JPH01120963A - Predictive coding device - Google Patents

Abstract

PURPOSE:To eliminate the time division of an existing transmission line without the provision of new transmission line so as to transmit the number of the picture element of one scanning line by adding one line of a virtual original picture where prediction is coincident from the leading picture element till a picture element just before the final picture element and the prediction is in discrepancy to the final picture element only before the 1st line of an original picture. CONSTITUTION:A counter 102 uses a phase signal (c) being one shot at the head of the pattern to load one scanning line picture element number (n). Then the loaded value is incremented at the trailing edge of a picture signal clock (b) and when the count is zero, the counter output is made to a high level for one picture signal clock. When a predictive coding section 1B executes predictive code processing to a picture signal a3, only the final picture element of the first scanning line is not predicted and a predicted error signal string is one length, coded by the A mode and an EOL code to separate the A mode code and the B mode code is given to start the predictive coding processing of the next scanning line. Thus, in the decoding processing, one scanning line picture element number of the pattern is recognized by decoding the A mode code inputted first.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a predictive encoding device used for highly efficient encoding of image signals such as facsimile signals.

2. Description of the Related Art Recently, predictive encoding devices for image information have come into widespread use in fields such as facsimile.

This predictive coding device is used, for example, in Engineering Studies and Implementation
A Fast Digital Newspaper Page
Facsimile system (Kutsu, Tanaka, Miwa, Ai・
E.E. International Conference on Communicating, Proceeding'' HNG
I NEERI NGSTUDIES AND IMP
LEMENTATION OF AFAST DIGI
TAL NEWSPAPERPAGE FAC8I-M
ILE SYSTEM” (UNO, TANAKA, M
IWA, IEEE International Co.
communication on communication
.

Proceedings Vol., I) p223
-227. 1984) A configuration in which two words are used is known. Below is Figure 5.

A conventional predictive encoding device will be explained using No. 64.

FIG. 5 is a block diagram of a conventional predictive encoding device.

Figure 5 (= where 51 is the value of the original pixel of interest (l or O
) from the values of surrounding pixels and outputs it together with the prediction result d and the prediction matching rate. A prediction unit 52 compares the prediction result d with the value of the original pixel a, and if they match, it outputs a numerical value as the prediction error e. A prediction comparison unit 53 outputs a numerical value 0 and a numerical value 1 in the case of mismatch, and a prediction comparison unit 53 divides the prediction error e into groups with a high prediction coincidence rate and groups with a low prediction coincidence rate in units of scanning lines, and collects the same groups and outputs a rearrangement error f. The prediction error relocation unit 54 counts the distance between mismatched pixels of the relocation prediction error if, and calculates the run length r.
The run count unit 55 encodes the run length r using the encoding method for the prediction matching rate group used by the leading prediction error constituting each run length, and outputs the code i and the code clock j. The output encoding unit 56 is a timing unit that generates operation timing from the image signal clock b and the phase signal C indicating the beginning of the scanning line.

The operation of the above configuration will be explained below. FIG. 6 is an example showing the flow of predictive encoding processing in a conventional device. The original image a is a binary image, and l or 0 indicates the value of the original pixel. The prediction unit 51 predicts the value (1 or 0) of the original pixel of interest from the values of surrounding pixels, and calculates the prediction result d (1 or 0).
) is output along with the prediction matching rate, which indicates the probability that the prediction is correct. The predicted matching rate is converted into A mode when it is 90% or more, and converted into B mode when it is less than 90% and output.

The prediction comparison unit 52 compares the prediction result d with the original image a, and outputs 1 as the prediction and error e when the prediction is wrong, and 0 when the prediction matches. The prediction error e for the prediction result dC of the A mode has a high occurrence frequency of O, and the prediction error e for the prediction result d of the B mode has a high occurrence frequency of 1.

The prediction error relocation unit 53 writes the A-mode prediction error e from the beginning of the error relocation memory, and writes the B-mode prediction error e from the end of the same memory.

When the rearrangement of prediction errors e for one scanning line is completed, the prediction errors e of mode A are gathered at the beginning of the error rearrangement memory, and since the prediction matching rate is high, the distance between the prediction mismatching pixels becomes long, and the prediction error e of mode B is In the portion where the prediction errors e of , the prediction mismatch rate is low, the distance between the prediction mismatch pixels becomes short.

The run counting unit 54 counts the distance between predicted mismatched pixels of the reallocation prediction error f (this is called a run length) and outputs it as a run length r. Therefore, the run length r of the A mode often has a large numerical value, and the run length r of the B mode often has a small numerical value.

