JPH04179371A - Device and method for encoding picture data - Google Patents

Abstract

PURPOSE:To encode a picture within prescribed time and within a prescribed code amount without damaging the quality of the picture by controlling the code amount so that it is within an allocated code amount obtained by means of combining the excess and lack of the allocated code amount of respective blocks and the allocated code amount till a previous block in accordance with the encoding order of respective decided color components. CONSTITUTION:An encoding circuit 80 is provided with an orthogonal conversion circuit 4, a quantizing circuit 6, a Huffman encoding circuit 8 as a variable length encoding, a quantizing width prediction circuit 12, a code amount calculation circuit 14, a code amount allocation circuit 20 and a code stop circuit 16. Optimum quantizing width and the allocated code amount for respective blocks are decided from the code amounts for respective blocks, which are obtained from a statistical processing, and a difference between the code amount generated by encoding in the processed block and the allocated code amount is added to the allocated code amount of the block being the object of a processing, and variable length encoding is stopped lest it exceeds the allocated code amount. On the other hand, a processing order by the individual color components is decided in correspondence with code amount prediction values by the individual color components. Thus, the encoding processing can be executed within prescribed processing time and within the prescribed code amount without damaging the quality of the picture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an encoding device and encoding method for highly compression encoding image data to a predetermined capacity.

[Conventional technology]

When an image signal captured by a solid-state imaging device such as a CCD is stored as digital data in a storage device such as a memory card, magnetic disk, or magnetic tape, the amount of data is enormous, so many frames are required. In order to record images within a limited storage capacity, it is necessary to perform some kind of highly efficient compression on the obtained image signal data. Furthermore, in digital electronic still cameras, captured images are stored as digital data on storage media such as memory cards, magnetic disks, or magnetic tapes instead of silver halide films. The number of images that can be recorded on one roll of magnetic tape device is specified, and recording of this specified number of images must be guaranteed, and the time required for data recording and reproduction processing is short and constant. Is it necessary?

Similarly, digital VTR (video tape recorder),
When recording moving images such as digital moving image files, it is necessary to be able to record various amounts of frames without being affected by the amount of image data per frame.

In other words, whether it is a still image or a moving image, it is necessary to be able to reliably record the required number of frames, and the time required for data recording and reproduction processing must be short and constant. .

A coding method that combines orthogonal transform coding and variable length coding is widely known as a highly efficient image data compression method.

A typical example is a method being considered in the international standardization of still image coding.

An outline of this method will be explained below. First, image data is divided into blocks of a predetermined size, and a two-dimensional DCT (discrete cosine transformation) is performed as orthogonal transformation for each divided block. Next, linear quantization is performed according to each frequency component, and Huffman encoding is performed on the quantized values as [2 variable length rod encoding. At this time, regarding the DC component, the difference value between it and the DC component of the neighboring block is Huffman encoded.

AC components are invalidated by scanning from low frequency components to high frequency components called zigzag scan (value or O)
Two-dimensional Huffman encoding is performed from the consecutive number of components and the values of the subsequent effective components.

In this basic portion, since Huffman coding, which is variable length coding, is used, the amount of code is not constant for each image.

Therefore, the following method has been proposed as a method for controlling the amount of code. First, at the same time as processing the basic part, the total amount of codes generated for the entire screen is determined.

From this total code amount and the target code amount, the optimum quantization width for approaching the target code amount for the DCT coefficient is predicted. Next, using this quantization width, the processing after quantization of the basic portion is repeated.

Then, from the total code amount generated this time, the total code amount generated last time, and the target code amount, the optimum quantization width to bring the target code amount closer again is predicted.

If the predicted quantization width and the previous quantization width are sufficiently close and the total amount of code generated this time is smaller than the target code amount, the process is terminated and the code is output. If not, the process is repeated using a new quantization width.

For the quantization width, a quantization matrix is prepared as a basic form representing the relative quantization characteristics for each frequency component, and this quantization matrix is multiplied by a quantization coefficient to obtain the necessary quantization width. Specifically, first, the above-mentioned basic part is quantized using the quantization width obtained using standard quantization coefficients, and then this is variable-length encoded, and the information on the total code amount obtained by this is , a comparison is made with the preset target total code amount, which is the limit that should be accommodated, and when the target total code amount is reached, the final encoding process is performed using that quantization width, and the target total code amount is reached. If the amount does not fall within the amount, the optimal quantization coefficient that approaches the target total code amount is determined by linear prediction from the generated total code amount and the target total code amount, and
A more optimized quantization width is calculated from the obtained quantization coefficient and quantization matrix, and this is used to perform the final encoding process. The quantization width is changed using this method.

However, with the method of controlling the amount of code described above, the number of times the basic encoding pass is repeated differs depending on the image, which not only makes the processing time unstable, but also generally requires a long processing time. There was.

Therefore, the present inventors proposed the following method as a method to solve this problem. (Refer to Japanese Patent Application No. 1-283781 and Japanese Patent Application No. 2-137222.) This proposed method is a compression method that combines orthogonal transform and variable length coding, and in order to control the amount of generated code, The sampled image signal stored in is divided into blocks, orthogonal transformation is performed on each divided block, and the output of this transformation is quantized using a provisional quantization width. At the same time as variable-length encoding, the amount of generated codes for each block and the total amount of generated codes for the entire image are calculated, and then the provisional quantization width, the total amount of generated codes, and the target total amount of codes are calculated. , predict the new quantization width. Further, the allocated code amount for each block is calculated from the generated code amount for each block, the total generated code amount, and the target total code amount. Then, the image signal in the image memory is divided into blocks, orthogonally transformed, quantized, and variable length encoded again using the new quantization width, and if the generated code amount of each block exceeds the allocated code amount of each block, stops variable-length encoding midway through and moves on to processing the next block. This is intended to control the code amount so that the total generated code amount for the entire image does not exceed the target total code amount.

To explain the above operation in detail with reference to FIG.
57B pixels) into a block of a predetermined size (for example, 8×
) is divided into blocks A, B, C, ...) each consisting of 8 pixels, and as shown in (b), a two-dimensional DCT (discrete cosine transform) is performed as an orthogonal transform for each divided block. Stored sequentially on an 8x8 matrix. When image data is viewed on a two-dimensional plane, it has a spatial frequency that is frequency information based on the distribution of gradation information.

Therefore, by performing the above DCT, the image data is converted into a direct current component DC and an alternating current component AC, and data indicating the value of the direct current component DC is placed at the origin position (0,0 position) on the 8×8 matrix. At the 0.7 position, there is data indicating the maximum frequency value of the alternating current component AC in the horizontal axis direction, and
Data indicating the maximum frequency value of the alternating current component AC in the vertical axis direction is stored at the 7.0 position, data indicating the maximum frequency value of the alternating current component AC in the diagonal direction is stored at the 7.7 position, and the intermediate position Then, frequency data in directions related to each coordinate position are stored in a form in which higher frequencies appear sequentially from the origin side.

Next, by dividing the stored data at each coordinate position in this matrix by the quantization width for each frequency component,
Linear quantization is performed according to each frequency component (C), and Huffman encoding is performed as variable length encoding on this quantized value. , - At this time, regarding the DC component DC, the difference value with the DC component of the neighboring block is expressed by a group number (number of additional bits) and additional bits, the group number is Huffman encoded, and the obtained code word and additional bits are are combined into encoded data (dl, d2. el, e2)
.

Coefficients that are not valid (values other than "0") regarding the alternating current component AC are expressed by group numbers and additional bits.

Therefore, the AC component AC performs a scan called zigzag scan from low frequency components to high frequency components, and detects the number of consecutive invalid (value is "0") components (number of runs of zero) and the following valid components. Two-dimensional Huffman encoding is performed from the group number of the value, and the obtained code word and additional bits are combined to form encoded data.

Huffman encoding is the above DC component D per frame image.
The data distribution of C and alternating current component AC is centered around the peak frequency of occurrence in the data distribution, and bits are allocated in such a way that the center has fewer data bits, and the closer it is to the periphery, the larger the number of bits. This is done by encoding the data and obtaining a code word.

The above is the basic part of this method.

If only this basic part is used, the code will not be constant for each image because Huffman coding, which is variable length coding, is used, so the code amount is controlled, for example, as follows.

First, using a provisional quantization coefficient, the basic part is processed with the quantization width for each frequency component obtained by multiplying the predetermined quantization matrix and the quantization coefficient, and at the same time The total amount of generated codes (total number of bits) is determined (g). The optimum quantization coefficient for approaching the target code amount for the DCT coefficient is predicted from this total code amount, the target code amount, and the temporary quantization coefficient used (h). Next, using this quantization coefficient (I), the above-described processing after quantization of the basic part is repeated. Then, from the total code amount generated this time, the total code amount generated last time, the target code amount, the quantization coefficient used this time, and the quantization coefficient used last time, it is possible to approach the target code amount again. Newton-Raphson Iteration (Newton-Raphson Iteration)
n).

If the predicted quantization coefficient and the previous quantization coefficient are close enough, and the total amount of code generated this time is smaller than the target amount of code, the process is terminated, and the coded data generated this time is Output and store it on the memory card (f
). Otherwise, the quantization coefficient is changed and the process is repeated using this new quantization coefficient.

However, with the above code amount control method, the number of times the basic encoding pass is repeated varies depending on the image, which not only makes the processing time unstable, but also generally requires a long processing time. was there. Therefore, the present inventors solved this problem using the following method.

First, using a provisional quantization coefficient, the basic part is processed with the quantization width for each frequency component obtained by multiplying the predetermined quantization matrix and the quantization coefficient, and at the same time The total amount of generated codes (total number of bits) and the amount of generated codes for each block are determined (gl). The optimum quantization coefficient for approaching the target code amount for the DCT coefficient is predicted from this total code amount, the target code amount, and the used provisional quantization coefficient (hl). Further, the allocated code amount for each block is determined by proportional allocation from the total code amount, the target code amount, and the generated code amount for each block (h2). Next, using the pre-M1 quantized coefficients (i
), repeat the basic process described above. In other words, the image signal in the image memory is divided into blocks, orthogonally transformed, quantized, and variable-length encoded again, and if the generated code amount of each block exceeds the allocated code amount of each block, the variable-length code is Abort the process and move on to processing the next block.

When the above processing is completed for all blocks, the encoded data generated this time is output and stored in the memory card (f).

[Problem to be solved by the invention]

As mentioned above, for example, in a digital electronic still camera, there must be a guaranteed number of images that can be recorded on one medium, card, magnetic disk device, or one magnetic tape. Image data is compressed and recorded, but from the viewpoint of operability, the processing time must be as short as possible and constant. It is also desirable to be able to compress image data with high efficiency. These are items that are required not only for digital electronic still cameras but also for other applications.

As a compression method that satisfies these requirements, there is the International Standard East method mentioned above. However, because variable-length encoding is used, the amount of code is not constant, and the number of images that can be stored on a recording medium such as a memory card, magnetic disk, or magnetic tape is limited. There was a drawback that the number of sheets was indefinite.

In addition, as a conventional technique to solve this problem, there is a code amount control method that is being considered in the international standardization of still image coding mentioned above, but in this method, the number of passes of the basic part of encoding is repeated. Not only does the processing time vary depending on the image, but it also has the disadvantage that it generally requires a long processing time.

Japanese Patent Application No. 1-283761 and Japanese Patent Application No. 2-137222 proposed by the present inventors as a method to solve this problem.
There is a number method. The proposed method may usually give very good results, or depending on the system in which it is applied, the image quality may be slightly degraded for images with particularly low or particularly high spatial frequencies, and the amount of code generated may be less than the target amount. In rare cases, the difference in code amount may be slightly larger than in the normal case.

