JPH0795568A - Method and device for coding picture - Google Patents

Abstract

PURPOSE:To improve the compression efficiency and to reduce the deterioration in the picture quality when picture data are coded hierarchically by dividing a block adaptively corresponding to the property of picture data and sending the hierarchical coding data obtained by the result of division. CONSTITUTION:Input picture data D31 comprising a still picture are divided into five layers through hierarchical coding and lowermost layer data and four inter-layer differential data D40-D43 obtained as the result are coded. First - 4th layer data except 5th layer data D35 of a highest layer among the five layer data D31-D35 are given to 1st-4th differential circuits 41, 43, 45, 47, in which they are subjected to differential calculation respectively and the result of arithmetic operation is generated as inter-layer differential data D40-D43. Then number of picture elements as a coding object is not increased by generating the lower layer data relating to the higher layer data and even when the picture data are coded while being decomposed into plural layers, the reduction in the compression efficiency is avoided.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Fields of Industrial Application Conventional Technology (FIGS. 7 and 8) Problems to be Solved by the Invention (FIGS. 7 and 8) Means for Solving the Problems (FIGS. 1 to 6) Operation (FIGS. 1 to 6) ) Embodiments (Figs. 1 to 6) (1) Principle of hierarchical coding (Figs. 1 to 3) (2) Image coding device of embodiments (Figs. 4 to 6) (3) Other embodiments Invention Effect of

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding method and an image coding apparatus, and can be applied to, for example, an image coding apparatus which divides predetermined image data into a plurality of image data having different resolutions and codes the image data. .

[0003]

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

Here, as shown in FIG. 7, in the image coding apparatus 1 which realizes, for example, four-layer coding as the hierarchical coding, thinning filters 2, 3, 4 for three stages are respectively provided.
And the interpolation filters 5, 6, and 7, and the input image data D
With respect to No. 1, the reduced image data D2, D3, D4 having a lower resolution are sequentially formed by the thinning filters 2, 3, 4 of each stage, and the reduced image data D2, D3, D4 are reduced by the interpolation filters 5, 6, 7 before reduction. Return to the resolution of.

Outputs D2 to D4 of the thinning filters 2 to 4
And the outputs D5 to D7 of the respective interpolation filters 5 to 7 are input to the 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, this difference data D8
-D10 and reduced image data D4 are input image data D
For example, the area is 1, 1/4, 1/16, 1 /
It has been selected to be 64 times the size.

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 filter 4 are encoders 11, 12, 13, 14 respectively.
And the compression processing is performed. As a result, the encoders 11, 12, 13, 14 which have different resolutions
Second, third and fourth hierarchical data D11, D12, D1
3 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 apparatus shown in FIG. That is, the first to fourth hierarchical data D11 to D14 are respectively decrypted by the decoders 21, 22, 23,
The data is decoded by 24, and as a result, the decoder 24 first outputs the fourth hierarchical data D24.

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, so that the first hierarchical data D21 is restored.

[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 to be coded, the data amount of only the hierarchical component is inevitable. However, there is a problem that the compression efficiency is reduced as compared with the high efficiency coding method that does not use the hierarchical coding. Further, when trying to improve the compression efficiency, there is a problem that the image quality is deteriorated by the quantizer applied between the respective hierarchical data.

The present invention has been made in consideration of the above points, and provides an image coding method and an image coding apparatus capable of improving compression efficiency and reducing image quality degradation when hierarchically coding image data. It is a proposal.

[0012]

In order to solve such a problem, the present invention provides an image coding method for hierarchically coding image data by using a recursive hierarchical representation.
An adaptive block division corresponding to the property of the image data is executed, and the hierarchical encoded data obtained by the division result is transmitted.

Further, according to the present invention, in an image coding method of sequentially recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and coding the hierarchical data, the hierarchical data except the highest hierarchical data having the lowest resolution is hierarchized. The block activity is determined for a predetermined block of data, and when the block activity is less than a predetermined threshold value, a split stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. The block activity determination and the transmission of a plurality of lower blocks are stopped, and the determination flag for each block is transmitted together with the encoded code.

Further, in the present invention, the image data D31
Is recursively divided into a plurality of hierarchical data D31 to D35 having different resolutions, and the highest hierarchical data D35 having the lowest resolution, each hierarchical data D31 to D34 excluding the highest hierarchical data D35, and adjacent upper data. In the image coding method for coding the inter-layer difference data D40 to D43 for a plurality of layers, which are the difference values of the layer data D32 to D35, the inter-layer difference data D of each layer except the highest layer.
The block activity A is determined for the predetermined blocks 40 to D43, and when the block activity A is less than the predetermined threshold Tha, the determination flags F of a plurality of lower blocks corresponding to the blocks in the inter-layer difference data D40 to D42 of the adjacent lower layers. As a result, the division stop flag is set, the block activity determination of a plurality of lower blocks and the transmission of a plurality of lower blocks are stopped, and the determination flag F for each block is transmitted together with the encoded code.

Further, according to the present invention, in the image coding method of sequentially recursively dividing the image data into a plurality of hierarchical data having a plurality of different resolutions and coding the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is judged for a specified block in the data, and when the block activity is less than the specified threshold value, the split stop flag is temporarily set as a judgment flag for a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. When the block activity of one of the blocks is equal to or more than a predetermined threshold value, the division stop flag is changed to the division continuation flag, and the determination flag for each block is transmitted together with the encoded code.

Further, in the present invention, the image data is recursively divided into a plurality of hierarchical data having different resolutions, and the highest hierarchical data having the lowest resolution and each hierarchical data excluding the highest hierarchical data. And an image encoding method for encoding the inter-layer difference data for a plurality of layers, which is the difference value of the adjacent upper layer data, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the highest layer. , If the block activity is less than a predetermined threshold value, a split stop flag is set once as a determination flag of a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block activity of one of the plurality of lower blocks is predetermined. If the threshold is greater than or equal to the threshold of Flag was set to be transmitted together with the encoded code.

Further, according to the present invention, in an image coding apparatus which represents image data using a recursive hierarchical representation and performs hierarchical coding, adaptive block division corresponding to the property of the image data is executed to perform coding. The encoding means for encoding and the transmitting means for transmitting the hierarchical encoded data obtained by the division result are provided.

Further, according to the present invention, in an image coding apparatus for sequentially recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and coding the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is determined for a predetermined block of data, and when the block activity is less than a predetermined threshold value, a split stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. The block activity determination and the transmission of a plurality of lower blocks are stopped, and the division control means for transmitting the determination flag for each block together with the encoding code is provided.

Further, in the present invention, the image data D31
Is recursively divided into a plurality of hierarchical data D31 to D35 having different resolutions, and the highest hierarchical data D35 having the lowest resolution, each hierarchical data D31 to D34 excluding the highest hierarchical data D35, and adjacent upper data. The image encoding device 4 that encodes the inter-layer difference data D40 to D43 for a plurality of layers that is the difference value of the layer data D32 to D35.
At 0, the block activity A is determined for a predetermined block of the inter-layer difference data D40 to D43 of each layer except the top layer, and when the block activity A is less than the predetermined threshold Tha, the inter-layer difference data D40 of the adjacent lower layer. In D42, the division stop flag is set as the determination flag F of the plurality of lower blocks corresponding to the blocks, the block activity determination of the plurality of lower blocks and the transmission of the plurality of lower blocks are stopped, and the determination flag F of each block. The division control means 50, 51, 52, 53 for transmitting the code together with the encoded code are provided.

Further, according to the present invention, in an image coding apparatus which recursively divides image data into a plurality of hierarchical data having a plurality of different resolutions and encodes the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is judged for a specified block in the data, and when the block activity is less than the specified threshold value, the split stop flag is temporarily set as a judgment flag for a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. When the block activity of one of the blocks is equal to or more than a predetermined threshold value, the division stop flag is changed to the division continuation flag, and the division control means for transmitting the determination flag for each block together with the encoding code is provided.

Further, in the present invention, the image data is recursively divided into a plurality of hierarchical data having different resolutions, and the highest hierarchical data having the lowest resolution and each hierarchical data excluding the highest hierarchical data. And an image encoding device for encoding inter-layer difference data for a plurality of hierarchies consisting of difference values of adjacent upper layer data, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the highest layer. , If the block activity is less than a predetermined threshold value, a split stop flag is set once as a determination flag of a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block activity of one of the plurality of lower blocks is predetermined. If the threshold is greater than or equal to the threshold of Flag was set to provide a division control means for transmitting with the encoded code.

