JP3381007B2 - 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 Field of the Invention Conventional Technology (FIGS. 14 and 15) Means for Solving Problems to be Solved by the Invention (FIGS. 4, 9, and 11 to 11)
FIG. 13) Operation (FIGS. 4, 9, and 11 to 13) Embodiment (1) Principle of hierarchical coding (FIGS. 1 to 3) (2) Image coding apparatus (FIGS. 4 to 8) (FIG. 3) Image Decoding Device of Embodiment (FIGS. 9 to 13) (4) Effects of Other Embodiments of 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 in particular, it divides predetermined image data into a plurality of image data having different resolutions and decodes a plurality of hierarchically encoded data. It is suitable for application to an image decoding device and an image decoding method.

[0003]

2. Description of the Related Art Conventionally, there is an image encoding apparatus which divides predetermined image data into a plurality of image data having different resolutions and encodes the image data. This type of image coding apparatus is configured to hierarchically code input image data by using a hierarchical coding method such as pyramid coding. That is, in this image encoding device, the high-resolution input image data is used as the first layer data, and the second layer data having a lower resolution than the first layer data and the resolution higher than the second layer data. .. are sequentially recursively formed, and the plurality of hierarchical data are transmitted through one communication path or a transmission path formed of a recording / reproducing path.

Further, in the image decoding apparatus for decoding the plurality of hierarchical data, in addition to decoding all of the plurality of hierarchical data, one of the hierarchical data corresponding to the resolution of the television monitor corresponding to the respective hierarchical data is used. One of them may be selected and decoded. As a result, by decoding only the desired hierarchical data from the plurality of hierarchical data, it is possible to obtain the desired image data with the minimum required transmission data amount.

As shown in FIG. 14, in the image coding apparatus 1 which realizes, for example, four-layer coding as the hierarchical coding, the thinning filters 2, 3, 4 for three stages and the interpolation filters 5, 6, respectively. 7 and the reduced image data D2, D3, D4 having a sequentially lower resolution are formed by the thinning filters 2, 3, 4 of the respective stages for the input image data D1 and the reduced images are generated by the interpolation filters 5, 6, 7. Data D
2. Return D3, D4 to the resolution before reduction.

Input image data D1, each thinning filter 2
The outputs D2 and D3 of the output signals 3 and 3 and the outputs D5 to D7 of the interpolation filters 5 to 7 are input to the differential circuits 8, 9 and 10, respectively, thereby generating the differential 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
Areas of 4 are 1, 1/4, 1/16 and 1/64.

The difference data D8 to D10 obtained from the difference circuits 8 to 10 and the reduced image data D4 obtained from the thinning filter 4 are encoded by the encoders 11, 12, 13, and 14 and compressed. As a result, the first, second, third and fourth hierarchical data D11, D12, D13 having different resolutions from the respective encoders 11, 12, 13, 14 are applied.
And D14 are sent to the transmission line in a predetermined order.

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

The output of the decoder 23 is the fourth hierarchical data D obtained from the interpolation filter 26 in the adder circuit 29.
It is added with the interpolation data of 24, whereby 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 adder circuit 30, whereby the second hierarchical data D22 is restored. Further, the output of the decoder 21 is output by the adder circuit 31 to the interpolation filter 2
8 is added to the interpolated data of the second hierarchical data D22 to restore the first hierarchical data D21.

[0010]

However, in the image coding apparatus which realizes such a hierarchical coding method, since the input image data is divided into a plurality of hierarchical data for coding, only the hierarchical component data is inevitably obtained. There is a problem in that the amount of data increases and the compression efficiency decreases correspondingly as compared with a high efficiency coding method that does not use hierarchical coding. Further, when trying to improve the compression efficiency, there is a problem that image quality deterioration occurs.

The present invention has been made in consideration of the above points, and when the image data is hierarchically encoded and transmitted, the image processing apparatus and the image processing method can improve the compression efficiency and reduce the image quality deterioration. Is to propose.

