JPH0575867A - Image data coder - Google Patents

Abstract

PURPOSE:To make it possible to perform an encoding with code quantity in accordance with significance degree every area in a picture, to perform the encoding without the degradation of the reproducibility of a significant area and to suppress the total code quantity of the whole picture to fixed quantity or less. CONSTITUTION:As for the block of an area B shown by an area setting part 103, a code quantity control part 107 performs an encoding for the conversion factor of the number held in an area B minimum conversion factor number setting part 105. As for the block of an area A shown by an area setting part 102, the control part 107 makes a DCT/encoding part 101 perform an encoding by increasing code quantity allotted to the block of the area B when the total code quantity of the whole picture when an encoding is performed for all the conversion factors is smaller than a maximum total code quantity held in a whole code quantity setting part 106 and by decreasing code quantity allotted to the block of the area A when the total code quantity is larger than the maximum total code quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data coding apparatus used in an image data storage apparatus, an image data transmission apparatus, etc., for compressing image data by coding, and particularly to a fixed data amount after coding. The present invention relates to an image data encoding device that encodes so as to be less than or equal to the amount.

[0002]

2. Description of the Related Art When encoding image data such as a still image and compressing the data, attention is paid to the fact that the data in the adjacent regions in the image have a high correlation.
It is divided into a plurality of blocks of N pixels, data in each block consisting of N × N pixels is subjected to orthogonal transform such as discrete cosine transform (DCT) and quantized, and the obtained transform coefficient is encoded and compressed. The method of doing is sometimes used.

When discrete cosine transform is applied to the two-dimensional block of N × N pixels, energy is generally concentrated in low-order terms, and thus the obtained transform coefficient is hatched in (FIG. 10), for example. The low order coefficients shown often have relatively large values. In particular, with regard to the transform coefficients of a block having many low frequency components, those having large numerical values are concentrated in the coefficients at the upper left of the block, and those having small numerical values or zero are large at the lower right.

Therefore, when the above transform coefficients are quantized and coded, a variable length coding method is often used to improve the efficiency of data compression by the following processing. That is, for example, when encoding a transform coefficient obtained by performing orthogonal transform on a block of 8 × 8 pixels,
1) sequentially scan coefficient data in the order indicated by the arrow
The data is arranged in a dimension, and the number of consecutive zero coefficients and the non-zero coefficient value are paired to form group data, and the group data is encoded.

More specifically, for example, as shown in (FIG. 12), in the case of a block in which only the coefficient indicated by the symbol Z is a non-zero coefficient, the number of zero coefficients before the coefficient Z (3
9) and the value of the coefficient Z are encoded as group data, and zero coefficients after the coefficient Z are not encoded and EOB is not encoded.
(End Of Block) code is added to generate one block of code data.

As described above, the block is used as a processing unit, and the processing of this block unit is performed on the entire image. In this case, the amount of data after encoding (hereinafter referred to as the amount of code).
Varies depending on the number of non-zero coefficients in each block. By the way, when storing and transmitting image data, it is sometimes necessary to not only compress the data but also to suppress the code amount to a certain amount or less.

For example, when applied to a still camera or the like,
If the code amount for each image is not less than a certain amount, the number of images that can be recorded on a recording medium (magnetic disk, memory card, etc.) of a predetermined capacity will change, and the minimum number of recorded images cannot be guaranteed. Further, when applied to a moving image display device or the like, it is necessary to suppress the code amount to be equal to or less than the amount of data that can be written to or read from the storage medium within a certain time according to the field frequency and the like.

Therefore, for example, by obtaining an activity indicating the fineness of the image for each block and setting the code amount of each block according to this activity,
A method is known in which the total code amount of the entire image is suppressed below a certain amount. (1989 National Congress of Television Society 19-
22) Hereinafter, an example of the image data encoding device to which the above method is applied will be described based on (FIG. 13) and (FIG. 14).

FIG. 13 is a block diagram showing the structure of the image data encoding device. The blocking unit 1002 converts the image data 1001 into 8 blocks as shown in (FIG. 14).
The image data is divided into blocks of × 8 pixels and the image data of each block is output to the activity calculation unit 1003 and the encoding unit 1006. The activity calculation unit 1003 calculates an activity for each block.

