JPH04167868A - Coding device and coding method for picture - Google Patents

Abstract

PURPOSE:To obtain a coding output as a final output by deciding a code quantity per one block from an object code quantity and controlling the variable length coding in the unit of blocks so that the quantity is set within a desired code quantity. CONSTITUTION:A coding circuit 80 gives an input data received from a signal processing circuit 60 to an orthogonal transformation circuit 4, which applies orthogonal transformation by discrete cosine transformation to a block picture data for each block. The data (transformation coefficient) is stored in a relevant frequency component position and the result is inputted to a quantization circuit 6. The circuit 6 applies quantization of a 1st path to the data. In this quantization, the transformation coefficient is quantized with a quantization width resulting from multiplying a standard quantization coefficient alpha given from a control circuit 18 corresponding to a picture quality setting value set by the user at the image pickup with a quantization matrix position for each preset frequency component. The data is subjected to variable length coding at a variable length coding circuit 8, subjected to zigzag scanning from a lower frequency component to a higher frequency component.

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.

[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 recording media such as memory cards, magnetic disks, or magnetic tapes instead of silver halide films.
The number of images that can be recorded on a roll of magnetic tape is specified, and the recording of this specified number of images must be guaranteed.
Moreover, the time required for data recording and reproducing processing needs to be short and constant. .

Similarly, digital VTR (video tape recorder),
When recording moving images, such as digital moving image files, it is necessary to be able to record a predetermined amount 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 reproducing processing needs to be short and constant.

Therefore, for this purpose, it is necessary to compress the image data so that the amount of data per frame falls within the specified capacity.

As a highly efficient image data compression method for this purpose, a coding method that combines orthogonal transform coding and variable length coding is widely known.

A representative example of this is a method that is 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 each divided block is subjected to orthogonal transformation.
Perform T (discrete cosine transformation).

Next, linear quantization is performed according to each frequency component, and the quantized values are subjected to Noffman encoding as variable length encoding. At this time, regarding the DC component, the difference value between it and the DC component of the neighboring block is subjected to Nofman encoding. The AC component is scanned from a low frequency component to a high frequency component, which is called a zigzag scan, and two-dimensional Huffman encoding is performed from the consecutive number of invalid (value is ambience) components and the value of the subsequent valid component. . The above is the basic -16= part of this method.

Since Huffman encoding, which is variable length encoding, is used in this basic portion, 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, while 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. Then, this predicted quantization width and the previous quantization width are sufficiently close, and
If the total amount of code generated this time is smaller than the target amount of code, the process is terminated and the code is output. If not, the process is repeated using a new quantization width.

The quantization width is relative to each frequency component = 17
- Prepare a quantization matrix that is a basic form representing quantization characteristics, and obtain the necessary quantization width by multiplying this basic quantization matrix by a quantization coefficient α.

Specifically, first, the basic part described above is quantized using the quantization width obtained using the standard quantization coefficient α, and then this is variable-length encoded, and the total code amount obtained by this is The information is compared with a preset target total code amount value that is the limit that should be stored, and when it reaches the target edge code amount, the final encoding process is performed using that quantization width, When the target edge code amount is reached, the final encoding process is performed using the quantization width, and when it is not within the target edge code amount, the total generated code amount and the target edge code amount are from,
For example, the Newton-Raphson method (Newton-Ra
phson 1teration), etc., to find the optimal quantization coefficient α that approaches the target total code amount, and then calculate a more optimized quantization width from the found quantization coefficient and quantization matrix. This is then used to perform the final encoding process.

The quantization width is changed using this method.

To explain the above operation in detail with reference to FIG. 9, first, as shown in (a), one frame of image data (one frame image proposed in other international standards is 720
x57B pixels) to a block of a predetermined size (for example,
Blocks A, B, C, consisting of 8×8 pixels...
), and as shown in (b), a two-dimensional DCT (discrete cosine transform) is performed as an orthogonal transform for each divided block, and the results are sequentially stored on a -8×8 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 on the 8×8 matrix, data indicating the value of the direct current component DC is placed at the origin position (0,0 position), and , 0.7 position is data indicating the maximum frequency value of the alternating current component AC in the horizontal axis direction, and 7
, 0 positions store data indicating the frequency value of the maximum alternating current component AC in the vertical axis direction, and data indicating the maximum frequency value of the alternating current component AC in the diagonal direction are stored in the 7 and 7 positions. 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, linear quantization corresponding to each frequency component is performed by dividing the stored data of each coordinate position in these 7 trixes by the quantization width for each frequency component (C), and this quantized value is , Huffman encoding is performed as variable length encoding. At this time, regarding the DC component DC, the difference value with the DC component of neighboring blocks 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 combined. and make it encoded data (di, d2. el, e2).

Regarding the AC component AC, coefficients that are not valid (value is not "0") are expressed by group numbers and additional bits.

Therefore, the AC component AC performs a scan called a zig-sag 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 using the group number of the component value, and the resulting 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 the 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.

In this basic portion, since Huffman coding, which is entropy coding, is used, the code amount is not constant for each image, so the code amount is controlled, for example, as follows.

First, using a provisional quantization coefficient α, the basic part is processed with the quantization width for each frequency component obtained by multiplying the determined quantization matrix by this quantization coefficient α, and at the same time, Total code M (total number of bits) generated for the entire screen
Find (g). From this total code amount, the target code amount, and the tentative quantization coefficient α used, we calculate the optimal quantization coefficient α to approach the target code amount for the DCT coefficients using Newton-Raphson-iteration. (New
ton Raphson Iteration) (11). Next, using this quantization coefficient α (i)
, repeat the process after quantization of the basic part described above. Then, from the total code amount generated this time, the total code amount generated last time, the target code amount, the quantization coefficient α used this time, and the quantization coefficient α used last time, the target code amount is again calculated. The optimal quantization coefficient α to be approximated is predicted by Newton-Raphson iteration.

Then, if the predicted quantization coefficient α and the previous quantization coefficient α are sufficiently close, and the total amount of code generated this time is less than the target amount of code, the process is terminated and the amount of code generated this time is The encoded data is output and stored in the memory card (f). If not, change the quantization coefficient α,
The process is repeated using this new quantization coefficient α.

[Problem to be solved by the invention]

As mentioned above, for example, in digital electronic still cameras, the number of images that can be recorded on one memory card or magnetic disk device must be guaranteed, and for this reason, image data is compressed and recorded. From the viewpoint of operability, the processing time needs to 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 above-mentioned international standard draft method. In this method, the method that combines block-by-block orthogonal transformation and variable-length coding as illustrated in the basic part above cannot process image data. However, because it uses variable length encoding, 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 or magnetic disk device is undefined. There were drawbacks.

In addition, in the method of controlling the amount of code as exemplified in the conventional example to solve this problem, the number of times the bus, which is the basic part of encoding, is repeated varies depending on the image, which not only makes the processing time unstable. , - Boat fishing had the disadvantage of requiring a long processing time.

As a method for solving this problem, the present inventors proposed the following method (see Japanese Patent Application No. 1-283761 and Japanese Patent Application No. 2-1-37222).

This proposed method is a compression method that combines orthogonal transformation and variable length coding. In order to control the amount of generated code, the sampled image signal stored in the image memory is Divide each piece into blocks, perform orthogonal transformation for each divided block, and then quantize the transform output with a provisional quantization width.
This quantization output is variable-length coded, and the generated code amount for each block and the total code amount for the entire image are calculated, and then the provisional quantization width, the total generated code amount, and the amount of code generated per image are calculated. A new quantization width is predicted from the target total code amount. In addition, 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 per image (statistical processing : Processing of the first bus).

Then, using the new quantization width, the image signal in the image memory is again divided into blocks, orthogonally transformed, quantized, and variable length encoded, and the amount of generated code for each block is determined by the assigned code of that block. If the amount is exceeded, processing is performed such as stopping variable-length encoding midway through and moving on to processing the next block (encoding processing: second block).
path processing).

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.

-25= However, although the above method provides very good results, it requires at least a memory to store the amount of code generated for each block, which increases the circuit scale and reduces power consumption. This will lead to an increase. For portable products, where miniaturization is very important, increased power consumption means that the battery portion occupies a larger proportion, which increases weight, and increases in overall size due to increased circuit scale. , which is extremely inconvenient;
Furthermore, there are problems in using the above method, such as increasing costs for low-priced products.

In recent years, there have been various user needs, such as those who place emphasis on image quality even if the product is expensive, and those who want an inexpensive product even if they sacrifice some image quality. However, there is a need for a method that can be realized using a simple circuit even if it requires a somewhat complicated circuit or provides high image quality. Also, these 2
The two methods must monitor the compressed data and be compatible with each other during playback.

