JPH10210466A - Data-compressing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically compress generated data down to an amount compatible with a relevant degree of difficulty merely through selection of the desired data of an operator by producing a control instruction for the amount of generated data according to the category of the degree of difficulty corresponding to the data to be compressed. SOLUTION: A category ID is set to each of dynamic image data to be compressed to previously show each degree of difficulty. A CPU 11 gives a control instruction for an amount of generated data to a bit rate control part 114 of a compression circuit 15, based on the corresponding relation stored in a table 12a contained in a ROM 12, so that the amount of generated data is secured corresponding to the category ID corresponding to the dynamic image data to be compressed. Thus, an operator can be set free from such inconveniences whereby he must set a category ID at each time. Then the experiences and the technical knowledge of the operator are required only for setting a category ID at first. Thereafter, a dynamic image data compressing device 1 automatically instructs a proper amount of generated data according to the relevant degree of difficulty. As a result, a properly reproduced image can always be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression apparatus capable of compressing data and adjusting the amount of generated data.

[0002]

2. Description of the Related Art Conventionally, for example, MPEG (Moving Picture)
In a compression apparatus that compresses moving image data using a method such as re Image Coding Experts Group (re Image Coding Experts Group), an operator may compress the moving image data so as to have a predetermined generated data amount or perform an operation before compressing the moving image data. Each time, the amount of generated data is set so as to correspond to the content of the moving image to be compressed.

[0003]

However, when compression is performed with a predetermined amount of generated data, the reproduced image may not be sufficiently satisfactory depending on the image content. For example, in the case of an image having a small temporal / spatial correlation, that is, an image having a high degree of difficulty, the image quality deteriorates unless a certain amount of generated data is secured. Conversely, if the generated data amount determined on the premise of such a high degree of difficulty is applied to an image with a low degree of difficulty, the compression efficiency is reduced. Therefore, as described above, the amount of generated data according to the image content is set and compressed each time, but when compressing a large number of images, the operation of the setting is required every time, and there is complexity. .

Further, in determining the amount of generated data of the image, specialized knowledge is also required, and it is very difficult for an inexperienced operator to determine an appropriate amount of generated data. The above-mentioned problem occurs not only in the case of handling image data but also in the case of other data having a difference in difficulty in compression.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. Just by an operator selecting desired data, a compression process is automatically performed with a generated data amount suited to the difficulty level. It is an object of the present invention to provide a data compression device capable of performing the following.

[0006]

In order to achieve the above object, a data compression apparatus according to claim 1 is capable of compressing data and adjusting the amount of generated data. A data compression device comprising:
A difficulty category is set in advance for each of the data to be compressed, and the amount of generated data to the compression unit is set so that the amount of generated data is in accordance with the difficulty category corresponding to the data to be compressed. The present invention is characterized in that it comprises an adjustment instruction means for giving an instruction for the adjustment.

In the case where the data to be compressed is moving image data, the difficulty level becomes more difficult as the temporal and spatial correlation of the moving image data decreases. It is conceivable to set the degree to be higher. As a specific example, a so-called CG (computer graphics) image or a natural image often has little temporal and spatial correlation, and it is considered appropriate to set a high difficulty level. In addition, it is considered appropriate to set relatively low difficulty levels for images such as animations and movies.

Of course, the degree of difficulty varies depending on the content of a natural image, and these may be appropriately set in consideration. For example, even if the same mountain scenery image is present in a distant place and does not particularly move, and when there is no detailed part, the difficulty level becomes low. Conversely, if it is nearby, for example, a landscape that appears in the details of the forest and the branches and leaves flutter in the wind, the difficulty level is high. Similarly, even if the category of sports is considered, there are some types of sports that are intense and some that are not so depending on the type of sports, and the level of difficulty naturally increases.

The compression means of the data compression apparatus is capable of compressing data and adjusting the amount of generated data. A difficulty category is set in advance for each of the target data, and the adjustment instructing unit sends the generated data to the compression unit so that the amount of generated data corresponds to the difficulty category corresponding to the data to be compressed. Give an instruction to adjust the amount.

For example, as described in the specific example of the moving image data described above, the difficulty level is often not constant depending on the data to be compressed. Will be unsatisfactory in the reproduced state. For example, the reproduced image does not have sufficient quality. Therefore, the amount of generated data according to the data content to be compressed is set each time and compression is performed, but it is a very cumbersome operation and it is difficult to determine an appropriate amount of generated data without experience and expertise. difficult.