The total activity calculation unit 1004 accumulates the above activities to obtain the total activity for one image. The code amount control unit 1005 obtains the bit allocation of each block from the ratio of the activity of each block and the total activity. The encoding unit 1006 encodes, for each block, the number of zero coefficients and the value of non-zero coefficients in order as described above, and when the code amount exceeds the above bit allocation, the higher order All the coefficients of are regarded as zero coefficients and the encoding is stopped.

As described above, by controlling the code amount based on the activity for each block, the total code amount of the entire image can be suppressed to a certain amount or less, and the code amount becomes higher in a portion where the degree of fineness of the image is higher. Is set to a large number to improve the reproducibility of the image when it is decoded.

[0012]

However, in the image data encoding apparatus using the above-mentioned method, the higher the activity of the block, the higher the reproducibility of the image. Since a block with high activity is not necessarily a high importance part in the image, for example, even in a high importance part near the center of the image, if the degree of detail is low, the code amount is suppressed small, There is a problem that the reproducibility may deteriorate.

In view of the above points, the present invention is capable of reliably storing and transmitting image data of an important area by performing encoding with a code amount according to the degree of importance of each area in an image. It is an object of the present invention to provide an image data encoding device capable of suppressing the total code amount of the entire image to a fixed amount or less.

[0014]

In order to achieve the above object, the present invention divides an image into a plurality of blocks composed of a plurality of pixels, and obtains transform coefficients obtained by orthogonally transforming image data of each block. In an image data encoding device for encoding, a first code amount obtained by encoding all transform coefficients for a block belonging to a first area in an image, and a second code amount
When the total code amount, which is the sum of the second code amount obtained by encoding the predetermined number of transform coefficients for the blocks belonging to the area of, is smaller than the preset code amount,
All the transform coefficients are coded for blocks belonging to the first area, and the blocks belonging to the second area are coded by allocating the code quantity of the difference between the set code quantity and the first code quantity. When the total code amount is larger than the set code amount, for blocks belonging to the first area,
A block belonging to the second area is coded by allocating a code amount of the difference between the set code amount and the second code amount,
It is characterized by further comprising code amount control means for encoding the predetermined number of transform coefficients.

[0015]

With the above arrangement, the code amount control means has the first code amount obtained by coding all the transform coefficients for the block belonging to the first area of the image and the predetermined number of blocks belonging to the second area. Second encoded transform coefficient of
If the total code amount, which is the sum of the code amounts of the above, is smaller than the preset code amount, all the transform coefficients of the blocks belonging to the first region are coded to belong to the second region. For the block, the code amount of the difference between the set code amount and the first code amount is assigned and coded, and when the total code amount is larger than the set code amount,
For a block belonging to the first area, the code amount of the difference between the set code amount and the second code amount is assigned and encoded,
For the blocks belonging to the second area, the predetermined number of transform coefficients are encoded.

[0016]

(Embodiment 1) An image data encoding apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the image data encoding device.

In the figure, the DCT / encoding unit 101
For example, as shown in FIG. 2, the image data in the image 301 is divided into 8 × 8 pixel blocks 302, and the image data in each block is subjected to the discrete cosine transform (DC).
T), and the obtained conversion coefficient is used for the code amount control unit 10 which will be described later.
The encoding is performed based on the control of 7. The area setting units 102 and 103 hold information for identifying whether each block 302 belongs to the area A near the central portion shown in FIG. 2 or the area B in the peripheral portion. ..

The priority setting unit 104 uses the areas A and B described above.
Information indicating that the area A has a higher degree of importance is held. The area B minimum conversion coefficient number setting unit 105 holds the minimum number of conversion coefficients to be coded for each block 302 belonging to the area B. As the number of conversion coefficients, a certain image quality is guaranteed. A value of 21, for example, is set as the required number of coefficients. The number of transform coefficients may be set in advance, or may be set each time encoding is performed according to the image to be encoded.

The total code amount setting unit 106 holds information indicating the maximum total code amount as the upper limit of the total code amount of the entire image. As the maximum total code amount, for example, all blocks 302 have the above minimum value. It is set to a value sufficiently larger than the code amount when encoded with the number of transform coefficients. The code amount control unit 107 controls the DCT / encoding unit 101 based on the area to which each block 302 belongs, the degree of importance of the area, and the maximum total code amount.