The cause of this will be explained. As mentioned above, when expressing the quantization width by multiplying the quantization matrix, which is the basic form expressing the relative quantization characteristics for each frequency component, by the quantization coefficient, there is a difference between the quantization coefficient and the amount of generated code. has approximately the following relationship.

log BR-a log sp+ b-
(1) Here, BR is the code tkc bit rate per pixel), SF is the quantization coefficient, and a and b are constants, where a is particularly dependent on the system and b is particularly dependent on the image.

When quantizing a color image separated into color components, multiple quantization matrices are used for the color components, for example, two quantization matrices, one for luminance and one for color difference, and a common quantization coefficient is used. If we use log BRy = a, log SF+ b,
−(2) log BRc −a, log S
The relationship becomes F+ b c- (3). In addition, in each of the above formulas, BR.

y and c are added to aSb to distinguish between brightness and color difference. Here, if B, , wm a, then
log(BRy +BRc) -ay log sp + (10by+10”
)-a log SF+ b-(4)
The code amount to be allocated to each block is determined by proportionally distributing the target code amount according to the statistics.

If you get it, you know it's good.

In the normal case, the force is % a7 '' ac- (although, depending on the system, the magnitudes of a, and ac may be quite different depending on the system).

In other words, the total code amount log BR is plotted on the Y axis, and the quantization coefficient l
og SF on the Y axis and the relationship between equations (2) and (3) is shown in Figure 9. The magnitude of the total code JilogBR according to the quantization coefficient log SP is slightly different for the luminance system and color difference system. There is a difference. Looking at FIG. 9, we can see that when the quantization coefficient during encoding, that is, the quantization coefficient predicted to be the optimal value, is particularly large or small, in other words, when the image has a particularly high spatial frequency, Alternatively, in the case of a low-quality image, if the allocated code amount is determined by proportionally allocating the target code amount according to the statistics of each block, the actual encoding is performed using the predicted quantization coefficient. In this case, the allocated code amount becomes insufficient for the luminance component block, and becomes redundant for the chrominance component block, or vice versa.

Whether the allocated code amount for the luminance component is insufficient or the allocated code amount for the chrominance component is insufficient depends on the magnitude relationship between a and ao and the magnitude of the predicted quantization coefficient.

Due to the above reasons, depending on the applied system, the image quality may deteriorate slightly for images with particularly low or particularly high spatial frequencies, and the gap between the generated code amount and the target code amount may be slightly larger than in normal cases. There was.

Therefore, an object of the present invention is to enable encoding of images within a certain amount of code within a certain processing time without degrading the image quality, even if the image has a biased spatial frequency distribution. An object of the present invention is to provide an encoding device and method for encoding image data.

[Means for Solving the Problems] In order to achieve the above object, the present invention is configured as follows.

That is, each color image data separated by color component is divided into blocks, orthogonal transformation is performed for each divided block by color component, and the output of this transformation is quantized by a quantization means. The encoded output is given to a variable-length encoding means to be variable-length encoded, and when encoding data, it is first quantized with a provisionally determined quantization width and then variable-length encoded, and the code amount for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and according to the determined optimal quantization width, each block is In an encoding device that performs encoding processing of quantizing the transform output of and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block, First, the difference between the amount of code generated by the encoding of the processed block processed before the block to be encoded next and the amount of allocated code for the processed block is calculated. a code amount allocating means which adds this and the allocated code amount of the processing target block and allocates it as an allocated code amount in the processing target block; and a code amount allocation means when performing encoding processing on the processing target block. a coding aborting unit that aborts the variable length coding so as not to exceed the assigned allocated code amount; code order determining means for determining the processing order for each color component in the encoding process of image data; and a control means for controlling the encoding process.

Second, the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next among the blocks and the amount of allocated code in the processed block. a code amount allocating means that calculates and adds this and the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block; and the code amount allocation means during encoding processing of the processing target block. encoding terminating means for terminating the variable length encoding so as not to exceed the allocated code amount allocated by;
code order determining means for determining a processing order for each color component in the encoding process of the color image data from the tentatively determined quantization width and the optimum quantization width; and a processing order determined by the code order determining means. and a control means for controlling the color image data of color components having higher ranks to perform encoding processing according to power color component ranks.

Thirdly, a compression rate selection means for selecting a target compression rate and determining the target code amount to be accommodated and the provisional quantization width according to the selected compression rate; a code amount calculation means for calculating the code amount of the entire image of variable-length encoded transform coefficients and the code amount for each block; quantization width prediction means for predicting an optimal quantization width to be used in the encoding process from the target code amount and the provisional quantization width, and providing the predicted optimal quantization width to the quantization means; During encoding processing, the difference between the amount of code generated by encoding in the processed block processed before the next target block to be encoded among the blocks and the amount of code allocated to the processed block. and the code amount allocation means which adds this and the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block; a coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the code amount allocating means; and a code for each color component when quantizing at the optimum quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data according to the amount predicted value; and a control means for controlling encoding processing based on the component color image data.

Fourth, there is a code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing, and the image calculated by the code amount calculation means. The optimum quantization width to be used in the encoding process is pre-Ml based on the total code amount, the target code amount to be stored, and the provisional quantization width, and the predicted optimum quantization width is sent to the quantization means. quantization width prediction means for giving
Next, find the difference between the amount of code generated by encoding in the processed block processed before the target block to be encoded and the allocated code amount in the processed block, and calculate the difference between this and the code amount allocated to the target block. and a code amount allocating means which adds the allocated code amount and allocates it as the allocated code amount in the processing target block; coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount; and coding of the color image data according to the predicted code amount for each color component when quantizing with the optimum quantization width. code order determining means for determining the processing order of each color component in the encoding process; and according to the color component order to be processed determined by the code order determining means, the color image data of the color component having a higher rank is subjected to encoding processing. The variable length encoding means obtains the difference between the DC component and the DC component in the previous processing block among the image data for each block obtained by the orthogonal transformation, and a DC component encoding processing unit that variable-length encodes this difference; and an AC component encoding processing unit that performs variable-length encoding on the AC component after the encoding processing unit finishes processing the DC component. and the encoding aborting means is provided only in the AC component encoding processing section.

Further, fifthly, a compression rate selection means for selecting a target compression rate and determining the target code amount to be accommodated and the provisional quantization width according to the selected compression rate; A code amount calculation means for calculating the code amount for the entire image and the code amount for each block of variable-length encoded transform coefficients, and the code amount for the entire image calculated by the code amount calculation means and the target code to be stored. quantization width prediction means for predicting an optimal quantization width to be used in the encoding process from the amount and the provisional quantization width, and providing the predicted optimal quantization width to the quantization means; At the time of processing, calculate the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next among the blocks and the amount of code allocated to the processed block. A code amount allocating means which adds this and the allocated code amount of the processing target block and allocates it as the allocated code amount in the processing target block, a coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the code amount allocating means; and a code for each color component when quantizing at the optimum quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data according to the amount predicted value; control means for controlling the encoding processing based on the component color image data, and the variable length encoding means controls the previous processing for the DC component among the image data in units of blocks obtained by the orthogonal transformation. a DC component encoding processing unit that obtains a difference from a DC component in a block and encodes this difference into a variable length code; and after the encoding processing unit finishes processing this DC component, a variable length An encoding processing section for the alternating current component to be encoded is provided, and the encoding aborting means is provided only in the encoding processing section for the alternating current component.

a code amount calculation means, a quantization width prediction means, a code amount allocation means, a coding abort means, a coding output means,
The variable length encoding means obtains a difference between the DC component and the DC component in the previous block among the image data in units of blocks obtained by the orthogonal transformation, and converts this difference into a variable length coder. An encoding processing unit for the DC component to be encoded, and an encoding processing unit for the AC component that performs variable length encoding on the AC component after the processing of the DC component encoding processing unit is completed, and the The encoding aborting means is provided only in the encoding processing section for AC components.

Sixthly, the color image data separated by color component is divided into blocks, orthogonal transformation is performed for each divided block, and the output of this transformation is quantized by a quantization means. The output is given to variable length encoding means to be variable length encoded, and when encoding data, the amount of code is assigned to each block according to the amount of allocated code for each block determined from the statistics for each block determined in advance. When performing variable length encoding while performing control, the quantization is performed using a provisional quantization width, and the resulting quantized output is encoded to generate the entire image necessary for optimization. The first step is to check the amount of code and the amount of code for each block.
In addition to predicting the quantization width necessary for optimization from the code amount of the entire image obtained in the first step,
a second step of determining the coding order of each color component from the predicted quantization width; a third step of determining a standard allocated code amount for each block from the code amount of each block; and a third step of determining the coding order of each color component from the predicted quantization width. A fourth step of performing the quantization for each block using the width, and varying the quantization output for each block and block in this fourth step within the allocated code amount for the block. 5th long code
of the block to be currently subjected to variable-length encoding processing in the fifth step, determining the difference between the code amount due to variable-length encoding in the block processed immediately before and the allocated code amount in that block; a sixth step of adding this amount as a carryover amount to the reference allocated code amount for the block to be currently processed, and setting it as the allocated code amount for the block to be currently processed; is characterized in that encoding is performed according to the encoding order of each color component obtained in the second step.

[For production]

In such a configuration, each color image data separated by color component is divided into blocks of a predetermined number of pixels,
After performing orthogonal transformation for each of these divided blocks for each color component, this transform output is quantized by a quantization means, and then this quantization output is given to a variable length encoding means to be variable length encoded, and the data is When performing encoding, first quantize with a provisionally determined quantization width, perform variable length encoding, perform statistical processing to obtain the code amount for each block, and then perform statistical processing to obtain the code amount for each block. The optimum quantization width and the allocated code amount for each block are determined from the code amount, and the transform output for each block is quantized according to the determined optimum quantization width, and this quantization output is quantized for each block. In the first configuration, the code amount allocating means performs coding processing to sequentially perform variable length encoding while controlling the code amount for each block according to the allocated code amount, or in the case of the first configuration, the code amount allocating means performs encoding The difference between the amount of code generated by encoding in the processed block processed before the target block to be processed and the allocated code amount in the processed block is calculated, and this and the allocated code amount of the target block are calculated. is added and allocated as the allocated code amount for the block to be processed. Then, the encoding aborting means aborts the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means during the encoding process on the processing target block. On the other hand, the code order determining means determines the processing order for each color component in the encoding process of the color image data according to the predicted code amount for each color component when quantizing with the optimum quantization width, and controls the The means performs control in accordance with the order of color components to be processed determined by the code order determining means, so that the color image data of color components having higher ranks are subjected to encoding processing.

In the case of the second configuration, the code amount allocation means includes the code amount generated by encoding in a processed block processed before the next target block to be encoded among the blocks, and the code amount generated by encoding in the processed block. The difference between the allocated code amount and the allocated code amount of the processing target block is calculated, and this difference is added to the allocated code amount of the processing target block, and the difference is allocated as the allocated code amount of the processing target block. Then, the encoding aborting means aborts the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means during the encoding process on the processing target block. On the other hand, the code order determining means determines the processing order for each color component in the encoding process of the color image data from the tentatively determined quantization width and the optimum quantization width, and the control means uses the code order determining means to determine the processing order for each color component in the encoding process of the color image data. In accordance with the determined ranking of color components to be processed, control is performed so that the color image data of color components with higher rankings are subjected to encoding processing.

The above describes how to know the state of the generated code using the provisional quantization width during statistical processing, predict the optimal quantization width from this information, and calculate the code amount from the color component with the least amount of code, for example. Decide the processing order of the color components to be processed, and also decide the standard allocated code amount for each block, and encode according to this processing order (in other words, the top one)
Starting from the color component, when encoding each block, the difference between the code amount and the allocated code amount in the encoding of the previous block is added as a carryover amount to the standard allocated code amount of that block to obtain the allocated code amount. For example, if you start processing from a color component with a small amount of code, the unused portion of the allocated code amount of the previously processed color component will be encoded within the allocated code amount. Since the carryover amount can be used for encoding later color components, there is less need to abort encoding in each block for color components that require a large amount of code, which contributes to image quality improvement and reduces the time required for encoding processing. By setting the number of times to a specified number, the time required for encoding can be kept constant.

