JPH06245086A - Encoding and decoding method - Google Patents

Abstract

PURPOSE:To easily cipher encoded code data by repeatedly performing a repetitive encoding processing until the number of times including a first encoding processing reaches a prescribed number. CONSTITUTION:First, picture data PIX 1 are encoded and the encoded data FDC 1 of a prescribed data form are formed. Then, a second encoding processing is performed by considering the FDC 1 as the picture data and the code, data obtained as the result are gathered as the encoded data FDC 2 of the prescribed data form. Also, at the time of encoding the FDC 1, the respective byte data are considered as the picture data of one line and the encoding processing is performed. Then, similarly, a third encoding processing is performed and the encoded data FDC 3 are formed. This is successively repeated, the encoding processing is performed for (m) times including the first encoding processing and the encoded data FDCm obtained finally are outputted as the encoded data of the picture data PIX 1 at the time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding / decoding method for coding a symbol sequence by an arithmetic code.

[0002]

2. Description of the Related Art For example, as an encoding method for compressing the information amount of an image signal obtained by raster scanning an original,
The MH code adopted as the standard coding method of the group 3 facsimile machine, the MR code adopted as the option coding method, and the MMR code adopted as the standard coding method of the group 4 facsimile machine are widely used. Although used, a coding method with good coding efficiency has been proposed other than the standard coding method.

For example, JPEG (Joint Photo)
The image data is encoded by using the arithmetic code like the QM-coder adopted in the entropy coding method of the color still image (natural image) coding method for which the international standardization work is being carried out in the (Graphics Experts Group). Things have been proposed.

[0004]

However, in such a conventional method, since the well-known standard encoding method is used in any case, the following disadvantages occur.

That is, for example, if the transmission data of a facsimile machine is wiretapped, it is easy to decode the transmission data, which may cause the inconvenience that the original image is known to others. there were.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an encoding / decoding method capable of easily encoding encoded code data.

[0007]

According to the present invention, in a coding / decoding method for coding a symbol sequence by arithmetic code, the symbol sequence is coded at the time of coding, and the code string obtained thereby is coded again. Coding process, the coding sequence obtained by this coding process is coded again, and this repetitive coding process is repeatedly executed until the number of times including the first coding process reaches a predetermined number. The data is decrypted, the resulting data string is decrypted again, and this iterative decryption process is repeated until the number of times including the initial decryption process reaches the above specified number, and finally The obtained data string is output as the original symbol series.

Further, in a coding / decoding method for coding a symbol series by an arithmetic code, at the time of coding, the symbol series is coded, the code string obtained thereby is coded again, and this coding processing is performed. The code string obtained by is re-encoded, and this repetitive encoding process is repeatedly executed until the number of times including the first encoding process reaches a predetermined number, and the code data is generated for each code data. When decoding, including the coding parameters used in the coding process, the coded data is decoded, the resulting data string is decoded again, and this iterative decoding process is the first decoding process. Are repeatedly executed until the number of times including the above reaches the above predetermined number, and the finally obtained data string is output as the original symbol sequence, and in each decoding process, With reference to the encoding parameters included in the data string to be processed decoded can it is obtained so as to apply a decoding process to the data string of the portion excluding the coding parameters.

Further, in the coding / decoding method of coding a symbol sequence by arithmetic code, at the time of coding, the symbol sequence is coded, the code string obtained thereby is coded again, and this coding process is performed. The code string obtained by is re-encoded, and this repetitive encoding process is repeatedly executed until the number of times including the first encoding process reaches a predetermined number, and finally the encoded data is Including the encoding parameter data in which a plurality of encoding parameters applied at the time of encoding processing are arranged according to the order of the encoding processing, at the time of decoding, the encoded data is subjected to the decoding processing, and the obtained data string is obtained. The decoding process is performed again, and this iterative decoding process is repeatedly executed until the number of times including the first decoding process reaches the above predetermined number, and the finally obtained data string is converted into the original symbol. In addition to outputting as a series, in the first decoding process, the above-mentioned coding parameter data included in the coded data is extracted and the corresponding coding parameter of the coding parameter data is used to convert the coding parameter data. The coding process is applied to the removed part, and the coding parameters corresponding to the above coding parameters are applied in the second and subsequent coding processes.

Further, in the coding / decoding method for coding a symbol sequence by arithmetic code, at the time of coding, the symbol sequence is coded, the code string obtained thereby is coded again, and this coding process is performed. The code string obtained by the above is encoded again, and this repetitive encoding processing is repeatedly executed until the number of times including the first encoding processing reaches a predetermined number, and in the encoding processing other than the final encoding processing, A predetermined number of dummy data is added to the code data obtained after the encoding process, and when decoding, the code data is decoded, the data string obtained thereby is decoded again, and this iterative decoding process is performed. , Repeatedly executed until the number of times including the first decoding process reaches the above predetermined number, outputting the finally obtained data string as the original symbol sequence, and The issue process, after removing a predetermined number of dummy data from the decoded data is obtained by so applying the decoding process.

[0011]

Therefore, the number of repetitions of the encoding process, etc.
If the specific contents of the encoding method are not known, the encoded data cannot be properly decoded, and therefore the information can be kept secret.

[0012]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows a group 3 facsimile apparatus according to an embodiment of the present invention.

In FIG. 1, a control unit 1 performs control processing of each unit of the facsimile apparatus and facsimile transmission control procedure processing, and the system memory 2 is
The control unit 1 stores a control processing program executed by the control unit 1 and various data necessary for executing the processing program, and constitutes a work area of the control unit 1. The parameter memory 3 is a group memory. It is for storing various information unique to the facsimile machine.

The scanner 4 is for reading an original image at a predetermined resolution, the plotter 5 is for recording and outputting an image at a predetermined resolution, and the operation display unit 6 is a facsimile device. For operation,
It consists of various operation keys and various indicators.