[0012]

In order to solve such a problem, according to the present invention, a plurality of information from the lowest layer information having the lowest resolution to the lowest layer information having the highest resolution for expressing the image data D31 at a plurality of resolutions. Of the hierarchy information of the predetermined hierarchy, the activity of the block of the predetermined hierarchy to be quantized, which consists of a plurality of pixels of the hierarchy information of the predetermined hierarchy, is determined. When the activity is low, the quantization step width p is made small, and the quantization step width p is made small. By using the quantization step width p, each pixel included in the predetermined layer block and the lower layer Generated by quantizing the lower layer block to be quantized, which consists of multiple pixels corresponding to each layer information, and obtaining the quantized value The hierarchical coding data D51~D5
In the image processing apparatus 60 and the image processing method for decoding 5, the quantization step width p used when decoding the quantized value of the lower layer block is the predetermined layer obtained by decoding the layer information of the predetermined layer. The quantized decoded values e0 to e3 for the quantized values of the lower layer blocks are determined according to the block activity, and are suppressed as the quantized step width p used for decoding the quantized values increases. Decided.

Further, in the present invention, the image data D31
Of a plurality of layer information from the lowest layer information having the lowest resolution to the lowest layer information having the highest resolution. Activity is determined, and if the determined activity is high, the quantization step width p when quantizing the hierarchical information of the lower hierarchy than the predetermined hierarchy is increased, and if the activity is low, the quantization step width p p is made smaller, and the lower step block to be quantized, which is made up of a plurality of pixels corresponding to each pixel in the predetermined layer block and the lower layer hierarchy information, is quantized by using the quantization step width p. Hierarchical coded data D5 generated by obtaining a value
In the image processing device 60 and the image processing method for decoding 1 to D55, the quantization step width p used when decoding the quantized value of the lower layer block is calculated from the distribution of the quantized value of the layer information of the predetermined layer. Then, the quantized decoded values e0 to e3 corresponding to the quantized values of the lower layer blocks are determined so as to be suppressed as the quantization step width p used when decoding the quantized values increases.

Further, in the present invention, the distribution of the quantized value obtained by quantizing each pixel included in the predetermined hierarchical block of the predetermined hierarchical layer is reflected in the activity.

[0015]

[0016]

[0017]

Therefore, a plurality of pixels in the hierarchy information of a predetermined hierarchy among a plurality of hierarchy information from the lowest hierarchy information having the lowest resolution to the lowest hierarchy information having the highest resolution for expressing the image data D31 at a plurality of resolutions. The activity of a predetermined hierarchical block to be quantized is determined, and if the determined activity is high, the quantization step width p for quantizing the hierarchical information of a lower hierarchical layer than the predetermined hierarchical level is increased, and the activity is increased. If the value is low, the quantization step width p is reduced, and the quantization step width p is used to quantize each pixel included in the predetermined layer block and a plurality of pixels corresponding to the hierarchical information of the lower layer. Image processing for decoding the layer encoded data D51 to D55 generated by quantizing the lower layer block of In the apparatus 60 and the image processing method, the quantization step width p used when decoding the quantized value of the lower layer block is determined from the activity of the predetermined layer block obtained by decoding the layer information of the predetermined layer, Decoding is performed by suppressing the quantized decoded values e0 to e3 corresponding to the quantized value of the lower layer block as the quantization step width p used when decoding the quantized value increases. It is possible to obtain the image processing device 60 and the image processing method capable of reducing the image quality deterioration at the time.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(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 encoding, the upper layer data is created by a simple arithmetic average of the lower layer data, thereby realizing a hierarchical structure without an increase in the amount of information.
For decoding from the upper layer to the lower layer, the amount of information in the flat portion is reduced by adaptively controlling the division based on the activity of each block. Further, in the encoding of the differential signal performed for the lower layer, the efficiency is improved by switching the quantization characteristic for each block without additional code based on the activity of the upper layer.

