JPH04114564A - Picture signal recording device - Google Patents

Abstract

PURPOSE:To suppress the deterioration of a picture and to efficiently compress the picture by once recording plural pictures on a recording medium and permitting an expanding means to decode a recorded picture signal so as to compress by a fixed length again. CONSTITUTION:An A/D converer 3 converts an image pickup signal which an image pickup device 2 reads into a digital signal and the video signal is accumulated in a picture memory 4. A compression encoding/ decoding device 5 encodes picture data which is read from the picture memory 4 and outputs it to a recording device 6 or decodes a code which is read from the recording medium by the recording device and accumulates it in the picture memory 4. A control part 7 transfers a parameter F to the compression encoding/ decoding device 5, compresses picture data in the picture memory 4 and counts a code quantity. When the desired code quantity is generated, the control part gives the parameter Fa to the compression encoding/decoding device 5 again and instructs the recording device 6 to output a compression code. Thus, the deterioration of the picture is suppressed and the picture can efficiently be compressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image signal recording device that compresses and encodes an image signal and records it.

[Prior art] Examples of conventional image compression technologies include ISO, /JTCI, and S
C2,/WG8 N800 (hereinafter referred to as 'Reference 1')
DiscreteCosineTransfo
rm/hereinafter referred to as "17A D CT method"). This method has the function of compressing an image to a constant code amount regardless of the image by repeating the process of trial and error several times. This adjustment function will be briefly explained below.

In the ADCT method, the compression rate (that is, the amount of code) can be controlled by a certain encoding parameter F. As shown in FIG. 3, the compression ratio is a monotonically decreasing function of F. In Figure 3 (
Figures a) and (b) show the relationship between F and compression rate for different images. As can be seen from Figure 3 (a) and (b), F
The relationship between F and compression rate depends on the content of the image, but is always a monotonically decreasing function of F. Therefore, it is possible to converge to a desired compression ratio (code amount) by trial and error several times while adjusting F.

However, the value of F is proportional to the quantization size of the DCT coefficient, and if it is increased, the quantization will be made more coarsely, which will deteriorate the image quality.

In the ADCT method, if it is acceptable for the code amount to vary depending on the image, it is also possible to fix F and compress without performing repetitive processing. Therefore, if compression is performed while fixing the value of F to a sufficiently small value, the amount of code will be large and will vary depending on the image, but any image will suffer less deterioration due to compression.

Here, fixed length compression (FLC: Fixed Length Compression) is a compression method that involves repeated processing and control of code amount.
hCoding), variable length compression (hereinafter referred to as VLC) is a compression method that does not involve repetitive processing and control of the amount of code.
availableLengthCoding).

[Problem to be solved by the invention I In VLC, the code amount is variable length depending on the image, that is, the code amount is an amount that reflects the content of the image, so the value of the parameter F is sufficiently small to reduce the code amount. By doing so, it is possible to minimize the deterioration caused by compression.

Since the length of one side is variable, there is a drawback that the number of sheets that can be recorded per recording medium is unstable.

On the other hand, since FLC has a fixed variable length, it is possible to guarantee the number of recordable sheets per recording medium. Since the half-image is compressed to a fixed amount of code regardless of its content, it has the disadvantage that some images may be significantly degraded.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image signal recording device that can efficiently compress images while suppressing image deterioration.

[Means and operations for solving the problems] In order to solve the above problems, the image signal recording device of the present invention includes a first compression means that performs variable length compression, and a second compression means that performs fixed length compression. , a decompressing means for decompressing the image signal compressed by the first or second compressing means is used, a plurality of images are once recorded on the recording medium by the first compressing means, and then the images are unrecorded. [Embodiment] The present invention takes advantage of the two advantages of the above-mentioned VLC and FLC compression. This paper proposes a recording method that takes full advantage of this technology, reduces image quality deterioration, and guarantees the number of sheets per recording medium.

