JPH02112394A - Moving image signal smoothing processor - Google Patents

Abstract

PURPOSE:To reduce block distortion without lowering the resolution of a picture by executing the smoothing filter processing of different intensity by the coarse and fine block of an encoding parameter and by a picture element position and further changing the intensity of a smoothing filter in response to the rough of the encoding parameter. CONSTITUTION:To a moving image which is encoded by block unit processing, the smoothing filter processing of the different intensity is executed by the coarse and fine block of the encoding parameter and by the picture element position. Further, the rough of the encoding parameter is decided by a block deciding circuit 107 and in response to such a decided result, the intensity of a smoothing filter 111 is hourly changed. Thus, the block distortion of an encoding and forecasting picture can be widely reduced due to the smoothing filter 111 and simultaneously, the picture at the time of decoding can obtain the large improvement of picture quality on vision as well. The lowering of the resolution can be reduced wholly in the encoding and forecasting picture and the picture at the time of the decoding. Then, the picture to be visually easily observed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device that performs smoothing processing on a moving image signal input to a moving image encoder based on block unit processing, and in particular, The present invention relates to a moving image signal smoothing processing device that can suppress deterioration in overall resolution of a signal and reduce deterioration in image quality due to encoding distortion.

[Conventional technology]

In order to perform high-efficiency encoding of image signals, moving image encoding/decoding systems and devices that adaptively encode mainly block by block are widely used. At this time, there are two ways to remove block distortion caused by encoding: - Decoding on a boat and using a smoothing filter with the same characteristics on the entire screen for good image signals, or using it only on block boundaries. Are known.

[Problem to be solved by the invention]

In the conventional video encoding device described above, the predicted image signal to be encoded is the same image as the decoded image on the receiving side, and the distortion due to encoding is visible on the receiving side, resulting in visual deterioration of image quality. is often accompanied by In particular, in the case of adaptively encoding and decoding on a block-by-block basis, (b
), encoded predicted images and decoded images often have block distortion due to encoding. FIG. 8 is a diagram for explaining problems in conventional video encoding devices, and (a) shows an input image defect signal expressed with time on the horizontal axis and amplitude on the u axis. , (b) shows encoded predicted images. And (c) in (b) indicates block distortion due to pre-encoding.

Since such front block distortion is distortion that is not familiar to ordinary TV screens, there is a problem in that it causes a fatal visual quality deterioration. Therefore, conventionally, as a general method, a smoothing filter (post filter) with the same characteristics is used for the entire screen of the decoded video image, which has the problem of often reducing the overall screen resolution. was there.

[Means to solve the problem]

The moving picture signal smoothing processing device of the present invention is a device that performs smoothing processing on a moving picture signal input to a moving picture encoder based on block unit processing. A circuit that determines whether the encoding is a block, a memory circuit that stores encoding parameters, a circuit that selects encoding parameters to be written to this memory circuit according to a motion/static block identification signal, and a circuit that determines whether the encoding parameters are coarse or fine. a determining circuit, a counting circuit that counts the position of a pixel, and a determining circuit that determines a pixel area to be divided by referring to the pixel count value in this counting circuit, the surrounding pixel area, and the coarse determination result of the encoding parameter. , a circuit that controls the smoothness according to the roughness of the encoding parameter in each block for each pixel region determined by the determination circuit, and a smoothing filter process of the moving image signal according to the signal that controls the smoothness. It has a circuit that performs this.

[Effect]

In the present invention, smoothing filter processing with different strengths is applied to each coarse block and pixel position side of the encoding parameter on a video* to be encoded by block unit processing, and further, according to the coarseness of the encoding parameter. The strength of the smoothing filter is changed over time.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 101m is a nonlinear level converter, and 101m is a nonlinear level converter.
b is a frame memory, which is built into the noise reducer 102. 103 is a scan converter, 104
is a moving/static block determining circuit, and this moving/static block determining circuit 104 is a circuit that determines whether a block to be encoded is a moving block or a static block.