Therefore, it is an object of the present invention to encode image data within a certain amount of code within a certain processing time using a simple circuit configuration without degrading the image quality as much as possible. An object of the present invention is to provide an encoding device and an encoding method.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention divides image data into blocks, performs orthogonal transformation on each of the divided blocks in turn, quantizes the transform output by a quantization means, and sends this quantized output to a variable length encoding means. In an encoding device that performs variable-length encoding on data and encodes data for each block, firstly, when encoding the block, the amount of code generated by the encoding process in the block to be encoded and the amount of code generated by the encoding process in the block to be encoded are The amount of excess or deficiency of the generated code amount with respect to the allocated code amount is calculated based on the allocated code amount in the block, and 1 is predetermined according to the target total code amount, which is the allowable code amount per image. code amount allocation means that calculates the code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block as the allocated code amount of the next block to be processed; and terminating means for controlling the variable length encoding means to abort the variable length encoding so as not to exceed the allocated code amount.

Second, there is a compression rate specifying means for specifying the compression rate, and the total allowable target code amount and quantization width per screen and the quantization width per block according to the compression rate specified by the compression rate specifying means. a compression rate selection means for determining a standard allocated code amount; and a compression rate selection means for determining a standard allocated code amount; Calculate the excess or deficiency of the generated code amount with respect to the allocated code amount, and then process the code amount obtained by adding the calculated excess or deficiency amount to the reference code amount per block determined by the compression rate selection means. a code amount allocating means for determining the allocated code amount of a block; and a variable length encoding means for terminating the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means for each block. a truncation means for controlling, an encoding output means for outputting the transform coefficient variable-length encoded by the variable-length encoding means as a code, and an abort means for outputting the quantization coefficient determined by the compression rate selection means for the quantization means; and a control means for controlling quantization using the quantization width.

Furthermore, the present invention divides image data into blocks, and each divided block sequentially undergoes orthogonal transformation to decompose the image data for each block from low frequency components to high frequency components in order, and performs this transformation. In an encoding device which quantizes an output by a quantization means, gives this quantized output to a variable length encoding means to perform variable length encoding, and encodes data for each block, the third step is a code of the block. In encoding, based on the code amount generated by the encoding process in the block to be encoded and the allocated code amount in the block, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated. The code amount obtained by adding the calculated excess/deficiency amount to the standard code amount per block predetermined according to the target total code amount, which is the allowable code amount, is used as the allocated code amount for the next block to be processed. a desired code amount allocation means; and an abort means for controlling the variable length encoding means to abort the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocation means for each block; control means for controlling the quantization means to perform quantization using a predetermined quantization width; For the DC component of the data, there is an encoding processing unit for the DC component that obtains the difference from the DC component in the previous encoding processing block and encodes this difference with variable length coding, and an encoding processing unit for the DC component. and an AC component encoding processing unit that performs variable length encoding on the AC component after the processing is completed, and the code cost aborting means is capable of performing abort control only on the AC component encoding processing unit. The configuration is as follows.

Fourthly, a code amount calculation means for calculating the code amount of the transform coefficients of the entire image encoded by the variable length encoding means; and a code amount of the entire image calculated by the code amount calculation means; quantization width prediction means for predicting an optimal quantization width from the permitted target total code amount per screen and giving the predicted quantization width to the quantization means; Based on the code amount generated by the encoding process in the block to be processed and the allocated code amount in the block, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated, and based on the target total code amount. code amount allocation means for determining the code amount obtained by adding the calculated surplus/deficiency amount to the determined reference code amount per block as the allocated code amount of the block to be processed next;
Termination means for controlling the variable length encoding means to terminate the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocation means for each block;
The quantization means first performs a first encoding process at least once to predict an optimal quantization width using a predetermined provisional quantization width from the target total code amount, and then and a control means for controlling the second encoding process to be performed using the optimum quantization width predicted by the quantization width prediction means.

Furthermore, the present invention divides image data into blocks, sequentially performs orthogonal transformation on each divided block, quantizes the transform output by a quantization means, and supplies the quantized output to a variable length encoding means. In an encoding device that performs variable length encoding and encodes data for each block, the fifth component is a compression rate designation means for designating a compression rate, and a compression rate designation means that corresponds to the compression rate designated by the compression rate designation means. a compression ratio selection means for determining a target total code amount allowed per screen, a provisionally determined quantization width, and a reference allocated code amount per block; and a conversion encoded by the variable length encoding means. a code amount calculating means for calculating the code amount of the entire image of coefficients; predicting an optimal quantization width from the code amount of the entire image calculated by the code amount calculating means and the target total code amount; quantization width prediction means for giving this predicted quantization width to the quantization means; and a code amount generated by the encoding process in the block to be encoded and an allocated code amount in the block when encoding the block; Based on this, calculate the excess or deficiency of the generated code amount with respect to the allocated code amount, and add the calculated excess or deficiency amount to the reference code amount per block determined by the compression rate selection means. code amount allocating means for determining the allocated code amount of the next block to be processed; an abort means for controlling the long encoding means; and a first method for predicting an optimal quantization width for the quantization means using a provisional quantization width predetermined from the target total code amount.
and a control means for performing control so as to perform the encoding process at least once, and then perform a second encoding process using the optimal quantization width predicted by the quantization width prediction means. do.

Furthermore, in the sixth step, the image data is divided into blocks, each of the divided blocks is subjected to orthogonal transformation, and the image data of each block is decomposed into components from low frequency components to high frequency components in order. In a coding device that quantizes a transform output by a quantization means, supplies the quantized output to a variable length coding means to perform variable length coding, and codes data for each block, the variable length coding means A code amount calculation means that calculates the code amount of the transform coefficients of the entire encoded image, the code amount of the entire image calculated by this code amount calculation means, and the allowable objective total code amount per screen. quantization width ff1l1 means for predicting a quantization width and giving the predicted quantization width to the quantization means; and a code generated by the encoding process in the block to be encoded when encoding the block; The excess or deficiency of the generated code amount with respect to the allocated code amount is calculated based on the amount and the allocated code amount in the block = 34 −, and the reference code per block determined based on the target total code amount. For the code amount allocation means and the quantization means, which obtain the code amount obtained by adding the calculated surplus/deficiency amount to the code amount as the allocated code amount of the block to be processed next, Preliminarily determine the optimal quantization width using the provisional quantization width i1+1
] control means for performing control so as to perform a first encoding process at least once, and then perform a second encoding process using the optimal quantization width predicted by the quantization width prediction means; The variable length encoding means obtains the difference between the DC component of the image data in each block obtained by the orthogonal transformation and the DC component of the previous encoding processing block, and calculates this difference. A DC component encoding processing section that performs variable length encoding, and an AC component encoding processing section that performs variable length encoding on the AC component after the processing of the DC component encoding processing section is completed. , the code cost truncation means is configured to enable truncation control only for the AC component encoding processing section.

Seventhly, the image data is divided into blocks, each divided block is sequentially orthogonally transformed, then quantized, and this quantized data is variable-length coded. In an encoding method that encodes data, the first step is to perform encoding processing on the data and check the code amount of the entire image, and the optimization is performed from the code amount of the entire image obtained in this first step. a second step of predicting the quantization width necessary for the block; a third step of performing quantization for each block using the predicted quantization width; Based on the code amount generated by the encoding process in the block to be processed and the allocated code amount in the block, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated, and the allowable code amount per image is calculated. a fourth step of determining the code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block predetermined according to the target total code amount as the allocated code amount of the block to be processed next; , and a fifth step of performing variable length encoding of each block within the allocated code amount for each block in the fourth step.

Furthermore, in the eighth step, the image data is divided into blocks, each of the divided blocks is sequentially subjected to orthogonal transformation, and the image data for each block is decomposed into components from low frequency components to high frequency components in order. In an encoding method in which data is encoded for each block by variable length encoding after quantizing the decomposed data, in the variable length encoding process, each block unit obtained by the orthogonal transformation is For the DC component of the image data, the difference between the DC component and the previous encoding processing block is obtained and this difference is variable-length encoded. After the encoding process for the DC component is completed, the AC component is The first step is to perform variable length coding on the image and check the amount of code for the entire image required for optimization.
A second step of predicting the quantization width necessary for optimization based on the code amount of the entire image obtained in the step, and performing quantization for each of the above-mentioned programs using the predicted quantization width. In the third step and encoding the block,
Based on the code amount generated by the encoding process in the block to be encoded and the allocated code amount in the block, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated, and the allowance per image is calculated. A fourth step of determining the code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block predetermined according to the target total code amount, which is the code amount to be processed, as the allocated code amount of the block to be processed next. It is characterized by steps and more.

