JP3337166B2 - Image processing apparatus and image processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 15 and 16) Problems to be Solved by the Invention Means for Solving the Problems (FIGS. 4 and 12 to 14) Operation (FIGS. 4 and 10) 1) Principle of hierarchical coding (FIGS. 1 to 3) (2) Image coding apparatus of the embodiment (FIGS. 4 to 7) (3) Selection of quantization step width (FIGS. 8 and 9) (4) Selection of initial value of quantization step width (FIG. 10) (5) Operation of embodiment (FIG. 11) (6) Effects of embodiment (7) Other embodiments (FIGS. 12 to 14) Effects of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method suitable for application to an image encoding apparatus for dividing predetermined image data into a plurality of image data having different resolutions. is there.

[0003]

2. Description of the Related Art Conventionally, as this type of image coding apparatus,
There is a method in which input image data is hierarchically encoded using a hierarchical encoding technique such as pyramid encoding. In this image coding apparatus, high-resolution input image data
Are sequentially and recursively formed as second hierarchical data having a lower resolution than the first hierarchical data, and third hierarchical data having a lower resolution than the second hierarchical data. A plurality of hierarchical data are transmitted through a transmission path including a communication path and a recording / reproducing path.

In an image decoding apparatus for decoding a plurality of hierarchical data, all of the plurality of hierarchical data may be decoded, or any one of the hierarchical data may be decoded according to the resolution of a television monitor corresponding thereto. A desired one may be selected for decoding. In this way, by decoding only the desired hierarchical data from the hierarchical data of a plurality of layers, it is possible to obtain the desired hierarchical data with a minimum necessary transmission data amount.

[0005] As shown in FIG. 15, in the image coding apparatus 1 that realizes, for example, four-layer coding as the layer coding, the thinning-out filters 2, 3, and 4 for three stages are respectively provided.
And interpolation filters 5, 6, 7 and input image data D
1, the reduced image data D2, D3, and D4 having lower resolution are sequentially formed by the thinning filters 2, 3, and 4 at each stage, and the reduced image data D2, D3, and D4 are reduced by the interpolation filters 5, 6, and 7 before the reduction. To the resolution of.

[0006] Input image data D1, each thinning filter 2
3 and the outputs D5 to D7 of the interpolation filters 5 to 7 are input to difference circuits 8, 9 and 10, respectively, thereby generating difference data D8, D9 and D10. As a result, in the image encoding device 1, the amount of hierarchical data is reduced and the signal power is reduced. Here, the difference data D8 to D10 and the reduced image data D
4 have sizes of 1, 1/4, 1/16, and 1/64, respectively.

The difference data D8 to D10 obtained from the respective difference circuits 8 to 10 and the reduced image data D4 obtained from the thinning-out filter 4 are converted into encoders 11, 12, 1
3 and 14, and are subjected to a compression process. As a result, first, second, third and fourth hierarchical data D11, D1 having different resolutions from the encoders 11, 12, 13, 14 are obtained.
2, D13 and D14 are transmitted to the transmission line in a predetermined order.

The first to fourth hierarchical data D11 to D14 transmitted in this manner are decoded by the image decoding device 20 shown in FIG. That is, the first to fourth hierarchical data D11 to D14 are respectively provided to the decoders 21 and 22,
The decoding is performed by the decoders 23 and 24. As a result, the fourth hierarchical data D24 is output from the decoder 24.

The output of the decoder 23 is supplied to a fourth hierarchical data D obtained from the interpolation filter 26 in an adder circuit 29.
Thus, the third hierarchical data D23 is restored. Similarly, the output of the decoder 22 is added to the interpolation data of the third hierarchical data D23 obtained from the interpolation filter 27 in the adding circuit 30, whereby the second hierarchical data D22 is restored. Further, the output of the decoder 21 is added to the interpolation filter 2 in the addition circuit 31.
8 is added to the interpolated data of the second hierarchical data D22, whereby the first hierarchical data D21 is restored.

[0010]

However, in an image coding apparatus for realizing such a hierarchical coding method, since input image data is divided into a plurality of hierarchical data and coded, the data amount is inevitably limited to hierarchical components. There is a problem that increases.

The present invention has been made in consideration of the above points, and is intended to propose an image processing apparatus and an image processing method capable of reducing the amount of data to be transmitted even when image data is hierarchically encoded. .

[0012]

In order to solve this problem, the present invention processes image data D31 comprising a plurality of pieces of hierarchical information from the highest hierarchical information having the lowest resolution to the lowest hierarchical information having the highest resolution. the image processing apparatus 40, the pixel value of the pixel of interest m included in the top-level hierarchy block comprising the highest hierarchical quantization characteristic p _a at the time of quantizing the uppermost hierarchy data and the quantization target of the highest hierarchy information , Neighboring pixels X0 to X7, X0 to X3, X0 to the pixel of interest m
The highest level quantization characteristic determining means 60 for determining by calculation the pixel values of X4, uppermost quantization means for quantizing the uppermost hierarchy block of the uppermost layer information by using the top-level hierarchy quantization characteristic p _A 49 and activity determining means 49, 51, 5 for determining the activity of a predetermined hierarchical block to be quantized, which includes a plurality of pixels of hierarchical information of a predetermined hierarchical level.
When the activity is high, the lower-layer quantization characteristic when quantizing the layer information of the lower layer than the predetermined layer is coarse, and when the activity is low, the lower-layer quantization characteristic is changed to 3, 55, 57. Lower layer quantization characteristic determining means 49, 51, 53, 55, 57 to be not coarse
And a lower layer quantization means 4 for quantizing lower layer blocks of lower layer information using lower layer quantization characteristics.
9, 51, 53, 55 and 57 are provided.