More specifically, the code amount control unit 107 is configured to perform the following control. First, DC
Regarding the block 302 in the area B, the T / encoding unit 101 is caused to perform encoding on the transform coefficient having the minimum number of transform coefficients among the transform coefficients obtained by DCT, while regarding the block 302 in the area A, , All transform coefficients are encoded, and the total code amount of the entire image is calculated.

When the total code amount is smaller than the maximum total code amount, the code amount assigned to the block 302 in the area B is increased. That is, the block 302 in the area B
For, the encoding is performed on more transform coefficients than the minimum transform coefficient number. If the total code amount exceeds the maximum total code amount, the code amount assigned to the block 302 in the area A is decreased. That is, for the block 302 in the area A, the number of transform coefficients to be coded is reduced.

An example of a specific operation of the image data encoding device configured as described above will be described. DCT
The encoding unit 101 first inputs 8 × the input image data.
The image data is divided into 8-pixel blocks 302, and the image data of each block is DCT sequentially from the upper left block.

The code amount control unit 107 includes an area setting unit 102.
Based on the information from 103, which of the areas A and B each block 302 belongs to is identified, and the priority order setting unit 1
For the block 302 belonging to the area A, which is shown to have high importance based on the information from 04, the DCT / encoding unit 101 is caused to perform coding on all transform coefficients, while the block 302 belonging to the area B about,
The region B minimum transform coefficient number setting unit 105 is caused to perform coding on the number (21) of transform coefficients set.

More specifically, the DCT / encoding unit 101
For example, as shown in (FIG. 3), the transform coefficient set 303 of the block 302 belonging to the area A is represented by the symbols a, b, c, d.
When it consists of non-zero coefficient indicated by and other zero coefficient, coefficient data are sequentially scanned in the order shown by the arrow in the figure and arranged into one-dimensional data, and as shown in (FIG. 4), The number of zero coefficients up to coefficient a and the value of coefficient a, the number of zero coefficients from coefficient a to coefficient b and the value of coefficient b ...
-The number of zero coefficients from coefficient c to coefficient d and the value of coefficient d are each paired and coded, and finally EOB (end
of code) to generate code data 304.

The DCT / encoding unit 101 also uses the block 302 belonging to the area B as shown in (FIG. 5), for example.
When the conversion coefficient set 305 of No. 1 is composed of non-zero coefficients indicated by symbols e, f, g, and h, and other zero coefficients, the low-frequency component to the area B minimum conversion indicated by hatching in FIG. The conversion coefficients of the minimum conversion coefficient number (21) set in the coefficient number setting unit 105 are encoded, and as shown in FIG. 6, the number of zero coefficients up to the coefficient e and the value of the coefficient e, And the number of zero coefficients from the coefficient e to the coefficient f and the value of the coefficient f are encoded as a pair, and the EOB code is added to generate the code data 306.

Next, the code amount control unit 107 causes each block 3
The total code amount of the entire image is calculated by accumulating the code amount for each 02, and it is determined whether the total code amount is smaller than the maximum total code amount set in the total code amount setting unit 106. When the total code amount is smaller than the maximum total code amount, it is obtained by dividing the difference between the maximum total code amount and the total code amount of the blocks 302 belonging to the area A by the number of blocks 302 belonging to the area B. The code amount is assigned to each block 302 in the area B, and the DCT
-The encoding unit 101 is made to perform encoding again.

Therefore, the DCT / encoding unit 101 encodes all the transform coefficients for each block 302 in the area A as in the first step, while for each block 302 in the area B, for example (FIG. 7). As shown in, coded data 307 is generated by performing coding up to a transform coefficient that does not exceed the assigned code amount. (When encoding up to the transform coefficient h, if the code amount of the block exceeds the assigned code amount, the coding of the block is completed up to the transform coefficient g.) When the code amount is larger than the maximum total code amount, a code obtained by dividing the difference between the maximum total code amount and the total code amount of the blocks 302 belonging to the area B by the number of blocks 302 belonging to the area A The amount is allocated to the block 302 of the area A, and the DCT
-The encoding unit 101 is made to perform encoding again.

