JPH11177966A - Image-multiplexed transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to simultaneously transmit an image indicating the whole state and an image indicating a detailed state by additionally multiplexing a picture signal obtained from an enlargement camera and transmitting the multiplexed data upon occurrence of abnormality. SOLUTION: Digitized image data from a wide angle camera 15a are compressed to a specified band suited to multiplex transmission by a wide angle image encoder 16a and are combined with image signals from other position, so that four channels are multiplexed by an image MUX 18 and the multiplexed data are transmitted to a center system through a system MUX 22. When a sensor 3a detects an abnormality, a control signal is sent from the center system to a system controller 23, while a terminal system executes processings for abnormality occurrence. Namely an enlargement camera 17a is driven in order to obtain an enlarged image of a position where the abnormality has occurred. Then, picture data from the camera 17a are selected by a switch 19 and compressed to a specified band suited to multiplex transmission by an enlarged image encoder 20 and the compressed data is switched by a switch 21 and transmitted to the center system through the system MUX 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image multiplex transmission system, and more particularly, to an image multiplex transmission system in a system for performing remote monitoring using images.

[0002]

2. Description of the Related Art A system for monitoring a building or the like by installing a plurality of surveillance cameras and sensors for infrared rays, fire, smoke, etc., and performing centralized monitoring from a remote place is often used. These systems generally employ digital transmission for reasons such as high quality transmission requirements and digital signal processing of images. In addition, since image data becomes a signal having an extremely wide band when digitized, it is usually necessary to use an image compression coding technique. 7 and 8 are block diagrams of a conventional image multiplexing transmission system. FIG. 7 shows a terminal system, and FIG. 8 shows a center system. This image multiplexing transmission method is based on cameras 1a, 1b, 1c, 1d, encoders 2a, 2b, 2c, 2d and sensors 3a, 3b, 3d, which are installed at respective monitoring points A, B, C, D.
c, 3d, an image MUX4 for multiplexing output signals of the encoders, a sensor MUX5 for multiplexing output signals of the sensors, and an output signal of the image MUX4 and an output signal of the sensor MUX5 are multiplexed and transmitted. A terminal system including a system MUX 6 for outputting to a line, a system controller 7 for controlling a camera, a system DMUX 8 for separating an image signal and a sensor signal from a multiplexed signal received from a receiving line, and a multiplexed image An image DMUX 9 for separating each image signal from a signal, and a decoder 10a, 10b, 10c, 1 for decoding each separated image signal
0d, a display controller 11, and a sensor DM for separating each sensor data from the multiplexed sensor signal.
UX 12 and display 13 for displaying images and alarms
And a center system including a system controller 14 for controlling the camera.

[0003] The image multiplex transmission system configured as described above operates as follows. In this figure, the monitoring points are A, B, C, D
The following four cases are shown, but the description will be made using the monitoring point A as an example. First, the terminal system will be described. Digitized image data from a camera 1a for photographing a monitored area is compressed by an encoder 2a into a predetermined band suitable for multiplex transmission, and is combined with image signals of other places in four channels. Are multiplexed by the image MUX4. On the other hand, the sensor 3a attached to the monitoring location and having the function of detecting abnormality such as infrared rays, fire, smoke, etc., multiplexes four channels with the sensor MUX5 together with the sensor data of other locations. Next, in order to transmit the multiplexed image signal and sensor signal to the center system via the transmission line, the multiplexed signal is converted into a multiplexed signal having a frame structure suitable for transmission on the digital transmission line by the system MUX6 and output. Further, the system controller 7 receives the control signal of the camera 1a from the center system, adjusts the photographing angle of the camera 1a and zooms up according to a command from the center system when an abnormality occurs in the monitoring location, and enlarges the abnormal location. Is controlled to obtain

Next, a center system will be described. A multiplexed signal received from a receiving line is separated into a multiplexed signal of an image signal and a multiplexed signal of a sensor signal by a system DMUX8. The multiplexed signal of the separated image signal is
It is input to the image DMUX 9 and separated into the original four-channel image signals. The separated image signal of the monitoring point A is input to the decoder 10a, decoded into image data before compression, and then output to the display controller 11. On the other hand, the multiplexed signal of the separated sensor signals is input to the sensor DMUX 12, separated into the original four-channel sensor data, and output to the display controller 11. The display controller 11 controls the display 13 to perform image display and alarm display of the surveillance camera as predetermined.
Also, when an abnormality occurs in the monitoring location, the system controller 14 operates the camera 1 of the terminal system according to an external operation signal.
A signal for adjusting the photographing angle a and performing zoom-up is sent to the terminal system.