In the present invention, the image processing apparatus 30 that processes image data D31 including a plurality of pieces of hierarchical information from the highest hierarchical information having the lowest resolution to the lowest hierarchical information having the highest resolution is provided with the highest hierarchical information. A plurality of pixels X0 to X included in the highest hierarchical block to be quantized.
By 3 averaging processing, and hierarchy information generating means for generating a virtual upper hierarchy data M lower than the resolution of the highest hierarchy information, the highest layer quantization characteristic p _A at the time of quantizing the uppermost hierarchy data The highest floor determined by calculating the pixel values X0 to X3 of each pixel included in the highest hierarchy block of the highest hierarchy information and the pixel value of the corresponding pixel M of the virtual higher hierarchy information corresponding to the highest hierarchy block. a layer quantization characteristic determining means, the highest quantizer 49 for quantizing the uppermost hierarchy block of the uppermost layer information by using the top-level hierarchy quantization characteristic p _a, a plurality of pixels of the hierarchical information of a predetermined hierarchy Activity determining means 49, 51, 53, 55 for determining the activity of a predetermined hierarchical block to be quantized.
57, when the activity is high, the lower layer quantization characteristic when quantizing the layer information of the lower layer than the predetermined layer is assumed to be coarse, and when the activity is low, the lower layer quantization characteristic is not coarse. Lower-layer quantization characteristic determining means 49, 51, 53, 55, and 57, and lower-layer quantization means 49, 51, 5 for quantizing the lower-layer blocks of the lower-layer hierarchy information using the lower-layer quantization characteristics.
3, 55, and 57 are provided.

[0014] Furthermore, in the present invention, it was to use a quantization step width p _A as quantization characteristic.

[0015] Furthermore, in the present invention, the quantization step width p _A at the time of quantizing the uppermost hierarchy data, and as determined by the following equation.

(Equation 2) Here p _A represents the quantization step width for quantizing the uppermost hierarchy data, K is represents the number of quantization bits, n represents the number of pixels near the pixel, m represents the pixel value of the pixel of interest , X
_i represents the pixel values of the neighboring pixels, w _i represents the weight corresponding to the distance to the neighboring pixels from the target pixel.

Further, in the present invention, the activity judging means 49, 51, 53, 55, and 57 reflect the activity of the quantized value of each pixel included in the predetermined hierarchical block of the predetermined hierarchical information. Was determined.

[0017]

Therefore, when processing the image data D31 composed of a plurality of pieces of hierarchical information from the highest-level hierarchical information having the lowest resolution to the lowest-level hierarchical information having the highest resolution, it is necessary to quantize the highest-level hierarchical information. and the pixel value of the pixel of interest m included in the top hierarchy block the uppermost layer quantization characteristic p _a becomes a quantization target of the highest hierarchy information, neighboring pixels X0~X7 of the target pixel m, X0 to X3, X0 To the pixel values of X4 to X4, and the determined highest-layer quantization characteristic p
_A is used to quantize the highest hierarchical block of the highest hierarchical information, determine the activity of a predetermined hierarchical block to be quantized comprising a plurality of pixels of the hierarchical information of the predetermined hierarchy, and determine that the determined activity is high. The lower layer quantization characteristic when quantizing the layer information of the lower layer than the predetermined layer is assumed to be coarse, and when the activity is low, the lower layer quantization characteristic is assumed to be not coarse, and the lower layer quantization characteristic is determined. Is used to quantize the lower layer blocks of the lower layer information, the respective layer information D41 to D4
The quantization characteristic _{p A} at 4 and D35, each layer information D
41 to D44 and D35 can be determined, and thus image quality degradation during quantization can be reduced.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

(1) Principle of Hierarchical Coding FIG. 1 shows, as a whole, the principle of hierarchical coding according to the present invention, in which a still image such as a high definition television signal is hierarchically coded and compressed. In this hierarchical coding, upper hierarchical data is created by a simple arithmetic average of lower hierarchical data, and lower hierarchical data to be transmitted is reduced, thereby realizing a hierarchical structure without increasing the amount of information. In addition, for decoding from the upper layer to the lower layer, the division is adaptively controlled based on the activity of each block, thereby reducing the information amount of the flat portion. Further, in the encoding of the difference signal performed for the lower layer, the quantization characteristic is switched for each block without an additional code based on the activity of the upper layer, thereby realizing high efficiency.

That is, in the hierarchical structure of the hierarchical coding,
First, the input high-definition television signal is defined as a lower layer, and four pixels X1 to X4 in a small block of 2 lines × 2 pixels of the lower layer are expressed by the following equation.

(Equation 5) The arithmetic average represented by is calculated, and the value m is set as the value of the upper hierarchy. In this lower hierarchy,

(Equation 6) As shown by, by preparing three pixels of difference values from the above-mentioned hierarchy, a hierarchy structure is formed with the same information charge as the original 4-pixel data.

