JP2542662B2 - Image signal communication method and image signal communication system - Google Patents

Description

The present invention relates to an image signal communication method and an image signal communication system, and an image signal for a video conference or the like in which a subject does not move much is transmitted with a relatively small transmission capacity regardless of a change in brightness of the subject. The image signal output from the camera with automatic aperture for the purpose of transmission and reception is divided by the aperture signal that changes depending on the aperture of the camera with automatic aperture, and inter-frame coding is performed, and then the coded image The above-mentioned aperture signal is multiplexed with a signal, encoded by an image signal encoding method to be transmitted to a transmission line, and an image signal encoded from the transmission line and an aperture signal of a camera with an automatic aperture that is multiplexed with the image signal are obtained. Receiving, separating the multiplexed image signal and aperture signal, interframe decoding only the image signal, multiplying the decoded image signal and aperture signal, and displaying on the display means. An image communication method for decoding by an output image signal decoding method.

[Industrial applications]

The present invention relates to an image signal communication method and an image signal communication system, and more particularly to an image signal communication method and an image communication system for transmitting a signal having a small difference value between two consecutive frames such as an image signal of a video conference.

An image signal of a video conference or the like has a small difference value between two consecutive frames because only a part of the image is changed. Therefore, when transmitting such a signal, the image signal is encoded by the well-known interframe encoding and transmitted as a signal of a small capacity.

However, in recent video conferences, cameras with an automatic diaphragm have been used in which the diaphragm automatically changes according to changes in the brightness of the subject. Therefore, an image communication system by interframe coding suitable for such a camera is desired.

[Conventional technology]

As a configuration example of a conventional image transmission system, FIG. 4 shows a configuration example of an image transmission system for a video conference.

In FIG. 4, the transmitter 17 has a camera 19 with an automatic aperture.
The image signal from is input to the interframe coding means 3.
In the inter-frame coding means 3, the difference value between two consecutive frames is sequentially coded, and further, for example, variable length coding is performed for signal compression and output to the transmission means 15. Transmission means 15
Then, the signal from the interframe coding means 3 is sent to the transmission line 5 after being formed into a predetermined frame.

The receiving device 18 receives, for example, a signal having a frame structure as described above from the transmission line 5 and inputs it to the receiving means.

In the receiving means, for example, the received frame signal is decomposed into frames and output to the interframe decoding means 7.
The interframe decoding means 7 performs, for example, variable-length decoding on the input signal, adds a difference value to the image signal of the preceding frame, that is, performs interframe decoding, and outputs it to the display means 9.

At this time, the aperture of the camera with automatic aperture 19 is determined by the brightness of a certain point in the image to be captured by the camera.

Therefore, the same subject is photographed at the same brightness and the same angle with a camera that does not have an automatic iris. , The difference value between two consecutive frames becomes large.

[Problems to be Solved by the Invention]

As described above, in the conventional configuration, since the aperture is determined by the brightness of a certain point in the image to be captured by the camera with an automatic aperture, when the brightness of a certain point in the image changes, Even though the brightness of the part does not change, the overall brightness changes, so that even the part of the image signal that originally does not change changes, and the image signal changes significantly.

In the well-known interframe coding means, the difference value between the previous frame and the current frame on one scanning line or in one division among them is calculated and output. Therefore, when there is no difference value, that is, when there is no motion between the previous frame and the current frame, a bit indicating that the difference value is 0 is transmitted by 1 bit, and the bit of the transmission signal to be transmitted is transmitted. Although the number of transmitted signals is reduced, the difference value increases because the image signal between two consecutive frames changes significantly due to the change in brightness due to the change in the aperture. Therefore, it becomes impossible to reduce the number of bits of the transmission signal to be transmitted as described above. Therefore, the number of bits of the transmission signal to be transmitted increases,
There is a problem that the capacity of the transmission path is exceeded and it becomes impossible to send all the image signals to the receiving device.

Therefore, it is an object of the present invention to transmit and receive an image signal of a video conference, etc., in which the movement of the subject is small, with a relatively small transmission capacity regardless of the change in the brightness of the subject.

[Means for Solving the Problems] FIG. 1 shows the principle of the present invention. The transmitter 13 outputs the image signal from the automatic aperture camera 1 and the aperture signal X indicating the aperture value automatically set by the camera to the dividing means 2. The dividing means 2 divides the image signal by the aperture signal and outputs it to the interframe coding means 3. The inter-frame encoding means 3 inter-frame encodes the divided image signal and outputs it to the transmitting means 4. The transmission means 4 multiplexes the coded image signal and the diaphragm signal and sends them to the transmission line 5.

In the receiving device 14, the receiving means 6 receives the image signal from the transmission path 5 and the aperture signal multiplexed with the image signal. The receiving means 6 separates the multiplexed image signal and aperture signal, outputs only the separated image signal to the interframe decoding means 7, and the interframe decoding means 7 decodes the image signal between frames. And outputs to the multiplication means 8. The multiplication means 8 multiplies the decoded image signal and the aperture signal and outputs the result to the display means 9.