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

[Equation 1] The arithmetic mean represented by is taken, and its value m is taken as the value of the upper hierarchy. In this lower hierarchy,

[Equation 2] As shown in, the difference value from the upper layer is prepared for three pixels, so that the hierarchical structure is configured with the same information amount as the original four pixel data.

On the other hand, when decoding the lower layer, 3 pixels X1
~ X3 is the following formula

[Equation 3] As shown by, each difference value Δ is added to the average value m of the upper hierarchy.
Xi is added to obtain the decoded value E [Xi], and the remaining one pixel is

[Equation 4] 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.

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

Here, as an example of hierarchical coding, HD of ITE is used.
FIG. 2 shows the adaptive division result when the standard image (Y signal) is used and five-layer coding is performed. The ratio of the number of pixels in each layer to the original number of pixels when the threshold value for the maximum difference data is changed is shown, and it can be seen that redundancy is reduced based on the spatial correlation. The reduction efficiency changes depending on the image, but 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 hierarchy data is ¼
By making the upper layer data by doubling, by encoding the difference data from the upper layer data in the lower layer at that time,
The signal level width can be effectively reduced. FIG. 3 shows the case of five stages by the hierarchical coding described above with reference to FIG. 2, and here, the layers are named from the lower layers to the first to fifth layers.

Compared to the 8-bit PCM data of the original image,
A reduction in signal level width can be seen. First with a large number of pixels
Since the ~ 4 layers are differential signals, a significant reduction can be achieved and efficiency is improved by subsequent quantization. As can be seen from the table of FIG. 3, the reduction efficiency has little dependence on the pattern, and is effective for all pictures.

Further, by forming the upper layer with the average value of the lower layer, the error propagation is stopped in the block, and the lower layer is converted into the difference from the average value of the upper layer, so that the efficiency is also provided. You can In actual upper layer coding, there is a correlation in the activities between layers at the same spatial position, and by determining the quantization characteristic of the lower layer from the quantization result of the upper layer, adaptive quantization that does not require additional code Can be realized.

In practice, an image is hierarchically encoded based on the above-mentioned five-stage hierarchical structure to be expressed in multi-resolution, and adaptive division and adaptive quantization using the hierarchical structure are performed to obtain various HD standard images (8 Y / PB / PR of bit is about 1 /
It can be compressed to 8. The additional code for each block prepared for adaptive division is run-length coded in each layer to improve compression efficiency. In this way, an image with sufficient image quality can be obtained in each layer, and a good image without visual deterioration can be obtained in the final lowest layer.

(2) Image Encoding Device In FIG. 4, reference numeral 40 denotes an image encoding device, and input image data D31 is input to the difference circuit 41 and the averaging circuit 42. As shown in FIG. 5, the averaging circuit 42 uses the input image data D3, which is the first layer data as the lowest layer.
The four pixels X1 (1) to X4 (1) of 1 generate the pixel X1 (2) of the second hierarchical data D32. Pixel X2 (2) to pixel X1 (2) adjacent to pixel X1 (2) of the second layer data D32
Similarly, X4 (2) is also generated by averaging four pixels of the first layer data D31.

The second layer data D32 is input to the difference circuit 43 and the averaging circuit 44. The averaging circuit 44 has a second
The third pixel 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 pixels X1 (2) to X4 (2) of the second layer data D32 generate the pixels X1 (3) of the third layer data D33, and
Pixels X2 (3) to X4 (3) adjacent to the pixel X1 (3)
Is also generated by averaging four pixels of the second layer data D32.

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

Here, the first to fifth hierarchical data D31 to D3
As for the block size of 5, if the block size of the first layer data D31 which is the lowest layer is 1 × 1, the second layer data D32 is 1/2 × 1/2 and the third layer data D33 is 1/3.
4 × 1/4, the fourth hierarchical data D34 is 1/8 × 1/8, and 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 four pixels of the spatially corresponding lower layer data, if the upper layer data is M and the lower layer pixel values are a, b, c and d, the transmission pixels are It will be good with 4 pixels. That is, using M, a, b, c, d, the following equation,

[Equation 5] The non-transferred pixel d can be easily restored on the decoding device side by the arithmetic expression represented by

A schematic diagram of the relationship between layers is shown in FIG. 6 for an example of four layers. Here, each layer data is 4
It is generated by pixel averaging, and all the data can be restored by the arithmetic expression shown in the equation (5) without transmitting the shaded data in the figure. As a result, in the image coding device 40, the number of pixels to be coded by the subsequent coder can be reduced, and thus, even when the coding is performed after disassembling into a plurality of hierarchical images, it is possible to avoid a decrease in compression efficiency. It is done like this.