[0005]

However, in the conventional image multiplexing transmission method as described above, when a monitor image of an abnormal portion is zoomed up to an enlarged image when an error occurs, the screen becomes a part of the monitor target range. However, there is a problem that it is difficult to monitor the entire image, and it is difficult to detect a subsequent abnormality. The present invention
Image multiplexing transmission for solving the problem of the conventional image multiplexing transmission system as described above, which efficiently and simultaneously transmits a wide-angle image showing an overall situation and an enlarged image showing a detailed situation. The aim is to provide a scheme.

[0006]

In order to achieve the above object, according to the present invention, in a system in which a plurality of cameras and a plurality of abnormality detection sensors are installed at monitoring locations and a remote monitoring is performed by using an image, a wide-angle camera is normally used. Remote monitoring by multiplexing and transmitting the image signal and the sensor output signal according to the above. In the event of an abnormality, the remote monitoring is performed by additionally multiplexing and transmitting the image signal of the magnifying camera. During transmission of image signals, the transmission bit rate of image signals by other wide-angle cameras is reduced to keep the overall multiplexed transmission speed constant,
Furthermore, when an image signal is transmitted by a magnifying camera, upsampling and a difference operation are performed using the image signal of the corresponding wide-angle camera, and high efficiency coding is performed by transmitting the obtained difference image. And

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. 1 and 2 are block diagrams showing an embodiment of an image multiplexing transmission system according to the present invention. FIG. 1 shows a terminal system, and FIG. 2 shows a center system. As shown in FIG. 1, the terminal system in the image multiplexing transmission system according to the present invention includes wide-angle cameras 15a, 15b, 15c, and 15d installed at monitoring points A, B, C, and D.
And wide-angle image encoders 16a, 16b, 16c, 16d
A magnifying camera 17a, 17b, 17c, 17d and sensors 3a, 3b, 3c, 3d, an image MUX 18 for multiplexing output signals of the wide-angle image encoders, and a switch 19 for selecting an output signal from the magnifying camera. , An enlarged image encoder 20, a switch 21, a sensor MUX5 for multiplexing output signals of the respective sensors, and a wide angle image multiplexed signal, an enlarged image signal and a sensor multiplexed signal which are inputted and multiplexed to a transmission line. An output system MUX22,
A system controller 23 for controlling a magnified camera and band compression of image data. On the other hand, the center system in the image multiplex transmission system according to the present invention is shown in FIG.
As shown in FIG. 2, a system DMUX 24 for separating the wide-angle image multiplexed signal, the enlarged image signal and the sensor multiplexed signal from the multiplexed signal received from the receiving line, and separates each image signal from the multiplexed wide-angle image signal. Image DMUX
25, wide-angle image decoders 26a, 26b, 26c, 26d for decoding the separated image signals, an enlarged image decoder 27 for decoding the enlarged image signal, and a sensor for separating the data of each sensor from the multiplexed sensor signal D
The MUX 12 includes a display 28 that displays wide-angle image data, enlarged image data, and sensor data, and a display system controller 29 that controls the display 28 and performs processing when an alarm occurs.

The image multiplexing transmission system configured as described above operates as follows. In this figure, the monitoring points are A, B, C,
The case of four locations D is shown, but the monitoring location A will be described as an example. First, the terminal system will be described. Digitized image data from a wide-angle camera 15a for photographing a monitored area is compressed by a wide-angle image encoder 16a into a predetermined band suitable for multiplex transmission, and combined with image signals at other locations. 4 is multiplexed by the image MUX 18 and transmitted to the center system via the system MUX 22. At this time, when the sensor 3a detects an abnormality and sends an alarm to the center system via the sensor MUX5 and the system MUX22, a control signal is sent from the center system to the system controller 23 through a receiving line, and the terminal system uses Under the control of the system controller 23, processing when an abnormality occurs is performed. Therefore, the magnifying camera 17a is operated to obtain an enlarged image of the location where the abnormality has occurred. After the image data of the magnified camera 17a is selected by the switch 19, the image data is compressed to a predetermined band suitable for multiplex transmission by the magnified image encoder 20, and transmitted to the center system via the system MUX by the switch 21. . On the other hand, in order to keep the transmission bit rate on the transmission line constant in normal times and when an abnormality occurs, the bit rate assigned to the wide-angle image when the enlarged image signal is multiplexed is reduced. The bit rate assigned to the image transmission is 4R, and the four monitoring points A, B, C, D
A bit rate of R is assigned to a wide-angle image at each location, and an enlarged image is not transmitted. Here, it is assumed that an abnormality has occurred in the monitoring location A, and a request for transmission of an enlarged image has been made from the center system. At this point, it is considered that the observer is paying the most attention to the enlarged image of the monitoring location A, so R is preferentially assigned as the bit rate. Therefore, the bit rate assigned to the wide-angle image is 4R-R = 3R, and 3R / 4 = 0.75R is assigned to one wide-angle image. Therefore, when an abnormality occurs, the transmission bit rate of the wide-angle image encoder 16a becomes 3/4 of the normal state under the control of the system controller 23.

