JPH03267882A - Picture coder - Google Patents

Abstract

PURPOSE:To realize a recorder offering convenient usage by providing a means applying fixed length compression, a variable length compression and a means selecting either of the two means. CONSTITUTION:At application of power, the fixed length mode is set and an operation switch 9 of a display device 8 is used to select the fixed length/ variable length code by the user. In the case of the fixed length mode, an idle capacity of a medium is divided by the code quantity and the result is displayed as a remaining recordable picture number. In the case of the variable length mode, the idle capacity of the medium is divided by a standard code quantity or a maximum code quantity and the remaining recordable picture number is displayed. Thus, the switch 9 by which the user selects either the fixed length length code mode or the variable length code mode is provided thereby selecting which of picture quality or recordable picture number is to be traded off and improving the use of convenience.

Description

[Detailed Description of the Invention] [Industrial Application Field] [Prior Art] Conventionally, image compression technology is used to digitally compress image data, and digital data is stored in a semiconductor memory or magnetic disk.
As a system that aims to record in ta, for example, research is being conducted on an image compression method known as the ADCT method, which uses a fixed length compression code for each screen in order to guarantee the number of recorded images. .

[Problem that the invention is trying to solve]

However, in these methods, for example, 1 bit/pixel
If compressed to el, images with a small amount of information will suffer less deterioration, but the image quality of the compressed images cannot be guaranteed for all images. In order to guarantee image quality and fixed length code, for example, 8 bits/pixel for brightness and color signals, depending on the method.
It can only be compressed to about +.

On the other hand, if the amount of generated code is allowed to vary depending on the image without making the image compression code amount a fixed length, it is possible to perform compression while guaranteeing image quality.

However, in this case, the total number of recordable sheets cannot be guaranteed.

Therefore, a system that guarantees the number of recorded images cannot guarantee image quality, and a system that guarantees image quality cannot guarantee the number of recorded images. Therefore, with either of the conventional systems, it was only possible to configure a system that was inconvenient for users.

The present invention has been made in view of these points, and has the following objects.

[Means to solve the problem]

In order to achieve such an object, the present invention provides a means for performing fixed-length compression in which the amount of generated code that is compressed and encoded is fixed or limited regardless of the image, a means for performing variable-length compression in which the amount of generated code is different depending on the image, and means for selecting the two means.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. Note that other parts of the camera that are not directly related to the present invention, such as an aperture and a shutter, are of course provided. In FIG. 1, the optical image of the subject captured by the lens 1 is captured by an imaging device 2° located at the rear, for example, a Charge-Couble.
The image is converted into a video electrical signal by a predetermined device (CCD). The imaging device 2 responds to a control signal given by the control unit 7 to accumulate charges corresponding to an optical image of a subject and read out a video signal. The read video signal is converted into a digital signal by the A/D converter 3. Note that the imaging device 2 and A/D converter 3
Although not shown, means for adjusting the video signal, such as forming and separating gamma-corrected color signals and performing white balance processing, is provided between the two.

The video signal converted into a digital signal is stored in the image memory 4.

The compression encoding circuit 5 compresses and encodes the image data read from the image memory 4 and outputs it to the recording device 6.

In addition, the control unit 7 uses the recording device 6 to record, for example, an MS-DO5.
It is configured to control recording and playback using commands. As a compression method, for example, a compression method that generates a variable length code or a fixed length code such as DCT transform of an image signal and subsequent entropy encoding as described later is executed.

It also has a function of counting the amount of compressed codes without outputting the compressed codes to the recording device 6. For such a function, the circuit shown in FIG. 1 includes a counting circuit 16 for counting the amount of code before outputting the compression-encoded data to the recording device 6.

The recording device 6 has, for example, a semiconductor memory or a tape-shaped recording medium, and can exchange information with a control section, and can write and read arbitrary digital data to and from an arbitrary physical address on the recording medium.

It also has a function to count the free space on the recording medium.

The control unit 7 integrates the functions of the devices 2 to 6 into M# and integrates the entire functions. In particular, image data files on a recording medium can be managed through the recording device.