[0022]

When the image data is expressed using the recursive hierarchical representation and hierarchically encoded, the adaptive block division corresponding to the property of the image data is executed and encoded, and the division result is obtained. It is possible to reduce the amount of information such as a flat portion of an image by adaptively dividing the blocks of the lower layer by transmitting the hierarchically encoded data that is generated.

Further, the block activity is determined for a predetermined block of hierarchical data excluding the highest hierarchical data having the lowest resolution, and when the block activity is less than a predetermined threshold value, a plurality of lower blocks corresponding to the block in adjacent lower hierarchical data are detected. By setting the split stop flag as the judgment flag, stopping the block activity judgment of a plurality of lower blocks and transmission of a plurality of lower blocks, and transmitting the judgment flag for each block together with the coding code It is possible to prevent unnecessary block encoded data from being transmitted according to the block activity of the data, reduce the code amount, and improve the compression efficiency of the encoded data.

Further, the block activity A is determined for a predetermined block of the inter-layer difference data D31 to D34 of each layer except the highest layer D35, and when the block activity A is less than a predetermined threshold Tha, the difference between the adjacent lower layers. A division stop flag is set as the determination flag F of a plurality of lower blocks corresponding to the blocks in the data D40 to D42, the block activity determination of the plurality of lower blocks and the transmission of the plurality of lower blocks are stopped, and the determination of each block is performed. By transmitting the flag F together with the encoded code, the inter-layer difference data D4
According to the block activity A of 0 to D43, unnecessary block encoded data can be prevented from being transmitted, the code amount can be reduced, and the compression efficiency of the encoded data can be improved.

Further, when the image data is sequentially recursively divided into a plurality of hierarchical data having a plurality of different resolutions and encoded, a block activity is determined for a predetermined block in the hierarchical data except the highest hierarchical data having the lowest resolution. If the block activity is less than the predetermined threshold value, the split stop flag is set once as the determination flag of the lower blocks corresponding to the block in the adjacent lower layer data, and the block of one of the lower blocks is blocked. When the activity is equal to or higher than a predetermined threshold, the split stop flag is changed to the split continuation flag, and the determination flag for each block is transmitted together with the coding code, so that the image quality is degraded according to the block activity of the hierarchical data. It is necessary to prevent the block and judge the necessity of the block, and to remove unnecessary coding data. Resulting to not transmit the data, can improve the compression efficiency of the coded data to reduce the amount of codes. .

The image data is sequentially recursively divided into a plurality of hierarchical data having a plurality of different resolutions, and the highest hierarchical data having the lowest resolution, each hierarchical data excluding the highest hierarchical data, and adjacent upper hierarchical data. When encoding the inter-layer difference data for multiple hierarchies consisting of the difference value of, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the top layer, and the block activity is less than the predetermined threshold value. In this case, the split stop flag is set once as the judgment flag of multiple lower blocks corresponding to the block in the adjacent lower layer data, and if the block activity of one of the multiple lower blocks is greater than or equal to the specified threshold, the split is stopped. Change the flag to the division continuation flag and transmit the judgment flag for each block together with the coded code. By doing so, it is possible to prevent the deterioration of the image quality according to the block activity of the inter-layer difference data, judge the necessity of the block, and prevent unnecessary encoded data from being transmitted, thereby reducing the code amount. The compression efficiency of encoded data can be improved.

[0027]

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 Layered Coding FIG. 1 shows, as a whole, the principle of layered coding according to the present invention in which a still image such as a high definition television signal is layered 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.
Further, regarding decoding of upper layer data to lower layer data, the amount of information in the flat portion is reduced by adaptively controlling division based on the activity of each block. Furthermore, in the encoding of the inter-layer difference data performed for the lower layer data, the efficiency is realized by switching the quantization characteristic for each block without additional code based on the activity of the upper layer data.

That is, in the hierarchical structure of this hierarchical encoding,
First, the high-definition television signal to be input is used as the lowest layer data, and the 4 pixels X _{1 to} X _{4 in} the small block of 2 lines × 2 pixels of this lowest layer data 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 data. In this lower layer data,

[Equation 2] As shown in, the inter-layer difference data with respect to the upper layer data 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 data, the three pixels X _{1 to} X ₃ are

[Equation 3] As shown in, the decoded value E [X _i ] is obtained by adding the inter-layer difference data ΔX _i to the average value m of the upper layer data, and the remaining 1 pixel is

[Equation 4] As shown by, the decoded value E [X ₄ ] is determined by subtracting the three decoded values of the lower layer data from the average value m of the upper layer data. E [] means a decoded value.

Here, in this hierarchical encoding, the resolution is quadrupled from upper layer to lower layer, but in the flat part, 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 judged as a local activity, for example, the maximum value of the inter-layer difference data.

As an example of this hierarchical encoding, an ITE HD standard image (Y signal) is used, and the adaptive division result when divided into five layers and encoded is shown in FIG. In the figure, the ratio of the number of pixels in each layer to the original number of pixels when the threshold value for the maximum inter-layer difference data is changed is shown, but it can be seen that the redundancy is reduced based on the spatial correlation. The reduction efficiency changes depending on the image, but if the threshold for the maximum inter-tier difference data is changed from 1 to 6, the average reduction rate is 28 to 69 [%].
become.

In practice, the resolution of the upper layer data is quadrupled to form lower layer data, at which time the difference data between layers from the upper layer data is encoded in the lower layer data to effectively reduce the signal level width. it can. FIG. 3 shows the case of five layers by the layer coding described above with reference to FIG. 2, but here, the layers are numbered from the lower layers to the first to fifth layers. It can be seen that the signal level width is reduced as compared with the 8-bit PCM data of the original image. In particular, since the first to fourth layers having a large number of pixels are difference data between layers, a significant reduction can be achieved and efficiency is improved by subsequent quantization. As can be seen from the table in Fig. 3, the reduction efficiency has little dependence on the pattern,
Valid for all pictures.

Further, by making the upper layer data by the average value of the lower layer data, the lower layer data is converted into the difference from the average value of the upper layer data while keeping the error propagation within the block, thereby improving the efficiency. Can also be held together. Actually, in the upper layer coding, there is a correlation in the activity between layers at the same spatial position, and by determining the quantization characteristic of the lower layer data from the quantization result of the upper layer data, adaptation without additional code is required. A quantizer can be realized.

Practically, an image is hierarchically encoded based on the above-mentioned five-stage hierarchical structure and expressed at a plurality of resolutions, and adaptive division and adaptive quantization using the hierarchical structure are performed.
About 1 HD standard image (8 bits Y / P _B / P _R )
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 of Embodiment In FIG. 4, reference numeral 40 generally indicates an image encoding device according to the present invention. For example, input image data D31 which is a still image such as a high-definition television signal is described above. As the layer coding, the data is divided into five layers, and the lowest layer data obtained as a result and the inter-layer difference data for four layers are encoded. In fact, in the image encoding device 40, the input image data D31 is input to the first difference circuit 41 and the first averaging circuit 42.

As shown in FIG. 5, the first averaging circuit 42 starts from the four pixels X1 (1) to X4 (1) of the input image data D31, which is the first layer data as the lowest layer, to the second pixel. The pixel X1 (2) of the hierarchical data D32 is generated. Similarly, the pixels X2 (2) to X4 (2) adjacent to the pixel X1 (2) of the second hierarchical data D32 also have the first hierarchical data D3.
It is generated by averaging 4 pixels of 1. The second layer data D32 is the second difference circuit 43 and the second averaging circuit 44.
Entered in. The second averaging circuit 44 generates the pixel X1 (3) of the third hierarchical data D33 by averaging the four pixels of the pixels X1 (2) to X4 (2) of the second hierarchical data D32, for example. Pixel X1 (3) of this third layer data D33
Similarly, the pixels X2 (3) to X4 (3) adjacent to are also generated by averaging four pixels of the second hierarchical data D32.

Further, the third hierarchical data D33 is input to the third difference circuit 45 and the third averaging circuit 46. Third
The averaging circuit 46 of the third hierarchical data D3 is also similar to the above.
From the four-pixel average of the three pixels X1 (3) to X4 (3),
The pixels X1 (4) to X4 (4) of the fourth layer data D34 are generated. The fourth layer data D34 is input to the fourth difference circuit 47 and the fourth averaging circuit 48. Similarly to the above, the fourth averaging circuit 48 also generates the fifth layer data D35, which is the highest layer, by averaging the four pixels of the pixels X1 (4) to X4 (4) of the fourth layer data D34.

