JP3193078B2 - System environment adaptive contour compensation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a contour compensating how to perform image enhancement of edges for image quality improvement such as a television image, and more particularly to a system environment adaptive contour compensation how.

[0002]

2. Description of the Related Art Generally, the quality of a processed image is better if the details are sufficiently described and the edges are clearer. The former is determined by the resolution of the image processing system, and the latter is determined by the sharpness of the outline. In particular, the quality of a television image is greatly affected by the sharpness of the outline.

Although sharpness is a psychological concept, visual Mach phenomenon is performed by performing contour compensation for giving an appropriate amount of edge-enhanced distortion (contour compensation effect amount, enhancer effect amount) to a processed and reproduced image. And highlight the contrast phenomenon of brightness,
The sharpness of the contour portion can be obtained by improving the visually low contrast and the rising characteristics of the edge portion so as to make it easy to see.

FIG. 6 is a block diagram showing an image processing system to which a conventional contour compensation method is applied. In FIG. 6, reference numeral 1 denotes an image decoding unit for decoding an image signal (input signal) , and 2 denotes a video decoding unit. A contour compensator for enhancing the image edge portion of the decoded data obtained by the image decoder 1 in accordance with a constant contour compensation effect amount, and a decoding device 3 for emphasizing the edge portion of the image by the contour compensator 2. An image display unit (for example, a TV monitor) for displaying an image based on the digitized data.

[0005] With such a configuration, an image signal input via a transmission path or the like is decoded by an image decoding unit 1, and the decoded data is converted into a constant contour compensation effect amount by a contour compensation unit 2. After the image edge portion is emphasized, the image is displayed on the image display unit 3.

[0006]

However, in such a conventional contour compensation method, the enhancement of the image edge portion by the contour compensation section 2 is always performed with a constant contour compensation effect amount. When the system environment parameters (transmission rate, pixel thinning rate, quantization table, quantization gradation, moving image / still image, display size of the image display unit 3, etc.) change, it cannot respond well, and in such a case, There is a problem that image quality deteriorates. For example, if the contour compensation effect is large when the transmission rate is low, the quantization noise is emphasized and the image becomes difficult to see.

[0007] A high-efficiency coding method for moving picture signals, which is mainly intended for application to a video conference or a video phone, was recommended by CCITT in December 1990 (H.261).

Although the recommendation specifies the use of inter-frame / intra-frame adaptive prediction with motion compensation and DCT (discrete cosine transform), when the recommended transmission rate is low, the block by DCT is used. There was a problem that distortion was conspicuous.

When performing image coding, the amount of information generated on one screen greatly depends on the pattern, and the amount of information in an image that has little movement in time and has many flat portions is small, and small portions in which movement is intense and small are used. The amount of information of an image including many is large.

On the other hand, the line speed for transmitting the information is constant (for example, 64 kbps), and the amount of information that can be transmitted in one second is limited. For this reason, the block distortion is remarkably expressed as noise when an image with a sharp movement is input.

Further, in the case of performing image coding, if there is a function of switching input images of two or more channels or a function of switching the resolution of input images, the following problem occurs.

That is, for example, when the input channel is switched, there is no relation between the image contents before and after the switching (because the input image is discontinuous), so that a large amount of information clearly occurs. Would.

The same can be said for the case where there is a function for switching two or more resolutions. In these cases, much information is inevitably generated, and block distortion due to DCT becomes conspicuous.

[0014] The present invention has been made in view of such problems, so as to obtain the effect of the contour compensation in response to changes in the system environment, the system environment adaptive contour compensation how with improved image quality It is intended to provide.

FIG. 1A is a block diagram showing the principle of the present invention.
In FIG. 1, 1A is an image decoding unit that decodes an image signal (input signal) , and 2A is an image decoding unit obtained by the image decoding unit 1A, which emphasizes an image edge portion according to the contour compensation effect amount. A contour compensating unit 3 for performing the contour compensating unit 2
An image display unit for displaying an image based on the decoded data in which an edge portion of the image is emphasized in A, and a contour compensation effect amount control for controlling the contour compensation effect amount in the contour compensation unit 2A according to the system environment parameter. Department.