[Action]

As described above, in the transmission device that transmits the signal from the camera with the automatic aperture, the difference value between two consecutive frames of the image signal is changed by changing the brightness of one point in the image whose brightness is detected. Will increase. However, the difference value between two consecutive frames caused by the change in brightness is removed by dividing the image signal by the aperture signal.
Therefore, the image signal input to the inter-frame encoding means becomes an image signal that does not include the inter-frame difference value caused by the change in brightness.

Therefore, the difference value between two consecutive frames encoded by the interframe encoding means is only the moving part of the object in the image.

Further, the transmitting means multiplexes the coded image signal and the aperture signal and transmits them.

Therefore, on the receiver side, the encoded image signal and the aperture signal multiplexed with the image signal are received, and the image signal and the aperture signal multiplexed in the receiving means are separated,
The inter-frame decoding means inter-frame decodes only the image signal, and the multiplying means multiplies the decoded image signal by the aperture signal.

Therefore, the same image signal as the image signal output from the camera with automatic aperture can be input to the display means.

〔Example〕

 A detailed description will be given below based on an embodiment shown in the drawings.

 FIG. 2 is a diagram of an embodiment of the present invention.

In FIG. 1, the dividing means 2 corresponds to the divider 21 of FIG. 2, and the interframe coding means 3 of FIG. 1 is the subtractor 31, quantizer 32, variable length coder 33 of FIG. Adder 34, frame memory 3
Corresponds to the part consisting of 5. The transmitting means 4 in FIG. 1 corresponds to the portion composed of the multiplexer 41, the frame mechanism 42 and the unipolar / bipolar converter 43 in FIG. The receiving means 6 in FIG. 1 corresponds to the portion composed of the bipolar / unipolar converter 63, the frame decomposer 62 and the separator 61 in FIG. The inter-frame decoding means 7 in FIG. 1 corresponds to the portion composed of the variable length encoder 72, the adder 71, and the frame memory 73 in FIG. The multiplication means 8 in FIG. 1 corresponds to the multiplier 8 in FIG.

In FIG. 2, the transmitter 13 has a camera 1 with an automatic aperture.
More specifically, an image signal as shown in FIG. 3 (b) and an aperture signal as shown in FIG. 3 (c), which indicates the size of the automatic aperture according to the brightness change of the image to be captured by the camera, are output. There is. The image signal is input to the image signal A / D converter 10, and the aperture signal is input to the aperture signal A / D converter 11, and A / D converted.

The A / D-converted image signal and aperture signal are input to the dividing means 2 and divided by the aperture signal in the divider 21. The divided image signal is the same as the signal from a camera without an aperture, but the aperture signal is removed as shown in FIG. 3 (a).
The signal is the same as the signal with the waveform as shown in A / D conversion.

At this time, the image signal and the diaphragm signal may be passed through the dividing means 2 before A / D conversion.

In the interframe coding means 3, the value of the previous frame stored in the frame memory 35 is subtracted from the value of the image signal input by the subtractor 31. The difference value output from the subtracter 31 is quantized by the quantizer 32 and output to the adder 34 and the variable length encoder 33. The adder 34 adds the difference value to the value of the previous frame stored in the frame memory 35 and inputs the difference value into the frame memory 35. Therefore, the value stored in the frame memory 35 is updated at any time. Variable length coding reduces the average number of bits per codeword by assigning a small number of bits to codewords that occur frequently and a large number of bits to codewords that occur infrequently. Is intended to be reduced. Therefore,
As an example of the operation performed by the variable-length encoder 33, if the input signal is divided into scanning lines or into some of the images, and there is no difference value for each division, the difference value is 0. 1 bit of the signal shown is sent. Therefore, when the difference value between two consecutive frames is small, the transmission code length can be reduced.

The transmission means 4 includes a variable length coded image signal and an A / D
The converted aperture signal is input. In the transmission means 4,
The image signal and the diaphragm signal are multiplexed by the multiplexer 41 and output to the frame configurator 42, and the frame configurator 42 incorporates a frame pattern into the multiplexed signal to form a frame. The framed signal is converted into a bipolar signal input to the unipolar / bipolar converter 43 and sent to the transmission line 5.

In the receiver 14, the image-framed image signal and the bipolar signal of the diaphragm signal are input to the receiver 6 from the transmission path 5. In the receiving means 6, first, the bipolar / unipolar converter 63 converts the image signal and the diaphragm signal into a unipolar signal and outputs the unipolar signal to the frame decomposer 62. The frame decomposing unit 62 removes the frame pattern from the unipolar signal and outputs only the multiplexed image signal and aperture signal to the separator 61. The separator 61 separates the image signal and the aperture signal, and outputs the image signal to the interframe decoding means 7 and the aperture signal to the multiplication means 8. In the inter-frame decoding means 7, the variable length decoder 72 performs variable length decoding and outputs it to the adder 71. The adder 71 adds the difference value between the image signal of the previous frame stored in the frame memory 73 and the image signal of the previous frame, and outputs it to the multiplication means 8 and the frame memory 73. . The value of the image signal stored in the frame memory 73 is updated. In the multiplication means 8, the image signal and the aperture signal are multiplied by the multiplier 81 and output to the D / A converter 12. D / A
The converter 12 converts the image signal into an analog signal as shown in FIG. 3 (d) and outputs it to the display means 9.

