JPS6127945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for transmitting moving image signals economically and with good image quality through a narrowband transmission path.

Today, standards for image signals in broadcast television are set from the perspective of making general home receivers more economical, and in Japan, in order to prevent flickering in the received image, the screen is set at 60 fields per second.
Broadcasting is carried out using a 4MHz band signal. A similar type of camera is sometimes used in industrial televisions, etc., but in order to transmit the 4MHz band signal by wire, a coaxial cable must be installed, and if a balanced telephone cable is used, crosstalk attenuation is required. Since there is not enough quantity, it is necessary to select the cores to avoid crosstalk. Furthermore, since the amount of attenuation is large in the high frequency range, a large number of repeaters are required for long-distance transmission. In order to solve this high transmission cost, several methods have been proposed to perform transmission using a narrowband transmission path.

FIG. 1 is a diagram showing an example of a conventional narrowband transmission system. In Figure 1, 1 is a television camera, 2
is a narrowband transmission line, 3 is a television receiver, 4 is a (frame or field) image storage device, 5 is a switch, 6 is a time expansion circuit, 7 is a time compression circuit, 8
(frame or field) image storage,
shows.

In the system shown in FIG. 1, an image storage device 4 is provided on the image sending side in order to transmit the output signal of the television camera 1 to the television receiver 3 via the transmission path 2 with a band of 1/n of the signal. The camera output is input to the storage device 4 every n frames by the switch 5 and is stored therein. The stored information is transmitted through the narrowband transmission line 2 by expanding the time by n times, that is, by compressing the signal band to 1/n by the time expansion circuit 6. On the receiving side, the received narrowband signal is time-compressed to 1/n by the time compression circuit 7, written to the image storage device 8, and outputted repeatedly n times to reproduce the screen on the television receiver 3. do. This narrowband transmission method is called the speed conversion type.

In addition, with the same configuration as above, on the transmitting side, the correlation between pixels within a frame, between frames, etc. is taken according to the storage contents of the image storage device, and the band is compressed to produce a transmission signal, and on the receiving side, the signal is stored in the image storage device. There is also a method of reproducing the content into an original image based on the correlation between pixels.

FIG. 2 is a diagram showing another example of the conventional narrowband transmission system. In FIG. 2, reference numeral 12 indicates a low-speed scanning type television camera. In this television camera 12, a narrow band signal output is directly obtained by scanning the image pickup tube at low speed. The transmission path and receiving side equipment are the same as in the case of FIG. Such a narrowband transmission method is called a slow scanning narrowband transmission method.

Since conventional narrowband transmission systems have the configuration described above, they either require a large-capacity image storage device on the transmitting side or use a slow-scanning camera. The disadvantage was that even if roads were used, they could not bring about sufficient economic benefits. In addition, the image quality deteriorates due to the addition of image storage device noise or increased camera noise due to slow scanning.
In the case of a screen with rapid movement, the speed conversion type compresses the movement of n frames of the original surface into one frame time, making the movement awkward, while the band compression type reduces the correlation between pixels, so the same Image quality deteriorates because transmission is no longer possible through the high-capacity transmission path, and with low-speed scanning, the difference in time taken by the camera to scan between the top and bottom of the screen is large, resulting in distortion of the screen and movement of the deformation point. There were flaws. In addition, in the case of the low-speed scanning type, in order to monitor the image sending screen, a time compression circuit and an image storage device are required like those on the image receiving side, and the disadvantage is that such expensive equipment is required.

This invention was made in order to overcome the drawbacks of the prior art as described above, and the purpose of this invention is to provide a novel narrowband moving image that is economically inexpensive and that exhibits less deterioration in image quality. This provides an image signal transmission system.

The main point of the configuration of the present invention is that in the narrowband video signal transmission system, the output signal of the imaging camera is extracted every n lines for one frame at the transmitting end, and another line is extracted every n lines for the next frame. Below, in the same way, the entire original image is scanned in n frames, and when the horizontal 1/m part of the screen is necessary information and the rest is unnecessary information, lines with necessary information in each field are scanned. In addition to extracting every m lines, information on other lines is temporarily stored in a buffer memory, and is extracted again when unnecessary information is scanned.

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 4 is a diagram showing an embodiment of the present invention. The present invention will be described with reference to a case where a signal is transmitted through a transmission line 2 having a band that is 1/n of the output signal band of the camera 1. In the narrowband transmission system shown in FIG. 4, the switch 5 closes the output signal of the camera 1 every n lines for one frame, and
(where n is a positive number). In the next frame, different lines are selected every n lines and added to the time expansion circuit 6, so that the entire original image is scanned in n frames. The time expansion circuit 6 expands this signal to n times the time, thereby converting the signal into a band of 1/n and transmitting it to the narrowband transmission line 2. On the receiving side, the time compression circuit 7 compresses the signal to 1/n of the time, and rewrites the stored contents of the image storage device (frame memory) 8 for each receiving line. By repeatedly reading this, the transmitted image can be reproduced on the television receiver 3.

For example, if the method of this invention is applied to the case of n=4 in the case of a screen with 30 frames and 60 fields per second like a normal camera, each line will be n/
30 = 4/30 = It is rewritten with new information once every 1/7.5 seconds, but when viewed in units of 4 lines, it changes once every 1/30 seconds. Therefore, even if the movement is rapid, the movement will not appear unnatural on the playback screen.