In practice, the first to fifth hierarchical data D31 to
The block size of D35 is the second when the block size of the first layer data D31 which is the lowest layer is 1 × 1.
Hierarchical data D32 is 1/2 × 1/2, third hierarchical data D33
Is 1/4 × 1/4, the fourth layer data D34 is 1/8 × 1/8, and the fifth layer data D35, which is the highest layer data, is 1/16 × 1 /
16

In this way, the five hierarchical data D31 ...
The first to fourth layer data other than the fifth layer data D35 of the highest layer of D35 are the first, second, third, and fourth difference circuits 41, 4 as described above regarding the equation (2).
Difference calculation is performed at 3, 45, and 47, and the calculation result is generated as inter-layer difference data D40, D41, D42, and D43.

In practice, first, the fourth difference circuit 47 calculates the difference between the fifth layer data D35 and the fourth layer data 34 to generate the fourth layer inter-layer difference data D43, and then the fourth layer data D43. The difference circuit 45 of No. 3 performs a difference operation between the fourth layer data D34 and the third layer data D33 to generate inter-layer difference data D42 of the third layer.
Further, next, the second difference circuit 43 performs a difference operation on the third layer data D33 and the second layer data D32 to generate inter-layer difference data D41 of the second layer, and finally in the first difference circuit 41. Second layer data D32 and first
The difference calculation is performed on the layer data D31 to generate the first layer difference data D40 between layers.

As described above, the image coding apparatus 4 of this embodiment
0, the fifth layer data D35, the fourth layer to the first layer
Inter-layer difference data D43 to D40 of layers are sequentially generated in this order. At this time, in the image encoding device 40,
As described above with respect to the equation (2), by generating the lower layer data in association with the upper layer data,
The number of pixels to be encoded is not increased so that the reduction of compression efficiency can be avoided even when the image data is decomposed into a plurality of layers and encoded.

These inter-tier difference data D40 to D43
Are input to the division control circuits 50, 51, 52 and 53, respectively. The division control circuits 50 to 53 sequentially determine from the inter-layer difference data D43 to D40 of the upper layer, the determination with the block activity threshold Tha indicating whether or not a predetermined block in the inter-layer difference data D40 to D43 is a flat portion. Then, it is determined whether or not to transmit the following inter-layer difference data D42 to D40. For example, when the activity in the block of the difference data D43 between layers of the fourth layer is A,

[Equation 5] If the condition is satisfied, it is determined that the image data is a flat portion and is not likely to deteriorate, and a determination flag F indicating that the image data is not transmitted is set.

At the same time, the division control circuit 53 sends a control signal C3 to the division control circuit 52 of the third hierarchy. As a result, the division control circuit 52 of the third layer is provided with the inter-layer difference data D4.
Unconditionally abort the transmission of 2. The division control circuits 52 of the third and second layers are controlled by a control signal C indicating an unconditional suspension of transmission.
When 3 and C2 are received, they are sent as they are to the lower division control circuits 51 and 50 as control signals C2 and C1. As a result, under the control of the division control circuits 53 to 50, the inter-layer difference data D42 to D4 of all lower layers.
The transmission of 0 is unconditionally aborted.

In this way, the division control circuits 50 to 53 are provided.
Difference data D40 to D4 of each layer sent from
3 is sent to the encoders 54 to 57. Further, the fifth layer data D35 of the highest layer is sent to the encoder 58 as it is. The encoders 54 to 57 use the non-linear encoding method suitable for encoding the difference data to obtain the inter-layer difference data D4.
0 to D43 are compression-encoded to generate first to fourth hierarchical compression-encoded data D45 to D48. Further, the encoder 58 uses the linear encoding method suitable for encoding the image data composed of the average value data to obtain the fifth layer data D35.
Is compression-encoded to generate fifth-layer compression-encoded data D49.

The determination flag F sent from each of the division control circuits 50 to 53 is input to the control code generation circuit 59. As a result, the control code generation circuit 59 causes the control code D including the determination flag F for each layer and each block.
Generate 50. This control code D50 is the first to fifth
The hierarchical compression coded data D45 to D49 are coded by run-length coding or the like and transmitted as a coded code.

The first to fifth information transmitted in this manner
Hierarchical compression coded data D45 to D49 and control code D5
0 is decoded by the image decoding device 60 shown in FIG. That is, the first to fifth layer compression encoded data D45 to
The D49 is input to the decoders 61 to 65 having a decoding method reverse to that of the encoders 54 to 58, respectively. As a result, the first to the fourth decoded by the decoders 61 to 64, respectively.
The inter-tier difference data D51 to D54 of the tiers are passed through the first to fourth tier division control circuits 70 to 73, respectively, to the first
~ Is input to the fourth adders 75 to 78.

The fifth layer compression coded data D49 is decoded by the decoder 65, and the resulting fifth layer data D55 is output as it is and the fourth addition circuit 7 is also provided.
8 is input. The fourth adder circuit 78 adds the fifth layer data D55 and the inter-layer difference data D54 of the fourth layer to restore the fourth layer data D59, which is output and also sent to the third adder circuit 77. .

Similarly, the third addition circuit 77 adds the restored fourth layer data D59 and the third layer difference data D53 between layers to restore the third layer data D58, and outputs it. It is sent to the second adder circuit 76. In the same manner, the second layer data D57 and the first layer data D56 are restored from the second and first addition circuits 76 and 75, and the first to fourth layer data D56 are thus restored.
~ D59 and D55 are output.

The control code D50 is input to the control code analysis circuit 66. The control code analysis circuit 66 analyzes whether or not the transmission stop of the inter-layer difference data has occurred based on the input control code D50, and sends the analysis result as the transmission stop flag F to the division control circuits 70 to 73. To do. When the division control circuits 70 to 73 detect that the transmission of the inter-layer difference data has been stopped based on the input transmission stop flag F, instead of the inter-layer difference data, for example, the value “0” is set as dummy data. Inter-layer difference data is generated and sent to the addition circuits 75 to 78.

In this way, according to the block activity of the inter-layer difference data, the image encoding device 40 does not transmit the inter-layer difference data of unnecessary blocks but only the control data indicating the transmission stop. By doing so, the image decoding device 60 can reliably restore the hierarchical data based on the control data.

According to the above configuration, the block activity is judged for a predetermined block of the inter-layer difference data of each layer except the top layer, and when the block activity is less than the predetermined threshold value, the inter-layer difference data of the adjacent lower layer. In addition to setting the split stop flag as the judgment flag of the lower order blocks corresponding to the block, the block activity judgment of the lower order blocks and the transmission of the lower order blocks are stopped, and the judgment flag of each block is coded. Since it is transmitted along with the block code, unnecessary block encoded data can be prevented from being transmitted according to the block activity of the inter-layer difference data, and the code amount can be reduced to improve the compression efficiency of the encoded data. The encoding method and the image encoding device can be realized.

(3) Other Embodiments In the above-described embodiment, the block activity is determined by the block of the inter-tier difference data, and when the block activity is less than the predetermined threshold value, the lower inter-tier difference data is used for the block. The case where the transmission is stopped by setting the division stop flag as the determination flag of the corresponding plurality of lower blocks has been described, but the present invention is not limited to this, and when the block activity is less than a predetermined threshold value, the difference between the lower layers is Set a split stop flag as a determination flag for multiple lower blocks corresponding to a block in the data, and if the block activity of one of the multiple lower blocks is greater than or equal to a predetermined threshold, set the split stop flag to the split continue flag. To change the check flag for each block to be transmitted together with the encoded code. good.

To realize this, in the image coding apparatus described above with reference to FIG. 4, the division control circuit determines the block activity for all the inter-layer difference data, and the upper division control circuit stops transmission. When the block activity is detected to be equal to or higher than the threshold value even if the control data of the above is input, the lower division control circuit sends an instruction to change the transmission stop to the transmission continuation to the upper division control circuit. If you do so, it is good.

Further, in the above-mentioned embodiment, the image data is recursively divided into a plurality of hierarchical data having a plurality of different resolutions, and the highest hierarchical data having the lowest resolution,
The case where each layer data excluding the top layer data and the inter-layer difference data for a plurality of layers formed by the difference value of the adjacent upper layer data is described, but the present invention is not limited to this, and the image data is It can also be applied to the case of sequentially recursively dividing and encoding into a plurality of hierarchical data having a plurality of different resolutions. In this case, if the block activity determination is performed on the block of the hierarchical data instead of the inter-layer difference data, the same effect as that of the above-described embodiment can be realized.

In the above embodiment, the case where the maximum value in the block and the threshold value are determined as the block activity has been described, but the present invention is not limited to this.
As the block activity, the average value in the block,
The sum of absolute values, standard deviation, sum of n powers, etc. may be judged against a threshold value, and even if the frequency of data exceeding a predetermined threshold value is used in the block, the same as in the above-mentioned embodiment. The effect can be realized.

