JPH08205178A - Method for reducing quantization noise and device for decoding image data - Google Patents

Abstract

PURPOSE: To provide the method for reducing the quantization noise and the device for decoding the image data which can easily realize a decoded image signal having the quantization noise reduced. CONSTITUTION: A control part 6 generates a control signal according to motion vector information detected by a motion vector detection part 5 from a bit stream consisting of converted and encoded image data and additional information, i.g., motion vector values set individually by areas of predetermined size including at least one unit block. Further, the control part 6 generates a control signal according to differences between the motion vector values set individually by the areas and motion vector values of adjacent areas. Signal processing for adaptively reducing a high-frequency component with the control signals is performed by controlling the passing band of a variable passing band low-pass filter 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing quantization noise generated when decoding transform-encoded image data, and decoding the transform-encoded image data by applying the above method. Regarding the chemical conversion device.

[0002]

2. Description of the Related Art In the case of transmitting, recording and reproducing image signals, audio signals, and other various signals as digital signals,
Information compression / expansion technology is used. That is, for example, when digitizing an image signal or an audio signal, linear quantization (equal quantization) in which each sample value is replaced with one of the representative values of the signal level that is equally divided is transmitted. ， The amount of information of the signal to be recorded and reproduced is
This is because there will be very many. Therefore, in the technical field of broadcast communication and the technical field of recording / reproduction, for example, human vision and hearing are sensitive to a portion where the signal changes little, and there is some error in a portion where the signal changes drastically. In addition to utilizing the human visual and auditory properties, which are difficult to detect, to reduce the amount of information for each sample, many information compression techniques are applied to transmit, record, and reproduce. It is well known that a high-efficiency compression technique (high-efficiency information encoding technique) for various kinds of targeted information has been put into practical use.

Now, the amount of information per hour in a moving image having a quality similar to that of a reproduced image displayed using a reproduced signal from a VHS (registered trademark) VTR currently in practical use is about 109 G bits. In addition, the amount of information per hour in a moving image of a quality similar to the received image of the current standard color television system in Japan is about 360 G bits, but it has a large amount of information as described above. Practical studies have also been actively conducted on a high-efficiency compression method of image information required for transmitting and recording / reproducing image information using a current transmission line or recording medium that has been put to practical use. ..

By the way, in the high-efficiency compression method of image information, which is currently proposed as a practical high-efficiency compression method of image information, the correlation between the adjacent pixels in the natural image is high. Of the amount of information performed by using the correlation function (compression of the amount of information performed by using the spatial correlation function) and the amount of information performed by using the correlation function between screens (frames) arranged on the time axis. The amount of information is compressed by combining three different types of compression means: compression (compression of information amount using temporal correlation), compression of information amount due to deviation of code appearance probability, and compression of information amount. Efficient coding is achieved. As a means for compressing the information amount of an image using the above-mentioned intra-frame (intra-frame) correlation, many methods have been proposed in the past, but in recent years, K-L ( Karonen-Reeve) transform, discrete cosine transform (DCT), discrete Fourier transform,
Orthogonal transformations such as Walsh-Hadamard transformations have been adopted as typical examples.

[0005] For example, MPEG (Moving Picture C) established under ISO (International Organization for Standardization)
The high-efficiency coding method of image information (sometimes referred to as MPEG1 method or MPEG2 method) proposed as a result of international standardization work by the Odging Expert Group includes intra-frame coding and inter-frame coding. High-efficiency coding of moving image information is performed in combination with motion-compensated prediction and inter-frame prediction. As the orthogonal transformation, two-dimensional discrete cosine transformation (2
Dimensional DCT) is adopted. In the orthogonal transform, a predetermined block size (N × M pixels ← horizontal N pixels × vertical M line block size) is set for the image signal of each screen to be subjected to high efficiency encoding. An image divided for each “unit block” (in the MPEG1 system and the MPEG2 system, a block having a block size of 8 × 8 pixels ← horizontal 8 pixels × vertical 8 lines is a “unit block”) Performed on signals.

[0006] (N × M) orthogonal transform coefficients (8 × 8 = 6 in the above-mentioned MPEG1 system and MPEG2 system) obtained by performing orthogonal transform for each block of the above unit.
The four DCT transform coefficients) are areas of a predetermined size including at least one of the blocks of the above-mentioned units (areas called “macroblock” in the above-mentioned MPEG1 system and MPEG2 system). , That is,
In the MPEG1 method and the MPEG2 method, an area having a block size of 16 × 16 pixels ← horizontal 16 pixels × vertical 16 lines for the luminance signal Y and two color difference signals Cr and C
(A region consisting of 8 × 8 pixels ← horizontal 8 pixels × vertical 8 line block size region for each b)
It is quantized by the "block quantization width value" set for each. For example, in the MPEG1 system and the MPEG2 system, the above-mentioned “block quantization width value” is represented as [{macroblock quantization characteristic value (or macroblock quantization scale) QS} × quantization matrix].