FIG. 1B is a block diagram showing the principle of another embodiment of the present invention. In FIG. 1B, reference numeral 1B denotes an image encoding unit, and the image encoding unit 1B includes a contour compensating unit 2A. Encodes the image signal from the imaging unit 5 in which the image edge portion is enhanced in accordance with the contour compensation effect amount, and outputs it as an output signal.
Is intended to force, in a manner similar to that shown in FIG. 1 (a),
The contour compensation effect amount in the contour compensation unit 2A is controlled by the contour compensation effect amount control unit 4 according to the system environment parameter.

[0017] Here, FIG. 1 (a), as the system environment parameters in the edge compensation effect amount control unit 4 of the present invention shown in (b), picture element decimation factor, the information amount of the input image, the input image not Continuity is used.

The image When using the element thinning rate, by increasing the contour compensation effect size as pixel thinning rate is lower emphasizing an edge portion of the image.

[0019]

Further, when the information amount of the input image is used, the contour compensation effect amount is increased as the information amount of the input image is smaller under a constant transmission rate, and the edge portion of the image is emphasized. Furthermore, when the discontinuity of the input image is used, when the discontinuity of the input image is detected, the contour compensation effect amount is reduced, and the enhancement of the edge portion of the image is weakened.

[0021]

According to the invention shown in FIG. 1A, the image signal input to the image decoding unit 1A is transmitted to the image decoding unit 1A.
, And the decoded data is displayed on the image display unit 3 after emphasizing the image edge portion by the contour compensation effect amount by the contour compensation unit 2A.

At this time, the amount of the contour compensation effect in the contour compensating section 2A is determined by the pixel as various system environment parameters.
It is adaptively controlled in accordance with the thinning rate, the information amount of the input image, and the discontinuity of the input image, and the effect of contour compensation corresponding to such a parameter and a change in the system environment can be obtained.

In the invention shown in FIG. 1 (b), after the image signal obtained by the image pickup unit 5 is emphasized by the contour compensation unit 2A with the contour compensation effect amount,
Output to the image encoding unit 1B.

At this time, the amount of the contour compensation effect in the contour compensating section 2A is determined by the pixel as various system environment parameters.
It is adaptively controlled in accordance with the thinning rate, the information amount of the input image, and the discontinuity of the input image, and the effect of contour compensation corresponding to such a parameter and a change in the system environment can be obtained. Then, the image signal in which the edge portion of the image is enhanced by the contour compensating unit 2A is encoded and output by the image encoding unit 1B.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(A) Description of First Embodiment FIG. 2 is a block diagram showing a first embodiment of the present invention. In FIG. 2, reference numeral 1 denotes an image decoding / encoding for decoding and encoding an image signal. The contouring unit 2A enhances an image edge portion according to the contour compensation effect amount with respect to the decoded data obtained by the image decoding / encoding unit 1 or the image data obtained by the TV camera (imaging unit) 5A. Compensation section.

Reference numeral 3A denotes a TV monitor (image display unit) for displaying an image based on the decoded data in which the edge portion of the image is emphasized by the contour compensating unit 2A, and 4 denotes a contour compensation effect amount by the contour compensating unit 2A. Is adaptively controlled according to system environment parameters (control information from the image decoding / encoding unit 1, display size information from the TV monitor A, control information from the TV camera 5A). is there.

Here, for example, the following (1) to (8) are used as system environment parameters used in the contour compensation effect amount control section 4. (1) Transmission rate (2) Pixel thinning rate (sub-sample; for example, QCIF with low resolution has a large thinning rate and CI with high resolution
(F is a thinning rate.) (3) A quantization table as a density when decoding / encoding in the image decoding / encoding unit 1 (density; information amount is low when coarse, and information amount is low when coarse) (4) Quantization gradation (A / D bit precision) (5) Moving image / still image (6) Display size of TV monitor 3A (7) Information amount of input image (movement of input image) (8) Discontinuity of input image (What happens when switching is performed when a function of switching input images of two or more channels or a function of switching the resolution of input images is provided)

For the parameters actually used as system environment parameters, the effect amount of contour compensation according to each parameter is determined in advance in, for example, several stages. Specifically, the contour compensation effect amount is set for each system environment parameter in accordance with the following trends (i) to (viii).

