JP3037961B2 - Electronic camera device and image data encoding device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic camera device and an image data encoding device.

[Conventional technology]

When an image signal captured by a solid-state imaging device represented by a CCD or the like is recorded as digital data on a recording medium such as a memory card, a magnetic disk, or a magnetic tape, the amount of data is enormous. In order to record a frame image in a limited recording capacity range, it is necessary to perform some kind of compression on the obtained image signal data. For example, in a digital electronic still camera, a photographed image is stored as digital data on a data storage medium such as a memory card or a magnetic disk instead of a silver halide film, so that the image is recorded on a single memory card or a magnetic disk device. The number of possible images must be guaranteed.

Similarly, in the case of a digital VTR (video tape recorder) or the like, a predetermined amount of frames must be recorded without being affected by the amount of image data per frame. That is, it is necessary to reliably record the required number of frames, whether a still image or a moving image.

As a method of compressing image data to cope with such a condition, a coding method combining orthogonal transform coding and entropy coding is widely known.

As a representative example, an outline of a method studied in international standardization of still image coding will be described below.

In this method, first, image data is divided into blocks of a predetermined size, and two orthogonal transforms are performed for each of the divided blocks.
Performs a dimensional DCT (Discrete Cosine Transform). Next, linear quantization according to each frequency component is performed, and Huffman coding is performed on the quantized value as entropy (information amount per unit report) coding. At this time, the difference value between the DC component and the DC component of the neighboring block is Huffman-coded. The AC component scans from a low frequency component to a high frequency component called a zigzag scan, and performs two-dimensional Huffman coding from the continuous number of invalid (value 0) components and the value of the valid components that follow. . The above is the basic part of this method.

With this basic portion alone, the code amount is not constant for each image because Huffman coding, which is entropy coding, is used.

Therefore, the following method has been proposed as a method of controlling the code amount. First, the processing of the basic portion is performed, and at the same time, the total code amount of the entire screen is obtained. From the total code amount and the target code amount, an optimal quantization width for approaching the target code amount for the DCT coefficient is predicted. Next, processing after the quantization of the basic portion is repeated using this quantization width. Then, from the total code amount generated this time, the total code amount generated last time, and the target code amount, an optimum quantization width for approaching the target code amount again is predicted. If the predicted quantization width matches the previous quantization width and the total code amount generated this time is smaller than the target code amount, the process is terminated and a code is output. Otherwise, the process is repeated using the new quantization width.

The above operation will be specifically described with reference to FIG.
First, as shown in (a), one frame of image data (one frame of an image presented in the
A block of a predetermined size (for example, 8 × 576 pixels)
Divided into blocks A, B, C...
As shown in (2), two-dimensional DCT (discrete cosine transform) is performed as an orthogonal transform for each of the divided blocks, and an 8 × 8
Are sequentially stored on the matrix. When viewed on a two-dimensional plane, the image data has a spatial frequency which is frequency information based on the distribution of density information. Therefore, by performing the DCT, the image data is converted into a DC component DC and an AC component AC, and the origin position (0, 0) is displayed on an 8 × 8 matrix.
Data indicating the value of the DC component DC at position), and 0,7
At the position, data indicating the maximum frequency value of the AC component AC in the horizontal axis direction, and at the 7,0 position, the maximum AC component A in the vertical axis direction.
Data indicating the frequency value of C is further stored at positions 7 and 7, and data indicating the maximum frequency value of the AC component AC in the oblique direction are stored at the respective positions.The frequency data in the direction associated with the respective coordinate positions is stored at the intermediate position. Are stored in such a manner that ones having higher frequencies sequentially from the origin side appear.

Next, the stored data of each coordinate position in this matrix is converted into a predetermined quantization matrix and a quantization width coefficient α.
Is divided by the quantization width for each frequency component obtained by multiplying by (c), linear quantization corresponding to each frequency component is performed (c), and this quantized value is subjected to Huffman coding as entropy coding. I do. At this time, the DC component
Regarding DC, the difference value from the DC component of the neighboring block is represented by a group number (number of additional bits) and additional bits, the group number is Huffman-coded, and the obtained codeword and additional bits are combined to generate encoded data. (D1, d2, e1, e
2).

Coefficients that are also valid for AC component AC (values are not “0”) are represented by group numbers and additional bits. Therefore, the AC component AC scans from a low frequency component to a high frequency component called a zigzag scan, and the continuous number of invalid (value is “0”) components (zero run number) and
Two-dimensional Huffman coding is performed from the group number of the value of the effective component that follows, and the obtained code word and additional bits are combined to obtain coded data.

Huffman coding is the above DC component per frame image
Centering on the peak of the occurrence frequency in each data distribution of DC and AC component AC, the more this center,
This is performed by obtaining data by encoding data in such a manner that the number of data bits is reduced and the number of bits is increased toward the periphery.

 The above is the basic part of this method.

Since only the basic portion uses Huffman coding, which is entropy coding, the code amount is not constant for each image. Therefore, as a method of controlling the code amount, for example, the following process is performed.

First, the basic portion is processed using the provisional quantization width coefficient α, and at the same time, the total code amount (total number of bits) generated for the entire screen is obtained (g). From the total code amount, the target code amount, and the tentative quantization width coefficient α used, the optimum quantization width coefficient α for approaching the target code amount for the DCT coefficient is calculated by Newton − Predicted by Newton Raphson Iteration (h).

Next, using the quantization width coefficient α (i), the above-described processing after quantization of the basic part is repeated. Then, from the total code amount generated this time, the total code amount generated last time, the target code amount, the quantization width coefficient α used this time, and the quantization width coefficient α used last time, The quantization width coefficient α that is optimal for approaching the amount is predicted. Then, if the predicted quantization width coefficient α matches the previous quantization width coefficient α, and the total code amount generated this time is smaller than the target code amount, the process ends, and the current The encoded data is output and stored in the memory card (f). If not, the quantization width coefficient α is changed, and the process is repeated using the new quantization width α.

[Problems to be solved by the invention]

As described above, for example, in a digital electronic still camera or the like, the number of images that can be recorded on one memory card, a magnetic disk device, or one magnetic tape must be guaranteed. Although the data is compressed and recorded, it is desired that the image data can be compressed with high efficiency. These items are not limited to digital electronic still cameras, and are items required not only in other applications.

However, the above-mentioned compression method based on the international standard scheme pre-processes by performing image information compression, such as coding that performs orthogonal transformation typified by discrete cosine transform by blocking image data or predictive coding (DPCM). This is a method of compressing the result, quantizing the result, and then encoding the quantized output by variable-length coding represented by Huffman coding. Although the combined image data compression method can perform high-efficiency compression, it uses variable-length coding, so the code amount cannot be known until the coding is actually completed, and the code amount can be controlled. There was a problem that it was difficult. The present inventors have proposed the following method as a method for solving this problem.

One of them is to control the amount of generated code in a compression method that combines DCPM and variable-length coding. First, an image signal is sampled, and the sampled signal is stored in an image memory. The difference signal from the predicted value predicted based on the already-encoded reference pixel signal to obtain a difference signal, quantize it with a provisional quantization width, and calculate the code amount generated here. By performing the integration, the total generated code amount of one image is obtained. Next, a new quantization width is predicted from the provisional quantization width, the total generated code amount, and the target total code amount. Then, using the predicted new quantization width, DCPM, quantization, and variable-length encoding are performed to determine the total code amount. By repeating this,
The code amount is controlled by bringing the entire code amount close to the target code amount.

Another method is a compression method in which orthogonal transform and variable length coding are combined. In order to control the amount of generated code, a sampled image signal stored in an image memory is divided into blocks, and this division is performed. After performing an orthogonal transform for each of the blocks, the transform output is quantized with a provisional quantization width, and then the quantized output is subjected to variable-length coding, and the generated code amount for each block and the entire image Then, a new quantization width is predicted from the provisional quantization width, the total generated code amount, and the target total code amount. Further, an allocated code amount for each block is calculated from the generated code amount for each block, the total generated code amount, and a target total code amount. Then, the image signal of the image memory is again divided into blocks using the new quantization width,
Perform orthogonal transform, quantization, and variable-length coding.If the generated code amount of each block exceeds the allocated code amount of each block, stop variable-length coding on the way and process the next block. Move on. Thus, the code amount is controlled so that the total generated code amount of the entire image does not exceed the target total code amount.

However, as described above, compression of preprocessing is performed by an image information compression method such as encoding or predictive encoding (DPCM) that performs orthogonal transformation as represented by discrete cosine transform (DCT) by blocking image data. Then, in a method in which the result is quantized, and the quantized output is encoded by variable-length encoding represented by Huffman encoding, the total code amount is not known until the encoding is completed. It was difficult to control the compression to the optimum value in a short time. In other words, before the optimal quantization width coefficient α of the quantization is determined,
As a result of repeated trial and error, the optimum quantization width coefficient α could not be determined quickly. Determining the optimum quantization width coefficient α early is a basic proposition to satisfy a series of requirements for ending compression encoding of an image early and recording it on a recording medium without deteriorating image quality. In the case of a still camera, it becomes a division of whether the continuous shooting mode can be used or how much continuous shooting can be made, and also a division of whether or not the technique can be used for a video camera.

Accordingly, it is an object of the present invention to provide an electronic camera device and an image data encoding device capable of quickly finding an optimum quantization width and suppressing deterioration of image quality.

[Means for solving the problem]

To achieve the above object, the present invention is configured as follows. That is, an image signal obtained from an imaging system or the like is pre-processed by an image information compression unit that performs orthogonal transformation or predictive encoding, and then quantized by a quantization unit, and the quantized output is changed by a variable length encoding unit. In an apparatus configured to perform long coding and compression, firstly, means for obtaining a frequency component of the image signal and obtaining a ratio of the frequency component for each band, ratio information for each band of the frequency component and a target code Quantizing width prediction means for predicting information of an optimum quantization width from which the code amount of the image signal after compression coding can be included in the target code amount, and wherein the quantization means The information of the quantization width from the quantization width prediction means is received, and the preprocessed image signal data is quantized by the quantization width.

Secondly, a means for calculating a frequency component of the image signal and calculating a ratio of the frequency component for each band, and a method for compressing and encoding the image signal from the ratio information for each band of the frequency component and the target code amount information. The information of the optimal quantization width that the code amount of can be contained in the target code amount is predicted and given to the quantization means, and the image signal of the image signal obtained by the quantization based on the information of the optimal quantization width is obtained. The information of the optimal quantization width in which the code amount after compression encoding falls within the target code amount is again
And a quantization width prediction means for predicting and providing the quantization width to the quantization means.

