JPH089387A - High frequency component controller - Google Patents

Abstract

PURPOSE:To suppress the decline of the resolution of output pictures accompanying the increase of a data amount to be encoded in a high efficiency encoder for digital image communication. CONSTITUTION:A coefficient control part 13 judges the data amount to be encoded by an encoding operation part 113 based on a quantization step width W obtained by a residual amount calculation part 115. Then, when the data amount increases, an image data correction coefficient X for line conversion is controlled so as to suppress the high frequency component of image data to be encoded. Thus, since the decrease of the storage tesidual of a buffer memory 14 is suppressed even when the data amount to be encoded increases, the increase of the quantization step width W is suppressed. As a result, the decline of the resolution of the output images is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency component control device for controlling high-frequency components of image data coded based on a differential coding method in a high-efficiency coding system for digital image communication, for example. Regarding

[0002]

2. Description of the Related Art Generally, in a high efficiency coding system for digital image communication, a differential coding system is adopted as a coding system. Here, the differential encoding method is a method of obtaining a difference value between the input signal and the prediction signal and encoding the difference value.

In the high-efficiency coding system using the differential coding method, when the background of the input image becomes complicated, the amount of image data to be coded increases, and as a result,
The amount of encoded image data, in other words, the amount of image data to be transmitted via the communication line also increases.

On the other hand, the data transmission amount of the communication line for transmitting the encoded image data is constant. Therefore, when the amount of encoded image data increases and exceeds the data transmission amount of the communication line, it becomes impossible to transmit the image data.

In order to deal with this problem, in the conventional high-efficiency coding system, a buffer memory for temporarily storing coded image data is provided, and the coded image data is delayed by the buffer memory. The difference between the amount of data and the amount of data transmitted on the communication line is absorbed.

[0006]

However, in the high-efficiency coding system having the above-mentioned structure, there has been a problem that the resolution of the output image is conventionally lowered when the amount of data to be coded is increased. This will be described below.

In this high-efficiency coding system, if the background of the input image becomes complicated, the buffer memory may become full and a part of the coded image data may be discarded. When the image data is discarded, on the receiving side, for example, a part of the screen is not reproduced
An unnatural reproduced image in which the motion of the moving image is jerky can be obtained.

To solve this problem, the storage capacity of the buffer memory should be increased. However, if the storage capacity of the buffer memory is increased, the delay amount of this memory increases, and it becomes impossible to transmit image data in real time.

Therefore, conventionally, when the remaining memory capacity of the buffer memory becomes small, the quantization step width for quantizing the image data is increased.

With such a configuration, when the remaining memory capacity of the buffer memory decreases, the number of bits of image data to be encoded decreases. As a result, the number of bits of the encoded image data also decreases, so that the buffer memory is prevented from filling up.

However, with such a configuration, although the reproduction of an unnatural image is prevented as much as possible, when the remaining memory capacity of the buffer memory becomes small, the quantization step width becomes large, so that the resolution of the output image deteriorates. , The image quality is degraded.

[0012]

In order to solve the above-mentioned problems, the present invention shows the means for outputting information indicating the amount of data coded based on the differential coding method, and the output information of this means. A means for controlling the high frequency component of the data is provided so that the high frequency component of the data is suppressed when the amount of data to be stored increases.

[0013]

In the above structure, when the amount of data to be encoded is small, the high frequency component of the data to be encoded is emphasized. On the other hand, when the amount of data to be encoded increases, the high frequency component of the data to be encoded is suppressed according to the increase.

Therefore, when the present invention is applied to the high-efficiency coding system for digital image communication, when the amount of data to be coded is small, the contour of the image is emphasized and a clear image can be obtained. On the other hand, when the amount of data to be encoded increases, the high frequency component of the image data to be encoded is suppressed according to the increase, so that the amount of data to be encoded is suppressed from increasing.

As a result, the decrease in the remaining memory capacity of the buffer memory is suppressed, and the increase in the quantization step width is suppressed. As a result, the deterioration of the resolution of the output image is suppressed, and the accompanying deterioration of the image quality is suppressed.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. In the following description, the case where the present invention is applied to a high efficiency coding system for digital image communication will be described as a representative.

In the figure, reference numeral 11 is an encoding unit for encoding image data (analog image signal). Reference numeral 12 denotes a coefficient storage memory unit that holds the image data correction coefficient X for converting the number of lines. 13 controls the image data correction coefficient X based on the quantization step width W,
It is a coefficient control unit that controls a high frequency component of image data to be encoded. Here, the image data to be encoded is the image data encoded by the encoding operation unit 113 described later.

