JPH11341428A - Digital still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce a recording time on a record medium without deteriorating a function of image compression. SOLUTION: The camera is provided with a compressor 51 that compresses thumbnail images and a main image, a byte number counter 53 that counts number of bytes of the compressed thumbnail images, and devices 54, 55 that calculate data for a quantization scale or a quantization table based on the byte number. The compressor 51 compresses the main imagebased on the quantization scale or the quantization table to realize fixed length bytes of the compressed main image only through one compression.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital still camera device, and more particularly to a digital still camera device capable of shortening a preparation period for compression processing of a main body image.

[0002]

2. Description of the Related Art In recent years, the spread of personal computers,
With the spread of the Internet and the like, digital still cameras that can easily process image data have become widespread.
FIG. 6 shows a simple configuration example of a digital still camera.

Image data taken in from a photoelectric element such as a CCD is input from an input terminal 10. The input image data is converted by a camera signal processing unit 11 into a next compression unit 13.
(For example, RGB, YUV). The converted data 12 is input to the compression unit 13, subjected to a predetermined compression process (for example, JPEG), and written to the recording medium 15 in an arbitrary file format.

FIG. 7 shows the principle of compression processing for keeping the number of compressed bytes at a fixed length. FIG. 7 shows a configuration example of a general compression unit. First, the camera signal processing circuit 1
1, an image signal 12 converted to an image format suitable for compression is converted into a discrete cosine transform circuit (hereinafter, DCT) 2
1 is input. The DCT circuit 21 converts an input image signal from a time axis signal to a frequency axis signal. Here, DC
Detailed description of T is omitted. The image signal 22 output from the DCT circuit 21 is input to a quantization circuit 23. The other input of the quantization circuit 23 is connected to the output of a fixed-length Q (quantization coefficient) table creation circuit 29. An output 24 of the quantization circuit 23 is input to a variable-length encoding circuit 25 such as Huffman encoding, is subjected to variable-length encoding, and is output as compressed data 26. The compressed data 26 is input to a byte counting device 27.
The byte number counting device 27 counts the number of bytes for one screen of the compressed data 26, and outputs the result to a Q scale calculating device 28.
Output to The Q scale calculation device 28 calculates how much the input byte number deviates from the expected value of the byte number of the present digital still camera device, and calculates the adjustment amount (hereinafter referred to as Q scale). Output to the fixed-length Q table creation circuit 29. The fixed-length Q table creation circuit 29 creates a new Q table from the input Q scale and the original Q table, and supplies it to the quantization circuit 23. The quantization circuit 23 follows the new Q table,
The compression amount is adjusted, and new image data is output to the variable length encoding circuit 25.

[0005] By repeating this operation, the length is fixed. FIG. 8 shows an example of the file format. Starting from SOI (Start of Image), information of a recorded image (for example, time, image file information, etc.) is first written in an area called an application area (APP). Here, the application area includes the following data. Application marker
(APP Marker), the number of bytes of the entire application area (A
PP Length), an application where various information is written,
This is information of a thumbnail image. In the next area, information of the main body image is written. These information are added and recorded as one image.

As described above, the file format is roughly divided into an application area and body data. The application area generally includes an image attribute and a thumbnail image.

[0007] Here, the thumbnail image is an index-like image of the main body image and is an image used for displaying a list or the like. Generally, the image is compressed by the same compression device as the main image with an image size that is a fraction of the main image. Also, in order to immediately reproduce the main body image without reproducing a thumbnail or the like, the exact number of bytes of the application area is recorded in the first part of the application so that the first position of the main body image can be known. Often.

FIG. 9 shows a conventional compression flow. (1) In order to obtain the number of bytes of the application area including the thumbnail, the thumbnail is compressed and the number of bytes of the thumbnail image is calculated. (2) The number of bytes of the application area is obtained by adding the number of data bytes of another application to the obtained number of bytes, and is written to a recording medium. (3) The thumbnail image is compressed again and written to the recording medium. (4) Compress the main image and calculate the number of bytes of the main image. (5) Calculate the Q scale from the obtained number of bytes. (6) The main body image is compressed again on the calculated Q scale and written to the recording medium.