On the other hand, when decoding the lower layer, three pixels X1
~ X3 is the following formula

(Equation 7) As shown by the above, the difference value Δ
Xi is added to obtain a decoded value E [Xi], and the remaining one pixel is expressed by the following equation.

(Equation 8) As shown by, the decoded value E [X4] is determined by subtracting the three decoded values of the lower layer from the average value m of the upper layer. Here, E [] means a decoded value.

Here, in this hierarchical coding, the resolution is quadrupled for each layer from the upper layer to the lower layer, but this division is prohibited in the flat part to reduce the redundancy. A flag for instructing the presence / absence of the division is prepared in units of 1 bit and block. The determination of the necessity of division in the lower hierarchy is determined as local activity, for example, by the maximum value of difference data.

Here, as an example of hierarchical coding, HD of ITE is used.
FIG. 2 shows a result of adaptive division in the case of performing 5-layer encoding using a standard image (Y signal). The ratio of the number of pixels in each layer when the threshold value for the maximum difference data is changed to the original number of pixels is shown. It can be seen that redundancy is reduced based on spatial correlation. Although the reduction efficiency changes depending on the image, if the threshold value for the maximum difference data is changed from 1 to 6, the average reduction rate becomes 28 to 69 [%].

Actually, the resolution of the lower hierarchical data is reduced to 1/4.
By doubling to create the upper layer data, at that time the lower layer encodes the difference data from the upper layer data,
The signal level width can be effectively reduced. FIG. 3 shows a case of five stages by the hierarchical coding described above with reference to FIG. 2. Here, the layers are named as first to fifth layers, counting from the lowest.

Compared to the original 8-bit PCM data,
The signal level width is reduced. Especially the first with a large number of pixels
Since the fourth to fourth layers are differential signals, a significant reduction can be achieved, and the subsequent quantization improves the efficiency. As can be seen from the table of FIG. 3, the dependence of the reduction efficiency on the picture is small and is effective for all pictures.

Further, by forming the upper layer by the average value of the lower layer, the lower layer is converted into the difference from the average value of the upper layer while the error propagation is stopped in the block, so that the efficiency is also improved. Can be. In practice, in hierarchical coding, there is a correlation between the activities between layers at the same spatial position, and by determining the quantization characteristics of the lower layer from the quantization result of the upper layer, the receiving side performs inverse quantization for inverse quantization. An adaptive quantizer that does not need to transmit quantization information (except for the initial value) can be realized.

In practice, an image is hierarchically coded based on the above-described five-stage hierarchical structure, is expressed in multi-resolution, and is subjected to adaptive division and adaptive quantization using the hierarchical structure, so that various HD standard images (8 Bit Y / PB / PR) to about 1 /
8 can be compressed. The additional code for each block prepared for adaptive division is subjected to run-length encoding in each layer in order to improve compression efficiency. In this way, an image with sufficient image quality can be obtained at each layer, and a good image with no visual deterioration can be obtained at the final lowest layer.

(2) Image Encoding Apparatus in Embodiment In FIG. 4, reference numeral 40 denotes an image encoding apparatus according to the present invention, and input image data D31 is input to a difference circuit 41 and an averaging circuit 42. As shown in FIG. 5, the averaging circuit 42 converts the four pixels X1 (1) to X4 (1) of the input image data D31, which is the first layer data as the lowest layer, from the pixels X1 (1) of the second layer data D32. 2) is generated. Pixels X2 (2) to X4 (2) adjacent to the pixel X1 (2) of the second hierarchy data D32 are similarly the first hierarchy data D31.
Is generated by averaging four pixels.

The second hierarchical data D32 is input to the difference circuit 43 and the averaging circuit 44. The averaging circuit 44 has a second
The third hierarchical data D is obtained by averaging four pixels of the hierarchical data D32.
33 is generated. For example, in the case shown in FIG. 5, the pixel X1 (3) of the third hierarchical data D33 is generated from the pixels X1 (2) to X4 (2) of the second hierarchical data D32, and
Pixels X2 (3) to X4 (3) adjacent to pixel X1 (3)
Is also generated by averaging four pixels of the second hierarchy data D32.

The third hierarchical data D33 is input to the difference circuit 45 and the averaging circuit 46. The averaging circuit 46 generates the fourth layer data D34 including the pixels X1 (4) to X4 (4) as shown in FIG. 5 by averaging four pixels of the third layer data D33 in the same manner as described above. The fourth hierarchical data D34 is input to the difference circuit 47 and the averaging circuit 48. The averaging circuit 48 generates fifth hierarchical data D35 which is the highest hierarchical level by averaging four pixels of the fourth hierarchical data D34. As shown in FIG. 5, the pixel X1 (5) of the fifth hierarchical data D35 is generated by averaging the four pixels X1 (4) to X4 (4) of the fourth hierarchical data D34.

Accordingly, the first to fifth hierarchical data D31 to D3
Assuming that the block size of the first hierarchy data D31, which is the lowest hierarchy, is 1 × 1, the second hierarchy data D32 is 1/2 × 1/2 and the third hierarchy data D33
Is 1/4 × 1/4, and the fourth hierarchical data D34 is 1/8 × 1
/ 8, the fifth hierarchical data D35, which is the highest hierarchical data, is 1/16 × 1/16.