105 is a pixel address counter which is a counting circuit that counts the position of a pixel, and 106 is a determination unit that determines a pixel area to be divided by referring to the pixel count value in this counting circuit, surrounding pixel areas, and coarse determination results of encoding parameters. A pixel area discriminating circuit 107 is a circuit that determines whether the encoding parameters are coarse or fine; 108 is a block determining circuit that determines whether the encoding parameters are coarse or fine; and 108 is a circuit that determines the encoding parameters for each block in the pixel area determined by the pixel area discriminating circuit 106. 109 is a scan converter; 110 is a delay circuit; 111 is a circuit for smoothing the moving image signal according to a signal for controlling the smoothness; A smoothing filter which is a circuit, 112 is an encoder, 113 is a buffer memory, 11
5 is a memory circuit for storing encoding parameters, and 114 is a selector which is a circuit for selecting encoding parameters to be written into the memory circuit 115 in accordance with a motion block identification signal.

2 and 3 are time charts for explaining the operation in FIG. ) shows the effective pixel cuff/), and (d) shows the moving/static block identification signal. In addition, (-) in FIG. 3 indicates block synchronization, (b) is a pixel run), (e) is a parameter identification signal, (d) is a pixel area identification signal, (e
) shows the filter characteristics.

FIG. 4 is a diagram for explaining the present invention in detail, where (-) indicates input image No. 1 after smoothing filter processing, with time on the horizontal axis and amplitude on the vertical axis; (b) indicates a coded predicted image obtained by smoothing filter processing.

5 and 6 are diagrams for explaining the method of dividing a pixel area according to the present invention. In FIG. 5, (b) shows a block with fine parameters, and e shows a block with coarse parameters. Pn: parameter, fine when n×2, coarse when n≧2. In addition, the pixel area■
The strength of the filter characteristics for ~■ is ■〈■ku■ku■ku■
It is.

FIG. 7 is a diagram for explaining the filter processing control method according to the present invention, where Pk indicates the coarsest parameter and Po indicates the finest parameter. And Pn: parameter, n=0~.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIGS. 2 to 7.

In FIG. 1, input signal 1 is first input to noise reducer 102. In FIG. This noise reducer 102
So input 6 signal 1 and frame memo 17101b
The differential image signal 2 is inputted to the nonlinear level converter 101m, and nonlinear conversion is performed to bring the small noise level of the difference as close to zero as possible. At this time, encoder 112
The output of the nonlinear level converter 1011 is set to zero according to the frame thinning signal 8 output from the nonlinear level converter 1011, and input of a new image is stopped. The non-linearly converted differential image signal 3 is added to the image signal 4, and the input signal 5 resulting from the addition is sent to the frame memory 101b again.
Enter K1. Further, this input image signal 5 is input to a delay circuit 110. Furthermore, the differential signal 3 is input to the scan converter 103.

This scan converter 103 first performs valid pixel determination on the TV line scan differential image signal 3. Then, if the pixel is less than or equal to the threshold Tu, it is determined to be an invalid pixel (0), and if it is larger than the threshold Tu, it is determined to be a valid pixel (1), and this valid/invalid pixel determination result is converted to line scanning in block units to be valid/invalid pixel. The invalid pixel identification signal 9 is output together with the block synchronization signal (IT No. 11) during block scan conversion as shown in FIG. , the valid/invalid pixel identification signal 9 is added for each block using the block synchronization signal 11 as a reset signal to calculate the number of effective pixels (see Fig. 2 (C)).And if the number of effective pixels is less than the threshold Tm If the block is larger than the threshold value Tm, it is determined to be a motion block (1), and a motion/static block identification signal 10 is determined.
(See Figure 2(d)). This dynamic block identification signal 10 is input to a selector 114 and an encoder 112. The block synchronization signal 11 is input to the pixel address counter 105, which outputs a pixel count value 12 indicating the position of the pixel within the block (see FIG. 3(b)). This pixel count value 12 is input to the pixel area determination circuit 106.

In this pixel area discrimination circuit 106, the pixel count value 12 and a parameter identification signal 14 (see FIG.
c)) to output a pixel area identification signal 13 which is an identification signal representing five pixel areas (see FIG. 3(d)).