Thirdly, setting means for setting the image quality, means for providing a target code amount corresponding to the image quality set by the setting means, and frequency components of the image captured by the imaging system are obtained. Means for calculating a ratio for each band, and an optimal quantization width of the code amount after compression encoding of the image signal can be included in the target code amount from the ratio information for each band of the frequency component and the target code amount information. Information that is predicted and given to the quantization means, and the code amount after compression coding of the image signal obtained by quantization based on the information of the optimum quantization width is within the target code amount. And the quantization width prediction means for predicting the information of the above again and giving the information to the quantization means.

Fourth, the image signal data for one screen is divided into blocks, and pre-processing such as orthogonal transform is performed for each of the divided blocks, and then quantization and variable length coding are performed. In this case, a means for obtaining a frequency component of the image signal, obtaining a ratio of each frequency component for each band, and outputting the information as ratio information, a means for providing information of a total code amount to be stored per image, A code amount calculating unit that receives the output of the long encoding unit, obtains the total code amount for each screen, and outputs this as calculated code amount information, and issues a statistical processing command at first, and performs the encoding process when the statistical processing is completed. Control means for issuing a command; and when executing the statistical processing command, the code amount after compression encoding of the image signal is calculated from the ratio information and the target code amount information for each frequency component band. Can fit in The information of the optimum quantization width is predicted and given to the quantization means, and the code amount of the image signal obtained by the compression based on the quantization based on the information of the optimum quantization width after the compression coding is set to the target code amount. The quantization width prediction means which predicts the information of the optimal quantization width that fits again and gives it to the quantization means at the time of execution according to the coding processing command, and the calculated code amount information at the time of execution according to the statistical processing command. Code amount allocating means for calculating the allocated code amount of each block based on information of the total code amount to be stored, and when the code processing command is executed, the calculated code amount information for each block is And an encoding discontinuing means for controlling the variable length encoding means to terminate the encoding of the block when the allocated code amount is reached.

(Operation)

According to the present invention, an image signal obtained from an imaging system or the like is pre-processed by an image information compressing unit (for example, it is subjected to orthogonal transformation such as DCT or a block is subjected to a DPCM, or the like, or is subjected to DPCM), and is then provided to a quantizing unit for In a device for performing variable-length coding on the quantized output by a variable-length coding unit, in the case of the first configuration, the unit for obtaining a ratio for each band obtains a frequency component of the image signal, Find the ratio for each. The quantization width prediction means predicts information of an optimal quantization width that enables the code amount after compression coding of the image signal to be included in the target code amount based on the ratio information of each frequency component band and the target code amount information. I do. The quantization means receives the information on the quantization width from the quantization width prediction means and quantizes the preprocessed image signal data with the quantization width.

According to this configuration, it is possible to provide an electronic camera device and an image data encoding device capable of quickly finding the optimum quantization width and suppressing deterioration of image quality.

Further, in the case of the second configuration, the quantization width prediction means uses the ratio information for each frequency band component of the image signal and the target code amount information to make the code amount after compression coding of the image signal fall within the target code amount. The information on the optimum quantization width that can be obtained is predicted and given to the quantization means, and the code amount after compression coding of the image signal obtained by the quantization based on the information on the optimum quantization width is the target code amount. Is again predicted and given to the quantization means.

According to this configuration, first, information of a quantization width that allows the code amount to be included in the target code amount is predicted, quantized using the information as the provisional quantization width information, and encoded. Again, since the optimal quantization width is predicted and the final quantization and encoding are performed, the optimal quantization width can be quickly and accurately found, and the degradation of the image quality can be suppressed. An image data encoding device can be provided.

In the third case, when the image quality is set by the setting means, the means for giving the target code amount gives the target code amount corresponding to the image quality set by the setting means. On the other hand, the means for obtaining the ratio for each band obtains the frequency component of the image signal, and obtains the ratio of this frequency component for each band. The quantization width prediction means predicts information of an optimal quantization width that enables the code amount after compression coding of the image signal to be included in the target code amount based on the ratio information of each frequency component band and the target code amount information. And gives it to the quantization means. Based on the information of the predicted quantization width, the quantization unit quantizes the quantization width using the quantization width, and the variable-length encoding unit performs variable-length encoding on the quantized output. With reference to the code amount after the compression encoding by the variable length encoding, the information of the optimal quantization width in which the code amount after the compression encoding falls within the target code amount is again predicted and the quantization means Given to
Based on this information, the image signal is again quantized, and further subjected to variable-length encoding to obtain final compressed encoded data of the image data.

According to this configuration, when the desired image quality is set, first, the information of the quantization width that allows the code amount to be within the target code amount corresponding to the set image quality is predicted, and this is estimated as the provisional quantization width information. From the result of quantization and encoding using
Again, by predicting the optimal quantization width and performing final quantization and encoding, it is possible to set the desired image quality, and quickly find the final quantization width corresponding to the set image quality with high accuracy. It is possible to provide an electronic camera device and an image data encoding device capable of suppressing deterioration of image quality.

In the fourth case, the data of the image signal for one screen is divided into blocks, and after performing pre-processing such as orthogonal transformation for each of the divided blocks, quantization and variable length coding are performed. In this encoding, when the image quality is set by the setting means, the means for giving the target code amount gives the target code amount corresponding to the image quality set by the setting means. on the other hand,
The means for determining the ratio for each band determines the frequency component of the image signal, and determines the ratio of this frequency component for each band. The quantization width prediction means predicts information of an optimal quantization width that enables the code amount after compression coding of the image signal to be included in the target code amount based on the ratio information of each frequency component band and the target code amount information. And gives it to the quantization means. Since the control means first issues a statistical processing command, the quantization means quantizes the quantization width based on the information of the predicted quantization width,
The variable length coding means performs variable length coding on the quantized output. The code amount calculation means receives the output of the variable length coding means, calculates the total code amount for each screen, and outputs this as calculated code amount information.

Then, the quantization width prediction unit refers to the code amount after the compression encoding by the variable length encoding of the image signal at the time of the statistical processing command, and optimizes the code amount after the compression encoding is within the target code amount. The information of the quantization width is predicted again and given to the quantization means. The control means then issues an encoding processing command, whereby the quantization means quantizes with the quantization width based on the information of the predicted quantization width, and the variable length encoding means changes the quantization output. Perform long encoding. The code amount calculation means receives the output of the variable length coding means and calculates the code amount. The quantization means quantizes the image signal again based on the information re-predicted by the quantization width prediction means, and further performs variable length coding to obtain final compressed and coded data of the image data. On the other hand, the code amount allocating means obtains the allocated code amount of each block based on the calculated code amount information and the information on the total code amount to be stored at the time of execution according to the statistical processing command. The code amount allocating means gives the obtained allocated code amount of each block to the coding truncation means. When the coding truncation means executes the processing according to the coding processing command, the calculated code amount information for each block indicates that block. When the amount of code allocated reaches the above, the variable length coding means is controlled so as to stop coding the block.

In short, the case of the fourth case is a two-pass method in which the processing is completed by the statistical processing and the encoding processing, and uses the coefficient α capable of giving a quantization width that can obtain a code amount close to the target code amount. Statistical processing makes it possible to find the optimal quantization width coefficient α quickly and more accurately, and uses the optimal quantization width set based on the target code amount as a provisional quantization width coefficient. Quantization of the first pass (statistical processing) is performed by using a quantization width coefficient close to, and a quantization width coefficient that can be contained in the target code amount is obtained from the total code amount obtained by the quantization, and is converted to the second code amount. The final coding is performed using the pass (coding process), but the code amount is adjusted in block units, and if the code amount in the block exceeds the allocated amount, the coding in that block is terminated. So the code amount is beautiful to the target amount Will fit in. As a result, the image data can be encoded in a short time and in a systematic manner to the full amount of the target code amount, thereby making it possible to approach the allowable code amount as much as possible, thereby minimizing lost data and improving image quality. Can be maintained.

The present invention provides an apparatus for pre-processing image data, quantizing the output, and variable-length encoding the quantized output.
Based on the frequency distribution of the target image, based on the frequency distribution of the image, the quantization width is reduced in an image having many high-frequency components, and the quantization width is increased in an image having few high-frequency components. For this purpose, an optimum quantization width is adjusted to a target code amount, encoding is quickly completed, encoding is completed, and high-precision encoding that suppresses deterioration of image quality is enabled. For this reason, in a still camera, a continuous shooting mode can be used, and a large number of continuous shootings can be performed. In addition, the technology is optimal for a video camera, and a digital electronic video camera can be realized. Become.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, to make the present invention easy to understand, a basic concept of the present invention will be described.

That is, the present invention first performs statistical processing by quantizing and encoding with a quantization width corrected by a provisional quantization width coefficient calculated in accordance with a target code amount as a first-pass processing, and performing optimal quantization. In addition to predicting the conversion width coefficient, the code amount to be allocated for each block is determined. Then, a final encoding process is performed as the process of the second pass. In the second pass, while quantizing the prediction quantization width coefficient for each block and encoding the same, the code amount of the block is set so that the code amount obtained by this encoding falls within the allocated code amount for each block. Is monitored, and when the code amount including the EOB code reaches the allocated code amount, the coding of the block is terminated and the coding of the next block is started. Also, in order to quickly converge to a value close to the target code amount, a standard quantization that can obtain a code amount close to the target code amount according to the target code amount that changes depending on the shooting mode such as the low image quality mode and the high image quality mode. The width coefficient α
This means that the function given to the pass is previously provided in the statistical processing system.

Statistical processing predicts the optimal quantization width and determines the allocated code amount for each block. The prediction of the optimum code amount coarsely reduces the code amount at the time of performing the encoding (however, with considerable accuracy). This is a process for approaching. By using this optimized quantum width in the encoding process, it is possible to approximate the target code amount. At this point, if the code amount falls within the target code amount, this processing alone is sufficient. However, if the upper limit of the data amount of one image is specified, let alone one byte, let alone one byte, The code amount cannot be exceeded. Therefore, a processing method when the overrun is required is required.

That is the determination of the allocated code amount for each block. This is for determining data to be used for fine adjustment when the code amount at the time of encoding exceeds the target code amount. Looking at the result of actually executing the encoding process at the optimal quantization width predicted in the statistical process, if it does not exceed, it may end, and if it does, it may be called post-processing. Statistical processing, encoding processing, post-processing becomes three steps, not only takes time,
Since it is necessary to save the code between the encoding process and the post-processing so that the codes having different lengths can be distinguished without joining them, it is necessary to perform fine adjustment during the encoding process. desired. However, dropping data indiscriminately leads to deterioration of image quality, and therefore must be avoided.

Therefore, in the present invention, visual effects are minimized by omitting high frequency components of each block.
However, it is impossible to determine whether or not the code amount is exceeded until the coding is completed. Therefore, in the present invention, it is determined for each block.

This is because the relative ratio of the generated code amount of each block to the code amount of each block generated when encoding is performed using the optimum quantization width or the quantization width predicted by the statistical processing is too small. This is used because it has been confirmed by experiments that it does not change. In other words, a tentative quantization width in statistical processing (this depends on the target code amount,
When coding is performed using encoding using the code amount generated in each block to a target code amount, a code for the entire image is used unless the code amount exceeds this value. A guideline "The amount does not exceed the target code amount" is set, and this guideline is used as a reference for monitoring as the allocated code amount for each block.

