JP3076081B2 - Image signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing apparatus suitable for a digital electronic still camera using, for example, a memory card, a magnetic disk or the like as a data recording medium.

[0002]

2. Description of the Related Art When an image signal captured by a solid-state imaging device represented by a CCD (Charge Coupled Device) or the like is recorded as digital data on a recording medium such as a memory card or a magnetic disk, the amount thereof becomes enormous. . For example, when converting an image signal into a digital signal and recording it as it is,
The data amount of one frame is a product of the number of pixels of the image sensor and several bits (for example, 8 bits) per pixel, and the number of frames that can be recorded on a recording medium is extremely limited.
Therefore, in order to record many frame images within 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 recorded as digital data on a data recording medium such as a memory card or a magnetic disk instead of a silver halide film used in a normal camera. The number of images that can be recorded on a memory card or a magnetic disk is specified, and recording of the specified number of images must be guaranteed. In addition, the time required for the data recording / reproducing process needs to be short and constant.

As a method for compressing image data satisfying the above conditions, for example, there is an encoding method. Here, as the simplest method, there is a method in which the number of pixels immediately before being encoded is used as a prediction value, the difference between this value and the value of the encoded pixel is quantized, and the data amount is reduced. This method is called an adaptive difference coding (ADPCM) method, and is often used as a compression method because it is simple and does not have a very large hardware scale. In addition, there is an adaptive discrete cosine transform (ADCT) method that converts an image signal into frequency components, performs optimal quantization for each component, and reduces the amount of data.

FIG. 2 is a block diagram of a conventional digital electronic still camera using a memory card as a data recording medium.

In FIG. 1, an image pickup device 12 converts an optical image picked up through an optical lens system 11 into an image signal. The image signal converter 13 has, for example, an A / D (analog / digital) converter, converts an image signal from the image sensor into an electric signal, converts the processed electric signal into a digital signal, and outputs the digital signal. An arithmetic control unit 14 (hereinafter, CPU) composed of a microcomputer or the like controls the image signal compression processing. The image signal compression device 15 compresses the input digital signal by the encoding method or the like. The read-only storage device (hereinafter referred to as ROM) 16 stores the image signal compression device 1
5 stores information on compression parameters used in the data compression process. The random access storage device (hereinafter, RAM) 17 temporarily stores data required during data compression processing by the image signal compression device 15. The memory card 19 records the compressed data.

Here, an image pickup device 12, an image signal conversion device 13, a CPU 14, an image signal compression device 15, a ROM 1
6. RAM 17 is the main unit 1 of the digital electronic still camera
The memory card 19 is provided in the main body 18 so as to be detachable.

Next, the actual operation of the conventional digital electronic still camera will be described.

An optical image is obtained through an optical lens system 11, and is converted into an image signal by an image pickup device 12. The image signal from the image sensor 12 is transmitted to the image signal conversion device 1.
The digital signal is converted into a digital signal by the digital signal processor 3 and is compressed by the image signal compressor 15. In order to temporarily store necessary data during the compression process, the RAM 1
7 is used. Further, the CPU 14 causes the image signal compression device 15 to read out the compression parameter from the ROM 16 and execute a data compression process based on the contents.

The data processed by the image signal compression device 15 is sequentially recorded on the memory card 18.

Since the ROM 16 is used for setting parameters, only initial parameters are read at the beginning of the compression operation. The RAM 17 is used for temporary storage. Therefore, the ROM 16 stores the RA
Since M17 is used only during the compression processing, each use time differs.

[0012]

As described in detail above,
For example, in a digital electronic still camera, the number of images that can be recorded on one memory card or magnetic disk must be guaranteed. Also, since a plurality of recording areas such as a work area and a parameter recording area are required, the circuit scale is large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points. By sharing a recording area in a recording medium with a work area and a parameter storage area, the recording area can be used in a time-efficient manner so that a RAM or the like can be used. It is an object of the present invention to provide an image signal processing device capable of reducing a circuit scale without using a ROM.

[0014]

In order to achieve the above object, an image processing apparatus according to a first aspect of the present invention includes an image compression apparatus that receives and compresses image data converted into a digital signal,
A data recording medium having a recording area shared by a work area and an image data recording area necessary for performing the compression processing, and a common mode of the work area and the image data area of the data recording medium, And control means for performing control in accordance with the compression operation. Also,
In the second invention, the work area includes a parameter area in which initial parameters necessary for compression are stored in advance and a temporary storage area for temporarily storing data required in compression processing. In accordance with an increase in image data to be provided, by overwriting the image data in the temporary storage area, a part of the work area can be transferred to the image data recording area. And the third
According to the invention, in the image processing apparatus according to the first invention,
It is characterized by further comprising an image pickup device for picking up a desired optical image, and an image signal conversion device for converting an image signal output by the image pickup device into a digital signal.

[0015]

The image signal processing apparatus according to the first aspect of the present invention compresses image data converted into a digital signal by the image data compression means and records the image data in a recording area in a recording medium.
At this time, the control means controls the common use of the work area and the image data area of the data recording medium in accordance with the compression operation of the image data compression means. Further, according to the second invention, it is possible to selectively use the work area as a parameter area in which initial parameters necessary for compression are stored in advance and a temporary storage area for temporarily storing data required in compression processing. The image data can be overwritten in the temporary storage area with the increase in the image data to be recorded by the control means. According to the third aspect, a desired optical image can be converted into an image signal, and image data converted into a digital signal can be obtained. As described above, since the parameter area and the temporary storage area are provided in the recording medium, and the recording area in the recording medium is shared by the working area and the image data recording area, the circuit scale in the main body is reduced. The recording area can be reduced and the recording area in the recording medium is not increased.

