JP3263674B2 - Digital camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera, and more particularly, to a digital camera for individually compressing and recording a captured image, for example.

[0002]

2. Description of the Related Art In a conventional digital camera of this type,
When a plurality of still images forming a moving image are compressed by so-called motion JPEG, the compression ratio is always constant.

[0003]

In this prior art, if the compression ratio is lowered to obtain a high-quality still image, the file size becomes large, and the data amount becomes large when recorded for a long time. On the other hand, when the compression ratio is increased, the file size is reduced, but the image quality of each still image is deteriorated, and there is a problem that deterioration is particularly noticeable during still reproduction.

[0004] Therefore, a main object of the present invention is to provide a digital camera capable of suppressing the amount of data and improving the image quality during still reproduction.

[0005]

According to a first aspect of the present invention, a moving image is generated .
Capturer for capturing still image signals of multiple screens to be formed
Column, each of multiple different size values is enabled for each screen
Activating means, and a multiple-screen still image signal.
Target the size value activated by the activation
This is a digital camera provided with compression means for separately performing compression . A second invention is a multi-screen still image forming a moving image.
Capturing means for capturing an image signal;
Enabling means for enabling each of the size values for each screen, and
The still image signal of multiple screens is activated by the activation means.
Compression means for individually compressing the target size value.
This is an image compression device. The third invention provides a shooting instruction
Still image mode for taking a picture of one screen in response
Continuously capture images for multiple screens in response to a shadow instruction
In the digital camera having a moving image mode, the first enabling means for enabling the first compression rate when the still image mode is set, than the first compression rate and the first compression ratio when the video image mode is set High second compression ratio on the screen
Therefore, the second enabling means for selectively enabling and the first enabling means
Activated by the activating means or the second activating means
The captured image signal of each screen is individually compressed based on the compression ratio.
A digital camera characterized by comprising compression means . According to a fourth aspect of the present invention, one image is
In still image mode to capture images of planes and instruction to capture
Responds to a moving image mode that continuously captures images for multiple screens in response.
In the image compression apparatus having the
First activation method that activates the first compression ratio when is set
When the moving image mode is set, the first compression ratio and
Select a second compression ratio higher than the first compression ratio depending on the screen
To the second activation means and to the first activation means.
Or based on the compression ratio activated by the second activation means.
And compression means for individually compressing the image signal of each screen.
An image compression apparatus characterized in that:

[0006]

The first setting means sets a still image mode for photographing an image for one screen. In the still image mode, the first activating means activates the first compression ratio. Further, the second setting means sets a moving image mode in which images for a plurality of continuous screens are captured. In the moving image mode, the second activating means selectively activates the first compression ratio and the second compression ratio higher than the first compression ratio.

In one aspect of the present invention, in the moving image mode, the second activating means activates the first compression ratio every predetermined number of screens. In one embodiment of the present invention, the second validating means validates the first compression ratio when compressing the first image and the last image. According to another embodiment of the present invention, in the moving image mode, the correction unit corrects the second compression ratio based on the previous second compression ratio, the target compressed data size, and the current compressed data size.

In another aspect of the present invention, the third setting means sets a frame-by-frame playback mode for frame-by-frame playback of a moving image. In the frame-by-frame playback mode, an image compressed at the first compression rate is played back, and the output means outputs information on the first compression rate.

[0009]

According to the present invention, since the data is selectively compressed at the first compression ratio, the entire data size does not become too large. Therefore, the data amount does not increase. Also,
If a still image compressed at the first compression ratio is extracted, the image quality during still reproduction can be improved.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a digital camera 10 of this embodiment includes a CCD imager 12. A color filter (not shown) is mounted on a front surface of the CCD imager 12, and a light image of a subject is irradiated on the CCD imager 12 through the color filter. When the mode setting switch 50 is switched to "camera", the system controller 42 sets the camera mode. The timing generator (TG) 14 includes a signal generator (SG) 16
A timing signal is generated based on a vertical synchronizing signal and a horizontal synchronizing signal output from the CPU, and the CCD imager 12 is driven by a progressive scan method. As a result, a camera signal of the subject is output from the CCD imager 12. The output camera signal is supplied to a CDS / AGC circuit 18.
Then, the noise is removed and the level is adjusted in a known manner. The signal processing circuit 22 has an A / D
The YUV conversion is performed on the camera data output from the converter 16 to generate YUV data.