Therefore, as in the present data compression device,
By adopting a configuration in which an adjustment instruction is given to each of the data to be compressed so that the generated data amount corresponds to the difficulty category set in advance, the trouble of the operator setting each time is eliminated. Then, it is only necessary to use experience and expertise only when setting the difficulty category first, and then the device automatically instructs the appropriate amount of generated data according to the difficulty category, so that the appropriate playback state is always set Obtainable. In particular, when the degree of difficulty varies considerably, such as moving image data, such an adjustment instruction is very effective.

The information indicating the difficulty category is as follows:
It may be added to each data. For example, this category information is put in the header information of each data.
Also, the correspondence between the difficulty category and the generated data amount is stored, and the generated data amount corresponding to the data to be compressed is determined based on the stored correspondence, and the determined generated data amount and It may be configured to give an adjustment instruction in such a manner.

[0013] As for the data to be compressed,
The present data compression apparatus itself may be provided with storage means and stored in the storage means, or the data compression apparatus itself may not be stored and may be configured to compress and input data input from outside. May be. This is particularly effective when the degree of difficulty is considerable, such as moving image data.However, the data is not limited to moving image data but may be audio data. It is equally applicable and effective.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. This embodiment is an example in which the data compression device is applied as a moving image compression device based on MPEG2.

As shown in FIG. 1, a moving image compression apparatus 1 according to this embodiment is a control means for controlling the entire apparatus.
CPU 11 corresponding to "adjustment instruction means" and its CP
ROM 12 which is a storage means for storing a program to be executed by U11 and which also corresponds to "correspondence storage means"
A hard disk drive (HDD) 14 for storing moving image data to be compressed, and a compression circuit 15 as a "compression means".
And these are mutually connected via a bus 20.

As shown in FIG. 3, a data ID and a category ID are added to the moving image data stored in the HDD 14 as header information. The category ID is information for identifying a category set by reflecting the degree of difficulty of moving image data. It is conceivable that the difficulty level is set based on the magnitude of the temporal and spatial correlation. For example, a so-called CG (computer graphics) image or a natural image has little temporal and spatial correlation. In many cases, setting a higher difficulty level is appropriate. Also, it is considered appropriate to set the difficulty level relatively low for images such as animations and movies. Therefore, these may be collectively set as one category.

Of course, the level of difficulty also occurs in the above-described natural image depending on the image content, and these may be appropriately set in consideration of the level of difficulty. For example, even if the same mountain scenery image is present in a distant place and does not particularly move and has no detailed portion, the difficulty level becomes low. Conversely, if it is nearby, for example, a landscape that appears in the details of the forest and the branches and leaves flutter in the wind, the difficulty level is high. Similarly, even when considering the category of sports, the level of difficulty can be naturally increased due to the difference between those that move rapidly and those that do not, depending on the type of sports. Therefore, a category with these distinctions may be set.

In the ROM 12, as shown in FIG. 4, a table 12a indicating a correspondence relationship between a category ID indicating a difficulty level and a generated data amount is stored. this is,
In consideration of the difficulty level described above, an appropriate amount of generated data is set according to the difficulty level. In order to appropriately set the above-described difficulty category and the amount of generated data, experience and expertise are required. Therefore, it is preferable that a person having such experience and knowledge set the above.

As described above, the moving image data stored in the HDD 14 is set with the category ID as the header information, and the ROM 12 stores the table 12a indicating the correspondence between the category ID and the generated data amount. Therefore, when the moving image data read from the HDD 14 is compressed by the compression circuit 15 and output, the CPU 11
Issues an adjustment instruction based on the correspondence stored in the table 12a so that the compression processing executed by the compression circuit 15 has an appropriate generated data amount according to the moving image data to be compressed. This adjustment instruction will be described later.