The orthogonal transform coefficient (for example, DCT coefficient) quantized by the block quantization width value is separated into its DC component (DC component) and AC component (AC component). The DC component of the orthogonal transform coefficient (for example, DCT coefficient) is differentially encoded, and the AC component of the orthogonal transform coefficient (for example, DCT coefficient) is entropy-encoded after zigzag scanning (information due to deviation of the appearance probability of the code). Quantity compression ... Variable length coding such as Huffman method). The image data converted and encoded as described above is output as a bit stream (bit string). Next, the decoding operation for the image data that has been transform-encoded as described above is performed in the reverse operation of the encoding operation described above to obtain the output image. When quantization is performed, the presence of a quantization error that cannot be avoided causes quantization noise in the output image. Then, when the complexity of the image to be encoded is large with respect to the transmission rate, the above-mentioned quantization noise greatly deteriorates the image quality.

Generally, among the quantization errors that cause the above-mentioned quantization noise, the quantization error of the low-frequency component is the output image distortion in a state where there is no correlation between unit blocks, so-called block distortion. Among the quantization errors that occur inside and cause the quantization noise, the quantization error of the high frequency component causes ringing-like output image distortion, so-called mosquito noise, around the edges. By the way, the quantization noise generated in the image as described above is particularly noticeable in the flat part of the image, and small noise is added to a place where there is a large change in the video signal level from the low range to the high range. In the case of such a quantization noise waveform, it is difficult to detect noise because the difference in sensitivity in visual characteristics is small. However, when a large change in the video signal level exists only in the low frequency range and the small noise is added to the high frequency range, the noise is easily detected. As a matter of course,
It goes without saying that when a large amount of noise is added, fatal fatality is detected as coding deterioration regardless of whether it is in the low band or the high band. And, as one of means for solving the problem of deterioration of image quality due to quantization noise as described above,
As one of them, as disclosed in, for example, Japanese Patent Laid-Open No. 4-372074, a solution means has been proposed to reduce the quantization noise by applying a post filter to the decoded image.

[0009]

However, when the means for applying the post-filter to the decoded image, which is disclosed in the above-mentioned Japanese Patent Laid-Open No. 4-372074, is applied, only a part of the image within the frame is deteriorated. Even in such a case, since the filter uniformly acts on the entire frame, there is a problem that the image quality of the part where the image is not deteriorated deteriorates, and a solution to it has been demanded.

[0010]

According to the present invention, an image signal divided for each unit block having a predetermined block size is orthogonally transformed for each unit block, and then at least the above unit block is used. Is quantized using a block quantization width value that is individually set for each area of a predetermined size including one of the predetermined blocks including at least one unit block described above. When decoding the image data that has been transform-coded by performing the inter-frame predictive coding that also uses the motion vector for each size region, it includes one of the blocks of the above-mentioned unit obtained in the decoding process. The signal processing for reducing the high frequency component is performed according to the magnitude of the motion vector for each area of a predetermined size, or the unit block obtained in the decoding process is used. Signal processing for reducing the high frequency component according to the difference between the motion vector value of each area having a predetermined size including one clock and the motion vector value of the adjacent area. A method for reducing quantization noise that occurs when decoding transform-coded image data, and a decoding device for image data that applies the method for reducing quantization noise that occurs when decoding image data, that is,
The image signal divided for each unit block having a predetermined block size is orthogonally transformed for each unit block, and then the image signal divided for each unit block having a predetermined block size is After being orthogonally transformed for each unit block, the quantization is performed using at least a block quantization width value individually set for each area of a predetermined size including one of the unit blocks described above. And decoding of image data that has been transform-coded by performing inter-frame predictive coding that also uses a motion vector for each area of a predetermined size that includes one of the above-described at least unit blocks. For this purpose, at least a buffer memory, a variable length decoding unit, an inverse quantization unit, an inverse orthogonal transform unit, an inverse motion compensation unit, and an image memory are provided. In the decoding device for transform-encoded image data configured as described above, the motion vector set individually for each region obtained by detecting the motion vector set individually for each region described above. Depending on the difference between the motion vector value set individually for each of the above-mentioned areas and the motion vector value of an adjacent area, The variable pass band low-pass filter of the variable pass band low-pass filtering means whose pass frequency band can be varied by a control signal is controlled so that the high pass component can be adaptively reduced according to the motion vector. There is provided a decoding device for transform-coded image data for controlling a band-pass filtering means.

[0011]

A predetermined block size (N × M) is applied to an image signal of each screen which is a target of high efficiency encoding.
Pixels ← horizontal N pixels x vertical M line block size) are obtained by orthogonal transformation for each "unit block" (N x
M) the orthogonal transform coefficients are quantized using a “block quantization width value” set for each area of a predetermined size including at least one block of the unit, and Image data that has been transform-encoded by performing inter-frame predictive encoding that also uses a motion vector for each area of a predetermined size that includes at least one unit block A bit stream including additional information (for example, block quantization width information, motion vector, prediction mode information, etc.) required at the time of decoding the image data is stored in the buffer memory. In the variable length decoding unit to which the bit stream read from the buffer memory is supplied, the entropy-coded (variable-length coded) image data and the addition required when decoding the transform-coded image data are added. Information (for example, block quantization width information, motion vector, prediction mode information, etc.) is decoded.