The encoding / decoding unit 7 is, for example, QM-co
The encoding table storage unit 8 is for encoding and compressing the image signal by the der encoding method and for decoding the encoded and compressed image information into the original image signal.
Is for storing an encoding table that the encoding / decoding unit 7 refers to at the time of encoding / decoding, and the image storage device 9 is for storing a large number of image information in an encoded and compressed state. It is a thing.

The group 3 facsimile modem 10 is for realizing the modem function of the group 3 facsimile, and is a low speed modem function (V.21 modem) for exchanging transmission procedure signals and mainly exchanging image information. High-speed modem function (V.29 modem,
V. It is equipped with a modem such as 27ter.

The network control device 11 is for connecting this facsimile device to a public telephone line network and has an automatic call originating / receiving function.

These control unit 1, system memory 2,
Parameter memory 3, scanner 4, plotter 5, operation display unit 6, encoding / decoding unit 7, image storage device 9, group 3 facsimile modem 10, and network control device 11
Are connected to the system bus 12, and data is exchanged between these respective elements mainly via the system bus 12.

Data is exchanged directly between the network control device 11 and the group 3 facsimile modem 10.

Here, the arithmetic code which is the basis of the QM-coder coding method will be described. The arithmetic code is a corresponding section (binary decimal [0.0 ... 0,0.1 ... 1)) on the number line of 0 or more and less than 1 ([0,1)) depending on the occurrence probability of each symbol. To divide the coordinates of points included in the section obtained by recursively repeating the division by allocating the target symbol series to the corresponding subsections, and at least distinguishing it from other sections. It is represented by a possible binary decimal number and used as it is as a code.

For example, in binary arithmetic coding for the coded symbol sequence 0100, coding as shown in FIG. 2 is performed.

In the figure, for example, when encoding the first symbol, the entire section is divided into A (0) and A (1) according to the ratio of the occurrence probabilities of the symbols of 0 and 1, and the section is generated by the occurrence of 0. A (0) is selected. Next, when encoding the second symbol, A (0) is further divided by the occurrence probability ratio of both symbols in that state, and A (01) is selected as the section corresponding to the generated symbol sequence. Encoding is advanced by repeating the processing of such division and selection.

This arithmetic code is a so-called non-block code, and is particularly suitable for coding in the case where the symbol appearance probability changes according to the state number (context) as in the predictive coding method. Compared to a run-length code such as a code, there are advantages that the hardware such as the scale of the encoder and the required memory amount can be small, higher efficiency can be expected, and the applied coding is easy.

The above-mentioned QM-coder realizes this arithmetic coding by using less hardware resources and enables higher speed processing. Note that, normally, the image data is not directly arithmetically coded, but a preprocessing is performed by the predictive coding process to determine whether each pixel of the image data is the inferior symbol or the dominant symbol.

The encoding / decoding algorithm of QM-coder will be described.

At the beginning of encoding, consider a number line of 0 or more and less than 1. When the interval of this number line is A and the probability of occurrence of the inferior symbol corresponding to the Markov state (state 0 in the initial state) at that time is Qe, the area after division is represented by the following equation (1).

A = A × (1−Qe) (a: size of area of dominant symbol)

B = A × Qe (b: size of area of inferior symbol) (1)

Here, if the first symbol is 0 (dominant symbol), a is a new A, and if it is 1 (inferior symbol), b is a new A and further division is performed. The encoding table stores the relationship between the state number of the Markov state and the probability Qe, information for state transition when renormalization processing occurs (described later), and the like.

However, performing the multiplication operation at the time of encoding is disadvantageous in terms of the scale of the apparatus and the operation speed. Further, when encoding a symbol sequence of infinite length, an arithmetic register of infinite length is required to compute a reduced area.

Therefore, in the QM-coder, the new A after division is always manipulated so as to have a size of 0.75 or more and less than 1.5 so that A can be approximated to 1, and the above equation (1 ) Is approximated by the following equation (2).

A = A-Qe

B = Qe (2)

In accordance with this approximation, when the value of A becomes less than 0.75, the renormalization processing in which A is bit-shifted to the left and enlarged until A becomes a value of 0.75 or more and less than 1.5 Do. By this renormalization process, an operation that requires multiplication can be realized by subtraction, and an operation can be performed using a finite length register. When the renormalization process is performed, the state shifts to the next Markov state according to the Markov state at that time and the superiority / inferiority of the symbol to be processed.

The coding process of the dominant symbol is performed as shown in FIG. 3 (a), and the coding process of the inferior symbol is performed as shown in FIG. 3 (b). Here, C represents a code, and its initial value is 0.

That is, when the dominant symbol is encoded, the code C is not changed (process 101), and the value of the area A is updated to a value smaller by the probability Qe corresponding to the Markov state at that time (process 102). At this time, it is checked whether or not the value of the area A is smaller than 0.75 (decision 10
3) When the result of determination 103 is YES, the value of the area A and the code C are renormalized and the state is changed (step 104), and the processing of one dominant symbol is ended. When the result of determination 103 is NO,
The process 104 is not performed, and the Markov state at that time is maintained.

When the inferior symbol is coded, the value of the code C is increased by (A-Qe) (process 20).
1) update the value of region A to the value of probability Qe (Process 20
2) The area A and the code C are renormalized and the state is changed (step 203).

The code C generated at this time coincides with the binary decimal value indicating the lowermost part of the area. In the renormalization process, the code C is shifted to the left by the same number of digits as in the area A and expanded, and the value of the code C exceeding 1 is output as code data.

An example of the decoding process is shown in FIG. 3 (c).