Further, in the above embodiment, when dividing into a plurality of hierarchical data, the adjacent upper hierarchical data is recursively formed sequentially from the arithmetic mean of the image data or adjacent lower hierarchical data for each predetermined block. However, the present invention is not limited to this, and it is also possible to recursively form the adjacent upper layer data by a weighted average such that a predetermined weighting is performed and an average is taken. Can also be applied to the case where the upper hierarchy data is recursively formed.

In the above embodiment, the block activity in the block is determined, and the transmission of the data of the lower layer is stopped.
Whether or not to stop the transmission is not limited to the block activity, and other characteristics of the image data may be used,
In this way, the coding efficiency can be improved by adaptively dividing the block according to the property of the image data.

[0059]

As described above, according to the present invention, when the image data is expressed using the recursive hierarchical representation and hierarchically encoded, the adaptive block division corresponding to the property of the image data is executed. In addition to encoding, the hierarchically encoded data obtained as a result of the division is transmitted, and the block in the lower layer is adaptively divided to reduce the amount of information such as a flat portion of the image. It is possible to realize an image coding method and an image coding apparatus capable of performing the above.

The block activity is determined for a predetermined block of hierarchical data excluding the highest hierarchical data having the lowest resolution, and when the block activity is less than a predetermined threshold value, a plurality of lower blocks corresponding to the block in adjacent lower hierarchical data are determined. By setting the split stop flag as a flag, stopping the block activity determination of multiple lower blocks and transmitting multiple lower blocks, and transmitting the determination flag for each block together with the coding code, the hierarchical data It is possible to realize an image coding method and an image coding apparatus which can prevent unnecessary block coded data from being transmitted according to the block activity, and can reduce the code amount and improve the coded data compression efficiency.

The block activity is determined for a predetermined block of the inter-tier difference data of each layer other than the highest layer, and when the block activity is less than a predetermined threshold value, a plurality of blocks corresponding to the block in the inter-layer difference data of the adjacent lower layer are determined. The split stop flag is set as the determination flag of the lower block of the above, the determination of the block activity of the plurality of lower blocks and the transmission of the plurality of lower blocks are stopped, and the determination flag of each block is transmitted together with the encoding code. By doing so, it is possible to prevent unnecessary block encoded data from being transmitted according to the block activity of the inter-layer difference data, reduce the code amount, and improve the compression efficiency of the encoded data, and an image encoding method. The device can be realized.

Further, the block activity is determined for a predetermined block in the hierarchical data excluding the highest hierarchical data having the lowest resolution, and when the block activity is less than the predetermined threshold value, a plurality of lower block data corresponding to the block in the adjacent lower hierarchical data are obtained. When the block activity of one of the multiple lower blocks is greater than or equal to the predetermined threshold, the split stop flag is set as the determination flag of the above, the split stop flag is changed to the split continuation flag, and the determination flag for each block is coded. By transmitting the encoded data together with the encoded code, it is possible to prevent the deterioration of the image quality according to the block activity of the hierarchical data, judge the necessity of the block, and prevent unnecessary encoded data from being transmitted. Image coding method that can reduce the amount and improve the compression efficiency of coded data And it can realize an image coding apparatus. .

Further, the block activity is determined for a predetermined block of the inter-layer difference data of each layer other than the highest layer, and when the block activity is less than a predetermined threshold value, a plurality of lower blocks corresponding to the block in the adjacent lower layer data are detected. Once the split suspension flag is set as the determination flag, and if the block activity of any of the multiple lower blocks is greater than or equal to the predetermined threshold, the split suspension flag is changed to the split continuation flag and the determination flag for each block is encoded. By transmitting with the code, it is possible to prevent the deterioration of the image quality according to the block activity of the inter-layer difference data, judge the necessity of the block, and prevent unnecessary encoded data from being transmitted.
An image coding method and an image coding apparatus capable of reducing the code amount and improving the compression efficiency of coded data can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining hierarchical coding as a principle of an image coding method and an image coding apparatus according to the present invention.

FIG. 2 is a chart showing an adaptive division result of an HD standard image using the hierarchical encoding.

FIG. 3 is a table showing standard deviations of signal levels of respective layers of an HD standard image using the hierarchical encoding.

FIG. 4 is a block diagram showing an image coding apparatus as an embodiment of the image coding method and the image coding apparatus according to the present invention.

FIG. 5 is a schematic diagram showing a structure of hierarchical data in hierarchical encoding.

FIG. 6 is a block diagram showing an image decoding device corresponding to the image encoding device of the embodiment.

FIG. 7 is a block diagram showing an image coding apparatus using a conventional pyramid coding method.

8 is a block diagram showing an image decoding device corresponding to the image encoding device of FIG. 7. FIG.

[Explanation of symbols]

40 ... Image coding device, 41, 43, 45, 47 ...
Subtractors, 42, 44, 46, 48 ... Averaging circuit, 5
0, 51, 52, 53, 70, 71, 72, 73 ... Divided control circuit, 54, 55, 56, 57, 58 ... Encoder, 59 ... Control code generation circuit, 61, 62, 63,
64, 65 ... Decoder, 75, 76, 77, 78 ... Adder, 66 ... Control code analysis circuit.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 24, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Image coding method and image coding apparatus

[Claims]

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIGS. 8 and 9) Problem to be Solved by the Invention (FIGS. 8 and 9) Means for Solving the Problem (FIGS. 1 to 7) Action (FIGS. 1 to 7) ) Embodiments (Figs. 1 to 7) (1) Principle of hierarchical coding (Figs. 1 to 3) (2) Image coding device of embodiments (Figs. 4 to 6) (3) Other embodiments ( Figure 7) Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding method and an image coding apparatus, and can be applied to, for example, an image coding apparatus which divides predetermined image data into a plurality of image data having different resolutions and codes the image data. .

[0003]

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

Further, in the image decoding apparatus for decoding the plurality of hierarchical data, all of the plurality of hierarchical data may be decoded, and any one of the hierarchical data may be decoded depending on the resolution of the television monitor corresponding to each. One of them may be selected and decrypted. 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.

Here, as shown in FIG. 8, in the image coding apparatus 1 which realizes, for example, four-layer coding as the hierarchical coding, thinning filters 2, 3, 4 for three stages are respectively provided.
And the interpolation filters 5, 6, and 7, and the input image data D
With respect to No. 1, the reduced image data D2, D3, D4 having a lower resolution are sequentially formed by the thinning filters 2, 3, 4 of each stage, and the reduced image data D2, D3, D4 are reduced by the interpolation filters 5, 6, 7 before reduction. Return to the resolution of.

Outputs D2 to D4 of the thinning filters 2 to 4
And the outputs D5 to D7 of the respective interpolation filters 5 to 7 are input to the 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, this difference data D8
-D10 and reduced image data D4 are input image data D
For example, the area is 1, 1/4, 1/1
The size is selected to be 6, 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 filter 4 are encoders 11, 12, 13, 14 respectively.
And the compression processing is performed. As a result, the encoders 11, 12, 13, 14 which have different resolutions
Second, third and fourth hierarchical data D11, D12, D1
3 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 apparatus shown in FIG. That is, the first to fourth hierarchical data D11 to D14 are respectively decrypted by the decoders 21, 22, 23,
The data is decoded by 24, and as a result, the decoder 24 first outputs the fourth hierarchical data D24.

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, so that the first hierarchical data D21 is restored.

[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 to be coded, the data amount of only the hierarchical component is inevitable. However, there is a problem that the compression efficiency is reduced as compared with the high efficiency coding method that does not use the hierarchical coding. Further, when trying to improve the compression efficiency, there is a problem that the image quality is deteriorated by the quantizer applied between the respective hierarchical data.

The present invention has been made in consideration of the above points, and provides an image coding method and an image coding apparatus capable of improving compression efficiency and reducing image quality degradation when hierarchically coding image data. It is a proposal.

[0012]

In order to solve such a problem, the present invention provides an image coding method for hierarchically coding image data by using a recursive hierarchical representation.
An adaptive block division corresponding to the property of the image data is executed, and the hierarchical encoded data obtained by the division result is transmitted.

Further, according to the present invention, in an image coding method of sequentially recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and coding the hierarchical data, the hierarchical data except the highest hierarchical data having the lowest resolution is hierarchized. The block activity is determined for a predetermined block of data, and when the block activity is less than a predetermined threshold value, a division stop flag is set as a determination flag for a plurality of lower blocks corresponding to blocks in adjacent lower layer data, and a plurality of lower blocks are set. The block activity determination and the transmission of a plurality of lower blocks are stopped, and the determination flag for each block is transmitted together with the encoded code.

