JPS6052167A - Adaptive forecasting coder - Google Patents

Abstract

PURPOSE:To improve forecasting effect and also to eliminate the need for a mode code by selecting a forecasting value obtained from plural forecasting devices from the degree of failure in the forecasting of a forecasting error signal after scanning. CONSTITUTION:A sampling value X and the output of line memories 2a, 2b1- 2bl are added properly to the forecasting values 3a1-3an respectively and forecasting values P1-Pn are outputted. Exclusive OR circuits 4a1-4an adding each forecasting value and the sampling value X output forecasting error signals Y1- Yn and give the signals to a forecast selecting circuit 5 and a selector 6. Then the selecting circuit 5 selects a forecast error signal having the least failure in the forecasting among the picture elements scanned already and outputs a selection signal M. The selector 6 selects the forecasting error signal Y according to the selection signal M, transmits it to a coder 7, where the signal is coded. Thus, the forecasting effect is improved and also the mode code is made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adaptive predictive coding device used for predictive coding of halftone photographs representing halftones using black and white binary image signals used in newspapers, etc. .

Conventionally, this type of adaptive predictive coding device compares the number of mispredicted pixels of a plurality of prediction error signals in a certain block unit, such as the prediction means shown in Japanese Patent Application Laid-Open No. 55-41080. However, there is a method of selecting a prediction error signal with a small number of prediction errors. This method has the disadvantage that the prediction effect is not sufficient if it is better to change the prediction method in the middle of a block, and the data compression rate is not sufficient because a mode code is required to indicate which prediction method was selected. was there.

An object of the present invention is to eliminate the drawbacks of the conventional prediction means described above, and to provide an adaptive predictive coding device that has a high prediction effect and does not require a mode code.

The adaptive predictive coding device of the present invention calculates a plurality of predicted values P1sPl..., Pn for a sample value X of a pixel A plurality of pixels Ylt)' having the same phase relationship as
l..., ym and means for generating the sample values of the neighboring pixels; and the sample value X and the plurality of predicted values Pl.
y P2t Pat P4y "' v pn means for obtaining prediction error signals y, t y, t..., Yn, and prediction error signals Y1.Y, . . . for already scanned pixels.
... means for comparing the degree of prediction error of sYn; means for generating a selection signal based on the comparison result; and means for generating the plurality of prediction error signals y, t y according to the selection signal.
, 1, . . . , Yn, it is composed of means for obtaining one prediction error signal Y, and means for encoding the prediction error signal Y.

The adaptive predictive coding device of the present invention includes a sample value X and a plurality of predicted values P1. From the prediction error signals Y, , Y, . . . , Yn obtained from P2*..., Pn, predicted values P1*P2 . ...The prediction error signal Y included in the prediction error signal Y is selected by comparing the degree of prediction error of ePi'l and selecting the prediction error signal Y with less prediction error.
Since the number of predicted values is small and a mode code indicating which predicted value is selected is not required, the overall amount of information after encoding is reduced and the method has the effect of being compatible with international standard MH encoding.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of a reference pixel of a predictor used in an adaptive predictive coding apparatus of the present invention and a pixel used for comparing prediction errors of a prediction error signal. In addition, the first
The figure targets a 45° diagonal halftone image. In FIG. 1, the distance D (D=10 here) represents the period of the halftone dot, and the pixels that have the same phase relationship (on the two-dimensional mesh periodic pattern of the image) with the sample value X of the pixel X are: Y1t
Y2t...

It is y. One way to predict the sample value Sample value Y of pixel y1 and sample value B of its neighboring pixels blp cl, dl* glp )11
It is conceivable to make a prediction from l t ct l 'ff, tG, , H,. This is the prediction method used in the predictor 3a1 in the block diagram (FIG. 2) showing one embodiment of the present invention. Another method for predicting the sample value X is to use the neighboring pixels ay be Cs dt
Sample value A of L g.

B, C, D, F, G, sample value Y of pixel y2 diagonally separated by halftone period, and its neighboring pixel b2°C2
Sample values of s dl g2+ h2 B,, C,, D,,
It is also possible to predict the sample value X from G,, H,. This prediction is performed by the predictor 3al shown in FIG. 2(4).

Still another prediction method is a method in which the sample value of the pixel Ymv Y+e . . . Also, pixel i1s izt kss ii
* j6p 16tIcy lay IIHjiffy
l1ls IHy 111+ 114p 1llllt
FIG. 2 (2) is a block diagram showing the first embodiment of the present invention, and is an example of the configuration when the reference pixels shown in FIG. 1 are used. In the figure, a sampled and binarized image signal is applied to terminal 1.