That is, the control unit 7 is a DO3 (Disk Operating System) implemented in the computer system.
system), it functions to link file information to a physical address on a recording medium. Therefore, the control unit 7 stores a file (=image compressed data) on the recording medium.
You can manage how the information is recorded, and therefore you can also manage the free space. If it is necessary to divide the compressed code into multiple small recording units and store them, the control unit specifies the physical address and data length on the medium for each recording unit and records the compressed code in the recording device 6. let When one image file is placed at a plurality of positions on the recording medium, the control unit 7 also causes information indicating how the image file is placed to be recorded on the recording medium.

The MMIF (man-machine interface) 8 includes an operating member 9 for operating the release (SWI, 5W2) and other switches described below, a display in the Finder, and an external L.
It includes a display device 10 such as a CD display and a buzzer.

The number of shots that can be taken during actual shooting is displayed in the following steps.

This procedure will be explained using the flowchart shown in FIG.

■ First, at the beginning of the flowchart, the control unit 7 outputs commands DIR, CHK, and DSK to the recording device 6 to cause the recording device to output the free space (
SL). SW to press the shutter button halfway to take a picture
When the state is turned on (ON), the control unit drives the lens l to focus, operates the aperture, shutter, etc., exposes the imaging device (S5), and captures the image information into memory (S7) and compresses and encodes it. The operations up to (S9) are performed. Then, the compression code counting circuit 16 counts the code amount of the image data. On the other hand, the free space is counted by the recording device, and from both values, the number of images that can be taken from now on is calculated (Sll). For example, the number of images that can be taken is calculated by dividing the free space by the code amount of image data. The value obtained by the calculation is displayed on a display device 1 installed in the viewfinder.
0 to notify the user (S13).

This display continues while SWl is turned on (S15
゜517) Of course, the image actually taken and recorded will change from S17 to S when you press the shutter button even deeper.
19. S21. The flow branches to S23, and the above-mentioned 5
5°S7. A step similar to S9 is executed and the data is imported again.

■ If the continuous shooting mode is not selected, the flow branches from S25 to S3; if the continuous shooting mode is selected, the free space on the recording medium decreases as continuous shooting progresses, and the amount of code for one screen of image data also changes. Therefore, after recording the first frame of continuous shooting, each time recording of one screen is completed, the free space and the amount of image code to be recorded next are counted (S23), and the amount of free space is counted (S23). The number of sheets is continuously displayed in the finder (S29).

That is, in this embodiment, when SW2 is kept pressed and the continuous recording mode is selected, images are exposed one after another, taken into memory, encoded, and recorded. At that time, the remaining recordable number is calculated from the code amount of the image recorded immediately before and the free space of the recording medium at that time, and the reduced remaining recordable number is continuously displayed in the finder.

Next, S21 in FIG. A detailed flowchart of step S23 will be explained using FIG. 4.

FIG. 4 shows S23 in FIG. That is, it shows the operation performed after image data is stored in the memory 4.

In FIG. 4, first, the image signal written in the memory 4 is read out and compression-encoded by the encoding circuit 5, and the compression-encoded data is counted by the counting circuit 16 (S41). and the free space of the recording medium in the recording device 6 (S43), and if there is enough free space, the image signal is read out from the memory 4 again, compressed and encoded, and the data is output to the recording device 6. The gate 18 is controlled to perform recording.

In this case, the control unit 7 reads out image data from the image memory 4, outputs a compression code to the compression encoding circuit 5,
The recording device 6 is instructed to record the compressed code, and the gate 18 is instructed to open the gate. The recording device 6 is configured to record a compression code by specifying a physical address on the medium and a data length for each recording unit. Since the recording device 6 does not request the compression encoding circuit 5 to output data unless there is a recording instruction from the control section 7, the operations of the compression encoding circuit 5 and the image memory 4 are interrupted. Therefore, the control unit 7 specifies the physical address and data length on the medium for each recording unit according to the file format, and instructs the recording device to perform a recording operation.
Recording can be performed while controlling the operation of the image memory 4.