The generated YUV data is supplied to a memory control circuit 26 via a bus 24, and the memory control circuit 26
Is written to the SDRAM 28. That is, CC
Since the D imager 12 employs the progressive scan system, while the monitor 40 employs the interlace scan system, the YUV data is temporarily stored in the SDRAM 28 for conversion of the scan system. YUV stored
The data is then read by the same memory control circuit 26 in an interlaced scan manner and applied to the video encoder 38 via the bus 24. The video encoder 38 generates a composite video signal in accordance with the NTSC format from the input YUV data, and inputs the generated composite video signal to the monitor 40. As a result, a moving image of the subject image is displayed on the monitor 40 in real time.

When the mode setting switch 50 is switched to the reproduction side and the still image mode is selected by the photographing mode selection button 54, photographing is performed only once each time the shutter button 48 is pressed once. In this still image mode, if the operator operates the shutter button 48, the YUV data (still image data) at the time of the operation is transferred to the SDRAM 2.
8, the CCD imager 12 is disabled. That is, the predetermined still image data is stored in the SDRAM 28
Is secured. The still image data is thereafter read by the memory control circuit 26 and input to the JPEG codec 30. The JPEG codec 30 also includes a CPU 32
, And compresses still image data according to the compression ratio data.

In the still image mode, still image data is compressed at a first compression ratio. That is, the still image data is compressed to a size of about 20% of the original data size. The compressed still image data (compressed image data)
According to the instruction of the memory control circuit 26, once the SDRAM 28
Is stored in At the time of compression, the CPU 28 calculates the data size (compressed data size) of the compressed image data and compares it with the target compressed data size (target size) L. That is,
The target size L set to 20 ± 3% is stored in the memory 32b, and the calculated data size is compared with such a target size L. The CPU 32 instructs the JPEG codec 30 to change the compression ratio based on the comparison result. Still image data is recompressed at the changed compression ratio. The compressed image data obtained by this is SDRAM
28, and then stored in the memory card 36 via the I / F circuit 34.

The CPU 32 processes such an operation according to a flowchart shown in FIG. When the still image mode is selected and the shutter button 48 is pressed, the CPU 32 starts processing, and sets the first compression ratio to the JPEG codec 30 in step S1. The still image data is JPEG-compressed at the first compression ratio, and the compressed image data is
Is stored once. In the following step S3, the compressed data size is calculated, and in step S5, the first compression ratio is changed by comparing with the target size L. That is, steps S1 to S5
Activates the first compression ratio. In step S7, the changed first compression ratio data is
Set to 0 again. The JPEG codec 30 uses SDR
The still image data before compression stored in the AM 28 is JPEG-compressed again at the updated first compression ratio. The compressed image data obtained in this way is supplied to the SDRAM 28 and overwritten on the compressed image data obtained in the first JPEG compression. In a succeeding step S9, the compressed still image data is stored in the memory card 36, and the process returns.

When the moving image mode is selected by the photographing mode selection button 54 and the operator operates the shutter button 48, the moving image of the subject is recorded on the memory card 36. Specifically, the operator presses the shutter button 48
Is pressed once, the CPU 32 sets the compression rate in the JPEG codec 30. On the other hand, the memory control circuit 26
The YUV data for one frame, that is, the still image data for one screen, is read from the RAM 28 and supplied to the JPEG codec 30. Therefore, in the JPEG codec 30, compressed image data for one screen is generated by one compression process, and the generated compressed image data is stored in the SDRAM2.
8 is temporarily stored.

Unless the shutter button 48 is pressed again by the operator, the CPU 32 repeatedly sets the compression rate in the JPEG codec 30. As a result, a plurality of compressed image data are generated and accumulated in the SDRAM 28. When the shutter button 48 is pressed, the CPU 3
2 disables the CCD imager 12 and stops the photographing operation. The memory control circuit 26 collectively reads still image data for a plurality of screens stored in the SDRAM 28.
The read still image data for a plurality of screens, that is, moving image data, is recorded on the memory card 36 via the I / F circuit 34. A method of sequentially performing JPEG compression on still image data for a plurality of screens to create moving image data is as follows.
This is a well-known technique called motion JPEG.

More specifically, the CPU 32 is provided with a counter 32a, and the counter 32a counts still image data for a plurality of screens. When the moving image mode is selected and the shutter button 48 is pressed, the counter 32a
Is reset, and the JPEG codec 30 is set to the second compression ratio according to the instruction of the CPU 32. In this embodiment, the still image data is compressed at the second compression ratio, and is reduced to about 10% of the original data size. In the moving image mode, the target size S is 10 ± 3%.
And stored in the memory 32b. The compressed image data is stored in the SDRAM 2 in accordance with an instruction from the memory control circuit 26.
8 is stored once. Here, the CPU 32 is an SDRAM
The size of the compressed data stored in 28 is calculated and compared with the target size S. The CPU 32 corrects the second compression ratio based on the comparison result, and sets the corrected second compression ratio in the JPEG codec 30. Assuming that the target size S is Z and the data size of the still image data compressed at the second compression ratio is Y, the next (or previous) compression ratio Xa is the next compression ratio Xa.
b is obtained by Equation 1.