Next, a center system will be described. A multiplexed signal received from a receiving line is transmitted to a system DMUX24.
To separate a multiplexed signal of a wide-angle image signal and a multiplexed signal of an enlarged image signal and a sensor signal. Further, the separated multiplexed wide-angle image signal is input to the image DMUX 25 and separated into the original four-channel wide-angle image signal. The wide-angle image signal of the separated monitoring point A is output to the wide-angle image decoder 26a.
And decodes it into image data before compression, and outputs it to the display system controller 29. The transmission bit rate received by the wide-angle image decoder 26a differs between the normal state of the monitoring location and the time of occurrence of an abnormality, and is controlled by the display system controller 29. The enlarged image signal of the separated monitoring location A is input to the enlarged image decoder 27, decoded into image data before compression, and output to the display system controller 29. Note that the enlarged image signal is received only when the terminal system is controlled by the display system controller 29, such as when an abnormality occurs in a monitoring location. On the other hand, the multiplexed signal of the separated sensor signals is input to the sensor DMUX 12, separated into the original four-channel sensor data, and output to the display system controller 29. The display 28 performs image display and alarm display of the monitoring camera under the control of the display system controller 29.

FIG. 3 shows a configuration of an encoder and a decoder used in the present embodiment. (A) is a configuration diagram of an encoder, which includes a discrete cosine transform (hereinafter, referred to as DCT) unit 30, a quantization unit 31, a quantization table unit 32, an entropy encoding unit 33, and an encoding table unit 34. ,
A buffer unit 35 and an encoding control unit 36 are provided. Image data, which is a digital signal, is subjected to orthogonal transform by a DCT unit 30 to a pixel block in which a plurality of pixels are put together, and is converted to a frequency domain. Since the transformed DCT coefficients include visually insignificant components such as high-frequency components, the quantization unit 31 coarsely quantizes or discards the DCT coefficients of the high-frequency components to reduce signal redundancy. The quantization section 31 is performed based on the quantization table section 32. Next, the quantized image data is output to the entropy encoder 33.
To compress information. The entropy coding unit 33 uses unequal length codes, and assigns a short code to an output level with a high frequency of occurrence and a long code to a level with a low frequency of frequency, thereby shortening the average code length of the code output. . (The entropy coding unit 33 performs information compression with reference to the coding table unit 34.) By performing entropy coding, the bit rate of coded data is not constant. Therefore, the encoded data is accumulated in the buffer unit 35, and the bit rate is smoothed and output. The encoding control unit 36 determines the quantization accuracy based on the occupancy of the buffer unit 35, and keeps the transmission bit rate constant. If the transmission path allows a variable transmission bit rate, the encoding control unit 36 is not always necessary.

FIG. 2B is a block diagram of the decoder, which comprises an entropy decoding unit 37, a decoding table unit 38, an inverse quantization unit 39, an inverse quantization table unit 40, and an inverse DCT unit 41. . The transmitted encoded data is decoded into DCT coefficients quantized by the entropy decoding unit 37 and the decoding table unit 38. Subsequently, the inverse quantization unit 3
9 and the inverse quantization table unit 40 to perform decoding for removing redundancy, and finally, the inverse DCT unit 41 performs inverse transform of DCT and decodes. Note that the present encoding algorithm is an example, and the transmission method according to the present invention can be realized even if another method is adopted.