In the present invention, basically, an image is first recorded by VLC. At this time, the value of F is selected to be sufficiently small so that there is little deterioration in image quality. When the total code amount of multiple images recorded by VLC reaches a certain level, if the total code amount does not reach the number that should be guaranteed, then those images are decoded and The FLC is used to re-encode the images so that the total amount of code falls within the amount of code allocated to that number of images.

At this time, instead of allocating the amount of code equally to all images, the amount of code to be allocated is determined according to the amount of code when first encoded by VLC. For example, an image with a large amount of code by VLC is considered to have more image information, so it is re-encoded with a relatively large amount of code.

With this recording method, it is possible to allocate the code amount in a well-balanced manner while taking into consideration the content of the image, and it is possible to guarantee the number of recordable sheets on the recording medium.

The above explanation will be explained in more detail.

For example, assume a digital still camera whose recording medium is a magnetic disk with a total recordable capacity of 2 Mbytes. Assume that it is guaranteed that 20 images can be recorded on one magnetic disk. In that case, the average allocated code amount per image is 100 bytes.

For example, when multiple images are recorded using LC and the total recording capacity exceeds 1900 bytes, 2
If zero or more images were recorded, there is no problem because the guaranteed number of images could be recorded while maintaining the image quality. Therefore, assume that the number of sheets is 19 or less.

For example, suppose that only 10 images have been recorded. The total code amount of these 10 images is lO*1oOK bytes (=
IM byte) is re-encoded using FLC.

Let the code amount of each image when encoded by VLC be VLCvolume(i). Here l represents the number of the recorded image.

Total code amount of images encoded by VLC VLCsu
m is expressed by formula (1).

The code amount for re-encoding for image 1 is FLCvol
Let it be ume(i). FLCvolume (i) is given by distributing, for example, VLCsum at the ratio of VLCvolume (i). At this time, FLCvolume (i)
is given by equation (2).

Since it is always larger than VLCsumlOOKbytesXlo, from formula (2), F L Cv o I u m e
(i) is always smaller than V L Cv o I u m e (i). Therefore, once the VLC code is decoded and the data on the recording medium is erased, the re-encoded code can always be recorded on the recording medium.

When the re-encoding of 10 pieces of gold stone by FLC is completed, the total code amount of the 10 pieces is 1 Mbytes, so the free space on the magnetic disk is 1 Mbytes.

Images that have been re-encoded once are not re-encoded again. That is, the remaining IMByte s
Similar recording processing is performed to ensure recording of the 10 images to be taken from now on. That is, i (i>
10) When the total code amount of the magnetic disk exceeds 1900 bytes when the 1st image is recorded by VLC, and l is 19 or less, a new image is recorded by VLC (i
-10) images, the total code amount is (i -10)*
Re-encode with FLC so that it becomes 1oOKbytes.

FIG. 2 shows an embodiment of the image signal recording device of the present invention. Here, other parts of the camera that are not directly related to the present invention, such as the aperture and the diaphragm, are omitted. In FIG. 2, an optical image of a subject captured by a lens 1 is captured by an imaging device 2 located at the rear, such as a Change Co.
It is converted into a video electrical signal by an upgraded 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. Furthermore, the imaging device 2
Although not shown, video signal processing means such as comma correction, color signal formation/separation, white lance processing, and conversion to Y two-color difference are inserted between the A and/D transformations 3.

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

The compression encoding/decoding device 5 encodes the image data read out from the image memory 4 using the above-mentioned ADCT method,
Output to recording device 6. Alternatively, the code read from the recording medium by the recording device is decoded and stored in the image memory 4. It also has the function of simply counting compression codes.

The amount of code can be read by the control unit 7.

The control unit 7 integrates the functions of the devices and controls the entire system. That is, it manages a series of operations such as imaging, storage in the image memory 4, compression, and recording on a recording medium. It also manages files on the recording medium. The device 9 is a human interface including a release button and various operating members.

Normally, the control unit 7 performs recording using VLC according to the following procedure.

