JP3233436B2 - Video signal monitoring system in CATV transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV system capable of monitoring a reception state at an arbitrary position at a center.

[0002]

2. Description of the Related Art Conventionally, a CAT for transmitting a VHF or UHF television signal received as a spatial radio wave at a head end or an independent broadcast signal generated at a head end by a frequency division multiplex transmission system using a coaxial cable.
V transmission systems are known. In addition to the unidirectional CATV system for transmitting a video signal only from the head end to the consumer side, this CATV transmission system is capable of transmitting a signal from the consumer side to the head end side using frequency division multiplexing. CATV systems are known.

[0003]

In such a CATV transmission system, there are cases in which a customer complains to the CATV station that the image on the television is poor or the screen has noise. Such disturbances of the image disturbance include failures that are uniformly observed by all consumers, as well as local failures that are observed downstream of a specific position or only by a specific customer.

[0004] In the case of video failures throughout the system,
It is easy for the head end at the transmission source of the video signal to grasp the state of the video disturbance. However, in the case of a local fault, it is not possible to grasp the fault at the head end, and a CATV station visits the complaining customer one by one to watch the television image and determine the degree and type of the fault. I had to judge. Then, it is necessary to infer the cause of the occurrence of the failure based on the state of the failure and to estimate where in the transmission path the cause of the failure has occurred. In addition, there are cases where the video cannot be checked directly due to the convenience of the consumer. In such a case, a special operation of connecting a surveillance television to the transmission line near the consumer and watching the television image is available. Needed. Such an operation is time-consuming and takes a great deal of time to recover from a failure. The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to enable a center to monitor a state of a video signal at an arbitrary position on a transmission line in a CATV transmission system. The purpose is to facilitate understanding of the failure and investigation of the cause of the failure.

[0005]

As shown in FIG. 1, the configuration of the invention for solving the above-mentioned problem is that the transmission line E of a bidirectional CATV system having an upstream channel and a downstream channel can be freely arranged. In a system for monitoring the state of an image signal of an arbitrary downlink channel at a center at a center, the center is installed in the center, receives a video signal at a specified position on a specified channel and a transmission path, and monitors the state of the video signal by visual display. The center device A includes a device A and video signal return devices B1 to Bn inserted at an arbitrary position of the transmission path E and transmitting a video signal of a designated channel on the uplink channel. Channel designating means X1 for designating a video signal, position designating means X2 for designating an arbitrary monitoring position of a video signal on a transmission path,
Control data transmitting means X3 for modulating channel identification data specific to the channel specified by the channel specifying means X1 and address data specifying the position specified by the position specifying means X2 and transmitting the modulated data to a predetermined control channel;
Video state display means X4 for receiving a video signal from a specific monitoring channel on the transmission path E and visually displaying the status of the video signal, and
Demodulation means Y1 for receiving a signal from the downlink control channel and demodulating the signal into channel identification data and address data;
The address judging means Y2 for judging whether or not the address data demodulated by the demodulating means Y1 is the data designating the own device. Selecting means Y3 for branching and extracting the video signal of the downstream channel corresponding to the channel identification data from the transmission path E; and converting the video signal extracted from the transmission path E by the selecting means Y3 into an upstream monitoring channel and sending it to the transmission path. Surveillance video transmission means Y
4 is provided.

[0006]

A plurality of video signal returning devices are provided at arbitrary positions on the CATV transmission line. For example, inserted at an arbitrary position of a coaxial cable, or a relay amplifier, a customer terminal,
It is arranged in the tuner of the customer terminal. In the center device, a downlink channel to be monitored and a monitoring position on the transmission path are designated. The unique channel identification data for specifying this channel and the address data for specifying the monitoring position are modulated and output to a predetermined channel, that is, a control channel determined in advance.

Each video signal returning device demodulates the signal of the downlink control channel into channel identification data and address data. Then, it is determined whether or not the address data is data designating the own device. When the own device is designated, the video signal of the downlink channel designated by the demodulated channel identification data is branched and extracted from the transmission path. This video signal is frequency-converted so as to transmit a predetermined specific uplink channel, that is, an uplink monitoring channel, and is transmitted to a transmission path.