In this case, the DCT / encoding unit 101
For each block 302 in the area A, the coding is performed up to the transform coefficient that does not exceed the assigned code amount, while for each block 302 in the area B, the coding for the 21 transform coefficients is performed as in the first coding. I do. In this way, the total code amount of the entire image when the transform coefficient having the minimum number of transform coefficients for the block 302 of the area B and all the transform coefficients of the block 302 of the area A are encoded is smaller than the maximum total code amount. If it is also smaller, all the transform coefficients are coded for each block 302 in the area A, and as many transform coefficients as possible for each block 302 in the area B are coded, and are larger than the maximum total code amount. In this case, each block 302 in the area A is encoded with as many transform coefficients as possible, and each block 302 in the area B is encoded with the minimum transform coefficient necessary to guarantee a certain image quality. Therefore, the total code amount of the entire image can be suppressed to the maximum total code amount or less while ensuring the reproducibility according to the importance of each area.

In the above example, only one area A having a high degree of importance is set, but the present invention is not limited to this. For example, three or more area setting units may be provided, You may comprise so that the several area | region A with high importance may be set. (Embodiment 2) Hereinafter, as another embodiment of the present invention, an image data coding apparatus capable of setting importance in three or more steps will be described with reference to the drawings. In the second embodiment, components having the same functions as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 8 is a block diagram showing the structure of the image data encoding device. In the figure, the area setting unit 20
2, 203 holds information for identifying to which area each block 302 of 8 × 8 pixels belongs in advance, as in the first embodiment. The area setting units 202 and 203 respectively include a main area setting unit 2021, a sub area generating unit 2022, sub area setting units 2023 and 2024, and a selector unit 2025.
Alternatively, the main area setting unit 2031 and the sub area generating unit 20
32, sub area setting units 2033 and 2034, and a selector unit 2035.

Main area setting section 2021, 2031
Holds information for identifying whether each block 302 belongs to the area A near the central portion shown in FIG. 9 or the area B in the peripheral portion. The sub-region generation unit 2022 of the region setting unit 202 determines that each block 302 belonging to the region A further has the central portion of the region A shown in FIG. 9 based on the information held in the main region setting unit 2021. Information for identifying whether it belongs to the half area A1 or the peripheral area A2 is generated.

The sub-area setting sections 2023 and 2024 hold information on the areas A1 and A2 generated by the sub-area generating section 2022, respectively.
In addition, the sub-region generation unit 2032 and the sub-region setting units 2033 and 2034 of the region setting unit 203 are the same as the sub-region generation unit 2022 and the sub-region setting units 2023 and 202.
4 has the same function.

The selector sections 2025 and 2035 respectively include a main area setting section 2021 and a sub area setting section 20.
23/2024, or main area setting unit 2031
And the sub-region setting units 2033 and 2034 are selectively switched, and information regarding each region is output to the code amount control unit 207. Here, for the sake of simplicity of explanation, an example in which the selector unit 2035 is set so as to always select the main region setting unit 2031, that is, the region B is not further subdivided will be described. ..

The priority setting unit 204 uses the area A.
B, and information indicating the importance of the areas A1 and A2 are held. For example, information indicating that the area A is higher than the area B and the area A1 is higher than the area A2 is held. .. Area B / A2 minimum conversion coefficient number setting unit 20
5 is a block 302 belonging to the area B or the area A2
The minimum number of transform coefficients to be encoded is held, and the number of transform coefficients is the number of coefficients required to guarantee a certain image quality according to the importance of each area, for example, area B Is set to 21 and the area A2 is set to a value larger by a predetermined number.

The code amount control unit 207 controls each block 302.
Controls the DCT / encoding unit 101 based on the area to which the area belongs, the degree of importance of the area, and the maximum total code amount.
For the block 302 in the area A, all transform coefficients are coded, and when the total code amount of the entire image is smaller than the maximum total code amount, the same as the code amount control unit 107 of the first embodiment. 21 about the block 302 of the area B
Encoding is performed on more transform coefficients than the number of transform coefficients, and when the total code amount exceeds the maximum total code amount, the number of transform coefficients to be encoded is further controlled for the areas A1 and A2. Is becoming

A specific example of the operation of the image data coding apparatus configured as described above will be described. DCT
The encoding unit 101 first inputs 8 × the input image data.
The image data is divided into 8-pixel blocks 302, and the image data of each block is DCT sequentially from the upper left block.