When the release button is pressed, the control unit focuses and
The aperture, shutter, etc. are operated to expose the imaging device and capture image information into the image memory 4.

The control unit sets the parameter F to the compression encoding/decoding device 5.
and instructs the recording device to output the compressed code. The control unit also instructs the recording device to receive, receive and record the compressed code.

Through the above processing, a variable length compression code is recorded on the recording device.

When the code amount of an image encoded by VLC exceeds a certain value, all the variable-length encoded codes are read out from the recording medium by the recording device 6, and the uncompressed image is read out by the compression encoding/decoding device 5. Decoded into information and stored in image memory 4
is accumulated in These processes are performed under the control of the control section 7, as in the case of encoding. Then, the control unit calculates the amount of code to be allocated to each image, and the image is encoded and recorded using FLC so that the amount of code is calculated.

The control unit 7 performs recording by FLC in the following procedure.

The control unit sets the parameter F to the compression encoding/decoding device 5.
is passed, the image data in the image memory 4 is compressed, and the code amount is counted. At this time, the compression encoding/decoding device 5 only counts the amount of codes for one screen without outputting the compressed codes.

This operation is repeated several times by trial and error while changing F until the desired code amount is achieved.

When F (hereinafter referred to as Fa) that generates the desired code amount is determined, the control unit again gives the parameter Fa to the compression encoding/decoding device 5 and instructs the recording device 6 to output the compressed code. . The control unit also instructs the recording device to receive, receive and record the compressed code.

The compressed code that has been made into a fixed length for each screen by the above processing is recorded on the recording medium of the recording device 6.

Next, the configuration of the compression encoding/decoding device 5 is shown in FIG.

In FIG. 4, 51 is a DCT/IDCT unit that performs discrete cosine transform and inverse transform. Reference numeral 52 denotes a quantization/inverse quantization unit, which performs quantization and inverse quantization of data according to quantization parameters set by the quantization table 53. 53 is a Huffman encoding/decoding unit, which performs Huffman encoding/decoding according to parameters from the Huffman table 56. A parameter setting register 54 holds data from the control unit 7 for changing the quantization parameters stored in the quantization table, and sends the data to the multiplier. 57 is a Huffman encoding/decoding unit 53
This is a counter that counts the amount of code output from.

The control unit 7 calculates data to be set in the parameter setting register 54 according to the count value of the counter 57.

Each section shown in FIG. 4 is controlled by the control section 7.

During encoding, image data from image memory 4 is subjected to DCT
/IDCT 51 performs discrete cosine transform, quantization/inverse quantization 52 quantizes, Huffman encoding/decoding section 53 performs Huffman encoding, and the result is stored in record bag M6.

Furthermore, when once decoding is performed for re-encoding, Huffman decoding, inverse quantization, and inverse DCT are performed on the encoded data stored in the recording device 6 in the reverse procedure to the above, and the obtained image data is stored in the image memory 4.

A detailed flowchart of the above embodiment is shown in FIG. Regarding the symbols in Figure 1: i, j, ivo, VL
Csum.

VLCvolume (), FLCvolume ()
, AIocArea is a variable, i m a x M V
, AV is a constant. 1 is the number of the image attached to the shooting type, ]vO is the first number of the image recorded by VLC, VLCsum is the total code amount of the image recorded by VLC and whose code length has not been adjusted yet, and the array VLCvolume (i) is the code length in VLC encoding of the i-th image, and the array FLCvolume (i)
is the target code length for adjusting the code amount for the i-th image, and AlocArea is the free space for temporarily recording a plurality of images recorded by VLC on the recording medium. MV is the total recordable capacity of the recording medium, and AV is the average allocated length per image. Therefore, the number of recordable sheets per recording medium imax is MV/AV
is given by

In step O, variables are initialized. i.e. 1-0.1vo
=1, VLCsurr+=O. AIocAre
a is obtained by subtracting the average data It AV from the total recording capacity MA. In other words, a margin of about - images is provided. In addition, imax uses the total recording capacity M A as the average data f
It is divided by iAV.