The recording operation is completed when all compressed codes are recorded.

Incidentally, FIG. 2 is a diagram showing a communication procedure between the control section 7 and the recording device 6 described above.

In FIG. 2, D-Req is the control unit 7 from the recording device 6.
D-Ack is a signal indicating that the data being output from the compression encoding circuit 5 to the recording device 6 is valid; There is. DataD(, ~D7 is 8-bit parallel data output from the compression encoding circuit 5 to the recording device 6.

In FIG. 2, the control unit 7 and the recording device 6 are
This shows a state in which data is output byte by byte while exchanging Req and D-Ack.

In FIG. 2, the side that receives and receives data, that is, the recording device 6 (hereinafter referred to as Receiver), outputs data to the side that outputs data, that is, the encoding circuit 5 (hereinafter referred to as Transmitter), by changing the signal D-Req from High to Low. request that Transmitter is D
When it detects that -Req goes low, it outputs data onto the data bus (Do"D7), and when the value is determined, it changes D-Ack from high to low.

The Receiver takes over the signal on the data bus when D-Ack goes low, and sets D-Req to H4gh.
Return to. Transmitter D-Req is H
When it becomes high, the output to the data bus is stopped and D-Ack is returned to high.

By the above Req-Ack handshake, Tra
Data transfer is performed according to the convenience of both the nsmitter and the receiver. Therefore, the compression encoding circuit 5 does not need to generate compression codes at a fixed transfer rate, and the fact that the code length changes depending on the content of the image does not cause any problems.

Further, when the flow branches to S47 in S43, the control unit notifies the finder display warning device 10 of the man-machine interface 8 that recording is not possible due to insufficient free space on the recording medium. The user is prompted to select one of the following three processes.

That is, (1) stop the recording operation, (2) replace the recording medium, and (3) erase one of the image files on the currently installed recording medium.

For this reason, the control unit 7 performs S49. S51. Execute step S53.

If (1) is selected by the user, all operations are stopped from S49.

If (2) is selected by the user, that is, if the recording device 6 detects the replacement of the medium and reports it to the control unit 7, the process returns to S43.

When (3) is selected by the user, the control unit 7 displays how many images are present on the display device 10 555
) Prompt the user to enter which image to delete. When the user inputs the number of the image to be deleted using the operation switch (S57), the control unit 7 deletes the image file (559), and returns to S43.

In order to detect that the medium has been replaced, a method may be used in which the recording section mechanically detects whether or not the medium has been replaced, as disclosed in Japanese Patent Application Laid-Open No. 182669/1983. The control unit 7 can access information on the presence/absence of such information via the recording device 6.

According to the control shown in the flowchart of FIG. 4 explained above, even if a compression method that generates variable length codes is used, image recording is guaranteed for the user in some way, so a system that is easy to use and can guarantee image quality is created. Can be provided.

Next, using FIG. 5, a method of displaying the number of shots that can be taken, which is executed in Sll and S13 in FIG. 3, will be explained.

For example, the control unit 7 outputs the above-mentioned command for detecting free space, causes the recording device 6 to count the free space of the recording medium (S61), and calculates the compression ratio of the variable length encoding method stored in advance. Calculate how many more images can be recorded on the recording medium from the representative value and free space (363
).

For example, the encoding method is
680 encoding method, the code length is on average 2 bits/pixel, at worst about 4.5 bits/pixel, so in S65 the average code length is 2 bits/pixel.
The number of shots that can be taken calculated in pixels is the standard number of remaining shots,
Both of them are displayed on the display device (8) with the number of images that can be taken calculated at 4.5 bits/pixel as the minimum guaranteed number of images. Of course, only one of these displays may be performed.

The display device 8 is, for example, Liquid Crystal D.
isplay (LCD) and Light-Emitti
ng Diocle (LED), etc., and can be displayed on the top of the camera, in the viewfinder, or both.