[0008] The center device receives the video signal of the monitor channel from the transmission line, and transmits the signal to a video status display device such as a television receiver or a waveform monitor based on the received video or a test signal in the video signal. Displays the waveform, signal level, S / N ratio, etc. Thus, in the center device, by specifying an arbitrary channel to be monitored and an arbitrary position to be monitored, it is possible to monitor the position and various states of the video signal of the channel.

[0009]

According to the present invention, a video signal returning device for returning a video signal of a specified channel by an upstream monitoring channel when a self-device is addressed is inserted into a plurality of arbitrary positions on a transmission line, and monitoring is performed. The data specifying the downlink channel to be monitored and the monitoring position is transmitted from the center to the transmission path, and one video signal returning device corresponding to the address data branches and extracts the video signal of the specified channel, and transfers the video signal to the upstream monitoring channel. After frequency conversion and transmission, the center receives the video signal transmitted by the monitoring channel,
This is a system in which the state of a video signal is displayed on a video state display device. Therefore, by using the system of the present invention, the center can monitor the state of the video signal of an arbitrary channel at an arbitrary position on the transmission line. Therefore, the cause of the failure and the recovery from the failure can be quickly and easily performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to a specific embodiment. FIG. 1 is a diagram showing the overall configuration of a CATV system. A transmission line E composed of a coaxial cable is provided from the head end C. In the transmission line E,
A plurality of bidirectional relay amplifiers (D1 to Dn) are provided. The transmission line E is a transmission line based on the frequency division multiplex transmission system. In the headend C, the VHF and UHF video signals received from the spatial radio waves and the independent broadcast signals, that is, the video signals reproduced by the VCR, the video signals captured by the TV camera, and the like are transmitted through the mixer through the downstream channel. Is transmitted to the transmission path E using

The channel arrangement on the transmission line E is configured as shown in FIG. The upstream channel is arranged in the low group, and the downstream channel is arranged in the high group. The uplink channel is a control channel for data transmission of channels chLc1 to chLc3,
M channels of channels chL1 to chLm for transmission of television signals, control channels for data transmission of channels chHc1 to chHc3, and n channels of channels chH1 to chHn for transmission of television signals are provided for downlink channels. ing. In this embodiment, the downlink channel chHc1 constitutes a control channel for transmitting control data, and the uplink channel chL1 constitutes a monitor channel for transmitting a video signal returned by the video signal returning devices (B1 to Bn). In the downstream channels chH1 to chHn, VHF and UHF television signals are transmitted from the head end C.

A center device A is provided at the head end C. Also, at an arbitrary position on the transmission path, that is, inserted into the transmission path E, in the relay amplifiers (D1 to Dn), in the consumer terminal F1, in the tuner of the consumer terminal F1, or the like,
Video signal returning devices (B1 to Bn) are provided.

The center device A is configured as shown in FIG. An address setting device 46 for specifying a unique address assigned to the video signal returning device and a channel setting device 47 for specifying a channel on which video is to be monitored are connected to the CPU 41 via an input interface 48. C
The PU 41 has a function of outputting the address data set by the address setting unit 46 and the channel identification data set by the channel setting unit 47 to the data modulator 45 via the output interface 44. This CP
The U41 includes a ROM 42 storing a program for controlling data transmission and a RAM 43 having a position information storage area 431 storing a correspondence relationship between an address and a position where the video signal returning device is provided on the transmission path. It is connected.

The control data transmitted from the center device A is configured as shown in FIG. That is, it is composed of address data for specifying a video signal returning device, channel identification data for specifying a downlink channel to be monitored, and command data for giving an operation command to the video signal returning device.