In the image coding apparatus 40, the encoder 49 compresses and codes the fifth layer data D35 to generate fifth layer compression coded data D55. Further, in the image encoding device 40, inter-layer difference data D44, D is obtained by performing a difference operation between adjacent layers for each of the above five respective layer data D31 to D35.
43, D42, D41 are generated.

That is, in the image coding device 40,
First, the fourth layer data D34 is input to the difference circuit 47, and the fifth layer compression encoded data D55 is restored by the decoder 50 and input as the restored data D36. As a result, 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 compression-codes the inter-layer difference data D44 to generate fourth layer compression-coded data D54.

Next, in the image encoding device 40, the third layer data D33 is input to the difference circuit 45, and the fourth layer compression encoded data D54 is restored by the decoder 52 to obtain the fourth layer data D34. Restored data D similar to
Enter 37. As a result, 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 compression-codes the inter-layer difference data D43 to generate third-layer compression-coded data D53.

Similarly, in the image coding device 40,
The second layer data D32 is input to the difference circuit 43, and the third layer compression encoded data D53 is decompressed by the decoder 54 to restore the same decompressed data D33 as the third layer 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 compression-codes the inter-layer difference data D42 to generate second-layer compression-coded data D52.

Finally, the image encoding device 40 inputs the first layer data D31 to the difference circuit 41 and, at the same time, inputs the second layer data D31 to the second circuit.
The layer compression-encoded data D52 is decompressed by the decoder 56, and decompressed data D39 similar to the second layer data D32 is input. As a result, the difference circuit 41 causes the first layer data D3
1 and the restored data D39 (that is, the second layer data D3
Inter-layer difference data D41 with 2) is generated and output to the encoder 57. The encoder 57 uses the inter-layer difference data D4.
1 is compression-encoded to generate first layer compression-encoded data D51.

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

Here, the encoders 49, 51, 53, 55, 5
Each 7 has a quantizer. In the image encoding device 40, when the lower layer data area corresponding to the upper layer data is defined as "block", the characteristics of the data change in the block are grasped by the activity of the inter-layer difference data D41 to D44 in this block. , The characteristic of the quantizer is determined based on this data characteristic. Here, the activity is a correlation value that can be obtained from the maximum value, the average value, the sum of absolute values, the standard deviation, the n-th power sum, etc. of the inter-tier difference data D41 to D44 in a predetermined block.

In the case of the embodiment, a 2-bit quantizer is used as the quantizer, and the difference value is +12 in this quantizer.
FIG. 7 shows the quantization characteristics when two-bit quantization is performed on the difference data between layers in the range of 8 to -128. In this way, the difference value is quantized into 0 to 3. Further, in the case of the embodiment, since upper layer data is generated by averaging 4 × 2 × 2 pixels for each layer data, there are 4 pixels in the lower layer of each block.

Here, as a method of determining the quantization characteristic of each quantizer, first, the inter-layer difference data is 2-bit quantized according to the quantization step width determined in the upper layer. At this time, one of the quantized values 0 to 3 shown in FIG. 7 is generated. Here, since the distribution of the quantized values of the four pixels in the block represents the activity in the block, 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 intra-block quantized value distribution, an additional code indicating the type of quantizer becomes unnecessary. As a result, in the image encoding device 40, it is possible to improve the compression efficiency of the encoder and avoid image quality deterioration during the compression encoding process.