This parameter identification signal 14 will be explained in detail below.

First, when the parameter identification signal 14 represents a block area with coarse parameters, it is determined whether the pixel to be subjected to filter processing is a boundary pixel or a pixel inside the boundary pixel based on the pixel count value 12, and as shown in FIG. Divide into ■ area or ■ area. In addition, when representing a block area with fine parameters, it is determined whether blocks with coarse parameters are adjacent by referring to the surrounding parameter identification signals, and if blocks with coarse parameters are adjacent, It is determined by the pixel count 12 whether it is the first pixel, the second pixel, or the inner pixel that is three or more pixels away from the block boundary, and the pixel is divided into a region of ■, a region of ■, a region of ■, and a region of ■. Furthermore, it is determined whether the pixel is a boundary pixel of mutually adjacent fine parameter blocks or a pixel inside thereof, based on the pixel count value 12, and the pixel is divided into a region (■) and a region (2). A pixel area identification signal 13, which is an identification signal representing the five pixel areas divided in this way, is input to a filter characteristic control circuit 108.

In this filter characteristic control circuit 108, when the encoding parameter is coarse, filter characteristics E and F (see FIG. 3(e) and FIG. 7) with strong blur are selected for the regions of ■ and ■ in the block, respectively. A slightly stronger filter characteristic D (see FIG. 3(e) and FIG. 7) is selected in the region. Furthermore, when the encoding parameters are fine, filter characteristic A (see FIG. 7) with weak blur is selected. That is, the filter characteristic control signal 16 for selecting the filter characteristic suitable for the roughness of the parameter as shown in FIG. )reference). This filter characteristic control signal 16 is transmitted to the scan converter 109.
In the block unit line scanning is converted to TV line scanning, and a filter characteristic control signal 1T is output to the TV line scanning layer in pixel units.

Then, in the delay circuit 110, the input signal 5, which is the noise reducer output image signal, is delayed by the time of the process in which the filter characteristics are determined, and the delay circuit output image signal 6 is input to the smoothing filter 111, and the filter characteristics are Smoothing processing is performed by switching the strength of the filter characteristic (characteristic coefficient) for each pixel region according to the control signal 17, and a smoothed filter output image flaw signal 7 is output.

The smoothing filter 111 in FIG. 1 performs smoothing processing by multiplying the surrounding pixels and the central pixel by a characteristic coefficient, and therefore requires a line mesh of at least 32 inches or more. And smoothing filter output 6
The signal T is encoded by the encoder 112 according to the motion block identification signal 10, the encoded compressed signal 20 is input to the buffer memory 113, and the encoded compressed signal 21 is read out at a constant transmission rate. The process waits until the buffer memory occupancy 22 output from the encoding expansion buffer memory 113 in the encoder 112 becomes equal to or less than the threshold Tf. At this time, a thinning signal 8 representing a frame that is not encoded is output, and thinning is performed in the nonlinear level converter 101a of the noise reducer 102. Then, before encoding, parameters are determined over a period of time for one frame, and encoding is performed in the next frame according to the determined encoding parameters 18. This encoding parameter 18 is input to the selector 114, and the past encoding parameter 1 is inputted according to the motion block identification signal 10.
9 (the parameter read from the memory circuit 115) or the current encoding parameter 18. When the moving/static block identification signal 10 is a moving block, the current encoding parameter 1B is selected, and when it is a still block, the past encoding parameter 19 is selected. The parameters 15 selected in this way are written into the memory circuit 115. Here, the parameters of a static block cannot be rewritten unless it becomes a moving block.

Parameter 15 is input to block determination circuit 107 and filter characteristic control circuit 108 . This block determination circuit 107 determines whether the parameter 15 is a fine parameter block or a coarse parameter block.

For example, assume that the parameter 15 is a valid parameter such as pn (n=ok). n is the judgment threshold T
When it is larger than p, it is considered a coarse parameter block. Further, when n is less than or equal to the determination threshold Tp, the block is determined to be a detailed parameter block. As a result of this determination, a parameter identification signal 14 representing coarse/fine parameters of each block is output.