First, it is checked whether or not the code C is smaller than the value (A-Qe) (decision 301). When the result of the decision 301 is YES, the pixel of interest to be decoded is set as the dominant symbol. A determination is made (process 302), and the value of the area A is updated to a value reduced by the probability Qe corresponding to the Markov state at that time (process 303). Then, it is checked whether or not the updated value of the area A becomes smaller than 0.75 (decision 304). When the result of the judgment 304 is YES, the area A and the code C are renormalized and the Markov state is changed. After the transition (process 305), the decoding process for this one symbol ends. When the result of determination 304 is NO, the process 305 is not performed and the Markov state at that time is maintained.

When the result of judgment 301 is NO, the pixel of interest is judged to be an inferior symbol (process 30).
6) The value of the code C is updated to a value smaller by (A-Qe) (process 307), the area A is updated to the value of the probability Qe (process 308), and the areas A and C are renormalized. With this, the Markov state is changed (process 309), and this 1
The decoding process for one symbol ends.

In this way, when the QM-coder is coded, the code C does not change when the dominant symbol appears, the renormalization process is unlikely to be performed, and the inferior symbol appears immediately. Renormalization processing is performed and code data is formed.

Therefore, if the predictive coding process, which is a preprocess, is performed so that the frequency of appearance of the inferior symbols is reduced, the coding efficiency is improved and the processing speed is also improved.

The coded data thus coded is output as coded data in the data format of the format shown in FIG. 4 (a).

This coded data has a marker code prefix MCP consisting of a predetermined bit pattern at the beginning, a marker code SOI indicating the beginning of an image (data), and a line number data L indicating the number of lines of the image.
N, code data, marker code prefix MCP, and marker code E indicating the end of the image
It consists of OI.

Now, in this embodiment, the QM-coder
The encoded data encoded by is encrypted by the following method.

That is, as shown in FIG. 5, first, the image data PIX1 to be encoded is encoded to form the encoded data FDC1 in the above-mentioned data format. Next, the encoded data FDC1 is regarded as image data, the second encoding process is executed, and the encoded data obtained as a result of the encoding process is put together into the encoded data FDC2 in the above-mentioned data format.

When the encoded data FDC1 is encoded, each byte data is regarded as one line of image data and the encoding process is executed. That is, in this case, the number of pixels per line (that is, the number of bits) when the encoded data FDC1 is regarded as image data.
Is set to 8 pixels (= 8 bits). Therefore,
In this case, as the value of the line number data LN included in the encoded data FDC2, the number of bytes of the encoded data FDC1 that is the encoding target at that time is set.

Next, similarly, the encoded data FDC2
Is regarded as image data, the third encoding process is executed to form the encoded data FDC3, which is sequentially and repeatedly executed to execute the mth encoding process including the first encoding process. The finally obtained coded data FDCm is output as the coded data of the image data PIX1 at that time.

An example of the encoding process in this case is shown in FIG.
Shown in (a) and (b).

First, the number of pixels in the main scanning direction and the number of lines of image data to be encoded are set in the encoding / decoding unit 7 as the main scanning size and the sub-scanning size (process 401), and the variable NC is set. Then, the value of the number of repetitions of the encoding process at that time is set, and the value of the counter i for storing the number of repetitions of the encoding process is initialized to 0 (process 402).

Then, one bit of the image data to be encoded is extracted and transferred to the encoding / decoding unit 7 (process 403),
The encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic encoding process (process 404), and when the encoding / decoding unit 7 outputs the encoded data at that time, the encoded data is output to a predetermined buffer ( Process 405).

Next, it is checked whether or not the image data has ended (decision 406). When the result of the determination 406 is NO, the process returns to step 403 and the remaining image data is encoded. When the result of determination 406 is YES, the value of the counter i is incremented by 1 (process 40).
7) Then, the code data accumulated in the buffer at that time is converted into the coded data of the above-mentioned format (process 408).

Next, the sub-scanning size used as a condition for the next encoding is calculated (process 409). In this case, the number of bytes of the encoded data after formatting is calculated (rounded up), and the value is used as the value of the sub-scanning size.

After the main scanning size is set to 8 and the sub-scanning size is set to the value calculated in step 409 in the encoding / decoding unit 7 (step 410), 1 bit of encoded data is taken out from the buffer and encoded. The data is transferred to the encoding / decoding unit 7 (process 411) and the encoding / decoding unit 7 is caused to execute the arithmetic encoding process described above (process 412). At that time, encoded data is output from the encoding / decoding unit 7. Sometimes, the coded data is output to a predetermined buffer different from the coded data to be coded (process 413).

Next, it is checked whether or not the coded data to be coded is completed (decision 414), and the decision 4
When the result of 14 is NO, the process returns to the process 411 and the remaining encoded data is encoded. When the result of the judgment 414 is YES, the value of the counter i is incremented by 1 (process 415) and the code data accumulated in the buffer at that time is converted into the coded data of the above-mentioned format ( Process 416).

Then, it is checked whether the value of the counter i is equal to the value of the variable NC (decision 417). Judgment 417
If the result is NO, it means that the encoding process of the specified number of repetitions has not been completed, so the process returns to the process 409 and the next encoding process is performed. When the result of the determination 417 is YES, the encoded data finally obtained at that time is output to the next process or the like as the encoded data of the encoding result (process 418).

FIGS. 7A and 7B show an example of the decoding process in this case.

First, the coded data to be decoded is decomposed to extract the coded data and the line number data (process 501; this is called unformatting the coded data; the same applies hereinafter).

Then, the value of the main scanning size is set to 8 and the value of the line number data extracted at that time is set to the sub scanning size, and the main scanning size and the sub scanning size are decoded at that time. The condition is set in the encoding / decoding unit 7 (process 502). In addition, a value of the number of times the decoding process is repeated is set in advance in the variable NC, and a counter i for storing the number of times the decoding process is repeated is initialized to 0 (process 503).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 504), and the encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic decoding process (process 5).
05). When the decrypted data is output in this process 505, the decrypted data is stored in a predetermined buffer (process 506).