In the case of the third configuration, when a target compression rate is selected, the compression rate selection means determines the target code amount to be accommodated and the provisional quantization width according to the selected compression rate. Further, the code amount calculation means calculates the code amount of the entire image of the variable-length encoded transform coefficient in the statistical processing and the code amount for each block, and the quantization width prediction means calculates the code amount of the entire image and the code amount for each block. The optimum quantization width to be used in the encoding process is predicted from the code amount of the entire image, the target code amount to be stored, and the provisional quantization width, and the predicted optimum quantization width is applied to the quantization means. Give width. Then, during the encoding process, the code amount allocation means
Among the blocks, the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the allocated code amount in the processed block is calculated. The allocated code amount of the block to be processed is added to the allocated code amount for the block to be processed. Furthermore, the encoding aborting means aborts the variable length encoding during encoding processing so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding of the processing target block. The code order determining means determines the processing order for each color component in the encoding process of the color image data according to the predicted code amount for each color component when quantizing with the optimum quantization width, and the control means In accordance with the order of color components to be processed determined by the code order determining means, control is performed so that the color image data of color components with higher ranks are subjected to encoding processing.

In this method, in addition to the functions and effects of the first and second configurations, the target compression rate can be selected, and the provisional quantization width and the target code per image power to be accommodated can be selected accordingly. Since the amount is determined and statistical processing is performed, an advantage is obtained that the optimum quantization width that fits within the desired code amount can be found with higher accuracy.

Further, in the case of the fourth configuration, the code amount calculation means calculates the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficient in the statistical processing, and the quantization width prediction means calculates the code amount of the entire image and the code amount for each block. Predicting the optimum quantization width to be used in the encoding process based on the code amount of the entire image calculated by the code amount calculation means, the target code amount to be stored, and the provisional quantization width, and predicting the optimum quantization width to be used in the encoding process, and This predicted optimal quantization width is given to . Further, during the encoding process, the code amount allocation means calculates the amount of code generated by the encoding of the processed block processed before the block to be encoded next among the blocks, and the code amount of the processed block. The difference between the allocated code amount and the allocated code amount of the processing target block is calculated, and this difference is added to the allocated code amount of the processing target block, and the difference is allocated as the allocated code amount of the processing target block. Furthermore, the encoding aborting means aborts the variable length encoding during encoding processing so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding of the processing target block. On the other hand, the code order determining means determines the processing order for each color component in the encoding process of the color image data according to the predicted code amount for each color component when quantizing with the optimum quantization width, The control means performs control in accordance with the determined order of the color components to be processed, so that the color image data of the color component having a higher order is subjected to encoding processing.

Here, the variable-length encoding means obtains a difference between the DC component and the DC component in the previous processing block among the image data for each block obtained by the orthogonal transformation, and converts this difference into a variable-length code. After the DC component has been processed by the encoding processing section, the AC component is variable-length encoded, and the encoding is terminated only in the encoding process for the AC component.

Therefore, in addition to the first and second cases above, it is possible to abort only the alternating current component during the encoding process, thereby limiting the abort to the high frequency region that has little visual impact, and improves image quality. can prevent deterioration.

In the fifth case, the desired compression ratio can be selected, and as a result, the effects of the third case can be obtained in addition to the effects of the fourth configuration.

In the sixth case, quantization is performed with a provisional quantization width,
Perform encoding processing on the quantized output obtained by this,
The amount of code required for the entire image and the amount of code for each block required for optimization are examined, and the quantization width required for optimization is predicted from the amount of code for the entire image obtained. Determining the coding order of each color component from the width, determining the standard allocated code amount for each block from the code amount of each block, and then performing the quantization for each block using the predicted quantization width. The quantized output for each block obtained here is variable-length encoded within the amount of code allocated to that block. On the other hand, the difference between the amount of code generated by variable length coding in the block processed immediately before the block to be currently subjected to variable length coding processing and the amount of allocated code for that block is calculated, and this is used as the carryover amount for the current processing. The code amount is added to the standard allocated code amount for the block to be processed, and the allocated code amount is set as the allocated code amount for the block to be currently processed, and encoding, that is, variable length encoding is performed within the range of this allocated code amount. Quantization using the predicted quantization width is performed according to the coding order of each color component.

In this way, the state of the generated code is first known using the provisional quantization width, the optimal quantization width is predicted from this information, and the code amount is determined from the amount of code, for example, from the color component with the smallest amount of code. Decide the processing order of the color components to be processed, and
The standard allocated code amount for each block is determined, and the encoding process starts from the color component with a higher rank (that is, the higher ranking one) according to this processing order, and when encoding each block, the standard allocated code amount for that block is The difference between the amount of code encoded in the previous block and the amount of allocated code is added as a carryover amount to obtain the allocated amount of code, and the code is encoded within the range of this allocated amount of code. If you start processing from the component, the unused portion of the allocated code amount for the color component processed first can be carried over and used for encoding the later color component, so colors that require a large amount of code can be In the component, the number of coding stops in each block is reduced, contributing to improved image quality, and if the number of times of coding processing is set to a prescribed number, the time required for coding can be kept constant.

In this way, the present invention first performs statistical processing, and through this statistical processing, obtains the statistics necessary for predicting the optimal quantization width and determining the amount of code allocated to each block, and also calculates the order in which each color component is encoded. Based on this information, we start the encoding process, and while looking at the encoded output sequentially according to the determined coding order of each color component, we calculate the allocated code amount for each block and the allocated codes up to the previous block. The code amount is controlled for each block by discontinuing variable length coding so that the amount of code is within the allocated code amount of the block obtained by combining the excess and deficiency of the amount.
The encoded output within the desired code amount is obtained as the final output.

This is based on the following idea.

As explained in the conventional example, when the quantization coefficient during encoding is particularly large or small, in other words, in the case of an image with a particularly high or low spatial frequency, the target code amount is determined according to the statistics of each block. When the allocated code amount is determined by proportionally distributing the quantized coefficients, when actual encoding is performed using the quantized coefficients, the allocated code amount is insufficient for the luminance component block and excessive for the chrominance component block. Yes, or vice versa. Then, the encoding of the color component for which the amount of code is insufficient is aborted midway, and the image quality naturally deteriorates. Whether such a phenomenon occurs or not, whether there is a shortage of allocated code for luminance or for one color difference, depends on the magnitude relationship between a in equation (2) and ac in equation (3) and prediction. This can be easily determined by the magnitude of the quantization coefficients, but this is determined by the system and the image. Therefore, in addition to using the extra allocated code for the code amount of the subsequent blocks, we decided on the order in which the color components with the extra allocated code amount are encoded based on the above-mentioned relationship, and according to that order, the code amount for each block was determined. Encoding is performed while controlling the amount of code.

Considering each color component together, by encoding using the predicted quantization coefficient, the value will be quite close to the target code amount without having to control the code amount for each block, so the amount of code will be unnecessary. If encoding is performed from the color components, the allocated code amount will be left over, and the shortage in the allocated code amount of the color component with insufficient code amount can be compensated for, and good results can be obtained for each color component. On the other hand, if encoding is performed starting from a color component with insufficient code amount, the image will deteriorate because the coding will be discontinued one after another for that color component, and the color component with excess code amount will be decoded one after another. There will be a surplus of codes, and the remainder will be completely wasted.

Therefore, according to the present invention, it becomes possible to encode images with a wide range of spatial frequencies within a certain amount of code within a certain processing time using a simple circuit without degrading the image quality as much as possible.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. When compressing and encoding color image data, the present invention conventionally processes each color component so that it falls within a predetermined code amount range. When a shortage occurs, high frequency components are often cut on the side of the insufficient color component, while this situation does not occur for the other color component, and the amount of code is rather excessive. This kind of irrationality occurs. This can be resolved by compressing and encoding the color components that are likely to be in excess first, and allocating the surplus to color components that are likely to be in short supply.

First, in order to make the present invention easier to understand, the basic idea of the present invention will be explained.

That is, the present invention, for example, uses one color image (screen)
The color image data for each color component is divided into blocks of a predetermined number of pixels, and each block is further processed by orthogonally transforming the data of the constituent pixels of that block. When quantizing, compression-encoding, and encoding so that the total code amount of each compression-encoded color component falls within the target code amount, the color image data separated into color components is first processed by -1. Through this statistical processing, we obtain the statistics necessary to predict the optimal quantization width and determine the standard allocated code amount for each program, and also determine from which color component to start the encoding process based on the predicted quantization width. The coding order of each color component is determined. and,
Based on this information, actual encoding processing is performed starting from the one with the highest encoding processing rank. Encoding is performed for each color component, or the encoding process is performed block by block in block order, and while looking at the encoded output, the standard allocated code amount for each block and the block before the processing block are determined. Encoding is performed while monitoring the code amount obtained by variable length encoding so that the amount of generated code is within the allocated code amount of the block obtained by adding up the excess or deficiency of the allocated code amount. When the generated code amount, including EOB code, reaches the allocated code amount, the encoding of that block is terminated, but the DC component is always encoded even if it exceeds the allocated code amount, and the excess or deficiency of the allocated code amount at that time is determined. The amount is memorized and the next block is encoded.

Statistical processing predicts the optimal quantization width, determines the coding order of each color component from the predicted quantization width, and obtains statistics that serve as a reference for determining the amount of code allocated to each block. belongs to.

By using this optimized quantization width in the encoding process, it is possible to get close to the desired amount of code, but if the upper limit of the amount of data for one image is specified, let alone 1 byte, Even one bit cannot exceed the target code amount.

Therefore, a standard allocated code amount, which is the standard allocated code amount for each block, is determined, and the remainder obtained by subtracting the generated code amount from the allocated code amount in the processing block immediately before the block from this standard allocated code amount. The allocated code amount obtained as a carryover amount and corrected by adding this carryover amount is set as the maximum limit for encoding processing in the block, and encoding control is performed so that encoding is performed within this range, except in special cases.

Adjustment of the allocated code amount by this carryover differs depending on the code amount at the time of encoding, so in the block where there is a surplus, the surplus is transferred to the block where there is a shortage, and the overall code amount is adjusted by carrying over. This is to rationally allocate the data within the target code amount. This provides a function for fine adjustment when the standard code amount is exceeded. In encoding each block, low frequency components are encoded sequentially from high frequency components, and when the guideline (allocated code amount per block) is exceeded, encoding of further high frequency components is discontinued.

This is because high frequency components of each block are omitted to minimize visual impact. Regarding the termination of the alternating current component, the fact that high frequency components tend to have less visual impact especially as the frequency becomes higher is utilized.

For blocks whose amount of code generated including EOB is less than or exactly the same as the allocated code amount, coding is completed without any problem, that is, the EOB is pushed. Then, the remainder is added to the allocated code amount for one block, and is used as the allocated code amount for the next block. Encoding of a block that exceeds the limit is terminated, and the encoding of that block is terminated, that is, an EOB is output. and,
The remainder is added to the allocated code amount for one block, and is used as the allocated code amount for the next block. This is not possible in reality unless the compression rate is extremely high, or in the unlikely event that the allocated amount of code is not enough to encode even the DC component, only the DC component will be encoded. The encoding of the block is completed, that is, the EOB is output.

Then, the insufficient amount of code is carried over to the next block as a shortage, the shortage is subtracted from the allocated code amount of one block, carried over to the next block, and the shortage is subtracted from the allocated code amount of one block. , is the allocated code amount for the next block. At this time, since EOB is also one of the codes, E
The amount of code including OB should be within the allocated code amount.