Assuming that the sample value applied to the terminal 1 at the time of interest is X, this sample value X is stored in the line memory 2a.

Predictor 3a1.3a2. ..., supplied to 3aH. The line memory 2a delays the signal by about one line, and more precisely, the delay amount for one line is H (= 8000
sample), the output terminal will have (H-6)=79
A signal delayed by 94 samples is obtained. The line memories zb, 2btt..., 2b7J each delay the input signal by one line, and each output terminal has a delay of 1°2, . . . compared to the output terminal of the line memory 2a.
...! A line-delayed signal is obtained. Prediction 53al
, 3a2. ..., 3aH is composed of a shift register and a read-only memory (ROM)9, and as described later, using the combination shown in FIG. 1 as reference pixels, the predicted values Pl, ats...・.

Output PR. The predicted values P1tPle...tPn are then sent to exclusive OR circuits 4a1g 4a2. ..., 4a
Exclusive OR is taken with the sample value X at H, and the prediction error signal y
1j y2j...

yn is obtained and input to the prediction selection circuit 5 and the selector. The prediction selection circuit 5 selects pixels a, b, and c that have already been scanned, as shown in an example in FIG.

``F'*gy 15~its prediction error signal Y,,
Y2. ....

Compare the number of prediction errors included in Yn, select the prediction error signal (■) with the least prediction error among the pixels that have already been scanned, and output a selection signal (b) to select it as the prediction error signal for the current pixel. In the selector 6, the selection signal (
A prediction error signal Y can be obtained pixel by pixel according to the following method. Predictor, the difference signal Y is then encoded in an encoder 7 (eg a conventionally used encoder such as a run-length encoder),
It is output as a code C from the output terminal 8.

In addition, when encoding the prediction state signal in addition to the prediction error signal in the encoding of the encoder 7, as shown in FIG.
This can be achieved in the second embodiment of the invention shown in .

That is, the prediction state signal is a signal used to statistically examine the prediction probability for each reference pixel pattern in advance and to group the prediction error signals according to the magnitude of the prediction probability. For example, when there are two predicted states, patterns are divided into patterns with a predicted accuracy probability of 0.95 or more and patterns with other patterns. In FIG. 2(B), the predicted state signal S1v S2t ``'p sn, like the predicted value P1 t' B2 t ''' t Pn, is generated by a shift register and a ROM. g 3a'21 . . In the encoder 7', prediction state No. 48 S
For example, the prediction error signal is run-length coded using the . A run-length encoding method using such a prediction error signal and a prediction state signal is described in Japanese Patent Application Laid-Open No. 55-41080.
It is stated in the No.

FIG. 3 (4) shows the predictor 3a used in FIG. 2 (4).
FIG. terminal 10
and 11 are the current scan line and the previous scan line, i.e., FIG.
) is applied to the output signal of the line memory 2a.

Letting the sample value applied to the terminal 10 be
Pixel fy in FIG.
gy)11. ) '1 and gl sample values F, ' G,
H□.

Y, and C1 are obtained. A signal obtained by delaying the standard X by (H-6)=7994 sample times is applied to the terminal 11, but the signal is further delayed by 4 sample times by the shift register 12d. Shift registers 12c, 12f.

and 12g, 1-4 and 11-13 samples time delayed, pixels d, c, b in FIG.

The sample values of a, dI, (, and S, C, B, A, D
,.

C1 and B1 are obtained. Sample values of reference pixels obtained in this way A, B, c, D, F, G, B1°c,
t Di toll Hl and Y, I'tOM
13 as an address, and the aforementioned predicted value P1 is generated at its output terminal 14. The predictor 3a2 also uses the neighboring pixel ay bt ct dt fy g of the pixel X as the reference pixel, and the pixel y2 and its neighboring pixel b2° C2y d2y gzt h, which are diagonally separated by the period of the halftone dot. It can be implemented with a circuit configuration using a shift register and a Q-M.
et )'4*...

Predictor 3a3.3a4 when using ym,...
3an can also be implemented with a similar circuit configuration.

Above, we have described an example in which only one pixel having the same phase relationship with pixel X is selected as the reference pixel of the predictor, but multiple pixels having the same phase relationship with pixel X are simultaneously used as reference pixels. can.