Once the quantization width and the allocated code amount for each block are determined in this way, the coding process is performed based on this,
Perform final encoding.

In the present invention, in the encoding process, the encoding is terminated in each block so as not to exceed the allocated code amount of the block.

In the coding of each block, a check is made so as not to exceed the guideline (the amount of allocated code) while sequentially coding from low frequency components to high frequency components. The blocks that did not exceed the end of encoding without any problem, that is, output EOB. In the block that has been exceeded in the middle, the higher frequency components are not coded, and the coding is terminated, and the coding of the block is terminated, that is, the EOB is output. At this time, since the EOB is also one of the Huffman codes, it is necessary to include the EOB within the allocated code amount.

In this way, for example, if half of the blocks terminate coding without having to be truncated, and the other half have omitted a part of a very high frequency and complete coding, very little information will be missing. In addition, the missing information can be limited to information of a high frequency component with little visual influence. With this method, encoding can be always terminated in two steps of statistical processing and encoding processing, so that the total code amount can be kept within a specified value. Deterioration of image quality can be suppressed within the range.

 An embodiment of the apparatus using the above principle will be described.

FIG. 1 shows an embodiment of a digital electronic camera having a built-in image data encoding apparatus according to the present invention, and FIG. 2 shows the configuration of an autofocus system used in the apparatus of the present invention.
FIG. 3 is a block diagram showing the configuration of an image data encoding circuit according to the present invention. The illustration and description of the mechanism of the digital electronic camera that is not directly related to the present invention is omitted.

As shown in FIG. 1, the electronic camera body 1 captures an image composed of an imaging element 4 configured using a solid-state imaging element such as a CCD and an imaging lens 16 for forming a subject image on the imaging element 4. And a signal processing system including an amplifier 6, an A / D converter 8, a buffer memory 9, and a process circuit 10 for performing predetermined signal processing on the output of the imaging system. , An encoding circuit 12 having an entropy encoding function, compressing and encoding the output of the signal processing system, and outputting image data encoded by the encoding circuit 12 and a quantization width (or information corresponding thereto). ) On a recording medium, a focus drive system 18 for driving and adjusting a focus position of a lens 16, an autofocus circuit 24 for controlling the same, and a system controller for controlling the entire system in the camera. And a half mirror 22 for guiding a part of the incident light image guided by the lens 16 to the autofocus circuit 24.

The amplifier 6 of the signal processing circuit system amplifies the video signal from the image sensor 4 and performs noise removal and the like. The A / D converter 8 converts the analog signal (video signal) output from the amplifier 6. It is to be converted into a digital signal. The buffer memory 9 is composed of a RAM or the like and has a capacity capable of storing at least one frame of image data. The process circuit 10 forms a color signal and the like, and outputs the signal in blocks of a predetermined matrix size.

 FIG. 2 shows the details of the autofocus system.

The autofocus system includes a pair of separator lenses that respectively guide an optical image (subject image) separated by a half mirror 22 provided between the lens 16 and the image sensor 4.
26, and an image sensor 28 having a two-part structure disposed behind the separator lens 26. Further, it comprises an A / D converter 30, a correlation operation circuit 32, a defocus amount detector 34, and an evaluation signal generator 36.

The image sensor 28 is divided into left and right regions at the center, and captures the optical images distributed by the pair of separator lenses 26, respectively. The output of the image sensor 28 is A /
After being A / D converted by the D converter 30, the signal is input to the correlation operation circuit 32, and then input to the defocus amount detector 34 and the evaluation signal generator 36, respectively. The output of the evaluation signal generator 36 is provided to the encoding circuit 12. The correlation operation circuit 32 calculates the cross-correlation of the divided subject images, obtains information on the interval values of the subject images from the cross-correlation of the subject images, and outputs them. The defocus amount detector 34 is for detecting a defocus amount (a defocus amount), and the defocus amount detector 34 converts the defocus amount based on the interval value of the subject image obtained by the cross-correlation. From this, the lens movement amount for focusing (just focus) is obtained and output. The focus drive system 18 functions to drive the lens 16 to the in-focus position and adjust the focus by a signal corresponding to the value of the lens movement amount output from the defocus amount detector 34.

The correlation operation circuit 32 obtains the autocorrelation of the two separated subject images. Since the two images are originally the same, this is equivalent to obtaining the autocorrelation. Therefore, hereinafter, the cross-correlation is treated as autocorrelation. The autocorrelation has a shape depending on the frequency spectrum of the image data.
For example, when there are many high frequency components, there is a sharp peak, but when there are few high frequency components, there is a gentle peak. That is, the frequency component ratio of the image is obtained from the obtained autocorrelation.

The evaluation signal generator 36 evaluates the magnitude of the high frequency component in the image signal, and the evaluation value obtained as a result is given to the quantization width prediction circuit 52 in the encoding circuit 12 and used for the quantization width setting. Is done. As the evaluation value of the evaluation signal generator 36, the value of the half width (d in FIG. 4) of the autocorrelation curve obtained by the correlation operation circuit 32 is used. Here, if the evaluation value E is large, the high frequency component is small, and if E is small, it is determined that the image has a large high frequency component. Therefore, when the value of E is large, the quantization width is set small, and when the value of E is small, the quantization width is set large, so that optimal code amount control can be performed.

The encoding circuit 12 has a configuration as shown in FIG. 3, and includes, for example, an orthogonal transformation circuit 38 that performs orthogonal transformation such as DCT (discrete cosine transformation), a quantization circuit 40 that performs linear quantization, and entropy encoding. A variable length coding circuit 42 for performing Huffman coding, a quantization width prediction circuit 52, a code amount calculation circuit 46, a code amount allocation circuit 48, a code truncation circuit 50, and a control circuit 54 that controls the inside of the coding circuit 12. It is configured.

The recording system 14 comprises a memory card having an interface circuit and an IC memory used as a recording medium. The memory card is detachable from the electronic camera body 1.

When a shutter operation button, which is a trigger switch, is pressed, a shutter function is activated and a subject image is formed on the image sensor 4, and a charge image is accumulated on the image sensor 4 corresponding to this image. By controlling the readout, a video signal can be obtained from the image sensor 4. These controls are also controlled by the system controller 20.

The image pickup system in FIG. 1 has an image pickup device 4 including an image pickup device 16 and an image pickup device such as a CCD.
An optical image formed on the image pickup device 4 by the camera 16 is converted into an image signal and output to a signal processing system. The signal processing system includes an amplifier 6, an A / D converter 8, a buffer memory 9, and a process circuit 10. The process circuit 10 converts the image signals obtained by the image sensor 6 into color signals Y, R
-Y (hereinafter, RY is abbreviated to Cr (chroma red)), BY (hereinafter, BY is Cb (chroma blue))
Gamma correction, white balance processing, and the like.

The output video signal of the imaging system digitally converted by the A / D converter 8 becomes image data, which is stored in, for example, a buffer memory 9 having a capacity of one frame, read out, and given to a process circuit 10. Therefore, it is a luminance signal system and a chroma (C; color difference signal) system.
It is separated into Cr and Cb components. The image data stored in the buffer memory 9 is processed by a process circuit 10 to obtain a Y component data of the image signal, for example, in order to first perform a statistical process on a luminance signal.
To perform encoding processing on the Y component data,
When the processing is completed, the data processing of the chroma Cr and Cb components is processed, and then the coding processing is performed.

The signal processing system has a blocking function, and image data (for one frame or one field) for the Y component and for the Cr and Cb components that are read from the buffer memory 9 and obtained by the process processing are stored in a predetermined format. Can be performed. Here, the block size is 8 × 8 as an example, but this block size is not limited to 8 × 8, and the block size may be different between Y and C (chroma system).

In the present embodiment, the data of the luminance system Y is read out and divided into blocks, which are provided to a subsequent processing system to perform statistical processing on the Y component data. When the statistical processing is completed,
Next, in order to enter the statistical processing for the data of the chroma Cr and Cb components, the reading of the data of the chroma Cr and Cb components and the blocking are started. In the chroma blocking, it is assumed that all the image data of the Cr component are firstly blocked, and then the image data of the Cb component is blocked.

The encoding circuit 12 has the configuration shown in FIG. Third
In the figure, reference numeral 38 denotes an orthogonal transformation circuit which receives each image data input as a block and performs two-dimensional orthogonal transformation on the image data for each block. As the orthogonal transform, cosine transform, sine transform, Fourier transform, Hadamard transform and the like can be used. By performing the orthogonal transform, image data as a transform coefficient is obtained.

Numeral 40 denotes a quantization circuit, which receives image data (transformation coefficient) output from the orthogonal transformation circuit 38, in the first quantization, sets a predetermined quantization width for each frequency component, and switches to a shooting mode. Quantization of the transform coefficient is performed with the quantization width corrected by multiplying by the quantization width coefficient α preset in accordance with
In the third round, quantization is performed using the optimum quantization width coefficient α determined in the previous processing.

Reference numeral 42 denotes a variable-length encoding circuit. The variable-length encoding circuit 42 performs variable-length encoding (entropy encoding) on the quantized output output from the quantization circuit 40. Huffman coding, arithmetic coding and the like are used as variable length coding.
Since entropy coding is variable-length coding, the code amount for each block, the code amount for the entire image, and the like change for each image. Although what kind of entropy coding is used is not directly related to the present invention, an example using Huffman coding will be described here.

The variable length coding circuit 42 scans from the low frequency component to the high frequency component by a method called zigzag scanning 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 shown in FIG. 9 is obtained by Huffman-encoding the difference value between the DC component of the block immediately before and entropy-encoded and output. For the AC component [AC], look at the conversion coefficients in order from the second to the 64th in the scanning order in FIG. 9, and if a conversion coefficient that is not 0 (ie, a valid coefficient) comes out, it exists immediately before that. An operation of performing two-dimensional Huffman encoding on the number of consecutive 0 (invalid) coefficients (zero run) and the value of the effective coefficient is output. When an invalid coefficient continues from a certain coefficient to the 64th coefficient, an EOB (end of block) code indicating the end of the block is output. Also, when the censoring signal is input, the coding is terminated, and EOB is added and output. Then, the code amount generated for the block is output to the code amount calculation circuit 46.

The code amount calculation circuit 46 calculates the code amount of each of the input Y, Cr, and Cb components for each block and integrates the code amounts.
The code amount data of each block of each component of r and Cb is collected, and the code amount of the entire image is calculated.The code amount data of the entire image is output to the quantization width prediction circuit 52, and the code amount of each block is calculated. The data of the amount and the code amount of the entire image is output to the code amount allocating circuit 48.