[For production]

In such a configuration, image data is divided into blocks, each divided block is sequentially orthogonally transformed to obtain transform coefficients, and the orthogonally transformed transform coefficients are quantized by a quantizer. In the first configuration, standard allocation per block is predetermined according to the target total code amount, which is the allowable code amount per image. Based on the allocated code amount for the block currently being processed, which is obtained by combining the code amount and the excess or deficiency of the code amount generated in the encoding process of the block before this block with respect to the allocated code amount,
The variable length encoding process is performed so as to monitor the generated code amount of the encoding process in the block currently being processed, and stop the encoding in that block before the amount exceeds the allocated code amount.

In the case of the second configuration, by selecting the compression rate, the target total code amount, quantization width, and code amount per block are determined according to the selected compression rate, and the image data is After dividing into blocks, performing orthogonal transformation, and performing quantization with the quantization width, the assigned code of the reference code amount per block and the code amount generated in the encoding process of the block before this block. Based on the allocated code amount for the block currently being processed, which is obtained by combining the excess and deficiency with respect to the amount, the generated code amount of the encoding process in the currently processed block is monitored, and whether this amount exceeds the allocated code amount. Variable-length encoding processing is performed to terminate encoding in that block beforehand.

In addition, in the case of the third configuration, the image data is divided into blocks, and the divided blocks are sequentially subjected to orthogonal transformation for each block to decompose the image data from low frequency components to high frequency components in order, This transform output is quantized by a quantization means, and then this quantized output is given to a variable-length encoding means to be variable-length encoded to encode data, or each block unit obtained by the orthogonal transformation is For the DC component of the image data, obtain the difference between this block and the DC component in the previous block, and
This difference is variable-length encoded, and after the encoding process for the DC component is completed, the reference code amount per block, which is predetermined according to the target total code amount, and the block The code amount for the block currently being processed is calculated based on the allocated code amount for the block currently being processed, which is obtained by adding up the excess or deficiency of the code amount generated in the encoding process of the previous block to the allocated code amount. The variable length encoding process is performed so that the amount of code generated in the encoding process is monitored and the encoding of the block is terminated before the amount of code generated exceeds the allocated amount of code.

In addition, in the case of the fourth configuration, the image data is divided into blocks, orthogonally transformed, quantized with a provisional quantization width, variable-length encoded, the code amount of the entire image is calculated, and the optimal Predict the quantization width. Then, after quantizing the transform coefficients that have undergone orthogonal transformation again using the new quantization width, the standard allocated code amount per block determined in advance according to the target total code amount and the previous block The code for the block currently being processed is calculated based on the allocated code amount for the block currently being processed, which is obtained by adding up the excess or deficiency of the code amount generated in the encoding process for the block with respect to the allocated code amount. The variable-length encoding process is performed so that the amount of code generated in the coding process is monitored, and the coding in that block is terminated before the amount of code generated in the coding process exceeds the allocated code amount.

In the case of the fifth configuration, by selecting the compression rate, the target total code amount, provisional quantization width, and reference allocated code amount per block are determined according to the selected compression rate, and the Block the data and perform orthogonal transformation,
After performing quantization using the provisional quantization width, variable-length encoding is performed, the code amount of the entire image is calculated, the optimal quantization width is predicted from this, and then the orthogonal transformed transform coefficients are , after performing quantization with the new quantization width obtained by the prediction, the allocated code of the standard allocated code amount per block and the generated code amount in the encoding process of the block before this block. Based on the allocated code amount for the block currently being processed, which is obtained by combining the excess and deficiency with respect to the amount, the generated code amount of the encoding process in the currently processed block is monitored, and before this exceeds the allocated code amount. Then, variable-length encoding processing is performed to terminate encoding in that block.

In the case of the sixth configuration, the image data is divided into blocks, and the divided blocks are sequentially orthogonally transformed for each block to transform the image data for each block from low frequency components to high frequency components. The components are decomposed, this transform output is quantized by a quantizing means, and then this quantized output is given to a variable length encoding means to be variable length encoded to encode data. Among the image data for each block, for the DC component, the difference between this block and the DC component in the previous block is obtained, and this difference is variable-length coded, and for the AC component, this DC component is encoded. After the processing is completed, check the amount of code required for the entire image for optimization, predict the optimal quantization width from this, perform quantization for each block using this predicted quantization width, and The standard allocated code amount per block, which is predetermined according to the total code amount, and the amount of excess or deficiency of the generated code amount in the encoding process of the block before this block with respect to the allocated code amount are combined. Based on the allocated code amount for the block currently being processed obtained by Variable length encoding processing is performed so as to terminate the process.

In addition, in the seventh method, image data is divided into blocks, each divided block 2 is subjected to orthogonal transformation in order, and then quantized, and this quantized data is variable-length encoded. , When encoding data for each block, perform the encoding process on the data, check the code amount of the entire image, and predict the quantization width necessary for optimization from the obtained code amount of the entire image. The predicted quantization width is used to perform quantization for each block, and when encoding the block, the code amount generated by the encoding process in the block to be encoded and the block The amount of excess or deficiency of this generated code amount with respect to the allocated code amount is calculated based on the allocated code amount in The code amount obtained by adding the calculated surplus/deficiency amount to the standard code amount of Perform encoding.

Furthermore, in the eighth method, image data is divided into blocks, and each divided block is sequentially subjected to orthogonal transformation to decompose the image data for each block into components from low frequency components to high frequency components. , After quantizing this component decomposition, data is encoded for each block by variable length encoding. In the variable length encoding process, each block unit obtained by the orthogonal transformation is For the DC component of the image data, the difference between the DC component and the previous encoding processing block is obtained and this difference is variable-length encoded. After the encoding process for the DC component is completed, the AC component is Variable-length coding is performed on the image, and the amount of code required for the entire image to be optimized is determined. Based on the amount of code for the entire image obtained, the quantization width required for optimization is predicted. Quantization is performed for each block using the quantization width, and when encoding the block, the code amount generated by the encoding process in the block to be encoded and the allocated code amount in the block are calculated. The amount of excess or deficiency of this generated code amount with respect to the allocated code amount is calculated based on the amount of generated code, and the amount of excess or deficiency of this generated code amount with respect to the allocated code amount is calculated, and the reference code amount per block determined in advance is The code amount obtained by adding the calculated surplus/deficiency amount is determined as the allocated code amount of the block to be processed next.

In this way, this device determines the amount of code per block from the target amount of code, and sequentially monitors the encoded output.
Variable length encoding is controlled on a block-by-block basis so that the amount of code is within a desired amount, and the encoded output is obtained as the final output.

Additionally, if this device first performs statistical processing at least once to optimize the quantization width and then performs encoding processing, even better results can be obtained, so first optimize the quantization width by statistical processing. The amount of code required for the entire image is checked, and then the process begins to perform optimized encoding based on the information obtained through this statistical processing. Variable length encoding is controlled on a block-by-block basis so that the encoded output is obtained as the final output.

Therefore, first, the image is blocked, quantized using a quantization width predetermined from the target code amount for the elements of this blocked image, and the transform coefficients obtained by this quantization are varied. Long coding and variable length coding are performed by adding the allocated code amount per block obtained in advance from the target code amount and the excess or deficiency of the allocated code amount caused by previous encoding. This is because the final output is obtained by performing variable-length encoding of the element within the allocated code amount of the block and output processing to save all the codes of the image to be processed. , the obtained image data can now be encoded within a certain amount of code, and in cases where the number of images to be stored is specified, a certain amount of storage capacity can be achieved with respect to the storage capacity of the storage means. In addition to being able to guarantee the number of sheets, constant processing =
47- It becomes possible to perform encoding within time.

Further, since the code amount control uses only the allocated code amount per block and the excess or deficiency of the allocated code amount up to that block, a large storage area is not required and it can be realized with a relatively simple configuration. Furthermore, since the coding is terminated for high frequency components, there is relatively little deterioration in image quality.

Also, first perform statistical processing using a provisional quantization width at least once to predict the optimal quantization width, and then encode using the optimal quantization width obtained based on this. In this method, processing is completed in at least one pass of statistical processing and a fixed number of passes of encoding processing, so it is possible to perform encoding within a fixed processing time, and it also eliminates code truncation during encoding. In addition, since the coding is terminated for high frequency components, there is almost no deterioration in image quality.