(I) In the case of the transmission rate, the contour compensation effect amount is increased as the transmission rate increases, and the edge portion of the image is emphasized.

(Ii) In the case of the pixel thinning rate, the lower the pixel thinning rate, the larger the contour compensation effect amount is, and the edge of the image is emphasized.

(Iii) In the case of a quantization table, the denser the quantization table is, the larger the contour compensation effect amount is, and the edge of the image is emphasized.

(Iv) In the case of the quantization gradation, the edge compensation portion is emphasized by increasing the contour compensation effect amount as the quantization gradation increases.

(V) When using a moving image or a still image, if the image is a still image, the edge compensation effect amount is increased, the edge portion of the image is emphasized, and if the image is a moving image, the outline is The compensation effect amount is reduced, and the enhancement of the edge portion of the image is weakened.

(Vi) In the case of the display size of the TV monitor 3A, the smaller the display size is, the larger the contour compensation effect amount is, and the edge portion of the image is emphasized.

(Vii) In the case of the information amount of the input image, based on the constant transmission rate (corresponding to each transmission rate of the image decoding / encoding unit 1), the contour compensation becomes smaller as the information amount of the input image becomes smaller. The effect amount is increased to emphasize the edge portion of the image.

(Viii) In the case of the discontinuity of the input image, when the discontinuity of the input image is detected, the edge compensation effect amount is minimized and the edge portion of the image is weakened as much as possible.

With the above-described configuration, when decoding, image decoding is performed.
Image signal received by the encoding / encoding unit 1(input signal)
Are decoded by the image decoding / encoding unit 1.
Thereafter, the decoded data is given a predetermined
Is the edge of the image emphasized by the contour compensation effect amount?
Are displayed on the TV monitor 3A.

At the time of encoding, the image signal obtained by the image pickup section 5 is emphasized by the contour compensating section 2A with a predetermined contour compensating effect amount, and then image decoding / encoding is performed. It is output to the unit 1 and is coded by the image decoding / coding unit 1 and output as an output signal .

At this time, in this embodiment, the contour compensating unit 2A
Is adaptively controlled by the contour compensation effect amount controller 4 as described in (i) to (viii) above in accordance with changes in the various system environment parameters described above.
The effect of the contour compensation corresponding to the change of the system environment can be obtained.

When the contour compensation effect amount is increased according to the tendency of the items (i) to (viii), the input signal as shown in FIG. As shown in (b), when the slope between the widths H is steep and the edge portion is emphasized, while the contour compensation effect amount is weakened according to the tendency of the items (i) to (viii). Figure 3
The input signal as shown in FIG. 3A is output from the contour compensator 2A as a signal having a gentle slope as shown in FIG. 3C.

That is, by adjusting the effect amount of the contour compensation, when the effect amount is small, the image is blurred, and as the effect amount is increased, the image becomes clearer.

The principle of such contour compensation is utilized, and furthermore, in the case of an intense motion due to human visual characteristics, the fact that the image is not so noticeable even if the image is blurred is utilized. In the case of the items (7) and (vii), the amount of information generated from the image decoding / encoding unit 1 or the TV camera 5A is monitored based on a constant transmission rate. By adaptively switching the contour compensation effect amount set in each step, block distortion noise due to DCT is reduced, and image quality is greatly improved.

As described above, according to the method of the present embodiment, the contour compensation effect amount in the contour compensation unit 2A is adaptively controlled by the contour compensation effect amount control unit 4 in accordance with various system environment parameters. The image quality can be significantly improved by effectively utilizing the effect of contour compensation corresponding to environmental changes.

In the above-described embodiment, the case where the method of the present invention is applied to both the case of decoding image data and the case of encoding image data has been described. The method of the invention may be applied.

(B) Description of the Second Embodiment Next, in particular, in the case of the above items (8) and (viii), that is, when the discontinuity of the input image is used as the system environment parameter, A configuration example will be described with reference to FIGS.