Here, it is checked whether or not the decoding process has been completed for all the coded data (decision 507). If the result of the judgment 507 is NO, the process returns to the process 504 to decode the next coded data. Execute the conversion process. Also,
When the result of determination 507 is YES, the counter i
Is incremented by 1 (process 508).

Since the decoded data obtained at that time is not the final decoding result, the decoded data is unformatted (process 509). And the counter i
Check whether the value of is equal to (NC-1) (decision 5
10). When the result of the decision 510 is NO, it is necessary to execute the intermediate decoding process, and therefore,
The main scanning size value is set to 8 and the sub scanning size is set to the value of the line number data extracted at that time, and the main scanning size and the sub scanning size are coded and decoded as the decoding conditions at that time. It is set in the conversion unit 7 (process 51
After 1), the process returns to the process 504 to execute the decryption process.

When the result of the judgment 510 is YES, the final decoding process is executed next.
The main scanning size designated at that time and the sub-scanning size obtained by unformatting are set in the encoding / decoding unit 7 (process 512).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 513), and the encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic decoding process (process 5).
14). When the decoded data is output in this process 514, the decoded data is output as image data to the next process (process 515).

Next, it is checked whether a predetermined amount of image data has been obtained (decision 516), and the result of the decision 516 is NO.
When it becomes, the process returns to the processing 513 to execute the decoding processing of the next encoded data. In addition, the result of the determination 516 is Y
When it becomes ES, this decoding process is terminated.

Therefore, in this case, the image data P
Since the encoding process for IX1 is recursively executed m times, if the recursive number of times of this encoding process is not known, the original image data P from the encoded data FDCm
Since IX1 cannot be formed, the confidentiality of image transmission can be maintained.

Since the encoded data FDCm has a smaller data amount than the original image data PIX1, the data transmission time can be shortened. Further, since the image data encoding process and the encryption process can be realized by using the encoding / decoding unit 7, a facsimile apparatus having an encryption function does not require a component (hardware) for encryption. Can be provided at low cost.

The main scanning size referred to at the last decoding process is calculated based on the size in the main scanning direction determined by the image size notified from the partner terminal and the resolution of the image at that time. As the image data amount referred to in the determination 516 at the time of decoding, a value obtained by multiplying the main scanning size and the sub scanning size is used.

The number of times m of the recursive encoding processing may be set in each facsimile apparatus by the user or a service person, or may be set implicitly when this encryption encoding mode is used. The value may be fixedly set in the facsimile machine. Further, the user may be required to input each time communication is performed.

FIG. 8 shows an encryption method according to another embodiment of the present invention.

In this case, first, the image data PIX2 to be encoded is encoded (first encoding) to form the encoded data CD1. Then, this code data C
At the beginning of D1, main scan size data MSD1 representing the main scan size of image data PIX2 and image data PI
Subscan size data SSD1 representing the number of X2 lines
Are sequentially added, and the main scanning size data MSD1, the sub scanning size data MSD1 and the code data CD1 arranged in this order are regarded as image data, and the second encoding process is executed.

The number of bytes of the main scan size data MSD2, the main scan size data MSD1, the sub scan size data MSD1 and the code data CD1 in which the value 8 is set in the code data CD2 obtained by the second encoding process. The sub-scanning size data SSD2 representing the sub-scanning size data
2 and code data CD2 arranged in this order are regarded as image data, and the third encoding process is executed.

Thereafter, in the same manner as described above, a series of data consisting of the main scanning size data, the sub scanning size data, and the code data is sequentially regarded as image data, and the encoding process is repeatedly executed.

Then, the main scanning size data MSDm in which the value 8 is set in the code data CDm formed in the m-th encoding process and the sub-data representing the number of bytes of the m-th encoding target data. Scan size data SSDm
Is sequentially added, and main scan size data MSDm, sub-scan size data SSDm, and code data CDm are arranged in this order to form final code data, which is then formatted into coded data of the above-described format. The finally obtained encoded data is the image data P at this time.
Output as encoded data of IX2. In this case, since it is not necessary to refer to it at the time of decoding, an appropriate value may be set to the line number data LN of encoded data.

Therefore, in this case, as compared with the encryption method of FIG. 5, the amount of code data for the second and subsequent times is small, and thus the coding efficiency is improved as compared with the embodiment of FIG.

An example of the encoding process in this case is shown in FIG.
Shown in (a) and (b).

First, the number of pixels and the number of lines in the main scanning direction of the image data to be encoded are set in the encoding / decoding unit 7 as the main scanning size and the sub scanning size (process 601), and the variable NC is set. Then, the value of the number of repetitions of the encoding process at that time is set, and the value of the counter i for storing the number of repetitions of the encoding process is initialized to 0 (process 602).

Then, 1 bit of the image data to be encoded is extracted and transferred to the encoding / decoding unit 7 (process 603),
The encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic encoding process (process 604), and when the encoding / decoding unit 7 outputs the encoded data at that time, the encoded data is output to a predetermined buffer ( Process 605).

Next, it is checked whether or not the image data has ended (decision 606). When the result of the decision 606 is NO, the process returns to step 603 and the remaining image data is encoded. When the result of determination 606 is YES, the sub-scanning size of the original image data that has been encoded at that time is calculated (process 607), and the main-scanning size data representing the main-scanning size and the calculated The sub-scanning size data representing the obtained sub-scanning size is added to the beginning of the code data formed at that time to form data for the next encoding, and the main scanning size and the sub-scanning size are encoded. Set in the decoding unit 7 (Process 6)
08). Then, the value of the counter i is incremented by 1 (Process 6
09).

Next, one bit of encoded data is taken out from the buffer and transferred to the encoding / decoding unit 7 (process 61).
0), the encoding / decoding unit 7 is caused to execute the above-described arithmetic encoding process (process 611), and when the encoding / decoding unit 7 outputs the encoded data, the encoded data is to be encoded. Is output to a predetermined buffer different from the encoded data (process 612).