Therefore, according to the present invention, with a simple configuration, it is possible to perform encoding within a certain amount of code within a certain processing time, and there is almost no deterioration in image quality. Furthermore, according to the present invention, since the code itself is not affected, it is possible to maintain compatibility during playback with the International Standard East System shown in the conventional example and in the section of the problem to be solved by the present invention. In other words, a common playback device may be used.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

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 divides one image (screen) into blocks, and sequentially orthogonally transforms the data of the constituent pixels of each block for each block, further quantizes the data, and compresses and encodes the data. In this process, the image data of each block is sequentially quantized using a quantization width determined in advance based on the target total code amount, which is the final amount of code that is desired to be stored per image, and the quantized data is encoded. , and the code amount obtained by this encoding is determined by the standard allocated code amount per block predetermined from the target total code amount and the encoding process for the block that is in the processing order immediately before this block. Encoding is proceeded while monitoring the code amount so that the code amount is within the allocated code amount, which is the allowable code amount for the block, which is determined by adding the amount of excess or deficiency of the generated code amount to the allocated code amount. OB
(End Of Block) When the code amount reaches the allocated code amount, including the code, the coding of that block is terminated, or even if the DC component exceeds the adjusted allocated code amount, it is always encoded, and the above-mentioned at that time The excess/deficiency with respect to the allocated code amount is memorized, and when the next block is encoded, this excess/deficit amount is added to the standard allocated code amount and adjusted, and the allocated code amount is set as the allocated code amount for this block. , variable length encoding is performed within this allocated code amount range.

Another way of thinking is that the present invention sequentially quantizes the data of the constituent pixels of each block in block units, and when compressing and encoding the data, the amount of code that is ultimately desired to be stored per image is determined. The image data of each block is sequentially quantized using a quantization width predetermined based on the target total code amount, and the optimal quantization width is predicted from the code amount. , the image data of each block is quantized in order, and the quantized data is encoded, and the code amount obtained by this encoding is the standard allocated code amount per block determined in advance from the target total code amount. The allowable code amount for that block, which is determined by the sum of the amount of code generated in the code ratio processing of the block in the processing order immediately before this block, and the excess or deficiency of the allocated code amount. Encoding is proceeded while monitoring the code amount so that it stays within the allocated code amount, and when the code amount reaches the allocated code amount, including the EOB code, the encoding of that block is terminated, but the DC component is adjusted. Even if the allocated code amount is exceeded, the code is always encoded, the excess or deficiency with respect to the allocated code amount at that time is memorized, and when the next block is encoded, this excess or deficiency is used as the standard for the next block. In addition to the allocated code amount, =51- is adjusted to be the allocated code amount for this block, and variable length encoding is performed within the range of this allocated code amount.

The former is a 1-pass method, and the latter is a 2-pass method, and in both cases, when quantizing with a certain quantization width and variable length encoding,
Using the standard allocated code amount assigned to each block as a standard, we can calculate the variation in the generated code amount in each block.
This is to make adjustments by absorbing it in the next block, and this adjusted amount is set as the allocated code amount, and the block is encoded within the range of this allocated code amount, and when the allocated code amount is exceeded, that block is The encoding of is terminated. 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 entering the AC component and exceeding the allocated code amount, encoding is discontinued.

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.

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. In this way, if 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. It is distinctive in that it takes - To specifically describe the two-pass method, in the present invention, the first
As pass processing, statistical processing is performed using a provisional quantization width determined in advance from the target total code amount to predict an optimal quantization coefficient. Next, final encoding processing is performed as second pass processing.

In the second pass, each block is quantized using the predictive quantization coefficient and encoded, and the amount of code obtained by this encoding is determined per block in advance based on the target total code ffi. The excess/deficiency of the code amount caused by the encoding process for the block (a) immediately before that block (the assigned code allocated to the block (a) immediately before the block) Encoding is proceeded while monitoring the code amount so that the amount of code is within the allocated code amount determined by adding the difference between the amount of code generated in the block (a) and the amount of code generated in the block (a). When the amount of code reaches the allocated code amount, encoding of that block is terminated, but the DC component is always encoded even if it exceeds the allocated code amount.
The surplus/deficiency of the allocated code amount at that time is memorized and the next block is encoded.

This code amount control by aborting coding for each block using the allocated code amount per block can be used to control the code amount for the entire image by itself, or the code amount control when performing approximate code amount control It can also be used for fine adjustment when the amount exceeds the target code amount.

The one-pass method mentioned earlier is when encoding is performed in one pass for statistical processing, and since the encoding is completed in one pass, it has the great effect of being able to perform processing in a short time. However, unless there is a system that always encodes similar images, that is, images with the same amount of code generated by encoding, it may not be possible to obtain very good image quality depending on the image.

On the other hand, when statistical processing is used, the two-bus method is used, and when this statistical processing is combined with code amount control by cutting off coding for each block using the allocated code amount per block, it is particularly effective. is obtained. ,
Hereinafter, this case will be explained in detail by taking an example.

Statistical processing predicts the optimal quantization width, and by using this optimized quantum width in encoding processing, it becomes possible to approach the total code amount as desired.

If the code amount falls within the target total code amount at this point, this processing alone is sufficient, but if an upper limit for the data amount of one image is specified, even 1 bit, let alone 1 byte, is enough to reach the target amount. Exceeding the code amount is not allowed. Therefore, a processing method is needed when the number exceeds the limit.

This is control based on the allocated code amount for each block. This is used for fine adjustment when the code amount during encoding exceeds the target total code amount (a value corresponding to the upper limit of the data amount of one image). It is also possible to check the results of executing the encoding process using the optimal quantization width predicted by statistical processing, and if it does not exceed the quantization width, end the process, and if it exceeds it, perform post-processing, but in that case, the statistical processing , encoding process,
There are three post-processing steps, which not only takes time, but also requires storage between the encoding process and post-processing so that codes of different lengths can be distinguished without being concatenated, which requires a lot of memory. Because there is a problem that it is necessary,
It is desirable to make fine adjustments during the encoding process. However, recklessly dropping data will lead to deterioration of image quality, so it must be avoided.

Therefore, in the present invention, the visual influence is minimized by omitting the high frequency components of each block. However, since it is not known whether the amount of code exceeds until the encoding is finished, in the present invention, this is determined for each block at the time of encoding.

A provisional quantization width predetermined according to the target total code amount and 1
Determine the amount of code to be allocated per block, and use this as a guideline that says, ``Unless the amount of code for each block exceeds this, the amount of code for the entire image will not exceed the target amount of code.'' This guideline is applied to each block. The allocated code amount for each block is used as a monitoring standard. In the encoding process according to the present invention, 1 is added to each block, and encoding is terminated in each block so as not to exceed the allocated code amount of the block.

Each block is decomposed into frequency components by orthogonal transformation according to the spatial frequency of the image data in that block, and the data is quantized, so when encoding each block, the frequency components are divided from low frequency components to high frequencies. When sequentially encoding components, guidelines (allocation code N
) while monitoring to ensure that it does not exceed the encoding limit. In general, this guideline is used for images in which there are blocks that are so sufficient that the coding ends without using the entire allocated amount of code, and blocks that are insufficient. Therefore, for blocks that do not overlap, that is, for blocks in which the generated code amount including EOB is less than the allocated code amount, or blocks that have just reached the allocated code amount, coding is completed without any problem, that is, EOB is output. Blocks that exceed the allocated code amount are encoded before they exceed the allocated code amount, and higher frequency components are cut without being encoded so that they stay within the allocated code amount. do. In short, for blocks that overlap midway, the encoding of that block is finished before the block exceeds the limit, that is, an EOB is output. Since this mid-term termination often results in a surplus of the allocated code amount (because it is variable-length encoding, the code length changes depending on the data value, a surplus often occurs if it is terminated midway). The remainder is added to the standard 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, but 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 and the Finish encoding the block, that is, output EOB. The insufficient amount of code is carried over to the next block as a shortage, and the shortage is subtracted from the standard allocated code amount of one block to become the allocated code amount of the next block. At this time, EOB is also Huffman code -, so EO
It is necessary to perform coding abort control so that the amount of code including B is within the allocated code amount. .

In this way, for example, if most blocks finish coding without needing to be truncated, and some of the remaining blocks finish coding with some very high frequencies omitted, there will be missing information. However, what is missing is only information in high frequency components that have little visual impact. With this method, encoding can be completed in two steps: statistical processing and encoding processing, and there is no need to repeat optimization many times as in the conventional method. You can control the amount,
It is now possible to keep the total code amount within a specified value without requiring a large number of working memories as in the past, and furthermore, deterioration in image quality can be suppressed.

In the present invention, the amount of code generated in each block of an image is different in advance, that is, the amount of code generated is locally uneven, but if we consider a group of several blocks or tens of blocks as a microblock, each microblock This method focuses on the fact that the amount of generated codes is relatively unbalanced. Therefore, even if the standard allocated code amount per block is fixed, the generated code amount of each block can be reduced by carrying over the surplus of the generated code amount to the allocated code amount of subsequent blocks. While adapting to changes, microblocks control the amount of generated code.

