JP3344596B2 - 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. 11 and 12) Problems to be Solved by the Invention Means for Solving the Problems (FIGS. 4, 7 and 8) Operation (FIGS. 4, 7 and 8) Embodiment (1) Principle of Hierarchical Coding (FIGS. 1 to 3) (2) Image Coding Device of Embodiment (FIGS. 4 to 6) (3) Selection of Quantization Step Width (FIG. 7) (4) Operation of Embodiment (FIG. 8) (5) Effects of Embodiment (6) Other Embodiments (FIGS. 9 and 10) 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 method suitable for application to an image coding apparatus for dividing predetermined image data into a plurality of image data having different resolutions for coding. Things.

[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 lower resolution than the first hierarchical data, third hierarchical data having lower resolution than the second resolution data, and so on. The 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. Thus, by decoding only the desired hierarchical data from the hierarchical data of a plurality of layers, desired image data can be obtained with a necessary minimum transmission data amount.

[0005] Here, as shown in FIG. 11, in the image coding apparatus 1 that realizes, for example, four-layer coding as the layer coding, the thinning filters 2, 3, and 3 for three stages are respectively provided.
4 and interpolation filters 5, 6, and 7. The reduced image data D2, D3, and D4 having lower resolution are sequentially formed by the thinning filters 2, 3, and 4 for each stage of the input image data D1, and the interpolation filters are formed. The reduced image data D2, D3, and D4 are returned to the resolutions before the reduction according to 5, 6, and 7.

The outputs D2 to D4 of the respective thinning filters 2 to 4
The outputs D5 to D7 of the interpolation filters 5 to 7 are input to difference circuits 8, 9, and 10, respectively, whereby difference data D8, D9, and D10 are generated. 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 reduced image data D4 each have an area of 1,
The size is 1/4, 1/16, 1/64.

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.

[0008] 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 encoding apparatus for realizing such a hierarchical encoding method, input image data is divided into a plurality of hierarchical data and encoded. However, there is a problem in that the compression efficiency is reduced as compared with a high-efficiency coding method that does not use hierarchical coding. Further, when an attempt is made to improve the compression efficiency, there is a problem that the image quality deteriorates due to the quantizer applied between the respective hierarchical data.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to propose an image coding apparatus capable of improving compression efficiency and reducing image quality deterioration when hierarchically coding image data. It is.

[0012]

In order to solve this problem, the present invention comprises a plurality of pieces of hierarchical information D31 to D35 from the lowest hierarchical information D35 having the lowest resolution to the lowest hierarchical information D31 having the highest resolution. An image processing apparatus 40 for processing image data, means 49 to 57 for determining the activity of hierarchical information of a predetermined hierarchy, and, when the activity is high, quantizing hierarchical information of a hierarchy lower than the predetermined hierarchy. Means 51 to 57 for making the quantization characteristics rough at the time, and when the activity is low, making the quantization characteristics at the time of quantizing the layer information of a layer lower than the predetermined layer not coarse.

In the present invention, the image processing apparatus 40 for processing image data composed of a plurality of pieces of hierarchical information D31 to D35 from the highest hierarchical information D35 having the lowest resolution to the lowest hierarchical information D31 having the highest resolution. Hot,
Activity determining means 55 to 49 for determining the activity of each block composed of a plurality of pixels with respect to the hierarchy information D32 to D35 of a predetermined hierarchy, and a hierarchy lower than the predetermined hierarchy when the activity is high. The quantization characteristics at the time of quantizing the information D31 to D34 are rough, and when the activity is low, the quantization characteristics at the time of quantizing the hierarchy information D31 to D34 of a layer lower than the predetermined layer are not coarse. Decision means 5 to be assumed
7 to 51, and quantization means 57 to 51 for quantizing corresponding blocks in lower layers based on the quantization characteristics.

Further, in the present invention, the quantization characteristic is a quantization step width.

Further, according to the present invention, there is provided an image processing apparatus 40 for processing image data comprising a plurality of pieces of hierarchical information from the highest hierarchical information D35 having the lowest resolution to the lowest hierarchical information D31 having the highest resolution. Activity determining means 55 to 49 for determining the activity of each block composed of a plurality of pixels with respect to the hierarchical information D32 to D35 of the predetermined hierarchy, and, when the activity is high, the hierarchical information of the hierarchy lower than the predetermined hierarchy. D31
When the activity is low, the quantization step width at the time of quantizing the layer information D31 to D34 of a layer lower than the predetermined layer is narrow. Determination means 57 to
51, and quantization means 57 to 51 for quantizing the corresponding block of the lower hierarchy based on the quantization step width.