Next, the rule for determining the quantization step width in the embodiment will be described. First, the quantized values 0 to 3 are classified into sections A and B as shown in FIG. That is, when the quantized value is 1 or 2, it is set as the section A, and when the quantized value is 0 or 3, it is set as the section B.

Here, as a characteristic of the quantizer for efficiently forming a high-quality image, a coarse quantizer having a large quantization step width is used for a block having a high activity, and a low activity is used for the block. Considering that it is necessary to use a quantizer having a narrow quantization step width in the block, the following rules are set.

That is, the quantization step width of the upper layer is p
0, and the quantization step width of the lower layer is p1. Rule 1) When all the quantized values of 4 pixels belong to the section B,
p1 = 2 × p0 Rule 2) When the quantized values of 4 pixels belong to the intervals A and B, p1 = p0 Rule 3) When the quantized values of 4 pixels all belong to the interval A,
The quantization step width p1 of the lower layer is determined based on p1 = p0 / 2.

Here, rule 1 corresponds to the case where the intra-block activity is large, and in this case, the quantization step width of the next lower layer is increased to fulfill the function of suppressing the quantization distortion. Rule 2 can be considered as a state of intra-block activity in many cases, but it is generally considered that the absolute value of the data in section B is not large due to the spatial correlation, so the quantization step width of the upper layer is maintained. Fulfill the function of Furthermore, rule 3 corresponds to the case where the intra-block activity is small, and in this case, the quantization step width of the next lower layer is made small, and the function of suppressing the image quality deterioration in the flat part is fulfilled. As described above, in the image encoding device 40, the quantization step width of the lower layer is determined according to the intra-block activity of the upper layer.

In the image coding device 40, the number of quantization bits in each layer is determined according to the quantization step width of the adjacent upper layer. At this time, the image coding apparatus 40 determines the number of quantization bits in each layer in accordance with the distribution of the quantized values in the block according to the quantization step width of the upper layer. That is, in the image encoding device 40, the quantization bit number of the upper layer is
Assuming that t 0 is the quantization step width of the upper layer and p 0 is the quantization bit number weight determination function of the lower layer, and f 0 (.) is the quantization bit number of the lower layer, bit 1 is

[Equation 6] It is designed to be asked by. Here, the quantizing bit number weight determining function f0 (.multidot.) May have a characteristic as shown in FIG.

As a result, in the image coding device 40, when the quantization step width p0 of the upper layer is large,
Even in the lower layer, the number of quantization bits in the upper layer is maintained or increased. On the other hand, when the quantization step width of the upper layer is small, the quantization distortion is reduced in the lower layer even if the number of quantization bits is reduced. Therefore, the number of quantization bits is made smaller than that of the upper layer.

As a result, in the image coding apparatus 40, the number of quantization bits is adaptively determined by utilizing the relationship between adjacent layers, so that the number of transmission bits is effective in the state where the image quality is not deteriorated. The compression efficiency can be improved. Further, the number of quantization bits determined as described above can be determined on the decoding side from the combination of transmission data, so that it is not necessary to separately transmit an additional code indicating the number of quantization bits, and compression efficiency is not added. .

(3) Image Decoding Device of Embodiment The first to fifth layer compression coded data D51 to D55 which are encoded and transmitted as described above are image decoding devices 60 as shown in FIG. It is decoded by. Ie the first
-Fifth layer compression coded data D51 to D55 are decoders 61, 62, 63, 64 and 6 having decoding methods reverse to those of the encoders 57, 55, 53, 51 and 49, respectively.
Input to 5. As a result, the inter-layer difference data D56 of the first to fourth layers decoded by the decoders 61 to 64, respectively.
D59 is input to the first to fourth adder circuits 66 to 69, respectively.