With this principle, if blocks with a large amount of generated code are concentrated at the beginning of encoding, the intended effect may not be obtained, but normally such a case is almost impossible,
Even if there is, the effect will appear in visually unimportant positions of the image, so it is not a problem, but if you divide, for example, 90% of the desired amount of code for the entire image by the number of blocks, In this method, the remaining 10% is given as a surplus of the allocated code amount for the previous block when encoding the first block. It can be solved by taking

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 operating 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 4Qa for forming an optical image.
and an image sensor 40b such as a CCD. The signal processing circuit 60 includes an amplifier 60 that performs amplification, noise removal, etc.
a and an A/D that converts analog signals into digital signals.
Converter 60b and buffer 7 memory 80 consisting of RAM, etc.
c, and a process circuit 80d that performs color signal formation and the like. The encoding circuit 80 includes, for example, an orthogonal transform circuit 4 that performs orthogonal transformation such as DCT (discrete cosine transform), a quantization circuit 6 that performs linear quantization, and a Huffman code 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 16, and a control circuit I8 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 71 can be attached to and removed from the electronic camera body 1.

The control circuit 90 is implemented using 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 statuses 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 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 amount of 71 codes per image, which is determined according to the compression rate, and providing this to the encoding circuit 80 as target code amount setting information. Further, when the shutter operation button 50, which is a switch, is pressed, the shutter function is activated and 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. Therefore, by reading and controlling this, a video signal can be obtained from the image sensor 40b. 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
An image sensor 4 (having a lb.
The photographic lens 40aL'J: converts the optical image formed on the image sensor 40b into an image signal and converts it into a signal processing circuit 60.
This is what is output to. Signal processing circuit 6° is amplifier BO
a SA/D converter 60b1 buffer memory 60c,
A process circuit BOd is included, and this process circuit 60
d, the image signal obtained by the image sensor 40b is converted into color signals Y, RY (hereinafter, this RY is abbreviated as Cr (chroma red)), B-Y (hereinafter, this B-
In addition to separating Y into each color component of Cb (abbreviated as chroma blue), gamma correction, white balance processing, etc. are performed.

-65= The image data of the output video signal of the imaging system 40 that has been digitally converted by the A/D converter 60b is stored in a buffer memory 60c having a capacity for one frame, for example.
By being read out and given to the process circuit 11i0d, the Y component, which is a luminance signal system, and the Cr and Cb acid components, which are chroma (C; color difference signal) systems, are separated. The image data stored in the buffer memory 80c is first processed by a process circuit to obtain Y component data of the image signal in order to perform statistical processing on the luminance signal, and this is then provided to the encoding circuit 80. , Y component data, and once this processing is completed, chroma-based Cr and cb acid component data are processed and then encoded.

The signal processing circuit 60 has a blocking function, and the image data for the Y component and the Cr and Cb components (one frame or one field) is read out from the buffer memory BOc and processed. It is possible to perform a blocking process to divide the data into blocks of a predetermined size. Here, the block size is 8x8 as an example, but this block size is not limited to 8x8.
Further, the block sizes may be different between Y and C (chroma type).

In this embodiment, the 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.After the statistical processing is completed, the chroma system Crs In order to start statistical processing of the Cb acid component data, reading and blocking data of the chroma system Cr, CI>component is started.

Chroma block formation is 1. First, all the image data of the Cr component is divided into blocks, and then the Cb
It is assumed that the acid component image data is divided into blocks.

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 (transformation coefficients) output from the orthogonal transformation circuit 4, and in the first quantization, changes the quantization width for each frequency component set in advance to the shooting mode. The transform coefficients are quantized using a quantization width corrected by multiplying by a preset quantization coefficient α, and in the second time, quantization is performed using the optimal quantization coefficient α determined by the previous process. This is the configuration to do.

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. 9 is output by Huffman encoding the difference value from the DC component of the block that has been subjected to variable length encoding immediately before. AC component [A
Regarding [C], look at the conversion coefficients in order from the 2nd to the 64th in the scanning order in Figure 9, and if a non-zero (i.e. valid) coefficient comes out, it is the continuation that existed immediately before it. The number of 0 (invalid) coefficients (zero run) and the value of their valid coefficients are encoded into two-dimensional Huffman code and output.

Also, if invalid coefficients continue after a certain coefficient up to the 64th coefficient, EOB (end of block) indicates the end of the block.
of block) is output. Furthermore, when a termination signal is input manually, encoding is terminated and BOB is added and pressed. 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 the input Y, Cr, and Cb components, and calculates YSCrscb.
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 the configuration to output to.

The quantization width prediction circuit 12 receives information on the target code amount from the control circuit 18 at the start of the first bus, and uses this code amount information to calculate the following formula (%). Bi-soto number), s
p is a quantization coefficient, and a and b are constants.

The initial value of the quantization coefficient α is set using the relationship of From the target total code amount, which is the maximum allowable data amount per image, for example, using the = 70 - relationship in equation (1), determine the optimal quantization coefficient to approach the target total code amount by linear prediction. α is predicted by taking into account the quantization coefficients actually used this time.

Here, how to set the quantization coefficient to the optimal value?
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 quantization 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 code amount to be allocated 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 total code amount. is calculated and output to the encoding abort circuit 16.

The calculation method here is, for example, by proportionally allocating the target total code amount using the ratio of the code amounts for each color component, and further dividing the allocated code amount for each color component by the number of blocks.

For example, by multiplying the code amount of a certain color component by the target total code amount, dividing it by the code amount of the entire image, and then further dividing by the number of blocks of that color component, Determine the allocated code amount. As a result, the amount of code allocated to each color component is suppressed to the extent that it is possible to make it in time, depending on the actual amount of code for that color component. will be allocated a lot to

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. , calculates the standard allocated code amount per block for each color component from the code amount for each color component and the code amount for the entire image inputted from the code amount calculation circuit 14, and the target total code amount, and calculates the standard allocated code amount per block for each color component. The data of the standard allocated code amount per block of the component is stored in the block allocated code amount data table. The standard allocated code amount per block for each color component in this block allocated code amount data table is given to the encoding abort circuit 16 when the corresponding color component is subjected to variable length encoding processing.

The encoding abort circuit 16 adds the standard allocated code amount per block for the corresponding color component from the code amount allocation circuit 20 and the excess/deficiency of the generated code amount in the previous block to the corresponding block. At the same time, the code length of each code from the code amount allocation circuit 20 is subtracted from the allocated code amount, and the remaining allocated code amount is equal to the code amount to be sent and E
If the total code amount is smaller than the total code amount with the OB code, an abort signal is output and given to the variable length encoding circuit 8, the encoding of that block is finished, and the code amount transmitted from the allocated code amount of the block is It has the function of subtracting the value and holding that value as the remainder of the allocated code amount.

Therefore, in the encoding abort circuit 16, this assigned code=74
- Referring to the amount, the input code amount to be sent and EOB
If the amount of codes to be transmitted does not exceed the allocated code amount, no truncation is performed, the encoding of that block is finished, the amount of codes to be sent is subtracted from the allocated code amount of the block, and that value is used as the allocated code. The operation is to hold the amount as a remainder. 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 transmission, the encoding of the block is finished, and the transmitted 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 10 connects the variable length codes inputted from the variable length encoding circuit 8. The code output circuit 10 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
pass), examines the amount of information for each color component and the amount of information for the entire image required for optimization, and then performs processing to perform optimized encoding based on the information obtained through this statistical processing. enter(
2nd pass).

To do this, we first block the image, quantize the elements of this blocked image using a standard quantization coefficient α, variable length encode the transform coefficients obtained by quantization, and then From the code amount information of each element of each color component obtained by this variable length encoding and the code amount information of the entire image, predict the coding coefficient α required to obtain the optimal code amount, per block for each element of each color component. Determining the standard allocated code amount, shifting 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, and determining the prediction quantum for the elements of this blocked image. The following steps are performed: quantization processing using the conversion 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. It is assumed that the overall control management is performed by the control circuit 18 in the figure.

Incidentally, such functions of the control circuit 18 can be easily realized by using a microprocessor (MPU).

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 detachably connected to this, and the image data and quantization width (or information corresponding to this) encoded and output by the encoding circuit 80 are transferred to the recording medium via the interface circuit 70a. 71.

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, a camera user operates a 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, a subject image or an optical image is formed on an 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 a signal processing circuit 60, where it is amplified by an amplifier circuit 60a in the signal processing circuit 60, and is amplified by an A/D converter [A/D by iob].
After conversion, it is temporarily held in the buffer memory 60c. Thereafter, the signal is read out from the buffer memory 60c, and processed by the process circuit Sod in the signal processing circuit 60, such as band correction and color signal formation.