Further, in the present invention, the activity judging means 49 to 57 judge the activity so as to reflect the distribution of the quantized values of a plurality of pixels of each block of the hierarchy information of the predetermined hierarchy.

Further, in the present invention, the determining means 49
When the activity is high, the hierarchy information D31 to D34 of the lower hierarchy than the predetermined hierarchy is quantized to the upper quantization step width when quantizing the hierarchy information D32 to D35 of the predetermined hierarchy. In the case where the quantization step width at the time of performing the quantization is large and the activity is low, the coefficient is multiplied by a coefficient such that the quantization step width at the time of quantizing the hierarchy information D31 to D34 of the hierarchy lower than the predetermined hierarchy is reduced. , The quantization step width is determined.

Further, in the present invention, the determining means 49
To 57 are multiplied by a coefficient having a weight according to the quantization value. Further, the weight is at least one of a linear weight and a non-linear weight.

[0019]

According to the present invention, the quantization characteristics for quantizing the hierarchy information D31 to D34 of the lower hierarchy than the predetermined hierarchy are determined based on the activities of the hierarchy information D32 to D35 of the predetermined hierarchy. An image processing apparatus 4 that can omit an additional code indicating the characteristics of a quantizer, improves compression efficiency when performing sub-hierarchical encoding, and reduces image quality degradation
0 can be obtained.

[0020]

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. For four pixels X1 to X4 in a small block of 2 lines × 2 pixels of the lower layer, the following equation is used.

[Mathematical formula-see original document] m = (X1 + X2 + X3 + X4) / 4 An arithmetic average represented by the following equation (1) is obtained, and the value m is set as the value of the upper hierarchy. In this lower hierarchy,

ＸXi = Xi−m (where i = 1 to 3) As shown by (2), by preparing three pixels of difference values from the upper layer, the same as the original four-pixel data A hierarchical structure is constructed by the amount of information.

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

[Equation 3] E [Xi] = ΔXi + m (where i = 1 to 3) As represented by (3), each 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 4] E [X4] = m × 4-E [X1] -E [X2] -E [X3]... As shown by (4), three decodings of the lower layer from the average value m of the upper layer The decoded value E [X4] is determined by subtracting the value. Here, E [] means a decoded value.

In this hierarchical coding, the resolution is quadrupled from the upper layer to the lower layer for each layer, but the redundancy is reduced by inhibiting this division in the flat part. 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
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. The reduction efficiency varies depending on the image, but when 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.
In this case, the signal level width can be effectively reduced by encoding the difference data from the upper layer data in the lower layer. FIG. 3 shows the case of five layers by the layer coding described above with reference to FIG. 2. Here, the layers are named as the first to fifth layers counting from the lower layer.

Compared to the 8-bit PCM data of the original image,
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 a 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 represented 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) is reduced 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 Coding Apparatus of Embodiment In FIG. 4, reference numeral 40 denotes an image coding 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 ( 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 fourth hierarchical 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
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 1/1.
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 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 The upper-layer data M and the lower-layer pixels a, b, and c 4 pixels can be left as they are. That is, using M, a, b, c, and d, the following equation:

D = 4 × M− (a + b + c) (5) The decoder can easily restore the non-transferred pixel d on the decoder side.

FIG. 6 shows a schematic diagram of the relationship between the hierarchies for an example of four hierarchies. Here, each hierarchical data is
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 apparatus 40, the fifth hierarchical data D55 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 obtain 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 coding apparatus 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 apparatus 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.

(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. 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, or the n-th sum of the hierarchy data D35 and the difference data D41 to D44.

In the case of the embodiment, a 2-bit quantizer is used as a quantizer, and the difference value is +12 in this quantizer.
FIG. 7 shows the quantization characteristics when 2-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 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, any of the quantization values 0 to 3 shown in FIG. 7 is generated. Here, since the distribution of the quantization 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 distribution of the quantization values 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 encoders 51, 53, 5
It is possible to improve the compression efficiency according to the fifth and fifth aspects and to prevent the image quality from deteriorating during the compression encoding process.

Next, the rule for determining the quantization step width in the embodiment will be described. First, each of the quantized values 0 to 3 is classified into sections A and B as shown in FIG. That is, when the quantized value is 1 or 2, this is set as a section A, and when the quantized value is 0 or 3, this is set as a 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 quantization 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, the quantization step width of the upper layer is p
0, assuming that the quantization step width of the lower hierarchy is p1, Rule 1) When all the quantization values of four pixels belong to the section B,
p1 = 2 × p0 Rule 2) When the quantized values of the 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,
The quantization step width p1 of the lower hierarchy is determined based on p1 = p0 / 2. 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.