At the start of the first pass, the quantization width prediction circuit 52 receives information on the target code amount from the system controller 20 and uses the code amount information to obtain the quantization width coefficient α using the relationship of Equation (1) described later. , And outputs it to the quantization circuit 40. Prior to the start of the second pass, the code amount calculation circuit 46
For example, the Newton-Raphson iterative method (Newton-Raphson iterat) is used to calculate the code amount of the entire image input from the above and the target code amount which is the maximum allowable data amount per image.
ion), the optimum quantization width coefficient α for approaching the target code amount is predicted in consideration of the quantization width coefficient actually used this time.

The code amount allocating circuit 48 calculates the code amount of each block from the code amount of the image data for each block input from the code amount calculating circuit 14, the code amount of the entire image, and the target code amount, and calculates the code amount. The signal is output to the termination circuit 50.

In this calculation method, for example, the target code amount is proportionally distributed based on the ratio of the code amount for each block. For example, the code amount of a certain block is multiplied by the target code amount, and the result is divided by the code amount of the entire image to determine the allocated code amount of the block. As a result, the allocated code amount of each block is appropriately suppressed when the code amount is small according to the actual code amount in the block,
Blocks with a large code amount are allocated accordingly.

The code amount allocating circuit 48 has a code amount information table and a block allocated 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 calculating circuit 46. The code amount of each block input from the code amount calculation circuit 46, the code amount of the entire image, and the target code amount are calculated to calculate the allocated code amount of each block, and the data of the calculated allocated code amount of each block is calculated. Is stored in the block allocation code amount data table.

The allocated code amount for each block in the block allocated code amount data table is given to the coding truncation circuit 50 when the block is subjected to entropy coding processing.

The coding truncation circuit 50 subtracts the code amount of each block from the code amount allocation circuit 48 from the allocated code amount, and the remainder of the allocated code amount becomes smaller than the total code amount of the code amount to be transmitted and the code of EOB. In this case, it has a function of outputting an abort signal and supplying it to the variable length encoding circuit 42 to terminate the encoding of the block.

Therefore, the encoding truncation circuit 50 refers to the allocated code amount, and if the input code amount to be transmitted and the code of the EOB are transmitted but the allocated code amount does not exceed the allocated code amount, the truncation is not performed, and the block of the block is not performed. The operation of terminating the encoding and subtracting the code amount to be transmitted from the allocated code amount of the block is performed.

Reference numeral 44 denotes a code output circuit. The code output circuit 44 connects the variable-length codes input from the variable-length coding circuit 42, and is configured by a recording medium such as a memory card. It functions to write to the recording system 14.

In this system, statistical processing is first performed using a quantization sub-coefficient α of an initial standard determined according to a shooting mode (first pass), and the amount of information for each block required for optimization and the entire image Then, a process for performing optimized coding based on the information obtained by the statistical processing is started (second pass).

Therefore, first block the image, quantize the elements of the blocked image using a standard quantization width factor α, entropy encode the transform coefficients obtained by the quantization, and this entropy Prediction of the coding width coefficient α necessary for obtaining an optimum code amount from the code amount information of each element of each block obtained by encoding and the code amount information of the entire image, and determination of the allocated code amount for each element of each block Using the prediction quantization width α for the elements of the blocked image, by shifting to the processing mode of the optimal coding for the processing target image based on these, , The entropy coding of the transform coefficients obtained by this quantization, and the output processing for storing all the codes of the image to be processed. Its overall control managing shall we have to carry out by the system controller 20 in FIG. Note that such a function of the system controller 20 can be easily realized by using a microprocessor (CPU).

 The above is the configuration of the encoding circuit 12.

The recording system 14 in FIG. 1 includes an interface circuit and a recording medium detachably connected to the interface circuit.
The image data and the quantization width (or the information corresponding to the image data) encoded and output by are recorded on a recording medium via an interface circuit.

Next, the operation of the present apparatus having the above-described configuration will be described. First, a basic operation will be described with reference to FIG. When the camera user uses the camera, the user selects and sets a desired image quality mode from among standard image quality, high image quality, low image quality, and the like. Thereby, according to the setting, the optimal code amount corresponding to the image quality mode is output from the system controller 20, and is supplied to the encoding circuit 12 as target code amount setting information.

Next, when a trigger switch, which is a shutter button, is pressed to perform photographing, first, the autofocus system functions by the system controller 20, and control of focusing is started. That is, the subject image incident from the photographing lens 16 is separated by the half mirror 22 into the image sensor 4 side and the separator lens 26 side. In the separator lens 26, this subject image is further distributed to each of the left and right regions of the image sensor 28 to form an image. Since the image sensor 28 is divided into left and right regions with the center as a boundary, the image sensors 28 respectively capture the optical images distributed by the pair of separator lenses 26. The image signal output from each area of the image sensor 28 is subjected to A / D conversion by the A / D converter 30, and then the correlation operation circuit 32
Is input to

The correlation operation circuit 32 obtains the autocorrelation of the subject image using the input, and obtains information on the interval value between the subject images from the autocorrelation of the subject image. The autocorrelation has a shape depending on the frequency spectrum of the image data, and the frequency component ratio of the image can be obtained from the obtained autocorrelation. Correlation circuit
Information on the subject image interval value obtained by 32 is supplied to a defocus amount detector 34, and an autocorrelation output is supplied to an evaluation signal generator 36.

Then, the defocus amount detector 34 calculates a defocus amount (a defocus amount) based on the obtained distance value between the subject images, and calculates a lens movement amount for focusing (just focus) based on the defocus amount. Find and output. A signal corresponding to the value of the lens movement amount output from the defocus amount detector 34 is sent to the focus drive system 18, and the focus drive system 18 thereby drives the lens 16 to the in-focus position to perform focusing.

When the focus control ends, the system controller 20
Immediately starts the control of each element so as to start the processing of imaging and image compression.

That is, the evaluation signal generator 36 of the autofocus system obtains the half-value width of the autocorrelation curve based on the autocorrelation from the correlation operation circuit 32, and outputs this as the evaluation value E to the quantization width prediction circuit 52.

On the other hand, the subject image formed on the image sensor 4 is converted into an image signal by the image sensor 4 and input to a signal processing system. Then, after being amplified by the amplifier 6 in the signal processing system and A / D converted by the A / D converter 8, the data is temporarily stored in the buffer memory 9. When one frame is held, the held image signal is read out from the buffer memory 9 and sent to the signal processing system process circuit 10 where processing such as band correction and color signal formation is performed. Is performed.

Here, in this embodiment, since the subsequent encoding process is performed in the order of the Y (luminance), Cr, and Cb (all color difference) signals, the color signal formation is also performed accordingly. That is, the image signal is read out after being blocked in an 8 × 8 matrix, and the process circuit 10 extracts the Y component, the Cr component (RY component), and the Cb component (BY) from the blocked image signal data. Component), the signals of these color components are separated, and gamma correction and white balance processing are performed.

That is, in the process circuit 10, the buffer memory 9
Is separated into a Y component as a luminance signal system and Cr and Cb components as a chroma (C: color difference signal) system. The image data stored in the buffer memory 9 is processed by a process circuit 10 to obtain Y component data of the image signal, for example, in order to first perform statistical processing on a luminance signal, and the obtained Y signal is supplied to an encoding circuit 12. Then, the encoding process is performed on the Y component data, and when the process is completed, next, the process process is performed on the chroma Cr and Cb component data, and then the encoding process is performed.

As described above, the process circuit 10 has a blocking function, and the image data (1) for the Y component and the Cr and Cb components obtained from the buffer memory 9 and processed by the process are obtained.
(For one frame or one field) can be divided into blocks of a predetermined size. Here, the block size is 8 × 8 as an example, but the block size is not limited to 8 × 8.
Further, the block size may be different between Y and C (chroma system).

In this way, the luminance system Y data in the image signal data for one image is read out and made into a block, and given to a subsequent processing system to perform all the blocking and statistical processing on this Y component data, After the summation process is completed, the process starts reading and blocking the data of the chroma Cr and Cb components so as to start the statistical process for the data of the chroma Cr and Cb components. Chroma blocking first
All block processing is performed on the Cr component image data, and thereafter, the Cb component image data is blocked.

Image signal data of each color component in an 8 × 8 matrix block image signal separated by the process circuit 10 is input to the encoding circuit 12. Thus, image data for one frame (or one field) is
The image data is divided into blocks having the predetermined size and sequentially input to the encoding circuit 12. The image signal of each color component processed by the process circuit 10 may be stored in the buffer memory 9 for each of Y, Cr, and Cb components, and read and used in the subsequent processing.

The encoding circuit 12 supplies this data, which has been blocked and input from the signal processing system, to the orthogonal transformation circuit 38. Then, the orthogonal transform circuit 38 performs a two-dimensional orthogonal transform by, for example, a discrete cosine transform (DCT) for each block on the input image data (hereinafter, referred to as block image data) that is divided into blocks.

This orthogonal transformation is called cosine transformation, sine transformation,
Fourier transform, Hadamard transform, and the like. In the case of cosine transform, for example, a certain waveform is divided into frequency components, and this is represented by cosine waves of the same number as the number of input samples.

The orthogonally transformed block image data (transformation coefficients) are stored at corresponding frequency component positions on an 8 × 8 matrix in a buffer memory (not shown). This is stored in a matrix having a relationship in which the frequency increases as the distance from the position increases), and this is input to the quantization circuit 40.

Then, the quantization circuit 40 performs the first pass (first pass) quantization on the block image data (transform coefficients).
In the first quantization, the quantization matrix calculated by the quantization width prediction circuit 52 is applied to a predetermined quantization matrix for each frequency component (frequency components are determined corresponding to each matrix position of the block). The transform coefficient is quantized (linearly quantized) with the quantization width multiplied by the width coefficient α (FIG. 10 (h1, i)). The quantization matrix at this time may be the same for each of the luminance system and the chroma system, but a good result is obtained by a method of setting a quantization matrix suitable for each.

Note that the quantization width prediction circuit 52 obtains the target code amount corresponding to the image quality mode given from the system controller 20 corresponding to the image quality mode set by the user when shooting, and the evaluation signal generator 36 of the autofocus circuit 24. A standard (temporary) quantization width coefficient α set corresponding to the half-width E of the autocorrelation of the image and the frequency component ratio of the image is used.

The quantized block image data (transformation coefficient) is input to the variable length encoding circuit 42 under the control of the control circuit 54,
Here, variable-length coding (entropy coding; Huffman coding in this example) is performed. The variable length coding circuit 42 performs a zigzag scan of the quantized and inputted transform coefficients in the order shown in FIG. 9 to scan from a low frequency component to a high frequency component. That is, the transform coefficients are stored in a 8.times.8 matrix corresponding to the frequency components. Since the frequency is lower as the position is closer to the origin, zigzag scanning enables scanning from a lower frequency component to a higher frequency component.

