GB2319422A

GB2319422A - CCTV surveillance system video multiplexing apparatus for time-lapse video recording

Info

Publication number: GB2319422A
Application number: GB9623845A
Authority: GB
Inventors: Christopher Malcolm Hall
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-11-16
Filing date: 1996-11-16
Publication date: 1998-05-20
Anticipated expiration: 2016-11-16
Also published as: GB2319422B; GB9623845D0

Abstract

A video multiplexing apparatus 12 has a multiplexer 18 for passing a video signal derived from a video input selected, in dependence upon a control signal CS1, to a video output for supply to a time-lapse video recorder 14. A controller 20 is operable in a manual mode to supply the control signal CS1 to the multiplexer so as to cycle the selection of the multiplexer video input at a manually selectable rate. A visual display 34 responsive to the controller displays information dependent on the selected rate, so that an operator can readily see whether the multiplexing apparatus 12 and the video recorder 14 are properly set up.

Description

TITLE Multiplexing Apparatus for Video Recording System DESCRIPTION This invention relates to a video multiplexing apparatus and to a video recording system including such an apparatus. The invention is particularly applicable in the field of timelapse CCTV surveillance of premises for security purposes, but is also applicable in other fields.

Video multiplexing apparatus is well known, and one particular form of such apparatus used in this invention comprises: a plurality of multiplexer video inputs for connection to respective video camera outputs; a multiplexer video output for connection to a recorder video input of a video recorder; a multiplexer for passing a video signal derived from a selected one of the multiplexer video inputs to the multiplexer video output in dependence upon a control signal; and a controller operable in a manual mode to supply the control signal to the multiplexer so as to cycle the selection of the multiplexer video input at a manually selectable rate.

When used in a video recording system in conjunction with a video recorder having its video input connected to the multiplexer video output, the multiplexing apparatus is typically operable to supply video frames continuously to the video recorder, and the video recorder is operable to record one in every selectable number N of the supplied frames. In a typical known system, the number N is manually selectable; the video recorder has a control output for providing a second control signal dependent on the rate at which the frames are recorded by the video recorder; the video multiplexing apparatus has a control input for connection to the recorder control output; and the controller of the multiplexing apparatus is alternatively operable in an automatic mode to supply the first-mentioned control signal to the multiplexer so as to cycle the selection of the multiplexer video input at a rate dependent on the second control signal. The video recorder usually has a visual display operable to display information dependent on the number N (for example the number of hours that a three hour video tape will last with the currently selected time-lapse).

When such a system is used in the automatic mode, it may well operate perfectly satisfactorily. However, such systems are not infrequently used in the manual mode, for example because nobody has bothered to connect a cable from the recorder control output to the multiplexer control input, because the cable has been lost or damaged, or because the operator does not know how to operate the system properly. In these circumstances, if the video recorder and the multiplexing apparatus are not set to the same rate, then an unsatisfactory recording is likely to result.

In order to assist in preventing this problem, the multiplexing apparatus of the present invention is characterised by a visual display responsive to the controller to display information dependent on the selected rate (for example the number of hours that a three hour video tape will last with the rate currently selected for the multiplexing apparatus).

Accordingly, when in the manual mode, the display on the multiplexing apparatus may be checked by the operator against the display on the video recorder to which the multiplexing apparatus may be connected, and if there is a discrepancy the operator will hopefully realise that further action is necessary to set up the system properly.

A specific embodiment of the present invention will now be described by way of nonlimiting example with reference to the accompanying drawing, which is a block diagram of a CCTV system.

The CCTV system shown in the drawing comprises four video cameras 10A to 10D, a multiplexing apparatus 12, a time-lapse video recorder 14 and a monitor 16. The multiplexing apparatus 12 comprises a multiplexer 18 having four video inputs each connected to a respective one of the video cameras 10A to 10D, a control input which receives a control signal CS1 from a microprocessor 20, and a video output connected to a recording frame buffer 22 and a monitor frame buffer 24. The filling and emptying of the frame buffers 22, 24 and time base correction is controlled by the microprocessor, or alternatively a time base correction circuit may be provided before the video inputs to the multiplexer 18. An output from the recording frame buffer 22 is fed to the video tape recorder 14 via a coder circuit 26 which, under control of the microprocessor 20 adds to the first few lines of each video frame a code indicative of the time and date and which of the cameras 10A to 10D supplied that frame. An output from the monitor frame buffer 24 is fed to the monitor 16, and the monitor frame buffer 24 may be controlled by the microprocessor 20, in response to manually operable mode selection switches 28 so that each frame displayed by the monitor is made up of reduced scale frames from each of the video cameras 10A to 10D, or so that the displayed frames cycle around the cameras 10A to 10D.

The mode selection switches can also be used to select a rate of cycling of the control signal CSl to the multiplexer 18, for example to select a 3 hour mode, 6 hour mode, 12 hour mode, 24 hour mode or an automatic mode. If, starting from a particular time, the frames from the video camera 10A are denoted as A0, Al, A2 ...., from the camera 10B as B0, B1, B2 ..., and so on, soon, then in the 3 hour mode, the frames output from the multiplexer 18 are A0, B1, C2, D3, A4, B5, C6, D7, .. . In the 6 hour mode, the frames output from the multiplexer 18 are AO, Al, B2, B3, C4, C5, D6, D7, .. . In the 12 hour mode, the frames output from the multiplexer 18 are AO, Al, A2, A3, B4, B5, B6, B7, . . Similarly, in the 24 hour mode, a sequence of eight (=24/3) frames are supplied from each camera before cycling to the next camera. The automatic mode will be described later.