In the above description, a case has been described in which the pixel area is divided into five parts, but it may be divided into two pixel areas as shown in (&) to (f) in FIG.

Alternatively, the pixel area may be divided into three pixel areas such as □□□) to (b). Furthermore, in FIG. 6 and (4) to (1) described below,
)) may be divided into four pixel areas.

According to the present invention, if the input moving image signal is an image with a block containing high-frequency components in the contour part, such as (,) in FIG. It is often determined that the moving block is a block, and encoding the moving block causes block distortion in the encoded predicted image (see (c) of (b) in FIG. 8). To make this coded predicted image visually smooth without block distortion, pixels at the boundary of the moving block where block distortion would occur, pixels located near that pixel, or pixels inside the block. When a smoothing filter process is performed to cut the high frequencies (see ``&'' in FIG. 4), an image with less block distortion can be obtained as shown in FIG. 4(b). More specifically, in order to create a visually smooth image with less block distortion in the encoded predicted image, pixels at the boundaries of blocks encoded with coarse parameters, pixels inside them, and blocks encoded with fine parameters. The characteristics of the smoothing filter are switched and used for each region of boundary pixels and pixels inside the boundary. In FIG. 5, when the parameter Pn (n=o~, where O is the finest and k is the coarsest) is PO and Pl, it is assumed that the block has a fine parameter. If it is coarser than Pl, it is assumed that the block has a rough parameter. As shown in Figure 7, characteristic coefficients are prepared such that the strength of the filter characteristics is characteristic A, characteristic B, characteristic C, characteristic E, characteristic F, and the areas in which these characteristics are switched are divided into the following five areas. shall be.

■ A pixel area inside a block boundary pixel in a block to be encoded with fine parameters, and a pixel area in a block to be encoded with fine parameters that is three or more pixels away from the boundary with a block to be encoded with coarse parameters.

■ A pixel area surrounding the boundary within a block to be encoded with adjacent fine parameters (excluding the area marked ■).

■ 2 from the boundary of the block encoded with coarse parameters
A pixel area within a block that is encoded using detailed parameters that are a pixel ahead or at least two pixels apart.

■ The pixel region inside the boundary pixel within the block to be encoded with coarse parameters.

■ Pixels at the boundary between a block encoded with coarse parameters and an adjacent block encoded with finer parameters, and pixel areas surrounding the boundaries within mutually adjacent blocks encoded with coarse parameters.

When a pixel to be subjected to filter processing is a pixel within a block to be encoded with coarse parameters, it is determined whether the pixel is a pixel at a block boundary or a pixel inside the block boundary, and the pixel is divided into a region (■) and a region (2). Also, when a pixel in a block is encoded with fine parameters, it is determined whether the moving block is adjacent by referring to the surrounding blocks, and if the block to be encoded with coarse parameters is adjacent, the block boundary is from 1
Determine whether it is the 1st pixel, the 2nd pixel, or the inner pixel that is 3 or more pixels away, and compare the ■ area, the ■ area, and the ■ area.
Divide into areas. Furthermore, it is determined whether the pixel is a pixel at the boundary of the block to be encoded or a pixel inside the block to be encoded using fine parameters adjacent to each other, and the pixel is divided into a region (■) and a region (2). For example, if the pixel divided in this way is in the area ■, select filter characteristic A, if it is in the area ■, select filter characteristic B, if it is in the area ■, select filter characteristic C, and if the pixel is in the area ■, select filter characteristic A. When the filter characteristic is in the region (■), filter characteristic E is selected and used. In other words, by switching the strength of the filter characteristics for five pixel regions like ■ku■ku■ku■ku■, it is possible to cut the high frequency components of the block encoded with coarse parameters including the contour part. can.

In the above explanation, the pixel is divided into regions (1) to (2), but by combining the five regions, the following (,) to () may be selected. FIG. 6K shows area divisions in (a) to (4).

(&) Divide into two areas: ■+■ and ■+■10■.