Next, the internal configuration of the compression circuit 15 will be described. As shown in FIG. 2, the compression circuit 15 receives moving image data and outputs it as digital data having a reduced data amount. The image memory 101 stores moving image data to be data-compressed. A subtraction unit 102 that performs a subtraction process between pixel value data and reference data, a DCT unit 103 that performs an orthogonal transformation unit that performs a DCT (discrete cosine transform) process, which is a type of orthogonal transformation, and an input from the DCT unit 103 A quantization unit 104 as quantization means for quantizing DCT coefficient data;
4, a variable length encoding unit 105 as a variable length encoding unit for performing variable length encoding on the DCT coefficient data quantized, and buffering the data encoded by the variable length encoding unit 105 A transmission buffer unit 106 for outputting to a subsequent separation / multiplexing unit (not shown), an inverse quantization unit 107 for inversely quantizing the DCT coefficient data quantized in the quantization unit 104, and an inverse thereof. Quantization unit 1
ID for the DCT coefficient data inversely quantized at 07
IDCT unit 10 for performing a CT (Inverse Discrete Cosine Transform) process
8, an adder 109 for adding motion compensation to data returned to the image data before the IDCT processing by the IDCT unit 108, and an output from the adder 109 for motion inter-frame prediction. A frame memory unit 110, a motion vector detecting unit 111, and a motion compensating unit that selects pixel value data of a corresponding macroblock unit in the previous frame according to the motion vector detected by the motion vector detecting unit 111. 112 and a bit rate control unit 114.

In the compression circuit 15, the input moving image data to be compressed is taken into the image memory 101 and is temporarily stored. In the present embodiment, since a macroblock of 16 × 16 pixels is processed as one unit for compression, the data is rearranged in macroblock units and output. The pixel data in macroblock units, which is the output of the image memory 101, is sent to the subtraction unit 102 and the motion vector detection unit 111. The motion compensation unit 1 is included in the subtraction unit 102.
The prediction data from the pixel data 12 is also input, and the difference data (prediction error) between the pixel data and the prediction data is output to the DCT unit 103.

The DCT unit 103 performs a DCT (Discrete Cosine Transform) process on the difference data output from the subtraction unit 102. At this time, the calculation is performed in predetermined block units (for example, every 8 × 8 pixels). In DCT operation,
An 8 × 8 coefficient is obtained as an output. In the present embodiment, the coefficients (hereinafter, also referred to as “DCT coefficients”) are arranged in the order of frequency components and output to the quantization unit 104.

In the quantization section 104, the DCT inputted from the DCT section 103 has a step size selected according to the quantization characteristic control signal from the bit rate control section 114.
The coefficient is quantized, and the quantized value is transmitted to the variable length coding unit 1
Output to 05. The variable length coding unit 105 performs a significant block determination and the like based on the coding control signal from the bit rate control unit 114, performs variable length coding on the quantized DCT coefficient, and outputs it to the transmission buffer unit 106. In this variable-length coding, for example, it is conceivable that after the output of the quantization unit 104 is run-length-transformed, the coefficient is converted into a variable-length code and output as compressed data. Run-length encoding results in two coefficients, the set of the number of zero coefficients and the value of the next non-zero coefficient,
Since the output of the quantization unit 104 tends to have a large number of zero coefficients, the amount of data is reduced by performing run-length encoding. Next, two coefficients that are the result of the run-length encoding are put together, and one variable-length code is assigned and output, so that compressed data is obtained.

On the other hand, the inverse quantization unit 107 includes the quantization unit 1
Since the quantized DCT coefficient output from the input unit 04 is input, inverse quantization is performed using the quantization step size selected in the quantization unit 104, the DCT coefficient is calculated and output to the IDCT unit 108. I do. Since the result at this time is a value including an error due to quantization, IDCT section 108 performs IDCT (inverse discrete cosine transform) processing on the DCT coefficient input from inverse quantization section 107 and outputs the result to addition section 109. I do.

The addition section 109 adds the output from the IDCT section 108 and the output from the motion compensation section 112 and outputs the result to the frame memory section 110. Frame memory unit 11
Reference numeral 0 denotes a frame memory for motion compensated inter-frame prediction, which is composed of at least two frame memories. Then, at the same time as accumulating the pixel value output from the adding unit 109, the pixel data of the previous frame is output to the motion vector detecting unit 111 and the motion compensating unit 112 for motion compensated frame prediction.

The motion vector detecting section 111 reads out pixel data of the previous frame near the processing macroblock position of the current frame from the frame memory section 110 as a motion vector search window (search area).
A motion vector is detected by performing a block matching operation, and the detected motion vector is output to the motion compensation unit 112. Further, the motion vector detected by the block matching calculation is also output as a motion vector for an adjacent macro block.

In accordance with the motion vector detected by the motion vector detecting section 111, the motion compensating section 112 reads out the pixel data of the corresponding macroblock unit of the previous frame from the frame memory section 110 and outputs it to the subtracting section 102 as predicted value data. I do. This is a schematic operation relating to data compression, and as described above, efficient compression of data can be realized by employing, for example, run-length encoding and variable-length code.