The present embodiment described above has means for counting the free space of the recording medium, and by storing the representative value of the compressed code amount in variable length encoding, the counted free space and the representative value of the code amount can be calculated from the counted free space and the representative value of the code amount. By having a function that can calculate the number of shots that can be taken by a recording medium, and by having a means to display information on the number of shots that can be taken by the calculation, it is possible to determine whether the number of shots that can be taken by a recording medium is the standard value or the minimum guaranteed value. A variable length encoded digital image recording device is shown that can display either or both.

Furthermore, according to the present embodiment described above, after detecting the free space of the recording medium at step S1 in FIG. 3, the free space of the recording medium is detected again at step S13, details of which are shown in FIG. This allows you to check the free space on the recording medium not only when the SWI is turned on, but also during continuous recording.

Furthermore, according to this embodiment, even if variable length encoding compression is used, it is possible to guarantee and inform the user of the amount of images to be recorded, that is, the number of remaining images that can be taken on the recording medium, making it easy to use and improving image quality. can be guaranteed.

In this embodiment, an example of a compression method that can generate both a variable length code and a fixed length code is "ISO/JTCI
DC listed in /SC2/WG8 N800″
An adaptive compression method using T (discrete cosine transform) (
(hereinafter referred to as ADCT method). In such an ADCT method, the compression rate can be controlled by the encoding parameter F. The relationship between F and compression rate is as shown in FIG. 7, where the compression bit rate is a monotonically decreasing function of F. In FIG. 7, (a) and (b) show the relationship between F and bit rate for different images, respectively. Figure 7(a),(b)
), the relationship between F and bit rate depends on the content of the image, but always decreases monotonically. Therefore, it is possible to match the desired bit rate by several trials and errors while adjusting F.

In this embodiment, the compression encoding circuit 5 shown in FIG.
It is a method described in "ISO..." that allows you to select between a variable length compression method and a fixed length compression method.

Further, the control unit 7 can know about such selection via the man-machine interface 9.

When the control unit learns that the user has selected the recording number priority mode and pressed the release button in the man-machine interface, the control unit 7 controls the photographing device 2, AD converter 3, and image memory 4 to store images. The image of the subject is stored as digital data in the image memory.

The control section passes the parameter F to the compression encoding circuit 5 to cause the compression encoding circuit 5 to compress the image data stored in the image memory and count the compression codes. At this time, the encoding device does not write the compression code to the recording device, but only calculates the amount of code for one screen. Then, trial and error is repeated several times while changing F until the desired code amount is achieved.

When F that generates the desired amount of code is determined, the control unit 7
gives this F to the compression encoding circuit 8 and instructs the recording device 6 to output a compressed code, thereby restarting the compression operation. Then, the control unit 7 instructs the recording device 6 to record the compressed code. Through the above processing, the compressed code that has been made into a fixed length for each screen is recorded on the recording device.

Next, when priority is given to image quality, the control section makes the parameter F passed to the compression encoding circuit 8 sufficiently small to prevent image quality deterioration. That is, the value of F is fixed at a certain value, and the work of determining the first F when the number of recording sheets is prioritized is not performed. Then, the image data on the image memory is compressed for compression encoding and outputted to the recording device 6, and the recording device 6 is caused to record one compression code.

In this embodiment, when the compression mode is switched between fixed length/variable length mode, the number of remaining sheets, the settable continuous recording speed, etc. are also changed. In other words, in the case of a fixed length, the amount of code is fixed, so the number of recordable sheets can be calculated accurately by dividing the free capacity of the medium by the amount of code. On the other hand, in variable length mode, it is impossible to accurately calculate the possible number of sheets. Further, in the fixed length mode, since a plurality of repetition processes are required, the time required for recording is longer than in the variable length mode. Therefore, the settable continuous recording speed decreases. These things affect the camera's display content and continuous recording speed settings.

In response to the above two problems, the control unit 7 of this embodiment calculates and displays the number of recordable sheets by dividing the recordable capacity by the standard code amount or the maximum value in the variable length mode. In the fixed length mode, processing such as reducing the upper limit of the continuous recording speed that can be set is required.