The output of the data modulator 45 is connected to an input / output terminal 52 via a splitter 53. The demodulator 4
Reference numeral 9 denotes a device which is connected to the input / output terminal 52 of the transmission line E via the duplexer 53, demodulates the video signal of the upstream monitoring channel of the transmission line E, and displays the video on the television receiver 50. is there. Under the control of the CPU 41, the position information of the visible display corresponding to the address is output to the output interface 44.
Is output to the video superimposing device 51 via the
By 1, the image of the upstream monitoring channel and the position information are combined and displayed on the television receiver 50. The output signal of the demodulator 49 is input to the waveform monitor 57,
The waveform monitor 57 displays the waveform of the test signal existing in a part of the video signal, the signal level is displayed as a numerical value, the frequency spectrum is displayed,
The S / N ratio and C / N ratio are displayed.

The video signal returning devices B1 to Bn are configured as shown in FIG. The transmission line E has an input terminal 34 and an output terminal 35. The input terminal 34 and the output terminal 35 are connected to power separation filters 70 and 71.
The high-frequency signal separated from the transmission line E by the power separation filter 70 is branched by the splitter 36, split by the splitter 37 and the splitter 38, and input to the data demodulator 25. The data demodulator 25 is a device for demodulating the control data output from the center device A to the control channel. The control data is transmitted to the CPU 2 via the input / output interface 24.
Read by 1.

The status data such as the pilot signals of the down channel and the power supply voltage / current are detected by various monitoring devices 39, and are transmitted to the CP via the input / output interface 24.
Read by U21. The CPU 21 stores in the ROM 22 a control program for returning the video signal of the designated downlink channel, a self-address storage area 231 storing the self-address allocated to the video signal returning device, and channel identification data. A channel / IF storing a correspondence table with frequency data for converting a signal of a channel corresponding to the data into a predetermined intermediate frequency
The RAM 23 in which the conversion frequency storage area 232 is formed is connected.

On the other hand, the branching unit 38 is connected to the IF channel selecting converter 26 for selecting only the signal of the specified channel from all the down channels and converting the signal into the intermediate frequency. The IF tuning converter 26 is connected to bandpass filters 27 and 28 via a duplexer, and the signal of the designated channel selected by the IF tuning converter 26 is
The signals are separated into video signals and audio signals by the band-pass filters 27 and 28. The video signal is input via a splitter 72 to a frequency converter 32 for converting the signal into a frequency of an uplink monitoring channel, and the frequency-converted signal is amplified by an amplifier 33. The video signal converted to the upstream monitoring channel is output from the output switch 72.
(Analog switch) through a splitter 37 and a splitter 36
Is transmitted to the input terminal 34 side.

The audio signal is input to the audio terminal of the switch 31. A data modulator 30 is connected to a data terminal of the switch 31, and a carrier generator 29 and an input / output interface 24 are connected to the data modulator.

The CPU 21 outputs status data such as a pilot signal, power supply voltage, and current detected by the various monitoring devices 39 to the data modulator 30, and the status data modulated by the data modulator 30 is transmitted via a switch 31. Output to the frequency converter 32. Accordingly, when the switch 31 is on the audio side, the video signal and the audio signal of the specified downlink channel are converted into the signal of the uplink monitoring channel by the frequency converter 32 and transmitted to the headend C side. These signals can be received by the center device A.

On the other hand, when the switch 31 is on the data terminal side, the modulated signal of the status data output by the CPU 21 is sent to the upstream monitoring channel together with the video signal instead of the audio signal.

Next, the operation of the present system will be described with reference to FIGS. 5 and 6 which show the operation procedure of the CPU 41 of the center device A and the CPU 21 of the video signal returning device. In the center device A, the operator operates the address setting device 46 to specify the address of the video signal returning device inserted into the transmission path E, thereby specifying the video signal monitoring position. Further, the user operates the channel setting unit 47 to designate a channel for monitoring the video signal.

In step 100, the address data set in the address setting device 46 is read, and in step 102, the channel identification data set in the channel setting device 47 is read. Next, in step 104, control data in a format as shown in FIG. 4 is created, and the data modulator 45 is output via the output interface 44.
Is output to The data modulator 45 FSK-modulates this control data and sends it out to the uplink control channel of the transmission line E.