Next, it is checked whether or not the coded data to be coded is completed (decision 613), and the decision 6
When the result of 13 is NO, the process returns to step 610 and the remaining encoded data is encoded. When the result of determination 613 is YES, the number of bytes of the original encoded data that has been encoded at that time is calculated as the sub-scanning size (process 614), and the main scanning size data to which the value 8 is set, Also, the sub-scanning size data representing the calculated sub-scanning size is added to the beginning of the code data formed at that time to form data for the next encoding, and the main scanning size and the sub-scanning size are set. The scan size is set in the encoding / decoding unit 7 (process 615).
Then, the value of the counter i is incremented by 1 (process 609).

Here, it is checked whether the value of the counter i is equal to the value of the variable NC (decision 617). Judgment 617
If the result is NO, it means that the encoding process of the specified number of repetitions has not been completed, so the process returns to the process 610 to perform the next encoding process. When the result of determination 617 is YES, the encoded data finally obtained at that time is formatted into the encoded data of the above-described format (process 618), and the encoded data is set as the encoding result. For example, it is output to the next process or the like (process 619).

FIGS. 10A and 10B show an example of the decoding process in this case.

First, the coded data to be decoded is decomposed to extract the coded data (process 701).

Next, the value of the number of times the decoding process is repeated is set in advance in the variable NC, and the counter i for storing the number of times the decoding process is repeated is initialized to 0 (process 702). Further, the main scanning size data and the sub-scanning size data added to the extracted code data are acquired (process 703), and these values are used as the main scanning size and the sub-scanning size, respectively, and the encoding / decoding unit 7 is set (process 704).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 705), and the encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic decoding process (process 7).
06). When the decrypted data is output in this process 706, the decrypted data is stored in a predetermined buffer (process 707).

Here, it is checked whether or not the decoding process has been completed for all the coded data (decision 708). If the result of the judgment 708 is NO, the process returns to the process 705 to decode the next coded data. Execute the conversion process. Also,
When the result of determination 708 is YES, the counter i
Is incremented by 1 (process 709).

Then, it is checked whether the value of the counter i is equal to (NC-1) (decision 710). When the result of the determination 710 is NO, the decrypted data obtained at that time is not the final decryption result, so the process 70
Returning to step 3, the decoding operation is executed again for the decoded data obtained at that time.

When the result of judgment 710 is YES, the next decoding process is to be executed.
The main scanning size data and the sub scanning size data are respectively acquired from the data decoded at that time (process 711), and those values are used as the main scanning size and the sub scanning size, respectively, and the encoding / decoding unit 7 Is set (step 712).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 713), and the encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic decoding process (process 7).
14). When the decoded data is output in this processing 714, the decoded data is output as image data to the next process (processing 715).

Next, it is checked whether a predetermined amount of image data has been obtained (decision 716), and the result of the decision 716 is NO.
When it becomes, the process returns to the processing 713 to execute the decoding processing of the next encoded data. In addition, the result of the determination 716 is Y
When it becomes ES, this decoding process is terminated.

In this case, the image data amount referred to in the determination 716 can be obtained by multiplying the main scanning size and the sub scanning size used at that time.

FIG. 11A shows an encryption method according to still another embodiment of the present invention.

In this case, first, the image data PIX3 to be encoded is encoded (first encoding) to form the encoded data CE1. Then, this code data C
The second encoding process is executed by regarding E1 as image data. At the time of the second encoding processing, the value of the main scanning size is set to 8 and the value of the number of bytes of the code data CE1 is set to the sub scanning size.

Next, the code data CE2 obtained by the second encoding process is regarded as image data, and the third encoding process is executed. Even during this third encoding process,
A value of 8 is set in the main scanning size, and a value of the number of bytes of the code data CE2 is set in the sub scanning size.

Thereafter, similarly to the above, the coded data CE thus formed are sequentially regarded as image data, and the coding process is repeatedly executed, including the first coding process (k
-1) When the first encoding process is executed, 1 is added to the beginning of the code data CE (k-1) obtained by the encoding process.
Header information HD representing the main scanning size and the sub-scanning size used in the (k-1) th encoding process from the second encoding process is added, and the header information HD and the encoded data CE (k-1) are added. Are regarded as image data, the kth encoding process is executed,
The final code data is formed. The value of the main scanning size for the kth time is set to 8, and the value of the number of bytes of the code data CE2 is set to the sub-scanning size.

As shown in FIG. 11B, the header information HD is size information composed of the main scanning size and the sub-scanning size used in the 1st to (k-1) th encoding processing (see FIG. (see c)) are sequentially arranged.

The sub-scanning size used in the kth encoding process is set in the line number data LN of the finally formed encoded data.

Therefore, in this embodiment, the header information consisting of the main scanning size information and the sub-scanning size information necessary for the subsequent decoding processing can be obtained in the first decoding processing, and the header information can be obtained. Is fixed-length data, extraction is easy and the decoding process can be executed at higher speed.

An example of encoding processing in this case is shown in FIG.
It shows in (b).

First, the number of pixels in the main scanning direction and the number of lines of the image data to be encoded are set in the encoding / decoding unit 7 as the main scanning size and the sub-scanning size (process 801), and the variable NC is set. The value of the number of repetitions of the encoding process at that time is set, and the value of the counter i for storing the number of repetitions of the encoding process is initialized to 0 (process 802).

Then, 1 bit of the image data to be encoded is extracted and transferred to the encoding / decoding unit 7 (process 803),
The encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic encoding process (process 804), and when the encoding / decoding unit 7 outputs the encoded data at that time, the encoded data is output to a predetermined buffer ( Process 805).