The above processing can be expressed as a flowchart as shown in FIG. First, when the power is turned on (SL), the set value of defect is set to, for example, fixed length mode. Also, the continuous speed is set to the lowest value (S3).

Normally, the user changes the fixed length/variable length mode using terminal S. Alternatively, it waits to see if the continuous speed should be changed, and processes are performed depending on each case.

If there is a change in fixed length/variable length mode, proceed to step 5. In fixed length mode, the free capacity of the medium is divided by the code amount and displayed as the number of remaining recordable sheets. The current possible continuous speed is then set as the upper limit of the continuous speed in the fixed length mode (S7). On the other hand, in the variable length mode, the free capacity of the medium is divided by the standard code amount or the maximum value in S9, and the result is displayed as the number of remaining recordable sheets. Then, the current continuous recording speed is set as the upper limit value of the continuous recording speed in the variable length mode (Sll).

In step 520, if the current continuous recording speed setting value exceeds the range of possible continuous recording speeds, the continuous recording speed setting value is set as the upper limit speed of the range (S22).

Then, display the continuous speed (524) and return to terminal S.

Further, if there is an instruction to change the continuous recording speed in S2, and more specifically from S30, if the user presses the continuous recording speed change button and instructs to increase the continuous recording speed by one unit, the process in S33 is performed. Go to , and increase the current continuous recording speed setting by one unit. Then, it is compared with the current continuous recordable speed (S35), and if it exceeds, the continuous speed is reset to the lowest value (S37). Then, the continuous speed setting value is displayed and the process returns to terminal S (S39).

According to the embodiment described above, by providing a means for the user to select between the fixed length compression mode and the variable length compression mode, the user can select whether to give priority to image quality or the number of recording sheets, thereby improving usability. It can be improved.

Furthermore, in the fixed length compression mode of this embodiment, a predetermined time is required until the compression operation is completed, so the continuous speed can be set high.

Furthermore, since the upper limit of the continuous recording speed is automatically corrected depending on whether the compression mode is fixed length or variable length, reliable compression operation can be performed.

Furthermore, various other methods may be used as the variable length encoding method of the compression encoding method in this embodiment. For example, DC
Entropy encoding may be performed on T-encoded data, and it is sufficient to switch between fixed-length compression and variable-length compression. Therefore, both methods do not have to be the same method.

Further, in this embodiment, the recording device 6 is MS-DO5.
Although the data storage device is driven by an OS system, the present invention is not limited to this, and other types of media may be used, such as semiconductor memory or tape-shaped media.

When considering a floppy disk as a recording medium, it is quite possible to realize a capacity of 5M Eyes with a 2-inch floppy disk if a perpendicular magnetization recording method is used. In this case, the present embodiment can guarantee a standard 55 to at least 22 TV field images to the floppy disk.

Further, in this embodiment, commands such as DIR and CHKDSK are sent from the control unit 7 to the recording device 6 as a means for generating information regarding the storage capacity of the storage means, but the commands are not limited to this, and the unrecorded portion of the storage means, i.e. When a tape is used as the medium, the control section 7 may actually detect the main recording area on the tape.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to select between variable length encoding and fixed length encoding, thereby providing a recording device that is easy to use.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a device according to an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the device shown in FIG. 1, and FIG. 3 is a block diagram showing the operation of the device shown in FIG. 1. Flowcharts, FIGS. 4 and 5 are flowcharts showing some details of the flowchart in FIG. 3, FIG. 6 is a flowchart of another embodiment of the present invention, and FIG. 7 is a flowchart showing the embodiment of FIG. 6. FIG. 1: Lens 2: C0D 3: A/D converter 4: Image memory: Compression encoding circuit; Recording device 2 control unit, display device: Operation switch Fig. 2 &: f; ratt (brt F!l-Pizel
)O 0 昂D (a-) (b)

Claims (1)

[Claims] (1) The amount of code generated by compression encoding is fixed regardless of the image.
An image encoding device comprising means for performing fixed-length compression, or means for performing variable-length compression in which the amount of generated code varies depending on the image, and means for selecting one of the two means.