For example, pixel 09g near X shown in FIG. 1 as a reference pixel, yly)')y, which has the same phase relationship as
Sample value of t gs By Cy Gy Ylt C1y
()is Yt! t C2t C2y YIC3yG3
Of course, this includes a predictor using a .

Figure 3 (J3) shows the predictor 3 used in Figure 2 (B).
FIG. 8 is a diagram showing an example of an embodiment of 8'1. 3rd in the figure
The difference from the predictor 3al in FIG. 4 is that the predicted state signal S
.

The difference is that a ROM 13' that generates . The predicted state signal S is a predicted value P.

Similarly, several types of papers are statistically evaluated in advance.

FIG. 4 is a diagram showing an embodiment of the prediction selection circuit 5 used in FIG. 2 (4) and FIG. 2 ω). terminal 20a
l, 20a2. ..., 20an are prediction error signals Y□, Y7 . . . obtained from the results of the respective predictors.・
..., Yn is applied. The prediction error signal Y1 applied to the terminal 2081 is delayed by a delay circuit 21a1 composed of a line memory and a shift register, and the prediction error signal Y1 is delayed by a delay circuit 21a1 which includes a line memory and a shift register.
I! 1+41°, and the prediction error signal Y, , □
l, Y, ;2. Ylt,,Yl,i'-.

? Given Y,, i, i', Yl, H,:',, Ylt
, 1 and YI+g are ROM.

1'l 19 Prediction error measurement circuit 2 consisting of an adder and a register
2a l. Prediction deviation measurement circuit 22a.

Now, the already scanned pixel "B~, +19y at
Prediction error signal Y□9 of bv Ctd+'+g. ~Y
, , , , Y,.

+10 o+t y, jl) νYIg og Y@y dH
The sum of the mispredictions of YtH41 and Y1tg is counted. In other words, the total prediction error for the previous pixel is Y,
i, Yl, i,, Y,.

Add 1'1 jiq missing YIj north and write Y,, jH* y,,
By subtracting Y, , i from i, νYYt, the total sum of prediction errors for the original pixel can be found. Similarly, the prediction error signal Y,.

Y3. , Yn are the delay circuits 21a2, 21a3 .
- Delayed by , 21an, prediction error measuring circuit 22a
2.22a3°..., 22al counts the number of prediction errors and inputs it to the comparison circuit 23. Comparison circuit 23
Now, the prediction error signals YI, Y2 . ..., already scanned pixels I5 to 1Ili for Yn, at bt C
The numbers of prediction errors of t de ee f+ g are compared with each other, and a selection signal for selecting the prediction error signal Y for the current pixel X is outputted from the terminal 24 .

Although the prediction selection circuit of the present invention has been described above, it goes without saying that these do not impose any limitations on the present invention. For example, when comparing the degree of prediction error,
Of course, it is possible to use the method of adding a weight proportional to the distance from the current pixel, and the range of the prediction error signal to compare the degree of prediction error has already been scanned. Of course, it is possible to limit the pixels to the area corresponding to the size of a certain halftone dot.

FIG. 5 is a diagram showing an embodiment of the delay circuit 21a□ used in FIG. 4. The prediction error signal Y is connected to the terminal 20aI.
1 is applied. The line memory 30a1 delays the prediction error signal by about one line. To be exact, if the delay amount for one line is H (= 8000 samples), the output terminal has a delay of (H-2) = 7998 samples. A signal is obtained. Also, line memory 30b,, 3ob,,
30b and 30b respectively delay the input signal by one line, and each output terminal has a delay of 1. 2. A signal delayed by 3 lines is obtained. Shift register 31a1.31a2゜31a, and 31
a4 is a shift register with time delays of 1 to 7 and 4 to 7 samples, respectively, and pixel 11ν12νI in FIG.
3νf4y jl tllB prediction error signal for iso and g, Y191. Yl2. Yl, i3゜1 Y,, 1; Ylti, , Yl, ,,, Yl, i
and Y++g 1'l M9 circle is obtained, terminal 32al, 32a2.32a3.32
a4.32a6゜32a6.32a7. and 32a6
A lot of output is generated.

FIG. 6(4) is a block diagram showing an embodiment of an adaptive predictive decoding device that decodes a signal encoded by the first embodiment of the adaptive predictive coding device of the present invention.