FIG. 4 is a block diagram showing a second embodiment of the present invention, and FIGS. 5A and 5B are block diagrams showing examples of a detection circuit for detecting discontinuity of an input image. is there. In the drawings, the same reference numerals as those described above indicate the same parts, and thus the description thereof will be omitted.

In FIG. 4, reference numerals 5-1 to 5-n denote TV cameras (imaging units) for obtaining image signals. In this embodiment, n cameras are provided so that n-channel image signals can be obtained. I have.

Reference numeral 6 denotes a channel / resolution switching operation unit for selecting and switching an image signal to be encoded from n-channel image signals and outputting a resolution switching instruction. Reference numeral 7 denotes a channel / resolution switching operation unit. A channel switching unit that selects and outputs any one of the image signals of the TV cameras 5-1 to 5-n according to an instruction.

Reference numeral 8 denotes a resolution switching unit for switching the resolution of the selected image signal in response to an instruction from the channel / resolution switching operation unit 7, and 9 denotes an image decoding / encoding unit 1.
This is a detection circuit for detecting the discontinuity of the input image to the input, that is, the switching operation by the channel switching unit 7 or the resolution switching unit 8.

FIG. 5A shows the detection circuit 9.
Alternatively, the one shown in FIG. 5B is used.

The detection circuit 9 shown in FIG. 5A is composed of two flip-flops (FF) 10 and 11 and an exclusive OR circuit (EOR) 12.

The flip-flops 10 and 11 perform a latch operation each time a frame pulse (using one vertical frame pulse output for each frame) is input. In addition to latching the switching signal (or the resolution switching signal), the flip-flop 11 latches the output from the flip-flop 10, that is, the channel switching signal (or the resolution switching signal).

The exclusive-OR circuit 12 performs an exclusive-OR operation on the output from the flip-flop 10 and the output from the flip-flop 11, so that when the previous signal is different from the current signal, That is, when a change occurs in the channel switching signal (or the resolution switching signal), the output is started up, and the fact that the discontinuity of the input image has occurred is output to the contour compensation effect amount control unit 4 as a switching detection signal. Things.

On the other hand, the detection circuit 9 shown in FIG. 5B includes two flip-flops 13 and 14 and an exclusive OR circuit 15 for detecting a change in the channel switching signal.
Two flip-flops 16 and 17 and an exclusive OR circuit 18 for detecting a change in the resolution switching signal;
An exclusive OR circuit (OR) 19 for ORing outputs from the exclusive OR circuits 15 and 18 is provided.

A circuit composed of the flip-flops 13 and 14 and the exclusive OR circuit 15 and the flip-flops 16 and
17 and the exclusive OR circuit 18 perform the same operation as the circuit described above with reference to FIG. 5A to detect a change in each signal (discontinuity of an image). Therefore, detailed description thereof is omitted.

When a change occurs in one or both of the channel switching signal and the resolution switching signal, the outputs of the exclusive OR circuits 15 and 18 rise, and the output of the OR circuit 19 rises accordingly. Is output to the contour compensation effect amount control unit 4 as a switching detection signal.

The contour compensation effect amount control unit 4 which has received the switching detection signal from the detection circuit 9 minimizes the contour compensation effect amount and weakens the edge portion of the image as much as possible.

As a result, noise caused by the generation of a large amount of information immediately after switching of the device having the channel switching function / resolution switching function can be reduced, and the image quality can be improved.

[0060]

As described above in detail, according to the system environment adaptive contour compensation how the present invention, a contour compensating effect amount,
Shi pixel thinning rate as the stem environmental parameter, input image
Information amount of the image, and then, it is adaptively controlled in accordance with the discontinuity of the input image, written on such parameters
The effect of contour compensation corresponding to the change of the system environment can be obtained, and the display image quality and the image quality of image data to be transmitted are greatly improved.

[Brief description of the drawings]

FIGS. 1A and 1B are block diagrams showing the principle of the present invention.

FIG. 2 is a block diagram showing a first embodiment of the present invention.

FIGS. 3A to 3C are diagrams showing examples of waveform changes according to the contour compensation effect amount.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIGS. 5A and 5B are block diagrams each showing an example of a detection circuit for detecting discontinuity of an input image.