(b) Divide into two areas: ■+■+■ and ■+■.

(C) Divide into two areas: ■+■+■+■, and ■.

(d) Divide into two areas: ■+■ and ■+■10■.

(e) Divide into two areas: ■+■+■ and ■+■.

(f) Divide into two areas: ■, ■+■+■10■.

(g) Divide into three areas: ■, ■, and ■1010.

■ Divide into three areas: ■+■, ■, and ■10■.

(1) Divide into three areas: ■10+■, ■, ■.

(j) Divide into three areas: ■+■, ■, and ■10.

(2) Divide into three areas: ■, ■10, and ■+■.

V) Divide into four areas: ■+■, ■, ■, ■.

(c) Divide into four areas: ■, ■+■, ■, ■.

(,) Divide into four areas: ■+■, ■, ■, ■.

(o) Divide into four areas: ■, ■, ■, and ■+■.

Conflict) Divide into four areas: ■, ■, ■, ■10.

Furthermore, the strength of the filter characteristics is changed depending on the coarseness of the encoding parameters. In Fig. 7, for example, when the encoding parameters are coarse, the block distortion becomes large, so the fifth
Filter characteristics E and F, which have strong blur, are used in the pixel regions marked with ■ and ■ in the figure.

On the other hand, when the encoding parameters are thin, block distortion does not appear conspicuously.

Filter characteristic A, which provides the weakest blur, is used for the pixel region (2). In this way, by changing the characteristics of the smoothing filter temporally depending on the roughness of the encoding parameter,
It has the characteristic that when the encoding distortion is small, a decrease in the resolution of the decoded image can be suppressed, and when the encoding distortion is large, the image quality can be improved.

〔Effect of the invention〕

As explained above, the present invention performs smoothing filter processing with different strengths for each coarse block and pixel position of encoding parameters on a moving image to be encoded by block-by-block processing, and By changing the strength of the smoothing filter over time depending on the situation, the block distortion of the encoded predicted image can be significantly reduced using the smoothing filter, and at the same time, the visual quality of the decoded image can be significantly improved. be able to. In addition, since the smoothing process is performed by changing the characteristics of the smoothing filter according to the different pixel regions to be encoded and the roughness of the encoding parameters, it is possible to reduce the decrease in the resolution of the encoded predicted image and the entire image during decoding. This has the effect of providing visually easy-to-see images.

Furthermore, since the smoothing filter can smooth out significant level changes in the signal within a moving block, it is also effective in reducing the amount of information generated during encoding.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a moving image signal smoothing processing device according to the present invention, FIGS. 2 and 3 are time charts for explaining the operation of FIG. 1, and FIG. 4 is a detailed diagram of the present invention. FIG. 5 and FIG. 6 are explanatory diagrams for explaining the method of dividing a pixel area in the present invention, and FIG. 7 is an explanatory diagram for explaining the filter processing control method according to the present invention. FIG. 8 is an explanatory diagram for explaining problems in a conventional video encoding device. 104・Fist・ilE! ! Static blotter block determination circuit --- Pixel address counter, 106...φ Pixel area determination circuit, 107... Block determination circuit, 108
... Filter characteristic control circuit, 111 ... Smoothing filter, 115 ... Memory circuit.

Claims (1)

[Claims] A device that performs smoothing processing on a video signal input to a video encoder based on block unit processing includes a circuit that determines whether a block to be encoded is a moving block or a still block, and a circuit that determines encoding parameters. A memory circuit for storing, a circuit for selecting encoding parameters to be written into the memory circuit according to a motion/static block identification signal, a circuit for determining whether the encoding parameters are coarse or fine, and a counter for counting pixel positions. a determination circuit that determines a pixel region to be divided by referring to the pixel count value in this counting circuit, surrounding pixel regions, and coarse determination results of the encoding parameters; A moving image characterized by comprising a circuit that controls smoothness according to the roughness of an encoding parameter in each block, and a circuit that performs smoothing filter processing on the moving image signal according to a signal that controls the smoothness. Signal smoothing processing device.