Decoded image data and block quantization width information in the decoded additional information are supplied to the dequantization section, so that the dequantization operation performed on the image data by the dequantization section causes An orthogonal transform coefficient is supplied from the inverse quantization unit to the inverse orthogonal transform unit. In the inverse orthogonal transform unit,
The image data in the frequency domain is inversely transformed into the image data in the time domain by performing a two-dimensional inverse orthogonal transformation for each unit block. The image data in the time domain which is output from the inverse orthogonal transform unit is added to the image data in the motion compensated state by the motion compensation unit according to the coding type indicating the difference between intraframe coding and interframe coding. Or,
The output image data is stored in the image memory with or without addition.

The motion vector information in the additional information contained in the bit stream is detected, and the detected motion vector information, that is, a predetermined size including at least one block of the unit. Control signal is generated according to the motion vector value set individually for each area, and the difference between the motion vector value set individually for each area and the motion vector value of the adjacent area. A signal processing for generating a control signal in response to the control signal and adaptively reducing the high frequency component by the control signal is performed by controlling the pass band of the variable pass band low pass filter.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is a detailed description of a block distortion reducing method and a decoding device for transform-encoded image data according to the present invention, with reference to the accompanying drawings. Will be described in detail. 1 and 2 are block diagrams showing a configuration example of an image data decoding apparatus to which the quantization noise reducing method of the present invention is applied, FIG. 3 is a diagram used for explaining a differential motion vector in an adjacent region, and FIG. Is a block diagram showing a configuration example of a variable pass band low pass filter,
FIG. 5 is a diagram used for explaining a filtering state at the boundary of a unit block, FIG. 6 is a block diagram showing a configuration example of a control signal generating section, and FIG. 7 is an explanatory diagram of a control characteristic example.

In the image data decoding apparatus of the present invention shown in FIGS. 1 and 2, reference numeral 1 denotes an input terminal of a bit stream (bit string) to be decoded, and in each drawing, it is surrounded by a one-dot chain line frame. (3,15 ...
The decoder integrated circuit) is said to be an integrated circuit component. In the embodiment of the decoding device shown in each of FIG. 1 and FIG. 2, at least the buffer memory 8 and the variable length decoding unit 9 are the constituent parts surrounded by the one-dot chain line frame 3. It is possible to use a commercially available product that includes the inverse quantization unit 10, the inverse orthogonal transformation unit 11, the addition unit 12, the motion compensation unit 13, and the image memory 14, and is integrated into an integrated circuit.

The bit stream supplied to the above-mentioned input terminal 1 is a compression of the information amount of the image by the orthogonal transformation using the intra-frame (intra-frame) correlation factor (the information amount performed by using the spatial correlation factor). Compression) and the amount of information performed by using the correlation correlation between screens (frames) arranged on the time axis (compression of the information amount performed by using the temporal correlation correlation), and the probability of appearance of the code. It is said that the image data is high-efficiency conversion-encoded image data (for example, image data according to the MPEG1 system or MPEG2 system) in combination with three different types of compression means including compression of the information amount due to the bias. In the following description of this specification, it is assumed that the image data to be decoded is image data based on the MPEG1 system and the MPEG2 system.

High-efficiency coding of moving picture information in the MPEG1 system and the MPEG2 system is a combination of intra-frame coding by two-dimensional discrete cosine transform (two-dimensional DCT) and inter-frame coding, and motion compensation prediction is performed. Or with inter-frame prediction. Then, the image signal of the screen for each one that has been subjected to high efficiency encoding is
The image data is divided into “unit blocks” having a block size of 8 × 8 pixels (8 pixels in the horizontal direction × 8 lines in the vertical direction), and DCT is performed for each of the blocks in the above units. The 64 DCT transform coefficients for each block of each unit are quantized with the "block quantization width value". MPEG1 system,
In the MPEG2 system, the “block quantization width value” is a region called a “macroblock” of a region of a predetermined size including one of the blocks of the units described above, that is, a luminance. 16 for signal Y
A region having a block size of 16 pixels (horizontal 16 pixels x vertical 16 lines) and a block size of 8 x 8 pixels (horizontal 8 pixels x vertical 8 lines) for each of the two color difference signals Cr and Cb It is a value indicated by the product of {macroblock quantization characteristic value (or macroblock quantization scale) QS} set for each area (area of size) and the quantization matrix.