[0016]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a diagram showing a configuration of a digital electronic still camera to which an image signal processing apparatus according to one embodiment of the present invention is applied.
Lead to. The imaging element 2 captures an optical image. The image signal conversion device 3 converts a captured image signal into a digital signal. The image signal compression device 4 compresses the digital signal processed by the image signal conversion device 3. An arithmetic control unit (hereinafter, CPU) 5 composed of a microcomputer or the like controls the compression processing.

The image pickup lens 1, image pickup device 2, image signal converter 3, image signal compressor 4, and CPU 5 are housed in a camera body 6.

The memory card 7 is provided detachably with respect to the main body, and records compressed image data. The storage area of the memory card 7 is shared by the parameter area 71, the temporary storage area 72, and the image storage area 73.

The actual operation of the digital electronic still camera of the embodiment will be described below. The optical image that has passed through the taking lens 1 is first captured by the image sensor 2. And
The captured image signal is converted into a digital signal by an A / D converter included in the image signal conversion device 4. And
The digital signal is subjected to compression processing by an image signal compression device 4.

Here, as a compression method of the image data,
For example, an encoding method that combines orthogonal transform encoding and entropy encoding is used.

This method will be described briefly. First, image data is divided into blocks of a predetermined size, and a two-dimensional DCT as an orthogonal transform is performed for each of the divided blocks.
(Discrete cosine transformation). 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 performs a scan from a low frequency component to a high frequency component called a zigzag scan, and obtains a two-dimensional Huffman from the continuous number of invalid (zero value) components and the value of the valid component following the invalid component. Perform encoding.

The above is the basic part of this encoding method.

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

Therefore, there are the following methods for controlling the code amount.

First, the processing of the basic portion is performed, and at the same time, the total code amount generated for 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 part 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 re-estimating the target code amount is predicted. Then, the predicted quantization width matches the previous quantization width,
If the code amount generated this time is smaller than the target code amount, the process is terminated and the code is output. Otherwise, the process is repeated using the new quantization width.

When data is compressed by the above-mentioned encoding method, a compression parameter is selected in consideration of the data amount after compression so that the data amount of one frame falls within a predetermined value. Initial parameters for this compression are recorded in the parameter area 71 of the memory card 7 in advance, and compression processing is performed based on the initial parameters. The temporary storage area 72 is used for temporarily storing predetermined data during the compression processing. Thus, the compressed image data, that is, the compressed data, is sequentially recorded in the image recording area 73.

Here, actually, the compressed data is also overwritten in the temporary storage area 72 in the memory card 7. In this case, the temporary storage area 72 decreases each time data is written to the memory card 7, so that as the data compression proceeds, predetermined data of the compression processing can be sequentially overwritten, and even if the area is small, It doesn't matter.

These predetermined compression processes are automatically performed under the control of the CPU 5.

As described in detail above, in the image signal processing apparatus according to the present invention, a plurality of recording areas such as a work area and a parameter recording area necessary for performing compression processing of image data are provided in a data recording medium. In addition, the recording area is shared so that it can be used as an image data recording area as the recording proceeds.

Accordingly, the circuit area can be reduced, and the recording area in the memory card can be used efficiently in time according to the application, so that the recording area can be used efficiently. The scale can be reduced.

[0034]

According to the present invention, the compression processing and the recording processing of the image data can be performed by efficiently using the recording area in the recording medium for the image data. In other words, since the function of the work area provided in the circuit of the main body can be also used as the recording area, it is possible to provide an image signal processing apparatus with a reduced circuit scale of the main body.

[Brief description of the drawings]

FIG. 1 is a block diagram of a digital electronic still camera to which an image signal processing device according to one embodiment of the present invention is applied.

FIG. 2 is a block diagram of a conventional digital electronic still camera.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photographing lens 2 image pickup device 3 image signal conversion device 4 image compression device 5 CPU 6 camera body
7 Memory card, 71 Parameter area, 72 Temporary storage area, 73 Image recording area

Claims (3)

(57) [Claims] 1. An image data compression means for receiving image data converted into a digital signal and compressing the same, a predetermined work area and an image data recording area when the data compression means compresses the image data. A data recording medium having a recording area sharing the same, and control means for controlling a common mode of the working area and the image data area of the data recording medium in accordance with a compression operation in the image data compression means. An image signal processing device characterized by the above-mentioned. 2. The work area includes a parameter area in which predetermined initial parameters are stored in advance in compression and a temporary storage area in which predetermined data is temporarily stored in compression processing. 2. The image processing apparatus according to claim 1, wherein a part of the work area can be transferred to the image data recording area by overwriting the image data in the temporary storage area with an increase in the image data to be increased. Image signal processing device. 3. The image processing apparatus according to claim 1, further comprising: an image pickup device that picks up a desired optical image; and an image signal conversion device that converts an image signal output by the image pickup device into a digital signal. The image signal processing device according to any one of the preceding claims.