FIGS. 4A, 4B and 5 show an embodiment in which an encoder and a decoder for an enlarged image are more efficiently coded. The embodiment describes only a part related to the image transmission, FIG. 4A shows an encoder in the terminal system, and FIG. 4B is a detailed view of the enlarged image encoder. FIG. 5 shows a decoder in the center system. As shown in FIGS. 4A and 4B, the terminal system
Wide-angle camera 15 installed at each monitoring point of A, B, C, D
a, 15b, 15c15d and wide-angle image encoder 16
a, 16b, 16c, 16d and magnifying cameras 17a, 1
7b, 17c, 17d, an image MUX 18 for multiplexing the output signals of the wide-angle image encoders, a switch 19 for selecting an output signal from the magnifying camera, and a switch for selecting the output signals of the wide-angle image encoders 42, a wide-angle image decoder 43 functioning as an enlarged image encoder, an image cutout unit 44, an up-sampling unit 45, a subtractor 46, a difference encoder 47, and the wide-angle image multiplexed signal and the enlarged image signal. The system includes a system MUX 22 that outputs to a transmission line, and a system controller 48 that controls encoding of a magnified camera and image data. On the other hand, as shown in FIG. 5, the center system includes a system DMUX 24 for separating the wide-angle image multiplexed signal and the enlarged image signal from the multiplexed signal received from the receiving line, and each image signal from the multiplexed wide-angle image signal. DMUX 25 for separating the image signals, wide-angle image decoders 26a, 26b, 26c and 26d for decoding the separated image signals, and a switch 49 for selecting the output signal of each of the wide-angle image decoders
And an image cut-out unit 44 functioning as an enlarged image signal decoder, an up-sampling unit 45, a difference decoder 50, an adder 51, and a display system controller 52 for controlling a display and performing processing when an alarm is generated.

The image multiplex transmission system configured as described above operates as follows. In this figure, the monitoring points are A, B, C, D
The following four cases are shown, but the description will be made using the monitoring point A as an example. 1 and 2 for transmission of wide-angle images.
Since this is the same as that described above, transmission of an enlarged image will be described here. The enlarged image has a high correlation with the part that overlaps with the field of view of the wide-angle image at the same point. It will be a similar image. Therefore, the enlarged image Iz taken by the magnifying camera
And the difference Iz-Iw for each pixel between the image and the image Iw obtained by enlarging the portion of the wide-angle image is mostly small.
If only this value is transmitted instead of the enlarged image, the transmission coding efficiency is improved. To explain this with reference to an actual configuration diagram, in the terminal system, a wide-angle image at a desired monitoring location is selected by the switch 42, and the output wide-angle image encoded signal is decoded by the wide-angle image decoder 43. The image cutout unit 44 sets coordinates from the decoded wide-angle image under the control of the system controller 48, and cuts out an image in the same range as the enlarged image. The extracted image is displayed in the up-sampling unit 45.
Stretch by. Next, the enlarged image of the desired monitoring location is selected by the switch 19, and the value of each corresponding pixel of the enlarged image is subtracted by the subtractor 46 from the value of each pixel of the output enlarged image. The difference encoder 47 compresses and encodes the difference image obtained by the subtraction, and the system MUX 22
Output to In the center system, a wide-angle image of a desired monitoring location is selected by the switch 49 and output to the image cutout unit 44. The image cropping unit 44 sets coordinates from the wide-angle image under the control of the system controller 52, and crops an image in the same range as the enlarged image. The cut-out image is stretched by the up-sampling unit 45. Next, the difference screen transmitted is decoded by the difference decoder 50, and the expanded screen and the difference decoded screen are added by the adder 51 to obtain the original enlarged screen.

FIG. 6 shows a processing procedure for upsampling. In the present example, upsampling is doubled, and {1/2, 1, 1/2} is used as a filter coefficient of the upsampling filter. In the figure, filtering is performed by inserting a pixel having a value of zero in the horizontal direction with respect to the (4 × 4) original image.
The filtering is represented by the following equation, where x (n) is the original image and y (n) is the filtered image. y (2n) = x (n), y (2n + 1) = x (n) /
2 + x (n + 1) / 2 The meaning of this expression is that the value after filtering uses the value of the original image as it is in the case of an even number term, and adds and halves the values on both sides in the case of an odd number term That is to use. Next, rows and columns are exchanged with respect to the filtered image, and zero pixels are further inserted to obtain an (8 × 8) image. Subsequently, by performing filtering and exchanging rows and columns for the filtered image, an image in which the original image is doubled can be generated.

As for the transmission bit rate, assuming that the entire bit rate is 4R, R is assigned to the difference image and 0.75R is assigned to the four wide-angle images. The enlarged image is the difference image and 1
Since this is the sum of the two wide-angle images, the bit rate assigned to the enlarged image is R + 0.75R = 1.75R, and high-quality transmission can be performed. Also, among the wide-angle images, an image showing the same screen as the enlarged image has an abnormality,
Since it is used for difference calculation in encoding of an enlarged image, it is desirable that the image quality be higher than that of other wide-angle images. Therefore, assuming that the bit rate of a wide-angle image indicating occurrence of abnormality is R, the bit rate of the enlarged image is R +
R = 2R, and the bit rates of the other wide-angle images are 2R / 3, respectively. Although the present invention has been described with reference to the case where the number of monitoring points is four, the present invention is not limited to this, and any number of monitoring points can be used.