As described above, when the present invention is arranged, the image signal as shown in FIG. 3B is output from the camera with the automatic aperture. However, the aperture signal as shown in FIG. 3 (c) is superimposed on the image signal shown in FIG. 3 (b), and when the value of the aperture signal (c) fluctuates, the image signal ( b) varies. Due to fluctuations caused by superimposing the aperture signal (c), the difference value between frames increases and the signal cannot be effectively compressed. Therefore, in the transmitter, first, the aperture signal [FIG. 3 (c)] superimposed on the image signal is removed by the dividing means to obtain an image signal without signal fluctuation due to the aperture as shown in FIG. 3 (a). , Only the image signal is inter-frame coded. After that, the aperture signal is multiplexed with the inter-frame coded image signal and transmitted.

At the receiving side, first, the image signal and the aperture signal multiplexed with the image signal are separated. Thereafter, only the image signal shown in FIG. 3 (a) is inter-frame decoded, the aperture signal shown in FIG. 3 (c) is superimposed by the multiplying means, and the signal shown in FIG. 3 (d) is converted into the display means. It is outputting.

〔The invention's effect〕

As described above, according to the present invention, only the difference value of the fluctuation in the image is inter-frame coded, regardless of the increase of the difference value due to the change in brightness of the image signal.

Therefore, even if the difference value of the inter-frame code increases due to the change in brightness, the signal can be sufficiently compressed by the inter-frame coding to be transmitted and received.

[Brief description of drawings]

 FIG. 1 is a principle diagram of the present invention, FIG. 2 is a diagram of an embodiment of the present invention, FIG. 3 is a diagram of input / output waveforms of FIG. 2, and FIG. 4 is a configuration example of a conventional image communication system. In the figure and the figure shown, 1 ... Camera with automatic aperture, 2 ... Division means 3 ... Interframe coding means 4 ... Transmission means, 5 ... Transmission path 6 ... Reception means, 8 ... Multiplication means 7 ... Interframe decoding means 9 ... Display means 10 ... Image signal A / D converter 11 ... Aperture signal A / D converter 12 ... D / A converter, 13 ... Transmission device 14 ... Receiving device, 15 ...... Sending means 16 ...... Reception means, 17 ...... Camera with automatic aperture 21 ...... Divider, 31 …… Subtractor 32 …… Quantizer, 33 …… Variable length encoder 34 …… Adder, 35 ... Frame memory 41 ... Multiplexer, 42 ... Frame composer 43 ... Unipolar / bipolar converter 61 ... Separator, 62 ... Frame decomposer 63 ... Bipo La / unipolar converter 71 ...... adder, 72 ...... variable length decoder 73 ...... frame memory, 81 ...... multiplier

Claims (6)

(57) [Claims] 1. An image signal output from a camera with an automatic aperture is divided by an aperture signal that varies depending on the aperture of the camera with an automatic aperture, the divided image signal is interframe coded, and the interframe code is used. An image signal encoding method, wherein the aperture signal is multiplexed with the encoded image signal and the multiplexed signal is transmitted to a transmission line. 2. A coded image signal and a diaphragm signal of a camera with an automatic diaphragm multiplexed on the image signal are received from a transmission path, and the multiplexed image signal and diaphragm signal are separated. An image signal decoding method, characterized in that only the separated image signal is inter-frame decoded, and the inter-frame decoded image signal and the aperture signal are multiplied and output to a display means. 3. An image signal communication method, characterized in that the image signal is encoded by the encoding method according to claim 1, and the image signal sent to a transmission line is received and decoded by the decoding method according to claim 2. 4. An image signal from an automatic aperture-equipped camera (1) in which an aperture is automatically set according to a change in brightness of a copy and an aperture signal indicating the size of the aperture is output. And division means (2) for inputting the aperture signal and dividing the image signal by the aperture signal, and interframe encoding for interframe encoding and outputting the image signal obtained by dividing the image signal by the aperture signal. Means (3)
An image signal transmitting apparatus, comprising: and a transmitting means (4) for multiplexing the divided image signal and the aperture signal and transmitting the multiplexed signal to a transmission path (5). 5. An image signal coded from a transmission line (5), and an aperture signal indicating the size of an aperture automatically set by the change in lightness and darkness of a copy body, which is multiplexed on the image signal. A received signal (6) for receiving and receiving and separating and outputting the multiplexed image signal and aperture signal; and an interframe decoding means (7) for decoding and outputting the separated image signal. An image signal receiving apparatus, comprising: a multiplying unit (8) that multiplies the aperture signal and the inter-frame decoded image signal and outputs the result to a display unit (9). 6. An image communication system comprising the transmitting device (13) according to claim 4 and the receiving device (14) according to claim 5.