[0019]

Xb = (Y / Z) × Xa In this embodiment, as shown in FIG. 3, the first frame, the last frame, and a multiple of four (4 × i-th; i is a natural number). The still image data of the frame is compressed at a first compression ratio smaller than the second compression ratio. The data size after compression is about 20% of the original data size. Still image data of the first frame, the last frame, and the frame of a multiple of 4 is detected by the CPU 32 based on the count value of the counter 32a, and the CPU 32 changes the second compression ratio to the first compression ratio according to the count value.
That is, the first compression ratio is set in the JPEG codec 30. The first frame, the last frame, and frames that are multiples of 4 are compressed at the first compression ratio. At this time, the still image data compressed at the first compression ratio is directly used as the SDRAM 28.
Is stored in The second compression ratio is corrected by the above equation 1, but the first compression ratio is fixed. Therefore, when the first compression ratio is used for the compression processing of the current frame, the second compression ratio of the previous frame is set to the compression ratio Xa of Expression 1, and the second compression ratio of the next frame is set to the compression ratio Xb of Expression 1. It is said.

The CPU 32 processes such an operation according to a flowchart shown in FIG. When the moving image mode is selected and the shutter button 48 is pressed, the CPU 32
Starts the process, and resets the counter 32a (i = 0) in step S11. In the following step S13, the second
The compression ratio is determined, and in step S15, it is determined whether the current frame is the first frame, the last frame, or the 4 × i-th frame. If “YES” in the step S15, the first compression ratio is determined in a step S17, and the first compression ratio is set in the JPEG codec 30 in a step S19. Therefore, the still image data is compressed at the first compression ratio, the compressed image data is temporarily stored in the SDRAM 28, and the process proceeds to step S27.

On the other hand, if "NO" in the step S15, in a step S21, the second signal determined in the step S13 is determined.
The compression ratio is set in the JPEG codec 30. Therefore, the still image data is compressed at the second compression ratio, and the compressed image data is temporarily stored in the SDRAM 28, and is stored in step S2.
Proceed to 3. In step S23, the size of the compressed data once stored in the SDRAM 28 is calculated. In the following step S25, the next compression ratio Xb is calculated according to Equation 1 based on the target size S stored in the memory 32b and the calculated data size. The changed compression ratio is only the second compression. Thus, steps S17 and S1
3. In S21 to S25, the first compression ratio and the second compression ratio are selectively enabled.

In step S27, the counter 32a is incremented, and it is determined in step S29 whether or not photographing has been completed. If "NO" here, the process returns to the step S15, but if "YES", the process returns.
When the mode setting switch 50 is switched to “video playback”, the video playback mode is set by the system controller 42. The CPU 32 includes a memory card 36
And reads the desired moving image data from
It is stored in the DRAM 28. The CPU 32 further executes JP
It instructs the EG codec 30 to decompress the head still image data. The JPEG codec 30 gives a request to read out desired still image data to the memory control circuit 26 every time the decompression command is given once, and performs JPEG decompression on the read still image data. As a result, immediately after the moving image reproduction mode is set, the still image data stored at the head of the moving image data is expanded.

The expanded still image data is written into the SDRAM 28 again by the memory control circuit 26 and thereafter read out by the same memory control circuit 26 in an interlaced scan system. The video encoder 38 converts the read still image data into a composite video signal according to the NTSC format. As a result, the first still image is displayed on the monitor 40.

When the frame advance button 52 is pressed in this state, a frame advance reproduction mode is set. In the frame-by-frame playback mode, each time the start button 56 is pressed, still image data corresponding to a plurality of screens shot in the moving image shooting mode is played one frame (one frame) at a time. The still image data to be reproduced is counted by the counter 32a. When still image data compressed at a compression rate lower than the first compression rate (second compression rate) during shooting is displayed, as shown in FIG. 5, "H" indicating high quality is displayed at the upper right of the screen.
Q "is superimposed on the still image and displayed.
The still image data compressed at the second compression ratio is
In the case of reading from the switch 8, the switch SW1 is switched according to the instruction of the CPU 32, and the output signal of the video encoder 38 or the output signal of the character generator 58 is output to the monitor 40. Therefore, “HQ” is overwritten on the still image data. For example, when editing with a computer, high-quality still image data can be used by extracting a still image overwritten with “HQ”.

