JPH0832040B2 - Video signal encoder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a moving picture signal encoding apparatus.

(Prior Art) When a surrounding frame difference is small, which is often used in conventional interframe coding, and when only one point has a large amplitude, it is regarded as an independent significant pixel, that is, an independent point, and is removed. The independent point removal was performed in the inter-frame difference feedback loop as shown in FIG.

(Problems to be Solved by the Invention) Since the conventional removal of the significant pixels (noise component) isolated from each other is performed in the inter-frame difference feedback loop, the feedback error is always included and the moving image In many cases, the contours of the image were contaminated by insects and left on the screen for a long time, which was noticeable as a deterioration in image quality. An object of the present invention is to provide a moving image capable of performing an isolated point removing apparatus which removes the influence of a feedback error by removing an isolated point outside an inter-frame difference feedback loop as shown in FIG. It is to provide a signal encoding device.

(Means for Solving the Problem) In a moving picture signal coding apparatus for coding a signal using inter-picture correlation of a moving picture signal, one screen of a first moving picture signal which is an input is stored. A frame memory, a subtracter for generating a first difference signal from the output of the frame memory and the first moving image signal, and a predetermined difference between the first difference signal and a difference value in the vicinity thereof. Whether or not it is within the range is determined, and when it is within the range, the first difference signal is output as it is. When it is not within the range, it is obtained using a certain fixed value or the difference value in the vicinity. A comparison / determination circuit that outputs a second differential signal that has been replaced with a predetermined value, a delay circuit that generates a second moving image signal that has a delay adjusted input or output of the frame memory, the second differential signal and the First An isolated point removing circuit including an adder for adding the second moving image signal to obtain a third moving image signal, and the third moving image signal output from the isolated point removing circuit are input. It is composed of an interframe encoder that performs encoding.

(Operation) Since the conventional isolated point removal is performed in the inter-frame difference feedback loop, significant information isolated and generated in the contour portion is determined to be an isolated point and removed, so that an error occurs at that point. The error is generated, and the image quality is deteriorated because the contour portion of the image is contaminated and remains due to the action of the inter-frame difference feedback loop.

The independent point removal according to the present invention occurs when the isolated point removal is performed in the conventional inter-frame difference feedback loop by using the inter-frame difference obtained without forming the feedback loop as shown in FIG. It is possible to remove dirt on the screen at the contour portion of the moving image due to the influence of the feedback error and remove isolated points without image quality deterioration.

As shown in FIG. 1, the independent point removing circuit of the present invention calculates a difference signal between screens for an input moving image signal without forming a feedback loop with a frame memory and a subtractor. When the comparison determination circuit determines the significant difference with respect to this difference signal and the pixel is determined to be significant, the signal indicating the presence or absence of the determined significant difference in the vicinity of the pixel is used as the reference pixel for the current pixel. Is determined to be an isolated significant pixel.

Next, the determination of isolated points will be described by taking the reference pixel states of A to F in FIG. 3 as an example. The shaded area in FIGS. 3A to 3F is the current pixel (the pixel which is about to be judged for isolated point removal). 1 in the reference pixels is a significant pixel (that is, a pixel whose frame difference value is larger than the threshold value)
And 0 is an insignificant invalid pixel. 1 if the current pixel is 1 (significant pixel) and the reference pixel state is A, B, C
Since the current pixel has a high correlation with the reference pixel because they are strongly connected to each other, it is determined to be a significant pixel. When the reference pixel state is D, E, F, the one pixel is weakly connected and the current pixel has a low correlation with the reference pixel, so it is determined that the current pixel is isolated, and the pixel is determined as an independent invalid pixel.

Return to FIG. When the pixel is determined to be a significant pixel that is not isolated, the comparison / determination circuit outputs the difference signal corresponding to the pixel as it is. When the pixel is determined to be an isolated invalid pixel, the difference signal corresponding to the pixel is replaced with a certain fixed value, for example, zero, and is output. Further, the difference signal corresponding to the pixel determined to be an invalid pixel in the significant difference determination is also replaced with a certain fixed one value and output. Then, the difference signal output from the comparison / determination circuit is delayed by the adder and the output of the frame memory is delayed, and the output of the comparison / determination unit and the moving image signal in phase are added, and the moving image signal with isolated points removed is output as the output. It is given to the interframe encoder. In this way, if isolated point removal is performed without forming a feedback loop outside the coding loop, it is not affected by the feedback error, so that stains remaining on the contour portion are eliminated. Further, the difference value itself can be used as the reference pixel shown in FIG. For example, the average value of the surrounding difference values is compared with the difference value of the current pixel, and if the difference is within the defined range, the difference value of the current pixel is used as it is, and if it is outside the range, the average value of the current pixel is calculated. A method of replacing with a difference value can also be used.

