontal and the distance is A.

Encode al, A, and a2 as a pair, and set the new starting pixel as A.
Move to position 2. Next, the cases shown in FIGS. 6A, B, and C will be explained.

In addition, in this explanation, is called the first conditional expression. will be called the second conditional expression.

In the example of Figure 6A, from Table 1 Therefore, the first conditional expression (a) does not hold.

Therefore, in this case, the vertical mode is set and [Blal] is used as the encoded output, resulting in TllOlF'. Next, in FIG. 6B, the first conditional expression (a) is similarly satisfied, but since The second conditional expression (6) does not hold.

Therefore, in this example, vertical mode is selected and adopted [Bla
l]+[B2a2] as the encoded output, so 110F
"and 8100" are paired and used as encoded output. Also the 6th
In Figure C, the first conditional expression (a) is satisfied at \-1-1'.

Next (Ulal no I (U2QZ no 1 ν-1 L −/IJ
-1r equation (6) also holds, so in horizontal mode [AO
The encoded outputs of a, ] and [Albl] are each "1"
1111000'2 and FtOll''.

In the above explanation, when [AOal]<[B,al] holds, [AOal]+[Ala2]<[Blal]+[
B2a2] was selected depending on whether or not it holds, but this conditional expression may be, for example, as in the case of the previous embodiment, or the distance A before encoding. . al, ala2, blal9b2a2 may also be used.

It is also possible to use codes other than MH codes and D(n) codes.

Next, regarding the circuit configuration for realizing this embodiment, on the encoding device side, in addition to the comparison circuit 60 in FIG. 4A, as shown in FIG. Bla
When this condition is not satisfied, the comparison circuit 61 of [B
In order to encode the vertical mode as vertical mode, it is necessary to make some changes to the circuit configuration, such as adding an a1 address counter 84 and a gate 78.

In addition, on the decoding device side, the mode code identification circuit 203 and the like are slightly changed as shown in FIG. 8 in the same manner as in FIG. Although it is necessary to change the circuit such as adding a subtracter 266 and a gate 288 in order to achieve this, detailed explanation will be omitted here since it is thought that the explanation up to now and the prior art can be sufficiently understood.

Next, a method of limiting the influence of deterioration of the image quality of a reproduced screen due to a code error to a small range in the present invention will be described.

In the encoding method of the present invention, in order to encode the image signal of the encoded line, the image signal information of the reference line immediately before the encoded line is used to encode the encoded line.

Therefore, on the decoding device side as well, the image signal of the decoded line is decoded using the image signal information of the reference line that has already been decoded. In this way, since encoding and decoding are performed while sequentially using the image signal information of the immediately preceding scanning line, coding errors may occur due to the influence of line noise, and the image signal of a certain line may not be reproduced correctly. , the image signals of lines subsequent to this line may not be reproduced correctly, and the image quality of the reproduced screen may deteriorate significantly. Therefore, it is possible to detect the occurrence of a code error, suppress the deterioration of the image quality of the line where the code error has occurred, and promptly recover from the code error state so that the deterioration of image quality due to the code error does not spread beyond the line. It becomes necessary. In the present invention, for this purpose, the encoding device side generates a so-called self-synchronized first control code that can be detected from any position in the code sequence in a predetermined section of the image signal, for example, as shown in FIG. 4 lines (K
-4) is inserted immediately before the start of encoding of the first black line, and the black line is encoded using only the image signal information of the black line without using the image signal information of the immediately previous line. (e.g. run-length RL encoding),
For the black K scanning line immediately after the line 2, 3, etc., two-dimensional sequential encoding according to the present invention is performed, and the black 2
- A second control code different from the first control code for code error detection is inserted immediately before the encoded signal of the black K line.

Next, on the decoding device side, when the self-synchronized first control code is detected, the immediately following code sequence is assumed to have been RL encoded, and is decoded as one black line without using the information of the immediately preceding line. Let's do it. When the second control code is detected, it is assumed that encoding according to the present invention has been performed, and decoding is performed using the immediately preceding line information. Immediately after decoding of each line is completed, the presence or absence of the first or second control code is checked,
Make an incorrect retrieval. If an error is detected, processing such as replacing the decoded line with the image signal of the immediately previous scanning line is performed to suppress deterioration in image quality. When an error is detected, the decoding operation is temporarily stopped, but as soon as the self-synchronized first control code is detected, RL decoding is started to recover from the error state. FIG. 10 is a block diagram of an encoding device according to an embodiment of the present invention based on such a principle, and FIG. 11 is a block diagram of a decoding device corresponding thereto.