Normally, a single VGA image (480 × 640 pixels in length and width) is generally used to compress the main image once.
It usually takes about 0.1 to 0.2 seconds. The same compression processing is performed on the thumbnail image, but it takes less time than the main image because the image size is small.

[0010]

In the digital still camera device configured as described above, the compression of the thumbnail is performed by two times.
Since the compression of the main body image is performed twice, it takes a long time for recording, and when a camera operation such as continuous shooting is performed, the continuous shooting speed is reduced and the performance as a camera is reduced. . Therefore, an object of the present invention is to provide a digital still camera device capable of greatly reducing the recording time without lowering the compression function.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a compression device for compressing a thumbnail and a main body image, a byte number counting device for calculating the number of bytes of the compressed thumbnail, and the byte A device for calculating a quantization scale or a quantization table from a number, compressing the main image from the calculated quantization scale or the quantization table, and fixing the fixed length of the main image by a single compression operation. It will be realized. As a result, since the compression operation of the main body image, which takes the longest time in the compression processing, is performed once, the camera function such as continuous shooting is greatly improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. Further, FIG. 1B shows the state shown in FIG.
3 shows the procedure of the compression processing operation of the device.

Hereinafter, according to FIGS. 1 (a) and 1 (b),
This embodiment will be described. Image data is input to the compression device 51 from the input terminal 50. The compression device 51 performs predetermined compression and outputs compressed image data. The output of the compression device 51 is supplied to input terminals of a recording medium recording unit 52 and a byte number counting device 53. Byte counting device 53
Is supplied to the input terminal of the Q scale calculator 54 and the recording medium recording unit 52. Q scale calculator 54
Is input from the original Q table 56 to the device 55 for creating a new Q table, and the Q table newly created by the device 55 for creating a new Q table is input to the compression ratio setting unit of the compression device 51. The compression device 51 includes a DCT circuit, a quantization circuit, and a variable length coding circuit.

The operation will be further described with reference to FIG. The description will be made assuming that the recording format recorded on the recording medium is the same as that described in the conventional example. First, the number of bytes of the thumbnail is counted by the byte number counting device 53 as in the conventional example (step a11). The counted number of bytes is written to the recording medium (step a12). Next, at the same time as writing the thumbnail to the recording medium (step a13), the Q scale calculation device 54 estimates the number of bytes of the main image from the number of bytes of the thumbnail and determines a new Q scale (steps a14 and a15). Q scale calculator 54
A new Q table is created by the device 55 from the Q scale obtained from the above and the original Q table 56, and the main body image is compressed and written on the recording medium (step a1).
6).

By performing the above processing, a new Q scale of the main body image is determined from the number of bytes of the thumbnail, and a new Q table is created by the device 55 from the Q scale and the original Q table 56. The compression processing of the main body image is only compression processing for actually writing, and the time for the entire data processing process is greatly reduced.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the original Q in FIG.
This is an example in which a Q table is directly created using the calculation result of the byte number calculator 62 instead of the table 56, the device 55 for creating a new Q table, and the Q scale calculator 54. Needless to say, it is necessary to have a Q table for thumbnail compression in the embodiments of FIGS. 1 and 2 in advance.

In FIG. 2A, image data is input to a compression device 61 from an input terminal 60. The compression device 61 performs predetermined compression and outputs compressed image data.
The output of the compression device 61 is supplied to input terminals of a recording medium recording unit 62 and a byte number counting device 63. The output of the byte number counting device 63 is supplied to the input terminal of the Q table creation device 64 and the recording medium recording unit 62.

The Q table creating device 64 creates a Q table for directly compressing the main body image using the number of bytes of the thumbnail obtained from the byte number calculating device 63 and supplies it to the compressing device 61.

