JPH07146927A - Image file device - Google Patents

Abstract

PURPOSE:To efficiently store image data which has small deterioration in a recording medium and to reproduce and display them by encoding the image data in two stages of a 1st encoding method which compresses the data irreversibly and a 2nd encoding method which encodes the difference data between the original image data and 1st encoded data reversibly. CONSTITUTION:The 1st encoded data A encoded by a 1st encoder 4 which encodes the image data irreversibly and 2nd encoded data B encoded by a 2nd encoder 6 which compresses the difference data between the original image data and image data obtained by restoring the encoded data A irreversibly are stored on the recording medium 1. At the time of reproduction, only the encoded data A are restored for normal reproduction and display, but when the original image data are necessary, the encoded data A and B are restored and then added. Consequently, the image data having small deterioration can be stored on the recording medium 1 and they can be reproduced and displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image file device which stores a large number of image data in a recording medium and reproduces and displays a desired image as needed.

[0002]

2. Description of the Related Art Conventionally, halftone image data such as a TV signal has an enormous amount of information, and such image data can be efficiently recorded on a recording medium such as a magnetic disk or an optical disk and quickly. Various attempts have been made to compress image data for playback display. As one of such image data compression methods, a method utilizing orthogonal transformation and entropy coding of image data is well known, and recently it is being standardized as a compression method of a color still image (JPEG method).

In this method, digital two-dimensional image data is divided into blocks each having an appropriate number of samples (for example, 8 × 8), and each block is subjected to a two-dimensional discrete cosine transform (DCT) which is a kind of orthogonal transform. Then, the coefficient representing the energy component of the frequency composed of the DC component and the AC component is obtained,
Since energy is concentrated on a specific component by this conversion, a large energy component is finely quantized, while a small energy component is roughly quantized.

Further, Huffman coding, which is a kind of entropy coding, is performed on the quantized coefficient thus obtained. In this method, coding is performed by referring to a Huffman table to which a code having a code length corresponding to the appearance of the quantized coefficient is assigned, and a code with a short frequency becomes a quantized coefficient with a high frequency. A long code is assigned to reduce the code length for each block.

To restore the image coded data compressed in this way, a process reverse to the above is performed. That is, the original image signal can be restored by decoding the coded data using the Huffman table and subjecting the decoded quantized coefficient to the inverse orthogonal transform. In such a method, depending on the degree of coarseness of quantization, 1
It is possible to compress the encoded data amount from about / 5 to about 1/100.

[0006]

However, it is possible to perform coding at a low bit rate by roughly performing quantization as in the above method. However, when such image coded data is restored, the There is a problem that an unnatural discontinuous state occurs at the block boundary called block distortion due to the effect of the digitization error, and especially in a flat area where the image density change is small, the block distortion is conspicuous and the image quality is deteriorated. .

Further, noise spread around the contour, called mosquito noise, which occurs when the quantization error of the coefficient of the high frequency component generated at the contour edge portion appears in a distributed manner over the entire block, similarly causes deterioration of the image quality. . These two problems are essential problems when DCT and quantization are used, and there is a trade-off relationship between image quality and code amount.

In the case of an average natural image, if the code amount is about 1/20, the deterioration of the image quality is not noticeable visually, and an image aimed at accumulating a large number of image files and reproducing and displaying at a high speed. In a file device, image data is often compressed and stored with such a coding amount. However, 1/2
Even if the compression ratio is about 0, the above-mentioned noise is seen in detail in the character portion, the contoured portion, and the portion having a flat density. Especially in the image file device,
Not only displaying the accumulated image on the monitor, but also outputting it to the image printer, creating new image data by editing and processing, processing it so that it can be used in other systems, transferring it, etc. It is recommended that the original original image with no deterioration be saved as needed.
However, there is a problem that the original image has a large capacity and deteriorates the storage efficiency.

The present invention is intended to solve the above problems,
It is an object of the present invention to provide an image filing device capable of reproducing and displaying original image data without deterioration in image quality without significantly impairing the storage efficiency.

[0010]

In order to achieve the above object, the present invention has means for inputting image data and division of the image data into blocks of a specific size for orthogonal transformation, quantization, and irreversible data amount. First compressing means for compressing the data, second restoring means for restoring the first encoded data, and means for obtaining a difference between the first restored image data and the input original image data A second encoding means for reversibly compressing the difference data, a second restoring means for restoring the second encoded data, and a first restored data and a second restored data. Means for recording only the first encoded data or both the first encoded data and the second encoded data on a recording medium at the time of image recording, and at the time of image reproduction by the reproduction mode selection means. , In normal playback mode Only the first encoded data is read from the recording medium, the image restored by the first restoring unit is displayed on the display unit, and in the original image reproduction mode, the first encoded data and the second encoded data are displayed. By reading out, restoring by the first and second restoring means respectively, and adding the first restored data and the second restored data by the adding means,
And means for restoring the original image data and displaying it.