[0016]

As described above, the present invention makes it possible to simultaneously multiplex a wide-angle image showing the entire situation being constantly transmitted and an enlarged image showing the detailed situation transmitted when necessary, and to multiplex-transmit the enlarged image. Nevertheless, the overall transmission speed can be kept constant, and high-quality transmission of necessary screens can be performed, which is very effective in performing image multiplexing transmission.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a terminal system using an image multiplexing transmission system according to the present invention.

FIG. 2 is a configuration diagram showing one embodiment of a center system using an image multiplexing transmission system according to the present invention.

FIGS. 3A and 3B are diagrams illustrating configuration examples of an image encoder and an image decoder.

4A is a diagram showing an embodiment of a terminal system using the image multiplexing transmission system according to the present invention, and FIG. 4B is a diagram showing details of an enlarged image encoder;

FIG. 5 is a configuration diagram showing one embodiment of a center system using the image multiplexing transmission method according to the present invention.

FIG. 6 is a conceptual diagram showing upsampling of an image.

FIG. 7 is a diagram showing a configuration example of a conventional image multiplexing transmission system.

FIG. 8 is a diagram showing a configuration example of a conventional image multiplexing transmission system.

[Explanation of symbols]

1a, 1b, 1c, 1d, camera, 2a, 2b, 2
c, 2d-encoder, 3a, 3b, 3c, 3d-
・ Sensor, 4 ・ ・ Image MUX, 5 ・ ・ Sensor MU
X, 6. System MUX, 7 System controller, 8 System DMUX, 9 Image DM
UX, 10a, 10b, 10c, 10d-decoder, 11-display controller, 12-
Sensor DMUX, 13. Display, 14. System controller, 15a, 15b, 15c, 15
d ·· Wide-angle camera, 16a, 16b, 16c, 16d
..Wide-angle image encoders, 17a, 17b, 17c,
17d ... magnifying camera, 18. image MUX, 19
..Switchers, 20..Enlarged image encoders, 21.
・ Switch, 22 ・ ・ System MUX, 23 ・ ・ System Controller, 24 ・ ・ System DMUX,
25 image DMUX, 26a, 26b, 26c, 2
6d · · · wide-angle image decoder, 27 · · · enlarged image decoder, 28 · · · display, 29 · · · display system controller, 30 · · · DCT section, 31 · · ·
Quantization section, 32 .. quantization table section, 33 .. entropy coding section, 34 .. coding table section,
35 buffer part 36 encoding control part 37
..Entropy decoding section, 38 .. decoding table section, 39 .. inverse quantization section, 40 .. inverse quantization table section, 41 .. inverse DCT section, 42..switcher, 43 ..
Wide-angle image decoder, 44 ... Image cutout part, 45 ...
Upsampling part, 46..Subtractor, 47..Difference encoder, 48..System controller, 49.
.Switcher, 50..Difference decoder 51..Adder,
52..System controller

Claims (3)

[Claims] In a system in which a plurality of cameras and a plurality of abnormality detection sensors are installed at monitoring locations and a remote monitoring is performed by using an image, an image signal from a wide-angle camera and a sensor output signal are multiplexed and transmitted in normal times. An image multiplexing transmission system characterized in that remote monitoring is performed, and when an abnormality occurs, remote monitoring is performed by additionally multiplexing and transmitting an image signal of a magnified camera. 2. A transmission bit rate of an image signal transmitted by another wide-angle camera when an image signal is transmitted by an enlargement camera in a system in which a plurality of cameras and a plurality of abnormality detection sensors are installed at a monitoring location to perform remote monitoring based on an image. 2. The image multiplexing transmission system according to claim 1, wherein the overall transmission speed of the multiplexed image is kept constant by reducing the transmission speed. 3. In a system in which a plurality of cameras and a plurality of abnormality detection sensors are installed at a monitoring location to perform remote monitoring by using an image, when an image signal is transmitted by an enlarged camera, an image signal of a corresponding wide-angle camera is used. 3. The image multiplexing transmission system according to claim 1, wherein a high-efficiency encoding is performed by performing a difference operation with the up-sample and transmitting the obtained difference image.