For example, when the upper layer data is generated by averaging the spatially corresponding lower layer data by four pixels, if the upper layer data is M and the lower layer pixel values are a, b, c, and d, the transmission pixel is , Upper layer data M and lower layer pixels a, b, and c. That is, using M, a, b, c, and d, the following equation:

(Equation 9) The non-transferred pixel d can be easily restored on the decoder side by the arithmetic expression represented by

FIG. 6 shows a schematic diagram of the relationship between the hierarchies for an example of four hierarchies. Here, each layer data is the lower layer 4
It is generated by pixel averaging, and all data can be restored by the arithmetic expression shown in Expression (5) without transmitting the data in the hatched portion in the figure. As a result, in the image coding apparatus 40, the number of pixels to be coded by the following coder can be reduced, so that the compression efficiency can be prevented from lowering even when coding is performed after being decomposed into a plurality of hierarchical images. It has been made like that.

Here, in the image encoding device 40, the fifth hierarchical data D35 is generated by compressing and encoding the fifth hierarchical data D35 by the encoder 49. Further, the image encoding device 40 performs a difference operation between adjacent layers on the above-described five layer data D31 to D35, thereby obtaining inter-layer difference data D44 and D44.
43, D42, and D41 are generated.

That is, in the image encoding device 40,
First, the fourth hierarchy data D34 is input to the difference circuit 47, and the fifth hierarchy compression-encoded data D55 is restored by the decoder 50 and input as restored data D36. Thus, the difference circuit 47 generates inter-layer difference data D44 between the fourth layer data D34 and the fifth layer data D35, and outputs this to the encoder 51. The encoder 51 generates fourth-layer compressed and encoded data D54 by compression-coding the inter-layer difference data D44.

Next, in the image encoding device 40, the third hierarchy data D33 is input to the difference circuit 45, and the fourth hierarchy compression encoded data D54 is restored by the decoder 52 to the fourth hierarchy data D34. Restored data D similar to
Enter 37. Thereby, the difference circuit 45 generates inter-layer difference data D43 between the third layer data D33 and the restored data D37 (that is, the fourth layer data D34), and outputs this to the encoder 53. The encoder 53 generates third-layer compressed encoded data D53 by compression-coding the inter-layer difference data D43.

Similarly, in the image encoding device 40,
The second hierarchy data D32 is input to the difference circuit 43, and the third hierarchy compression-encoded data D53 is restored by the decoder 54 to obtain the same restored data D as the third hierarchy data D33.
Enter 38. As a result, the difference circuit 43 generates inter-layer difference data D42 between the second layer data D32 and the restored data D38 (that is, the third layer data D33), and outputs this to the encoder 55. The encoder 55 compresses and codes the inter-layer difference data D42 to generate second-layer compressed and coded data D52.

Finally, the image encoding device 40 inputs the first hierarchical data D31 to the difference circuit 41,
The hierarchical compression coded data D52 is restored by the decoder 56, and the same restored data D39 as the second hierarchical data D32 is input. Thereby, the difference circuit 41 stores the first hierarchical data D3
1 and the restored data D39 (that is, the second hierarchical data D3).
2), and outputs the difference data D41 between layers to the encoder 57. The encoder 57 outputs the difference data D4 between layers.
1 is compression-encoded to generate first-layer compression-encoded data D51.

As described above, in the image encoding device 40, the fifth hierarchical compression encoded data D55, the fourth hierarchical compressed encoded data D54, the third hierarchical compressed encoded data D53,
The second hierarchy compression encoded data D52 and the first hierarchy compression encoded data D51 are sequentially generated in this order.

Here, each of the decoders 52, 54 and 56 receives the compression-encoded data D54, D53 or D52 to be decoded from the corresponding encoder 51, 53 or 55, respectively, and the code of the next higher hierarchy. Vessel 49, 51 or 53
By receiving the quantization information E0, E1, or E2 used in the above, the compressed encoded data D54, D53, or D52 is decoded. Also, each of the decoders 52, 54, and 56 receives the restored data D3 from the decoder 50, 52, or 54 in the next higher layer.
6, by receiving D37 or D38, the hierarchical data D34, D33 or D32 before the difference is created.

In practice, each of the decoders 52, 54, 56
It is configured as shown in FIG. Here, the decoder 52 will be described for simplification. The decoder 52 is a decoding circuit 5
The second layer compressed encoded data D54 is decoded by receiving the fourth layer compressed encoded data D54 and the quantization information E0 used for generating the fourth layer compressed encoded data D54 in 2A. As a result, for example, FIG.
X1 (4) -X1 (5), X2 (4) -X1
(5) Output values of X3 (4) -X1 (5) are obtained.
This output value is supplied to the restoration data D in the subsequent addition circuit 52B.
36 and X1 (4), X2 (4),
The output value of X3 (4) is obtained. Difference value generation circuit 52C
Are X1 (4), X2 (4), X3 (4) and X1 (5)
Is used to generate a non-transmission pixel X4 (4) by performing an operation based on the expression (5). Therefore, the following synthesis circuit 52
From D, the fourth hierarchy data X1 (4), X2
(4), X3 (4), and X4 (4) are generated and supplied to the difference circuit 45.

The encoders 51, 53, 55, and 57 receive the quantized information E0, E1, E2, or E3 output from the adjacent higher-layer encoders 49, 51, 53, and 55, respectively. The encoding is performed based on E0, E1, E2, and E3, and the quantization characteristic of the lower layer is determined.