The DCT coefficient which is quantized with the DCT transform coefficient as the dividend and the "block quantization width value" as the divisor, has its direct current component (DC component) and alternating current component (AC).
Component) and separated. The DC component of the DCT coefficient is differentially encoded, and the AC component of the DCT coefficient is zigzag-scanned and then entropy-encoded (information amount compression due to bias of appearance probability of code ... For example, variable length code such as Huffman method). Image data that has been converted into transform coded information is added to additional information [for example, {block quantization width information →
Macroblock quantization characteristic value (or macroblock quantization scale) QS} and motion vector, prediction mode information, etc.] are added to form a bitstream.
In the image data decoding apparatus of the present invention shown in each of FIGS. 1 to 6, the bit stream supplied to the input terminal 1 is, for example, a first-in first-out memory (FI).
FO) is stored in the buffer memory 8.

In the variable length decoding unit 9 to which the bit stream read from the buffer memory 8 is supplied, at the time of decoding the entropy coded (variable length coded) image data and the transform coded image data. Necessary additional information, for example, {block quantization width information → macroblock quantization characteristic value (or macroblock quantization scale) QS}, motion vector, prediction mode information, etc.) is decoded. Then, the image data decoded by the variable length decoding unit 9 and the block quantization width information {macroblock quantization characteristic value (or macroblock quantization scale) QS} are supplied to the inverse quantization unit 10. Further, the motion vector, the prediction mode information, and the like are supplied to the inverse motion compensation unit 13.

The image data decoded by the variable length decoding unit 9 and the block quantization width information {macroblock quantization characteristic value (or macroblock quantization scale) QS} in the decoded additional information are Given inverse quantizer 1
At 0, the DCT transform coefficient obtained by performing the inverse quantization operation is supplied to the inverse orthogonal transform unit (inverse DCT) 11. The inverse orthogonal transform unit (inverse DCT) 11 performs a two-dimensional inverse DCT for each unit block, inversely transforms image data in the frequency domain into image data in the time domain, and supplies it to the addition unit 12. To do. The image data in the time domain supplied to the adding unit 12 as described above is an image in a state in which motion compensation is performed by the motion compensation unit 13 according to a coding type indicating a difference between intraframe coding and interframe coding. Output data is stored in the image memory 14 as output image data, with or without addition to the data. Buffer memory 8, variable length decoding unit 9, inverse quantization unit 10, and inverse orthogonal transformation unit 11
, Adder 12, motion compensator 13, and image memory 14
The description so far regarding the operation of each of the above-mentioned components is common to the operation of each of the above-mentioned components in the image data decoding apparatus of the present invention shown in FIGS.

In the image data decoding apparatus of the present invention shown in each of FIGS. 1 and 2, the image data from the image memory 14 in the decoder integrated circuit 3 (or 15) is a variable band low-pass filter. It is output to the output terminal 2 via 7. The variable band low pass filter 7 is
The control signal supplied from the control signal generator 6 to the variable band low pass filter 7 controls the signal level of the high band portion of the image signal passing therethrough to change. A concrete configuration example of the control signal generator 6 is shown in FIG. A concrete configuration example of the variable band low-pass filter 7 described above is shown in FIG. The constituent part shown by a dotted frame 7h in FIG. 4 is a constituent functioning as a variable band low-pass filter in the horizontal direction of the image, and the constituent shown by a dotted frame 7v in FIG. The part is a component functioning as a variable band low pass filter in the vertical direction of the image.

In the concrete configuration of the variable band low pass filter 7 illustrated in FIG. 4, the variable band low pass filter 7 functions as a variable band low pass filter in the horizontal direction of the image shown by the dotted frame 7h. A two-dimensional variable band low band as a whole is formed by serially connecting the component part and the component part functioning as a variable band low pass filter in the vertical direction of the image shown by the dotted frame 7v. It is configured as the pass filter 7. The variable band low-pass filter 7 is composed of one two-dimensional low-pass filter, a subtractor (a subtracter provided corresponding to 17 in FIG. 4), and a multiplier (in FIG. 4). 18 and a adder (subtractor provided corresponding to 19 in FIG. 4) may be configured.

The variable band low-pass filter 7 illustrated in FIG.
In the above, the above-mentioned component 7h is a horizontal LPF 1 configured to have a predetermined fixed cutoff frequency.
6, a subtractor 17, a multiplier 18, and an adder 19, and the above-mentioned component 7v is
A vertical LPF 20 configured to have a predetermined fixed cutoff frequency, a subtractor 21, a multiplier 22,
And an adder 23. The control signal generator 6 controls the multipliers 18 (22) provided in the two component parts 7h and 7v of the variable band low-pass filter 7 shown in FIG. A signal (for example, coefficient in the range of 0 to 1.0 ... Coefficient signal for multiplication) is supplied. As a result, the output image data from the variable band low-pass filter 7 has coefficients 0 to 1 for the signal components in the frequency band higher than the cutoff band in the LPF having the predetermined fixed cutoff frequency. The state is multiplied by 0.