The encoding unit 55 encodes one code i for one run length r.
is assigned and output together with the code clock j. In order to increase the encoding efficiency, when encoding the A-mode run length r, an encoding method is used that assigns a code with a short number of bits to a large number, and the B-mode run length r is When encoding, use a code (hi method) in which a code with a short number of bits is assigned to a small number.
Coding efficiency is increased by assigning codes with a short number of bits. As mentioned above, the run length r of A mode and the run length r of B mode have different distributions of run length values, so they are encoded differently. It's being done.

In the case of the reallocation prediction error f shown in FIG. 6, the run length cannot be counted because the final pixel value of the A-mode prediction error is 0. Therefore, the run count section 54
counts up to the first pre-1jllll mismatched pixel in B mode as a run length r=3, and the encoding unit 55 encodes this run length r=3 using the A mode encoding method.

In the encoding unit 55, when A-mode encoding is completed, an EOL code is added so that the A-mode code string and the D-mode code string can be correctly separated at the time of decoding.

As for the rearrangement prediction error fn of the n-th line shown in FIG. 7, the run length cannot be counted because the predictions of the last pixel of the scanning line match. Therefore, the run count section 54
is one run length of 5 up to the first prediction mismatch pixel of the relocation prediction error fn+1 of the next line, that is, the n+1th line.
The encoding unit 55 encodes in the group B mode to which the first pixel of the main run length belongs. however,
If the n-th line is the final scanning line of one page, there is no next line, so it is necessary to add end data to generate the run length.

Therefore, the coding break of the reallocation prediction error fn,
The scan line breaks do not match. Therefore, the decoding device needs to execute the decoding process after receiving information regarding the number of pixels in one scanning line from the encoding device in advance by the following means. As a first means, as shown in FIG. 8, a control information transmission line 84 is provided between the encoding device 81 and the decoding device 82 in addition to the compressed code transmission line 83. There is a method of transmitting the number of pixels of one scanning line using

As a second means, when performing compressed code transmission, the code is transmitted using a transmission frame as shown in FIG. There is a method of transmitting the number of pixels in l scanning lines.

Problems to be Solved by the Present Invention However, in the above configuration, in order to transmit the number of pixels of one scanning line, the first means requires the provision of a new transmission path, resulting in an increase in line usage charges. and the second
This method has the problem that the compressed code and control information are transmitted by time-sharing the existing transmission path, resulting in a reduction in the transmission efficiency of the compressed code.

The present invention solves the above-mentioned problems, and provides a predictive coding device that eliminates the need to create a new transmission path and time-divide existing transmission paths in order to transmit the number of pixels in one scanning line. It is something to do.

Means for Solving the Problems The present invention provides that before the first line of the original image, the predictions match from the first pixel to the pixel immediately before the last pixel, the prediction is wrong only for the last pixel, and the number of pixels is equal to one scan of the original image. The above object is achieved by providing a virtual original image adding means for adding one line of a virtual original image that matches the number of line pixels.

According to the above configuration, the present invention adds pixel count information for one scanning line to the beginning of the compression code for one screen, thereby making it possible to transmit the information from the predictive encoding device to the predictive decoding device. This reduces transmission line usage fees or improves code transmission efficiency.

Embodiment FIG. 1 is a block diagram of a predictive encoding device according to an embodiment of the present invention. In FIG. 1, IA is a virtual original image adding section that adds a virtual original image before the first line of the original image, and IB is a virtual original image adding section that adds a virtual original image before the first line of the original image. A predictive encoding unit 101 performs predictive encoding processing, a line memory 102 delays the original image a by one scanning line period and outputs it;
103 is a counter that generates a virtual original image, and 103 is an output signal a1 of the line memory 101 and an output signal a2 of the counter 102.
This is an OR gate that takes the logical sum of the following. Predictive encoding unit IB
The internal configuration and predictive coding algorithm are the same as those of the predictive coding device shown in the conventional example. Also, when making predictions,
If the reference pixel goes outside the screen due to the position of the pixel of interest,
The reference pixel is a white pixel.

The operation of the above configuration will be explained using the timing diagram shown in FIG.

The original image a (second tN(a)) is input to the line memory 101 in scanning line order starting from the first line. line memory 10
1 can store an original image for two scanning lines.

The original image of the first line is the phase signal c (Fig. 2(b))
It is written to the line memory 101 in synchronization with the next phase signal cC, and read out from the line memory 101 in synchronization with the next phase signal cC. Therefore, the output signal al (FIG. 2(C)) from the line memory 101 is a signal delayed by one phase period with respect to the original image a.