In the figure, the code applied to the terminal 40 is transmitted to the decoder 41
is decoded into a prediction error signal Y. The prediction error signal Y is sent to the exclusive OR circuit 4a□+4a2. ..., 4aH, predictor 3al, 3a2. ..., the predicted value PIyP2. which is output more than 3an. ..., Pn, and the decoded signal X1. X2. ..., generates Xn. The selector 6 selects the decoded signals x', , x2 . ....

Select the decoded signal X based on Xn. Exclusive OR circuit 42
are predicted values P, , P2. ..., generate prediction error signals y, t y2j...+yn' from Pn and decoded signal X,
It is input to the prediction selection circuit 5. Other line notes! J
2a.

2bl j 2b! e =', 2bm, predictor 3al H3a2 y..., 3aHN The prediction selection circuit 5 has exactly the same circuit configuration as that in FIG. 2 (4), which is the first embodiment of the adaptive predictive encoder of the present invention. does the same thing. Moreover, the predictors 3a1, 3a2. ..., 3
As aH, the predictor shown in FIG. 3 (4) is used.

FIG. 6(B) is a block diagram showing an embodiment of an adaptive predictive decoding device that decodes a signal encoded by the second embodiment of the adaptive predictive coding device of the present invention.

The difference between the figure and FIG. 6(4) is that the decoder 41' performs run-length decoding of the prediction error signal using the prediction state signal, and the predictors 3a'1 t 3a'2 y...
, 38'. As shown in Figure 3 (g)), a device that generates a prediction error signal and a prediction state signal is used, and a device that selects a decoded signal and a prediction state signal is used as the selector 6'. It is a point.

As described above, the present invention uses a plurality of predictors and selects the predicted value obtained by the predictors based on the degree of prediction error of the scanned prediction error signal. This is an adaptive predictive coding device that has a large side effect and can be applied to international standard MH encoders.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the reference 14α pixel of the predictor used in the present invention and the pixel used to compare the prediction error of the prediction error signal, and FIG. 2 (4) and FIG. 2 (B) are A block diagram showing the first and second embodiments of the present invention,
3(3) and 31ffl(B) are block diagrams showing first and second examples of the predictor used in the present invention, and FIG. 4 is a block diagram showing an example of the prediction selection circuit used in the present invention. FIG. 5 is a diagram showing an example of a delay circuit used in the present invention, and FIG. 6 (4) and FIG. FIG. 2 is a block diagram showing first and second embodiments of the present invention. In the figure, reference numeral 21 *' 2b+t 2b2
p ”' e 2bm-+2bm and 30a1.3o
b, y 3ob,, aob3 is line memory, reference number 3”I t 3a2t ”’, 3an y 3a
'is 3a'2. ``'v3a'. is a predictor, reference numerals 4a1y 4a2..., 4an and 42 are exclusive OR circuits, reference numeral 5 is a prediction selection circuit, reference numerals 6 and 6' are selectors, reference numerals 7 and 7 ' is the encoder, reference numbers 12a, 12b, 12c. 12d, 12e, 12f, 12g, 3
1aI, 31a2.31a3. and 31a4 are shift registers, reference numbers 13 and 13' are ROMs, reference numbers 21al, 21a2 . −． 21aH-1 and 21an are delay circuits, reference numbers 22a, 22az+
..., 22a, 1. -□ and 22a, 1 represent a prediction error measuring circuit, and reference numerals 41 and 41' represent a decoder. t (embedding patent attorney inner layer hunting,'s,):'X゛\-[ [heart--++-+------lha 10 Capturing Satoru Figure 3 (A) j○1 73 Figure (B) O1 Figure 74

Claims (1)

[Claims] In an adaptive predictive encoding device that encodes a halftone photograph, a plurality of predicted values Pat Pt5 for a sample value X of a pixel
-, Pn (n is a positive integer), and the pixels y1゜yl, ... t y in the vicinity of the pixel X and the plurality of pixels y1゜yl, ... ty that have the same phase relationship with the pixel X on the two-dimensional mesh periodic pattern of the image
n1' (In is a positive integer) and means for generating the sample value of its neighboring pixels, and the sample value X and the plurality of predicted values P1yP! ,...yPn, prediction error signal Y,
, Y, . . . tYn, and a means for obtaining prediction error signals Y, , Y, . means for calculating the degree of prediction error of t...tan, and means for obtaining one prediction error signal Y from the plurality of prediction error signals Y, Y, . . . , Yn based on the calculation result. and means for encoding the prediction error signal Y.