Further, in the present invention, the image data D31
Is recursively divided into a plurality of hierarchical data D31 to D35 having different resolutions, and the highest hierarchical data D35 having the lowest resolution, each hierarchical data D31 to D34 excluding the highest hierarchical data D35, and adjacent upper data. In the image coding method for coding the inter-layer difference data D40 to D43 for a plurality of layers, which are the difference values of the layer data D32 to D35, the inter-layer difference data D of each layer except the highest layer.
The block activity A is determined for the predetermined blocks 40 to D43, and when the block activity A is less than the predetermined threshold Tha, the determination flags F of a plurality of lower blocks corresponding to the blocks in the inter-layer difference data D40 to D42 of the adjacent lower layers. As a result, the division stop flag is set, the block activity determination of a plurality of lower blocks and the transmission of a plurality of lower blocks are stopped, and the determination flag F for each block is transmitted together with the encoded code.

Further, according to the present invention, in the image coding method of sequentially recursively dividing the image data into a plurality of hierarchical data having a plurality of different resolutions and coding the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is judged for a specified block in the data, and when the block activity is less than the specified threshold value, the split stop flag is temporarily set as a judgment flag for a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. When the block activity of one of the blocks is equal to or more than a predetermined threshold value, the division stop flag is changed to the division continuation flag, and the determination flag for each block is transmitted together with the encoded code.

Further, in the present invention, the image data is recursively divided into a plurality of hierarchical data having different resolutions, and the highest hierarchical data having the lowest resolution and each hierarchical data excluding the highest hierarchical data. And an image encoding method for encoding the inter-layer difference data for a plurality of layers, which is the difference value of the adjacent upper layer data, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the highest layer. , If the block activity is less than a predetermined threshold value, a split stop flag is set once as a determination flag of a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block activity of one of the plurality of lower blocks is predetermined. If the threshold is greater than or equal to the threshold of Flag was set to be transmitted together with the encoded code.

Further, according to the present invention, in an image coding apparatus which represents image data using a recursive hierarchical representation and performs hierarchical coding, adaptive block division corresponding to the property of the image data is executed to perform coding. The encoding means for encoding and the transmitting means for transmitting the hierarchical encoded data obtained by the division result are provided.

Further, according to the present invention, in an image coding apparatus for sequentially recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and coding the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is determined for a predetermined block of data, and when the block activity is less than a predetermined threshold value, a split stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. The block activity determination and the transmission of a plurality of lower blocks are stopped, and the division control means for transmitting the determination flag for each block together with the encoding code is provided.

Further, in the present invention, the image data D31
Is recursively divided into a plurality of hierarchical data D31 to D35 having different resolutions, and the highest hierarchical data D35 having the lowest resolution, each hierarchical data D31 to D34 excluding the highest hierarchical data D35, and adjacent upper data. The image encoding device 4 that encodes the inter-layer difference data D40 to D43 for a plurality of layers that is the difference value of the layer data D32 to D35.
At 0, the block activity A is determined for a predetermined block of the inter-layer difference data D40 to D43 of each layer except the top layer, and when the block activity A is less than the predetermined threshold Tha, the inter-layer difference data D40 of the adjacent lower layer. In D42, the division stop flag is set as the determination flag F of the plurality of lower blocks corresponding to the blocks, the block activity determination of the plurality of lower blocks and the transmission of the plurality of lower blocks are stopped, and the determination flag F of each block. The division control means 50, 51, 52, 53 for transmitting the code together with the encoded code are provided.

Further, according to the present invention, in an image coding apparatus which recursively divides image data into a plurality of hierarchical data having a plurality of different resolutions and encodes the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is judged for a specified block in the data, and when the block activity is less than the specified threshold value, the split stop flag is temporarily set as a judgment flag for a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and a plurality of lower blocks are set. When the block activity of one of the blocks is equal to or more than a predetermined threshold value, the division stop flag is changed to the division continuation flag, and the division control means for transmitting the determination flag for each block together with the encoding code is provided.

Further, in the present invention, the image data is recursively divided into a plurality of hierarchical data having different resolutions, and the highest hierarchical data having the lowest resolution and each hierarchical data excluding the highest hierarchical data. And an image encoding device for encoding inter-layer difference data for a plurality of hierarchies consisting of difference values of adjacent upper layer data, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the highest layer. , If the block activity is less than a predetermined threshold value, a split stop flag is set once as a determination flag of a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block activity of one of the plurality of lower blocks is predetermined. If the threshold is greater than or equal to the threshold of Flag was set to provide a division control means for transmitting with the encoded code.

[0022]

When the image data is expressed using the recursive hierarchical representation and hierarchically encoded, the adaptive block division corresponding to the property of the image data is executed and encoded, and the division result is obtained. It is possible to reduce the amount of information such as a flat portion of an image by adaptively dividing the blocks of the lower layer by transmitting the hierarchically encoded data that is generated.

Further, the block activity is determined for a predetermined block of hierarchical data excluding the highest hierarchical data having the lowest resolution, and when the block activity is less than a predetermined threshold value, a plurality of lower blocks corresponding to the block in adjacent lower hierarchical data are detected. By setting the division stop flag as a judgment flag, stopping the block activity judgment of a plurality of lower blocks and transmission of a plurality of lower blocks, and transmitting the judgment flag for each block together with the coding code It is possible to prevent unnecessary block encoded data from being transmitted according to the block activity of the data, reduce the code amount, and improve the compression efficiency of the encoded data.

Further, the block activity A is determined for a predetermined block of the inter-layer difference data D31 to D34 of each layer except the highest layer D35, and when the block activity A is less than a predetermined threshold Tha, the difference between the adjacent lower layers. A division stop flag is set as the determination flag F of a plurality of lower blocks corresponding to the blocks in the data D40 to D42, the block activity determination of the plurality of lower blocks and the transmission of the plurality of lower blocks are stopped, and the determination of each block is performed. By transmitting the flag F together with the encoded code, the inter-layer difference data D4
According to the block activity A of 0 to D43, unnecessary block encoded data can be prevented from being transmitted, the code amount can be reduced, and the compression efficiency of the encoded data can be improved.

Further, when the image data is sequentially recursively divided into a plurality of hierarchical data having a plurality of different resolutions and encoded, a block activity is determined for a predetermined block in the hierarchical data except the highest hierarchical data having the lowest resolution. If the block activity is less than the predetermined threshold value, the split stop flag is set once as the determination flag of the lower blocks corresponding to the block in the adjacent lower layer data, and the block of one of the lower blocks is blocked. When the activity is equal to or higher than a predetermined threshold, the split stop flag is changed to the split continuation flag, and the determination flag for each block is transmitted together with the coding code, so that the image quality is degraded according to the block activity of the hierarchical data. It is necessary to prevent the block and judge the necessity of the block, and to remove unnecessary coding data. Resulting to not transmit the data, can improve the compression efficiency of the coded data to reduce the amount of codes. .

The image data is sequentially recursively divided into a plurality of hierarchical data having a plurality of different resolutions, and the highest hierarchical data having the lowest resolution, each hierarchical data excluding the highest hierarchical data, and adjacent upper hierarchical data. When encoding the inter-layer difference data for multiple hierarchies consisting of the difference value of, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the top layer, and the block activity is less than the predetermined threshold value. In this case, the split stop flag is set once as the judgment flag of multiple lower blocks corresponding to the block in the adjacent lower layer data, and if the block activity of one of the multiple lower blocks is greater than or equal to the specified threshold, the split is stopped. Change the flag to the division continuation flag and transmit the judgment flag for each block together with the coded code. By doing so, it is possible to prevent the deterioration of the image quality according to the block activity of the inter-layer difference data, judge the necessity of the block, and prevent unnecessary encoded data from being transmitted, thereby reducing the code amount. The compression efficiency of encoded data can be improved.

[0027]

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 Layered Coding FIG. 1 shows, as a whole, the principle of layered coding according to the present invention in which a still image such as a high definition television signal is layered and compressed. In this layer coding, the upper layer data is created by a simple arithmetic average of the lower layer data, the lower layer data to be transmitted is reduced, and the layer structure without increasing the information amount is realized. Further, regarding decoding of upper layer data to lower layer data, the amount of information in the flat portion is reduced by adaptively controlling division based on the activity of each block. Furthermore, in the encoding of the inter-layer difference data performed for the lower layer data, the efficiency is realized by switching the quantization characteristic for each block without additional code based on the activity of the upper layer data.

