KR100266589B1 - Still image compressing method for digital still camera - Google Patents

Abstract

PURPOSE: A method for compressing a static image of a digital camera is provided to improve efficiency of practical use of a DRAM when pictures are continuously taken. CONSTITUTION: In an image information capture step, image information of a subject obtained by taking a picture is orderly received in frame unit so as to be different resolution according to storing capacity of a temporary memory and to store(SA1). In an image information compressing step, the image information stored in the temporary memory is processed to compress so as to store in a flash memory(SA3). The image information capture step is further comprised of the step of storing the image information separating a high resolution mode and a low resolution mode according to memory capacity of the temporary memory. The storable capacity of the temporary memory is residual capacity of the temporary memory.

Description

Still image compression method of digital still camera {STILL IMAGE COMPRESSING METHOD FOR DIGITAL STILL CAMERA}

The present invention relates to a still image compression technology of a digital still camera (DSC), and more particularly, to perform the capture and compression of the image to contribute to the continuous shooting of the image, and to support the maximum resolution in a given condition A still image compression method of a still camera.

FIG. 1 is a block diagram of a general digital still camera. As shown in FIG. 1, a CCD (CDD) 2 converting an optical signal incident from a lens 1 into an electrical signal after being reflected from a subject by photographing )Wow; A camera signal processor (3) for receiving a signal output from the CD (2) to perform a noise canceling function, an automatic gain control function, an analog / digital conversion function, and the like; A digital signal processor (4) which receives the signal converted into a digital signal from the camera signal processor (3) and processes it into various forms required by the system; A monitor (5) for displaying an image signal output from the digital signal processor (4); A timing signal generator (6) for generating various timing signals to drive the CD (2), the camera signal processor (3), the digital signal processor (4), and the like; A key input unit 7 which receives various control commands requested by the user; Each part of the system performs control of the camera unit and the memory unit according to a control command input through the key input unit 7, and performs compression and restoration operations on image signals temporarily stored in a memory such as the DRAM 9. A central processing unit (8) for overall control; A JPEG compression restorer (8A) embedded in the central processing unit (8) to perform a JPEG compression recovery function; A DRAM (DRAM) 9, which is a place for storing image data captured by photographing or data stored and restored in a compressed form in the flash memory 11; The data processed by the digital signal processing unit 4 is stored in the DRAM 9, and the stored data is read and outputted to the monitor 5 side, and when the shutter is on, the DRAM is processed according to a call command of the central processing unit 8; A gate array unit 10 for intermittently controlling data lines between (8) and the central processing unit; A flash memory (11) which is a place for storing data which is finally compressed in JPEG format by using the central processing unit (8) and an auxiliary memory (SRAM) 12; It is composed of the SRAM 12, which serves as an auxiliary memory of the CPU 8, such as serving as a recording area when storing data of the DRAM 9 or performing decompression calculation of already stored data. The operation will be described with reference to FIG. 2 as follows.

When a user photographs a desired subject with a digital still camera, the light reflected from the subject is incident through the lens 1 and converted into an electrical signal in the CD 2, and the electrical signal is converted into a camera signal processor 3. Pretreated by

That is, the camera signal processing unit 3 controls a CDS (Correlated Double Sampling) function that outputs only pure signal components from which noise is removed from the input signal components, and controls the CDS signals to maintain a constant level regardless of the change in the amount of light. An automatic gain control (AGC) function, and an analog / digital conversion function for converting the automatic gain controlled analog signal into a digital signal.

The image signal obtained through the above process is supplied to the digital signal processing unit 4 and processed into various forms required by the system, and then, by the gate array unit 10 to a temporary storage device such as the DRAM 9. Stored.

In such a state, the CPU 8 reads the data stored in the DRAM 9 by controlling the gate array unit 10 and uses the internal JPEG compression restorer 8A and the SRAM 12. After compression processing, it is stored in the flash memory 11.

The above description shows a process of processing an image captured by one shot, and in the case of continuous shooting, the process is repeated after such a process is repeated.

Thereafter, the image data stored in the compressed form in the flash memory 11 is expanded by the central processing unit 8 in the original form, stored in the DRAM 9, and then, through the digital signal processing unit 4. Since it is output to the monitor 5 side, the user can see the pictures taken continuously.

However, in the continuous shooting technique according to the prior art, there is a defect that the time interval during which continuous shooting is possible is continuously affected by image capturing, compression processing, and storage cycles repeatedly performed during continuous shooting. In addition, when shooting in the low resolution mode, only a part (about 3/4) of the entire area of the DRAM was used, and there was a defect that the utilization efficiency of the system was reduced.

Accordingly, the present invention has been made in an effort to provide a still image compression method in which the compression speed of image data during continuous shooting does not significantly affect the time interval at which continuous shooting is possible, and improves the utilization efficiency of the DRAM.

1 is a block diagram of a typical digital still camera.

2 is a continuous shooting signal flow chart according to the prior art.