In FIG. 10, the image signal input line 1 of the facsimile is connected to the RL encoder 102 every K lines via a switch 101a under the control of a switch control circuit 101.

At this time, the first control code generation circuit 104 generates a first control code, and the RL encoder 102 performs RL encoding on the line (1 line). When this encoding is completed, the switch 101a is connected to a two-dimensional sequential encoder 103 according to the present invention as shown in FIG. A second control code is inserted by the second control code generation circuit 105 immediately before the encoded signal of the line. On the decoding device side shown in FIG.
When the first control code is detected by the control code detection circuit 106,
Thereafter, the RL decoder 107 performs RL decoding for one line (1 line), writes reproduced pixel information to the line memory 1 river 08, and when the decoding of the 1 black line is completed, the contents of the line memory 108 are written to the line memory 109. Forward.

From then on, the contents of the line memo I month 09 become the reference line information, and the decoder 110 as shown in FIG. Let's do it. Note that each time the decoding of each line is completed, the control code is detected by control code detection circuits 106 and 111, and the code error detection circuit 112 detects whether or not a code error has occurred. Once a code error occurs, black K
Decoding is not performed up to the scanning line, and when the first control code is detected thereafter, normal decoding operation is started to recover from the code error state. As explained in detail above, the present invention enables highly efficient encoding of signals with extremely strong correlation between adjacent lines, such as black-and-white binary facsimile signals, by using the distance from the changing pixels in the vicinity to write documents. As mentioned above, by appropriately selecting two types of encoding methods, in which parts that have no correlation with the line directly above are encoded using the distance from the same line, highly efficient encoding can be achieved regardless of the degree of correlation. This method has advantages such as improved encoding efficiency, reduced transmission time, and reduced amount of memory for storing or processing information compared to the previous application proposed earlier. Also, for example, K
After inserting a self-synchronous first control code for each scanning line,
By performing run-length encoding for one scanning line, encoding the subsequent scanning lines according to the present invention, and checking for code errors each time the encoding of one scanning line is completed,
This has the advantage of preventing the spread of image quality deterioration due to code errors and quickly recovering from the code error state.

[Brief explanation of drawings]

Figures 1, 2, 3 A, BL, 6 A, B, C, and 9 are examples of facsimile signals for explaining the principle of the present invention, and Figures 4 A and 7 are examples of facsimile signals. Block diagrams showing an embodiment of the present invention, FIGS. 4B, C, and D are similar to FIGS. 4A and 7.
5A and 8 are block diagrams showing specific examples of circuits used in the embodiments shown in the figure, and FIGS. FIGS. 5B, C, and D are block diagrams showing specific examples of circuits used in the decoding devices shown in FIGS. 5A and 8, and FIGS. 10 and 11 are block diagrams showing other embodiments of the present invention. FIG. 2 is a block diagram showing an example of a decoding device corresponding to this embodiment.

Claims (1)