That is, a control signal from the control signal generator 6 (for example, coefficient in the range of 0 to 1.0 ... Coefficient signal for multiplication)
Is an area in which an individual quantization scale value associated with a block quantization width used when quantizing a DCT transform coefficient is to be set, that is, a unit block (DCT) having a predetermined block size in which DCT is performed. Block), the motion vector value set individually for each area of a predetermined size including at least one block) and the difference value between the motion vectors set in adjacent areas are adaptively adjusted. This is a coefficient for causing the variable band low-pass filter 7 to perform signal processing that reduces high-frequency components.

In each area surrounded by a rectangular frame in FIG. 3, an individual quantization scale value associated with a block quantization width used when quantizing a DCT transform coefficient is set. Power region, that is, a unit block (D
A region of a predetermined size including at least one of the CT blocks), and M displayed in each region.
V0, MV1, MV2, MV3, MV4, MV5, MV6, M
V7 and MV8 indicate the motion vector values set in the respective areas, and the motion vector MVi described above is used.
(I is 0, 2, 3, ... 8) is represented by the following equation (1).

[0026]

[Equation 1]

In FIG. 3, a region whose motion vector value is shown as MV0 is defined as a current region, and this current region and eight regions adjacent to the current region (regions having an 8-connected relationship → motion vector). The value is MV1,
MV2, MV3, MV4, MV5, MV6, MV7, MV8) and the difference value dMV between the motion vector and the motion vector of the above-mentioned nine regions are MV0, MV1, MV2. , MV3, MV4, MV5, MV6,
It is obtained by performing the operation shown in the following equation (2) using MV7 and MV8. In addition, MV0, MV1, MV2 ... MV8
For the motion vector of each area indicated by, for example, MV0 is MV (x0, y) using the X and Y coordinates shown in the parentheses.
o), MV1 is MV (xo-1, yo-1), MV2 is MV (x
o, yo-1), MV3 is MV (xo + 1, yo-1), MV4 is M
V (xo-1, yo), MV5 is MV (xo + 1, yo), MV6
Is MV (xo-1, yo + 1), MV7 is MV (xo, yo +)
1) and MV8 are represented as MV (xo + 1, yo + 1).

[0028]

[Equation 2] Note that MV0 (x) in the equation (2) is MV (xo), MV0
(y) is MV (yo), and MV1 (x) is MV (x
o-1), MV1 (y) is MV (yo-1), MV2 (x) is MV
(Xo), MV2 (y) is MV (yo-1), MV3 (x) is M
V (xo + 1), MV3 (y) is MV (yo-1), MV4 (x)
Is MV (xo-1), MV4 (y) is MV (yo), MV5
(x) is MV (xo + 1), MV5 (y) is MV (yo), M
V6 (x) is MV (xo-1), MV4 (y) is MV (yo +
1), MV7 (x) is MV (xo), MV7 (y) is MV (y
o + 1), MV8 (x) is MV (xo + 1), and MV8 (y) is MV (yo + 1).

The motion vector MVi (MV0 in FIG. 3) and the motion vector difference value dMV are standardized between G (x, y) 1.0 to 0.0.
In FIG. 7, the magnitude of the motion vector MV (or the magnitude of the motion vector difference value dMV) is plotted on the horizontal axis, and the vertical axis is the multiplication supplied from the control signal generator 6 to the variable band low-pass filter 7. A setting example of a plurality of control characteristics A to E for adaptively reducing the high frequency component by taking a coefficient (1.0 to 0.0) and depending on the magnitude of the motion vector MV and the magnitude of the difference vector dMV Is shown. For example, when the magnitude of the difference value dMV of the motion vector is 50 or more, the A characteristic, when the magnitude of the difference value dMV of the motion vector is 40 or more and less than 50, the B characteristic, and the magnitude of the difference value dMV of the motion vector are When the magnitude of the motion vector difference value dMV is 20 or more and less than 30, it is the C characteristic when it is 30 or more and less than 40, and the E characteristic when the magnitude of the motion vector difference value dMV is less than 20. , Set the control characteristics.

As shown in FIG. 6, the coefficient signal in the range of 0.0 to 1.0 is generated as described above, and the coefficient signal is output to the variable band low pass filter 7.
6 is a configuration example of a control signal generation unit 6 (control signal generation unit 6 shown in FIGS. 1 and 2) supplied to the control signal generation unit 6 shown in FIG. The motion vector information memory 24 having a storage capacity capable of storing the motion vector information in a range (for example, at least about 3 macroblock lines) is made to store the motion vector information of successive areas. Memory 2 for motion vector information
The motion vector information stored in 4 is read out, and the motion vector information comparison / determination unit 25 of the adjacent regions sequentially calculates the motion vector information in each of the adjacent regions by, for example, the calculation of the above equation (2). The value of the magnitude dMV of the motion vector for the current area is calculated and supplied to the multiplication coefficient setting unit 26.