Since the first data in the scanning order in FIG. 9 is the DC component DC, the data of the DC component DC is the difference value between the DC component DC of the block (the immediately preceding block) on which entropy encoding was performed immediately before. The diff-DC is Huffman-coded (FIGS. 10 (d1) and (e1)).

The AC component AC is from the second in the scanning order in Fig. 9.
Look at the transform coefficients in order up to the 64th, and when a transform coefficient that is not 0 (ie, valid) comes out, the number of consecutive 0 (invalid) coefficients that existed immediately before (zero run) and its validity Two-dimensional Huffman coding is performed with the coefficient values ((d2), (e2)).

Further, the variable length encoding circuit 42 gives an EOB (end of block) code indicating the end of a block when an invalid coefficient continues from a certain coefficient to the 64th coefficient continuously. Then, the code amount generated for the block is output to the code amount calculation circuit 46 (g1). Then, such processing is executed for all blocks of one image.

When such processing for the Y component is completed, similar processing is performed for each of the Cr and Cb components.

On the other hand, the code amount calculating circuit 46 calculates the code amount of each block of the Y, Cr, and Cb components and calculates the code amount of each of the Y, Cr, and Cb components in order to calculate the code amount of the entire Y image of the Y, Cr, and Cb components. The amount is integrated (g2), and the code amount data for each block is output to the code amount allocating circuit 48. The code amount allocating circuit 48 writes the code amount data of each block as code amount information of the corresponding block position in the code amount information table.

Then, at the stage when the Huffman encoding process for all the Y, Cr, and Cb components has been completed for all blocks of one image, the code amount calculation circuit 46 is controlled by the system controller 20.
Is the quantization width prediction circuit
At the same time, the data of the code amount of the entire image is output to the code amount allocating circuit.

The quantization width prediction circuit 52 obtains, for example, Newton- based on the input code amount data of the entire image and the target code amount data.
Using the Raphson iteration method, an optimal quantization width coefficient α for approaching the target code amount is predicted based on the actually used quantization width coefficient (FIG. 10 (h2)).

Further, the code amount allocating circuit 48 determines the allocated code amount of each block from the input code amount of each block, the code amount of the entire image, and the target code amount, for example, by using the ratio of the code amount of each block to the target. The code amount is calculated by, for example, proportional distribution.
Figure 10 (h3). Specifically, to determine the allocated code amount of a block, the code amount of the block is multiplied by the target code amount, and the result obtained by dividing the result by the code amount of the entire image is used as the allocated code amount. I do. Then, the data of the calculated allocated code amount of each block is stored in the block allocated code amount data table. The data of the allocated code amount for each block in the block allocated code amount data table is supplied to the coding truncation circuit 50 when the corresponding block is subjected to entropy coding processing in the second (second pass) processing. become.

Thus, the first pass, that is, the first encoding (statistical processing) for determining the code amount to be allocated to each block and optimizing the quantization width is completed.

Next, the process enters the second pass. The processing of the second pass is the second encoding (encoding processing), and is the processing of obtaining the final encoded output optimized to be within the target code amount.

This process is first performed for the Y component, and is performed for the Cr and Cb components after the Y component is completed. That is, first, image data is divided into blocks and read, and the Y component (luminance system) image signal data extracted and output from the signal processing system process circuit 10 is encoded.
Input 12 (a). The input block image data is input to the orthogonal transform circuit 38 in the encoding circuit 12, where the orthogonal transform is performed again (b). The transform coefficient obtained by this orthogonal transform is input to the quantization circuit 40, where the quantization is performed again (c). However, the quantization width coefficient α used at this time is the optimum quantization width coefficient α of the prediction calculated by the quantization width prediction circuit 52 in the previous pass. That is, the quantization width coefficient α is a more suitable quantization width coefficient α predicted from the image code amount obtained by the statistical processing as the first pass process and the target code amount given in advance by the system controller 20.

Next, the transform coefficient of the quantized block image data is
It is input to the variable length encoding circuit 42. In the entropy coding, as in the case of the statistical processing, among the transform coefficients of the block image data, first, the difference value diff-DC of the DC component DC is Huffman-coded ((d1), (e1)), and then the AC component AC Are sequentially extracted by zigzag scanning to perform two-dimensional Huffman coding ((d2), (e2)).

However, every time a Huffman code is generated for one element (one position in the matrix), the code amount allocating circuit 48 sends the allocated code amount to be transmitted at the element position stored in the block allocated code amount data table. Is output to the coding truncation circuit 50.On the other hand, the coding truncation circuit 50 does not exceed the allocated code amount even if the code amount to be transmitted and the code of EOB are transmitted based on the allocated code amount of each block. In this case, a process of reducing the amount of code to be transmitted from the amount of code allocated to the block without performing a truncation signal is performed. And
When the total code amount of the code amount of the block to be transmitted and the code of the EOB exceeds the remaining code amount of the allocated code amount, the coding cutoff circuit 50 sends the cutoff signal to the variable length coding circuit 42. Output, and terminate the Huffman coding of the block. Then, the variable length encoding circuit 42 shifts to the Huffman encoding of the next block obtained from the quantization circuit 40.

Therefore, the variable length encoding circuit 42 outputs the converted Huffman code to the code output circuit 44 until the truncation signal is input from the encoding truncation circuit 50, and outputs the Huffman codes for all the elements of the matrix before the truncation signal is generated. When the encoding is completed, the variable length encoding circuit outputs the code of the EOB to the code output circuit. Also, if the truncation signal is input before Huffman coding for all elements of the matrix is not completed, the variable length coding circuit 42 outputs the EOB code to the code output circuit 44 instead of the code. become. The code output circuit 44 temporarily stores the coded data.

Then, the variable length encoding circuit 42 shifts to the Huffman encoding of the next block obtained from the quantization circuit 40.

Such an operation is repeated, and the processing of all the blocks of the image of one screen is completed, thereby completing all the encoding processing. When such processing for the Y component is completed, processing for chroma-based components (Cr, Cb) is then started in the same manner. Also in the processing of the chroma component, the quantization circuit 40 uses the optimum quantization width coefficient α of the prediction calculated by the quantization width prediction circuit 52 in the previous pass.

When the processing of the second pass is completed for all the blocks of the image for one screen for the chroma components, all the encoding processes are completed.

At the end of this, the code output circuit 44 outputs the optimized Huffman encoded data for one image to the recording system 14,
The data is written in a storage medium such as a memory card in the recording system 14 (f). This is performed by the output of the code output circuit 44. The code output circuit 44 writes the data by connecting the variable-length Huffman codes from the variable-length coding circuit 42 to the memory card as a storage medium. This code output circuit
Writing to the storage medium by the output of 44 may be performed collectively at the stage when the second pass is completed. However, when the first pass is completed and the second pass is executed, a variable-length Huffman code is written. The results of the connection may be written to the storage medium as soon as they are collected in units of one byte or several bytes.

Prior to this, the code output circuit 44 writes the optimal quantization width coefficient α used for encoding in the header portion of the storage data of the encoded image, and leaves it as a clue at the time of reproduction.

As described above, in the present apparatus, when the image quality is specified, the provisional quantization is performed based on the total code amount per target image (target code amount) determined according to the specified image quality and the evaluation signal from the autofocus circuit 24. The width is calculated, and statistical processing is performed using the calculated provisional quantization width (first pass),
Based on the data, an optimum quantization width is predicted, and then the predicted quantization width is used, quantized and coded to obtain final coded image data (second
Pass), thereby making the code amount in the encoding process closer to the target code amount, and further determining the allocated code amount of each block so that the code amount in the encoding process does not exceed the target code amount. This is an important point of the present invention. Therefore, the present invention is not limited to the block size, the type of orthogonal transform, the type of entropy coding, and the like used in the present embodiment. Further, the image data buffer memory may be provided between the orthogonal transform circuit 38 and the quantization circuit 40. In this way, the process of blocking and orthogonal transform in the encoding process can be omitted. However, to maintain accuracy, in this case,
The size of the image memory increases. Further, the processing may be performed before the A / D conversion, and may be digitized thereafter. Further, in the present apparatus, entropy coding for each block is performed from the low-frequency component side, and high-frequency components having a relatively small effect on image quality are coded and used within a range where the allocated code amount has a margin. Therefore, it is possible to perform encoding with high compression while minimizing deterioration of image quality.

The above-described present invention having the structure shown in FIGS. 1 to 3 basically determines the frequency distribution of image data using an autofocus system normally provided in an electronic still camera, and uses this to obtain a linear quantum The initial value of the quantization width of the quantization is determined, and the provisional quantization width of the first pass is determined by the evaluation value related to the frequency distribution of the image data output from the autofocus circuit 24 and the set image quality. The first pass quantization is performed using a provisional quantization width close to the optimal quantization width set from the target code amount, and as a result,
Using the obtained total code amount data, a further optimal quantization width is predicted, and the allocated code amount for each block is obtained, and this is used for the encoding in the second pass, which is the final processing, and is used for each block. By collecting the assigned code amount, the data is compressed and encoded so as to fit exactly into the target code amount. This is based on the fact that, when statistical processing is performed using the quantization width coefficient α that can obtain a code amount close to the target code amount, the optimum quantization width coefficient α can be found quickly and more accurately, The first pass quantization is performed using a quantization width coefficient close to the optimum quantization width set based on the target code amount as a provisional quantization width coefficient, and the target code is calculated from the total code amount thus obtained. The quantization width coefficient that can be contained in the quantity is known, and this is used in the second pass to perform the final encoding.

Thus, the image data obtained by the imaging system by shooting is encoded in a short period of time with high accuracy and in the full frame of the target code amount. To minimize data and maintain image quality.
It is possible to perform quantization with high prediction accuracy and little image quality deterioration due to encoding, that is, high image quality.

In the present embodiment, the frequency distribution of image data is obtained by using an autofocus system normally provided in an electronic still camera, and the obtained evaluation value E, the target code amount, and the quantization width coefficient α of the linear quantization are obtained. The initial value of is determined.
In the above embodiment, the half value width d of the autocorrelation function is used as the evaluation value E at the time of obtaining the initial value of the quantization width. However, the present invention is not limited to this method. For example, using the variance of the autocorrelation function, It is good. Further, the peak value may be P, the average value of the entire image may be A, and E = (P / A) ^-1 or the like, and various other suitable methods may be employed. Here, y indicates the autocorrelation function f (x), and c indicates the value of x that gives the peak of the autocorrelation function.

Since the reproduction system is not directly related here, it will not be described in detail, but it is roughly described as follows.

The video signal data that has been compression-encoded and recorded on the recording medium is read out together with the information on the quantization width at the time of encoding, and since the video signal data is Huffman-coded, it is Huffman-decoded and quantized to a quantization coefficient. Is inversely quantized with the quantization width at the time of encoding, and the transform coefficient obtained by the inverse quantization is inversely orthogonally transformed for each block to restore the original video signal.