At this time, the purpose of the present invention is to prevent the allocated code amount from being wasted. If encoding is performed from a color component with an excess amount, the amount of allocated code will be left over, which can compensate for the shortage of the amount of allocated code for the color component with a shortage of code amount.
Good results are obtained for each color component.

From the above, especially in the case of images with high or low spatial frequencies, if the target code amount is proportionally allocated according to the statistics of each block and the allocated code amount is determined, the predicted quantization coefficient can be used to When actually encoding, the allocated amount of code may be insufficient for the luminance component block and redundant for the chrominance component block, or vice versa, resulting in colors for which the amount of code is insufficient. Since the encoding of the component is aborted midway through, the image quality naturally deteriorates, but
According to the present invention, it becomes possible to encode images with a wide range of spatial frequencies within a certain amount of code within a certain processing time without degrading the image quality as much as possible.

The present invention basically employs a method called a two-pass method in which two processes, statistical processing and coding processing, are performed to complete the coding. When performing long encoding, the standard allocated code amount assigned to each block is used as a standard, and variations in the generated code amount in each block are adjusted by absorbing it in the next block. This adjusted amount is set as the allocated code amount, and encoding in a block is performed within the range of this allocated code amount, and when the allocated code amount is exceeded, the encoding of that block is discontinued. However, image data is decomposed into DC and AC components by orthogonal transformation, and even if the code amount exceeds the allocated code amount for the DC component, which has a large visual impact, the coding will not be aborted and the next block will be processed. The allocated code amount is subtracted by the amount that exceeds the allocated code amount, and if there is a risk of the AC component entering the allocated code amount exceeding the allocated code amount, the encoding is terminated. Further, when the amount of code generated by encoding is less than the allocated code amount, the surplus is added to the allocated code amount of the next block to increase the allocated code amount of the next block. In this way, when the amount of code in the previous processing block is over or under the allocated code amount, the excess or deficiency is reflected in the allocated code amount of the next block and adjusted.

An embodiment of this device using the above principle will be described.

FIG. 1 shows an embodiment in which an image data encoding device according to the present invention is applied to a digital electronic still camera, and FIG. 2 shows a block diagram of the configuration of the image data encoding device according to the present invention. . Note that illustrations and explanations of mechanisms of the digital electronic still camera that are not directly related to the present invention will be omitted.

As shown in FIG. 1, a digital electronic still camera body (hereinafter referred to as electronic camera body) 1 includes an imaging system 40 that captures images, and a signal processing system that performs predetermined signal processing on the output of this imaging system 40. The signal processing circuit 60 has functions such as orthogonal transformation, linear quantization, variable length coding, etc.
An encoding circuit 80 compression-encodes and outputs the output of the encoder 80, and the image data and quantization width (or information corresponding to this) encoded by the encoding circuit 80 are transferred to a recording medium 71.
The system is comprised of a recording system 70 for recording data, a switch 30 for setting and inputting a desired data compression rate, and a control circuit 90 for controlling the entire system.

A switch 30 for setting an image compression rate is provided on the operation section of the electronic camera body 1, and the switch 30 is connected to a control circuit 90.

The imaging system 40 includes a lens 40a for forming an optical image.
and an image sensor 40b such as a CCD. The signal processing circuit 60 includes an amplifier 80 that performs amplification, noise removal, etc.
a and convert analog signals to digital signals ^/D
Converter 130b and buffer memory 6 consisting of RAM, etc.
0c, and a process circuit BOd that performs color signal formation and the like. The encoding circuit 80 includes, for example, an orthogonal transform circuit 4 that performs orthogonal transform such as DOT (discrete cosine transform), a quantization circuit 6 that performs linear quantization, and a Huffman encoding circuit 8 that performs Huffman encoding as variable length encoding. It further includes a quantization width prediction circuit 12, a code amount calculation circuit 14, a code amount allocation circuit 20, a code abort circuit 1B, and a control circuit 1B that performs control processing within the encoding circuit 80.

The recording system 70 includes an interface circuit 70a and a memory card 71 containing an IC memory used as a recording medium. The memory card door 1 is removably attached to the electronic camera body 1.

The control circuit 90 is realized by a microprocessor (MPU).

FIG. 6 shows a perspective view of the external appearance of the electronic camera body 1. The figure shows a binocular type, and 48 is L in the operation section.
A CD (liquid crystal) display 30 is a switch 30 in the operation section, and a tele/wide changeover switch, a shutter operation button 50, etc. are also provided. Also,
49 is a finder.

The LCD display 48 displays various values and conditions such as the shooting mode, number of frames, date, time, etc. under the control of the control circuit 90. In this electronic camera, the image compression ratio can be set to a desired value by operating a switch 30 provided on the operating section of the electronic camera body 1. That is, a plurality of standard compression ratio information is set in advance in the control circuit 90, and this is determined based on the value of the number of recordable images set by operating the switch 30. The compression rate to be applied is determined from the capacity of the medium (medium), and the determined compression rate value and the number of images that can be recorded on the memory card are converted and displayed on the LCD display 48 of the operation unit. . Then, when the user presses the switch 30, the control circuit 90 changes these values each time the switch 30 is pressed.

When the user stops pressing the switch 30 at the desired value while looking at the displayed change value, the control circuit 90 sets the command compression rate corresponding to the command value for the number of images that can be taken at that time. It has become. This is done by the control circuit 90 determining the standard total code amount per image determined according to the compression rate, and providing this to the encoding circuit 80 as target code amount setting information. Also, when the shutter operation button 50, which is a trigger switch, is pressed,
When the shutter function is activated, a subject image is formed on the image sensor 40b, and a charge image is accumulated in the image sensor 40b corresponding to this image. Can you get it? These controls are also controlled by the control circuit 90.

The imaging system 40 in FIG. 1 includes a photographic lens 40a and a CC
It has an image pickup device 40b made of an image pickup device such as D, and converts an optical image formed on the image pickup device 40b by the photographic lens 40a into an image signal and outputs it to the signal processing circuit 60. The signal processing circuit 60 includes an amplifier Boa,
It includes an A/D converter 60b, a buffer memory 60c, and a process circuit 60d, and the process circuit BOd converts the image signal obtained by the image sensor 40b into color signals Y and RY (hereinafter, 1?-Y is referred to as Cr). (abbreviated as Chroma Red)), B-Y (hereinafter, this B-
In addition to separating Y into each color component (abbreviated as Cb (chroma blue)), gamma correction, white balance processing, etc. are performed.

The output video signal of the imaging system 40 that has been digitally converted by the ^/D converter 60b is stored as image data in a buffer memory 60c having a capacity for one frame, for example.
By being read out and applied to the process circuit 60d, the Y component of the luminance signal system and the Cr and Cb acid components of the chroma (C1 color difference signal) system are separated. The image data stored in the buffer memory 60c is processed by a process circuit to obtain Y component data of the image signal, for example, in order to first perform statistical processing on the luminance signal.
This is supplied to the encoding circuit 80 to perform encoding processing on the Y component data, and when this processing is completed, next processing is performed on the chroma system Cr5Cb component data, and then encoding processing is performed.

The signal processing circuit 60 has a blocking function, and image data (1
It is possible to perform a blocking process in which one frame (or one field) is divided into blocks of a predetermined size. Here, as an example, the block size is 8×8, but this block size is not limited to 8×81, and the block size may be different for Y and C (chroma system).

In this embodiment, luminance system Y data is read out, divided into blocks, and given to the subsequent processing system to perform statistical processing on this Y component data.Once the statistical processing is completed, next chroma system C ``In order to start statistical processing of the cb acid component data, we begin reading and blocking data of the chroma-based Cr5Cb component.

In the chroma system blocking, all of the Cr component image data is first blocked, and then the CB acid component image data is blocked.

The encoding circuit 80 has a configuration shown in FIG. Second
In the figure, reference numeral 4 denotes an orthogonal transformation circuit, which receives input image data in blocks and performs two-dimensional orthogonal transformation on each block of this image data. As the orthogonal transformation, cosine transformation, sine transformation, Fourier transformation, Hadamard transformation, etc. can be used. By performing orthogonal transformation, image data as transformation coefficients can be obtained. Since the image data as the transform coefficient is orthogonally transformed, it is data obtained by decomposing the spatial frequency of the image into each frequency component.

6 is a quantization circuit, which receives the image data (transform coefficients) output from the orthogonal transform circuit 4, and in the first quantization, quantization width for each frequency component is set in advance according to each color component. The transform coefficients are quantized using the quantization width corrected by multiplying by the quantization coefficient α set in advance according to the shooting mode, and in the second time, the optimal quantization coefficient α determined by the previous processing is quantized. This is a configuration in which quantization is performed using

8 is a variable length encoding circuit, and the variable length encoding circuit 8 subjects the quantized output output from the quantization circuit 6 to variable length encoding. Huffman coding is used as variable length coding,
Use arithmetic encoding, etc. In variable length coding, the amount of code for each block, the amount of code for the entire image, etc. change for each image. Although the type of variable length encoding used is not directly related to the present invention, an example using Huffman encoding will be shown here.

The variable length encoding circuit 8 scans the input quantized transform coefficients from low frequency components to high frequency components by a method called zigzag scan in which the input quantized transform coefficients are scanned in the order shown in FIG.

The data of the first DC component [DC] in the scanning order in FIG. 7 is output by Huffman encoding the difference value between the data and the DC component of the block that has been subjected to variable length encoding immediately before. AC component [
AC], look at the conversion coefficients in order from the 2nd to the 64th in the scanning order in Figure 7, and if a non-zero (i.e., valid) coefficient appears, it is the same as the one that existed immediately before it. The operation is such that two-dimensional Huffman encoding is performed using the number of 0 (invalid) coefficients (zero run) and the value of its effective coefficients and output.

Furthermore, if invalid coefficients continue after a certain coefficient up to the 64th coefficient, an EOB (end of block) code indicating the end of the block is output. Furthermore, when a truncation signal is input, encoding is terminated, and an EOB is added and output. Then, the code length generated for each code is output to the code amount calculation circuit 14.

The code amount calculation circuit 14 integrates the code length for each code of each input YlCrsCb component, and calculates Y, Cr, cb.
The code amount of each component is calculated, and the data of the code amount of the entire image is output to the quantization width prediction circuit 12, and the code amount of each color component and the code amount of the entire image are output to the code amount allocation circuit 20. This is a configuration that outputs to .

At the start of the first pass, the quantization width prediction circuit 12 receives information on the target code amount from the control circuit 18, and uses this code amount information to calculate log(BRy + BR,) based on the equation (4) described earlier. 2 a X IogS
P+b However, BR is the code amount (number of bits per pixel)
, sp is a quantization coefficient, and a and b are constants.

The initial value of the quantization coefficient α is set using the relationship shown in FIG. ,
From the target total code amount, which is the maximum allowable data amount per image, for example, using the relationship in equation (1), calculate the optimal quantization coefficient α to approach the target total code amount by linear prediction.
is predicted by taking into account the quantization coefficients actually used this time.

Further, the quantization width prediction circuit 12 determines the optimal quantization coefficient a,
The order of the color components to be encoded is determined by comparison with the quantization coefficient α used in the first pass, and is output to the control circuit 16.

Here, how to set the quantization coefficient to an optimal value is
Since this is an important issue, I will explain this point a little.

It is well known that when image data is preprocessed, this output is quantized, and this quantized output is variable-length coded, the amount of code generated changes when the quantization width of this quantization is changed. . This is because variable length coding, typified by Huffman coding, uses the bias in the probability of occurrence of data to be encoded to reduce the amount of code required to represent that data. Since the above-mentioned "changing the quantization width" also means changing the probability of occurrence of a quantized value, it can be seen that by changing the quantization width, the generated code amount also changes.

By the way, even if the same encoding is performed with the same quantization width, the amount of generated code will differ depending on the image data at that time. However, when the same encoding is performed on one image data by changing the quantization width, a certain relationship is obtained between the quantization width and the amount of generated code. Furthermore, it has become clear that when the relationship between the quantization width and the amount of generated code is determined for a large amount of image data, the relationship with the highest frequency of occurrence can be statistically obtained.