The multiplication coefficient setting unit 26 uses the value of the magnitude dMV of the motion vector for the sequential current area supplied thereto as an address, and the magnitude of the difference value dMV of the motion vector as illustrated in FIG. And a coefficient signal (control signal) corresponding to a coefficient that satisfies the relationship between the multiplication coefficient (1.0 to 0.0) supplied from the control signal generator 6 to the variable band low-pass filter 7 (ROM signal). Output from the lookup table). The coefficient signal is supplied from the control signal generator 6 to the variable band low-pass filter 7 as a control signal from the control signal transmitter 27. The control signal generation unit 6 configured to generate the control signal corresponding to the magnitude of the motion vector MV of the sequential area, when the magnitude of the motion vector MV of the sequential area is given as an address, A ROM table (look-up table) provided such that predetermined coefficient signals are output can be used. Further, as the address given to the ROM table (look-up table), the difference value d of the above-mentioned motion vector
In addition to the magnitude of MV or the magnitude of motion vector,
The magnitude of the motion vector difference value dMV and the pixel address value, or the magnitude of the motion vector and the pixel address value may be used.

By the way, a motion vector value or a motion vector difference set individually for each area of a predetermined size including at least one unit block having a predetermined block size for which DCT is performed. FIG. 5 shows the filtering operation of the low-pass characteristic for the pixels in the vicinity of the boundary of the block of the selected unit by the variable band low-pass filter 7 that performs the signal processing operation to adaptively reduce the high frequency component with the value. This is done as illustrated and described. That is, in FIG. 5, t1, t2,
t3 ... Indicates different times, each being shifted by one clock cycle. FIG. 5 shows a case where the variable band low-pass filter 7 is configured as a low-pass filter having a filter length of 5 taps in the FIR filter, in the vicinity of the boundary of the unit block in the pixel array of a specific one row in the image. Sequential pixels p-3, p-2, p-1, p, p + 1, p
Shows a state in which low-pass filtering is applied to +2, p + 3 ....

In the image data decoding apparatus of the present invention shown in FIGS. 1 and 2, the bit stream (bit string) supplied to the input terminal 1 to be decoded is at least the buffer memory 8 and the variable length. Image data decoded by a component including a decoding unit 9, an inverse quantization unit 10, an inverse orthogonal transformation unit 11, an addition unit 12, a motion compensation unit 13, and an image memory 14. Image memory 1
As described above, the decoded image data stored in the image memory 14 can be output from the image memory 14. Then, the image data decoding apparatus of the present invention shown in FIGS. 1 and 2 applies the image data read from the image memory 14 to the variable band low-pass filter 7 to perform the variable By the operation of the band low-pass filter 7, the image data in which the quantization noise is reduced is output from the output terminal 2 of the image data decoding device.

First, in the image data decoding apparatus of the present invention shown in FIG. 1, the bit stream to be decoded supplied to the input terminal 1 is a buffer provided in the decoder integrated circuit 3. It is supplied to the memory 8 and also to the buffer memory 4. The bit stream read from the buffer memory 4 using the first-in first-out memory is supplied to the motion vector detection unit 5. The motion vector detecting section 5 may be of a configuration having the same function as the variable length decoding section 9 provided in the decoder integrated circuit 3. Then, the motion vector detecting unit 5 detects the motion vector information for each region in the bit stream supplied thereto, and supplies it to the control signal generating unit 6.

By the way, in the image data decoding apparatus of the present invention shown in FIG. 1, the bit stream to be decoded supplied to the input terminal 1 is provided in the buffer memory provided outside the decoder integrated circuit 3. 4 and supplies the bit stream read from the buffer memory 4 to the motion vector detecting unit 5, and the motion vector detecting unit 5 generates the control signal of the motion vector information for each sequential region detected from the bit stream. Although it is given to the section 6, in the image data decoding apparatus of the present invention shown in FIG.
By the operation of the variable length decoding unit 9 provided inside the decoder integrated circuit 15, the motion vector information for each sequential region detected from the bit stream is given to the control signal generating unit 6.

That is, the image data decoding apparatus of the present invention shown in FIG. 2 is the same as the image data decoding apparatus of the present invention shown in FIG. Long decoding unit 9 and inverse quantization unit 1
0, an inverse orthogonal transformation unit 11, an addition unit 12, a motion compensation unit 13, and a buffer memory 4 externally attached to a decoder integrated circuit 3 which is integrated into a circuit including an image memory 14. The operation of the motion vector detecting section 5 is performed by utilizing the functions of the buffer memory 8 and the variable length decoding section 9 provided inside the decoder integrated circuit 3, and the variable length decoding section is also used. The control signal generator 6 to which the motion vector information for each sequential region detected from the bit stream by 9 is given, and the control signal generator 6 described above.
Also included in one decoder integrated circuit 15 is a component part of the variable band low pass filter 7 for controlling the high frequency component of the image data supplied from the image memory 14 by the control signal output from the image memory 14. Thus, the integrated circuit is configured as described above.