[Claims] 1. A binary facsimile signal in which signals obtained by scanning an original image are sequentially sampled into pixels is input, and the position of the pixel whose information changes from one binary signal value to the other is encoded and output. A first step of setting a starting pixel that is the starting point of the encoding on the encoding scanning line to be encoded, and a first information change sequentially located next to the starting pixel on the encoding scanning line. a second process of detecting a pixel and a second information change pixel, and a signal located after a pixel directly above the starting pixel on a reference scanning line which is a scanning line immediately before the encoding scanning line and different from the starting pixel; a third step of detecting a first reference pixel that is a first information change pixel having a value and a second reference pixel that is a next information change pixel after the first reference pixel; a fourth step in which a state is detected as a first mode when is detected at a distance of n (n is an integer) or more pixels from the pixel directly above the first information change pixel, and the second reference pixel is detected as a first mode; A fifth mode that detects this state as not being in the first mode when it is not detected at a distance of n pixels or more from the pixel immediately above the first information change pixel.
and between the origin pixel and the first information change pixel and between the first information change pixel and the second information change pixel when the mode is detected as not being in the first mode. The first correlation is compared with the second correlation between the first information change pixel and the first reference pixel and between the second information change pixel and the second reference pixel. a sixth step of encoding the presence of the first reference pixel and the second reference pixel as the first mode when the first mode is detected; a seventh step of setting a pixel immediately below the second reference pixel as a starting point pixel, and a seventh step of setting a pixel immediately below the second reference pixel as a starting point pixel; and a seventh step of setting a pixel immediately below the second reference pixel as a starting point pixel; A second method that encodes the distance and the distance between the first information change pixel and the second information change pixel as a second mode, and sets the second information change pixel as a starting pixel in the first process. 8, and when the first correlation is weaker than the second correlation, the first correlation
The distance between the information changing pixel and the first reference pixel and the distance between the second information changing pixel and the second reference pixel are encoded as a third mode, and the starting point pixel in the first process is encoded. a ninth step of setting the second information change pixel as A two-dimensional sequential encoding method comprising: 2 In a method in which a binary facsimile signal in which signals obtained by scanning an original image are sequentially sampled into pixels is input, the position of the information changing pixel that changes from one of the binary signal values to the other is encoded and output. a first step of setting a starting pixel that is the starting point of the encoding on the exponent encoding scanning line; and a first information change pixel and second information sequentially located next to the starting pixel on the encoding scanning line. a second step of detecting a changed pixel, and first information located after a pixel immediately above the starting pixel on a reference scanning line, which is a scanning line immediately before the encoding scanning line, and having a signal value different from that of the starting pixel. a third step of detecting a first reference pixel that is a changed pixel and a second reference pixel that is an information changed pixel next to the first reference pixel; a fourth step of detecting this state as a first mode when the pixel immediately above the changed pixel is detected at a distance of n pixels or more (n is an integer), and the second reference pixel detects the first information change. If the pixel is not detected at a distance of n pixels or more from the pixel immediately above the pixel, this state is detected as not being in the first mode.
and between the origin pixel and the first information change pixel and between the first information change pixel and the second information change pixel when the mode is detected as not being in the first mode. The first correlation is compared with the second correlation between the first information change pixel and the first reference pixel and between the second information change pixel and the second reference pixel. a sixth step of encoding the presence of the first reference pixel and the second reference pixel as the first mode when the first mode is detected; a seventh step of setting a pixel immediately below the second reference pixel as a starting point pixel, and a seventh step of setting a pixel immediately below the second reference pixel as a starting point pixel; and a seventh step of setting a pixel immediately below the second reference pixel as a starting point pixel; A second method that encodes the distance and the distance between the first information change pixel and the second information change pixel as a second mode, and sets the second information change pixel as a starting pixel in the first process. 8, and when the first correlation is weaker than the second correlation, the first
The distance between the information changing pixel and the first reference pixel and the distance between the second information changing pixel and the second reference pixel are encoded as a third mode, and the starting point pixel in the first process is encoded. a ninth step of setting the second information change pixel as a pixel; and when the number of encoded scanning lines reaches a preset number, the secondary encoding operation is temporarily stopped and the next encoding is performed. A tenth step of encoding the position of the information changing pixel for only the scanning line without referring to the position of the information changing pixel of other scanning lines, the seventh step, and the eighth step.