Specifically, in many cases, the following relationships were obtained.

In other words, the relative ratio to a certain quantization width is SF, and the amount of generated code is the number of bits per pixel (bit rate).
When this is expressed as BR, the relationship of the above equation (1) holds true. In equation (1), if the encoding is the same, a is approximately constant regardless of the image, and b depends on the image. The value of b has a certain distribution depending on the image, and a representative value can be obtained from this distribution of frequency of occurrence.

Therefore, the optimal quantization coefficient can be found from the relationship in equation (1).

The code amount allocation circuit 20 calculates the allocated code amount per block for each color component based on the code amount of the image data for each color component inputted from the code amount calculation circuit 14, the code amount of the entire image, and the target edge code amount. It is calculated and output to the encoding abort circuit I6.

The calculation method here is, for example, to proportionately allocate the target edge code amount based on the ratio of the code amounts for each block.

For example, by multiplying the code amount of a certain block by the target edge code amount and dividing it by the code amount of the entire image, the allocated code amount of the block is determined.

As a result, the amount of allocated code for each block is reduced depending on the actual amount of code in that block, and if the amount of code is small, it is suppressed to the extent that it is enough to make it in time, and for blocks with a large amount of code, it is increased accordingly. Assigned.

The code amount allocation circuit 20 has a code amount information table and a block allocation code amount data table, and rewrites the code amount information of the corresponding block position in the code amount information table with the code amount information input from the code amount calculation circuit 14. , the standard allocation code amount for each block is calculated from the code amount for each block and the code amount for the entire image input from the code rotation 8 circuit 14, and the target edge code amount, and the calculated standard allocation code for each block is calculated. The code amount data is stored in the block allocation code amount data table. The standard allocation code amount for each block in this block allocation code it data table is given to the coding abort circuit 16 when the corresponding block is subjected to variable length coding processing.

The encoding abort circuit 16 adds an excess/deficiency amount to the standard allocated code amount of the corresponding block from the code amount allocation circuit 20, which is the difference between the generated code amount and the allocated code amount in the block processed one block before this block. is added as a carryover from the previous block to determine the allocated code amount for this block, and the code length of each block from the code amount allocation circuit 20 is subtracted from the allocated code amount to calculate the remaining allocated code amount. , when the amount of codes to be transmitted and the EOB code become smaller than the total code amount, an abort signal is output and the variable length encoding circuit 8
It has a function to complete the encoding of the block, subtract the transmitted code amount from the allocated code amount of the block, and hold that value as the remainder of the allocated code amount.

Therefore, the encoding abort circuit 16 refers to this allocated code amount, and if the input code amount to be transmitted and the EOB code do not exceed the allocated code amount even if the EOB code is transmitted, no abort is performed and the block is After the encoding is finished, the amount of code to be sent is subtracted from the allocated code amount of the block, and this value is held as the remainder of the allocated code amount.

In addition, the encoding abort circuit 16 refers to this allocated code amount, and if the allocated code amount is not sufficient to send out the input DC component code and EOB code, these two codes are After sending out the block, the coding of that block is finished, and the sent code amount is subtracted from the allocated code amount of the block. That is, the remainder of the allocated code amount is held as a negative value.

10 is a code output circuit, and this code output circuit IO connects the variable length codes inputted from the variable length encoding circuit 8, and stores the connected codes in a recording medium such as a memory card. It functions to write to the recording system 22 that is stored in the memory.

This system first performs statistical processing using the initial standard quantization coefficient α determined according to the shooting mode (first
bus), examine the amount of information for each block and the amount of information for the entire image required for optimization, determine the order in which each color component is encoded, and then optimize based on the information obtained through this statistical processing. Then, processing for performing the encoded data is started (second pass).

Therefore, we first block the image, quantize the elements of this blocked image using a standard quantization coefficient α, variable-length encoding the transform coefficients obtained by quantization, and then Prediction of the coding coefficient α necessary to obtain the optimal code amount from the code amount information of each element of each block obtained by long encoding and the code amount information of the entire image, determination of the coding order of each color component, Determination of the standard allocated code amount for each element of a block, transition to the processing mode of optimal encoding for the image to be processed based on these, blocking processing of the image in implementing this processing mode, elements of this blocked image quantization processing using the predicted quantization coefficient α, variable-length encoding of the transform coefficients obtained by this quantization, and output processing to save all codes of the image to be processed. However, the overall control management is assumed to be performed by the control circuit 18 in the figure.

Incidentally, such a function of the control circuit 18 can be easily realized by using a microprocessor (MPU). In addition, the order of coding of each color and component is determined so that the color component with the least amount of code is encoded first. The aim is to increase the amount of allocated code that can be allocated to color components with a large amount of code.

The above is the configuration of the encoding circuit 80.

The recording system 70 in FIG. 1 is an interface circuit 70a.
There is a recording medium 71 that is detachably connected to this.
The image data and quantization width (or information corresponding thereto) encoded and output by the encoding circuit 80 are recorded on the recording medium 71 via the interface circuit 70a.

Next, the operation of the present apparatus having the structure shown in FIGS. 1 and 2 will be described. In order to get an overall overview, the basic operation will first be explained with reference to FIG. 8, which is an operation transition diagram.

When using the camera, the user of the camera operates the switch 30 to set the desired number of images that can be taken. Thereby, the control circuit 90 determines the optimum code amount according to the set number of images that can be photographed, and provides this to the encoding circuit 80 as target code amount setting information. In this way, the number of images that can be taken is set.

When a photograph is taken next, the subject image is formed as an optical image on the image sensor 40b placed behind the photographic lens 40a. The image sensor 40b converts the formed optical image into an image signal and outputs the image signal.

The image signal obtained by the image sensor 40b is input to the signal processing circuit 60, where it is amplified by the amplifier circuit BOa in the signal processing circuit 60, A/D converted by the A/D converter 60b, and temporarily stored in the buffer memory 8Dc. Retained. Thereafter, it is read out from the buffer memory 60c, and subjected to band correction by the process circuit 60d in the signal processing circuit 60.
Processing such as color signal formation is performed.

Here, the subsequent first pass processing is Y (luminance), Cr, Cb
(Chroma system, both are color difference) Since it is performed in the order of the signals, color signal formation is also performed in accordance with this order. That is, the image signal is divided into blocks in an 8×8 matrix and read out, and the process circuit extracts the Y component, Cr component (1?-Y component), and Cb component from this blocked image signal data.
The signals of these color components are separated in the order of acid component (B-Y component), and gamma correction, white balance processing, etc. are performed.

The image signal data of each color component in the 8×8 matrix blocked image signal separated by the process circuit 60d is input to the encoding circuit 80. This results in
Image data for one frame (or one field) is divided into blocks of the predetermined size and sequentially input to the encoding circuit 80. The image signals of each color component processed by the process circuit 80d are Y, Cr,
Each component of Cb may be stored in a buffer memory and read out and used in later processing.

In this embodiment, the signal processing circuit 60 outputs the Y component (luminance component) of the image signal data for one image, and after completing the subsequent processing (statistical processing) for this, All the image data of the components are divided into blocks, which are then subjected to statistical processing at a later stage, and then the cb acid component image is divided into blocks, and which are subjected to statistical processing at a later stage. conduct.

The encoding circuit 80 supplies this input data received from the signal processing circuit 60 to the orthogonal transformation circuit 4. Then, the orthogonal transform circuit 4 performs two-dimensional orthogonal transform using, for example, discrete cosine transform (DCT) on each block of the input image data that has been divided into blocks (hereinafter referred to as block image data). This orthogonal transformation using DCT is a process of dividing a certain waveform into frequency components and expressing them with the same number of cosine waves of different frequencies as the number of input samples.

The block image data (transformation coefficients) subjected to orthogonal transformation are stored at corresponding frequency component positions on an 8x8 matrix in a buffer memory (not shown) (the origin position of the matrix is the DC component, and the other AC components are AC components from the origin position). (Stored in a matrix such that the frequency increases as the distance increases), this is input to the quantization circuit 6.

Then, the quantization circuit 6 performs a first pass (first time) quantization on this block image data (transform coefficients).

In this first quantization, the image quality setting value set by the user at the time of shooting is applied to the quantization matrix for each preset frequency component (frequency components are determined corresponding to each matrix position of the block). The control circuit 18 corresponds to
The transform coefficients are quantized using the quantization width multiplied by the standard (provisional) quantization coefficient α given by (Figure 8 (hl,
i)). The quantization matrix at this time may be the same for both the luminance system and the chroma system, but better results can be obtained by setting quantization matrices suitable for each.

The quantized block image data (transform coefficients) is input to a variable length encoding circuit 8, where it is variable length encoded. The variable length encoding circuit 8 zigzags scans the quantized input transform coefficients in the order shown in FIG. 7, scanning from low frequency components to high frequency components. That is, the conversion coefficients are stored in an 8×8 matrix corresponding to frequency components, and the closer to the origin the lower the frequency, so zigzag scanning allows scanning from low frequency components to high frequency components.

Since the first data in the scanning order in FIG. 7 is the DC component DC, the data of this DC component DC is the DC component D of the block (previous block) that was subjected to variable length encoding immediately before.
Huffman encode the difference value dlf'r-DC with C (
Figure 8 (di), (el)).

Regarding the AC component AC, look at the conversion coefficients in order from the 2nd to the 64th in the scanning order in Figure 7, and if a conversion coefficient that is not 0 (that is, valid) comes out, it is the continuation that existed immediately before it. Two-dimensional Huffman encoding is performed using the number of 0 (invalid) coefficients (zero run) and the values of their effective coefficients ((d2), (e2)).

Further, the variable length encoding circuit 8 provides an EOB (end of block) code indicating the end of the block when invalid coefficients continue after a certain coefficient up to the 64th coefficient. Then, the code length generated for that code is output to the code amount calculation circuit 14 (gl).

Such processing is executed for all blocks of one image.

When such processing for the Y component is completed, the same processing is then performed for each Or%cb component.

On the other hand, the code amount calculation circuit 14 inputs Y% Cr.

In order to calculate the code amount for the entire image for each color component of each cb component, calculate the code amount for each block of each Y, Cr, and Cb component, and integrate the code amount for the entire image ( g2), and outputs the code amount data for each block to the code amount allocation circuit 20. The code amount allocation circuit 20 writes the code amount data for each block as the code amount information of the corresponding block position in the code amount information table. Then, for all blocks of one image, Y, C
Data on the total code amount for each of the r and Cb components is output to the quantization width prediction circuit 12, and data on the code amount for the entire image is output to the code amount allocation circuit 20.

The quantization width prediction circuit 12 actually calculates the optimal quantization coefficient α for approaching the value of the target total code amount by linear prediction, for example, from the input code amount data of the entire image and the target total code amount data. The prediction is made based on the quantization coefficients used in (Fig. 8 (h2)).

Furthermore, the coding order of each color component is determined depending on whether the predicted quantization coefficient is larger than the actually used quantization coefficient, and is output to the control circuit 18. Further, the code amount allocation circuit 20 calculates a standard allocated code amount for each block from the input code amount for each block, the code amount for the entire image, and the target total code amount, for example, by calculating the ratio of the code amount for each block. ,
Calculate by proportionally distributing the total target code amount (see Figure 8 (
h3)).

Specifically, to determine the standard allocated code amount for a certain block, multiply the code amount of the block by the target total code amount, and divide it by the code amount of the entire image. This is the standard allocated code amount in a block.

Then, the calculated standard allocated code amount data for each block is stored in the block allocated code amount data table. The data of the allocated code amount for each block in this block allocated code amount data table is given to the encoding abort circuit 16 when the corresponding block is subjected to variable length encoding processing.