In the image data decoding apparatus of the present invention shown in FIGS. 1 and 2, the control signal generating section 6 has a configuration as exemplified in FIG. 6 as described above. Further, as the variable band low-pass filter 7, for example, the one having the configuration illustrated in FIG. 4 as described above is used. Therefore, in the image data decoding apparatus of the present invention shown in FIG. 1 and FIG. 2, the control signal generated by the control signal generation unit 6, that is, the additional information included in the bit stream as described above. In order to perform signal processing that adaptively reduces the high frequency component based on the magnitude of the motion vector information value MV or the motion vector difference value dMV for each region in the By controlling the pass band of the pass filter, the quantization noise in the image can be satisfactorily reduced.

[0038]

As is apparent from the above detailed description, the quantization noise reducing method and the image data decoding apparatus according to the present invention can be applied to each of the high-efficiency encoding targets. The image signal of the screen is obtained by performing orthogonal transform for each “unit block” having a predetermined block size (N × M pixels ← horizontal N pixels × vertical M line block size) (N × M) The orthogonal transform coefficient of the block is quantized using a "block quantization width value" set for each area of a predetermined size including at least one block of the unit, and at least the unit Image data that has been transform-coded by performing inter-frame predictive coding that also uses a motion vector for each area of a predetermined size that includes one of the blocks The motion vector information of the additional information included in the bitstream with the additional information required for decoding (eg, block quantization width information, motion vector, prediction mode information, etc.) is detected and detected. A control signal is generated according to the motion vector information, that is, a motion vector value that is individually set for each area of a predetermined size including at least one unit block, and each area described above. A signal that generates a control signal according to the difference between the motion vector value set individually for each and the motion vector value of the adjacent area, and adaptively reduces the high frequency component by the control signal. By performing the processing by controlling the pass band of the variable pass band low-pass filter, adaptively according to the magnitude of the motion vector of each region obtained in the decoding process. The magnitude of the frequency component can be controlled to reduce the high frequency component only in the portion where the motion is intense and the quantization noise is generated, and the magnitude of the difference value of the motion vector between the regions obtained in the decoding process. Depending on the degree of deterioration and the degree of deterioration of the decoded image, it is possible to adaptively control the size of the high-frequency component and reduce the high-frequency component only in the part where the motion is intense and quantization noise is generated. , The reason that the quantization noise can be effectively removed, and the motion compensation is relatively easy to reach when the image is moving over the entire image, and the quantization noise is also relatively small. From the visual characteristics of, the resolution is easier to recognize when the blocks are moving in the same direction than when the blocks are moving in different directions. However, the quantization noise can be satisfactorily removed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an image data decoding device to which a quantization noise reducing method of the present invention is applied.

FIG. 2 is a block diagram showing a configuration example of an image data decoding device to which the quantization noise reducing method of the present invention is applied.

FIG. 3 is a diagram used for explaining a differential motion vector in an adjacent area.

FIG. 4 is a block diagram showing a configuration example of a variable pass band low pass filter.

FIG. 5 is a diagram used for explaining a filtering state at a boundary between unit blocks.

FIG. 6 is a block diagram showing a configuration example of a control signal generator.

FIG. 7 is a characteristic example diagram showing a relationship between a motion vector and a control characteristic.

[Explanation of symbols]

[Description of Codes] 1 ... Input terminal, 2 ... Output terminal, 3, 15 ... Decoder integrated circuit, 4, 8 ... Buffer memory, 5 ... Motion vector detection section, 6 ... Control signal generation section, 7 ... Variable band low Band-pass filter, 9 ... Variable length decoding unit, 10 ... Inverse quantization unit, 11 ... Inverse orthogonal transform unit (inverse DCT unit), 12 ... Addition unit, 13 ... Inverse motion compensation unit, 14 ... Image memory, 16 ... … Horizontal LPF, 1
7, 21 ... Subtractor, 18, 22 ... Multiplier, 19, 23 ...
Adder, 20 ... Vertical LPF,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H03H 17/06 B 8842-5J H03M 7/30 A 9382-5K 7/40 9382-5K G06F 15 / 68 410

Claims (6)