Next, it is checked whether or not the image data has ended (decision 806). When the result of the decision 806 is NO, the process returns to step 803 to perform the encoding process of the remaining image data. When the result of the determination 806 is YES, the value of the counter i is incremented by 1 (process 807),
At that time, the values of the main scanning size and the sub scanning size of the original image data encoded are stored as the i-th size information # (i) (process 808).

Then, a value of 8 is set in the main scanning size, a value of the number of bytes of code data formed at that time is set in the sub scanning size, and the main scanning size and the sub scanning size are set in the encoding / decoding unit 7. (Process 809).

Next, one bit of encoded data is taken out from the buffer and transferred to the encoding / decoding unit 7 (process 81).
0), the encoding / decoding unit 7 is caused to execute the arithmetic encoding process described above (process 811), and when the encoding / decoding unit 7 outputs the encoded data, the encoded data is to be encoded. Is output to a predetermined buffer different from the encoded data (process 812).

Next, it is checked whether or not the coded data to be coded is completed (decision 813), and the decision 8
When the result of 13 is NO, the process returns to step 810 and the remaining encoded data is encoded. When the result of the determination 813 is YES, the value of the counter i is incremented by 1 (process 814), and the number of bytes of the original encoded data encoded at that time is calculated as the sub-scanning size (process 815). ), The size information of the original encoded data is saved (process 816), and the value of the counter i is (NC-
It is checked whether it is equal to 1) (decision 817). Judgment 8
When the result of 17 is NO, it means that the header information HD is not added, and therefore the process returns to step 809, and the same encoding process as described above is executed.

When the result of the judgment 817 is YES, the next encoding process corresponds to the last encoding process, so the (k-1) size information stored up to that point is collected. The header information HD described above is formed, and the header information HD is added to the buffer information code data (process 818).

Next, the main scanning size is set to 8 and the sub-scanning size is added with the header information HD to set the number of bytes of the entire code data, and the set main scanning size and sub-scanning size are set to the main scanning. The size and the sub-scanning size are set in the encoding / decoding unit 7 (process 819).

Then, one bit of encoded data is taken out from the buffer and transferred to the encoding / decoding unit 7 (process 82).
0), the encoding / decoding unit 7 is caused to execute the above-described arithmetic encoding process (process 821), and when the encoding / decoding unit 7 outputs the encoded data, the encoded data is to be encoded. Is output to a predetermined buffer different from the encoded data (process 822).

Next, it is checked whether or not the coded data to be coded has been completed (decision 823), and the decision 8
When the result of 23 is NO, the process returns to step 820 and the remaining encoded data is encoded. When the result of the determination 823 is YES, the number of bytes of the original encoded data that has been encoded at that time is calculated as the sub-scanning size (line number data LN) (process 82).
4), the coded data finally obtained at that time is formatted into coded data of the above-described format, and the coded data is output as a coding result to, for example, the next process (process 825). ).

FIGS. 13A and 13B show an example of the decoding process in this case.

First, the coded data to be decoded is decomposed to extract the coded data (process 901).

Next, a preset value of the number of times the decoding process is repeated is set in a variable NC, and a counter i for storing the number of times the decoding process is repeated is initialized to 0 (process 902). A value of 8 is set for the main scanning size and a value of the line number data LN at that time is set for the sub scanning size, and these values are set in the encoding / decoding unit 7 as the main scanning size and the sub scanning size, respectively. (Process 903).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 904), and the encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic decoding process (process 9).
05). When the decrypted data is output in this process 905, the decrypted data is stored in a predetermined buffer (process 906).

Here, it is checked whether or not the decoding processing for all the coded data has been completed (decision 907). When the result of the judgment 907 is NO, the flow returns to the processing 904 to decode the next coded data. Execute the conversion process. Also,
When the result of determination 907 is YES, the counter i
Is incremented by 1 (process 908).

Next, the header information HD added to the head of the decoded data formed at that time is taken out (step 909), the (NC-i) th size information of this header information HD is taken out, and the The contents of the size information are set in the encoding / decoding unit 7 as the main scanning size and the sub-scanning size, respectively (process 910). Also, the value of the counter i is incremented by 1 (process 911).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 912), and the encoding / decoding unit 7 executes the above-mentioned arithmetic decoding process (process 9).
13). When the decrypted data is output in this process 913, the decrypted data is stored in a predetermined buffer (process 915).

Next, it is checked whether a predetermined amount of image data has been obtained (decision 916), and the result of the decision 916 is NO.
When it becomes, the process returns to the process 912 to execute the decoding process of the next encoded data. In addition, the result of the determination 916 is Y
When it becomes ES, it is checked whether the value of the counter i is equal to NC (decision 917). The result of judgment 917 is N
When it becomes O, the process returns to the process 910. Also, the judgment 91
When the result of 7 is YES, the finally obtained decoded data is output to the next process as decoded image data (process 918).

In this case, the image data amount referred to in the judgment 916 can be obtained by multiplying the main scanning size and the sub scanning size used at that time.

FIG. 14 shows an encryption method according to still another embodiment of the present invention.

In this case, first, the image data PIX4 to be encoded is encoded (first encoding) to form the encoded data CF1. Then, this code data C
Dummy data DM after F1 and marker code MC
Add 1. At this time, the data amount of the dummy data DM1 is set such that the total data amount of the code data CF1, the marker code MC, and the dummy data DM1 becomes equal to the data size PSZ of the original image data PIX4.

Next, the combined data of the code data CF1, the marker code MC and the dummy data DM1 is regarded as image data, and the second encoding process is executed.
At the time of this second encoding processing, the value 8 is set in the main scanning size and the data size PS is set in the sub scanning size.
Set the value for the number of bytes in Z.