In the encoding unit 11, the reference numeral 111 separates the input image data into a luminance signal Y and a color difference signal C, and converts each of the signals Y and C into a digital signal.
-C separation part.

A line conversion unit 112 converts the number of lines of the input image data into the number of lines of an intermediate format (CIF) for image coding by an interpolation process using the image data correction coefficient X. Input image data is NTSC
If it is a signal, the number of lines is converted from 240 (NTSC) to 288 (CIF).

Reference numeral 113 is an encoding operation unit which encodes the input image data based on the difference encoding method by performing DCT operation, motion compensation operation, Huffman encoding and the like. Reference numeral 114 is a buffer memory that temporarily stores the encoded image data in order to absorb the difference between the amount of encoded image data and the data transmission amount of the communication line.

Reference numeral 115 is a remaining amount calculation unit for obtaining the quantization step width W of the A / D conversion / YC separation unit 111 based on the remaining storage amount of the buffer memory 114. The quantization step width W is represented by 5 bits, for example.

In the coefficient storing memory unit 121, 121
Is a memory for storing the image data correction coefficient X. The memory 121 has four storage areas R1,
It is divided into R2, R3 and R4. Each region Rn (n =
Image data correction coefficients X having different values are stored in 1, 2, 3, 4).

That is, the region R1 stores the image data correction coefficient X having the lowest suppression degree of the high frequency component (the highest degree of edge enhancement), and the region R2 has the second lowest suppression degree of the high frequency component. The image data correction coefficient X (the edge enhancement degree is second highest) is stored.

The region R3 stores the image data correction coefficient X in which the degree of suppression of high frequency components is the third lowest (the degree of edge enhancement is third highest), and the region R2 has the highest degree of suppression of high frequency components. The image data correction coefficient X (having the lowest edge enhancement degree) is stored.

In each region Rn, for example, 8
Each image data correction coefficient X is stored. And
Each image data correction coefficient X is composed of, for example, 8-word data.

In the coefficient control unit 13, 131 is a control unit which outputs a 2-bit address A1 for selecting one of the four regions R1, R2, R3 and R4 of the memory 121. The control unit 131 controls the quantization step width W
The amount of image data to be encoded is determined based on the four ranks, and the address A1 is output based on the determination result.

When the amount of image data to be encoded is ranked, the variable range may be equally divided into four, or the size may be changed for each rank and divided into four. You may

Reference numeral 132 denotes eight image data correction coefficients X stored in the area Rn selected by the control unit 131.
Is a counter that outputs a 3-bit address A2 for sequentially reading The addresses A1 and A2 are combined with A1 as an upper address and A2 as a lower address, and are supplied to the coefficient storing memory unit 12 as a read address A of the image data correction coefficient X.

The counter 132 outputs the address A2 for a predetermined period by counting the clock CK for a predetermined period based on the synchronization signal S supplied from the control unit 131. This is because, for example, when the above-described DCT calculation or motion compensation calculation is performed, the size of the image processing block is different for each calculation.

The operation of the above configuration will be described. First, the encoding operation of the encoding unit 11 will be described.

The input image data (analog image signal) of the encoding unit 11 is supplied to an A / D conversion / YC separation unit 111, separated into a luminance signal Y and a color difference signal C, and then each signal Y, Sampled every C. Each sampling output is quantized based on the quantization step width W obtained by the remaining amount calculation unit 115, and then encoded. As a result, a pulse code modulation signal is obtained.

The modulated output is supplied to the line conversion unit 112 and subjected to line conversion processing by interpolation processing using the image data correction coefficient X read from the coefficient storage memory unit 12. This converted output is supplied to the encoding calculation unit 113 and encoded based on the differential encoding method.
This encoded output is temporarily stored in the buffer memory 114 and then supplied to an image data transmission unit (not shown).

At this time, the remaining capacity of the buffer memory 114 is constantly monitored by the remaining capacity calculator 115. The remaining amount storage unit 115 sequentially obtains the quantization step width W based on the remaining storage amount. The data indicating the obtained quantization step width W is used for the YC separation / AD conversion unit 111.
Is supplied to the control unit 131 of the coefficient control unit 13.

The quantization step width W is calculated by the buffer memory 1
If the remaining storage capacity of 14 is large, it is set to a small value, and if it is small, it is set to a large value. As a result, if the storage capacity of the buffer memory 114 is large, the resolution of the output image is high, and if it is small, the resolution is low, but the buffer memory 114 is prevented from being full.

The above is the operation of the encoding unit 11. next,
The high frequency component control operation which is a feature of the present invention will be described.