FIG. 2B is a flow chart for explaining the operation of the above-mentioned device. The description will be given assuming that the recording format recorded on the recording medium is the same as that of the above embodiment. First, the number of bytes of the thumbnail is counted by the byte counting device 5.
The number is counted at 3 (step b11). In this case, a predetermined Q table is used. The counted number of bytes is written to the recording medium (step b12). Next, at the same time as writing the thumbnail to the recording medium (step b13), the number of bytes of the main body image is estimated from the number of bytes of the thumbnail, and a new Q table is determined (step b14,
b15). Then, the main body image is compressed using the new Q table and written to the recording medium (step b16).

FIG. 3 shows an example of a fixed length method. Since the fixed length is not required to take much time, it is usually performed within the time to compress one image. Therefore, several Q tables are prepared, and the size of one image is reduced.

In the case of the example of FIG. 3, two Q tables are prepared (Q table 1 and Q table 2). (A),
As shown in FIG. 3B, for example, compression is performed using only a portion indicated by oblique lines. Then, from the two obtained code amounts, the code amount actually desired is estimated by, for example, linear approximation as shown in FIG. 3C, and a new Q table is created.

FIG. 4A shows still another embodiment of the present invention. FIG. 4B is a flowchart showing the operation. An input image is input to the compression device 71 from the input terminal 70, and a compression operation is started. First, in order to determine a new Q scale for fixed length, the compression device 71 creates several types of image data patterns, and calculates the number of compressed bytes by the byte number counting device 72 using each Q table. . As one of the patterns of the image data, the same pattern as the thumbnail and the Q table 150 corresponding thereto are prepared. The other Q tables 160... 170 are Q tables applied to each pattern of the image data. First, a Q table prepared in advance is used, and then a new appropriate Q table is created by the Q scale calculator 74 and the Q table generator 140.

First, after counting the number of bytes of an image having the same pattern as the thumbnail, the byte number counting device 72 calculates the number of bytes in the application area from the number of bytes and writes the calculated number in the recording medium.

At the same time, as described with reference to FIG. 3, the Q scale calculation device 74 determines a new Q scale of the number of bytes to be obtained by using several types of patterns including a thumbnail pattern. After the compression of all the patterns is completed, the compression device 71 compresses the thumbnail image, supplies the thumbnail image to the recording medium recording unit 73, and writes it. When the writing of the thumbnail to the recording medium is completed, a new Q table is created by the Q scale generation device 140 using the obtained new Q scale, the main image is compressed and supplied to the recording medium recording unit 73. Write to the recording medium.

FIG. 4B is a flowchart showing the operation of the above embodiment. A plurality of types of image patterns of image data are created, compression processing is performed on each pattern using different Q tables, and the number of bytes when each pattern is compressed using the Q table is calculated. In each pattern, for example, a single image is divided into a grid and discrete portions are adopted. Therefore, after compression, an entire single image is estimated. This process includes a process using the same pattern as the thumbnail and a Q table for the same (step c11). The byte number counting device 72 calculates the number of bytes of the image having the same pattern as the thumbnail, calculates the number of bytes of the application area from the number of bytes, and records it on the recording medium (step c12). At the same time, the Q scale calculator 74
Determines the Q scale desired to limit the amount of compressed data from the compression result of each pattern (step c1).
3, c14). Next, the thumbnail is actually compressed this time and written on the recording medium, and then the main body image is compressed and written on the recording medium (steps c15 and c16).

FIG. 5A shows still another embodiment of the present invention. FIG. 5B is a flowchart for explaining the operation. In the embodiment of FIG. 4 described above, a new Q table is created by using the Q table that has been obtained in advance and the obtained Q scale. However, in the embodiment of FIG. 5, an apparatus that creates a completely new Q table at once is provided. 200
Is provided. This part is different from the embodiment of FIG. Therefore, the other parts are the same as those in the embodiment of FIG. FIG.
The flowchart of FIG. 4B also includes a Q table creation step c20 following step c13 as compared with the flowchart of FIG. 4B. Other steps are the same as described above.