This completes the first pass, that is, the first encoding (statistical processing) for determining the allocated code amount for each block and optimizing the quantization width.

Next, processing for the second bus begins. This second bus process is
It is a process to obtain a final encoded output optimized to fit within the target total code amount.

This process is performed in accordance with the coding order for each color component determined in the first pass. For example, if the determined order is Y, Cr, and Cb, the Y component is processed first, and after the Y component is processed, the Cb is processed.
After the r treatment, the cb acid component is added. If the determined order is Cr, Y, CbO, then the Cr component is processed first, the y component is processed after the Cr component is completed, and the Cb acid component is then processed. It is.

In the processing of the second bus, the image data is first read out in blocks, and the image signal data of the color component to be encoded first, which is extracted and output from the signal processing circuit 60, is input to the encoding circuit 80 ( a). The input blocked image data is input to the orthogonal transformation circuit 4 in the encoding circuit 80, and orthogonal transformation is performed again (b). The transform coefficients obtained by this orthogonal transform are input to the quantization circuit 6 and quantized again (C). However, the quantization coefficient α used at this time is the predicted optimal quantization coefficient α calculated by the quantization width prediction circuit 12 in the previous pass.

Next, the transform coefficients of the quantized block image data are input to the variable length encoding circuit 8. In variable length encoding, as in statistical processing, among the transform coefficients of this block image data, first the difference value difr-DC of the DC component DC is Huffman encoded ((di), (el)), and then the AC component Data is sequentially extracted from AC by zigzag scanning and two-dimensional Huffman encoding is performed ((d2)).

(e2)).

However, each time a Huffman code for one element (one position in the matrix) is generated, the code amount allocation circuit 20 sends the standard allocated code amount to be transmitted for that element stored in the block allocated code amount data table. is output to the encoding terminating circuit 16, while the encoding terminating circuit 16
Now, add the standard allocated code amount for each block and the remainder from the allocated code amount in the encoding process of the previous block to determine the allocated code amount for the block, and also calculate the code amount to be sent and the EOB code. If the allocated code amount is not exceeded, a process is performed to reduce the code amount to be transmitted from the allocated code amount of the block without generating an abort signal.

Then, when the total code amount of the code amount of the block to be transmitted and the EOB code exceeds the remaining code amount of the allocated code amount, the encoding abort circuit 16 sends the variable length encoder 8 to the variable length encoder circuit 8. A termination signal is output, Huffman encoding of the block is finished, and from the allocated code amount of the block,
The transmitted code amount is reduced and the value is held as the remainder of the allocated code amount. The variable length encoding circuit 8 then proceeds to Huffman encoding of the next block obtained from the quantization circuit 6.

In addition, in the encoding abort circuit 16, the DC component and the EOB
If the amount of allocated codes is insufficient to send out the codes, these codes are sent out and then sent to the coding abort circuit 16.
outputs an abort signal to the variable length encoding circuit 8 to terminate the Huffman encoding of the block, and subtracts the transmitted code amount from the allocated code amount of the block and holds the remainder of the allocated code amount as a negative value. do.

Therefore, the variable length encoding circuit 8 outputs the converted Huffman code to the code output circuit lO until the truncation signal is input from the coding truncation circuit 16, and before the truncation signal is generated, the Huffman code for all elements of the matrix is inputted. When the encoding is completed, the variable length encoding circuit 8 outputs the EOB code to the code output circuit 10. Furthermore, if the variable-length encoding circuit 8 receives an abort signal before completing Huffman encoding for all elements of the matrix, it outputs the EOB code to the code output circuit 10 instead of that code. Become. The code output circuit 10 temporarily stores this encoded data.

The variable length encoding circuit 8 then proceeds to Huffman encoding of the next block obtained from the quantization circuit 6.

By repeating such operations and completing processing of all blocks of one screen image, all encoding processing is completed. When such processing is completed for the color component to be encoded first, processing of the next color component in the processing order begins in the same manner. In processing this second color component as well, the quantization circuit 6 uses the predetermined optimal quantization coefficient α calculated by the quantization width prediction circuit 12 in the previous bus. The same applies to the third color component.

In this way, all the encoding processing is completed by completing the second pass processing of all blocks of the image for one screen for all color components.

At the end of this process, the encoder output circuit 10 outputs the optimized Huffman encoded data for one image to the recording system 22, and stores it in a storage medium 7 such as a memory cart in the recording system 22.
1 (n. This is done by the output of the code output circuit 10, or the code output circuit 10 connects the Huffman code, which is a variable length code from the variable length encoding circuit 8, and writes it to the memory, which is the storage medium 71. It is written by giving it to the card.The storage medium 7I is written by the output of this code output circuit IO.
Is it okay to write to the data all at once at the end of the second pass, or is it the result of stringing together variable-length Huffman codes at the stage where the first bus ends and the second bus is executed? It is also possible to sequentially write data to the storage medium in units of one byte or several bytes as soon as they are collected.

Prior to this, the code output circuit IO writes the optimal quantization coefficient α used for encoding and information for identifying the encoding order of each color component into the header part of the stored data of the encoded image. , leave it as a clue during playback.

As described above, in this device, statistical processing is first performed, and through this statistical processing, the predicted value of the optimal quantization width and the statistical amount necessary for determining the standard allocated code amount for each block are obtained, and the code of each color component is obtained. Decide on the order in which to
Encoding processing begins, and according to the determined coding order of each color component, while checking the encoded output sequentially, determine the standard allocated code amount for each block and the excess or deficiency of the output code amount with respect to the allocated code amount of the previous block. The code amount for each block is controlled by terminating the variable length encoding so that the code amount falls within the allocated code amount for that block obtained by combining the two blocks, and the encoded output that falls within the desired code amount is output as the final output. This point is an important point of the present invention.

Therefore, the block size, the type of orthogonal transformation, the type of variable length encoding, etc. used in this embodiment are not limited. Also, statistical processing does not necessarily have to be done only once;
It may be omitted or may be repeated multiple times.

However, performing the statistical processing once is the best option in terms of processing time and effects obtained. In addition, statistical processing does not necessarily require actual encoding to evaluate the generated code amount; instead, the activity is determined for each block, and the standard allocated code amount and quantization coefficient for each block are calculated from the results. It may be any method you request.

In addition, it is not necessarily necessary to allocate the entire target total code amount to each block; for example, if the remaining amount when the target total code amount is allocated to the allocated code amount of each block is used for the first block, the previous processing block It is also possible to give it as an excess or deficiency.

Furthermore, in this embodiment, the EOB code amount was included in the determination of the standard allocated code amount for each block and the code amount control, but the EOB code amount does not change even if the quantization width changes. Of course, there is no problem in determining the standard allocated code amount for each block and controlling the code amount by excluding the EOB code amount in advance, but this is preferable since it improves accuracy. Similarly, in predicting the quantization width, it is preferable to perform prediction using a code amount excluding the EOB code amount.

Furthermore, the compression rate does not need to be variable; it may be fixed to one type of compression rate, and the target total code amount, quantization width, standard allocated code amount per l block, etc. may all be given as fixed values. , in this case, the configuration becomes simpler. Further, the image data buffer memory may be located between the orthogonal transform circuit 4 and the quantization circuit 6, and in this case, the blocking and orthogonal transform processes in the encoding process can be omitted. However, in order to maintain accuracy, the size of the image memory becomes large in this case.

Also, process processing is performed before A/D conversion,
You may digitize it afterwards. In addition, in this device, variable-length encoding is performed for each block starting with low frequency components, and high frequency components, which have relatively little visual impact on image quality, are omitted by aborting the encoding, which improves image quality. This makes it possible to encode with high compression while minimizing deterioration.

The present invention having the configuration shown in FIGS. 1 and 2 described above has the following features:
In short, based on the results of statistical processing, the allocated code is the sum of the standard allocated code amount for each block and the excess or deficiency of the generated code amount in the block before that block with respect to the allocated code amount. Encoding is continued while monitoring the code amount for each block so that the code amount is within the allocated code amount, and when the code amount reaches the allocated code amount, the encoding of that block is terminated or the DC component is replaced with the allocated code. Be sure to encode even if the amount exceeds the amount, and remember the excess or deficiency of the allocated code amount at that time.
In addition, the coding order of each color component in the coding process is determined based on the magnitude of the quantization coefficient predicted based on the result of statistical processing. In the encoding process, each color component is encoded in the determined order.

This means that when encoding using the predicted quantization coefficients,
There are cases where the standard allocated code amount per block is redundant for a certain color component, and the standard allocated code amount per block is insufficient for another color component, but even in such a case, if you consider each color component together, By encoding using the predicted quantization coefficient, even if the code amount for each block is not controlled, the total code amount will be close to the target total code amount, so color components that require an extra code amount will be By performing encoding from 1 to 3 and using the remaining allocated code amount for subsequent encoding, it is possible to compensate for the lack of allocated code amount for color components with insufficient code amount, and both color components , in order to obtain good results.

Therefore, according to the present invention, it becomes possible to encode images with a wide range of spatial frequencies within a certain amount of code within a certain processing time without degrading the image quality.

In compression encoding, the encoding circuit 8o having the configuration shown in FIG. The process is completed by performing a second pass using this optimal quantization width to obtain the final compressed encoded data. This is to find the optimal α.

In FIG. 3, in order to make it easier to understand the processing flow of the encoding circuit 8o, the signal flow in the first path is indicated by a dotted arrow ■, and the signal flow in the second bus is indicated by a solid arrow ■. Each is illustrated. If we briefly follow the operation along the flow of this signal, we will see the following.

When encoding image data, a target total code amount is set in the control circuit 18 of the encoding circuit 8o.

By operating the switch 3o, the user sets the desired number of shots that can be taken, and the control circuit 90 selects the optimum code amount according to the set number of shots, and uses this as information on the target total code amount. This is realized by giving the code to the encoding circuit 80 as follows.

Note that in the initial state, the number of images that can be taken is set to a predetermined standard number.

When photographing is performed, an image signal is output from the image sensor in the imaging system 40. This output image signal is converted into a digital signal in the signal processing circuit 60, stored in a buffer memory, and then read out in blocks of 8x8 pixels, starting with the Y component, then the Cr component, and then the Cb component.
The acid component is separated.

This separation is first performed on the Y component, and the image data of the Y component is output in blocks of 8 x 8 pixels. Conversion (Discrete
Co51ne Transform) is performed.

The DCT transform coefficients obtained by the orthogonal transform circuit 4 are input to the quantization circuit 6, and on the other hand, the target total code amount is applied from the control circuit 18 to the quantization width prediction circuit 12.
2, the initial value of the quantization coefficient a is set from the target total code amount using the relationship of equation (1), and is output to the quantization circuit 6. The quantization circuit 6 linearly quantizes the transform coefficients using the manually generated quantization coefficient α. The quantized transform coefficients are input to the variable length encoding circuit 8 and are variable length encoded (in this example).
\Human encoding) is performed.

The quantization coefficients input here are scanned from low frequency components to high frequency components called zigzag scan, and the data of the first DC component is the DC component of the block that was variable-length encoded immediately before. The difference value is Huffman encoded and output.

For the AC component, look at the conversion coefficients in order from the 2nd to the 64th in the scanning order, and when a conversion coefficient or a non-zero (i.e., valid) coefficient appears, it is the consecutive 0 (zero) that existed immediately before it. Two-dimensional Huffman encoding is performed using the values of the number of coefficients (invalid) (celloran) and their effective coefficients. In addition, if invalid output continues after a certain coefficient up to the 64th coefficient, an EOB indicating the end of the block is output.
Outputs the sign of .

The variable length encoding circuit 8 performs encoding as described above,
Every time one code is generated, the code length is output to the code amount calculation circuit 14.

The code amount calculation circuit 14 accumulates and stores the manually input code lengths for each color component.