Rule 2) can be considered in many cases as the state of activity in a block. However, since it is generally considered that the absolute value of the data in section B is not large due to spatial correlation, quantization of the upper layer is performed. It fulfills the function of maintaining the step width. 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 layer is reduced, and the function of suppressing the image quality deterioration in a flat portion is achieved.

As described above, in the image encoding device 40, the quantization step width of the lower hierarchy is determined according to the activity in the block of the upper hierarchy.

(4) 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 device 40 enters n-1 to the layer counter I assuming n layers in step SP2 from step SP1.

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 of the quantization step width, which is the attribute of the highest layer. In the following step SP5, the image encoding device 40 performs the encoding and decoding of the highest hierarchical data D35. Incidentally, at this time, the image coding apparatus 40 does not quantize the uppermost layer data D35 with the initial value of the quantization step width initialized in step SP4, but sets the initial value of the quantization step width in the lower layer. This is set as an initial value for determining the quantization step width.

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 inter-layer difference data D44, D43, D42 or D41 generated at this time is determined in the upper layer by the quantum. Quantization is performed according to the quantization step width. Next, in step SP7, the image coding apparatus 40 makes a determination according to the above-described rules 1) to 3) based on the distribution of the quantized values in the block, and in a succeeding step SP8, based on the determination result. The quantization step width of the lower layer 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 an affirmative result is obtained here, this means that the processing of all the layers has been completed. At this time, the image coding apparatus 40 proceeds 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.

(5) Effects of the Embodiment According to the above configuration, the quantization step width p1 of the lower layer is determined based on the quantization value distribution when quantizing with the quantization step width of the upper layer. As a result, the additional code indicating the characteristics of the quantizer can be omitted, and the image encoding device 40 with improved compression efficiency and reduced image quality can be realized.

(6) Other Embodiments In the above-described embodiment, the quantization step width p0 of the upper layer is multiplied by 2, 1 or 1/2 based on rules 1) to 3), respectively. In the above, the case where the quantization step width p1 of the lower layer is determined has been described. However, the present invention is not limited to this, and the quantization step width p0 of the upper layer is determined according to the quantization value as shown in FIG. Linear weight w1
May be multiplied, and various types of weighting can be applied to the weighting of the quantization step width of the upper layer.

For example, the quantization step width p0 of the upper layer
May be multiplied by a non-linear weight to determine the quantization step width p1 of the lower hierarchy. In this case, the non-linear weighting rule for the quantized value is such that the upper layer quantization step width is p0, the lower layer quantization step width is p1, and the non-linear weights are w2 (p0) and w3 (p0). Then, for example, the following rule may be used. Rule 1) When all the quantized values of four pixels belong to section B in FIG. 7, p1 = w2 (p0) × p0 Rule 2) When the quantized values of four pixels belong to section A and section B in FIG. p1 = p0 Rule 3) If all the quantized values of the four pixels belong to the section B in FIG. 7, p1 = w3 (p0) .times.p0

Here, as shown in FIG. 10, the characteristics of the nonlinear weights w2 (p0) and w3 (p0) are such that the weights converge to 1 as the value of the upper hierarchical quantization step width p0 increases. This makes it possible to stabilize the quantization characteristics in processing over a plurality of hierarchies.

Also, when the quantization step width of the upper layer is multiplied by the linear weight, the characteristic of the linear weight is changed to the upper layer quantization step width p0 similarly to the case of the nonlinear weight.
If the weight w1 (p0) converges to 1 as the value of becomes larger, the quantization characteristics in the processing over a plurality of layers can be stabilized.

Furthermore, as a method of obtaining the quantization step width of the lower layer based on the quantization step width of the upper layer, in addition to multiplying the weight, the output of the function f with respect to the quantization step width p0 of the upper layer is used. May be directly generated. In this case, the quantization step width p1 of the lower layer is p1 = f (p
(Quantized value of 0, 4 pixels).

[0061]

As described above, according to the present invention, the quantization characteristic for quantizing the hierarchical information lower than the predetermined layer is determined based on the activity of the layer information of the predetermined layer. As a result, it is possible to omit the additional code indicating the quantization characteristic, and to obtain an image processing apparatus and method capable of improving the compression efficiency at the time of the divisional hierarchical coding and reducing the image quality deterioration.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining hierarchical data generated by an image encoding device according to an image processing method of 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 image encoding device according to the image processing method of 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 schematic diagram illustrating characteristics of a quantizer according to the embodiment.