The video tape recorder 14 has a manually operable mode selection switch 30 which can be used to select the time-lapse mode of the recorder 14, for example a 3 hour mode, 6 hour mode, 12 hour mode, or 24 hour mode. In the 3 hour mode, the recorder 14 records every frame received, whereas in the 6 hour, 12 hour and 24 hour modes, the recorder records only one in every two, four and eight, respectively, of the received frames. The recorder 14 has a digital display 32 which is operated to display the mode which has been selected. The recorder 14 also has a control output which provides a pulse in a signal CS2 each time a frame is recorded, and the control signal CS2 is supplied to the microprocessor 20 of the multiplexing apparatus 12.

When the multiplexing apparatus 12 is set by the switches 28 to its automatic mode, the microprocessor 20 changes the control signal CSl each time there is a pulse in the control signal CS2. It will therefore be appreciated that, if the recorder 14 is set to its 3-hour mode, and if the multiplexing apparatus is set to its 3-hour mode or to its automatic mode, then the frames which are recorded are A0, B1, C2, D3, A4, B5, C6, D7 .... . If the recorder 14 is set to its 6-hour mode, and if the multiplexing apparatus is set to its 6-hour mode or to its automatic mode, then the frames which are recorded are A0, B2, C4, D6, A8, B10, C12, D14, .. . If the recorder 14 is set to its 12-hour mode, and if the multiplexing apparatus is set to its 12-hour mode or to its automatic mode, then the frames which are recorded are A0, B4, C8, D12, A16, B20, C24, D28, Similarly, if the recorder 14 is set to its 24-hour mode, and if the multiplexing apparatus is set to its 24-hour mode or to its automatic mode, then the frames which are recorded are A0, B8, C16, D24, A32, B40, C48, D56 .... Accordingly, successive recorded frames are derived, in turn, from the different cameras.

The problem which arises with the system as described so far is that if the multiplexing apparatus 12 is set to manual mode which does not correspond to the mode of the recorder 14, then the recording may omit frames from one or more of the cameras. For example, if the recorder 14 is set to its 6-hour mode and the multiplexing apparatus is set to its 3-hour mode, then the frames which are recorded will be A0, C2, A4, C6, and the frames from cameras 10B and 10D will be lost. Similarly, if the recorder 14 is set to its 24-hour mode and the multiplexing apparatus is set to its 6-hour mode, then the frames which are recorded will be A0, A8, A16, A24, ..., and the frames from cameras 10B, 10C and 10D will be lost. In order to help overcome this problem, the multiplexing apparatus 12 is provided with a digital display 34 which is operated so as to display the manually selected mode of the multiplexing apparatus 12, for example as "3HR", "6HR", "12HR" or "24HR". The operator can then compare the display 34 of the multiplexing apparatus 12 with the display 32 of the recorder 14, and if they do not correspond, the operator may then take action to remedy the situation. When the multiplexing apparatus 12 is in its automatic mode, the display 34 may either be used to indicate that fact, for example "AUTO", or the microprocessor 20 may derive the current rate from the control signal CS2 and cause the display 34 to indicate that rate.

It will be appreciated that many modifications and developments may be made to the system described above.

Claims

CLAIMS The reference numerals in the claims do not form part of the definition of the invention for which protection is sought.

1. A video multiplexing apparatus (12), comprising: a plurality of multiplexer video inputs for connection to respective video camera outputs; a multiplexer video output for connection to a recorder video input of a video recorder (14); a multiplexer (18) for passing a video signal derived from a selected one of the multiplexer video inputs to the multiplexer video output in dependence upon a control signal (CS 1); a controller (20) operable in a manual mode to supply the control signal to the multiplexer so as to cycle the selection of the multiplexer video input at a manually selectable rate; and a visual display (34) responsive to the controller to display information dependent on the selected rate.

2. A video recording system, comprising: a multiplexing apparatus as claimed in claim 1; and a video recorder (14) having a recorder video input connected to the multiplexer video output; wherein the multiplexing apparatus is operable to supply video frames continuously to the video recorder, and the video recorder is operable to record one in every selectable number N of the supplied frames.

3. A system as claimed in claim 2, wherein: the number N is manually selectable; the video recorder has a control output for providing a second control signal (CS2) dependent on the rate at which the frames are recorded by the video recorder; the video multiplexing apparatus has a control input for connection to the recorder control output; and the controller of the multiplexing apparatus is alternatively operable in an automatic mode to supply the first-mentioned control signal to the multiplexer so as to cycle the selection of the multiplexer video input at a rate dependent on the second control signal.

4. A system as claimed in claim 2 or 3, wherein the video recorder has a visual display (32) operable to display information dependent on the number N.

5. A video multiplexing apparatus or a video recording system, substantially as described with reference to the drawing.