(3) Selection of quantization step width Here, the encoders 49, 51, 53, 55 and 57 each have a quantizer. In the image encoding device 40, if the lower layer data area corresponding to the upper layer data is defined as a "block", the characteristics of the data change in the block are grasped by the activities of the inter-layer difference data D41 to D44 in the block. The characteristics of the quantizer are determined based on the data characteristics.

In the case of the embodiment, a 2-bit quantizer is used as a quantizer, and the difference value is +1 in this quantizer.
FIG. 8 shows the quantization characteristics when 2-bit quantization is performed on the difference data between layers in the range of 28 to -128. In this way, the difference value is quantized from 0 to 3. Further, in the case of the embodiment, since the upper layer data of each layer data is generated by averaging 2 × 2 four pixels, there are four pixels in the lower layer of each block.

Here, as a method of determining the quantization characteristic of each quantizer, first, the difference data between layers is 2-bit quantized according to the quantization step width determined in the upper layer. At this time, one of the quantization values 0 to 3 shown in FIG. 8 is generated. Here, the distribution of the quantized values of the four pixels in the block indicates the activity in the block, so that the quantization step width of the next layer is determined based on the quantized value distribution of the four pixels. Thus, by selecting the quantization step width based on the quantization value distribution in the block, an additional code indicating the type of the quantizer becomes unnecessary.

As a result, in the image encoding device 40,
The compression efficiency of the encoders 49, 51, 53, 55, and 57 can be improved, and image quality degradation during compression encoding processing can be reduced. In practice, the encoder 5
1, 53, 55 and 57 are configured as shown in FIG. FIG. 9 shows the configuration of the encoders 53 and 55 for simplification.

That is, the inter-layer difference data D43 sent to the encoder 53 is input to the quantizer 53A, and the quantizer 53A performs the inter-layer difference based on the quantization information E1 received from the encoder 51 of the upper layer. The data D43 is quantized. Here, the quantization information E1 is a quantization step width. The quantized value obtained as a result is supplied to the following code word allocating circuit 5.
5B, an optimal code word that reduces the amount of information is assigned and output as compressed coded data D53.

The quantized value is given to the distribution state determination circuit 53D, which determines the distribution of the quantization value, and outputs the determination result obtained by the quantization width selection circuit 5D.
Give to 3C. The quantization width selection circuit 53C receives the distribution determination result and the quantization information E1, selects a new quantization step width based on the distribution determination result, and uses this as the quantization information E2.
Is transmitted to the encoder 55 of the adjacent lower layer.

Similarly, the encoder 55 converts the quantization information (quantization step width) E2 generated by the encoder 53 into a quantizer 5
5A, and uses the quantization step width generated in the upper layer by the quantizer 55A to generate the difference data D between layers.
42 is quantized, and based on the quantized value thus obtained, the compressed encoded data D5
2 and the distribution state determination circuit 55D determines the distribution state of the quantized values. The quantization width selection circuit 55C includes:
Upon receiving the distribution determination result and the quantization information E2, a new quantization step width is selected based on the distribution determination result, and this is transmitted to the adjacent lower-layer encoder 57 as quantization information E3.

Next, distribution state determination circuits 53D, 55D,.
.. And the quantization width selection circuits 53C, 55C,. The distribution state determination circuits 53D and 55D classify the respective quantized values 0 to 3 into sections A and B as shown in FIG. That is, when the quantization value is 1 or 2, this is set as the section A, and the quantization value is 0.
Or, if it is 3, this is set as section B.

As a characteristic of a quantizer for efficiently forming a high-quality image, a block having a high activity uses a coarse quantizer having a large quantization step width, whereas a block having a low activity has a low activity. In the block, the following rules are set in consideration of the necessity of using a quantizer having a narrow quantization step width.

That is, in the quantizer, when the quantization step width of the upper layer is p0 and the quantization step width of the lower layer is p1, Rule 1) When all the quantized values of four pixels belong to section B , P1 = 2 × p0 Rule 2) When the quantized values of four pixels belong to the section A and the section B, p1 = p0 Rule 3) When all the quantized values of the four pixels belong to the section A, p1 = p0 / 2 , The quantization step width p1 of the lower hierarchy is determined.

Here, rule 1 corresponds to the case where the activity in the block is large. In this case, the function of increasing the quantization step width of the next lower layer and suppressing the quantization distortion is performed. In addition, rule 2 can be considered as an activity state in a block in many cases. However, since the absolute value of the data in section B is generally considered not to be large due to spatial correlation, the quantization step width of the upper layer is held. Perform the function of Further, Rule 3 corresponds to the case where the activity in the block is small. In this case, the width of the quantization step of the next lower hierarchy is reduced, and the function of suppressing the image quality deterioration in the flat portion is achieved. As described above, in the image encoding device 40, the quantization step width of the lower layer is determined according to the activity in the block of the upper layer.

[0054] (4) In addition to the selection such a configuration of the initial value of the quantization step width, the image encoding apparatus 40, the initial value setting circuit for setting the quantization step width P _A in the encoder 49 of the uppermost hierarchy 60 Having. Incidentally, in the image encoding device 40, it is necessary to set a quantization step width p _A (hereinafter, referred to as an initial value of the quantization step width) in the fifth hierarchical data D35 (that is, the highest hierarchical data). The initial value p _A of the quantization step width, although depending on the quantization bit number to be set, in the case of 2-bit quantization, it is considered to use a fixed value of for example 32.