That is, in the hierarchical structure of this hierarchical encoding,
First, the input high-definition television signal is used as the lowest layer data, and the four pixels X _{1 to} X _{4 in} the small block of 2 lines × 2 pixels of this lowest layer data 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 data. In this lower layer data,

[Equation 2] As shown in, the inter-layer difference data with respect to the upper layer data 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 hierarchy data, the three pixels X _{1 to} X ₃ are

[Equation 3] As shown in, the decoded value E [X _i ] is obtained by adding the inter-layer difference data ΔX _i to the average value m of the upper layer data, and the remaining 1 pixel is

[Equation 4] As shown by, the decoded value E [X ₄ ] is determined by subtracting the three decoded values of the lower layer data from the average value m of the upper layer data. E [] means a decoded value.

Here, in this hierarchical encoding, the resolution is quadrupled from upper layer to lower layer, but in the flat part, 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 judged as a local activity, for example, the maximum value of the inter-layer difference data.

As an example of this hierarchical encoding, an ITE HD standard image (Y signal) is used, and the adaptive division result when divided into five layers and encoded is shown in FIG. In the figure, the ratio of the number of pixels in each layer to the original number of pixels when the threshold value for the maximum inter-layer difference data is changed is shown, but it can be seen that the redundancy is reduced based on the spatial correlation. Although the reduction efficiency changes depending on the image, if the threshold value for the maximum inter-tier difference data is changed to 1 to 6, the average reduction rate is 28 to 69.
〔%〕become.

In practice, the resolution of the upper layer data is quadrupled to form lower layer data, at which time the difference data between layers from the upper layer data is encoded in the lower layer data to effectively reduce the signal level width. it can. FIG. 3 shows the case of five layers by the layer coding described above with reference to FIG. 2, but here, the layers are numbered from the lower layers to the first to fifth layers. It can be seen that the signal level width is reduced as compared to the 8-bit PCM data of the original image. In particular, since the first to fourth layers having a large number of pixels are difference data between layers, a significant reduction can be achieved and efficiency is improved by subsequent quantization. As can be seen from the table in Fig. 3, the reduction efficiency has little dependence on the pattern,
Valid for all pictures.

Further, by making the upper layer data by the average value of the lower layer data, the lower layer data is converted into the difference from the average value of the upper layer data while keeping the error propagation within the block, thereby improving the efficiency. Can also be held together. In the 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 data from the quantization result of the upper layer data, the inverse quantization of the receiving side can be performed. It is possible to realize an adaptive quantizer that does not need to transmit quantization information for (but excluding initial values).

Practically, an image is hierarchically encoded based on the above-mentioned five-stage hierarchical structure and expressed at a plurality of resolutions, and adaptive division and adaptive quantization using the hierarchical structure are performed.
Various HD standard images (8 bit Y / P _B / P _R ) 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 of Embodiment In FIG. 4, reference numeral 40 generally indicates an image encoding device according to the present invention. For example, input image data D31 which is a still image such as a high-definition television signal is described above. As the layer coding, the data is divided into five layers, and the lowest layer data obtained as a result and the inter-layer difference data for four layers are encoded. In fact, in the image encoding device 40, the input image data D31 is input to the first difference circuit 41 and the first averaging circuit 42.

As shown in FIG. 5, the first averaging circuit 42 starts from the four pixels X1 (1) to X4 (1) of the input image data D31, which is the first layer data as the lowest layer, to the second pixel. The pixel X1 (2) of the hierarchical data D32 is generated. Similarly, the pixels X2 (2) to X4 (2) adjacent to the pixel X1 (2) of the second hierarchical data D32 also have the first hierarchical data D3.
It is generated by averaging 4 pixels of 1. The second layer data D32 is the second difference circuit 43 and the second averaging circuit 44.
Entered in. The second averaging circuit 44 generates the pixel X1 (3) of the third hierarchical data D33 by averaging the four pixels of the pixels X1 (2) to X4 (2) of the second hierarchical data D32, for example. Pixel X1 (3) of this third layer data D33
Similarly, the pixels X2 (3) to X4 (3) adjacent to are also generated by averaging four pixels of the second hierarchical data D32.

Further, the third hierarchical data D33 is input to the third difference circuit 45 and the third averaging circuit 46. Third
The averaging circuit 46 of the third hierarchical data D3 is also similar to the above.
From the four-pixel average of the three pixels X1 (3) to X4 (3),
The pixels X1 (4) to X4 (4) of the fourth layer data D34 are generated. The fourth layer data D34 is input to the fourth difference circuit 47 and the fourth averaging circuit 48. Similarly to the above, the fourth averaging circuit 48 also generates the fifth layer data D35, which is the highest layer, by averaging the four pixels of the pixels X1 (4) to X4 (4) of the fourth layer data D34.

In practice, the first to fifth hierarchical data D31 to
The block size of D35 is the second when the block size of the first layer data D31 which is the lowest layer is 1 × 1.
Hierarchical data D32 is 1/2 × 1/2, third hierarchical data D
33 is 1/4 × 1/4, and fourth layer data D34 is 1/8
× 1/8, 5th layer data D3 which is the highest layer data
5 becomes 1/16 × 1/16.

In this way, the five hierarchical data D31 ...
The first to fourth layer data other than the fifth layer data D35 of the highest layer of D35 are the first, second, third, and fourth difference circuits 41, 4 as described above regarding the equation (2).
Difference calculation is performed at 3, 45, and 47, and the calculation result is generated as inter-layer difference data D40, D41, D42, and D43.

In practice, first, the fourth difference circuit 47 calculates the difference between the fifth layer data D35 and the fourth layer data 34 to generate the fourth layer inter-layer difference data D43, and then the fourth layer data D43. The difference circuit 45 of No. 3 performs a difference operation between the fourth layer data D34 and the third layer data D33 to generate inter-layer difference data D42 of the third layer.
Further, next, the second difference circuit 43 performs a difference operation on the third layer data D33 and the second layer data D32 to generate inter-layer difference data D41 of the second layer, and finally in the first difference circuit 41. Second layer data D32 and first
The difference calculation is performed on the layer data D31 to generate the first layer difference data D40 between layers.

As described above, the image coding apparatus 4 of this embodiment
0, the fifth layer data D35, the fourth layer to the first layer
Inter-layer difference data D43 to D40 of layers are sequentially generated in this order. At this time, in the image encoding device 40,
As described above with respect to the equation (2), by generating the lower layer data in association with the upper layer data,
The number of pixels to be encoded is not increased so that the reduction of compression efficiency can be avoided even when the image data is decomposed into a plurality of layers and encoded.

These inter-tier difference data D40 to D43
Are input to the division control circuits 50, 51, 52 and 53, respectively. The division control circuits 50 to 53 sequentially determine from the inter-layer difference data D43 to D40 of the upper layer, the determination with the block activity threshold Tha indicating whether or not a predetermined block in the inter-layer difference data D40 to D43 is a flat portion. Then, it is determined whether or not to transmit the following inter-layer difference data D42 to D40. For example, when the activity in the block of the difference data D43 between layers of the fourth layer is A,

[Equation 5] If the condition is satisfied, it is determined that the image data is a flat portion and is not likely to deteriorate, and a determination flag F indicating that the image data is not transmitted is set.

At the same time, the division control circuit 53 sends a control signal C3 to the division control circuit 52 of the third hierarchy. As a result, the division control circuit 52 of the third layer is provided with the inter-layer difference data D4.
Unconditionally abort the transmission of 2. The division control circuits 52 of the third and second layers are controlled by a control signal C indicating an unconditional suspension of transmission.
When 3 and C2 are received, they are sent as they are to the lower division control circuits 51 and 50 as control signals C2 and C1. As a result, under the control of the division control circuits 53 to 50, the inter-layer difference data D42 to D4 of all lower layers.
The transmission of 0 is unconditionally aborted.

In this way, the division control circuits 50 to 53 are provided.
Difference data D40 to D4 of each layer sent from
3 is sent to the encoders 54 to 57. Further, the fifth layer data D35 of the highest layer is sent to the encoder 58 as it is. The encoders 54 to 57 use the non-linear encoding method suitable for encoding the difference data to obtain the inter-layer difference data D4.
0 to D43 are compression-encoded to generate first to fourth hierarchical compression-encoded data D45 to D48. Further, the encoder 58 uses the linear encoding method suitable for encoding the image data composed of the average value data to obtain the fifth layer data D35.
Is compression-encoded to generate fifth-layer compression-encoded data D49.

The determination flag F sent from each of the division control circuits 50 to 53 is input to the control code generation circuit 59. As a result, the control code generation circuit 59 causes the control code D including the determination flag F for each layer and each block.
Generate 50. This control code D50 is the first to fifth
The hierarchical compression coded data D45 to D49 are coded by run-length coding or the like and transmitted as a coded code.