The fifth layer compression coded data D55 is decoded by the decoder 65, and the resulting fifth layer data D60 is output as it is and the fourth addition circuit 6 is also provided.
9 is input. The fourth adding circuit 69 adds the fifth layer data D60 and the fourth layer inter-layer difference data D59 to restore the fourth layer data D64, which is output and also sent to the third adding circuit 68. . Similarly, the third adding circuit 68 adds the restored fourth layer data D64 and the third layer difference data D58 to restore the third layer data D63, and outputs it to output the second layer data D63. It is sent to the adder circuit 67. Similarly, the second and first addition circuits 67 and 66 restore the second layer data D62 and the first layer data D61 in this manner, and the first to fourth layers are thus restored.
The hierarchical data D61 to D64 and the fifth hierarchical data D65 are output.

Here, the decoders 61 to 64 are the encoder 57,
The decoded value of the quantized value generated by using 55, 53 and 51 is adaptively changed according to the conditions. FIG. 10 shows an example of a quantization target data distribution of inter-layer difference values when 2-bit quantization is performed. Since the inter-layer difference value is the difference value between the upper layer and the lower layer corresponding to each other, it is distributed symmetrically about positive and negative with 0 as the center. The position indicated by the broken line is the quantization boundary. Therefore, the quantized values of 0 to 3 in the 2-bit quantization have the distribution shown in the figure.

At this time, as is clear from FIG. 10, when the data to be quantized in the same quantized value interval is not uniform, the encoded data output from the general linear quantizer is decoded. Unlike, it is not always correct to select the median of the quantization step width as the decoded value. Therefore, in the decoders 61 to 64, FIG.
The quantized decoded value for the biased signal as shown in 0 is
It is adapted to be adaptively switched according to a quantized value at the time of encoding, a quantization step width, a number of quantization bits, a layer number and a combination thereof.

That is, the decoders 61 to 65 convert the quantized value into
code, the quantization step width is p, the number of quantization bits is bit,
When the layer number of the first to fifth layers is no and the quantized decoded value generation function is E (•), the quantized decoded value e is

[Equation 7] It is designed to be sought by.

In the case of the embodiment, the decoders 61 to 64 are the same as those of FIG.
The generation method of the quantized decoded value is determined based on the distribution of the quantization target signal indicated by 0. That is, the above-described image encoding device 40 generates an appropriate quantized value for the distribution of inter-layer difference values, so that the quantized decoded value is a standard signal distribution for various images. Can be assumed. Therefore, the decoders 61 to 64 can generate an appropriate quantized decoded value e from the quantized value, the quantized step width, the number of quantized bits, the layer number, etc., as shown in the equation (7). By the way, the layer number is added to the variable
This is because it corresponds to the case where the signal distribution depends on the number of layers.

As a result, the decoders 61 to 64 can set the quantized decoded values e0 to e3 according to the distribution of inter-layer difference values as shown in FIGS. 11 and 12, for example. That is, as shown in FIG. 11, when the spread of the inter-layer difference value is large, the quantized decoded values e0 to e corresponding to the distribution thereof are obtained.
Select 3. On the other hand, as shown in FIG. 12, when the spread of the inter-layer difference value is small, the quantized decoded values e0 to e3 corresponding to the distribution are selected.

As an example, FIG. 1 shows a characteristic example of the quantized decoded value e with respect to the quantization step width p by the decoders 61 to 64.
3 shows. In this way, in the decoders 61 to 64, the bias of the data within the quantization step width p is reflected in the quantization target data distribution (FIG. 10), so that the quantization step width p is quantized. The decoded value e is suppressed. Similarly, in the decoders 61 to 64, regarding the quantized value, the number of quantization bits, the layer number, etc., the quantized decoded value e is adaptively adjusted according to the bias of the quantization target data distribution in the image encoding device 40. Switching is performed so that decoding with little deterioration in image quality can be performed.

According to the above configuration, the quantized decoded value e is
Quantization value, quantization step width p, number of quantization bits,
By adaptively switching according to the layer number (first to fifth) and a combination thereof, the compression coded data D51 to D55 with a high compression rate can be decoded in a state in which image deterioration is reduced. The image decoding device 60 can be realized. Further, as a result, the image decoding device 60 capable of obtaining the quantized decoded value that matches the visual characteristics.
Can be realized.