In this way, the video signal is restored in the order of Y, Cr, Cb,
When these are written into the buffer memory, and the writing of the video signal data for one screen is completed, the video signal data is read out from the buffer memory in the scanning order of the ordinary television signal, and is converted into the NTSC video signal by the encoder.
D / A conversion and conversion to analog signal for final 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,
In addition, since a hard copy can be obtained by giving the image data to a printing device such as a video printer and printing the image, the user can view the image in the same manner as a photograph or the like.

The encoding circuit 12 having the configuration shown in FIG. 1 performs a series of processes in the first pass in the compression encoding with a provisional quantization width obtained based on the target code amount and image frequency information. Based on the result, an optimum quantization width is obtained, a second pass is performed using the optimum quantization width, and the process is completed by two processes of obtaining final compressed and encoded data. This is to find the optimum α by the path.

The digital electronic camera has a built-in auto-focus system, and can set a desired image quality mode. By setting the image quality mode, the camera automatically sets the target code amount corresponding to this, and obtains the image with the auto-focus system. From the obtained frequency distribution information of the image, a provisional quantization width that is optimal for keeping the image within the set target code amount is obtained, and using this, the captured image data for one screen is quantized and entropy-coded. The optimum quantization width is predicted from the obtained code amount of the captured image data for one screen, the captured image data for one screen is quantized by the predicted optimal quantization width, and entropy-encoded. In this method, the optimum quantization width is obtained quickly and the photographing can be performed at high speed, but the encoding process is completed in two processes of the first pass and the second pass. Without expression, practically sufficient compression ratio control in a manner as to encode in a single pass using a quantization width determined in the first pass. In this case, since the encoding circuit 12 does not require the code amount calculation circuit, the code amount allocation circuit, and the encoding termination circuit, the circuit is simplified. Then, even when encoding is performed in a single pass, the quantization width is set based on the target code amount and the image frequency distribution information of the autofocus system, so that the quantization width is close to the optimal quantization width,
The obtained code amount can be made approximately equal to the target code amount. In this case, since the processing is completed in one time, encoding can be performed at an extremely high speed.

Alternatively, an n-pass method may be adopted in which the first pass is repeated until the total code amount reaches the target code amount, and the second pass is executed when an optimum quantization width that reaches the target code amount is found.

In the apparatus of the present invention, a floppy disk, an optical disk, or the like can be used as a recording medium in addition to a memory card. Although the camera and the playback device are shown as being separated from each other, the camera may be of an integrated type having the functions of the playback device. Although the quantization width value itself is recorded on the recording medium, the quantization width value may be converted or encoded and recorded. Preprocessing encoding
KL conversion, DPCM conversion, etc. may be used. The entropy coding may be arithmetic coding, run-length coding, or the like.

As described above, the frequency component ratio of the image data to be encoded is obtained, and the quantization width obtained thereby is set, so that the generated code amount corresponding to the image data can be obtained for any image data. , An optimal quantization width can be obtained.

By using this quantization width, when applied to encoding in which encoding is completed in one encoding process,
The obtained code amount can be made close to the target code amount, and the provisional quantization width in the first encoding process of the encoding that controls the encoding by the two encoding processes can be obtained. When applied to the setting, it has the effect of improving the prediction accuracy of the optimal quantization width, can perform high-quality encoding, the code amount is sufficiently close to the target coding process, and is within the target code amount. Until the above, when applied to the provisional quantization width setting in the first encoding process of the encoding that repeats the encoding process and the prediction of the optimal quantization width, the prediction accuracy is improved, The effect of reducing the number of repetitions until convergence and shortening the processing time required for encoding is obtained.

The above is an example of a digital electronic still camera. Since the present invention can be applied to a digital electronic video camera, an embodiment thereof will be described with reference to FIGS. 5 to 7.

This example captures a moving image, converts it to digital data,
This is an example applied to a video camera recorder that records data on a magnetic table by performing data compression by encoding. In such an apparatus, as an autofocus mechanism, a mechanism that detects the contrast of an image and controls so that the contrast is always increased is generally used.

Therefore, here, the frequency distribution of the image is detected from this mechanism and used for code amount control. FIG. 5 is a block diagram showing the configuration of the video camera recorder main body. In FIG. 5, a video camera recorder main body 100 is a solid-state imaging device 102 such as a CCD, and an image signal output by being imaged by the solid-state imaging device 102. Amplify the amplifier 104, this amplifier 1
A process circuit 106 that performs color signal formation and the like, such as generating Y, Cr, and Cb components from the output of 04, and blocks and outputs a predetermined matrix size.
A / D converters 108-Y, 108-Cr, 108-Cb for Y, Cr, Cb provided for each of the Y, Cr, Cb signals output from
Line buffers 110-Y, 110-Cr, 110-Cb for Y, Cr, Cb which are provided corresponding to the converters 108-Y, 108-Cr, 108-Cb and temporarily hold digitally converted data, It has an encoding circuit 112 for performing encoding by receiving outputs of these line buffers 110-Y, 110-Cr, 110-Cb, and a recording system 114 for recording the output of the encoding circuit 112 on a magnetic tape.

A lens 116 for forming a subject image on the image sensor 4;
It has a focus drive system 118 for driving and adjusting the focus position of the lens 116, and a system controller 120 for controlling the inside of the camera, and also receives a Y signal output of the process circuit 106 to obtain a defocus amount, and outputs a focus adjustment output. It has an autofocus circuit 122 for generating. Also in this device, the image quality can be set,
The system controller 120 has a mechanism for providing information of the target code amount determined according to the set value of the image quality to the encoding circuit 112.

As shown in FIG. 6, the auto focus circuit 122 includes a gate circuit 119 for extracting a predetermined area in the image, and an integrator 126 for integrating the output of the gate circuit 119 with an absolute value.
a, three types of bandpass filters (BPF) 128, 130, 1 each having different characteristics for filtering the output of the gate circuit 119
32, and integrators 126b, 126c, 126d, and integrators 126a, 126 for integrating the respective outputs from the BPFs 128, 130, 132 in absolute values.
b, 126c, 126d, receive the outputs of the integrators 126b, 126c, 126d, standardize the outputs of the integrators 126a, and output the respective ratios. It comprises an evaluation signal calculation circuit 136 that receives the output and determines an evaluation value based on the quantitative tendency of each component.

The focus drive circuit 118 adjusts the position of the lens 116 so that the ratio value output from the focus signal calculation circuit 134 increases in the increasing direction, and adjusts the focus.

 The encoding circuit 112 is configured as shown in FIG.

That is, three orthogonal transform circuits 114 provided corresponding to the three signals Y, Cr, and Cb input from the process circuit 106.
−Y, 114−Cr, 114−Cb, these orthogonal transform circuits 114−Y, 114
−Cr, 114−Cb, and a quantization width prediction circuit 12
5 and a quantization circuit 116-Y, 116-Cr, 116-Cb and a variable length coding circuit 118-Y, 118-Cr, 118-Cb for performing linear quantization using the optimum quantization width coefficient α obtained. A multiplexer 120 for switching and outputting the outputs of these variable length coding circuits 118-Y, 118-Cr, 118-Cb, and a variable length coding circuit 118-Y, 118-Cr,
A code amount calculation circuit 127 that receives the encoded data output by 118-Cb and calculates a code amount; a code amount allocation circuit 124 that obtains a code amount allocation value for each block of image data based on the calculated value; In accordance with the allocation amount of each block of the amount allocation circuit 124 and the calculated code amount of each block output from the code amount calculation circuit 127, encoding is performed in each block so as not to exceed the allocated code amount of the block. Variable-length encoding circuits 118-Y, 118-Cr, 118-Cb
Code amount discontinuation circuit 128 for controlling the system controller 1
The initial code amount corresponding to the set image quality given from 20 and the output of the code amount calculation circuit 127 and the evaluation signal (evaluation value) from the autofocus circuit 122 are received, and the initial initial value suitable for containing the image in the target code amount is obtained. A provisional quantization width coefficient α is obtained and supplied to the quantization circuit, and an optimum quantization width coefficient α for obtaining an image within the target code amount is obtained from the total code amount obtained by the processing in the first pass. It comprises a quantization width prediction circuit 125 to be provided to the encoding circuit, and a control circuit 130 which controls the inside of the encoding circuit 112. The output of the multiplexer 120 is sent to a recording system 114, and the recording system 114 receives this output and records it on a magnetic tape.

Next, the operation of the video camera recorder having the above configuration will be described.

The video camera recorder having such a configuration first sets a desired image quality. As a result, the target code amount corresponding to the image quality is provided to the coding prediction circuit 125 of the coding circuit 112. When the camera enters the shooting / recording state, the image signal is encoded, and at the same time, the autofocus system operates. A video signal corresponding to the subject image captured by the lens 116 is output from the solid-state imaging device 102, amplified and removed by the amplifier 104, and then sent to the process circuit 106, where it is converted into Y, Cr, and Cb signals. And output in parallel.

These signals are converted into A / D converters 118-Y, 11 corresponding to the respective signals.
The signal is converted into a digital signal by 8-Cr, 118-Cb and recorded in the line buffers 110-Y, 110-Cr, 110-Cb. Y, C
The r and Cb signals correspond to the corresponding line buffers 110-Y and 110-C, respectively.
r, 110-Cb is read out after being converted so as to be read out in block units, and the orthogonal transform circuit 114-
Y, 114-Cr and 114-Cb are input respectively. The coefficient data obtained by DCT transformation by the orthogonal transformation circuits 114-Y, 114-Cr, 114-Cb are quantized by the quantization circuits 116-Y, 116-Cr, 116-Cb. Here, the width used for quantization will be described later.

The quantized coefficient values are respectively supplied to the variable length coding circuit 118.
-Y, 118-Cr, 118-Cb and are Huffman coded. The Huffman coding method is the same as that of the above-described embodiment, and a description thereof will be omitted. The code amount generated at the time of Huffman coding is compared with the allocated code amount obtained in the previous frame stored in the code amount allocating circuit 124.
As a result of the comparison between the generated code amount and the allocated code amount, if the generated code amount exceeds the allocated code amount, the coding is discontinued by the function of the code discontinuation circuit 128.

By the above operation, the obtained signs of the Y, Cr, and Cb signals are output to the recording system 114 via the multiplexer 120 and recorded on the magnetic tape.

Next, the operation of the autofocus system will be described. The Y signal output from the process circuit 106 is gated by the gate circuit 119, and a certain area portion in the screen is cut out. The signal separated by the cut is integrated by the integrator 126a in absolute value, and the signal separated by the cut is passed through each of the BPFs 128, 130, and 132 simultaneously in parallel with the signal to obtain a specific frequency band. Integrators are separated and provided for each BPF128,130,132
Absolute value integration of each separated component is performed by 126b, 126c, and 126d. Here, the separation frequency bands of the BPFs 128, 130, and 132 correspond to the low frequency component, the intermediate frequency component, and the high frequency component of the image data, respectively.