The first to fifth information transmitted in this manner
Hierarchical compression coded data D45 to D49 and control code D5
0 is decoded by the image decoding device 60 shown in FIG. That is, the first to fifth layer compression encoded data D45 to
The D49 is input to the decoders 61 to 65 having a decoding method reverse to that of the encoders 54 to 58, respectively. As a result, the first to the fourth decoded by the decoders 61 to 64, respectively.
The inter-tier difference data D51 to D54 of the tiers are passed through the first to fourth tier division control circuits 70 to 73, respectively, to the first
~ Is input to the fourth adders 75 to 78.

The fifth layer compression coded data D49 is decoded by the decoder 65, and the resulting fifth layer data D55 is output as it is and the fourth addition circuit 7 is also provided.
8 is input. The fourth adder circuit 78 adds the fifth layer data D55 and the inter-layer difference data D54 of the fourth layer to restore the fourth layer data D59, which is output and also sent to the third adder circuit 77. .

Similarly, the third addition circuit 77 adds the restored fourth layer data D59 and the third layer difference data D53 between layers to restore the third layer data D58, and outputs it. It is sent to the second adder circuit 76. In the same manner, the second layer data D57 and the first layer data D56 are restored from the second and first addition circuits 76 and 75, and the first to fourth layer data D56 are thus restored.
~ D59 and D55 are output.

The control code D50 is input to the control code analysis circuit 66. The control code analysis circuit 66 analyzes whether or not the transmission stop of the inter-layer difference data has occurred based on the input control code D50, and sends the analysis result as the transmission stop flag F to the division control circuits 70 to 73. To do. When the division control circuits 70 to 73 detect that the transmission of the inter-layer difference data has been stopped based on the input transmission stop flag F, instead of the inter-layer difference data, for example, the value “0” is set as dummy data. Inter-layer difference data is generated and sent to the addition circuits 75 to 78.

In this way, according to the block activity of the inter-layer difference data, the image encoding device 40 does not transmit the inter-layer difference data of unnecessary blocks but only the control data indicating the transmission stop. By doing so, the image decoding device 60 can reliably restore the hierarchical data based on the control data.

According to the above configuration, the block activity is judged for a predetermined block of the inter-layer difference data of each layer except the top layer, and when the block activity is less than the predetermined threshold value, the inter-layer difference data of the adjacent lower layer. In addition to setting the split stop flag as the judgment flag of the lower order blocks corresponding to the block, the block activity judgment of the lower order blocks and the transmission of the lower order blocks are stopped, and the judgment flag of each block is coded. Since it is transmitted along with the block code, unnecessary block encoded data can be prevented from being transmitted according to the block activity of the inter-layer difference data, and the code amount can be reduced to improve the compression efficiency of the encoded data. The encoding method and the image encoding device can be realized.

(3) Other Embodiments In the above embodiment, the block activity is judged by the block of the inter-layer difference data, and when the block activity is less than the predetermined threshold value, the division to the lower layer is stopped. The case where the control signals C1, C2, C3 for instructing are transmitted and the division stop flag is set as the determination flag of the plurality of lower blocks corresponding to the block in the lower layer difference data and the transmission is stopped has been described. The present invention is not limited to this, and as shown in FIG. 7, when the block activity is less than a predetermined threshold value, the control signals C1, C2, C3 for instructing to stop the division are sent to the lower layer and the lower layer. The split stop flag is set once as a determination flag for a plurality of lower-order blocks corresponding to the blocks in the inter-difference data, When the block activity of any of the blocks is equal to or higher than a predetermined threshold value, the control signals C4, C5, C6 for re-division are sent to the division control circuit 51, 52 or 53 of the upper hierarchy and the division stop flag is divided Instead of the continuation flag, the determination flag for each block may be transmitted together with the encoded code.

To realize this, in the image coding apparatus described above with reference to FIG. 4, the division control circuit determines the block activity for all the inter-layer difference data, and the upper division control circuit stops transmission. When the block activity is detected to be equal to or higher than the threshold value even if the control data of the above is input, the lower division control circuit sends an instruction to change the transmission stop to the transmission continuation to the upper division control circuit. Just do it.

Further, in the above-mentioned embodiment, the image data is recursively divided into a plurality of hierarchical data having a plurality of different resolutions, and the highest hierarchical data having the lowest resolution,
The case where each layer data excluding the top layer data and the inter-layer difference data for a plurality of layers formed by the difference value of the adjacent upper layer data is described, but the present invention is not limited to this, and the image data is It can also be applied to the case of sequentially recursively dividing and encoding into a plurality of hierarchical data having a plurality of different resolutions. In this case, if the block activity determination is performed on the block of the hierarchical data instead of the inter-layer difference data, the same effect as that of the above-described embodiment can be realized.

In the above embodiment, the case where the maximum value in the block and the threshold value are determined as the block activity has been described, but the present invention is not limited to this.
As the block activity, the average value in the block,
The sum of absolute values, standard deviation, sum of n powers, etc. may be judged against a threshold value, and even if the frequency of data exceeding a predetermined threshold value is used in the block, the same as in the above-mentioned embodiment. The effect can be realized.

Further, in the above embodiment, when dividing into a plurality of hierarchical data, the adjacent upper hierarchical data is recursively formed sequentially from the arithmetic mean of the image data or adjacent lower hierarchical data for each predetermined block. However, the present invention is not limited to this, and it is also possible to recursively form the adjacent upper layer data by a weighted average such that a predetermined weighting is performed and an average is taken. Can also be applied to the case where the upper hierarchy data is recursively formed.

In the above embodiment, the block activity in the block is determined, and the transmission of the data of the lower layer is stopped.
Whether or not to stop the transmission is limited to the block activity, and the property of other image data may be used.
In this way, the coding efficiency can be improved by adaptively dividing the block according to the property of the image data.

[0059]

As described above, according to the present invention, when the image data is expressed using the recursive hierarchical representation and hierarchically encoded, the adaptive block division corresponding to the property of the image data is executed. In addition to encoding, the hierarchically encoded data obtained as a result of the division is transmitted, and the block in the lower layer is adaptively divided to reduce the amount of information such as a flat portion of the image. It is possible to realize an image coding method and an image coding apparatus capable of performing the above.

The block activity is determined for a predetermined block of hierarchical data excluding the highest hierarchical data having the lowest resolution, and when the block activity is less than a predetermined threshold value, a plurality of lower blocks corresponding to the block in adjacent lower hierarchical data are determined. By setting the split stop flag as a flag, stopping the block activity determination of multiple lower blocks and transmitting multiple lower blocks, and transmitting the determination flag for each block together with the coding code, the hierarchical data It is possible to realize an image coding method and an image coding apparatus which can prevent unnecessary block coded data from being transmitted according to the block activity, and can reduce the code amount and improve the coded data compression efficiency.

The block activity is determined for a predetermined block of the inter-tier difference data of each layer other than the highest layer, and when the block activity is less than a predetermined threshold value, a plurality of blocks corresponding to the block in the inter-layer difference data of the adjacent lower layer are determined. The split stop flag is set as the determination flag of the lower block of the above, the determination of the block activity of the plurality of lower blocks and the transmission of the plurality of lower blocks are stopped, and the determination flag of each block is transmitted together with the encoding code. By doing so, it is possible to prevent unnecessary block encoded data from being transmitted according to the block activity of the inter-layer difference data, reduce the code amount, and improve the compression efficiency of the encoded data, and an image encoding method. The device can be realized.

Further, the block activity is determined for a predetermined block in the hierarchical data excluding the highest hierarchical data having the lowest resolution, and when the block activity is less than the predetermined threshold value, a plurality of lower blocks corresponding to the block in the adjacent lower hierarchical data are obtained. When the block activity of one of the multiple lower blocks is greater than or equal to the predetermined threshold, the split stop flag is set as the determination flag of the split stop flag, the split stop flag is changed to the split continuation flag, and the determination flag for each block is coded. By transmitting the encoded data together with the encoded code, it is possible to prevent the deterioration of the image quality according to the block activity of the hierarchical data, judge the necessity of the block, and prevent unnecessary encoded data from being transmitted. Image coding method that can reduce the amount and improve the compression efficiency of coded data And it can realize an image coding apparatus. .

Further, the block activity is determined for a predetermined block of the inter-layer difference data of each layer other than the highest layer, and when the block activity is less than a predetermined threshold value, a plurality of lower blocks corresponding to the block in the adjacent lower layer data are detected. Once the split suspension flag is set as the determination flag, and if the block activity of any of the multiple lower blocks is greater than or equal to the predetermined threshold, the split suspension flag is changed to the split continuation flag and the determination flag for each block is encoded. By transmitting with the code, it is possible to prevent the deterioration of the image quality according to the block activity of the inter-layer difference data, judge the necessity of the block, and prevent unnecessary encoded data from being transmitted.
An image coding method and an image coding apparatus capable of reducing the code amount and improving the compression efficiency of coded data can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining hierarchical coding as a principle of an image coding method and an image coding apparatus according to the present invention.