Here, the subsequent encoding process is Y (luminance), Cr.

Since it is performed in the order of the Cb (both color difference) signals, color signal formation is also performed in accordance with this order. That is, the image signal is read out in blocks in an 8 x 8 matrix, and the process circuit extracts the Y component, Cr component (R-Y component), Cb acid component B from this blocked image signal data.
-Y component), and performs gamma correction, white balance processing, etc.

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 60d are YSCr, C
Each component of b 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 of the component image data is divided into blocks, which are then subjected to statistical processing at a later stage.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.

Then, the orthogonally transformed block image data (transformation coefficients) are stored at corresponding frequency component positions on an 8x8 matrix in a buffer memory (not shown) (the origin of the matrix is the DC component, and the rest are AC components and the origin is This is input into 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 settings set by the user at the time of shooting are applied to the quantization matrix for each preset frequency component (frequency components are determined corresponding to each matrix position of the blower). The control circuit 18 corresponds to the value.
The transform coefficients are quantized using the quantization width multiplied by the standard (temporary) quantization coefficient α given by (Fig. 8 (hl).

j)). The quantization matrix at this time may be the same for 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 input quantized 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 acid component DC, the data of this DC component DC is the DC component D of the block (the previous block) that was subjected to variable length encoding immediately before.
The difference value dHf-DC with C is Huffman encoded (8th
Figures (di), (el)).

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

Further, the variable length encoding circuit 8 increments the sign of EOB (end of block) 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). Then, such processing is executed for all blocks of one image.

Once such processing for the Y component is completed, the same processing is then performed for each of the Cr, , and Cb components.

On the other hand, the code amount calculation circuit 14 receives the input YsCrscb.
In order to calculate the code amount for the entire image for each color component, the code amount for each color component of Y, Cr, and Cb is calculated, and the code amount is integrated for the entire image (g2
), and when all Huffman encoding processing for one color component has been completed, the code amount data for each color component is output to the code amount allocation circuit 20. The code amount allocation circuit 20 writes the code amount data for each color component as the code amount of the corresponding color component in the block allocation code amount table.

Then, for all blocks of one image, YlCr, C
When the Huffman encoding process for all components b is completed, the code amount calculation circuit 14 outputs the code amount data for the entire image to the quantization width prediction circuit 12 under the control of the control circuit 18, and The code amount data 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)).

Further, the code amount allocation circuit 20 calculates the standard allocated code amount per block for each color component from the input code amount for each color component, the code amount for the entire image, and the target total code amount, for example, the code amount for each color component. It is calculated by proportionally allocating the target total code amount using the amount ratio (FIG. 8 (h3)).

Specifically, to determine the standard allocated code amount per block for a certain color component, multiply the code amount of the color component by the target total code amount, and divide it by the code amount of the entire image. Using the obtained result, divide by the number of blocks in that color component, and use the result as the standard allocated code amount per block for that color component.

Then, the data of the calculated standard allocated code amount per block for each color component is stored in the block allocated code amount data table. The allocated code amount data for each color component in this block allocated code amount data table is provided to the encoding abort circuit 16 when the corresponding color component 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, the second pass processing begins. This second pass process is
It is a process to obtain a final encoded output optimized to fit within the target total code amount.

This process is first performed on the Y component, and after the Y component is completed, it is performed on the Cr and Cb acid components. That is, the image data is first read out in blocks, and the image signal data of the Y component (luminance system) extracted and output from the signal processing circuit 80 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 djff-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 code per block to be transmitted for the element stored in the block allocation code amount data table. outputs the standard allocated code amount to the encoding abort circuit 1B, and on the other hand,
The encoding abort circuit 16 adds the standard allocated code amount per block for each color component and the remainder of the allocated code amount in the encoding process of the previous block to determine the allocated code amount for the corresponding block, and also calculates the allocated code amount for the corresponding block. If the allocated code amount is not exceeded even if the EOB code is sent out, a process is performed to reduce the code amount to be sent 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 sent and the EOB code exceeds the remaining code amount of the allocated code amount, the coding abort circuit 16
An abort signal is output to terminate the Huffman encoding of that block, and at the same time, the transmitted code amount is subtracted from the allocated code amount of the block 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 ■6, 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 ■6.
outputs an abort signal to the variable length coding f circuit 8 to finish the Huffman encoding of the block, and subtracts the transmitted code amount from the allocated code amount of the block to obtain the remainder of the allocated code amount as the value of ). Hold.

Therefore, the variable length encoding circuit 8 outputs the converted Huffman code to the code output circuit 10 until the truncation signal is input from the coding truncation circuit 16, and all of the matrix is outputted before the truncation signal is generated. When the Huffman encoding for the element is completed, the variable length encoding circuit 8 outputs the code of EOB to the code output circuit 10. Furthermore, if the abort signal is input before the Huffman encoding for all elements of the matrix is completed, the variable length encoding circuit 8 outputs the EOB code to the code output circuit 10 instead of that code. It turns out. The code output circuit 10 temporarily stores this encoded data.

Then, the variable length encoding circuit 8 moves on to Nofman 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. Once the Y component has been processed in this way, the chroma components (Cr, Cb) are processed in a similar manner.

Even in processing the chroma component, the quantization circuit 6 uses the predicted optimal quantization coefficient α calculated by the quantization width prediction circuit 12 in the previous pass.

As for the chroma components, all encoding processing ends when the second pass processing of all blocks of one screen worth of images is completed.

Upon completion 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 card in the recording system 22.
Write to 1 (f). This is performed by the output of the code output circuit 10, and 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 by giving it to a memory card, which is a storage medium 71. . A storage medium 7 based on the output of this code output circuit 10
Writing to 1 may be done all at once after the second pass is completed, but when the first pass is completed and the second pass is executed, the result of connecting variable-length Huffman codes is , the data may be written to the storage medium sequentially in units of one byte or several bytes as soon as they are collected.

Note that, prior to this, the code output circuit 10 writes the optimal quantization coefficient α used for encoding into the header portion of the stored data of the encoded image, and leaves it as a clue during reproduction.

As described above, in this device, the number of recorded images determined according to the number of recordable images - the total code amount per image (target total code amount) is 1 block? Determine the standard allocated code amount for each block, adjust the surplus or deficiency of the generated code amount with respect to the allocated code amount in the block before the block, and use this to determine the allocated code amount for each block. By controlling the generated code amount, the generated code amount for the entire image is prevented from exceeding the target total code amount, and this 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, by performing statistical processing and optimizing the quantization width, the effect of the present invention becomes particularly remarkable. It is best to carry out the test twice. In addition, in statistical processing, instead of obtaining the total code amount for each color component and using this to determine the code amount per block, the code amount may be weighted empirically for each color component. ,
Furthermore, the amount of code per block may be the same without weighting for each color component, and the amount of statistics in statistical processing is not necessarily necessary for determining the reference amount of allocated code per block. Further, statistical processing is not limited to calculating the code amount by actually performing encoding using a provisional quantization width, but may also be calculated by calculating activity, for example.

In addition, the amount of code allocated per block within each color component does not necessarily have to be uniform, but is weighted based on the block position relative to the image. For example, a block in the center of the image is assigned a larger amount of code than surrounding blocks. You may also assign it. Furthermore, as shown in this embodiment, it is not necessary to allocate the entire target total code amount to the standard allocated code amount per block; for example, the target code amount is
The remainder that cannot be divided evenly when allocated to the standard allocated code amount per block may be given to the first block as an excess or deficiency up to the previous block.

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 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. Encoding can be performed 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, the allocated code amount is the sum of the predetermined standard allocated code amount per block based on the target total code amount 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 amount of code remains within the allocated code amount, and when the code amount reaches the allocated code amount, the encoding of that block is terminated, but if the DC component exceeds the allocated code amount. However, be sure to encode it, and remember the excess or deficiency of the allocated code amount at that time.
The process moves on to encoding the next block.

This means that the amount of code generated in each block of an image is different, that is, the amount of code generated is locally uneven, but a group of several blocks or tens of blocks can be divided into microblocks (some of the 8x8 matrices). This study focuses on the fact that when viewed as a block, the amount of code generated for each microblock is relatively uneven.

Therefore, without adaptively allocating the amount of code for each block,
Even if the method of allocating the amount of allocated code per block is fixed and the standard amount of allocated code per block is determined by allocating the target amount of code according to that allocation method, By carrying over the surplus to the allocated code amount of subsequent blocks, the generated code amount is controlled in the microblock while adapting to changes in the generated code amount of each block.

When trying to adaptively allocate the allocated code amount for each block for each image, it is necessary to calculate the statistics for each block for each image, and as a result, to memorize the standard allocated code amount for each block. However, this method eliminates the need for these, and even if the compression ratio changes, it can be handled with the same hardware. Therefore, the desired compression overprinting (
There is no need to prepare hardware for
It is possible to reduce the cost and size of the equipment to which it is applied.

