JPS63197172A - Prediction encoder - Google Patents

Abstract

PURPOSE:To improve encoding efficiency, by providing a first encoding means which performs encoding by adding an identification code representing which predictor is selected among plural predictors on a predicted result, and a second encoding means which performs the encoding by adding a predictor switching code representing the switching of the predictor on the identification code. CONSTITUTION:A minimum prediction error selection circuit 102 outputs the identification code 108 to select the predicted results of the predictor 101A-101D with a few of prediction errors to a data selector 104 and an addition circuit 105, and also outputs the prediction switching code 100 to switch the predictors 101A-101D to the addition circuit 105. The addition circuit 105 adds the identification code 108 and the predictor switching code 109 on a selected predicted result, and outputs the predicted result 110 with a unit of a prescribed number of picture elements to an encoder 106. And the prediction switching code is set at '1' only when the predictors 101A-101D are switched, and a value corresponding to the predictors 101A-101D is outputted to the identification code, and in the case other than the above, both the prediction switching code and the identification code are set at '0's, thereby, it is possible to improve the encoding efficiency as a whole.

Description

[Detailed description of the invention] This relates to an encoding device.

BACKGROUND OF THE INVENTION Recently, a high-efficiency encoding method for binary images using an adaptive prediction method has come to be used as a core technology for high-speed facsimile in fields such as newspaper transmission, which require a high code compression rate. This adaptive predictive coding method is described, for example, in ``Dot signal processing device'' disclosed in Japanese Patent Application Laid-Open No. 56-27565.
It is described in.

In the adaptive predictive coding method, multiple pixels around the encoded pixel are used as reference pixels, and the value (color) of the encoded pixel is predicted from the value (black and white color combination) of the reference pixel.
The prediction result is length encoded. FIG. 3 shows a circuit block diagram of an adaptive predictive coding method using a conventional predictor.

Signals read by the original reading device 4 through main scanning and sub-scanning are subjected to sampling and quantization by the binarizer 5, and become digital image signals.

This is temporarily stored in memory 6. The 2 to 12 reference pixels read from the memory 6 are used by the predictor 7 to predict the value of the coded pixel. The prediction result from the predictor 7 is length encoded in the encoder 8.

Particularly, in the case of a paper surface such as a newspaper where text parts and halftone photographs of various mesh numbers are mixed, the predictor 7 having reference pixels suitable for the properties of each image is used to improve the encoding efficiency. A widely used technique is to have a plurality of pixels, adaptively switch them in units of a fixed number of pixels, perform prediction processing, and encode the prediction results.

Problems to be Solved by the Invention However, when prediction is performed in units of a fixed number of pixels using a plurality of predictors, it is necessary to add an identification code indicating which predictor has been selected. As a method for adding this identification code, a method is known in which the prediction result is added to a code after run-length encoding.

However, in the above-mentioned method, when the effect of adaptively switching the predictor by reducing the unit of a fixed number of pixels is achieved, the code amount of the identification code increases and the encoding efficiency decreases.

Therefore, it is conceivable to add an identification code indicating which predictor has been selected from among the plurality of predictors to the prediction result. Note that the identification code is also a run-length code as a prediction result. Here, the run-length code is the total length of the number of consecutive "O" codes and one "1" code in the prediction result, and the longer the "0" code continues, the more coded it is. The number of subsequent codes (for example, the output of the encoder 8 described in the conventional example) is reduced, and the coding efficiency is improved. However, when a large number of predictors are incorporated, several bits of the identification code are required, and adding it as is will result in the prediction result, that is, the "0" code of the run-length code being divided, and the code will not be encoded. There is a problem that efficiency decreases.

In order to solve this problem, the present invention adds a predictor switching code indicating the switching of the predictor to the identification code, thereby minimizing the division of the "0" code of the run-length code and improving the overall coding efficiency. The purpose is to improve the

Means for Solving the Problems The present invention provides first encoding means for adding and encoding an identification code indicating which predictor has been selected from among a plurality of predictors to a prediction result; The above object is achieved by providing a second encoding means for adding and encoding a predictor switching code indicating switching to the identification code.