[0055] For example, in the image encoding apparatus 40, the initial value setting circuit 60 Yotsute, by setting the initial value p _A of the quantization step width adaptive to the image in the following manner, quantum In this case, it is possible to further reduce the image quality deterioration at the time of image formation. That is, the initial value setting circuit 60
Is, as shown in FIG. 10, the data m of interest in the highest hierarchy.
When it is adapted to determine an initial value p _A based on a relationship between the neighboring data X0~X7 of the attention data m.

Specifically, assuming that the data value of interest is m and the eight neighboring data values are X _i (i = 0 to 7), the initial value p _A of the quantization step width is expressed by the following equation:

(Equation 10) It is made to ask according to. Here, the coefficient 1/4 in the equation (6) corresponds to a 2-bit 4-code.
Equation (6) is based on the idea of estimating the average difference value between the target data m and the neighboring data X _i (i = 0 to 7) in the highest hierarchy as the quantization target section.

(5) Operation of Embodiment In the above configuration, the image coding apparatus 40 sequentially generates the first to n-th hierarchical compression code data according to the processing procedure shown in FIG. Case n = 5). That is, the image encoding apparatus 40 enters the hierarchy counter I at step SP2, assuming n layers.
Is input to n-1.

The image encoding device 40 performs the following step SP
In step 3, the averaging circuits 42, 44, 46, and 48 generate hierarchical data D31 to D35 for n layers, and the process proceeds to step SP4. Here, the image encoding device 40 sets the initial value p _A of the quantization step width as the attributes of the highest hierarchy by the method described above. In the following step 5, the image encoding device 40 performs the encoding and decoding of the highest hierarchical data D35.

Next, the image encoding device 40 executes step SP6.
First, an inter-layer difference operation is performed by the difference circuit 47, 45, 43 or 41, and the quantization step width of the upper layer is applied to the inter-layer difference data D44, D43, D42 or D41 generated at this time. Is performed.
Next, in step SP7, the image encoding device 40 determines the distribution of the quantized value in the block, and in step SP8, performs the determination according to the above-described rules 1, 2, and 3, and based on the determination result. Then, the quantization step width is determined and transmitted to the lower layer.

The image encoding device 40 performs the following step SP
At 9, the encoding and decoding of the inter-layer difference data D44, D43, D42 or D41 are executed using the quantization step width determined at step SP8. The image encoding device 40 decrements the layer counter I in step SP10, and determines whether or not the layer counter I is 0 in the next step SP11.

If a positive result is obtained here, this means that the processing of all the layers has been completed, and at this time, the image coding apparatus 40 moves to step SP12 and ends the processing procedure. On the other hand, if a negative result is obtained in step SP11, the image encoding device 40 sets the
Returning to P5, the above-described step S is performed for the next lower hierarchy.
The processing of P5 to step SP10 is repeated.

(6) Effects of Embodiment According to the above configuration, the initial value p _A of the quantization step width p is obtained.
Is selected according to the average difference value between the target data m and the neighboring data X _i (i = 0 to 7) adjacent to the target data m, thereby further reducing the image quality degradation at the time of quantization. It is possible to realize an image encoding device 40 that can perform the operations.

(7) Other Embodiments (7-1) In the above embodiment, quantization is performed based on the data of interest m in the highest hierarchy and eight neighboring data X0 to X7 adjacent to the data of interest m. has dealt with the case of selecting the initial value p _a of step width, the present invention is not limited to this, for example, as shown in FIG. 12, the horizontal direction and relative to the attention data m and the attention data m in the highest level Four neighboring data X1, X adjacent in the vertical direction
3, and X0 and X2 may be used.

In this case, the initial value p _A of the quantization step width is set.
Indicates that the data value of interest is m and the four neighboring data values are X _i (i = 0
~ 3), the following equation:

[Equation 11] Can be obtained by Here, the coefficient 1/4 in the equation (7) corresponds to four 2-bit codes. The basic concept is the same as when using eight adjacent data, but the parameter of division is 4 because four neighboring data are used.

(7-2) In the above embodiment,
With use of the quantizer 2 bits has dealt with the case of obtaining the initial value p _A of the quantization step width with eight neighboring data X _i adjacent to the attention data m _(i = 0~7), the The present invention is not limited to this, and the coefficient in the equation (6) is changed to the reciprocal of the number of quantization codes in accordance with the number of quantization bits, and the number of neighboring data necessary for the division parameter is used. manner it becomes possible to set the initial value p _a.

That is, the number of quantization bits of the quantizer is k,
The data value of interest is m, and the data values of neighboring n are X _i (i = 0 to n)
When -1), the initial value p _A of the quantization step width is expressed by the following equation,

(Equation 12) Can be obtained by

(7-3) In the above embodiment,
Initial value p _A using neighboring data adjacent to target data m
It is described for determining the present invention is not limited to this, as shown in FIG. 13, be calculated initial value p _A based from the target data m to the image data X0~X5 having a predetermined distance good. In this case, the number of quantization bits of the quantizer is k, the data value of interest is m, the number of image data to be referenced is n, and the image data value to be referenced is X _i (i = 0 to 0).
4), assuming that the spatial distance weight from the target image data m to each reference image data X _i is w _i (i = 0 to 4), the initial value p _A of the quantization step width is represented by the following equation:

(Equation 13) Can be obtained by

[0068] (7-4) Further, in the present invention, with respect to the uppermost hierarchy data initial value p _A of the quantization step width is set, further virtually generates upper layer data, the virtual upper hierarchy data When, by operation of a plurality of pixels in the uppermost hierarchy data corresponding to the virtual upper hierarchy data may be generated an initial value p _a of the quantization step width. FIG. 14 shows an example of the arrangement of the virtual upper hierarchical data and the uppermost hierarchical data at this time. In this example, virtual upper-layer data M (FIG. 14A) is generated from the highest-layer data (FIG. 14B) by four-pixel averaging as in the other hierarchical data generation methods. .