As described above, the quantization step width W is set to a small value when the storage capacity of the buffer memory 114 is large, and set to a large value when it is small. The remaining storage capacity of the buffer memory 114 increases when simple image data such as a background is input, and decreases when complicated image data is input. That is, the buffer memory 1
The storage remaining amount of 14 increases when the amount of data to be encoded is small, and decreases when the amount of data to be encoded is large.

Focusing on this point, the control unit 131 of the coefficient control unit 13 determines the amount of data to be encoded based on the quantization step width W obtained by the remaining amount calculation unit 115. In this case, the control unit 131 divides this data amount into four ranks for determination as described above. Then, based on this determination result, any one of the four regions R1 to R4 is selected.

It is now assumed that the amount of data to be encoded is, for example, the smallest rank. In this case, the control unit 13
1 outputs the address A1 that selects the region R1. Accordingly, in this case, the line conversion process is performed based on the image data correction coefficient X having the lowest suppression degree of the high frequency component. As a result, in this case, the contour of the output image is most emphasized and the image with the sharpest contour is obtained.

In this state, when the background of the input image becomes complicated and the amount of data to be encoded increases, the remaining memory amount of the buffer memory 114 decreases. As a result, the quantization step width W increases, and the resolution of the output image decreases. However, this decrease is suppressed by the following operation.

That is, when the quantization step width W becomes large and the control unit 131 determines that the amount of data to be encoded is the second smallest rank, the control unit 131 selects the region R2 this time. The address A1 is output. As a result, this time, the line number conversion processing is performed based on the image data correction coefficient X in which the degree of suppression of high frequency components is the second lowest. As a result, in this case, the high frequency components of the image data to be encoded are suppressed more than in the case where the region R1 is selected.

Since the high frequency component of the image data to be encoded is suppressed, the increase in the amount of data to be encoded is suppressed. As a result, the decrease in the remaining storage capacity of the buffer memory 114 is suppressed, and thus the increase in the quantization step width W is suppressed. As a result, the reduction in the resolution of the output image is suppressed.

Similarly, the regions R3 and R4 are sequentially selected as the amount of data to be encoded increases. Thereby, the high frequency components of the image data to be encoded are sequentially suppressed, and the increase in the amount of data to be encoded is sequentially suppressed. As a result, the decrease in the remaining storage capacity of the buffer memory 114 is sequentially suppressed, so that the expansion of the quantization step width W is sequentially suppressed. As a result, the reduction in the resolution of the output image is sequentially suppressed.

Next, when the region R4 is selected and the background of the input image becomes simple and the amount of data to be encoded decreases, the remaining memory amount of the buffer memory 114 increases. As a result, the quantization step width W becomes smaller, and the resolution of the output image becomes higher.

After that, the quantization step width W is further reduced, and the control unit 131 reduces the data amount of the input image to 3
When it is determined that the rank is the second lowest, this control unit 131
Thus, this time, the address A1 for selecting the region R3 is output.

As a result, the number-of-lines conversion process is performed on the basis of the image data correction coefficient X, which has the third lowest high frequency component suppression degree. As a result, in this case, the high-frequency component of the image data to be encoded is not suppressed as compared with the case where the region R4 is selected, so that an image with a sharper contour is obtained than when the region R4 is selected.

Similarly, as the amount of data to be encoded decreases, the regions R2 and R1 are sequentially selected, and the high frequency components of the image data to be encoded are sequentially suppressed. As a result, the contour of the output image is sequentially emphasized.

According to this embodiment described in detail above, the following effects can be obtained. (1) First, according to this embodiment, the encoding operation unit 11
3, a means for outputting information indicating the amount of data to be encoded and a means for controlling the high frequency component of the image data to be encoded based on the output information of this means are provided, and when the amount of data to be encoded increases, Since the high frequency component is suppressed, it is possible to suppress an increase in the amount of data to be encoded. As a result, it is possible to suppress a decrease in the remaining storage amount of the buffer memory 114, and thus a decrease in the resolution of the output image can be suppressed.

(2) Further, according to this embodiment, as a means for outputting the information indicating the amount of data to be encoded, the remaining amount calculator 1 for outputting the data indicating the quantization step width W.
Since 15 is used, it is possible to output information indicating the amount of data to be encoded without separately providing a data amount output unit. As a result, it is possible to suppress an increase in hardware as much as possible by adding the high frequency component control device to the high efficiency encoding system.

(3) According to this embodiment, the high frequency component of the image data to be encoded is controlled by controlling the image data correction coefficient X for line conversion. Therefore, the high frequency component control means. Can be configured by utilizing the means for supplying the image data correction coefficient X. As a result, it is possible to suppress an increase in hardware as much as possible by adding the high frequency component control device to the high efficiency encoding system.

