JPH01277078A - Still picture transmission method - Google Patents

Abstract

PURPOSE:To improve the picture quality of a transmitting/receiving image without increasing the number of image elements comprising one image by applying a smoothing filtering processing corresponding to a prescribed number of image data in the periphery of each image element at every image element before transmitting the image data. CONSTITUTION:When the image data corresponding to nine image elements (A-I) exist, a correction processing is applied on the image data of each image element fetched from a television camera 14 and stored in a picture memory 16 at every image element by a smoothing filter. In other words, for example, corrective computation either E=1/3(D+F+F), E=1/3(B+E+H), E=1/5(B+D+E +F+H), E=1/9(A+B+C+D+E+F+G+H+I) or E=1/9(A+B+C+D+2E+F+ G+H+I) is applied on the data E. In such a way, the image data of the image element E can be prevented from being a value different remarkably from that of each of the image elements (A-I) in the periphery of the image element E, and is smoothed to a harmonic value, and the picture quality of the transmission image can be improved without increasing the number of image elements comprising one picture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a still image transmission method, and particularly to a method for improving the image quality of transmitted images in a still image videophone.

[Prior Art] There is a demand for a videophone that simultaneously transmits audio and images using a telephone communication line, but in reality, current telephone communication lines cannot continuously transmit dynamic images that require a huge amount of data. Since it is difficult to send and receive a still image to the other party during a call, still image videophones are being put into practical use.

This still image videophone allows you to
It is possible to temporarily interrupt this call and send a desired still image, such as the speaker's face, a photo screen or a picture depending on the content of the call, or the like.

Therefore, with such a still image videophone, it is possible to send and receive images over a telephone line, which was previously impossible, and the amount of data processing is limited because only one still image is sent each time. This had the advantage that it was easy to put videophones into practical use.

A videophone capable of transmitting such still images is shown, for example, in the October 1986 issue of Foreign Communication Technology.

FIG. 2 is a circuit diagram of the simple still picture video telephone. In the figure, (1) is a handset, (2) is a microphone, (3) is an audio input/output circuit, (4) is an analog circuit, (5) is a matrix switch, (6) is a telephone interface circuit, and (7) is a is the telephone line connection terminal, (8) is the speaker, (9) is the keypad, (10) is the input/output board, (11) is the CPU, (12) is the program memory, (
13) is a modulation/demodulation circuit, (14) is a television camera, (15)
) is the image controller, (16) is the image memory, (
17) is a display.

Next, the operation of audio and image signal transmission of this conventional video telephone will be explained based on FIG. T:i2 and FIG.

In Figure 2, a voice call is made from a handset (1) or a microphone (2) to a telephone line via an audio input/output circuit (3), an analog circuit (4), a matrix switch (5), and a telephone interface circuit (6). Connection terminal (7)
will be sent to. Further, an audio signal from the other party is reproduced by the handset (1) or the speaker (8) via a path opposite to the above-mentioned signal path.

When transmitting an image signal, as shown in Figure 3, in order to confirm whether the communication partner is a video phone that has the ability to communicate image data in the same data format, an ID code such as data regarding the ability is sent. Sends the containing header. Then, after receiving the header back from the other party and confirming that the other party has similar capabilities, the image data is transmitted.

That is, in FIG. 2, when the keypad (9) is used to instruct image transmission, the CPU (11) detects this via the human output port (10), and the program memory (
12), the header is sent to the modulation/demodulation circuit (13) according to a program stored in advance. After modulating this header into an analog signal, it is sent out from the telephone line connection terminal (7) via the matrix switch (5). The header from the communication partner is sent to the CPU (
11) confirms the code etc.

Meanwhile, the image captured by the television camera (14) during this period is quantized by the image controller (15), stored in the image memory (16), and sequentially derived and displayed on the display (17). The image is output from the image memory (16) to the telephone line connection terminal (7).

When a header is input from the other party, the matrix switch (5) recognizes that image data reception is about to begin, and uses the carrier signal received by the matrix switch (5) to change the destination to the received signal from the telephone interface circuit (6). Switch from the analog circuit (4) to the modulation/demodulation circuit (13). After the received signal is demodulated by the modulation/demodulation circuit (13), the CPU (11) returns the header or stores the data in the image memory (16), and the image controller (15) sequentially converts the self-image data and the other party's image data. It is derived and displayed on the display (17). Further, a simple header containing an indicator that the image data starts is usually placed at the beginning of the image data.

Note that when the transmission and reception of images is completed and the carrier signal from the modulation/demodulation circuit (13) disappears, the matrix switch (5
) is the telephone interface circuit (6) and the analog circuit (4).
) to restore voice calls.

Furthermore, if the reply from the receiving side is to be omitted, information regarding the omission is included in the header, and the image data is transmitted following the header. In this case, the receiving side still prepares to receive the image data using this header.

