JPH03135182A - Video transmission system - Google Patents

Abstract

PURPOSE:To display a multiplex video image inexpensively and selectively by switching plural video frames sequentially, sending the selected frame to one transmission line, segmenting a frame on a display device at a receiver side, storing the result and interpolating the missing frame of a relevant video frame. CONSTITUTION:Video signals from cameras 1a-1d are selected by a multiplex section 4 in a predetermined sequence and the result is sent to a transmission line 5 as a multiplexed video signal, receivers 2a-2d segment a required video image and the image is displayed. The multiplexed video signal from the transmission line 5 is converted by an A/D converter 28 and sent to a frame buffer memory 24 via a frame buffer write gate 23. A synchronizing signal separation section 21 separates a synchronizing signal and the signal is sent to a selection section 22, a frame (FR) is selected once per 4 frames and the video signal for the frame is written in the memory 24. The same frame is displayed for a period when the frame is missing by multiplexing, the frame is revised when a frame is written newly and an optional video image is selected by a selector switch 29. Thus, lots of video images are sent through a few transmission lines and the multiplexed video image is displayed selectively and inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal transmission system, and particularly to a transmission system suitable for multiplexing and transmitting a plurality of video signals.

[Conventional technology]

Television cameras are used for safety monitoring at dams, rivers, railways, etc., but since a broadband transmission line is required for transmission, a method is used in which the receiving side sends a selection signal to the transmitting side to switch. is used. In addition, in order to send these simultaneously, frequency multiplexing is performed using synchronization cables, microwaves, etc.
Alternatively, there is a method of time-division transmission using optical fiber cable transmission (Japanese Patent Application Laid-open No. 10380/1983,
(Refer to Publication No.-67940).

[Problem to be solved by the invention]

However, in the former case, only one information source can be received at a time, while in the latter case, although it is possible to view the information simultaneously, the transmission system becomes extremely expensive.

In addition, a method of splitting and composing multiple moving images in one transmission frame (Japanese Patent Application Laid-Open No. 62-78980, Japanese Patent Application Laid-Open No. 62-108
However, there are problems in that the resolution of one channel decreases and the circuit configuration for performing synthesis becomes complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method that can realize time-division transmission relatively inexpensively and easily when dividing and displaying a plurality of videos on one screen.

[Means to solve the problem]

The above purpose is to sequentially switch video frames sent from multiple cameras or recording media and send them out to a single transmission path, while the receiving side displays one or more display devices in synchronization with the switching on the transmitting side. .

This is accomplished by cutting out frames, storing them, and interpolating the missing periods of the corresponding video frames.

[Effect]

In order to achieve the above objective, it is necessary to synchronize the frames of each video source device, but this is done by sending a synchronization signal from the multiplex transmission device to each video source device and synchronizing all frames. Later, the frame separation, i.e.
The signals are sequentially switched and transmitted using the vertical synchronization period as the switching timing.

On the other hand, the receiving side selects one or more frames of any order in the switching period based on the vertical synchronization signal of the transmitted video signal, with the same period as the switching period of the transmitting side, and Store it in the frame buffer memory and display it once.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 1a to 1d are television cameras, 2a to 2d are receivers, 3 is a synchronizing signal generator, 4 is a multiplexer, 5 is a video signal transmission line, 6 is a selection command unit, and 7 is a selection command transmission line. be.

In the above configuration, the synchronization signal generator 3 generates a synchronization signal, sends it to each of the television cameras 1a to 1b, and synchronizes the frames of each camera. On the other hand, the cameras 1a to 1d send their respective video signals to the multiplexing section 4, and the video signals 1a to 1d are switched in a predetermined order at the vertical synchronization period. The video signals multiplexed in this manner are supplied to the image receivers 2a to 2d through the transmission line 5.

These multiplexed video signals are shown in 2a to 2d.

Cut out and display the necessary video.

On the other hand, if it is desired to specifically change the switching order or multiplexing ratio, a selection command is sent from the selection command unit 6 through the transmission line 7 to the multiplexing control unit 4, which multiplexes the video based on the command.

In this multiplexing, as shown in FIG. 2, for example, when four cameras are multiplexed, each camera has F a ”
The video frames of F a are sent to the multiplexing unit 4 in parallel, but the multiplexing unit 4 sequentially switches the multiplexed frames FM
Send as.