The CPU 32 processes such an operation according to the flowchart shown in FIG. When the frame-by-frame playback mode is selected, the CPU 32 starts processing, and proceeds to step S31.
To load the moving image data on the SDRAM 28. In the following step S33, the counter 32a is reset (i =
0), and in a step S35, it is determined whether or not the start button 56 is pressed. If "NO" here, the process returns to the step S35, but if "YES", one frame (one frame) of still image data is reproduced in a step S37. In a succeeding step S39, it is determined whether or not the frame is the first frame, the last frame, or the 4 × i-th frame. If “NO”, the process proceeds to a step S43.
If "ES", the switch SW1 is switched in step S41 to display "HQ" over the still image data.
As described above, information (“HQ”) regarding the first compression ratio is output in steps S39 and S41. In a succeeding step S43, the counter 32a is incremented. In a step S45, it is determined whether or not the frame-by-frame playback is completed, that is, whether or not the last screen is displayed. here,
If “NO”, the process returns to the step S35, but the “YE
If S ", return.

According to this embodiment, the first frame, the last frame of the moving image data, and the still image data of a multiple of 4 frames are compressed at a low compression ratio (first compression ratio). Can be improved. In addition, since the still image data of some frames is compressed at a low compression rate as described above, the data size of the moving image data does not become too large. Therefore, it is possible to prevent an increase in the data amount.

In this embodiment, the still image data is compressed at a low compression ratio for each frame of a multiple of 4, but the multiple may be an arbitrary multiple N and may be set by the operator. .

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2 is a flowchart showing a part of the processing of the CPU shown in FIG. 1 embodiment;

FIG. 3 is an illustrative view showing a compression ratio of still image data corresponding to a plurality of screens when shooting in a moving image mode;

FIG. 4 is a flowchart showing a part of the processing of the CPU shown in the embodiment in FIG. 1;

FIG. 5 is an illustrative view showing a case where still image data compressed at a low compression ratio is reproduced;

FIG. 6 is a flowchart showing a part of the processing of the CPU shown in the embodiment in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Digital camera 22 ... Signal processing circuit 26 ... Memory control circuit 28 ... SDRAM 30 ... JPEG codec 32 ... CPU 42 ... System controller 58 ... Character generator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI // H04N 101: 00

Claims (8)

(57) [Claims] A still image signal for a plurality of screens forming a moving image
Capture means for enabling each of a plurality of different size values for each screen
Activating means, and the multi-screen still image signal
Target the size value activated by the activation means
A digital camera comprising compression means for individually compressing data . 2. A pre Kieu Enabling means the plurality of size values
2. The method according to claim 1, wherein the specific size value is enabled for each predetermined number of screens.
Digital camera as described. 3. A method according to claim 2, wherein said plurality of compression means are compressed by said compression means.
Playback means for individually playing back still image signals on the screen, and
The pressure is targeted at a specific size value among the plurality of size values.
A message associated with the playback of the compressed compressed still image signal
Further comprising output means for outputting a di-, claim 1 or 2 digital camera according. 4. The compression means performs compression by the JPEG method.
Cormorants, digital camera according to any one of claims 1 to 3. 5. A still image signal for a plurality of screens forming a moving image.
Capture means for enabling each of a plurality of different size values for each screen
Activating means, and the multi-screen still image signal
Target the size value activated by the activation means
An image compression device comprising compression means for individually compressing the image data. 6. An image for one screen is taken in response to a photographing instruction.
Still image mode and multiple screens in response to the shooting instruction
A digital camera having a moving image mode for continuously capturing images of a minute , wherein the first enabling means for enabling a first compression ratio when the still image mode is set ; and wherein the moving image mode is set. When the first compression ratio and the second compression ratio higher than the first compression ratio are displayed on the screen,
Second enabling means for selectively enabling Te, and the first
Activated by the activating means or the second activating means
The image signal of each screen is individually compressed based on the
A digital camera comprising compression means for compressing . Wherein said second enabling means for selecting said first compression ratio every predetermined number of screens, a digital camera according to claim 6, wherein. Claim 8. One screen image in response to the capture instruction
Still image mode to capture and in response to the capture instruction
A moving image mode for continuously capturing images for multiple screens
An image compression apparatus having The first compression ratio is enabled when the still image mode is set
First enabling means to be When the first compression ratio is set when the moving image mode is set
And a second compression ratio higher than the first compression ratio is displayed on the screen.
Second activating means for selectively activating and The first
Activated by the activating means or the second activating means
Image signal of each screen is individually compressed based on the
An image compression device, comprising: a compression unit.