(4) Other Embodiments In the above embodiment, the decoder 61 according to the present invention is used.
Up to 64 are used in the image decoding device 60, but the present invention is not limited to this and can be applied to various image decoding devices.

[0060]

As described above, according to the present invention, a predetermined number of pieces of hierarchical information from the lowest hierarchical information having the lowest resolution to the lowest hierarchical information having the highest resolution, which represents image data at a plurality of resolutions, is determined. The activity of a block of a predetermined layer to be quantized, which is composed of a plurality of pixels of layer information of a layer, is determined, and if the determined activity is high, a quantization step for quantizing layer information of a lower layer than the predetermined layer. Along with increasing the width, when the activity is low, the quantization step width is reduced, and using the quantization step width, each pixel included in the predetermined layer block and a plurality of pixels corresponding to the layer information of the lower layer An image processing for decoding the layer encoded data generated by quantizing the lower layer block of In the apparatus and the image processing method, the quantization step width used when decoding the quantized value of the lower layer block is determined from the activity of the predetermined layer block obtained by decoding the layer information of the predetermined layer, and the lower layer By reducing the quantized decoded value for the quantized value of the block as the quantized step width used when decoding the quantized value increases, the deterioration of image quality during decoding is reduced. It is possible to realize an image processing apparatus and an image processing method that can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining hierarchical data generated by an image encoding device.

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

FIG. 3 is a chart showing standard deviations of signal levels of respective layers in an HD standard image.

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

FIG. 5 is a schematic diagram for explaining a generation operation of hierarchical data.

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

FIG. 7 is a schematic diagram showing characteristics of a quantizer according to an embodiment.

FIG. 8 is a characteristic curve diagram showing characteristics of a quantization bit number weight determination function according to an embodiment.

FIG. 9 is a block diagram showing a circuit configuration of an image decoding apparatus according to an embodiment.

FIG. 10 is a frequency distribution diagram showing a relationship between a distribution state of quantization target data and a quantized value.

FIG. 11 is a frequency distribution diagram for explaining the setting operation of the quantized decoded value by the decoder.

FIG. 12 is a frequency distribution diagram for explaining the setting operation of the quantized decoded value by the decoder.

FIG. 13 is a characteristic curve diagram showing decoding characteristics of a decoder.

FIG. 14 is a block diagram showing a conventional image encoding device.

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

[Explanation of symbols]

40 ... Image coding device, 41, 43, 45, 47 ...
Difference circuit, 42, 44, 46, 48 ... Averaging circuit, 4
9, 51, 53, 55, 57 ... Encoder, 50, 52,
54, 56 ... Decoder, 60 ... Image decoding device, 61
~ 65 ... decoder, 66 ~ 69 ... adder circuit, D31 ~
D35, D60 to D61 ... Hierarchical data, D41 to D4
4 ... Difference data between layers, D51 to D55 ... Layer compression encoded data.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Shin Ito, Variable length code selection type DPCM coding method for image signals, IEICE Transactions, August 1989, Vol. J72-BI No. 8, p. 649-657 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N ^7/ 24-7/68 H04N 1/41-1/419

Claims (5)