[0011]

According to the present invention, in the above structure, the first encoded data encoded by the first encoding means for irreversibly compressing the image data, the original original image data and the first encoded data. The difference data with respect to the restored image data obtained by restoring the data is recorded with the second encoded data obtained by encoding with the reversible second encoding means, and the first encoded data is reproduced during reproduction.
Original encoded data is restored, and when original image data is required, the first encoded data and the second encoded data are restored respectively, and the restored data is added, so that the original original image without deterioration is obtained. Image data can be obtained.

Here, most of the difference data has a value in the vicinity of 0, and the reversible second encoding means can sufficiently compress the data amount. Even if the two encoded data are combined, a sufficient amount of data can be saved from the original image data, and the original image data without deterioration can be efficiently stored in the recording medium.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of an image filing device according to the present invention, showing only the main parts relating to the present invention and omitting the other parts.

In FIG. 1, the mode selecting means 15 is constructed so as to select the recording / reproducing mode of the image filing apparatus. Further, in the recording mode, the normal recording mode and the original image recording mode can be selected. In the reproduction mode, the normal reproduction mode and the original image reproduction mode can be selected.
The system controller 2 controls all of the components according to the selection mode of the mode selection means 15. The recording medium 1 is composed of an optical disk, a hard disk, or the like, and files image data.

The image input controller 14 takes in an image signal from an external input device such as a video camera or a VTR,
This is an image input means for digitizing, and the digitized image data is written in the frame memory 10.

The frame memory 10 is a frame memory A,
It is composed of a plurality of frame memories B, and the input image data is written in either the frame memory A or the frame memory B. Hereinafter, in this embodiment, it is assumed that the input image is written in the frame memory A. The switching circuit 11 switches the output of the frame memory A or the frame memory B, and outputs the contents of either one of the frame memories to D.
It is constantly displayed on the monitor 13 through the / A converter 12.

The encoder A4 comprises a DCT circuit 41, a quantization circuit 42, and a Huffman coding circuit 43,
The contents of the frame memory A in which the input image selected by the selection circuit 9 is written are irreversibly encoded, and the encoded data is stored in the buffer memory 3.

When the normal image recording mode is selected by the mode selecting means 15, the encoder A of the buffer memory 3 is selected.
The encoded data A encoded by the system controller 2
It records on the recording medium 1 via. The decoder A5 includes a Huffman decoding circuit 53, an inverse quantization circuit 52, an inverse DCT circuit 5
1 and is decoded by the encoder A, and the decoded image data is written in the frame memory selected by the selection circuit 9.

When the original image recording mode is selected by the mode selection means 15, the encoded data A encoded by the encoder A of the buffer memory 3 is decoded by the decoder A5 and input by the selection circuit 9. The other frame memory B in which the image data is not stored is selected, and the decoded image data is written there.

Further, the arithmetic circuit 8 calculates the difference between the frame memory A storing the original image data and the frame memory B storing the decoded image. The encoder B is composed of a DPCM circuit 61 and a Huffman encoding circuit 62, which are a type of predictive encoding method, reversibly encodes the difference data, and stores the encoded data B in the buffer memory 3. The encoded data A and the encoded data B are respectively written in different addresses of the buffer memory 3, and the encoded data A and the encoded data B are collectively written in the recording medium 1 via the system controller 2.

When the normal reproduction mode is selected by the mode selection means 15, only the encoded data A from the recording medium 1 is buffer memory 3 through the system controller 2.
, The decoded image A is decoded by the decoder A5, and the decoded image A is written in the frame memory (in this embodiment, the frame memory A) selected by the selection circuit 9. The switching circuit 11 switches the output of the frame memory 10 to the frame memory A, and D
Display on the monitor through the / A converter 12.

When the original image reproduction mode is selected by the mode selecting means 15, the coded data A and the coded data B are read from the recording medium 1 to the buffer memory 3 via the system controller 2, and the decoder A5 is used. The encoded data A is decoded by the frame memory A selected by the selection circuit 9.
The decoded image data A is written in. Further, a decoder B including a Huffman decoding circuit 72 and an inverse DPCM circuit 71
The encoded data B is decoded in 7, and the decoded difference data B and the decoded image data A stored in the previously decoded frame memory A are sequentially added by the arithmetic circuit 8 and written in the frame memory B. That is, the original original image data is written in the frame memory B. The switching circuit 11 switches the output of the frame memory 10 to the frame memory B, and D
The original image data is displayed on the monitor through the / A converter 12.