Furthermore, the allocated code amount for a block is determined by adding the surplus or deficiency in the previous block to the standard allocated code amount, and encoding is controlled based on this, which simplifies processing and reduces processing time. can.

In compression encoding, the encoding circuit 8o having the configuration shown in FIG. The process is completed in two steps: finding the optimal quantization width for each, and performing the 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 process flow of the encoding circuit 80, the signal flow in the first pass is indicated by a dotted arrow ■, and the signal flow in the second pass 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 80.

The user sets the desired number of shots that can be taken by operating the switch 30, and the control circuit 90 selects the optimum code amount according to the set number of shots that can be taken. 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 8 x 8 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 Y component image data output in blocks of 8 x 8 pixels is input to the orthogonal transformation circuit 4, and orthogonal transformation is performed for each block (in this example, DCT, discrete cosine Conversion (Discrete Co
5jne Transform) is performed.

The DCT transform coefficients obtained by the orthogonal transform circuit 4 are input to the quantization circuit 6, while the target total code amount is output from the control circuit 18 to the quantization width prediction circuit 12.
In step 2, the initial value of the quantization coefficient α 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 input quantization coefficient α. The quantized transform coefficients are input to a variable length encoding circuit 8, and variable length encoding (Huffman encoding in this example) 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 that is not 0 (that is, valid) comes out, it is the consecutive 0 (zero) that existed immediately before it. Two-dimensional Huffman encoding is performed using the number of invalid coefficients (zero run) and the values of their valid coefficients. Also, if invalid output continues after a certain coefficient up to the 64th coefficient, EOB indicating the end of the block will be displayed.
Outputs the sign of . The variable length encoding circuit 8 performs the above encoding and outputs the code length to the code amount calculation circuit 14 each time one code is generated.

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

After completing this processing for the Y component, next
The same treatment is applied to 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 output to the quantization width prediction circuit 12, and is also output to the code amount allocation circuit 20 for the code amount for each color component and the entire image.

When the first pass encoding process is completed, the quantization width prediction circuit 12 uses the picture image code amount obtained by the first pass encoding and the target code amount given from the control circuit 18. A more suitable quantization coefficient α is preset as full'jl, ,
It is output to the ft child conversion circuit 6. In addition, the code amount allocation circuit 20
calculates the allocated code amount per block for each color component 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.

Subsequently, a second pass of encoding processing is performed on the same image data. In the second pass, the image data read out from the memory in the signal processing circuit 60 is first the Y component, then the Cr component.
The image data of each component is separated into 8x8 pixel blocks, etc., and then input to the orthogonal transformation circuit 4, where each block is subjected to orthogonal transformation (
DCT transform), whereby the DCT transform coefficients obtained by the orthogonal transform circuit 4 are input to the quantization circuit 6.

In the quantization circuit 6, D
Linearly quantize the CT transform coefficients.

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 allocated code amount per 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. Furthermore, the excess or 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, the reproduction of compressed and encoded recorded image data recorded on the recording medium 72 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 106, and a control circuit 108. The reading unit 102 can attach and detach the storage medium 71, and transfers the contents of the storage medium 71 to the interface circuit 110.
It is read out via .

The decoding circuit 104 has functional blocks as shown in FIG. That is, 112 is a Puffman decoding unit that decodes Huffman encoded data, and 114 is an inverse quantization unit that reads the data obtained by Konohuffman decoding from the storage medium 71 and performs inverse quantization based on the information on the quantization width that has been manually set. The inverse quantization unit 116 performs inverse DCT transformation on the data obtained by inverse quantization and outputs it as video signal data.
T (inverse DCT transformation) unit, and 118 is a control unit that controls 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 controls the entire playback machine body 100.
01- The reading unit 102 of the main body 100 of the playback machine
, the information on the quantization width at the time of encoding is controlled to be read out, and as a result, the information on the quantization width at the time of encoding read out from the recording medium 71 is transferred to the inverse quantization unit 1 of the decoding circuit 104.
14, and then the control circuit 108 sets the recording medium 71 to
Control is performed such as controlling the reading unit 102 in order to read the compression-encoded video signal data from the . 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 108.

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 inserted into the reading section 102 of the main body 100 of the playback device, the control circuit 108 immediately instructs the reading section 102 to read the data at the time of encoding. Control is performed to read out quantization width information. As a result, information on the quantization width at the time of encoding is read from the recording medium 71 in the reading section 102, and this information is set in the fast quantization section 114 of the decoding circuit 104. Subsequently, the control circuit 108 controls the reading unit 102 to read the video signal from the recording medium 71, so that the reading unit 102 reads the video signal from the recording medium 71.
The video signals are sequentially read out from 1 and input to the decoding circuit 104. In the decoding circuit 104 that receives this, the Huffman code is decoded in the Huffman decoding unit 112 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 l DCT unit 11
6, each block is subjected to inverse OCT transformation and restored to the original video signal. In this way, Y, Cr.

The video signals are restored in the order of Cb, output from the decoding circuit 104, and written into the buffer memory 120 in the processing circuit 10B. When writing of the video signal data for one screen is completed, the video signal data is read out from the buffer memory 12 (l) 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/A 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 corresponding compression rate, and also temporarily sets the compression rate according to this set compression rate. Using a quantization width, one screen worth of captured image data is quantized and variable length coded, and the optimum quantization width is predetermined from the code amount of the one screen worth of captured image data obtained as a result. The captured image data for one screen is quantized using the predicted optimal quantization width, and variable length coded, and when the encoded video signal is played back, it is decoded using the optimal quantization width used at the time of shooting. By doing so, encoding at a desired compression rate can be realized with one common hardware without having to provide hardware for each compression rate, and decoding of image data encoded at a similar desired compression rate can be achieved. This can be achieved using a single common piece of hardware, without having to provide hardware for each compression ratio.

In the embodiment, the encoding process consists of two passes: the first pass and the second pass.
Although we used a two-bus method that completes the process in one pass, the method is not limited to this, and a method that encodes in one pass using the quantization width set based on the compression rate can also obtain a practically sufficient image. However, even better results can be obtained by repeating the first pass several more times.

Also, although we have shown an example using a memory card as the recording medium,
In addition, floppy disks, optical disks, magnetic tapes, etc. can 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 embodiments, the quantization width was set based on the target total code amount, but in applications where multiple target total code amounts are switched and used by mode, the quantization width and 1 Of course, it is also possible to prepare the allocated code amount per block 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 the total code amount 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 the predicted quantization coefficient is Quantization is performed using the 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 a memory etc., and it is calculated from the compression rate correspondence information. It is also possible to directly output quantization width information (ie, quantization coefficient or 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 optimal quantization can be performed immediately. Immediately after setting the width, the quantization circuit can quantize the image signal data using this quantization width. The same applies to the standard allocated code amount per block.

According to this configuration, the information on the optimal quantization width corresponding to various compression rates and the standard allocated code amount per block are stored in advance in a memory, etc., and this is read out in accordance with the input compression rate correspondence information. Since information on the optimal quantization width and standard allocated code amount per block can be provided by just using It becomes easy.

〔Effect of the invention〕

As described in detail above, according to the present invention, the amount of code can be controlled without the need for large-scale hardware, and
Since the encoding process can be performed in a short time, it is possible to reduce the cost and size of hardware, thereby providing an image data encoding apparatus and encoding method that are optimal 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 zigzag scanning of a block divided into 8×8 pixels, and FIG. 8 is a perspective view showing the appearance of the electronic camera body according to the present invention. FIG. 9 is an operation transition diagram for explaining the principle operation. FIG. 9 is an operation transition diagram for explaining the conventional technique. 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, 1
6... Encoding input-10, 8- cut circuit, 18.18a... Control circuit, 20... Code amount allocation circuit, 24... DCPM circuit, 30... Switch, 40... Imaging system, 48... LCD display, 6
0... Signal processing circuit, 80... Encoding circuit, 70...
... Recording system, 71 ... Recording medium, 90 ... Control circuit, 100 ... Playback main body, 102 ... Reading section, 10
4...Decoding circuit, 106...Processing circuit, 108.
...Control circuit, 110...Interface circuit, 112
... Huffman decoding section, 114... Inverse quantization section, 11
6...IDCT (inverse DCT conversion) section, +18...
control section. Applicant's representative Patent attorney Atsushi Tsuboi Figure 9 (h)

Claims (8)