Step 1 waits for the release button to be pressed, and when the release button is pressed, exposure and writing to the image memory 4 are performed in step 2.

In step 3, the image in the image memory 4 is VLC encoded and written on the recording medium. The record code I at this time is V L C
Save in voIume(i).

In step 4, it is determined whether all code data has been recorded on the recording medium. If recording is successful, proceed to step 5. The case where data cannot be recorded means that there is at least a free capacity on the recording medium of the size of the average data fiAV, but this is a case where the capacity has been exceeded, and is an exceptional situation. In this case, in step 15, the number of sheets recorded up to now is compared with the guaranteed number of sheets. If more recordings than the guaranteed number have been made, recording on this recording medium will end. If the guaranteed number of sheets or more has not been recorded, in step 16 recording is performed in an empty area on the recording medium using FLC.

Then, the recorded code amount at this time is V L Cv o l u
Save in e(i). Then proceed to step 5.

In step 5, l and VLCsum are updated.

That is, i=i+1, VLCsum=VLCsum +VL
Let it be Cvolume(i).

In step 6, it is determined whether the guaranteed number of sheets has been recorded. If the guaranteed number of sheets is recorded (l≧i m
ax) Since there is no need to adjust the code amount, return to step 1 and wait for the release button to be pressed. If the guaranteed number of sheets is not recorded (if i<imax)
Proceed to step 7.

In step 7, it is checked whether VLCsum exceeds the allocated capacity AlocArea for variable length codes. If not, return to step 1. If it exceeds, proceed to step 8.

In a loop of steps 8 to 12, images lvO to i are re-encoded to adjust the amount of code.

In step 9, the amount of code to be allocated to image j is determined by the following equation.

FLcvolume (j) Equation (3), like Equation (2), allocates a code amount proportional to VLCvolume □.

(i-ivojil) represents the number of images for which code amount adjustment has not been performed. Therefore, ftLlf multiplied by AverageValue represents the total code amount allocated to (j-ivo+1) images.

In step IO, image j is decoded into the image memory.

In step 11, the code on the medium is erased, and the image on the image memory is subjected to FLC and recorded.

Since the re-encoding of (i-ivo+1) sheets has been completed in the loop of steps 8 to 12, in step 14 the variables IVo and VL are
Update Csum and AIocArea. Then return to step l.

[Other Embodiment C In the above embodiment, V L Cv o l
Although the amount of code is allocated in proportion to the size of u m e (]), it is not necessarily limited to this. For example, an image in which the size of VLCvolume (i) is less than or equal to AverageValue may not be re-encoded. In that case, the code amount is adjusted by re-encoding only the other images. As another example, V L Cv o I u m e
(i) A method may also be considered in which an image having a code amount of X or more is regarded as having a code amount of X and is distributed proportionally.

This idea takes advantage of the fact that images with a certain degree of complexity do not suffer much noticeable deterioration even when compressed.

Further, in the above embodiment, the apparatus automatically enters the re-encoding no-ken, but in step 7, the VL
When Csum > AlocArea, a warning is displayed to the user, prompting the user to adjust the code amount or replace the recording medium because the capacity is insufficient, and only when the user instructs to adjust the code amount. It is also possible to proceed to the No-ken after step 8.

In addition, in the above embodiment, the code amount is adjusted when the variable length code amount reaches a certain fixed amount, but when the number of images encoded by VLC reaches a certain fixed number, the code amount is adjusted. You may also do this. For example, every 5 pieces, 5
It is also possible to adjust the code amount by re-encoding on a sheet-by-sheet basis.

In addition, if you want to automatically adjust the code amount in any of the above cases, if you start adjusting the code amount during quick shooting, the quick shooting will stop, so you should not start adjusting the code amount during continuous shooting. Alternatively, the code amount may be adjusted after the quick copy is completed.