FIG. 8 is a flowchart for explaining the operation of hierarchical encoding.

FIG. 9 is a characteristic curve diagram showing characteristics of linear weights according to another embodiment.

FIG. 10 is a characteristic curve diagram showing characteristics of non-linear weights according to another embodiment.

FIG. 11 is a block diagram showing a conventional image encoding device.

FIG. 12 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 decoding data.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N ^7/ 24-7/68 H04N 1/41-1/419

Claims (11)

(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  Activity of hierarchy information of a given hierarchyMeans to seek
When, If the activity is high,
The quantization characteristics when quantizing the layer information of the lower layer are coarse.
If the activity is low,
Amount when quantizing layer information of layers lower than the specified layer
Means to reduce the fertility characteristics With Specially
An image processing device. 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  For each layer information of a predetermined layer,
Activity to determine the activity of the block
Bitness determination means,If the activity is high,
The quantization characteristics when quantizing the layer information of the lower layer are coarse.
If the activity is low,
Amount when quantizing layer information of layers lower than the specified layer
Means for determining that the denaturation characteristics are not coarse;  Based on the quantization characteristics, a corresponding one of the lower layers
And a quantizing means for quantizing the block.
Image processing apparatus. 3. A pre-Symbol quantization characteristic image processing apparatus according to claim 1 or 2, characterized in that the quantization step width. (4)Resolution from the highest hierarchical information with the lowest resolution
From multiple layers of information up to the lowest level information
An image processing apparatus for processing image data For each layer information of a predetermined layer,
An activity that determines the activity of the block
Tay determination means, If the activity is high,
Quantization step when quantizing layer information of lower layers
If the width is large and the activity is low,
Quantizes layer information of a layer lower than the predetermined layer.
Means for narrowing the quantization step width when performing Correspondence of the lower layer based on the quantization step width
Quantization means for quantizing the block To have
Characteristic image processing device. Wherein said Akuteibitei determining means according to claim, characterized in that determining the Akuteibitei to reflect the distribution of quantized values of a plurality of pixels of each block of the hierarchical information of said predetermined hierarchical 1,2 Or the image processing device according to 4 . 6. The hierarchical information of the predetermined hierarchy
In the upper quantization step width when quantizing the
If the activity is high, floors lower than the predetermined level
Large quantization step width when quantizing layer information
And when the activity is low, the predetermined
Quantization when quantizing layer information of layers lower than the layer
The quantum is multiplied by a coefficient that reduces the step width.
4. The method according to claim 3, wherein the step width is determined.
5. The image processing device according to 4. 7. The method according to claim 1, wherein the determining means determines a weight according to the quantization value.
Multiplying by the coefficient having a weight
Item 7. The image processing device according to Item 6. 8. The method according to claim 1, wherein the weighting is a linear weight or a nonlinear weight.
Claims characterized by at least one of:
8. The image processing device according to 7. 9.Resolution from the highest hierarchical information with the lowest resolution
From multiple layers of information up to the lowest level information
An image processing method for processing image data Determine the activity of the hierarchy information of the predetermined hierarchy, If the activity is high,
The quantization characteristics when quantizing the layer information of the lower layer are coarse.
If the activity is low,
Amount when quantizing layer information of layers lower than the specified layer
Make the child characteristics not coarse Image processing characterized by the following:
Method. 10.Solve from the highest hierarchical information with the lowest resolution
Multiple hierarchical information up to the lowest hierarchical information with the highest resolution
An image processing method for processing image data comprising For each layer information of a predetermined layer,
For blocks, determine the activity, If the activity is high,
The quantization characteristics when quantizing the layer information of the lower layer are coarse.
If the activity is low,
Amount when quantizing layer information of layers lower than the specified layer
Not to coarsen the fertility characteristics, Based on the quantization characteristics, a corresponding one of the lower layers
Quantize blocks An image processing method comprising: 11. Solve from the highest hierarchical information with the lowest resolution
Multiple hierarchical information up to the lowest hierarchical information with the highest resolution
An image processing apparatus for processing image data comprising For each layer information of a predetermined layer,
Determines the activity of the block, If the activity is high,
Quantization step when quantizing layer information of lower layers
If the width is large and the activity is low,
Quantizes layer information of a layer lower than the predetermined layer.
The quantization step width at the time of Correspondence of the lower hierarchy based on the quantization step width
Quantize blocks Image processing method characterized by the following:
Law.