In the digital still camera apparatus configured as described above, since the main body image can be recorded by the single-shot compression operation, the camera function such as continuous shooting is greatly improved. FIG.
In the case of the embodiment, the thumbnail image is
In the case of the conventional operation, when the conventional operation is performed, the number of thumbnails is two and the main body is twice in the simple calculation. Therefore, when the main body compression time is 1, 1/8 + 1/8 + 1 + 1 = 2.25. 8 + 1/8 + 1 = 1.25, and the compression speed is improved by a factor of 1.8. For example, if the digital still camera device according to the conventional method achieves a continuous shooting speed of 2 frames / sec, the proposed method can achieve 3.6 frames / sec, and the camera function can be greatly improved. .

[0028]

As described above, according to the present invention,
The recording time can be greatly reduced without lowering the compression function.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a calculation example for obtaining a fixed length of compressed data.

FIG. 4 is a diagram showing still another embodiment of the present invention.

FIG. 5 is a diagram showing still another embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional digital still electronic camera.

FIG. 7 is a diagram showing a compression device of a conventional digital still electronic camera.

FIG. 8 is an explanatory diagram of a recording format of a recording medium.

FIG. 9 is a diagram showing the operation of a conventional electronic still camera.

[Explanation of symbols]

51, 61, 71 ... compression device, 52, 62, 73 ... recording medium recording unit, 53, 63, 72 ... byte number counting device, 5
4, 74... Q scale calculating device, 55... Device for creating a Q table, 55, 150, 160, 170.
64, 140, 200... Q table creation device.

Claims (6)

[Claims] When recording one image, a digital still camera device that pairs image data with a thumbnail image, compresses image data in an arbitrary format, and records the compressed image data on a recording medium in an arbitrary image format. A digital still camera that uses the correlation between the number of compressed bytes and the number of compressed bytes of the thumbnail to estimate the number of compressed bytes of the main image from the number of bytes of the thumbnail and performs compression processing of the main image. apparatus. 2. A digital still camera device for recording a single image, compressing image data in an arbitrary format by pairing with a thumbnail image, and recording the image data on a recording medium in an arbitrary image format. A compression device for compressing the image, a byte number counting device for calculating the number of bytes of the compressed thumbnail, and a device for calculating the quantization scale from the number of bytes, wherein a desired quantum is calculated from the calculated quantization scale. A digital still camera device, wherein a compression table is created and a main body image is compressed by the compression device using the table. 3. A digital still camera device for recording a single image, compressing image data in an arbitrary format by pairing with a thumbnail image, and recording the image data on a recording medium in an arbitrary image format. A compression device that compresses the image, a byte number counting device that calculates the number of bytes of the compressed thumbnail, and a device that creates a quantization table from the number of bytes. A digital still camera device, wherein compression is performed by the compression device. 4. A digital still camera device for recording a single image paired with a thumbnail image, compressing image data in an arbitrary format, and recording the image data on a recording medium in an arbitrary image format. A digital still camera device, wherein an arbitrary number of compressed bytes is calculated from image data using at least one of a quantization table of thumbnails and two or more quantization tables and image patterns which are image patterns. 5. A digital still camera device for recording a single image, compressing image data in an arbitrary format by pairing with a thumbnail image, and recording the image data on a recording medium in an arbitrary image format. A compression device that compresses an image, a byte number counting device that calculates each byte number using two or more quantization tables and an image pattern created from a main image, and a device that calculates a quantization scale from the byte number Wherein at least one of the two or more quantization tables and the image pattern is the same as a recorded thumbnail and creates a quantization table from the calculated quantization scale;
A digital still camera device wherein a main body image is compressed by the compression device using the quantization table. 6. A digital still camera device for recording a single image, compressing image data in an arbitrary format by pairing with a thumbnail image, and recording the image data on a recording medium in an arbitrary image format. A compression device that compresses the image, a byte count device that calculates each byte count using two or more quantization tables and an image pattern created from the main image, and a new quantization table created from the byte count And at least one of the two or more quantization tables and the image pattern is the same as the thumbnail to be recorded, and the compression apparatus compresses the main image using the newly created quantization table. A digital still camera device characterized by compression.