(Example) The Example of this invention is described in detail with reference to drawings. FIG. 4 shows an embodiment of the present invention. Input video signal is a line
It is supplied to the frame memory 1 and the subtractor 2 via 101. The frame memory 1 stores the input moving image signal as 1
The frame time is delayed and supplied to the subtractor 2 and the delay circuit 4. The subtractor 2 subtracts ba from the input moving image signal b given by the line 101 and the moving image signal a delayed by one frame in the frame memory 1 and outputs a difference signal. The difference signal of the output of the subtractor 2 is
It is supplied to the comparison / determination circuit 3. The comparison / determination circuit 3 first determines the significant difference of the difference signal supplied from the subtractor 2. Then, when the significant difference signal is determined to be a significant pixel, it is determined whether or not the significant pixel is isolated according to the rule already described. When the significant pixel is not the isolated point, the difference supplied from the subtractor 2 is determined. When the signal is output as it is and the pixel is an isolated significant pixel or a pixel determined to be an invalid pixel by the significant difference determination, the difference signal supplied from the subtractor 2 is set to a certain fixed value, for example, zero. Replace and output. The configuration of the comparison / determination circuit 3 will be described in detail later. The output of the comparison / determination circuit 3 is supplied to the adder 5. The delay circuit 4 delay-adjusts the moving image signal supplied from the frame memory 1, and supplies the moving image signal matched with the phase of the output signal of the comparison / determination circuit 3 to the adder 5. The adder 5 adds the difference signal supplied from the comparison / determination circuit 3 and the moving image signal supplied from the delay circuit 4 and outputs a moving image signal with independent points removed.

The output of the adder 5 is supplied to the subtractor 6 of the interframe encoder as the output of the isolated point removing circuit. The subtractor 6 subtracts the moving image signal from which the isolated point is removed supplied from the adder 5 of the independent point removing circuit and the prediction signal supplied from the frame memory 9 to generate a difference signal. The difference signal output from the subtractor 6 is supplied to the quantizer 7. The quantizer 7
The difference signal supplied from the subtractor 6 is quantized and added to the adder 8
Supply to. It also outputs as an interframe encoder output via line 701. The adder 8 adds the difference signal supplied from the quantizer 7 and the prediction signal supplied from the frame memory 9 to generate a locally decoded signal. The locally decoded signal generated by the adder 8 is supplied to the frame memory 9. The frame memory 9 delays the locally decoded signal supplied from the adder 8 for one frame time and supplies it to the subtractor 6 and the adder 8 as a prediction signal.

Next, the comparison / determination circuit 3 will be described in detail with reference to FIG. The difference signal supplied from the subtractor 2 is given to the significant difference determiner 301 and the delay circuit 304 of the comparison and determination circuit 3. The significant difference determiner 301 makes a significant difference determination of the difference signal with a predetermined threshold value. When the difference signal of a pixel is larger than the threshold value, it is determined to be significant, and when the difference signal is smaller than the threshold value, it is determined to be invalid. When it is determined that the difference signal of a pixel is significant, the output of the significant difference determiner 301 is set to 1. When it is determined that the difference signal of a pixel is invalid, the output of the significant difference determiner 301 is set to 0. The output of the significant difference determiner 301 is supplied to the memory 302. The memory 302 temporarily stores the 0 or 1 signal indicating the significant difference supplied from the significant difference determiner 301, and forms a reference pixel by this signal group. The memory 302 stores the third pixel according to the pixels near the current pixel.
When the reference pixel group as shown in the figure is formed in the memory, the current pixel and its reference pixel group are output. The output of the memory 302 is supplied to the comparator 303. Comparator 303
Determines whether or not the current pixel is an isolated significant pixel based on the current pixel and the reference pixel group supplied from the memory 302. For example, when the current pixel is a significant pixel and the reference pixel group is A, B, C in FIG. 3, that is, when the current pixel is a significant pixel and has a high correlation with the reference pixel, the comparator 303
Output of 1. When the reference pixel group is like D, E, F in FIG. 3, that is, when the correlation between the current pixel and the reference pixel is low, the output of the comparator 303 is set to 0. When the current pixel is an invalid pixel, the output of the comparator 303 is set to 0 regardless of the state of the reference pixel. The control signal output from the comparator 303 is supplied to the switch 305. The delay circuit 304 controls the delay corresponding to the delays of the significant difference determiner 301, the memory 302, and the comparator 303 with respect to the difference signal. Delay circuit 3
The differential signal delayed controlled in 04 is supplied to the switch 305. The switch 305 switches the differential signal supplied from the delay circuit 304 by the control signal supplied from the comparator 303. When the control signal supplied from the comparator 303 is 1, the switch 305 outputs the difference signal supplied from the delay circuit 304 as it is. Control signal is 0
In the case of, the output of the switching device is replaced with a predetermined fixed value, for example, 0, and then output. With respect to the isolated significant pixel and the invalid pixel thus isolated, the isolated point can be removed by setting the difference signal to zero. Changer 305
Of the comparison decision circuit 3, that is, the output of the comparison and determination circuit 3 is supplied to the adder 5 via the line 306.