Here, assuming that a 2-bit quantizer is used as the quantizer, the virtual upper layer data value is M, and the uppermost layer data value is X _i (i = 0 to 3), the quantization step width is the initial value _{p a} is expressed by the following equation,

[Equation 14] Can be obtained by The coefficient 1/4 in equation (10) corresponds to 4 codes of 2 bits, and the division parameter is 4 because 4 data of the highest hierarchy is used. The basic idea in this case is
The fluctuation range of the highest hierarchical data is used as a quantization section. Since this quantization section is quantized by a certain number of quantization bits, the quantization step width becomes narrower as the number of quantization bits increases.

When this method is generally considered, the coefficient is changed to the reciprocal of the number of quantization codes in accordance with the number of quantization bits, and the parameter of division is used as the parameter of the uppermost layer related to the generation of virtual upper layer data. by placing the number of data, it is possible to set the generically initial value p _a. That k the number of quantization bits, a virtual upper hierarchy data value M, the relevant top-level hierarchy data value when the _{X i (i = 0~n-1} ), the initial value p _A of the quantization step width, the following formula,

(Equation 15) Can be obtained by

[0071]

As described above, according to the present invention, when processing image data consisting of a plurality of pieces of hierarchical information from the highest hierarchical information having the lowest resolution to the lowest hierarchical information having the highest resolution, The quantization property of the uppermost layer at the time of quantizing the hierarchical information is determined by calculating the pixel value of the pixel of interest included in the uppermost layer block to be quantized of the uppermost layer information and the pixel value of the pixel adjacent to the pixel of interest. The highest hierarchical block of the highest hierarchical information is quantized using the determined highest hierarchical quantization characteristic, and a predetermined hierarchical block to be quantized comprising a plurality of pixels of the hierarchical information of the predetermined hierarchy is determined by the operation. And if the determined activity is high, the lower layer quantization characteristic when quantizing the layer information lower than the predetermined layer is coarse, and the activity is determined. When it is low, the lower layer quantization characteristics are not coarse, and the lower layer blocks of the lower layer hierarchy information are quantized using the lower layer quantization characteristics. Can be determined to a value adapted to each layer information, and thus an image processing apparatus and an image processing method capable of reducing image quality deterioration at the time of quantization can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining hierarchical data generated by an image encoding device according to the present invention.

FIG. 2 is a table showing a result of adaptive division in an HD standard image.

FIG. 3 is a chart showing the standard deviation of the signal level of each layer in the HD standard image.

FIG. 4 is a block diagram showing a circuit configuration of an embodiment of an image encoding device according to the present invention.

FIG. 5 is a schematic diagram used to describe an operation of generating hierarchical data.

FIG. 6 is a schematic diagram for explaining a hierarchical structure of hierarchical data.

FIG. 7 is a block diagram showing a configuration of a decoder.

FIG. 8 is a schematic diagram illustrating characteristics of a quantizer according to the embodiment.

FIG. 9 is a block diagram showing a configuration of an encoder.

FIG. 10 is a schematic diagram for explaining initialization of a quantization step width according to the embodiment;

FIG. 11 is a flowchart for explaining the operation of hierarchical coding.

FIG. 12 is a schematic diagram for explaining initialization of a quantization step width according to another embodiment.

FIG. 13 is a schematic diagram for explaining initialization of a quantization step width according to another embodiment.

FIG. 14 is a schematic diagram for explaining initialization of a quantization step width according to another embodiment.

FIG. 15 is a block diagram showing a conventional image encoding device.

FIG. 16 is a block diagram showing a conventional image decoding apparatus.

[Explanation of symbols]

40 image encoding device, 41, 43, 45, 47 ...
Difference circuit, 42, 44, 46, 48 ... Averaging circuit, 4
9, 51, 53, 55, 57 ... encoders, 50, 52,
54, 56... Decoders, D31 to D35... Hierarchical data, D41 to D44... Inter-layer difference data, D51 to D
55 ... Hierarchical compression encoded data.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N ^7/ 24-7/68 H04N 1/41-1/419

Claims (7)