Effects of the Invention The present invention minimizes division of 0'' codes in run-length codes of prediction results with the above configuration, and improves coding efficiency when coding is performed by switching a plurality of predictors in units of a fixed number of pixels. This makes it possible to

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block wiring diagram of a predictive encoding device according to an embodiment of the present invention, and FIG. 2 is a conceptual diagram showing the method and contents of adding an identification code and a predictor switching code to a prediction result in the same device. .

As shown in FIG. 1, an input pixel signal 100 is input to a predictor 1
Prediction is performed by 01A, 10IB1101C, and 10ID and converted into prediction results, and each prediction result is sent to the minimum prediction error selection circuit 102 and the buffer memory 103A.
Output to 1103B, 1030.103D.

The minimum prediction error selection circuit 102 counts the prediction errors of each prediction result and selects a predictor 10 with a small prediction error.
Identification code 1 for selecting prediction results 1A to 101D
08 to the data selector 104 and the additional circuit 105, and a predictor switching code 109 for switching the predictors 101A to 101D (switching the prediction result to be selected) to the additional circuit 10.
Output to 5.

The data selector 104 sends the prediction result selected by the identification code 108 to the backup memo IJ103A to 103.
D and outputs it to the additional circuit 105.

The addition circuit 105 adds an identification code 108 and a predictor change code 109 to the selected prediction result, and outputs the prediction result 110 in units of the constant number of pixels to the encoder 106. The prediction result 110 is encoded by the encoder 106 and output as a code output 107.

The code format of the prediction result 110 in this case is shown in FIG.

Here, the prediction results 200A and 200B indicate the prediction results in units of the constant number of pixels. In the prediction result 200A, the predictor switching code 201A is "1" and the predictor 1 in FIG.
01A to 101 represent switching, and the identification code 202A at this time represents the predictor. In this example, four predictors are used, so 00″, @01″
, 110" and "11" pits 110 turns. The predictor switching code 201B in the prediction result 200B is "O", indicating that the predictor is not switched. In other words, the prediction result 200A This shows that the same predictor is used.In this case, the identification code 202
B is "00".

In this embodiment, the number of predictors is four, but it goes without saying that a similar configuration is possible when there are five or more predictors.

Effects of the Invention As described above, the present invention adds the identification code of the predictor and the predictor switching code to the prediction result, sets the predictor switching code to "1" only when the predictor is switched, and adds the prediction to the identification code. By outputting a value corresponding to the predictor and setting both the predictor switching code and identification code to "0" for other cases, it is possible to minimize the division of "0" codes in the run-length code of the prediction result. , the overall encoding efficiency can be improved.

[Brief explanation of the drawing]

The first part is a block wiring diagram of a predictive encoding device according to an embodiment of the present invention, FIG. 2 is a conceptual diagram showing prediction results by the same device, and FIG. 3 is a circuit block diagram of a conventional adaptive predictive encoding method. be. 101A to 10ID...Predictor, 1o2 river most used prediction error selection circuit, 103A to 103D...Buffer memory, 104...Data selector, lo5...Additional circuit, 106...Encoder.

Claims (1)

[Claims] A plurality of predictors perform prediction in units of a certain number of pixels from the value of the predicted pixel in a combination pattern of values of a plurality of reference pixels existing around the predicted pixel, and a prediction error of the prediction result of each of the predictors is calculated. a selection circuit that counts and selects only the predictor with a small prediction error; and a selection circuit that adds and encodes an identification code indicating which of the plurality of predictors the selection circuit has selected to the prediction result of the predictor. and a second encoding means that adds and encodes a predictor switching code indicating switching of the predictor to the identification code,
A predictive encoding device that performs run-length encoding on the prediction result.