On the other hand, the selector sections 2025 and 2035 of the area setting sections 202 and 203 select the main area setting sections 2021 and 2031 respectively, and output information indicating which of the areas A and B each block 302 belongs to. .. The code amount control unit 207 identifies, based on the information from the selector units 2025 and 2035, which of the regions A and B each block 302 belongs to, like the code amount control unit 107 of the first embodiment, and gives priority. The block 30 belonging to the area A that is shown to have high importance based on the information from the rank setting unit 204.
For 2, the DCT / encoding unit 101 is caused to perform encoding on all transform coefficients, while for the block 302 belonging to the region B, the number set in the region B / A2 minimum transform coefficient number setting unit 205. The (21) transform coefficients are encoded, the code amount of each block 302 is accumulated to calculate the total code amount of the entire image, and the maximum total code set in the overall code amount setting unit 106 is calculated. Determine if less than quantity.

When the total code amount is smaller than the maximum total code amount, the code amount control unit 207 also determines the first embodiment.
Similarly, the code amount obtained by dividing the difference between the maximum total code amount and the total code amount of the blocks 302 belonging to the region A by the number of blocks 302 belonging to the region B is assigned to each block 302 of the region B. , The DCT / encoding unit 101 performs coding on all the transform coefficients for each block 302 in the area A as in the first step, while transforming each block 302 in the area B so as not to exceed the assigned code amount. Coding up to the coefficient is performed.

On the other hand, when the total code amount is larger than the maximum total code amount, the code amount control unit 207 further determines the area A1.
The control is performed so that the number of transform coefficients encoded in A2 is different. That is, first, the selector unit 2 of the area setting unit 202
025 selects the sub-region setting units 2023 and 2024, and each block 302 belonging to the region A is further divided into the region A.
Information indicating which of 1 and A2 it belongs to is output.

For the block 302 belonging to the area A1, the code amount control unit 207 is the DCT / encoding unit 101.
While all of the transform coefficients are coded, for the block 302 belonging to the area A2,
(2) Encoding the number of conversion coefficients set in the minimum conversion coefficient number setting unit 205 (not all the conversion coefficients, but the number of conversion coefficients greater than the number 21 set for the area B) is performed, The total code amount of the entire image is calculated by accumulating the code amount of each block 302, and it is determined again whether the total code amount is smaller than the maximum total code amount set in the total code amount setting unit 106.

When the total code amount is smaller than the maximum total code amount, the difference between the maximum total code amount and the total code amount of the blocks 302 belonging to the region B or the region A1 is calculated as the area A2.
The code amount obtained by dividing by the number of blocks 302 belonging to the area A2 is assigned to each block 302 of the area A2, and the DCT / encoding unit 101, for each block 302 of the area B or the area A1, respectively, similarly to the first time. 21 or all transform coefficients are coded while the area A
For each block 302 of No. 2, coding is performed up to a transform coefficient that does not exceed the assigned code amount.

When the total code amount is still larger than the maximum total code amount, the difference between the maximum total code amount and the total code amount of the blocks 302 belonging to the area B or the area A2 belongs to the area A1. The code amount obtained by dividing by the number of blocks 302 is assigned to each block 302 of the area A1,
The DCT / encoding unit 101 encodes 21 blocks or a predetermined number of transform coefficients larger than 21 for each block 302 in the region B or the region A2, respectively, as in the beginning. Each block 302 of A1
For, the coding is performed up to the transform coefficient that does not exceed the assigned code amount.

As described above, since the importance can be set in three or more steps, even when the importance of each area in the image is three or more steps, the code amount corresponding to each importance and It is possible to perform encoding so that the total code amount of the entire image is suppressed to a certain amount or less. Note that, in the second embodiment as well, similar to the first embodiment, a plurality of regions of each importance may be set.

Further, in the above-described first and second embodiments, an example is shown in which the information indicating which area each block 302 belongs to is set in advance, but the present invention is not limited to this. A region having a desired size and position may be set each time encoding is performed, depending on the image to be encoded.

[0045]

As described above, according to the present invention,
When the total code amount is smaller than the preset code amount, the blocks belonging to the first area are
All the transform coefficients are coded, and for the blocks belonging to the second area, the code amount of the difference between the set code amount and the first code amount is assigned and coded, while the total code amount is greater than the set code amount. Is larger, the blocks belonging to the first area are coded by allocating the code quantity of the difference between the set code quantity and the second code quantity, and the blocks belonging to the second area are subjected to the predetermined number. By including the code amount control means for encoding the transform coefficients of, all the transform coefficients of the blocks belonging to the first region are coded, or at least the set code amount and the second code amount are set. The code amount of the difference is assigned and encoded.