FIG. 2 is a chart showing an adaptive division result of an HD standard image using the hierarchical encoding.

FIG. 3 is a table showing standard deviations of signal levels of respective layers of an HD standard image using the hierarchical encoding.

FIG. 4 is a block diagram showing an image coding apparatus as an embodiment of the image coding method and the image coding apparatus according to the present invention.

FIG. 5 is a schematic diagram showing a structure of hierarchical data in hierarchical encoding.

FIG. 6 is a block diagram showing an image decoding device corresponding to the image encoding device of the embodiment.

FIG. 7 is a block diagram showing the configuration of an image encoding device according to another embodiment.

FIG. 8 is a block diagram showing an image coding apparatus using a conventional pyramid coding method.

9 is a block diagram showing an image decoding device corresponding to the image encoding device of FIG. 8. FIG.

[Explanation of Codes] 40 ... Image coding device, 41, 43, 45, 47 ...
Subtractors, 42, 44, 46, 48 ... Averaging circuit, 5
0, 51, 52, 53, 70, 71, 72, 73 ... Divided control circuit, 54, 55, 56, 57, 58 ... Encoder, 59 ... Control code generation circuit, 61, 62, 63,
64, 65 ... Decoder, 75, 76, 77, 78 ... Adder, 66 ... Control code analysis circuit.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

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[Fig. 2]

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[Figure 8]

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Claims (16)

[Claims] 1. An image coding method for hierarchically coding image data using a recursive hierarchical representation, wherein adaptive block division corresponding to the property of the image data is executed, and the division result is obtained. An image coding method characterized in that the obtained hierarchical coded data is transmitted. 2. An image coding method for recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and coding the image data, wherein the hierarchical data except the highest hierarchical data having the lowest resolution is used. The block activity is determined for a predetermined block, and when the block activity is less than a predetermined threshold value,
A division stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in adjacent lower layer data, and determination of the block activity of the plurality of lower blocks and transmission of the plurality of lower blocks are stopped, and An image encoding method characterized in that a determination flag for each block is transmitted together with an encoding code. 3. The image data is recursively divided into a plurality of hierarchical data having a plurality of different resolutions, the highest hierarchical data having the lowest resolution, each hierarchical data excluding the highest hierarchical data, and adjacent upper data. In an image encoding method for encoding inter-layer difference data for a plurality of hierarchies consisting of difference values of layer data, determining block activity for a predetermined block of the inter-layer difference data of each layer except the highest layer, When the block activity is less than a predetermined threshold,
A division stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in the difference data between adjacent lower layers, and the block activity determination of the plurality of lower blocks and transmission of the plurality of lower blocks are performed. And the decision flag for each block is transmitted together with the coding code. 4. An image coding method, wherein image data is sequentially and recursively divided into a plurality of hierarchical data having a plurality of different resolutions and coded, in the hierarchical data excluding the highest hierarchical data having the lowest resolution. The block activity is determined for the predetermined block of, and when the block activity is less than the predetermined threshold value,
When a division stop flag is set once as a determination flag for a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block activity of any one of the plurality of lower blocks is equal to or more than a predetermined threshold value, the division is performed. An image coding method, characterized in that a stop flag is changed to a division continuation flag, and the determination flag for each block is transmitted together with a coding code. 5. The image data is sequentially and recursively divided into a plurality of hierarchical data having a plurality of different resolutions, and the highest hierarchical data having the lowest resolution, each hierarchical data excluding the highest hierarchical data, and adjacent upper data. In an image encoding method for encoding inter-layer difference data for a plurality of hierarchies consisting of difference values of layer data, determining block activity for a predetermined block of the inter-layer difference data of each layer except the highest layer, When the block activity is less than a predetermined threshold,
When a division stop flag is set once as a determination flag for a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block activity of any one of the plurality of lower blocks is equal to or more than a predetermined threshold value, the division is performed. An image coding method, characterized in that a stop flag is changed to a division continuation flag, and the determination flag for each block is transmitted together with a coding code. 6. When dividing into the plurality of hierarchical data, adjacent upper hierarchical data is recursively formed sequentially from a weighted average of the image data or adjacent lower hierarchical data for each predetermined block. The image coding method according to claim 2, claim 3, claim 4, or claim 5. 7. The maximum value, the average value, the sum of absolute values, the standard deviation, or the n-th power sum of the hierarchical data or the hierarchical difference data in the predetermined block is used as the block activity. The image coding method according to claim 2, claim 3, claim 4, claim 5, or claim 6. 8. The block activity determination is performed by using the number of data in which the hierarchical data or the inter-tier difference data in the predetermined block exceeds a predetermined threshold value. The image coding method according to claim 3, claim 4, claim 5, or claim 6. 9. An image coding apparatus for hierarchically coding image data using a recursive hierarchical representation, wherein coding is performed by performing adaptive block division corresponding to the property of the image data. An image coding apparatus, comprising: a means and a transmission means for transmitting hierarchically encoded data obtained by the division result. 10. An image coding apparatus for recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and coding the image data, wherein the hierarchical data other than the highest hierarchical data having the lowest resolution is used. The block activity is determined for a predetermined block, and when the block activity is less than a predetermined threshold value, a division stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in the adjacent lower layer data, and the plurality of lower layers are set. An image coding apparatus, comprising: division control means for stopping the determination of the block activity of a block and the transmission of the plurality of lower blocks, and transmitting a determination flag for each block together with an encoding code. 11. The image data is sequentially recursively divided into a plurality of hierarchical data having different resolutions, and the highest hierarchical data having the lowest resolution, each hierarchical data excluding the highest hierarchical data, and adjacent upper data. In an image encoding device for encoding inter-layer difference data for a plurality of hierarchies consisting of difference values of layer data, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the highest layer, When the block activity is less than a predetermined threshold value, a division stop flag is set as a determination flag of a plurality of lower blocks corresponding to the block in the difference data between adjacent lower layers, and the blocks of the plurality of lower blocks are set. The activity judgment and the transmission of the above-mentioned lower blocks are stopped, and the judgment flag for each block is stopped. An image coding apparatus comprising a division control means for transmitting a lag together with a coded code. 12. An image encoding apparatus for sequentially recursively dividing image data into a plurality of hierarchical data having a plurality of different resolutions and encoding the hierarchical data except the highest hierarchical data having the lowest resolution. The block activity is determined for a predetermined block of, when the block activity is less than a predetermined threshold value, the division stop flag is once set as the determination flag of the plurality of lower blocks corresponding to the block in the adjacent lower layer data, and the plurality of the plurality of blocks are set. When the block activity of any one of the lower blocks is equal to or higher than a predetermined threshold value, the division stop flag is changed to a division continuation flag, and a division control means for transmitting the determination flag for each block together with an encoding code is provided. An image encoding device characterized by the above. 13. Image data is sequentially recursively divided into a plurality of hierarchical data having different resolutions, and the highest hierarchical data having the lowest resolution, each hierarchical data excluding the highest hierarchical data, and adjacent upper data. In an image encoding device for encoding inter-layer difference data for a plurality of hierarchies consisting of difference values of layer data, the block activity is determined for a predetermined block of the inter-layer difference data of each layer except the highest layer, When the block activity is less than a predetermined threshold value, a division stop flag is temporarily set as a determination flag of a plurality of lower blocks corresponding to the block in adjacent lower layer data, and the block of any block of the plurality of lower blocks is set. When the activity is equal to or higher than a predetermined threshold value, the division stop flag is changed to the division continuation flag and An image coding apparatus comprising a division control means for transmitting a determination flag for each block together with a coding code. 14. When dividing into the plurality of hierarchical data, the adjacent upper hierarchical data is recursively formed sequentially from a weighted average of the image data or adjacent lower hierarchical data for each predetermined block. Claim 10, Claim 1
The image coding apparatus according to claim 1, claim 12, or claim 13. 15. The maximum value, average value, sum of absolute values, standard deviation or sum of n-th powers of the hierarchical data or the hierarchical difference data in the predetermined block is used as the block activity. The image encoding device according to claim 10, claim 11, claim 12, claim 13 or claim 14. 16. The determination of the block activity is as follows.
11. The claim 10, claim 11, claim 12, claim 13 or claim 11, wherein the number of data in which the layer data or the inter-layer difference data in the predetermined block exceeds a predetermined threshold is used. Item 15. The image encoding method according to Item 14.