Each integrated output of the integrators 126a, 126b, 126c, 126d is given to a focus signal calculation circuit 134, and the focus signal calculation circuit 134
The outputs of 126a, 126b, 126c and 126d are normalized by the integrated value of the integrator 126a. The focus signal calculation circuit 134 outputs a signal in a direction in which this value increases, and supplies the signal to the focus drive system 118, so that the lens 116 is constantly driven and moved in the direction of focusing.

Here, as the outputs of the integrators 126b, 126c, 126d, the highest frequency within a detectable range is selected. That is, although the integrator 126d having the highest frequency is originally used, if the image has only low frequency components, or if the lens is far away from the focus position at the start of operation, the output of the high frequency components is output. Is not obtained, the signal is switched by a multiplexer to use the intermediate frequency component or the low frequency component.

On the other hand, the outputs of the integrators 126a, 126b, 126c, 126d are also supplied to an evaluation signal calculation circuit 136, and a calculation serving as a basis for quantization width prediction is performed. That is, the evaluation signal operation circuit 13
6 normalizes the low-frequency component, intermediate-frequency component, and high-frequency component signals of the image data output from the integrators 126b, 126c, and 126d, respectively, with the integrated value of the integrator 126a, and then calculates the respective ratios. An evaluation value of the integrator 126a based on the ratio is obtained. This evaluation value is provided to the quantization prediction circuit 125.

Here, as shown in FIG. 8, when the high-frequency component and the intermediate-frequency component are relatively close to the low-frequency component, it is determined that the image has many high-frequency components, and the quantization prediction circuit 125 determines the target code amount. The quantization width is set to be large in consideration of the above. If the high-frequency component and the intermediate-frequency component are relatively low-frequency components, and if the number is extremely small, it is determined that the image has many low-frequency components, and the quantization width is set to a small value. Is given to each of the quantization circuits 114-Y, 114-Cr, and 114-Cb, and is quantized. Then, an optimum quantization width in the next pass is obtained from the total code amount information obtained from the code amount calculation circuit 127 by the processing in the first pass, and this information is used as information on the quantization width in the second pass. Circuit 114-Y, 114-Cr, 114
To -Cb.

In this way, by setting the quantization width using the frequency component ratio of the image obtained from the autofocus system of the contrast method, even in the moving picture coding apparatus, high-precision and image quality deterioration due to coding can be achieved. Less coding can be performed.

As described above, the embodiment is an example applied to the provisional setting of the quantization width in the first encoding process of the encoding for controlling the code amount in the two encoding processes. In this case, since the quantization width close to the optimal quantization width for bringing the generated code amount close to the target code amount in the image has already been used as the temporary quantization width used in the first encoding process, The prediction accuracy of the optimal quantization width after performing the first encoding process is greatly improved, and high-quality encoding can be performed.

In the present invention, the code amount is sufficiently close to the target code amount, and
Even when applied to set a provisional quantization width used in the first encoding process of the encoding that repeats the encoding process and the optimal quantization width prediction until it is within the target code amount,
As the provisional quantization width used in the first encoding process, a coding width that is already close to the optimum quantization width for bringing the generated code amount close to the target code amount in the image is used. Has the effect of reducing the number of repetitions until convergence and shortening the processing time required for encoding.

Further, the present invention can be applied to a one-pass method in which encoding is completed in one encoding process. In this case, the generated code amount becomes close to the target code amount, and the encoding process is performed at high speed. Needless to say, there is an effect that it can be performed.

Further, in the above-described embodiment, a method of obtaining a frequency component ratio using an autofocus mechanism of an imaging system in a device having an imaging function has been described. However, the present invention is not limited to this example. In the case of application to image coding, when a motion vector is determined, a method of converting to a spatial frequency and then taking a correlation may naturally use the determined spatial frequency component. A means for obtaining an independent frequency component ratio may be newly added.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and can be appropriately modified and implemented without departing from the gist thereof. For example, in each of the above embodiments, the image quality is variably set. It was made possible, but of course it could be fixed. Also, since the quantization width is determined based on the frequency distribution of the image,
If a desired region in an image is set, an image of the region is extracted, and the quantization width is determined based on the frequency distribution of the region, the specified desired region is quantized with the optimal quantization width. It becomes possible to perform compression encoding based on the specified data, and to perform processing by optimal compression encoding centering on a designated desired area.

As described above, according to the present apparatus, using the information on the frequency distribution of the image used for autofocus in the autofocus system, the optimum quantization width for bringing the generated code amount close to the target code amount can be quickly determined. By performing quantization using this quantization width, even when the coding is completed by only one coding process (one-pass method), the obtained code amount can be reduced. In the two-pass method in which the code amount can be approximated to the target code amount and the code amount is controlled by the two encoding processes, the two-pass method uses the provisional quantization width in the first encoding process (statistical process). Since the quantization width is corrected based on the code amount, it has the effect of improving the prediction accuracy of the optimum quantization width, and can perform high-quality coding, and the total code amount is sufficiently close to the target value. Until the code amount In the n-pass method in which the encoding process and the prediction of the optimal quantization width are repeated, in the encoding process (statistical process) in the first pass, it is necessary to find the optimal quantization width for keeping the code amount to the target value ( The effect of reducing the number of repetitions (until the quantization width converges to the optimum value) and shortening the processing time required for encoding is obtained.

〔The invention's effect〕

As described in detail above, the present invention pre-processes image data, quantizes the output, and performs variable-length coding on the quantized output. By controlling the quantization width based on the frequency distribution situation such that the quantization width is reduced and the quantization width is increased in an image having a small number of high-frequency components, the optimal quantization width for the quantization is adjusted to the target code amount. In addition to finding and ending encoding quickly, it enables high-precision encoding that suppresses deterioration of image quality. Therefore, in a still camera, a continuous shooting mode can be used, and a large number of sheets can be obtained. According to the present invention, it is possible to perform continuous shooting and to realize a digital electronic video camera, which is an optimal technique for a video camera. It is possible to quickly find the optimum quantization width for the image, quantize with this optimum quantization width, perform compression encoding of the image, and obtain the best image quality within the range of the target code amount. In addition, it is possible to provide an electronic camera device and an image data encoding device capable of suppressing deterioration of image quality.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electronic camera body 1 showing one embodiment of the present invention, FIG. 2 is a diagram showing the configuration of an autofocus system in the configuration of FIG. 1, and FIG. 3 is a diagram in the configuration of FIG. FIG. 4 is a block diagram showing the structure of the encoding circuit 12, FIG. 4 is a diagram for explaining autocorrelation, and FIGS. 5 to 7 are examples in which the present invention is applied to a digital electronic video camera. FIG. 5 is a block diagram showing an example of the overall configuration, FIG. 6 is a block diagram showing an example of the configuration of the autofocus circuit 122, and FIG. 7 is a block showing an example of the configuration of the encoding circuit 112 in the configuration of FIG. FIG. 8 is a diagram for explaining the relationship between each ratio of the high frequency component, the intermediate frequency component, and the low frequency component after filtering by the BPF and the quantization width setting;
FIG. 9 shows the zigzag of a block divided into 8 × 8 pixels.
FIG. 10 is a diagram for explaining a scan, FIG. 10 is an operation transition diagram for explaining a principle operation of the present invention, and FIG. 11 is an operation transition diagram for explaining a conventional technique. 1 Electronic camera body, 4,102 Image sensor, 6,104 Amplifier, 8,108-Y, 108-Cr, 108-Cb A / D converter, 9 Buffer memory, 10,106 Process circuit, 12 ... Encoding circuit, 14 ... Recording system, 16,116 ... Imaging lens, 18,118 ... Focus drive system, 20,120 ... System controller, 22 ... Half mirror, 24,122 ... Autofocus circuit, 26 ... Separator lens, 28 image sensor, 30 A / D converter, 32 correlation operation circuit, 34 defocus amount detector, 36 evaluation signal generator, 38 orthogonal transform circuit, 40 quantum , Variable-length coding circuit, 44,112 coding circuit, 46,127 code amount calculation circuit, 48 code amount allocation circuit, 50 code truncation circuit, 52 quantization width prediction circuit , 54… control circuit, 100… video camera recorder body, 110-Y, 110-Cr, 110-Cb… In-buffer, 114: Recording system, 112: Code amount calculation circuit, 116-Y, 116-Cr, 116-Cb: Quantization circuit, 118-Y, 118-Cr, 118-Cb: Variable length code 119, a gate circuit, 120, a multiplexer, 124, a code amount allocation circuit, 126, a quantization width prediction circuit, 130, a control circuit, 134, a focus signal calculation circuit, 126a, 126b, 126c, 126d: Integrator, 128, 130, 132: Bandpass filter (BPF), 136: Evaluation signal operation circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-26781 (JP, A) JP-A-1-218187 (JP, A) JP-A-3-205963 (JP, A) JP-A-4- 2291 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 5/91-5/956 H04N ^7/ 24-7/68

Claims (10)