FIG. 3 is a general example showing the frequency distribution of the values of the difference data between the original image data and the decoded data A obtained by decoding the coded data A. As shown in this figure, the frequency distribution is concentrated in the vicinity of 0,
Since the data is statistically biased, the data using the DPCM of the encoder B of this embodiment can be sufficiently compressed.

Further, FIG. 2 shows the configuration of another embodiment of the encoder B and the decoder B. Encoder B60
0 is composed of a DCT circuit 601 and a Huffman coding circuit 602. The decoder B700 is a Huffman decoding circuit 702.
And an inverse DCT circuit 701. In this case, DCT
The DCT coefficient of the output of the circuit 601 can be sufficiently compressed by the Huffman coding circuit 602 without being quantized due to the above-mentioned statistical property.

That is, there is no deterioration due to the quantization error described in the above problem, and the Huffman decoding circuit 702 and the inverse DCT
The circuit 701 returns to the original image data. However, DC
Since there is a possibility that an arithmetic rounding error inside the T circuit 601 and the inverse DCT circuit 701 may occur, it does not always return to the original image data. However, even in this case, no difference is visually recognized compared with the original image.

FIG. 4 is a schematic diagram comparing the data amounts of the original image data and the coded data according to the embodiment of the present invention. In the normal recording mode, only the encoded data A is recorded.
In the original image recording mode, the encoded data A and the encoded data B are recorded as a series of data. When the data recorded in the original image recording mode is reproduced in the normal reproduction mode, only the encoded data A is reproduced, and in the original image reproduction mode, the encoded data A and the encoded data B are reproduced.

[0027]

As described above in detail, according to the present invention, the original image quality is deteriorated by encoding the image data in two stages by the first and second encoding methods. The amount of data can be compressed without any problem, the data can be efficiently stored in the recording medium, and the original image data without deterioration can be reproduced and displayed.

In normal reproduction, only the first coded data is reproduced, and the first and second coded data are reproduced as required, so that the high-speed reproducibility is not impaired and the response is high. It is possible to provide a good image file device.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an image filing device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of another embodiment of an encoder B and a decoder B.

FIG. 3 is a schematic diagram showing a frequency distribution representing statistical characteristics of difference data according to the present invention.

FIG. 4 is a schematic diagram comparing the data amounts of encoded data and original image data according to the present invention.

[Explanation of symbols]

 1 Recording Medium 2 System Controller 3 Buffer Memory 4 Encoder A 5 Decoder A 6 Encoder B 7 Decoder B 8 Arithmetic Circuit 9 Selection Circuit 10 Frame Memory 11 Switching Circuit 12 D / A Converter 13 Monitor 14 Image Input controller 41 DCT circuit 42 Quantization circuit 43 Huffman coding circuit 51 Inverse DCT circuit 52 Inverse quantization circuit 53 Huffman decoding circuit 61 DPCM circuit 62 Huffman coding circuit 71 Inverse DPCM circuit 72 Huffman decoding circuit 600 Encoder B 601 DCT circuit 602 Huffman coding circuit 700 Decoder B 701 Inverse DCT circuit 702 Huffman decoding circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H04N 7/30 H04N 7/133 Z (72) Inventor Yoshinori Amano 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Denki Sangyo Co., Ltd.

Claims (1)

[Claims] 1. A means for inputting image data, a first encoding means for dividing the image data into blocks of a specific size, performing orthogonal transformation, quantizing, and irreversibly compressing a data amount; A first decompression means for decompressing the first encoded data, a means for taking a difference between the first decompressed image data and the input original image data, and a second for reversibly compressing the difference data Encoding means, second restoring means for restoring the second encoded data, and means for adding the first restored data and the second restored data, and at the time of image recording, the first Of the first coded data or both the first coded data and the second coded data are recorded on a recording medium, and when the image is reproduced, the mode selection means causes the first coded data to be recorded in the normal reproduction mode. Read only from the recording medium Then, the image restored by the first restoring unit is displayed by the displaying unit, and in the original image reproduction mode, the first encoded data and the second encoded data are read out, and the first and second encoded data are read out, respectively. An image file device comprising means for restoring the original image data by restoring by the restoring means, and adding the first restored data and the second restored data by the adding means. .