By performing this operation, the demodulator 49 demodulates the signal of the upstream monitoring channel returned from the addressed video signal returning device, as described later. Then, the video signal of the monitoring channel is displayed by the television receiver 50. At this time, in step 106, the position information storage area 4 of the RAM 43 is
The position information on the transmission path corresponding to the address data stored in 31 is read out and output to the video superimposing device 51 via the output interface 44. Then, the position information is superimposed on the video demodulated by the demodulator 49 and displayed on the television receiver 50.

As a result, in the center device A, the operator can monitor the image at an arbitrary position on the transmission path E and the image of an arbitrary channel. Since the position information on the transmission path E is displayed on the image, it is easy to recognize at which position the image is located. Further, by sequentially changing the address data set in the address setting unit 46, it is possible to sequentially monitor the video at an arbitrary position on the transmission path. Further, the channel setting device 4
By changing the channel identification data set by 7, it is possible to sequentially change the channel of the video signal to be monitored.

In the video signal returning devices B1 to Bn,
Control data transmitted on the downlink control channel of the transmission path E is demodulated by the data demodulator 25. Then, in step 200, this control data is read via the input / output interface 24. Next, in step 202, the address data of the received control data
It is determined whether or not the address matches the self address stored in the self address storage area 231 of M23.

If the address data of the control data does not match the self address, the output switch 72 is turned off in step 204, and the transmission line E and the amplifier 33 are isolated from each other. Then, returning to step 200, if the address data of the control data does not match the self address, that is, if the self device is not specified, the output switch 72 is kept turned off.

If the address data of the control data matches the self address, the output switch 72 is turned on in step 206, and the output of the amplifier 33 is connected to the transmission line E. Next, in step 208,
The control item specified by the command data of the control data is controlled.

Next, at step 210, the IF conversion frequency corresponding to the channel identification data is obtained from the table stored in the channel / IF conversion frequency storage area 232 of the RAM 23. Next, in step 212, the IF conversion frequency data is output to the IF channel selection converter 26. With this, the IF channel selection converter 26
Generates a carrier of a frequency designated by IF conversion frequency data, and converts a high-frequency video signal to an intermediate frequency by the carrier. By this operation, the video and audio signals of the intermediate frequency corresponding to only the downlink channel specified by the center device A are extracted. The video signal is input to the frequency converter 32 via the band pass filter 27. The frequency is converted to a frequency in a band corresponding to the upstream monitoring channel by the frequency converter 32, amplified by the amplifier 33, and then transmitted to the transmission line E via the output switch 72. Thereby, the video signal of the specified downstream channel of the specified video signal returning device is returned to the handend C side using the monitoring channel of the transmission path E.

Next, at step 214, it is determined whether or not the command data of the control data is a status data transmission command. If a status data transmission command is given, in step 218, status data such as a pilot signal level, a power supply voltage, and a current value are read from the various monitoring devices 39. Then, in step 220, the switch 31 is switched to the terminal on the state data output side. Next, in step 222, the status data is
4 to the data modulator 30. As a result, the state data is FSK-modulated by the data modulator 30 into the audio band of the television signal, and output to the frequency converter 32 via the switch 31 and the duplexer 72. As a result, the status data is transmitted and transmitted to the handend C side along with the designated downstream channel video signal by the upstream monitoring channel. Therefore, in the television receiver 50 of the center device A, it is possible to monitor the video state at an arbitrary position on the transmission path, and to monitor the state such as the pilot signal level by separating the audio signal and demodulating the data. it can.

On the other hand, if it is determined in step 214 that no state data transmission command has been given to the control data,
In step 216, the switch 31 is switched to the audio output side. In this case, the IF channel selection converter 26
The video signal and the audio signal selected by the
Is transmitted to the frequency converter 32 via the central processing unit A, so that the center device A can monitor the state of the audio together with the video.

In the above embodiment, the upstream monitoring channel is composed of one channel, and by sequentially changing the designation of the downstream channel to be monitored and the position on the transmission path, the video at that channel and its position is changed. Since the state of the signal is sequentially monitored, a narrow uplink frequency band can be effectively used. However, a plurality of uplink monitoring channels may be used to simultaneously return different downlink channels or images at different positions and monitor them simultaneously.