The bit rate control unit 114
Acquires the generated data amount from the CPU 11 (see FIG. 1) as the content of the adjustment instruction. Then, the quantization unit 1 sets the bit rate according to the instructed generated data amount.
04 and the inverse quantization unit 107 are controlled to change the quantization step value. The quantization unit 104 selects a quantization step size in accordance with an instruction from the bit rate control unit 114, and
The T coefficient data is quantized, and thereby, a variable bit rate function is exhibited.

In the moving picture compression apparatus 1 of the present embodiment having the above configuration, the compression circuit 15 can compress the moving picture data, and the bit rate control unit 114 controls the bit rate to generate the moving picture data. The amount of data can be adjusted. As shown in FIG. 3, a category ID indicating the degree of difficulty is set in advance for each moving image data to be compressed, and the CPU 11 generates a data amount corresponding to the category ID corresponding to the moving image data to be compressed. In accordance with the correspondence stored in the table 12a in the ROM 12, the bit rate control unit 114 of the compression circuit 15 is instructed to adjust the generated data amount.

Since the degree of difficulty of moving image data to be compressed is not constant, if the compression is performed with a fixed generated data amount, the reproduced image may not be sufficiently satisfied depending on the data content. Therefore, the amount of generated data according to the content of the moving image data is set each time and compressed, but it is a very cumbersome operation and it is difficult to determine an appropriate amount of generated data without experience and expertise. difficult.

Therefore, as in the main moving picture compression apparatus 1, by adopting a configuration in which adjustment is instructed so as to have a generated data amount corresponding to a category ID preset for each moving picture data to be compressed, The trouble of the operator setting each time is eliminated. And you only have to use your experience and expertise when setting the category ID for the first time,
Thereafter, the moving image compression apparatus 1 automatically instructs an appropriate amount of generated data according to the difficulty level, so that an appropriate reproduced image can always be obtained.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. Is easily inferred. For example, regarding the moving image data to be compressed, in the case of the moving image compression device 1 of the above embodiment, the device 1 itself is H
Although the DD 14 is provided and stored in the HDD 14, the moving image compression apparatus 1 itself may not be stored and may be configured to compress and output moving image data input from the outside.

Also, the compression circuit 15 of the above-described embodiment
Although the configuration is such that compression processing based on the EG2 standard is performed, the compression encoding standard to be adopted is not limited to MPEG2, and the compression processing is performed based on another standard for compressing moving image data. You may make it apply.

Although the above embodiment is applied to a moving image compression apparatus, the same problem may occur not only when image data is handled as data to be compressed but also when other data is used. If
It is still effective. For example, the data may be audio data, and the difficulty category in that case may be, for example, speech, music performance, or nature. However, this is particularly effective in the case where the degree of difficulty is considerably large such as moving image data.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a moving image compression device according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of a compression circuit according to the embodiment.

FIG. 3 is an explanatory diagram showing moving image data and its header information.

FIG. 4 is an explanatory diagram of a table showing a correspondence relationship between a category ID indicating a degree of difficulty and a generated data amount.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Moving image compression apparatus 11 ... CPU 12 ... ROM 13 ... RAM 14 ... Hard disk drive 15 ... Compression circuit 101 ... Image memory 102 ... Subtraction unit 103 ... DCT unit 104 ... Quantization unit 105 ... Variable length encoding unit 106 ... Transmission Buffer unit 107: inverse quantization unit 108: IDC
T unit 109 addition unit 110 frame memory unit 111 motion vector detection unit 112 motion compensation unit 114 bit rate control unit

Claims (4)

[Claims] 1. A data compression apparatus comprising compression means capable of compressing data and adjusting an amount of generated data, wherein a difficulty category is set in advance for each data to be compressed, A data compression apparatus, comprising: an adjustment instruction unit that instructs the compression unit to adjust an amount of generated data so that the amount of generated data corresponds to the difficulty category corresponding to data to be compressed. 2. The data to be compressed is moving image data, and the difficulty category is set so that the degree of difficulty increases as the temporal and spatial correlation of the moving image data decreases. The data compression device according to claim 1, wherein 3. The information indicating the difficulty category is added to each data.
A data compression device as described. 4. A correspondence storage means for storing a correspondence relation between the difficulty category and the amount of generated data, wherein the adjustment instruction means is based on the correspondence relation stored in the correspondence storage means. And determining an amount of generated data corresponding to the data to be compressed and instructing the compression means to adjust the amount of generated data to the determined amount of generated data. 3. The data compression device according to 3.