The isolated point removing circuit having the configuration shown in FIG. 4 has been described above in detail, but the configuration shown in FIG. 6 can be adopted. Frame memory 1 in this case,
The subtractor 2, the comparison / determination circuit 3, the delay circuit 4, and the adder 5 are
The same thing as the embodiment of FIG. 4 can be used. Then, the input moving image signal is supplied to the frame memory 1, the subtractor 2 and the delay circuit 4. The frame memory 1 delays the input moving image signal by one frame time and supplies it to the subtractor 2. The subtractor 2 subtracts a−b from the input moving image signal b and the moving image signal a supplied from the frame memory 1 and supplies an output difference signal to the comparison / determination circuit 3. The comparison / determination circuit 3 makes the same determination as in the embodiment of FIG. 4 and supplies the output difference signal to the adder 5. The operation of the delay circuit 4 is similar to that described above, and the delay-adjusted moving image signal is supplied to the adder 5. Adder 5
Outputs the moving image signal with isolated points removed by adding the moving image signal supplied from the delay circuit 4 and the difference signal supplied from the comparison and determination circuit 3.

Next, another embodiment of the comparison / determination circuit 3 will be described. The differential signal at the input of the comparison / determination circuit 3 in FIG. 7 is supplied to the delay circuit 304 and the memory 302. Memory-302
3 temporarily stores the difference signal and forms the reference pixel state as shown in FIG. 3 by the difference value. The memory 302 outputs the difference signal of the current pixel and the surrounding difference signal which is the reference pixel when the reference pixel state is formed in the memory by the difference signal around the current pixel. The output of the memory 302 is supplied to the comparator 303 and the filter circuit 307. The filter circuit 307 performs spatial filter calculation using the differential signal supplied from the memory 302, and supplies it to the switch 305. Comparison determiner 303, from the difference signal of the current pixel and its surrounding pixels supplied from the memory-302, calculates the average value of the difference signal around the current pixel, and compares it with the difference value of the current pixel, If the difference is within the specified range, the comparator 303
1 is output, and when the difference is outside the defined range, the output is set to 0. The control signal output from the comparator 303 is supplied to the switch 305. The delay circuit 304 compares the input differential signal with the comparison / determination unit 303 and the filter circuit 307.
Gives a delay equivalent to the delay of. The delayed differential signal output from the delay circuit 304 is supplied to the switch 305. Switch 3
05 selects the difference signal supplied from the delay circuit 304 when the control signal supplied from the comparator 303 is 1, and selects the filter output value supplied from the filter circuit 307 when the control signal is 0. . The output of switch 305 is line 3
It is supplied to the adder 5 via 06.

(Effect of the Invention) As described in detail above, by performing isolated point removal without forming a feedback loop outside the interframe coding loop, a moving image generated by the influence of a feedback error of the interframe feedback loop Noise can be removed by removing stains on the contour portion. Thus, when the present invention is put to practical use, its effect is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a diagram for explaining a conventional method, FIG. 3 is a diagram for explaining the principle of the present invention, FIG. 4, FIG. 5, FIG. FIG. 7 and FIG. 7 are views for explaining an embodiment of the present invention. In the figure, 1 ... Frame memory, 2 ... Subtractor, 3 ... Comparison determination circuit, 4 ... Delay circuit, 5 ... Adder, 6 ... Subtractor, 7 ... Quantizer, 8 ... Adder, 9 ... Frame memory, 301 ... significant difference determiner, 302 ... memory, 303 ... comparator, 304 ... delay circuit, 305 ... switcher, 307 ... filter circuit.

Claims (1)

[Claims] 1. A moving picture signal coding apparatus for coding a signal using inter-picture correlation of a moving picture signal, and a frame memory for storing one screen of a first moving picture signal which is an input. Output of frame memory and the first
A subtractor for generating a first difference signal according to the moving image signal, and comparing the first difference signal with a difference value in the vicinity thereof to determine whether or not the difference value is within a predetermined range. When it is not within the range, it outputs the first difference signal as it is, and when it is not within the range, it outputs the second difference signal which is replaced with a certain fixed value or a value obtained by using the difference value in the vicinity. A comparison / determination circuit, a delay circuit for generating a second moving image signal in which the input or output of the frame memory is delay-adjusted, the second difference signal and the second moving image signal are added, and a third moving image signal is added. The adder for obtaining the moving image signal of 1), the isolated point removing circuit, and the interframe encoder for inputting and encoding the third moving image signal output from the isolated point removing circuit Video signal characterized by No. encoder.