[Claims] (1) Divide the image data into blocks, perform orthogonal transformation on each divided block in turn, quantize the transform output with a quantization means, and give the quantized output to a variable length encoding means to make it variable. In an encoding device that performs long encoding and encodes data for each block, when encoding the block, the amount of code generated by the encoding process in the block to be encoded and the amount of code allocated in the block. The amount of excess or deficiency of the generated code amount with respect to the allocated code amount is calculated based on the above, and the amount of excess or deficiency of this generated code amount with respect to the allocated code amount is calculated in advance.
code amount allocation means that calculates the code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block as the allocated code amount of the next block to be processed; An apparatus for encoding image data, comprising: a termination means for controlling the variable length encoding means to terminate the variable length encoding so as not to exceed an allocated code amount. (2) Divide the image data into blocks, perform orthogonal transformation on each divided block in turn, quantize the transform output with a quantization means, and give the quantized output to a variable length encoding means to perform variable length encoding. In an encoding device that performs long encoding and encodes data for each block, there is a compression rate specifying means for specifying a compression rate, and an allowable amount per screen according to the compression rate specified by this compression rate specifying means. Target total code amount, quantization width, and 1
a compression rate selection means for determining a standard allocated code amount per block; and a compression rate selection means for determining a standard allocated code amount per block; Based on this, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated, and the code amount obtained by adding the calculated excess or deficiency amount to the reference code amount per block determined by the compression rate selection means is calculated as follows. code amount allocation means for determining the allocated code amount of the block to be processed; and the variable length code for terminating the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocation means for each block. terminating means for controlling the quantization means; encoding output means for outputting the transform coefficients variable-length encoded by the variable-length encoding means as a code; and a control means for controlling quantization using the quantization width. (3) Divide the image data into blocks, perform orthogonal transformation on each divided block in order, decompose the image data for each block into components from low frequency components to high frequency components, and use this transformation output as In an encoding device that performs quantization by a quantization means, supplies this quantized output to a variable length encoding means to perform variable length encoding, and encodes data for each block, upon encoding the block,
Based on the code amount generated by the encoding process in the block to be encoded and the allocated code amount in the block, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated, and the allowance per image is calculated. The code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block predetermined according to the target total code amount, which is the code amount to be processed, is the code amount obtained as the allocated code amount of the next block to be processed. an allocation means; an abort means for controlling the variable length encoding means to abort the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocation means for each block; and the quantization. control means for controlling the means to perform quantization using a predetermined quantization width; As for the DC component, there is a DC component encoding processing unit that obtains the difference between the DC component and the previous encoding processing block and variable-length encoding this difference, and a processing of this DC component encoding processing unit. and an AC component encoding processing unit that performs variable length encoding on the AC component after the AC component is finished, and the encoding aborting means is configured to enable abort control only for the AC component encoding processing unit. An image data encoding device characterized by: (4) Divide the image data into blocks, perform orthogonal transformation on each divided block, decompose the image data for each block into components from low frequency components to high frequency components, and use this transformation output as In an encoding device that performs quantization by a quantization means, supplies the quantized output to a variable length encoding means to perform variable length encoding, and encodes data for each block, the data is encoded by the variable length encoding means. a code amount calculation means for calculating the code amount of the transform coefficients for the entire image; and a quantization width prediction means that predicts the predicted quantization width and gives the predicted quantization width to the quantization means, and when encoding the block, the amount of code generated by the encoding process in the block to be encoded and the block. The excess or deficiency of this generated code amount with respect to the allocated code amount is calculated based on the allocated code amount in code amount allocating means for determining the code amount added by the amount as the allocated code amount of the next block to be processed; an abort means for controlling the variable length encoding means to abort the quantization; and an abort means for controlling the variable length encoding means to abort the quantization; control means for controlling to perform a first encoding process to predict at least once and then to perform a second encoding process using the optimal quantization width predicted by the quantization width prediction means; 1. An image data encoding device comprising: (5) Divide the image data into blocks, perform orthogonal transformation on each divided block in turn, quantize the transform output with a quantization means, and give the quantized output to a variable length encoding means to make it variable. In an encoding device that performs long encoding and encodes data for each block, there is a compression rate specifying means for specifying a compression rate, and an allowable amount per screen according to the compression rate specified by this compression rate specifying means. compression ratio selection means for determining a target total code amount, a provisionally determined quantization width, and a reference allocated code amount per block; and a code for the entire image of transform coefficients encoded by the variable length encoding means. a code amount calculating means for calculating the amount of code, and predicting an optimal quantization width from the code amount of the entire image calculated by the code amount calculating means and the target total code amount, and A quantization width prediction means for giving a predicted quantization width, and a quantization width prediction means that generates a predicted quantization width based on the amount of code generated by the encoding process in the block to be encoded and the amount of code allocated in the block when encoding the block. A block that calculates an excess or deficiency of the code amount with respect to the allocated code amount, and then processes the code amount obtained by adding the calculated excess or deficiency amount to the reference code amount per block determined by the compression rate selection means. a code amount allocating means for determining the allocated code amount for each block; and controlling the variable length encoding means to terminate the variable length encoding so as not to exceed the allocated code amount allocated by the code amount allocating means for each block. a first encoding process for predicting an optimal quantization width using a predetermined provisional quantization width from the target total code amount at least once on the quantization means; and a control means for controlling the second encoding process to be performed using the optimum quantization width predicted by the quantization width prediction means. encoding device. (6) Divide the image data into blocks, perform orthogonal transformation on each divided block, decompose the image data for each block into components from low frequency components to high frequency components, and use this transformation output as In an encoding device that performs quantization by a quantization means, supplies the quantized output to a variable length encoding means to perform variable length encoding, and encodes data for each block, the data is encoded by the variable length encoding means. a code amount calculation means for calculating the code amount of the transform coefficients for the entire image; and a quantization width prediction means that predicts the predicted quantization width and gives the predicted quantization width to the quantization means, and when encoding the block, the amount of code generated by the encoding process in the block to be encoded and the block. The excess or deficiency of this generated code amount with respect to the allocated code amount is calculated based on the allocated code amount in a code amount allocating means that obtains the code amount obtained by adding the amount of code as the allocated code amount of the next block to be processed; a first encoding process in which the optimum quantization width is predicted by the quantization width prediction means is performed at least once, and then a second encoding process is performed using the optimum quantization width predicted by the quantization width prediction means. and a control means for controlling the execution, and the variable length encoding means has a control means for controlling the DC component of the image data for each block obtained by the orthogonal transformation, and the DC component of the previous encoding processing block. a DC component encoding processing section that obtains the difference between the two and variable-length encoding the difference; and an AC component encoding processing section that performs variable-length encoding on the AC component after the processing of the DC component encoding processing section is completed. 1. An image data encoding apparatus, characterized in that the encoding processing section is provided with a coding processing section, and the coding aborting means is configured to enable aborting control only for the alternating current component encoding processing section. (7) Divide the image data into blocks, perform orthogonal transformation on each divided block, quantize it, and variable-length code the quantized data. In the encoding method, the first step is to perform encoding processing on the data and check the amount of code for the entire image, and the amount of code required for optimization is determined from the amount of code for the entire image obtained in this first step. a second step of predicting a quantization width; a third step of quantizing each block using the predicted quantization width; and a block to be encoded when encoding the block. Based on the code amount generated by the encoding process and the allocated code amount in the block, calculate the excess or deficiency of the generated code amount with respect to the allocated code amount, and also calculate the amount of code that is allowed per image. a fourth step of determining the code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block predetermined according to the total code amount of the block as the allocated code amount of the block to be processed next; 4. A method for encoding image data, comprising: a fifth step of performing variable length encoding of each block within the amount of code allocated to each block in step 4. (8) Divide the image data into blocks, and perform orthogonal transformation on each divided block in order to decompose the image data for each block from low frequency components to high frequency components in order. In the encoding method, the data is encoded for each block by variable length encoding after quantizing the data, wherein in the variable length encoding process, the image of each block obtained by the orthogonal transformation is For the DC component of the data, the difference between the DC component and the previous encoding processing block is obtained and this difference is variable-length coded. After the encoding process for the DC component is completed, the AC component is changed. The first step is to perform long coding and check the code amount of the entire image required for optimization, and the quantization width required for optimization is calculated based on the code amount of the entire image obtained in this first step. a second step of performing prediction; a third step of performing quantization for each block using the predicted quantization width; and a third step of performing quantization for each block using the predicted quantization width; Based on the code amount generated by the processing and the allocated code amount in the block, the excess or deficiency of the generated code amount with respect to the allocated code amount is calculated, and the target total code amount, which is the allowable code amount per image, is calculated. a fourth step of determining the code amount obtained by adding the calculated surplus/deficiency amount to the reference code amount per block predetermined according to the above as the allocated code amount of the block to be processed next; Image data encoding method.