JPS5815994B2 - Gazoshingouayamarikenshiyutsusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a code error detection device on the receiving side when a binary image signal representing white or black level is encoded and transmitted.

Conventionally, when a binary image signal is encoded and transmitted, a code error detection device on the receiving side uses a coding method on the transmitting side that depends on the white or black level of the signal and the temporal duration of the signal. There is a device that detects code errors by monitoring the scanning time during which the received code is decoded on the receiving side using a method (hereinafter referred to as run-length coding method) that encodes the received code. Code errors cannot be detected until after all the codes have been decoded, so a buffer memory with one or more scanning lines is required to store the decoded image signals, making the device expensive. there were.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional technology, and an object of the present invention is to improve the quality of the received code by using an encoding method that is completely different from the run-length encoding method. To provide an inexpensive device which detects a code error by finding the position of a synchronization code before decoding an image signal from an address code, which is a part, and which does not include a buffer memory for storing the decoded image signal.

According to the present invention, when a binary image signal is encoded and transmitted, on the transmitting side, the image signal is encoded in m-bit units of a certain length, and an address code related to the position of the image signal and an address code related to the position of the image signal are input. Divide into code codes related to level and encode,
The synchronization code representing the start of m bits of the image signal, the address code representing m bits of the image signal, and the code code are transmitted in this order, and on the receiving side, only the address code that is part of the received code corresponds to the m bits of the image signal. The end of the received code is detected, and the presence or absence of a code error is checked by checking whether a synchronization code follows.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an example of the encoding method used in the present invention, and shows the case where it is applied to a binary image signal.

FIG. 1A shows a binary character string of one scanning line, taking a facsimile signal as an example, and the black level is indicated by diagonal lines.

In the figure, the run lengths of the white level and black level are shown numerically, and the number of samples for one scanning line is 1024.

The encoding method uses the image signal A1024 as the first division.
Divide the bit into 4 bits and check whether there is a black level in each of the 256 bits.If there is a black level, give it the code O to represent the white level, and if so, give the code 1 to represent the black level (this is called a primary division code). ), 1 representing the black level in the primary division code
In this case, the second division is to divide the 256-bit image signal A into 4, and check whether there is a black level in 64-bit units. give a code (called a quadratic division code),
Below, codes are created in units of 16 bits and 4 bits (referred to as 3rd and 4th division codes, respectively), and finally, if the 4th division code is 1 representing the black level, the 4 bits of the image signal A are used as the code, It is called a unit area code.

(Hereinafter, this encoding method will be referred to as a multi-stage divisional encoding method.

) Here, the primary to quartic division codes are called address codes because they are related to the position of the white level or black level of the image signal, and the unit area code is related to the position of the white level or black level of the image signal. It is called a code symbol because it is related to the level of the code.

In the image signal A, the code resulting from the primary division is 1110, and 1 appears three times.

The secondary division code is a 3X4 = 12 bit code as shown in the figure, and the tertiary division code is 3X4 = 12 bits.
The quaternary division code is 4×4=16 bits.

Since the number of unit area codes is 4, 7×4=28 bits are the remaining unit area codes.

When encoding as described above is performed, the maximum possibility that O's will continue is 6, so a code in which 8 O's are consecutive can be given as a synchronization code representing the break of one scanning line.

According to this encoding, when the black level, that is, the number of 1's included in the primary division code, is determined, the number of bits of the secondary division code is 3.
When the black level, that is, the number of 1's included in the secondary division code, tertiary division code, and quaternary division code is determined, such as X4 = 12 bits, the tertiary division code, 4
The number of bits of the next division code and unit area code is determined.

Since the code encoded on the transmitting side has the above properties, on the receiving side, by calculating the number of 1's included in the quaternary division code, that is, the address code, from the primary division code, the unit area code, that is, Detects the end of the code symbol, checks whether a synchronization code continues after it, detects the presence or absence of a code error, and if there is a code error, does not decode that scanning line and repeatedly outputs the previous scanning line. However, if there is no code error, it is directly decoded and output.

FIG. 2 is an example of a circuit configuration for implementing the code error detection device of the present invention.

The received codes input manually are stored in the buffer memory 3.

The four bits of the primary division code read out from the buffer memory 3 are counted by a counter 4 to the number of 1's.

The output of the counter 4 is input to the memory control circuit 8, and the secondary division code is read out from the buffer memory 3 in response to a signal from the memory control circuit, and the number of 1s is counted by the counter 5.

The output of the counter 5 is input to the memory control circuit 8, and the third division code is read out from the buffer memory 3 according to the signal from the memory control circuit 8, and the number of 1s is counted by the counter 6.

The output of the counter 6 is input to the memory control circuit 8, and the quaternary division code is read out from the buffer memory 3 according to the signal of the memory control circuit 8, and the number of 1s is counted by the counter 7.

The output of the counter 7 is input to the memory control circuit 3, and the memory control circuit 8 reads out the next signal of the unit area code, that is, the code code, by adding the output of the counter 7 to the address of the buffer memory, and synchronizes with the comparator 9. The code is compared with the code, and if they match, a signal without a code error is output from 10, and if they do not match, a signal with a code error is output from 10.

In other words, the error detection device of the present invention detects code errors in address codes, but does not detect code errors in code codes.

However, since a code error occurs in units of one bit, there is almost no effect on the actual paper.

Of course, the above method can also be applied when the level of the image signal becomes two or more values.

As described above, the image signal error detection device of the present invention uses the multi-stage divisional coding method on the transmitting side, so that on the receiving side,
To provide an inexpensive device that can perform error detection before decoding an image signal and does not include a buffer memory for the decoded image signal, which is necessary in a conventional run-length encoding error detection device. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an embodiment of the binary image signal encoding method according to the present invention, and FIG. 2 is a diagram of an error detector for implementing the binary image signal error detection device of the present invention. It is a block diagram. In the figure, 3 is a buffer memory IJ, 4, 5, 6.7 is a counter, 8 is a memory control circuit, and 9 is a comparator.

Claims (1)

[Claims] 1 Divide the image signal into units of a certain length (for example, one scanning line, and divide the divided image signal into a plurality of blocks,
The presence or absence of a black level contained in each block is detected, and if there is no black level, a code “0”° is assigned, and if there is a black level, a code “°°1”1 is assigned, and the block in which the black level has been detected is Divide into multiple blocks and repeat the same operation to divide the address code related to the position of the image signal and the last divided block that contains the black level into code code related to the level of the image signal. In the encoding/transmission device for an image signal, which transmits in the order of a synchronization code representing the start of the image signal unit length, the above address code, and the above code code, the receiving side includes a buffer memory for temporarily storing the received code, and the above buffer. means for reading out a predetermined number of address code strings from a memory among the address codes that are part of the received code; and a code included in the read address code string.
A means for counting the number of ``1''s, a means for reading the next address code string according to the number of ``1'' degrees, and a means for reading out the next address code string according to the number of ``1'' degrees, and the same means thereafter are repeated to determine the number of codes ``°1'' included in the last address code string. means for counting the number of "1"s, means for determining the address of the buffer memory where the next synchronization code should be stored based on the number of "1" 1s, and reading the memory address and determining whether the contents match the synchronization code or not. An image signal error detection device characterized in that the presence or absence of a code error is detected by a means for detecting a code error.