FIG. 3 is a diagram showing how FIG. 3A and FIG. 3B are connected, and FIG. 3A and FIG. 3B constitute one diagram by being assembled as shown in FIG. This is a diagram that compares the movement of the screen when a rectangular object moves from the first frame to the fourth frame, where a is a normal TV screen, b is a speed conversion screen, and c is a low-speed scanning screen. d shows the screen of the method according to the present invention.

In FIG. 3, in speed conversion type b, which is one of the conventional methods, n frames of the original image (in the illustrated example, 4
The motion of 1 frame) is compressed into the time of 1 frame, which makes the motion awkward, and in slow scan type c, there is a large difference between the camera scanning the top and bottom of the screen, which causes the screen to become distorted. In addition, it can be seen that the deformation point moves. On the other hand, in method d according to the present invention, the screen of each frame is a screen different from the shape of the moving object, but unlike the conventional methods b and c, the movement is awkward and the deformation point of the screen is Since movement is not detected, as in the case of a normal television screen a, there is almost no need to notice any deterioration in image quality from the recognition of the shape of the object before and after the movement. Therefore, in this example, a 4MHz video signal can be converted to 1MHz without deteriorating the image quality.
It can be transmitted in the band.

FIG. 5 is a diagram showing another embodiment of the invention. FIG. 6 shows a horizontally divided screen in which there are parts that do not require transmission and parts that require transmission.

In the screen shown in FIG. 6, it is assumed that a 1/m portion of the horizontally divided screen is information that needs to be transmitted (where m is a positive number), and the remaining (1-1/m) portion is information that does not need to be transmitted. The embodiment shown in FIG. 5 works effectively when transmitting such a screen. In Figure 5, 5
5 is a switch, and 9 is a buffer memory whose number of lines is (m-1)/m ² times the number of lines of one field. In FIG. 5, the output of the camera 1 is input directly to the time expansion circuit 6 by a switch 55 for every m lines of lines that have information to be transmitted out of each field, and the information on other lines is input to the buffer memory 9. The camera output signal is once stored, read out at a time when the camera output signal does not include the required transmission information, and inputted to the time expansion circuit 6. The time expansion circuit 6 is
The input signal is time-expanded by m times and sent to the narrowband transmission line 2. On the receiving side, the received signal is compressed to 1/m by a time compression circuit 7, and an image storage device (frame memory) 8 having a capacity of 1/m frame is stored.
write to. When reading from the image storage device 8,
The information directly sent and written by the transmitter switch 55 during writing and the buffer memory 9
The information is read from the image storage device 8 in the same line order as the original signal by adjusting the arrangement with the information that was once stored and later sent out and written. The original picture can be read out and reproduced on the television receiver 3. By doing so, horizontally divided screen information of 1/m can be transmitted in a signal band of 1/m, which is very economical. The capacity of the buffer memory 9 required in this system is small compared to the capacity of the storage device required on the transmitting side in the conventional speed conversion type, so it does not impede economy.

In the above description of the embodiments of the present invention, the case where a moving image is formed with n frames and the case where the horizontally divided screen is divided into 1/m have been described, but these can be combined to generate a signal with a band of 1/n/m. Of course, it can be transmitted. In addition, in the explanation, the contents of the image storage device are rewritten after time compression is performed on the receiving side, but the received narrowband signal is written to a low-speed memory, and then passed through a time compression circuit and input to the receiver in the same way. Needless to say, the screen can be played back.

As is clear from the above detailed explanation, the narrowband video signal transmission method of the present invention does not require a large-capacity image storage device or a low-speed scanning camera on the transmitting side, and is therefore superior to conventional methods. This has the great effect of reducing transmission costs and providing good image quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional narrowband transmission system, and FIG. 2 is a diagram showing another example.
FIG. 3 is a diagram showing how FIG. 3A and FIG. 3B are connected. FIG. 3A and FIG. 3B constitute one diagram by being put together as shown in FIG. FIG. 4 is a diagram showing a comparison between various methods of screen movement of a television image when moving, and FIG. 4 is a diagram showing one embodiment of the present invention, and FIG. 5 is a diagram showing another embodiment of the present invention. FIG. 6 is an explanatory diagram showing an example of a screen. In the figure, 1 is a television camera, 2 is a transmission line,
3 is a television receiver, 4 is an image storage device, 5 is a switch, 6 is a time expansion circuit, 7 is a time compression circuit, 8
12 is a low-speed scanning television camera, 55 is a switch, and 9 is a buffer memory.

Claims (1)

[Claims] 1 In a narrowband video signal transmission system consisting of a transmitting end that transmits a video signal, a receiving end that receives the signal, and a narrowband signal transmission path connecting both ends, one of the output signals of an imaging camera is connected to the transmitting end. The switch is equipped with a switch for switching and extracting the part, a time expansion circuit and a buffer memory into which the signal extracted by the switch is input, and when 1/m of the original image signal output from the imaging camera is the information to be transmitted, the switch For the required transmission information, a signal is extracted every m lines from each field and inputted directly to the time expansion circuit, and the signals of other lines are inputted to the buffer memory, and the signals of the other lines stored in the buffer memory are , the imaging camera output signal is read out at a time that does not contain the required transmission information and is input to the time expansion circuit, and the time expansion circuit time-expands the input signal by m times and sends it to the narrowband signal transmission path. The output signal band of the imaging camera is m
A narrowband video signal transmission method that transmits image signals in a 1/2 band, and at the receiving end, the image signals are once stored in a frame memory and then reproduced (where m is a positive number). ).