Then, the marker data MC2 and the dummy data DM2 are added to the code data CF2 obtained in the second encoding process. Also at this time, the code data C
The dummy data DM is set so that the total data amount of F2, the marker code MC and the dummy data DM2 becomes equal to the data size PSZ of the original image data PIX4.
Set the data amount of 2.

Next, the combined data of the code data CF2, the marker code MC and the dummy data DM2 is regarded as image data, and the third encoding process is executed. Even during the third encoding process, the value 8 is set to the main scanning size and the value of the number of bytes of the data size PSZ is set to the sub scanning size.

Thereafter, in the same manner as described above, the marker code MC and the dummy data DM are added to the sequentially formed code data CF so that the total data amount becomes equal to PSZ, and the code data CF is added. , Marker code M
C and dummy data DM are regarded as image data, the encoding process is repeatedly executed, and m including the first encoding process is performed.
When the encoding process of the second time is executed, the encoded data CFm obtained by the encoding process is used as the finally obtained encoded data to form the encoded data in the above-described format.

At this time, the line number data LN of the encoded data to be finally formed is the original image data PI.
Set the number of X4 lines.

Therefore, in this embodiment, since the dummy data is added so that the size of the original image data is always equal to the size of the original image data during the encoding process, the size of the decoded data is equal to the size of the image data during the decoding process. Since it is sufficient to execute the process until the data size is reached, it is not necessary to add data necessary for the decoding process.

An example of encoding processing in this case is shown in FIG.
It shows in (b).

First, the number of pixels in the main scanning direction and the number of lines of image data to be encoded are set in the encoding / decoding unit 7 as the main scanning size and the sub scanning size (process 1001), and the variable NC is set. Then, the value of the number of repetitions of the encoding process at that time is set, and the value of the counter i for storing the number of repetitions of the encoding process is initialized to 0 (process 1002).

Then, 1 bit of the image data to be encoded is extracted and transferred to the encoding / decoding unit 7 (process 100
3), causing the encoding / decoding unit 7 to execute the arithmetic encoding process described above (process 1004), and at that time, the encoding / decoding unit 7
When the code data is output from, the code data is output to a predetermined buffer (process 1005).

Next, it is checked whether or not the image data has ended (decision 1006). If the result of the determination 1006 is NO, the process returns to step 1003 and the remaining image data is encoded. Also, the result of determination 1006 is YES.
The counter i is incremented by one (processing 1
007), a marker code and dummy data are added to the code data formed at that time so that the total data amount becomes equal to the data size of the original image data (process 1008).

Then, the value 8 is set in the main scanning size, the value of the number of bytes of the data size of the image data at that time is set in the sub scanning size, and the main scanning size and the sub scanning size are set in the encoding / decoding unit 7. It is set (process 1009).

Next, 1 bit of the encoded data is taken out from the buffer and transferred to the encoding / decoding section 7 (process 101
0), and causes the encoding / decoding unit 7 to execute the arithmetic encoding process described above (process 1011). At that time, the encoding / decoding unit 7
When the coded data is output from, the coded data is output to a predetermined buffer different from the coded data to be coded (process 1012).

Next, it is checked whether or not the coded data to be coded has been completed (decision 1013). If the result of decision 1013 is NO, the process returns to step 1010 and the remaining coded data is returned. The encoding process of is performed. When the result of the judgment 1013 is YES, the value of the counter i is incremented by 1 (process 1014) and it is checked whether or not the value of the counter i is equal to the value of the variable NC (decision 1015). When the result of the determination 1015 is NO, a marker code and dummy data are added to the code data formed at that time so that the entire data amount becomes equal to the data size of the original image data (Processing 1
016), and returns to the processing 1010 to execute the same encoding processing as described above.

When the result of the judgment 1015 is YES, the coded data obtained at that time is formatted into the above-mentioned format (process 1017), and the coded data is used as the coding result, for example, the process of the next stage. (Processing 1018).

16 (a) and 16 (b) show an example of the decoding process in this case.

First, the coded data to be decoded is decomposed, the coded data is extracted, and the value 8 is set to the main scanning size.
The values of the number of bytes of the data size of the image data at that time are respectively set in the sub-scanning size, and those values are set as the main scanning size and the sub-scanning size, respectively, and the encoding / decoding unit 7 is set.
Is set (step 1101). Here, the data size of the image data is calculated from the resolution in the main scanning direction of the image at that time, the length in the main scanning direction, and the value of the line number data LN.

Next, a preset value of the number of times the decoding process is repeated is set in a variable NC, and a counter i for storing the number of times the decoding process is repeated is initialized to 0 (process 1102).

Then, 1 bit of the code data is read and transferred to the encoding / decoding unit 7 (process 1103), and the encoding / decoding unit 7 is caused to execute the above-mentioned arithmetic decoding process (process 1104). When the decrypted data is output in this process 1104, the decrypted data is stored in a predetermined buffer (process 1105).

Here, it is checked whether or not the decoding process has been completed for all code data (decision 1106),
When the result of determination 1106 is NO, the process 110
Returning to step 3, the decoding process for the next encoded data is executed.
The end determination of the coded data is performed by detecting that the data amount of the decoded data is equal to the data size of the image data at that time.

When the result of determination 1106 is YES, the value of the counter i is incremented by 1 (process 110
7), it is checked whether the value of the counter i is equal to (NC-1) (decision 1108). The result of judgment 1108 is NO.
When it becomes, the process returns to the processing 1103, and the decoding data formed at that time is regarded as code data, and the decoding operation is executed.

On the other hand, when the result of determination 1108 is YES, the values of the main scanning size and the sub scanning size of the image data at that time are set in the encoding / decoding unit 7 (processing 1109), and the encoded data is 1 bit. It is read and transferred to the encoding / decoding unit 7 (process 1110), and the encoding / decoding unit 7
To execute the arithmetic decoding process described above (process 111
1). When the decrypted data is output in this process 1111, the decrypted data is stored in a predetermined buffer (process 1112).