FIG. 6 is a block diagram showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image decoding / encoding unit 1A image decoding unit 1B image encoding unit 2A contour compensation unit 3 image display unit 3A TV monitor (image display unit) 4 contour compensation effect amount control unit 5 imaging unit 5A, 5-1 to 1 5-n TV camera (imaging unit) 6 channel / resolution switching operation unit 7 channel switching unit 8 resolution switching unit 9 detection circuit 10, 11 flip-flop 12 exclusive OR circuit 13, 14 flip-flop 15 exclusive OR circuit 16 , 17 flip-flop 18 exclusive OR circuit 19 OR circuit

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuichi Terui 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Toshihiro Yamanaka 3--22-8 Hakata-ekimae, Hakata-ku, Fukuoka-shi, Fukuoka Fujitsu Inside Kyushu Digital Technology Co., Ltd. (72) Kenji Rikimaru 3-22-8 Hakata-ekimae, Hakata-ku, Fukuoka City, Fukuoka Prefecture Inside Fujitsu Kyushu Digital Technology Co., Ltd. 1015 Ueodanaka, Nakahara-ku Fujitsu Limited (56) Reference JP-A-61-96877 (JP, A) JP-A-1-31877 (JP, A) JP-A-61-251379 (JP, A) Hei 2-119470 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N ^5/ 14-5/217 H04N ^7/ 00-7/173

Claims (6)

(57) [Claims] 1. A decoded data obtained by decoding an image signal.
When displaying an image on the image display unit based on
Image data corresponding to the contour compensation effect amount
A contour compensation method for emphasizing an edge portion, wherein the contour compensation effect amount is controlled in accordance with a system environment parameter, and pixel thinning is performed as the system environment parameter.
Rate is used, and the lower the pixel thinning rate, the lower the contour compensation effect.
By increasing the fruit amount, characterized by emphasizing the edge portion of the image, the system environment adaptive contour compensation how. 2. A decoded data obtained by decoding an image signal.
When displaying an image on the image display unit based on
Image data corresponding to the contour compensation effect amount
A contour compensation method for emphasizing an edge portion, wherein the contour compensation effect amount is controlled in accordance with a system environment parameter.
At that time, as the system environment parameters, the input image
The amount of information is used, and the input image is
The smaller the amount of information, the greater the amount of contour compensation effect, and the
A system characterized by enhancing the edges of an image
Environment adaptive contour compensation method. 3. A decoded data obtained by decoding an image signal.
When displaying an image on the image display unit based on
Image data corresponding to the contour compensation effect amount
A contour compensation method for emphasizing an edge portion, wherein the contour compensation effect amount is controlled in accordance with a system environment parameter.
At that time, as the system environment parameters, the input image
A discontinuity is used to detect a discontinuity in the input image.
In this case, the contour compensation effect amount is reduced to reduce the edge of the image.
System environment characterized by weakening the emphasis
Adaptive contour compensation method. 4. An image signal obtained by an imaging unit is encoded.
When the image signal is
Contour compensation method that emphasizes
Thus, the contour compensation effect amount is controlled according to the system environment parameters.
At this time, pixel thinning is used as the system environment parameter.
Rate is used, and the lower the pixel thinning rate, the lower the contour compensation effect.
Increase the amount of fruit to emphasize the edges of the image
Characteristic, a system environment adaptive contour compensation method. 5. An image signal obtained by an imaging unit is encoded.
When the image signal is
Contour compensation method that emphasizes
Thus, the contour compensation effect amount is controlled according to the system environment parameters.
At that time, as the system environment parameters, the input image
The amount of information is used, and the input image is
The smaller the amount of information, the greater the amount of contour compensation effect, and the
A system characterized by enhancing the edges of an image
Environment adaptive contour compensation method. 6. An image signal obtained by an imaging unit is encoded.
When the image signal is
Contour compensation method that emphasizes
Thus, the contour compensation effect amount is controlled according to the system environment parameters.
At that time, as the system environment parameters, the input image
A discontinuity is used to detect a discontinuity in the input image.
In this case, the contour compensation effect amount is reduced to reduce the edge of the image.
System environment characterized by weakening emphasis
Adaptive contour compensation method.