(57) [Claims] An image signal generating means for generating an image signal; preprocessing an image signal obtained by the image capturing system by image information compression means for performing orthogonal transformation or predictive coding; In the electronic camera device, the quantized output is variable-length coded by a variable-length coding unit, and the variable-length coded image signal data is recorded and stored in a readable recording medium. Means for obtaining a frequency component of an image captured by the imaging system, for obtaining a ratio of each of the frequency components for each band, and for each of the bands of the frequency component, after compression encoding of the image signal from the ratio information and the target code amount information. A quantization width prediction unit for predicting information of an optimum quantization width capable of keeping the code amount within the target code amount; and reading the information of the quantization width predicted by the quantization width prediction unit into the recording medium. And a means for recording the preprocessed image signal data with the quantization width in response to the quantization width information from the quantization width prediction means. An electronic camera device characterized in that: 2. An imaging system for generating an image signal, wherein the image signal obtained by the imaging system is preprocessed by an image information compression unit for performing orthogonal transformation or predictive coding, and then quantized by a quantization unit. In the electronic camera device, the quantized output is variable-length coded by a variable-length coding unit, and the variable-length coded image signal data is recorded and stored in a readable recording medium. Means for obtaining a frequency component of an image captured by the imaging system, for obtaining a ratio of each frequency component for each band, and for obtaining the image signal after compression encoding from the ratio information for each frequency band and target code amount information. The information of the optimum quantization width that the code amount can be contained in the target code amount is predicted and given to the quantization means, and the information obtained by the quantization based on the information of the optimum quantization width is obtained. A quantization width prediction unit for predicting again the information of the optimum quantization width in which the code amount after the compression encoding of the image signal falls within the target code amount and providing the information to the quantization unit; Means for recording the information of the quantized width in a readable manner on the recording medium, wherein the quantizing means receives the information of the quantized width and quantizes the preprocessed image signal data with the quantized width. An electronic camera device, characterized in that: 3. An imaging system for generating an image signal, wherein the image signal obtained by the imaging system is preprocessed by image information compression means for performing orthogonal transformation or predictive coding, and then quantized by a quantization means. In the electronic camera device, the quantized output is variable-length coded by a variable-length coding unit, and the variable-length coded image signal data is recorded and stored in a readable recording medium. Setting means for setting the image quality; means for providing a target code amount corresponding to the image quality set by the setting means; obtaining a frequency component of the image captured by the imaging system; and obtaining a ratio of the frequency component for each band Means, based on the ratio information for each band of the frequency component and the target code amount information, information on an optimal quantization width by which the code amount of the image signal after compression coding can be included in the target code amount. Information obtained by the quantization based on the information of the optimum quantization width, and the code amount after compression coding of the image signal obtained by the quantization based on the information of the optimum quantization width is within the target code amount. And a means for recording the information of the quantization width predicted by the quantization width prediction means in a readable manner on the recording medium. An electronic camera apparatus, wherein the quantization means receives information on a quantization width and quantizes the preprocessed image signal data with the quantization width. 4. An image pickup system for generating an image signal is provided. Data of one screen of image signal obtained by the image pickup system is divided into blocks, and the data of one screen of image signal is divided into blocks. After pre-processing by image information compression means for performing orthogonal transformation or the like for each block, quantization is performed by quantization means, and this quantized output is subjected to variable-length coding by variable-length coding means,
In an electronic camera device configured to record and store the variable-length-encoded image signal data on a recording medium that can be read out, a frequency component of an image captured by the imaging system is obtained, and a band of the frequency component is obtained. Means for obtaining a ratio for each image and outputting it as ratio information; means for providing information on the total code amount to be stored per image; receiving the output of the variable length encoding means to obtain the total code amount for each screen; Code amount calculating means for outputting the calculated code amount information, a control means for issuing a statistical processing command first, and issuing a coding processing command when the statistical processing is completed, and a frequency when executing the statistical processing command. From the ratio information and the target code amount information for each component band, information on the optimal quantization width that allows the code amount of the image signal after compression coding to be included in the target code amount is predicted. Information on the optimum quantization width, in which the code amount after compression coding of the image signal obtained by the quantization based on the information on the optimum quantization width falls within the target code amount. A quantization width predicting means to be given to the quantizing means at the time of execution according to the encoding processing command, based on the calculated code amount information and the information of the total code amount to be stored at the time of execution according to the statistical processing instruction, Code amount allocating means for determining an allocated code amount of each block; and, when executed by the encoding processing command, when the calculated code amount information of each block reaches the allocated code amount of the block, the variable length encoding is performed. Coding discontinuation means for controlling the coding of the block to be discontinued, and information of the quantization width predicted by the quantization width prediction means recorded in the recording medium in a readable manner. And the quantization means receives the information of the quantization width and quantizes the pre-processed image data with the quantization width, and the variable-length encoding means receives the truncation command each time. An electronic camera apparatus wherein coding of a block currently being processed is discontinued. 5. An image signal generating system for generating an image signal, the image signal data for one screen obtained by this image system being divided into blocks, and the image signal data for one screen being divided. After pre-processing by image information compression means for performing orthogonal transformation or the like for each block, quantization is performed by quantization means, and this quantized output is subjected to variable-length coding by variable-length coding means,
In an electronic camera device configured to record and store the variable-length-encoded image signal data on a recording medium for readable recording, a setting unit for setting an image quality, and a setting corresponding to the image quality set by the setting unit Means for giving a target code amount to be obtained, means for obtaining a frequency component of an image captured by the imaging system, means for obtaining a ratio of each frequency component for each band, and outputting the ratio information as ratio information, and an output of the variable length coding means. A code amount calculating means for receiving the total code amount for each screen and outputting this as calculated code amount information; a control means for issuing a statistical processing command first, and issuing a coding processing command when the statistical processing is completed. In the case of execution by the statistical processing command, the code amount after compression encoding of the image signal is included in the target code amount from the ratio information and the target code amount information for each frequency component band. The information of the optimum quantization width that can be predicted is given to the quantization means, and the code amount after compression coding of the image signal obtained by the quantization based on the information of the optimum quantization width is equal to the object. A quantization width prediction unit that predicts again information on the optimal quantization width that can be accommodated in the code amount and provides the quantization unit with the quantization processing instruction when executing the code processing instruction; Code amount allocating means for calculating the allocated code amount of each block based on the information and the information of the total code amount to be stored; and when the code processing command is executed, the calculated code amount information for each block is A coding truncation unit that controls the variable length coding unit to terminate coding for the block when the allocated code amount in the block is reached; and an amount predicted by the quantization width prediction unit. Means for recording information of the quantization width in a readable manner on the recording medium, and the quantization means receives the information of the quantization width and quantizes the preprocessed image data with the quantization width. An electronic camera apparatus, wherein the variable-length encoding means terminates encoding of a block currently being processed each time the variable length encoding command is received. 6. An image signal is preprocessed by image information compression means for performing orthogonal transformation or predictive coding, and then quantized by a quantization means, and the quantized output is subjected to variable length coding by a variable length coding means. An image signal encoding apparatus configured to compress the image signal data by performing the variable length encoding, wherein a frequency component of an image obtained by the image signal is obtained, and a ratio of the frequency component for each band is obtained. Quantization width prediction for predicting information of an optimal quantization width by which the code amount of the image signal after compression coding can be included in the target code amount from the ratio information for each band of the frequency component and the target code amount information. Means for receiving the information of the quantization width from the quantization width prediction means and quantizing the preprocessed image signal data with the quantization width. Encoding apparatus of the image data, wherein. 7. An image signal is pre-processed by image information compression means for performing orthogonal transformation or predictive coding, and then quantized by a quantization means, and the quantized output is subjected to variable length coding by a variable length coding means. In the image signal encoding apparatus configured to compress the image signal by performing the variable length encoding, a unit for obtaining a frequency component of an image obtained by the image signal and obtaining a ratio of the frequency component for each band, From the ratio information for each band of the frequency component and the target code amount information, predict the information of the optimal quantization width that allows the code amount after compression coding of the image signal to be included in the target code amount, and In addition, the information of the optimum quantization width in which the code amount after compression coding of the image signal obtained by the quantization based on the information of the optimum quantization width falls within the target code amount is predicted again. And a quantization width prediction unit provided to the quantization unit, wherein the quantization unit receives the information of the quantization width and quantizes the preprocessed image signal data with the quantization width. An electronic camera device characterized by the following. 8. An image signal is pre-processed by image information compression means for performing orthogonal transformation or predictive coding, and then quantized by quantization means, and the quantized output is subjected to variable length coding by variable length coding means. In the image data encoding apparatus configured to perform variable-length encoding and compression, setting means for setting image quality; means for providing a target code amount corresponding to the image quality set by the setting means; Means for obtaining a frequency component of an image obtained by the above, obtaining a ratio of each frequency component for each band, and a code amount after compression coding of the image signal from the ratio information of each frequency band for each band and the target code amount information. Predicts the information of the optimal quantization width that can be contained in the target code amount and gives it to the quantization means, and obtains the information obtained by the quantization based on the information of the optimal quantization width. And a quantization width prediction unit for predicting again the information of the optimal quantization width in which the code amount after the compression encoding of the image signal falls within the target code amount and providing the information to the quantization unit. The image data encoding apparatus according to claim 1, wherein said quantization means receives the information of the quantization width and quantizes said preprocessed image signal data with the quantization width. 9. An image signal data for one screen is divided into blocks, and the image signal data for one screen is pre-processed by image information compression means for performing an orthogonal transformation or the like for each of the divided blocks. In the image data encoding apparatus, the quantized output is quantized, the quantized output is variable-length encoded by a variable-length encoding unit, and the variable-length encoding is performed. Means for obtaining the ratio of each frequency component for each band and outputting the ratio information as ratio information; means for providing information on the total code amount to be contained per image; and receiving the output of the variable length coding means and Code amount calculation means for obtaining the total code amount and outputting the calculated code amount information, control means for issuing a statistical processing command at first, and issuing an encoding processing command when the statistical processing is completed; At the time of execution according to the statistical processing command, the code amount after compression encoding of the image signal can be included in the target code amount from the ratio information and the target code amount information for each frequency component band. Information that is predicted and given to the quantization means, and the code amount after compression coding of the image signal obtained by quantization based on the information of the optimum quantization width is within the target code amount. Is again predicted and given to the quantization means at the time of execution according to the encoding processing command, and the calculated code amount information and the total code amount to be contained at the time of execution according to the statistical processing command Code amount allocating means for calculating an allocated code amount of each block based on the information of the above, and, when executed by the encoding processing command, the calculated code amount information for each block is used to calculate the divided code amount of the block. And a coding cutoff means for controlling the variable length coding means to stop coding for the block when the code amount is reached, and the quantization means receives the information of the quantization width and The pre-processed image data is quantized by the quantization width, and the variable-length encoding unit is configured to discontinue encoding of the block currently being processed each time the discontinuation instruction is received. Image data encoding device. 10. The image signal data for one screen is divided into blocks, and the image signal data for one screen is pre-processed by image information compression means for performing orthogonal transformation or the like for each of the divided blocks. , Quantized by quantization means, and the quantized output is variable-length coded by variable-length coding means,
In the image data encoding apparatus configured to perform variable-length encoding and compression, setting means for setting image quality; means for providing a target code amount corresponding to the image quality set by the setting means; Means for obtaining frequency components, obtaining the ratio of each frequency component for each band, and outputting the information as ratio information; receiving the output of the variable-length encoding means, obtaining the total code amount for each screen, and calculating the total code amount information. Code amount calculating means for outputting as, a control means for issuing a statistical processing command at the beginning, and issuing a coding processing command when the statistical processing is completed, and when executing the statistical processing command, a frequency component for each band. Based on the ratio information and the target code amount information, information of an optimal quantization width that allows the code amount of the image signal after compression coding to be included in the target code amount is predicted and given to the quantization unit. In addition, the information of the optimal quantization width in which the code amount of the image signal obtained by compression based on the information of the optimal quantization width after compression and encoding falls within the target code amount is predicted again to predict the code. Quantization width prediction means to be given to the quantization means at the time of execution by the quantization processing command, and, based on the calculated code amount information and the information of the total code amount to be contained at the time of execution by the statistical processing instruction, A code amount allocating means for determining an allocated code amount, and when the calculated code amount information of each of the blocks reaches the allocated code amount in the block when the encoding process command is executed, the variable length coding means Coding discontinuing means for controlling the coding of the block to be discontinued, and wherein the quantizing means receives information of the quantization width and receives the preprocessed image with the quantization width. The data is configured to be quantized, said variable length coding means coding device of the image data, characterized in that a structure to abort the encoding for the block currently being processed for each receiving the abort command.