[Claims] 1. An image signal divided into blocks of a unit having a predetermined block size is orthogonally transformed for each block of each unit, and is then predetermined including at least one of the blocks of the unit. Motion vector is quantized by using the block quantization width value set individually for each area having a predetermined size, and the motion vector for each area having a predetermined size including at least one block of the unit described above. A region of a predetermined size including one of the blocks of the unit obtained in the decoding process in decoding the image data that has been transform-coded by performing inter-frame predictive coding using Quantization that occurs when decoding transform-coded image data, characterized by performing signal processing that reduces high-frequency components according to the magnitude of each motion vector How to reduce noise. 2. An image signal divided for each unit block having a predetermined block size is orthogonally transformed for each unit block and then divided for each unit block having a predetermined block size. After the image signal has been orthogonally transformed for each unit block, at least a block quantization width value that is individually set for each area of a predetermined size including one of the unit blocks described above. Is quantized by using, and is transform-coded by performing inter-frame predictive coding that also uses a motion vector for each area of a predetermined size including one of the at least unit blocks described above. In order to decode the existing image data, at least a buffer memory, a variable length decoding unit, an inverse quantization unit, an inverse orthogonal transform unit, an inverse motion compensation unit, and an image A decoding device for transform-coded image data configured to include an image memory, the motion vector detecting section detecting a motion vector set individually for each of the regions described above, and Control signal generating means for generating a control signal according to a motion vector set individually for each region sequentially output from the motion vector detection unit, and a variable pass band low band whose pass frequency band can be varied by the control signal. A filtering means; and a means for controlling the variable pass band low-pass filtering means so that the high frequency component can be adaptively reduced according to the magnitude of the motion vector output from the control signal generating means. Decoding device for transform-coded image data. 3. An image signal divided for each unit block having a predetermined block size is orthogonally transformed for each unit block and then divided for each unit block having a predetermined block size. After the image signal is orthogonally transformed for each unit block, the block quantization width value set individually for each area of a predetermined size including at least one of the unit blocks described above is set. Is quantized by using, and is also transform-coded by performing inter-frame predictive coding that also uses a motion vector for each area of a predetermined size including one of the at least unit blocks described above. At least a buffer memory for decoding the image data,
A variable-length decoding unit, an inverse quantization unit, an inverse orthogonal transformation unit, an inverse motion compensation unit, and a decoding device for transform-coded image data configured to include an image memory, Control signal generating means for generating a control signal according to a motion vector set individually for each region sequentially output from the variable length decoding unit, and a variable pass whose pass frequency band can be changed by the control signal. Band low-pass filtering means, and means for controlling the variable pass band low-pass filtering means so that the high frequency components can be adaptively reduced according to the magnitude of the motion vector output from the control signal generating means. A decoding device for transform-encoded image data, comprising: 4. An image signal divided into blocks of a unit having a predetermined block size is orthogonally transformed for each block of each unit, and then, is predetermined including at least one of the blocks of the unit. Motion vector is quantized by using the block quantization width value set individually for each area having a predetermined size, and the motion vector for each area having a predetermined size including at least one block of the unit described above. When decoding the image data that has been transform-coded by performing the inter-frame predictive coding also using, each of the predetermined size including one of the blocks of the above-mentioned unit obtained in the decoding process. Transform-coded, which is characterized by performing signal processing that reduces high-frequency components according to the motion vector value of each area and the difference between motion vector values of adjacent areas. A method for reducing quantization noise that occurs when decoding image data. 5. An image signal divided for each unit block having a predetermined block size is orthogonally transformed for each unit block and then divided for each unit block having a predetermined block size. After the image signal has been orthogonally transformed for each unit block, at least a block quantization width value that is individually set for each area of a predetermined size including one of the unit blocks described above. Is quantized by using, and is transform-coded by performing inter-frame predictive coding that also uses a motion vector for each area of a predetermined size including one of the at least unit blocks described above. In order to decode the existing image data, at least a buffer memory, a variable length decoding unit, an inverse quantization unit, an inverse orthogonal transform unit, an inverse motion compensation unit, and an image A decoding device for transform-coded image data configured to include an image memory, the motion vector detecting section detecting a motion vector set individually for each of the regions described above, and Control signal generating means for generating a control signal in accordance with a difference between a motion vector value individually set for each area sequentially output from the motion vector detecting section and a motion vector value of an adjacent area; And a variable pass band low pass filter capable of adaptively reducing the high band component according to the control signal output from the control signal generating means. A decoding device for transform-coded image data, comprising: a means for controlling the means. 6. An image signal divided for each unit block having a predetermined block size is orthogonally transformed for each unit block and then divided for each unit block having a predetermined block size. After the image signal has been orthogonally transformed for each unit block, at least a block quantization width value that is individually set for each area of a predetermined size including one of the unit blocks described above. Is quantized by using, and is transform-coded by performing inter-frame predictive coding that also uses a motion vector for each area of a predetermined size including one of the at least unit blocks described above. In order to decode the existing image data, at least a buffer memory, a variable length decoding unit, an inverse quantization unit, an inverse orthogonal transform unit, an inverse motion compensation unit, and an image A decoding device for transform-coded image data including an image memory, wherein a motion vector set individually for each region sequentially output from the variable length decoding unit described above. Control signal generating means for generating a control signal according to the difference between the value and the motion vector value of the adjacent area, a variable pass band low pass filtering means capable of varying the pass frequency band by the control signal, and the control signal generating means described above. A device for decoding transform-coded image data, which comprises means for controlling the variable pass band low-pass filtering means so that the high-pass components can be adaptively reduced in accordance with the control signal output from.