Next, it is checked whether a predetermined amount of image data has been obtained (decision 1113). If the result of decision 1113 is NO, the process returns to step 1110 to execute the decoding process of the next encoded data. To do. When the result of determination 1113 is YES, the decoded data finally obtained is output to the next process as decoded image data (process 1114).

By the way, in each of the above-mentioned embodiments, the format shown in FIG. 4A is used as the format of the encoded data, but the format shown in FIG. 4B is used as this format. It can also be used.

The coded data shown in FIG. 16B has a marker code prefix M consisting of a predetermined bit pattern at the beginning.
CP, marker code SOI representing the beginning of the image (data), line number data LN0 in which the line number 0 is set, code data, marker code prefix MCP, and next line number data Marker code DLN, line number data LN representing the number of lines in the image, marker code prefix MCP, and marker code E representing the end of the image
It consists of OI.

Further, in each of the above-mentioned embodiments, QM-coder is used as the arithmetic coding system, but other arithmetic coding system can be used. Further, in the above-described embodiment, the case where the present invention is applied to the group 3 facsimile machine is shown, but the present invention can be similarly applied to other devices.

Further, the present invention can be similarly applied to the case of combining with a predictive coding method using a template.

[0150]

As described above, according to the present invention,
If the specific content of the encoding method, such as the number of repetitions of the encoding process, is not known, the encoded data cannot be properly decoded, so that the effect of maintaining the confidentiality of information is obtained. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a group 3 facsimile apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining the principle of arithmetic coding.

FIG. 3 is a flowchart showing an example of QM-coder encoding processing and decoding processing.

FIG. 4 is a schematic diagram illustrating a data format of encoded data.

FIG. 5 is a schematic diagram for explaining an encoding method according to an embodiment of the present invention.

6 is a flowchart showing an example of the encoding process of FIG.

7 is a flowchart showing an example of the decoding process of FIG.

FIG. 8 is a schematic diagram for explaining an encoding method according to another embodiment of the present invention.

9 is a flowchart showing an example of the encoding process of FIG.

10 is a flowchart showing an example of the decoding process of FIG.

FIG. 11 is a schematic diagram for explaining an encoding method according to still another embodiment of the present invention.

FIG. 12 is a flowchart showing an example of the encoding process of FIG.

FIG. 13 is a flowchart showing an example of the decoding process of FIG.

FIG. 14 is a schematic diagram for explaining an encoding method according to still another embodiment of the present invention.

15 is a flowchart showing an example of the encoding process of FIG.

16 is a flowchart showing an example of the decoding process of FIG.

Claims (4)

[Claims] 1. A coding / decoding method for coding a symbol sequence by an arithmetic code, wherein at the time of coding, the symbol sequence is coded, and the code string obtained thereby is coded again, and this coding process is performed. The code string obtained by is re-encoded, this repetitive encoding process is repeatedly executed until the number of times including the first encoding process reaches a predetermined number, and at the time of decoding, the code data is decoded and The data string obtained by is decoded again, and this iterative decoding process is repeatedly executed until the number of times including the first decoding process reaches the above predetermined number, and the finally obtained data string is converted into the original symbol. A coding / decoding method characterized by outputting as a sequence. 2. A coding / decoding method for coding a symbol sequence by an arithmetic code, wherein at the time of coding, the symbol sequence is coded, and the code string obtained thereby is coded again, and this coding process is performed. The code string obtained by the above is encoded again, and this repetitive encoding processing is repeatedly executed until the number of times including the first encoding processing reaches a predetermined number, and the code data is generated for each code data. Including the coding parameters used in the coding process, when decoding, the coded data is decoded, the resulting data string is decoded again, and this iterative decoding is the first decoding process. Are repeatedly executed until the number of times including the above reaches the above-mentioned predetermined number, and the finally obtained data string is output as the original symbol sequence, and in each decoding process, Coding and decoding method, characterized in that in that reference to the encoding parameters included in the data string to be processed decoding applying a decoding process to the data string of the portion excluding the coding parameters. 3. A coding / decoding method for coding a symbol sequence by an arithmetic code, wherein at the time of coding, the symbol sequence is coded, and the code string obtained thereby is coded again, and this coding process is performed. The code string obtained by is re-encoded, and this repetitive encoding process is repeatedly executed until the number of times including the first encoding process reaches a predetermined number, and finally the encoded data is At the time of decoding, the code data is decoded and the data string obtained by decoding is included, including the coding parameter data in which multiple coding parameters applied at the time of coding are arranged according to the order of the coding process. The decoding process is performed again, and this iterative decoding process is repeatedly executed until the number of times including the first decoding process reaches the predetermined number, and the finally obtained data string is used as the original symbol system. In addition, in the first decoding process, the coding parameter data included in the coded data is extracted and the corresponding coding parameter of the coding parameter data is used to remove the coding parameter data. The encoding / decoding method is characterized in that the encoding process is applied to the above portion, and in the second and subsequent encoding processes, the corresponding encoding parameter of the above encoding parameter is applied. 4. A coding / decoding method for coding a symbol sequence by an arithmetic code, wherein at the time of coding, the symbol sequence is coded, and the code string obtained thereby is coded again, and this coding process is performed. The code string obtained by the above is encoded again, and this repetitive encoding processing is repeatedly executed until the number of times including the first encoding processing reaches a predetermined number, and in the encoding processing other than the final encoding processing, A predetermined number of dummy data is added to the coded data obtained after the encoding process, the coded data is decoded at the time of decoding, the data string obtained thereby is decoded again, and this iterative decoding process is performed. , Repeatedly until the number of times including the first decoding process reaches the above specified number, output the finally obtained data string as the original symbol sequence, and decode other than the first decoding process. In the process, after removing a predetermined number of dummy data from the decoded data, coding and decoding method characterized by applying the decoding process.