In this example, the frame Fa of camera 1a is sent once every 2 frames, and the other frames are sent once every 5 frames.If you want to monitor camera 1a in detail, you can multiplex it using this schedule, but the same ratio i.e. 1 in 4
It goes without saying that multiplexing can be easily achieved in any arbitrary manner (this is called a mode), such as by a ratio of 1.0 times, or by only 1, 2, or 3 devices.

Such a multiplexing mode is commanded by the selection command section 6.

On the other hand, on the receiver side, a selective receiver circuit as shown in FIG. 3 cuts out and displays a necessary frame.

In FIG. 3, 2o is a video signal amplification section, 21 is a synchronization signal separation section, 22 is a selection section, 23 is a frame buffer write gate, 24 is a frame buffer memory, 25 is a display control section, and 26 is a D/A conversion section. 27 is a cathode ray tube,
28 is an A/D converter.

In the above configuration, the multiplexed video signal arriving from the transmission line 5 is digitized by 28. On the other hand, 21 separates the synchronization signal from the video signal and sends it to the display control section and also sends it to the selection section 22. The selection unit 22 counts the vertical synchronization signals, and if, for example, 1a to lb are multiplexed at an equal ratio, that is, once every four frames, a quaternary counter counts the vertical synchronization signals once every four frames. One frame is selected and the video signal of that frame is written into the frame buffer memory. The written frame displays the same frame during the frame period that is missing due to multiplexing, and is updated when a new frame is sent.

In this case, if you want to select a different video, you can select the video from any television camera by selecting the channel (what frame) using the selection switch, for example. On the other hand, if you want to divide multiple images into screens and display them simultaneously, the display control unit controls the write address of the frame buffer, and the video signal is divided into four video signals by 1/4, that is, horizontal scanning 2 By sparsely sampling horizontally one per book and writing it into a part of the frame buffer, it is possible to display four screens on a separate screen.

On the other hand, when multiplexing at equal ratios or not multiplexing as in 1 or more, tuning is not recommended, but if the multiplexing ratio is different, how will the tuning side select the necessary frames? becomes a problem.

Therefore, as shown in Figure 4, by inserting an identification signal into the synchronization signal section of the composite video signal and decoding it in the synchronization signal separation unit, it is possible to identify which camera the frame sent by the transmitting side belongs to. can do.

This identification signal may be an independent signal for each camera, or may be selected in a numbered manner based on the beginning of the multiplexing repetition cycle.

〔Effect of the invention〕

As described above, according to the present invention, a large number of videos can be sent through a small number of transmission paths, and the multiplexing device is also simple. on the other hand,
As memories become cheaper, TVs with frame buffers are becoming more practical, and TV receivers can selectively display multiplexed images at relatively low costs, which has great economic effects.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 is a time chart showing the operating principle of the invention, Fig. 3 is a circuit configuration diagram of the receiver, and Fig. 3 is a diagram showing the video signal waveform. . 18-1d...TV camera, 2a-2d...Receiver, 3...Synchronization signal generation section, 4...Multiplexing section, 5.
...Video signal transmission line, 6...Selection command unit, 7...Command transmission line. VJ 1st/fsYN η -yT cI dm person 47 cases

Claims (1)

[Claims] 1. When transmitting video information using a television camera or the like that sends out moving images by frame scanning, when multiplexing multiple videos and transmitting them, the frames of each video are synchronized and sequentially transmitted frame by frame. The video is switched and sent to one transmission line in a time-division manner, and the receiving side specifies the switching in synchronization with the switching on the transmitting side.
Store frames of the video source in frame buffer memory,
A video transmission method characterized by interpolating and displaying frame missing periods. 2. In the video transmission method described in item 1, when sequentially switching and transmitting the frames, a video source identification signal is inserted into the synchronization signal section, identified on the receiving side, and the video of the desired video source is cut out and displayed. do. 3. In the video transmission system described in item 2, the identification signal is encrypted. 4. In the video transmission system described in item 1, an arbitrary number of video sources are specified, stored in the frame buffer memory, and a plurality of videos are simultaneously displayed on one display device by screen division. 5. In the video transmission method described in paragraph 1, from the receiving side,
The above multiplexing procedure on the transmitting side is specified, and multiple frames are multiplexed at an arbitrary ratio.