After completing this processing for the Y component, next
Similar treatment is performed for the r component and the Cb acid component.

When the encoding of one image is completed, the code amount calculation circuit 14 adds the accumulated code amounts for each color component and calculates the code amount of the entire image as a total code amount value. This total code amount value is applied to the quantization width prediction circuit I2, and is also output to the code amount allocation circuit 2G for each color component and the code amount for the entire image.

When the above-described first pass encoding processing is completed, the code amount allocation circuit 20 calculates the code amount from the code amount for each color component inputted from the code amount calculation circuit 14, the code amount for the entire image, the target code amount, and the number of blocks. The allocated code amount per block for each color component is calculated. Also, in the quantization width prediction circuit 12, the first
A more suitable quantization coefficient α is predicted from the picture image code amount obtained by encoding on the bus and the target total code amount given from the control circuit 18, and is output to the quantization circuit 6. Furthermore, the quantization width prediction circuit 12 determines the coding order of each color component by comparing the magnitudes of the quantization coefficients used in the first bus and the predicted quantization coefficients, and performs control. Compared to circuit 18.

Subsequently, the same image data is subjected to encoding processing on the second bus. On the second bus, the image data read from the memory in the signal processing circuit 60 is separated into color components in the order determined in the first pass, and the image data of each component undergoes processing such as 8x8 pixel blocks. After the conversion, the DC data obtained by the orthogonal transform circuit 4 is inputted to the orthogonal transform circuit 4, and is orthogonally transformed (DCT transform) for each block.
The T transform coefficients are input to the quantization circuit 6.

On the other hand, the quantization circuit 6 linearly quantizes the DCT transform coefficients using the corrected quantization width based on the new quantization coefficient α given by this prediction. The quantized coefficients are input to the variable length encoding circuit 8 and Huffman encoded in the same manner as in the first pass encoding. Here, the amount of code generated during encoding is obtained at the end of the first pass, and is calculated based on the standard allocated code amount of each block stored in the code amount allocation circuit 20 and the excess or deficiency of the allocated code amount in the previous block. A comparison is made with the added allocated code amount of the block, and if this is exceeded, the code abort circuit 16 works to abort subsequent encoding within that block. Also,
Excess/deficiency of the allocated code amount at the time when the encoding of the block is finished is stored in the code amount allocation circuit 20.

The encoded data controlled to the target total code amount by the above method is sequentially outputted to the recording system 70 via the code output circuit 10 and recorded.

Next, reproduction of compressed and encoded recorded image data recorded on the recording medium 71 by the recording system 70 will be explained.

Figure 4 shows the configuration of the player. In the figure, 100 is a main body of the playback machine, and this main body 100 of the playback machine includes a reading section 102.
, a decoding circuit 104, a processing circuit 10B, and a control circuit 10g. The reading unit 102 can attach and detach the storage medium 71, and the reading unit 102 can attach and detach the storage medium 71. The contents of the ff body 71p are read out via the interface circuit 110.

The decoding circuit 104 has functional blocks as shown in FIG. That is, 112 is a Huffman decoding unit that decodes Huffman encoded data, and 114 is a Huffman decoding unit that decodes the data obtained by Huffman decoding based on the quantization width information read from the storage medium 71 and set and input. The inverse quantization unit 11B performs quantization, and the IDC performs inverse DCT transformation on the data obtained by inverse quantization and converts it into video signal data.
The T (inverse DCT transform) section and the IHI are control sections that control these.

The processing circuit 106 includes a buffer memory 120 and an encoder 1.
22 and a D/A converter 124. The buffer memory 120 is a memory that temporarily holds the video signal data output from the decoding circuit 104, and the encoder 122 converts the video signal data read from the buffer memory 120 into an NTSC video signal.
The D/A converter 124 converts this NTSC video signal into analog and outputs it as a television video signal.

The control circuit 108 is in charge of overall control of the player main body 100, and identifies information on the quantization width at the time of encoding and the coding order of each color component to the reading unit 102 of the player main body 100. As a result, the dequantization unit 114 of the decoding circuit 104 sets the information of the quantization width at the time of encoding read from the recording medium 71, and then the control circuit Reference numeral 108 performs control such as controlling the reading unit 102 so as to read the compression-encoded video signal data from the information recording medium 71 in the order in which the read color components are encoded. Further, although not shown, the playback main body 100 includes a frame advance switch and the like, and the video at the frame position specified by this switch can be played back. Such control is also performed by the control circuit 10g.

Next, the operation of the reproducing machine having the above configuration will be explained. When the recording medium (memory card) 71 on which compression-encoded video signal data is recorded is attached to the reading section 102 of the playback main body 100, the control circuit 10g first sends the following information to the reading section 102.
Control is performed to read out information on quantization width during encoding. As a result, information on the quantization width at the time of encoding is read out from the recording medium 71 in the reading unit 102, and this information is set in the dequantization unit 114 of the decoding circuit 104. Next, the control circuit 108 reads out the video signal from the recording medium 71.
Since the reading unit 102 is controlled, the reading unit 102 reads the recording medium 7! Video signals are sequentially read out from the decoding circuit 104 and input to the decoding circuit 104.

The decoding circuit 104 that receives this inputs the Huffman decoding unit 1.
12, the Huffman code is decoded to obtain quantized coefficients. The quantized coefficients obtained in this way are supplied to an inverse quantization circuit 114 for inverse quantization. The inverse quantization here is performed using the information on the quantization width set previously.

The transform coefficients obtained by inverse quantization are transferred to the IDOT unit 11.
In B, each block is subjected to inverse DCT transformation and restored to the original video signal. In this way, the video signal is restored in the order of each color component set previously and output from the decoding circuit 104, and the buffer memory 12 in the processing circuit 10 [i
Written to 0. When writing of the video signal data for one screen is completed, the video signal data is read out from the buffer memory 120 in the normal scanning order of the television signal, and is converted into an NTSC video signal by the encoder 122. Furthermore, it is converted into an analog signal by the D/^ converter 124 and output. By inputting this video signal to a TV monitor, the image can be played back as a TV video and viewed as a video.Also, by feeding it to a printing device such as a video printer and printing it, a hard copy can be obtained, so it can be used as a photo, etc. You will be able to appreciate it in a similar way.

As explained above, the camera can set the desired number of shots that can be taken, and by setting the number of shots that can be taken, the camera automatically sets the compression rate corresponding to this, and the temporary Using a quantization width of The captured image data for one screen is quantized and variable-length encoded using the predicted optimal quantization width, and when the encoded video signal is played back, it is used at the time of shooting. By decoding at the desired compression rate, encoding at the desired compression rate can be realized with one common hardware, without having to install hardware on the compression rate side.
: Decoding of image data can be realized with one common hardware without installing hardware on the compression ratio side.

In the embodiment, during the encoding process, two buses, the first bus and the second bus,
Although the two-pass method is used, the method is not limited to this, and even better results can be obtained by repeating the first bus several more times. Further, although an example is shown in which a memory card is used as the recording medium, other media such as a floppy disk, an optical disk, and a magnetic tape may also be used. Further, although the camera and the playback device are shown as separate bodies, the camera may be an integrated type that also has the functions of the playback device. Furthermore, in the embodiment, the quantization width value itself is recorded on the recording medium, but the quantization width value may be converted or encoded and then recorded.

In the above embodiment, the quantization width is set according to the target edge code amount, but in applications where multiple target edge codes are used by switching between modes, the quantization width corresponding to each mote can be set. Of course, it is also possible to prepare it in advance and use it by switching it depending on the mode.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope of the gist, and the present invention is applicable not only to still images but also to moving images, etc. , which can be applied to compression encoding of various images.

In addition, in the above embodiment, information on a total code of 2 is given from the compression rate correspondence information, a quantization coefficient that can give a quantization width corresponding to this total code amount is predicted, and this child DI quantization coefficient is Quantization is performed using a quantization width based on the compression rate correspondence information, but the relationship between the quantization width and the compression rate correspondence information is calculated in advance and created in a table. This is stored in memory etc., and the compression rate correspondence information is It is also possible to directly output the quantization width information (that is, the quantization coefficient or the quantization width value). In this way, when information corresponding to the desired compression ratio is input, information on the quantization width that is uniquely determined according to the input compression ratio information can be read and output, and the optimal Immediately after setting the quantization width, the quantization circuit can quantize the image signal data using this quantization width.

According to this configuration, information on the optimal quantization width corresponding to various compression ratios is stored in advance in a memory, etc., and the information on the optimal quantization width can be obtained by simply reading out the information in accordance with the input compression ratio correspondence information. Therefore, when encoding to fit within the target edge code amount, the processing can be done in an extremely short time and the hardware can be simple.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to control the amount of code for images with a wide range of spatial frequencies without degrading the image quality, and to encode images within a certain amount of code within a certain processing time. Accordingly, it is possible to provide an image data encoding device and encoding method that are suitable for electronic camera systems and the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a block diagram showing an example of the main part configuration of the device of the present invention, FIG. 3 is a block diagram for explaining the flow of operation of the circuit shown in FIG. 2, and FIGS. 4 and 5 are block diagrams showing the configuration of the regenerator. 6 is a perspective view showing the external appearance of the electronic camera body according to the present invention, FIG. 7 is a diagram for explaining zig-sag scanning of a block divided into 8×8 pixels, and FIG. 8 is a diagram showing the principle of the present invention. FIG. 9 is an operation transition diagram for explaining the conventional technique, and FIG. 10 is a diagram for explaining the relationship between code amount and quantization width. 1... Electronic camera body, 6... Quantization circuit, 8...
Variable length encoding circuit, 10... Code output circuit, 12...
・Quantization width prediction circuit, 14... code amount calculation circuit, 16
... Encoding abort circuit, 18.18a... Control circuit,
20... Code amount allocation circuit, 24... DCPM circuit,
30...Switch, 40...Imaging system, 48...LC
D display, 60...signal processing circuit, 80...encoding circuit, 70...recording system, 71...recording medium, 9o...control circuit, 100...player main body, 102...reading section ,1
04...Decoding circuit, 106...Processing circuit, 108...
・Control circuit, 110 ・・Interface circuit, 112 ・
... Huffman decoding section, 114... Inverse quantization section, 11B.
...IDCT (inverse DCT transformation) unit, 118 - Control unit. Applicant's agent Patent attorney Jun Tsuboi Diagram 6 Danryu component Komi Sajiri Bunsha 7 Diagram 095F Quantized Buddhism Diagram 10

Claims (15)