3 is a basic signal flowchart of a continuous shooting still picture compression method according to the present invention;

4 is a detailed signal flowchart of a continuous shooting still picture compression method according to the present invention;

*** Description of the symbols for the main parts of the drawings ***

1: lens 2: CD

3: camera signal processor 4: digital signal processor

5: monitor 6: timing signal generator

7: key input unit 8: central processing unit

8A: JPEG Restorer 9: DRAM

10: gate array unit 11: flash memory

12: SRAM

The still image compression method of a digital still camera for achieving the object of the present invention pre-processes the image information of the subject obtained by shooting and sequentially receiving the image information of the subject in frame units under the permitted conditions and stored in a temporary memory such as DRAM A capture step; An image information compression step of sequentially reading image information stored in the temporary memory, compressing the image information in software or hardware, and storing the image information in a flash memory; The image information restoration step of decompressing the image information stored in the compressed form in the flash memory and outputting the image information to the monitor side.

The basic configuration of the digital still camera to which the still image compression method of the present invention is applied is the same as that of FIG. 1 mentioned in the related art. However, in FIG. 1, the memory array of the DRAM 9 is secured to store all the image information of each frame during continuous shooting at high resolution, and the gate array unit 10 is designed to capture an image at a low resolution. When the image data is read from the DRAM 9 for JPEG compression, the central processing unit 8 is configured so that the region can be read differently, and FIGS. 3 and 4 attached to the operation of the present invention configured as described above. If described with reference to:

When sequential photography starts, it is first determined whether to process at high resolution or at low resolution, which is based solely on the result preset by the user (SB1).

Thereafter, a series of capture processes for preprocessing the captured image and storing it in the DRAM 9 are the same as in the prior art. That is, when a user photographs a target subject using a digital still camera, the light reflected from the subject is incident through the lens 1 and converted into an electrical signal in the CD2, and the electrical signal is converted into a camera signal. After being preprocessed by the processing unit 3, it is supplied to the digital signal processing unit 4 and processed into a form required by the system, and the image data thus processed is stored in the DRAM 9. (SB2)

In this way, when an image of one frame is stored in the DRAM 9, the JPEG compression is not immediately started as in the prior art, but it is checked whether the number of shots already set is reached. It is checked whether the memory space of the DRAM 9 to be stored is secured, and if it is determined that the memory space is secured, the memory space is designated and the next captured image information is stored. The image capture process is repeatedly performed (SB2-SB5).

At this time, the memory allocation amount of the DRAM 9 is changed according to the resolution mode set above, that is, the continuous shooting mode of high resolution or the continuous shooting mode of low resolution. In other words, if the capacity of the DRAM 9 is secured and it is determined that the high-resolution continuous shooting mode can be realized, the storage space for image data is sufficiently allocated and stored in high resolution. Otherwise, the storage space is allocated less. Store at low resolution.

When the number of shots reaches the preset number of shots or the remaining memory space of the DRAM 9 is exhausted as described above, the image data stored in the DRAM 9 is compressed and then flash-processed. 11) to save.

That is, the central processing unit 8 controls the gate array unit 10 to read image data of one frame stored in the DRAM 9, and the internal JPEG compression restorer 8A and SRAM 12 are read. After compression processing, it is stored in the flash memory 11. (SB6, SB7)

Subsequently, the image data of the next frame is read, compressed and stored in the flash memory 11 as described above, and the captured storage information is repeatedly performed as desired, and all captured image information is stored in the flash memory 11. If it is saved, the series of compression storage process is terminated (SB8).

On the other hand, the image data stored in the compressed form in the flash memory 11 is extended by the central processing unit (8) in its original form and stored in the DRAM (9) and then through the digital signal processing unit (4) Since it is output to the monitor 5 side, the user can see the pictures taken continuously.

As described in detail above, in the present invention, the memory is allowed without uniformly processing a series of processes of capturing, compressing, and storing each frame image in compressing and storing image information photographed continuously in a memory. By capturing successively at the resolution required by the user within the range and storing it in the DRAM, and then compressing and storing it in the flash memory, the continuous shooting time interval can be set regardless of the compression processing time, contributing to high speed continuous shooting. It has an effect. In addition, if the memory capacity of the DRAM is secured and it is determined that a high-resolution continuous shooting mode can be implemented, when storing image information on the DRAM, the memory space is allotted enough to be captured at a high resolution. By capturing image information in a mode, the memory utilization can be improved.

Claims (4)

An image information capturing step of sequentially receiving image information of a subject obtained by photographing on a frame-by-frame basis, and storing the image information at different resolutions according to a storage capacity of a temporary memory; And compressing the image information stored in the temporary memory and storing the image information in a flash memory. The method of claim 1, wherein the capturing the image information further comprises storing the image information by dividing the image information into the high resolution mode and the low resolution mode according to the memory capacity of the temporary memory. The method of claim 1, wherein the capturing of the image information comprises storing image information of a predetermined number of continuous shooting frames in a temporary memory. The method of claim 1, wherein the storage capacity of the temporary memory is a remaining capacity of the temporary memory.

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