(57) [Claims] 1. Resolution from highest hierarchical information having the lowest resolution
Lowest level information with the highest degreeFor up toFrom multiple layers of information
Processing device for processing different image dataAnd Top layer quantization when the above top layer information is quantized
The characteristic is the top-level floor for quantization of the top-level information.
The pixel value of the pixel of interest included in the layer block and the pixel of interest
The highest order determined by the operation with the pixel value of the neighboring pixel
Layer quantization characteristic determining means; The above-mentioned top-layer information using the above-mentioned top-layer quantization characteristic
Top-level quantizer that quantizes the top-level block of
Steps and A quantization pair consisting of a plurality of pixels of the above-mentioned hierarchy information of a predetermined hierarchy
An activity that determines the activity of a given hierarchical block of an elephant
Activity determination means; If the activity is high,
Lower layer quantum when quantizing the above layer information of the lower layer
When the activity is low and the activity is low
Lower-level quantization characteristics that are not coarse
Means for determining a hierarchical quantization characteristic; Using the lower layer quantization characteristic, the lower layer
Lower layer quantization to quantize lower layer blocks of layer information
Means Equipped with An image processing apparatus characterized by the above-mentioned. 2. Resolution from highest hierarchical information having the lowest resolution
Lowest level information with the highest degreeFor up toFrom multiple layers of information
Processing device for processing different image dataAnd The top layer block to be quantized for the above top layer information
By averaging a plurality of pixels included in Tsuk,
A virtual upper floor lower than the resolution of the uppermost hierarchy information
Layer information generating means for generating layer information; Top layer quantization when the above top layer information is quantized
The characteristics are described in the top-level block of the top-level information.
And the pixel value of each pixel included in the
Pixel of the corresponding pixel of the above virtual upper layer information corresponding to Tsuk
Determining method of the highest hierarchical quantization characteristic determined by operation with values
Steps and The above-mentioned top-layer information using the above-mentioned top-layer quantization characteristic
Top-level quantizer that quantizes the top-level block of
Steps and A quantization pair consisting of a plurality of pixels of the above-mentioned hierarchy information of a predetermined hierarchy
An activity that determines the activity of a given hierarchical block of an elephant
Activity determination means; If the activity is high,
Lower layer quantum when quantizing the above layer information of the lower layer
When the activity is low and the activity is low
Lower-level quantization characteristics that are not coarse
Means for determining a hierarchical quantization characteristic; Using the lower layer quantization characteristic, the lower layer
Lower layer quantization to quantize lower layer blocks of layer information
Means Equipped with An image processing apparatus characterized by the above-mentioned. 3. The quantization characteristic is a quantization step width.
The image processing apparatus according to claim 1 or claim 2, characterized in that that. 4. The method according to claim 1, wherein said uppermost hierarchical information is quantized.
The quantization step width is determined by the following equation.
The image processing apparatus according to claim 3, wherein: (Equation 1) Here p _A the above when quantizing the uppermost hierarchy data
Represents the quantization step width, K represents the number of quantization bits,
n represents the number of neighboring pixels, and m represents the number of pixels of interest.
X _i represents the pixel value of the neighboring pixel, and
_i depends on the distance from the target pixel to the neighboring pixel
Represents the weight. 5. The activity judging means according to claim 1, wherein:
Included in the predetermined hierarchy block of the hierarchy information of the hierarchy
To reflect the distribution of the quantized value of each pixel
Claim, characterized in that determining the accession Teibitei 1 also
The image processing apparatus according to claim 2. 6. Resolution from the highest hierarchical information having the lowest resolution
Lowest level information with the highest degreeFor up toFrom multiple layers of information
Image processing method for processing different image dataAnd Top layer quantization when the above top layer information is quantized
The characteristic is the top-level floor for quantization of the top-level information.
The pixel value of the pixel of interest included in the layer block and the pixel of interest
The highest order determined by the operation with the pixel value of the neighboring pixel
Layer quantization characteristic determination step; The above-mentioned top-layer information using the above-mentioned top-layer quantization characteristic
Top quantization block that quantizes the top hierarchy block of
And steps A quantization pair consisting of a plurality of pixels of the above-mentioned hierarchy information of a predetermined hierarchy
An activity that determines the activity of a given hierarchical block of an elephant
Activity determination steps, If the activity is high,
Lower layer quantum when quantizing the above layer information of the lower layer
When the activity is low and the activity is low
Lower-level quantization characteristics that are not coarse
A hierarchical quantization characteristic determination step; Using the lower layer quantization characteristic, the lower layer
Lower layer quantization to quantize lower layer blocks of layer information
Step and Equipped with An image processing method comprising: 7. Resolution from highest hierarchical information having the lowest resolution
Lowest level information with the highest degreeFor up toFrom multiple layers of information
Image processing method for processing different image dataAnd The top layer block to be quantized for the above top layer information
By averaging a plurality of pixels included in Tsuk,
A virtual upper floor lower than the resolution of the uppermost hierarchy information
A layer information generation step for generating layer information; Top layer quantization when the above top layer information is quantized
The characteristics are described in the top-level block of the top-level information.
And the pixel value of each pixel included in the
Pixel of the corresponding pixel of the above virtual upper layer information corresponding to Tsuk
By operation with value Quantization characteristic determination
And steps The above-mentioned top-layer information using the above-mentioned top-layer quantization characteristic
Top quantization block that quantizes the top hierarchy block of
And steps A quantization pair consisting of a plurality of pixels of the above-mentioned hierarchy information of a predetermined hierarchy
An activity that determines the activity of a given hierarchical block of an elephant
Activity determination steps, If the activity is high,
Lower layer quantum when quantizing the above layer information of the lower layer
When the activity is low and the activity is low
Lower-level quantization characteristics that are not coarse
A hierarchical quantization characteristic determination step; Using the lower layer quantization characteristic, the lower layer
Lower layer quantization to quantize lower layer blocks of layer information
Step and Equipped with An image processing method comprising: