JPH02140083A - Picture transmission system - Google Patents

Abstract

PURPOSE:To reduce the picture switching time by sending a difference between a preceding and a present picture data at the sender side, correcting part of the preceding picture data with the sent difference data at the receiver side, and generating the present picture data. CONSTITUTION:A picture data written in a frame memory 5 and a picture data written in a frame memory 6 at present are compared by a comparator section 7 in the unit of picture elements. When only part of the pattern is changed, picture elements of both the memories 5, 6 are read again and compared at the comparator section 7 and a switch 8 is thrown to a moving contact 8b every time the picture elements of the memories 5, 6 differ from each other and the address data is sequentially written in a buffer memory 9. When the comparison processing is finished, the content of the memory 9 is read, sent to the receiver side B and written in the frame memory 16. The preceding picture data is written in the memory 15 and the control circuit 16 processes the address data to rewrite only part of the data subjected to change. This is new picture information and reproduced on a monitor 18 or a printer 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image transmission system that allows image data to be transmitted using a transmission system with a small capacity.

[Conventional technology]

For example, when looking at an NTSC screen, the amount of image data ranges from a few Mbits to several tens of Mbits per screen, and it takes a long time to transmit even a still image over a normal telephone line. It becomes necessary.

[Problem to be solved by the invention]

Therefore, conventionally, for example, in a still image videophone system, it is necessary to interrupt the call for several seconds to ten-odd seconds each time the screen is switched, which is inconvenient.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image transmission method that can reduce the time required for switching images as much as possible by transmitting only differences in subsequent image data.

[Means to solve the problem]

To this end, the present invention provides a transmitting side that transmits data for the difference between the previous image data stored in a first memory and the current image data; It is configured to have a receiving side that corrects a part of the contents of the second memory using the transmitted difference data and creates the current image data.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing one embodiment thereof. A indicates the sending side, B indicates the receiving side, and they are connected by a telephone line C.

First, on the transmitting side, an image captured by a camera 1 can be checked on a monitor 2, and one frame of the image is transferred to a frame memory 5. 6 are written alternately. 7 is a comparison unit that compares the contents written in both frame memories 5.6 pixel by pixel, 8 is a switch for reading out all or part of the data from one of both frame memories 5.6, and 9 is the read pixel data. This is a buffer memory that temporarily stores the address data in the frame memory 5 or 6 together with the address data. The operations from the switch 4 to the buffer memory 9 are controlled by a control circuit 10. Reference numeral 11 is a modem, and reference numeral 12 is a line control device having an automatic transmission/reception function.

Further, on the receiving side B, a line control device 13 similar to the above line control device 12, a modem 14, a frame memory 1
5, a control circuit 16 that controls the address of the frame memory 15, a D/A converter 17, a monitor 18, a printer 1;
Equipped with 9th grade.

Now, assume that line control devices 12 and 13 are connected via telephone line C. In this state, the image information captured by the camera 1 is digitized by the A/D converter 3 and written to the frame memory 5 if the switch 4 is switched to the contact 4a side. Then, by switching the switch 8 to the contact 8a side and reading out the written image data, the written image data passes through the buffer memory 9 as it is (through the path indicated by -), and is transferred to the modem 11 and the line control device 12.
from the telephone line C to the line control device 1 on the receiving side B.
3 to the modem I4 and written to the frame memory 15. By reading out the image data written in the frame memory 15, the monitor 18
The image is displayed as a still image and printed out on paper by the printer 19.

In this way, when the first image is transmitted after receiving side B is connected to the sending side, all data of that image is transferred to sending side A.
The frames are synchronized with the receiving side B, and are sequentially transmitted from the frame memory 5 of the sending side A to the frame memory 15 of the receiving side B, and one screen's worth is created on the receiving side.

When transmitting the next screen, the switch 4 on the transmitting side A is switched to the contact 4b side, and the captured image data of the camera 1 is written into the frame memory 6.

The new image data written in the frame memory 6 and the previous image data already written in the frame memory 5 are compared at high speed in the comparison section 7 pixel by pixel.

As a result of this comparison, if the new pixel portion of the new image data exceeds a predetermined percentage of the entire screen, the contact point of the switch 8 is switched to the 8b side, and all new image data in the frame memory 6 is is read out and transmitted to receiving side B in the same manner as above. As a result, the contents of the frame memory 15 on the receiving side B are all updated to the new contents existing in the frame memory 6.

As a result of the above comparison, if the new pixel portion of the new image data does not exceed a predetermined percentage of the whole, that is, if only a part of the screen has changed, the pixels in frame memories 5 and 6 are read out again. The comparing section 7 compares the data of the pixel in the frame memory 6 that is different from the pixel in the frame memory 5, and the address data of the pixel is taken out from the contact 8b of the switch 8.
The movable contact switches to the contact 8b side, and the pixel data and address data are sequentially written into the buffer memory 9.

After the comparator 7 completes the comparison process for all pixels, the contents of the buffer memory 9 are read out and transmitted to the receiving side B via the modem 11 and line control device 12 in the same manner as described above. Modem 14 to frame memory 1
Write in 5. At this time, the previous image data (pixel data of the frame memory 5) has been written in the frame memory 15, but the address data is processed by the control circuit 16 to control the frame memory 15, and the pixel portion that has changed is Only that data will be rewritten. The data in the frame memory 15 that has been partially rewritten in this way becomes data that matches the image data written in the frame memory 6 on the sending side, that is, new image information, and is reproduced on the monitor 18 or printer 19. be done.

In this way, if the difference between the still image data sent last time and the still image data sent this time remains within a predetermined percentage, only the current data of the difference will be sent. Compared to the case of transmission, the transmission time is extremely short, and the speed can be increased.

Note that although the above example is given as an example of one-way communication, it is of course possible to apply the present invention to two-way communication.

In this case, it is possible to install a transmitting section A and a receiving section B that share a modem and a line control device on one side, or to share one of the two frame memories on the transmitting side with frame memos on the receiving side. .

Further, in the buffer memory 11, all the different pixel data and their address data for one frame are stored and then read out and transmitted all at once, but it is also possible to process them field by field. Alternatively, frame memory 5.6.15 can be used as a line memory to compare pixels between adjacent scanning lines and transmit only the different portions of pixels, and furthermore, to compare adjacent pixels in the same scanning line to transmit pixels. It is also possible to transmit only the different parts.

〔Effect of the invention〕

As explained above, according to the present invention, only the image data related to the different parts are transmitted, so the amount of data to be transmitted can be reduced compared to a method in which all image data is transmitted each time. Even when applied to a still image videophone system, it is possible to reduce the call interruption time when changing the screen.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention. Agent: Patent attorney Tsuneaki Nagao

Claims (3)

[Claims] (1) A transmitting side that transmits the difference data between the previous image data stored in the first memory and the current image data; and a receiving side that corrects a part of the contents of the second memory using the difference data to create current image data. (2) The above difference data is the difference for each pixel between fields or frames, the difference for each pixel between adjacent scanning lines, or the difference for each adjacent pixel within the same scanning line. An image transmission system according to claim 1, characterized in that: (3) If the difference between the image data of the previous field or frame and the image data of the current field or frame does not exceed a predetermined percentage of the field or frame, the difference between the image data of the current field or frame is calculated. 3. The image transmission method according to claim 2, wherein the image transmission method comprises: transmitting an image;