On the other hand, the counter 102 receives the phase signal C of the first view at the top of the screen.
Load n, the number of pixels per scanning line. Counter 1 in Figure 3
02 shows a timing diagram for generating a virtual original image.

In this example, the original image is a black and white binary image, as shown in Fig. 3(d).
In the counter output a2 shown in , a High level bell indicates black, and a Low level indicates white.

The counter 102 has an image signal clock b (FIG. 3(b)).
At the falling edge of , the loaded value is subtracted, and when the counter value (FIG. 3(C)) becomes zero, the counter output is set to High level for one image signal clock. Therefore, the virtual screen has white pixels from the 1st pixel to the n-1th pixel,
The n-th pixel becomes a black pixel. Therefore, when prediction is performed on the virtual screen, the predicted value and the pixel value of the virtual screen match from the first pixel to the (n-1)th pixel, and the predicted value and the pixel value of the virtual screen differ for the nth pixel.

Therefore, the image signal a3 (second
In FIG. 2(e), as shown in FIG. 2, the image signal of the first scanning line is an image signal in which only the final pixel is mispredicted, and thereafter it matches the original image a.

When the predictive encoding unit IB performs predictive encoding processing on the image signal a3 (FIG. 2 (e)), only the last pixel of the first scanning line is mispredicted, and the prediction error signal sequence becomes one run length. The code is encoded in A mode, an EOL code for separating the A mode code and B mode code is added, and predictive encoding processing for the next scanning line is started. Therefore, the code i is finally output in the format shown in FIG.

Therefore, in the decoding process, the number of pixels in one scanning line of the screen can be determined by decoding the A-mode code that is first input.

Although this embodiment has been described for the case of predictively encoding a binary image, it is clear that the present invention can also be applied to predictively encoding a multilevel image. is a hypothetical original image in which the predictions match from the first pixel to the pixel immediately before the last pixel before the first line of the original image, only the last pixel is a prediction mismatch, and the number of pixels matches the original image - the number of scanning line pixels. By providing a virtual original image adding means for adding lines, a dedicated transmission path can be prepared to transmit the pixel number information for one scanning line from the predictive encoding device to the predictive decoding device, and the compressed code transmission line can be time-divided. This eliminates the need to use the network as a network, which reduces line charges and improves the efficiency of using transmission lines, which has great effects.

[Brief explanation of the drawing]

Fig. 1 is a block wiring diagram of a predictive encoding device according to an embodiment of the present invention, Fig. 2 is a timing diagram showing the operation of the predictive encoding device, and Fig. 3 is a virtual original image added in the predictive encoding device. Fig. 4 is a diagram showing the format of the code output by the predictive coding device, Fig. 5 is a block wiring diagram of the conventional predictive coding device, and Fig. 6 is the conventional predictive coding. Fig. 7 is a conceptual diagram showing the predictive coding method of the device. Fig. 7 is a conceptual diagram showing the processing method when the last pixel of the rearranged prediction error signal sequence matches the prediction in the conventional predictive coding device. Fig. 8 is the conventional predictive coding method. A system configuration diagram when a predictive encoding device transmits scanning line pixel number information to a predictive decoding device using a control information line. Figure 9 shows a conventional predictive encoding device that controls scanning line pixel number information within a transmission frame. FIG. 3 is a diagram of a transmission frame format when transmitting using information tilting. 1A...virtual original image adding unit, IB...predictive encoding unit,
10100. Line memory, 102... Counter, 1
03...OR gate. Name of agent: Patent attorney Toshi Nakao (1 person)
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Claims (1)

[Claims] a prediction means that predicts the value of the original pixel of interest from the values of surrounding pixels and outputs a prediction result value and prediction matching rate; and a prediction error that compares the prediction result value and the original pixel value to create a prediction error signal. a signal generating means; and a prediction error that divides the prediction error signal in units of scanning lines into two or more groups depending on the level of prediction matching rate, collects and rearranges the prediction error signals for each group, and creates a prediction error signal sequence. a signal sequence generating means; a distance measuring means for measuring the distance between mismatched pixels of the prediction error signal sequence; A hypothetical encoding means that matches the prediction from the first pixel before the first line of the original image to the pixel immediately before the last pixel, only the last pixel has a prediction mismatch, and the number of pixels matches the number of pixels of one scanning line of the original image. A predictive encoding device comprising virtual original image adding means for adding one line of an original image.