(57) [Claims] 1.Resolution that represents image data in multiple resolutions
The lowest level of hierarchy information to the highest resolution of the bottom
Of the multiple layers of information up to the hierarchical information, the above of the predetermined layer
A predetermined hierarchical block to be quantized, which consists of multiple pixels of hierarchical information
The activity of the lock is determined and the determined activity
If there is a high level of
Increase the quantization step width when quantizing the above hierarchical information.
If the activity is low,
Decrease the quantization step width and reduce the quantization step width.
Using each of the pixels included in the predetermined hierarchical block
A plurality of corresponding hierarchical information of the lower hierarchy
Quantize the lower layer block consisting of pixels to be quantized
Hierarchical coding data generated by calculating the quantized value by
An image processing device for decoding data, When decoding the quantized value of the lower layer block
The quantization step width to be used is set to the floor of the predetermined hierarchy.
Above the specified hierarchical block obtained by decoding the layer information
Quantizer step width determiner determined from activity
Dan, Quantization recovery for the quantized value of the lower block
Signal is the above-mentioned quantum used when decoding the quantized value.
As the width of the conversion step increases,
Quantized decoded value determining means for determining It is characterized by
Image processing device. 2.Resolution that represents image data in multiple resolutions
The lowest level of hierarchy information to the highest resolution of the bottom
Of the multiple layers of information up to the hierarchical information, the above of the predetermined layer
A predetermined hierarchical block to be quantized, which consists of multiple pixels of hierarchical information
The activity of the lock is determined and the determined activity
If there is a high level of
Increase the quantization step width when quantizing the above hierarchical information.
If the activity is low,
Decrease the quantization step width and reduce the quantization step width.
Using each of the pixels included in the predetermined hierarchical block
A plurality of corresponding hierarchical information of the lower hierarchy
Quantize the lower layer block consisting of pixels to be quantized
Hierarchical coding data generated by calculating the quantized value by
Data An image processing device for encoding, When decoding the quantized value of the lower layer block
The quantization step width to be used is set to the floor of the predetermined hierarchy.
Quantization step width determined from distribution of quantized value of layer information
Decision means, Quantization recovery for the quantized value of the lower block
Signal is the above-mentioned quantum used when decoding the quantized value.
As the width of the conversion step increases,
Quantized decoded value determining means for determining It is characterized by
Image processing device. 3. The activity is at the predetermined level.
Each of the above pixels included in the constant hierarchy block is quantized.
The image processing apparatus according to claim 1 or claim 2, characterized that you expressed to reflect the distribution of quantized values obtained by the. 4.Resolution that represents image data in multiple resolutions
The lowest level of hierarchy information to the highest resolution of the bottom
Of the multiple layers of information up to the hierarchical information, the above of the predetermined layer
A predetermined hierarchical block to be quantized, which consists of multiple pixels of hierarchical information
The activity of the lock is determined and the determined activity
If there is a high level of
Increase the quantization step width when quantizing the above hierarchical information.
If the activity is low,
Decrease the quantization step width and reduce the quantization step width.
Using each of the pixels included in the predetermined hierarchical block
A plurality of corresponding hierarchical information of the lower hierarchy
Quantize the lower layer block consisting of pixels to be quantized
Hierarchical coding data generated by calculating the quantized value by
An image processing method for decoding data, When decoding the quantized value of the lower layer block
The quantization step width to be used is set to the floor of the predetermined hierarchy.
Above the specified hierarchical block obtained by decoding the layer information
Quantization step width determination step determined from activity
With a tape Quantization recovery for the quantized value of the lower block
Signal is the above-mentioned quantum used when decoding the quantized value.
As the width of the conversion step increases,
Quantized decoded value decision step to decide Comprises Special
CollectPictureImage processingMethod. 5.Resolution that represents image data in multiple resolutions
The lowest level of hierarchy information to the highest resolution of the bottom
Of the multiple layers of information up to the hierarchical information, the above of the predetermined layer
A predetermined hierarchical block to be quantized, which consists of multiple pixels of hierarchical information
The activity of the lock is determined and the determined activity
If there is a high level of
Increase the quantization step width when quantizing the above hierarchical information.
If the activity is low,
Decrease the quantization step width and reduce the quantization step width.
Using each of the pixels included in the predetermined hierarchical block
A plurality of corresponding hierarchical information of the lower hierarchy
Quantize the lower layer block consisting of pixels to be quantized
Hierarchical coding data generated by calculating the quantized value by
An image processing method for decoding data, When decoding the quantized value of the lower layer block
The quantization step width to be used is set to the floor of the predetermined hierarchy.
Quantization step width determined from distribution of quantized value of layer information
Decision step, Quantization recovery for the quantized value of the lower block
Signal is the above-mentioned quantum used when decoding the quantized value.
As the width of the conversion step increases,
Quantized decoded value decision step to decide Comprises Special
Image processingMethod.