(4) Furthermore, according to this embodiment, since the amount of data to be encoded is determined in four stages, the high frequency component of the image data to be encoded can be controlled relatively finely. . As a result, the deterioration of the resolution of the output image can be suppressed relatively finely.

FIG. 2 is a block diagram showing the configuration of the second embodiment of the present invention. In the above embodiment, the case where the remaining amount calculation unit 115 that outputs the data indicating the quantization step width W is used as the means for outputting the information indicating the amount of data to be encoded has been described. In other words, in the previous example,
The case where the existing means is used as the data amount output means has been described. On the other hand, in this embodiment, the data amount output means is separately provided.

In FIG. 2, reference numeral 21 is a data amount evaluation unit as the data amount output means. The data amount evaluation unit evaluates the amount of image data to be encoded based on a predetermined data amount evaluation algorithm, and supplies the evaluation result to the coefficient control unit 13. As a result, the high frequency component of the image data to be encoded is controlled based on the evaluation result of the data amount evaluation unit 21.

Since there are various algorithms as the data amount evaluation algorithm, detailed description thereof will be omitted here.

According to this structure, since the data amount output means must be provided separately,
Although the amount of hardware increases, except for this point, the same effect as that of the previous embodiment can be obtained.

Although the two embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments. (1) For example, in the above-described embodiment, the case where the resolution of the output image is divided into four ranks for determination has been described. However, the present invention may be divided into smaller ranks or larger ranks for determination.

(2) In the above embodiment, the case where the high frequency component of the image data to be encoded is controlled by controlling the image data correction coefficient X for line conversion has been described. However, in the present invention, the contour of the input image may be controlled by controlling the image data correction coefficient other than this, and the high frequency component is controlled by a configuration other than the configuration of controlling the image data correction coefficient. You may do it.

(3) In the above embodiment, the case where the present invention is applied to the high-efficiency coding system for digital image communication has been described. However, the present invention can also be applied to high efficiency coding systems other than those for digital image communication.

(4) Further, in the above embodiment, the case where the present invention is applied to the image data encoding system has been described. However, the present invention can also be applied to, for example, an audio signal coding system.

(5) In addition to this, it is needless to say that the present invention can be variously modified without departing from the scope of the invention.

[0060]

According to the present invention described in detail above, there are provided means for outputting information indicating the amount of data to be encoded, and means for controlling the high frequency component of the data to be encoded based on this information, As the amount of data to be encoded increases,
Since the high-frequency component of the data to be encoded is suppressed, when applied to a high-efficiency encoding device for digital image communication, the resolution of the output image is reduced as the amount of data to be encoded increases. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

[Explanation of symbols]

 11 ... Encoding unit 12 ... Coefficient storage memory unit 13 ... Coefficient control unit 111 ... A / D conversion / YC separation unit 112 ... Line conversion unit 113 ... Encoding operation unit 114 ... Buffer memory 115 ... Remaining amount operation unit 21 ... Data amount evaluation unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H03M 3/04 0836-5K 7/38 0836-5K H04N 1/41 B G06F 15/68

Claims (3)

[Claims] 1. A data amount output means for outputting information indicating the amount of data encoded based on a differential encoding method, and an increase in the data amount indicated by the output information of the data amount output means, A high frequency component control device comprising: a high frequency component control means for controlling the high frequency component so that the high frequency component of the data is suppressed. 2. Modulating means for pulse-code modulating analog image data, line converting means for converting the number of lines of the modulated output of the modulating means into the number of lines in an intermediate format for image coding, and this line converting means. Encoding means for encoding the converted output of the encoding means based on the differential encoding method, temporary storage means for temporarily storing the encoded output of the encoding means, and based on the remaining storage capacity of the temporary storage means, In a coding system having a quantization step width calculation means for calculating a quantization step width of the modulation means, a data amount output means for outputting information indicating the amount of image data coded by the coding means, As the amount of data indicated by the data amount output means increases, the high frequency component of the image data encoded by the encoding means is suppressed so that High-frequency component control apparatus characterized by comprising a high-frequency component control means for controlling the frequency components. 3. The data amount output means is also used as the quantization step width calculation means, and outputs the quantization step width calculated by the quantization step width calculation means as information indicating the amount of the image data. The high-frequency component control unit is configured to control the high-frequency component by controlling an image data correction coefficient used in the line conversion processing of the line conversion unit. The high frequency component control device according to claim 2.