In the above embodiment, the position information is combined with the video signal in the center device A, and the center device A
On the television receiver 50.
However, the video signal returning device may be configured as shown in FIG. From the signals received from the transmission path E, the signal of the channel specified by the CPU 21 is extracted by the tuner 26 and converted into a baseband video signal and an audio signal. The correspondence between the address data and the position information on the transmission path is stored in the position information storage area 632 of the RAM 63, and the position information corresponding to the address data of the received control data is extracted and output to the video superimposing device 61. You. In the video superimposing device 61, the baseband video signal selected by the tuner 26 and the video signal of the position information are superimposed, and the superimposed signal is modulated by the modulator 6.
2 is output.

As a result, in the center device A, as shown in FIG. 8, a video superimposing device for superimposing the position information and the monitoring image is not required, and the image on which the position information is superimposed by the video signal returning device is transmitted to the television. It is displayed on the image receiver 50.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a center device.

FIG. 3 is a block diagram showing a configuration of a video returning device.

FIG. 4 is an explanatory diagram showing a configuration of control data.

FIG. 5 is a flowchart showing a processing procedure of a CPU of the center device.

FIG. 6 is a flowchart showing a processing procedure of a CPU of the video returning device.

FIG. 7 is an explanatory diagram showing a channel arrangement on a transmission path.

FIG. 8 is a block diagram showing a configuration of a center device according to another modification.

FIG. 9 is a block diagram showing a configuration of a video signal returning device according to another embodiment.

[Explanation of symbols]

 A: Center device B1 to Bn: Video signal returning device D1 to Dn: Relay amplifier E: Transmission line C: Hand end 46: Address setting device 47: Channel setting device 26: IF channel selection converter 32: Frequency converter 31: Switching device 30 … Data modulator

Continuation of the front page (56) References JP-A-3-108988 (JP, A) JP-A-3-46487 (JP, A) JP-A-3-135294 (JP, A) JP-A-1-265796 (JP) JP-A-4-7927 (JP, A) JP-A-47-45325 (JP, A) JP-A-1-288190 (JP, A) JP-A-3-248659 (JP, A) 2-14693 (JP, A) JP-A-5-83708 (JP, A) JP-A-4-304797 (JP, A) JP-A-4-227196 (JP, A) JP-A-61-56588 (JP, A) A) JP-A-59-15386 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 7/10 H04N ^7/ 14-7/173 H04N ^7/ 20-7/22 H04N 17/00-17/06

Claims (1)

(57) [Claims] 1. A system for monitoring, at a center, the state of a video signal of an arbitrary downlink channel at an arbitrary position on a transmission line of a bidirectional CATV system having an uplink channel and a downlink channel. A center device that receives a video signal at a specified position on a transmission path and monitors the state of the video signal by visual display; and a video that is inserted at an arbitrary position on the transmission path and transmits a video signal of a specified channel on the uplink channel. A signal returning device, wherein the center device includes: a channel specifying unit that specifies an arbitrary downlink channel to be monitored; a position specifying unit that specifies an arbitrary monitoring position of a video signal on a transmission path; and the channel specifying unit. Channel identification data unique to the channel specified by the Control data transmitting means for modulating address data specifying the location and transmitting the modulated data to a predetermined control channel; receiving a video signal from a specific monitoring channel on the transmission line, and displaying a visual display of the state of the video signal Status display means, and the video signal returning device receives a signal from a downlink control channel, demodulates the channel identification data and address data, and decodes the address data by the demodulation means. Address determining means for determining whether or not the data specifies the own device; and, when the own device is specified by the address determining means, a video signal of a downlink channel corresponding to the channel identification data demodulated by the demodulating means. Selecting means for branching and extracting the video signal from the transmission path; and monitoring the video signal extracted from the transmission path by the selection means. CATV comprising a monitor video transmitting means for converting the frequency into a channel and transmitting the converted video to the transmission path.
Video signal monitoring system in the system.