[Claims] (1) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , Of the blocks, calculate the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of code allocated to the processed block. a code amount allocation means that adds the allocated code amount of the processing target block and allocates the allocated code amount as the allocated code amount in the processing target block; coding aborting means for aborting the variable length encoding so as not to exceed the code amount; and encoding the color image data according to the code amount predicted value for each color component when quantizing with the optimum quantization width. a code order determining means for determining a processing order for each color component in processing; and a code order determining means for performing encoding processing on the color image data of color components having higher ranks according to the order of color components to be processed determined by the code order determining means. 1. An image data encoding device comprising: a control means for controlling the image data. (2) Claim (1) characterized in that the code order determining means gives a higher processing order to a color component with a small amount of codes.
The image data encoding device described above. (3) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , Of the blocks, calculate the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of code allocated to the processed block. a code amount allocation means that adds the allocated code amount of the processing target block and allocates the allocated code amount as the allocated code amount in the processing target block; encoding terminating means for terminating the variable length encoding so as not to exceed the code amount; encoding output means for outputting the transform coefficients variable length encoded by the variable length encoding means as codes; and the optimal quantum code order determining means for determining a processing order for each color component in encoding processing of the color image data according to a code amount prediction value for each color component when quantizing with a quantization width; and a code order determining means determined by the code order determining means. 1. A control means for controlling the color image data of color components having a higher rank to be encoded in accordance with the rank of color components to be processed. (4) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , Of the blocks, calculate the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of code allocated to the processed block. a code amount allocation means that adds the allocated code amount of the processing target block and allocates the allocated code amount as the allocated code amount in the processing target block; encoding aborting means for aborting the variable length encoding so as not to exceed the code amount; and processing for each color component in the encoding process of the color image data based on the tentatively determined quantization width and the optimal quantization width. A code order determining means for determining the order, and a control means for controlling the color image data of the color component having a higher order to be subjected to encoding processing according to the order of the color components to be processed determined by the code order determining means. An image data encoding device characterized in that: (5) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , a code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing; and the code amount of the entire image calculated by the code amount calculation means. Quantization width prediction that predicts an optimal quantization width to be used in the encoding process from the target code amount to be stored and the provisional quantization width, and provides the predicted optimal quantization width to the quantization means. means; during encoding processing, the amount of code generated by encoding in a processed block that is processed before the block to be processed next to be coded among the blocks and the amount of code allocated to the processed block; and a code amount allocation means which calculates the difference between the two and adds this to the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block, and at the time of encoding processing, coding aborting means for aborting the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding; and each color component when quantizing at the optimum quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data according to another code amount prediction value; and a control means for controlling the color image data having a high color component to be subjected to encoding processing. (6) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. an encoding device that quantizes the transform output for each block, controls the code amount for each block according to the allocated code amount for each block, and then sequentially encodes the quantized output with variable length coding; A code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing, and a code amount of the entire image calculated by the code amount calculation means. A quantization width that predicts an optimal quantization width to be used in the encoding process from the target code amount to be accommodated and the provisional quantization width, and gives the predicted optimal quantization width to the quantization means. a prediction means; during encoding processing, the amount of code generated by encoding in a processed block processed before a block to be processed next to be coded among the blocks and the assigned code in the processed block; a code amount allocating means that calculates the difference between the amount of code and the allocated code amount of the block to be processed, adds this to the allocated code amount of the block to be processed, and allocates the difference as the allocated code amount of the block to be processed; coding aborting means for aborting the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means when encoding; and the provisionally determined quantization width and optimal quantization. code order determining means for determining the processing order of each color component in the encoding process of the color image data based on the width; and according to the order of color components to be processed determined by the code order determining means, 1. An image data encoding device comprising: a control means for controlling color image data to be encoded. (7) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , a code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing; and the code amount of the entire image calculated by the code amount calculation means. Quantization width prediction for predicting an optimal quantization width to be used in the encoding process from the target code amount to be stored and the provisional quantization width, and providing the predicted optimal quantization width to the quantization means. means; during encoding processing, the amount of code generated by encoding in a processed block that is processed before the block to be processed next to be coded among the blocks and the amount of code allocated to the processed block; and a code amount allocation means which calculates the difference between the two and adds this to the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block, and at the time of encoding processing, coding aborting means for aborting the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding; and each color component when quantizing at the optimum quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data according to another code amount prediction value; and a control means for controlling the color image data having a high color component to be subjected to encoding processing. (8) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , a code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing; and the code amount of the entire image calculated by the code amount calculation means. Quantization width prediction that predicts an optimal quantization width to be used in the encoding process from the target code amount to be stored and the provisional quantization width, and provides the predicted optimal quantization width to the quantization means. means; during encoding processing, the amount of code generated by encoding in a processed block that is processed before the block to be processed next to be coded among the blocks and the amount of code allocated to the processed block; and a code amount allocation means which calculates the difference between the two and adds this to the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block, and at the time of encoding processing, coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding; and the provisionally determined quantization width and optimal quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data; 1. An image data encoding apparatus comprising: a control means for controlling image data to perform encoding processing. (9) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , a code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing; and the code amount of the entire image calculated by the code amount calculation means. Quantization width prediction that predicts an optimal quantization width to be used in the encoding process from the target code amount to be stored and the provisional quantization width, and provides the predicted optimal quantization width to the quantization means. means; during encoding processing, the amount of code generated by encoding in a processed block that is processed before the block to be processed next to be coded among the blocks and the amount of code allocated to the processed block; and a code amount allocation means which calculates the difference between the two and adds this to the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block, and at the time of encoding processing, coding aborting means for aborting the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding; and each color component when quantizing at the optimum quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data according to another code amount prediction value; control means for controlling the encoding process to be performed from the color image data having a high color component; a DC component encoding processing unit that obtains a difference from the DC component in the previous processing block and variable-length encoding this difference; and after the encoding processing unit finishes processing the DC component, the AC component An encoding device for image data, comprising: an encoding processing section for alternating current components that performs variable-length encoding for the alternating current components, and wherein the encoding aborting means is provided only in the encoding processing section for alternating current components. (10) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , a code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the variable-length encoded transform coefficients in the statistical processing; and the code amount of the entire image calculated by the code amount calculation means. Quantization width prediction that predicts an optimal quantization width to be used in the encoding process from the target code amount to be stored and the provisional quantization width, and provides the predicted optimal quantization width to the quantization means. means; during encoding processing, the amount of code generated by encoding in a processed block that is processed before the block to be processed next to be coded among the blocks and the amount of code allocated to the processed block; and a code amount allocation means which calculates the difference between the two and adds this to the allocated code amount of the processing target block and allocates it as the allocated code amount of the processing target block, and at the time of encoding processing, coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the code amount allocating means during encoding; and the provisionally determined quantization width and optimal quantization width. code order determining means for determining the processing order for each color component in the encoding process of the color image data; and a control means for controlling the image data to be encoded, and the variable length encoding means controls the DC component of the image data in units of blocks obtained by the orthogonal transformation from the DC component in the previous processing block. an encoding processing unit for a DC component that obtains a difference between the DC component and variable-length encoding the difference; and an AC component that performs variable-length encoding of the AC component after the encoding processing unit finishes processing the DC component. 1. An image data encoding device comprising: a component encoding processing section; and the encoding aborting means is provided only in the alternating current component encoding processing section. (11) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , compression rate selection means for selecting a target compression rate and determining the target code amount to be accommodated according to the selected compression rate and the provisional quantization width; code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the converted coefficients; quantization width prediction means for predicting an optimal quantization width to be used in the encoding process from the quantization width of the target quantization width, and providing the predicted optimal quantization width to the quantization unit; Among the blocks, the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of allocated code in the processed block is calculated and compared with the above processing. a code amount allocation means which adds the allocated code amount of the target block and allocates the allocated code amount as the allocated code amount in the processing target block; and a code amount allocation means when encoding the processing target block during encoding processing; a coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the color coder; code order determining means for determining the processing order for each color component in the encoding process of image data; 1. An image data encoding device comprising: a control means for controlling encoding processing. (12) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , compression rate selection means for selecting a target compression rate and determining the target code amount to be accommodated according to the selected compression rate and the provisional quantization width; code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the converted coefficients; quantization width prediction means for predicting an optimum quantization width to be used in the encoding process from the quantization width, and providing the predicted optimum quantization width to the quantization means; Among the blocks, the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of allocated code in the processed block is calculated and compared with the above processing. a code amount allocation means which adds the allocated code amount of the target block and allocates the allocated code amount as the allocated code amount in the processing target block; and a code amount allocation means when encoding the processing target block during encoding processing; coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the method; A code order determining means for determining a processing order for each color component, and control so that the color image data of a color component having a higher rank is subjected to encoding processing according to the order of color components to be processed determined by the code order determining means. 1. An image data encoding device comprising: a control means. (13) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , compression rate selection means for selecting a target compression rate and determining the target code amount to be accommodated according to the selected compression rate and the provisional quantization width; code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the converted coefficients; quantization width prediction means for predicting an optimum quantization width to be used in the encoding process from the quantization width, and providing the predicted optimum quantization width to the quantization means; Among the blocks, the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of allocated code in the processed block is calculated and compared with the above processing. a code amount allocation means which adds the allocated code amount of the target block and allocates the allocated code amount as the allocated code amount in the processing target block; and a code amount allocation means when encoding the processing target block during encoding processing; a coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the color coder; code order determining means for determining the processing order for each color component in the encoding process of image data; and a control means for controlling the encoding process, and the variable length encoding means is configured to differentiate the DC component from the DC component in the previous processing block among the image data for each block obtained by the orthogonal transformation. a DC component encoding processing section that obtains a difference and variable-length encoding the difference; and an AC component encoding processing section that performs variable-length encoding on the AC component after the encoding processing section finishes processing the DC component. 1. An image data encoding device comprising: an encoding processing section, and the encoding aborting means is provided only in the alternating current component encoding processing section. (14) Divide each of the color image data separated by color component into blocks, perform orthogonal transformation for each divided block by color component, and then quantize the transform output by a quantization means. The quantized output is given to a variable-length encoding means to be variable-length encoded, and when data is encoded, it is first quantized with a provisionally determined quantization width and variable-length encoded, and the code for each block is Then, from the code amount for each block obtained by this statistical processing, the optimal quantization width and the allocated code amount for each block are determined, and each block is divided according to the determined optimal quantization width. In an encoding device that performs encoding processing of quantizing the transform output for each block and sequentially variable-length encoding the quantized output while controlling the code amount for each block according to the allocated code amount for each block. , compression rate selection means for selecting a target compression rate and determining the target code amount to be accommodated according to the selected compression rate and the provisional quantization width; code amount calculation means for calculating the code amount of the entire image and the code amount for each block of the converted coefficients; quantization width prediction means for predicting an optimum quantization width to be used in the encoding process from the quantization width, and providing the predicted optimum quantization width to the quantization means; Among the blocks, the difference between the amount of code generated by encoding in the processed block processed before the block to be encoded next and the amount of allocated code in the processed block is calculated and compared with the above processing. a code amount allocation means which adds the allocated code amount of the target block and allocates the allocated code amount as the allocated code amount in the processing target block; and a code amount allocation means when encoding the processing target block during encoding processing; coding aborting means for aborting the variable length coding so as not to exceed the allocated code amount allocated by the method; A code order determining means for determining a processing order for each color component, and control so that the color image data of a color component having a higher rank is subjected to encoding processing according to the order of color components to be processed determined by the code order determining means. control means, the variable length encoding means obtains a difference between the DC component in the previous processing block and the DC component of the image data for each block obtained by the orthogonal transformation, and calculates this difference. An encoding processing unit for a DC component that performs variable length encoding, and an encoding processing unit for AC component that performs variable length encoding for the AC component after the encoding processing unit finishes processing the DC component. . An image data encoding device, wherein the encoding aborting means is provided only in an encoding processing section for alternating current components. (15) Divide the color image data separated by color component into blocks, perform orthogonal transformation for each divided block, and then quantize the transformation output by a quantization means,
After that, this quantized output is given to variable length encoding means to perform variable length encoding, and when encoding data, each block is assigned a code amount according to the allocated code amount for each block determined from the statistics for each block determined in advance. When performing variable length encoding while controlling the amount of code for each block, the quantization is performed using a provisional quantization width, and the resulting quantized output is encoded and optimized. The first step is to investigate the amount of code required for the entire image and the amount of code for each block, and the quantization width required for optimization is predicted from the amount of code for the entire image obtained in this first step. , a second step of determining the coding order of each color component from the predicted quantization width; a third step of determining a standard allocated code amount for each block from the code amount of each block; A fourth step of performing the quantization for each block using the quantization width, and converting the quantization output for each block in this fourth step into a variable length code within the allocated code amount for the block. a fifth step of converting the block to be variable-length encoded in the fifth step to the code amount due to variable-length encoding in the block processed immediately before and the allocated code amount in that block; a sixth step of determining the difference and adding it as a carryover amount to the reference allocated code amount in the block to be currently processed, and setting it as the allocated code amount in the block to be currently processed; A method for encoding image data, characterized in that a fourth step performs encoding according to the encoding order of each color component obtained in the second step.