That is, the maximum transform coefficient is coded for the blocks belonging to the first area within the range in which the total code amount is suppressed to the set code amount or less. Therefore, it is possible to perform the encoding with the code amount according to the importance of each area in the image and to suppress the total code amount of the entire image to a certain amount or less.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of an image data encoding device according to a first embodiment.

FIG. 2 is an explanatory diagram showing an example of image region division.

FIG. 3 is an explanatory diagram showing an example of transform coefficients of blocks belonging to the same area A.

FIG. 4 is an explanatory diagram showing an example of code data obtained by coding all transform coefficients in a block.

FIG. 5 is an explanatory diagram showing an example of transform coefficients of blocks belonging to the same area B.

FIG. 6 is an explanatory diagram showing an example of code data obtained by coding the transform coefficients having the minimum transform coefficient number in the block.

FIG. 7 is an explanatory diagram showing an example of code data re-encoded within the allocated code amount range.

FIG. 8 is a block diagram illustrating a configuration of an image data encoding device according to a second embodiment.

FIG. 9 is an explanatory diagram showing an example of area division of an image.

FIG. 10 is an explanatory diagram showing the relationship between the order of conversion coefficients and energy.

FIG. 11 is an explanatory diagram showing a scan order of transform coefficients at the time of encoding.

FIG. 12 is an explanatory diagram showing an example of a method of pairing the number of zero coefficients and the value of non-zero coefficients at the time of encoding.

FIG. 13 is a block diagram showing a configuration of a conventional image data encoding device.

FIG. 14 is an explanatory diagram showing an example in which image data is divided into blocks of 8 × 8 pixels.

[Explanation of symbols]

 101 DCT / encoding unit 102 region setting unit 103 region setting unit 104 priority setting unit 105 region B minimum conversion coefficient number setting unit 106 overall code amount setting unit 107 code amount control unit 202 region setting unit 2021 main region setting unit 2022 sub Region generation unit 2023 Sub region setting unit 2024 Sub region setting unit 2025 Selector unit 203 Region setting unit 2031 Main region setting unit 2032 Sub region generating unit 2033 Sub region setting unit 2034 Sub region setting unit 2035 Selector unit 204 Priority setting unit 205 Region B / A2 minimum conversion coefficient number setting unit

Claims (2)

[Claims] 1. An image data encoding device for dividing an image into a plurality of blocks made up of a plurality of pixels, and encoding a transform coefficient obtained by orthogonally transforming image data of each block, comprising: A total code that is the sum of a first code amount obtained by encoding all transform coefficients for blocks belonging to a region and a second code amount obtained by encoding a predetermined number of transform coefficients for blocks belonging to a second region When the amount is smaller than the preset set code amount, all transform coefficients are coded for the block belonging to the first region, and the set code amount and the first code are set for the block belonging to the second region. When the total code amount is larger than the set code amount, the first code is assigned.
For the blocks belonging to the area, the code amount of the difference between the set code amount and the second code amount is assigned and coded.
An image data encoding apparatus comprising a code amount control means for encoding the predetermined number of transform coefficients for blocks belonging to the area. 2. The image data encoding device according to claim 1, wherein the code amount control means, in the case where the total code amount is larger than a set code amount, a block belonging to the first area,
A code amount of the difference between the set code amount and the second code amount is assigned, and further, all the transform coefficients of the blocks belonging to the first sub region in the first region are coded in the first sub. The total sub-code amount that is the sum of the code amount and the second sub-code amount obtained by encoding a predetermined number of transform coefficients for blocks belonging to the second sub-region in the first region is the first sub-code amount. If it is smaller than the code amount assigned to the block belonging to the area, all transform coefficients are encoded for the block belonging to the first sub area, and the assigned code is assigned for the block belonging to the second sub area. Coding is performed by allocating a code amount of a difference between the amount and the first sub-code amount, and when the total sub-code amount is larger than the assigned code amount, the blocks belonging to the first sub-region are assigned. , A code amount of a difference between the assigned code amount and a second sub code amount is assigned and encoded, and the predetermined number of transform coefficients is encoded for a block belonging to the second sub region. An image data encoding device characterized by being provided.