In addition, in the above embodiment, the first
The compression means and the second compression means that perform fixed-length compression share a common circuit, and are divided into cases where the quantization parameter is fixed and cases where it is variable to obtain a fixed length through trial and error. By setting the parameters, the first
, the function of the second compression means, but they may each have completely separate circuit configurations.

Moreover, the compression means and the expansion means may also be all (separate systems).

After recording by the above-described method, it can be displayed on a monitor using an image reproducing device having means for decoding the compressed code, or can be copied by a copying device.

Further, the recording medium may be one that uses a magnetic recording method such as a magnetic disk, one that uses an optical recording method such as an optical disk, or one that can record image data such as an IC card or a semiconductor memory such as a ROMSRAM.

Furthermore, the compression algorithm is not limited to the above-mentioned JPEG method, and may be, for example, arithmetic encoding, run-length encoding, Huffman encoding, or facsimile encoding methods such as MH, MR, and MMR. That is, any encoding method may be used as long as it enables both fixed-length compression and variable-length compression by changing the quantization parameter or encoding parameter during encoding, for example.

As is clear from the above description, according to the embodiment of the present invention, it is possible to allocate the amount of code according to the image while guaranteeing the number of recording sheets, so that the image does not deteriorate significantly. Further, since VLC is normally used, it can be compressed faster than FLC, so there is also the effect that a larger number of images can be taken in the camera's quick-shooting mode.

〔Effect of the invention〕

According to the present invention, image deterioration can be suppressed and images can be efficiently compressed.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the operation of an embodiment of the present invention, Fig. 2 is a block diagram of the embodiment, Fig. 3 is a diagram showing the relationship between parameter F and compression code amount, and Fig. 4 is compression coding. 3 is a diagram showing the configuration of a decoding unit 5. FIG. 3...A/D converter 4...Image memory...Compression encoding/decoding device Fig. 1(b)

Claims (9)

[Claims] (1) comprising a first compression means that performs variable length compression, a second compression means that performs fixed length compression, and an expansion means that expands the image signal compressed by the first or second compression means; After a plurality of images are once recorded on the recording medium by the first compression means, the recorded image signals are decoded by the expansion means, and fixed length compression is again performed by the second compression means. Features of the image signal recording device. (2) When performing fixed-length compression by the second compression means, a code amount is assigned to each image so that the total code capacity by fixed-length compression of the plurality of images becomes a certain code amount. The image signal recording device according to claim 1, characterized in that: (3) A claim characterized in that codes for individual images when fixed-length compression is performed by the second compression means are distributed in proportion to the amount of codes when compressed by the variable-length compression. The image signal recording device according to item 1. (4) For images whose code amount when compressed by the variable length compression has reached a certain code amount x or more, the code amount when compressed by the variable length compression is x. Claim 1 characterized in that it is regarded as
The image signal recording device described in 2. (5) An image according to claim 1, wherein an image whose code amount does not reach a certain size when compressed by the variable length compression is not subjected to fixed length compression again. Signal recording device. (6) Furthermore, it is equipped with means for detecting whether the total amount of variable-length compressed codes on the recording medium has reached a certain certain code amount, and when it has reached a certain amount, automatically demodulates the codes recorded by variable-length compression. 2. The image signal recording apparatus according to claim 1, wherein the image signal recording apparatus performs fixed-length compression again. (7) further comprising means for detecting whether the number of variable-length compressed images on the recording medium reaches a certain number;
2. The image signal recording apparatus according to claim 1, wherein the image signal recording apparatus automatically decodes the code recorded by variable length compression and performs fixed length compression again when the code reaches the specified length. (8) Furthermore, a means is provided for the user to instruct conversion from the variable length compression code to a fixed length compression code, and when the user instructs the conversion, the code recorded by variable length compression is decoded and fixed again. 2. The image signal recording apparatus according to claim 1, wherein the image signal recording apparatus performs long compression. (9) The image signal recording apparatus according to claim 1, wherein the variable length compression code is not converted to a fixed length compression code during continuous shooting.