A two-dimensional sequential encoding method, comprising: a step of combining the encoded outputs of the ninth step and the tenth step and transmitting the combined result. 3 In a method in which a binary facsimile signal in which signals obtained by scanning an original image are sequentially sampled into pixels is input, the position of the information changing pixel that changes from one of the binary signal values to the other is encoded and output. a first step of setting a starting pixel that is the starting point of the encoding on the exponent encoding scanning line; and a first information change pixel and second information sequentially located next to the starting pixel on the encoding scanning line. a second step of detecting a changed pixel, and first information located after a pixel directly above the starting pixel on a reference scanning line, which is the immediately previous scanning line on the encoding scanning line, and having a signal value different from that of the starting pixel. a third step of detecting a first reference pixel that is a changed pixel and a second reference pixel that is an information changed pixel next to the first reference pixel; a fourth step of detecting this state as a first mode when the pixel immediately above the changed pixel is detected at a distance of n pixels or more (n is an integer), and the second reference pixel detects the first information change. a fifth step of detecting this state as not being in the first mode when the pixel is not detected at a distance of n pixels or more from the pixel immediately above the pixel; and a fifth step of detecting the state as not being in the first mode; a sixth step of comparing a first correlation between one information change pixel and a second correlation between the first information change pixel and the first reference pixel; When a mode is detected, the presence of the first reference pixel and the second reference pixel is encoded as the first mode, and the pixel immediately below the second reference pixel is used as the starting pixel in the first process. 7th to set the pixel of
and when the first correlation is weaker than the second correlation, the distance between the first information change pixel and the first reference pixel is encoded as a third mode, and the first correlation is
an eighth step of setting the first information change pixel as a starting point pixel in the process;
When it is detected that the correlation is stronger than the correlation between the origin pixel and the first information change pixel and between the first information change pixel and the second information change pixel, and a fourth correlation between the first information change pixel and the first reference pixel and between the second information change pixel and the second reference pixel. process and
When the third correlation is stronger than the fourth correlation, the distance between the origin pixel and the first information change pixel and the distance between the first information change pixel and the second information change pixel are a tenth step in which the second information change pixel is encoded as the second mode and the second information change pixel is set as the starting point pixel in the first step; The distance between one information change pixel and the first reference pixel and the distance between the second information change pixel and the second reference pixel are encoded as the third mode, and in the first process. an eleventh step of setting the second information change pixel as a starting pixel;
a twelfth process of combining and transmitting the encoded outputs of the seventh process, the eighth process, the tenth process, and the eleventh process; Encoding method. 4 In a method in which a binary facsimile signal in which signals obtained by scanning an original image are sequentially sampled into pixels is input, the position of the information changing pixel that changes from one binary signal value to the other is encoded and output. a first step of setting a starting pixel that is the starting point of the encoding on the exponent encoding scanning line; and a first information change pixel and second information sequentially located next to the starting pixel on the encoding scanning line. a second step of detecting a changed pixel, and first information located after a pixel immediately above the starting pixel on a reference scanning line, which is a scanning line immediately before the encoding scanning line, and having a signal value different from that of the starting pixel. a third step of detecting a first reference pixel that is a changed pixel and a second reference pixel that is an information changed pixel next to the first reference pixel; a fourth step of detecting this state as a first mode when the pixel immediately above the changed pixel is detected at a distance of n pixels or more (n is an integer), and the second reference pixel detects the first information change. The fifth mode detects this state as not being in the first mode when the pixel is not detected at a distance of n pixels or more from the pixel directly above the pixel.
a first correlation between the origin pixel and the first information change pixel when detected as not being in the first mode, and a first correlation between the first information change pixel and the first reference pixel. a sixth step of comparing the presence of the first reference pixel and the second reference pixel to the first mode when the first mode is detected; a seventh step in which the pixel immediately below the second reference pixel is encoded as the starting pixel in the first step; and when the first correlation is weaker than the second correlation, an eighth step of encoding the distance between one information change pixel and the first reference pixel as a third mode and setting the first information change pixel as a starting pixel in the first process; When it is detected that the first correlation is stronger than the second correlation, new information is created between the origin pixel and the first information change pixel, and between the first information change pixel and the second information change pixel. The third pixel between the changed pixel and
and a fourth correlation between the first information change pixel and the first reference pixel and between the second information change pixel and the second reference pixel. process, and when the third correlation is stronger than the fourth correlation, the distance between the origin pixel and the first information change pixel and the first
a tenth step of encoding the distance between the information change pixel and the second information change pixel as a second mode and setting the second information change pixel as the starting pixel in the first step; When the third correlation is weaker than the fourth correlation, the distance between the first information change pixel and the first reference pixel and the distance between the second information change pixel and the second reference pixel. an eleventh step in which the second information change pixel is encoded as the third mode and the second information change pixel is set as the starting pixel in the first step, and the number of encoded scanning lines reaches a preset number. When this happens, the above-mentioned two-dimensional encoding operation is temporarily stopped and the position of the information-changing pixel is encoded for the next encoding scan line without referring to the position of the information-changing pixel of the other scan lines. and a thirteenth step of combining and transmitting each encoded output from the seventh step, the eighth step, the tenth step, the eleventh step, and the twelfth step. A two-dimensional sequential encoding method.