[Problems to be Solved by the Invention] However, in such still image videophones, it is not possible to talk while images are being transmitted, so in order to maintain smooth communication, the image transmission time is limited. must be kept to a minimum.

For this reason, the reality is that the number of pixels constituting one screen is usually limited to a low number of pixels of about 64×64 or 96×96.

As a result, the quality of the transmitted image must be extremely low, and there is a problem in that it appears as an extremely rough and jittery image that cannot be used to identify the other party.

In particular, women who have a keen sense of aesthetics tend to dislike having their own facial expressions deformed in such a bold manner transmitted, and this is one of the factors that hinders the spread of still image videophones.

On the other hand, in order to improve the quality of the image, the conventional technology has no choice but to increase the number of pixels constituting the screen, which directly leads to an increase in the transmitted information E1iJn, time and cost.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a still image transmission method that can improve the quality of transmitted images without increasing the number of pixels constituting one screen. It's about doing.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides for each pixel of image data captured from a television camera and stored in an image memory, a predetermined number of pixels around each pixel. This method is characterized by performing smoothing filtering processing to correct image data according to the image data.

"Operation" Therefore, according to the present invention, when transmitting image data, instead of transmitting predetermined image data for each pixel as is, images of each pixel and other pixels around the pixel are transmitted. It will be transmitted after the data has been smoothed and corrected.

Therefore, since each pixel is sufficiently harmonized with each other, a smooth and clear image appears on the display screen, and an effective improvement in image quality can be achieved without increasing the number of pixels. Ru.

[Example] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

A feature of the present invention is that before transmitting the image data captured from the television camera to the other party's system, smoothing filtering processing is performed to obtain finer image quality before transmission.

This smoothing filtering process can be realized only by designing the software in the program memory (12) in the conventional device, and therefore there is no need to incorporate new device components, and it is not necessary to increase the size of the device in terms of hardware or manufacture it. It also does not cause an increase in costs.

FIG. 1 shows an explanatory diagram of the smoothing filtering process according to the method of the present invention.

Assume that there is image data corresponding to each of the nine pixels of A-1. As mentioned above, in the past, these image data were transmitted pixel by pixel as they were captured, so the image quality had to be proportional to the number of pixels fixed by the system. There wasn't.

For this purpose, in the present invention, the image data for each pixel captured by the television camera and written and stored in the image memory (16) for each pixel is supplemented by 1E according to a predetermined number of image data around the pixel. By doing so, each pixel is harmonized with each other, and irregularities in image data are suppressed to a smaller level.

Consider the case where data E in FIG. 1 is transmitted.

In this case, the smoothing filter set in the program memory (12) performs, for example, one of the following correction calculations.

(1) E-1/3 (D+E+F) (2) E-1/3 (B+E+H) (3) E-115 (B+D+E+F+H) (4) E-1
/9 (A+B10C101E+F+G+H+1) (5)E-1/9 (A+B+C+D+2E+F+G+
H+1) As a result, the image data of pixel E is prevented from taking a value that is significantly different from each pixel A-1 around the pixel E, and is kept at a value that harmonizes with the image data of each surrounding pixel. It can be understood that it is smoothed to

If such smoothing filtering processing is performed on all pixels of the image data, the displayed image can be displayed as a smooth, easy-to-read, clean image with fewer irregularities and rounded corners.

Further, as described above, since the number of pixels does not increase, the image transmission time does not change, making it possible to transmit still images quickly and at low cost.

Furthermore, especially when used by women, it has the advantage of being able to transmit a beautiful facial image that looks like it has been given soft focus.

Note that it is preferable that the smoothing filtering process be configured to be activated arbitrarily by the user by attaching a manual button or the like.

[Effects of the Invention] As explained above, according to the present invention, by performing smoothing filtering processing according to a predetermined number of image data around each pixel for each pixel before transmitting the image data,
Image quality can be improved without increasing the number of pixels, making it possible to transmit smooth and clear images.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of smoothing filtering processing according to the present invention, FIG. 2 is a block diagram of a conventional still picture video telephone device, and FIG. 3 is an explanatory diagram of the operation of the device according to FIG. 7.2. In the figure, (12) is a program memory, (14) is a television camera, and (16) is an image memory. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Patent Attorney Masuo Oiwa (2 others)
>tJ, Ming figure 1

Claims (1)

[Claims] A still image signal captured from a television camera is temporarily written and stored in the image memory as image data for each predetermined number of pixels, and this stored image data for each pixel is read out and sent to the other party's system via a telephone line. A still image transmission method, characterized in that the still image is transmitted after performing a smoothing filtering process to correct the image data for each pixel in the image memory according to a predetermined number of image data around the pixel. Transmission method.