GB2341290A

GB2341290A - Method of operating a surveillance system

Info

Publication number: GB2341290A
Application number: GB9819182A
Authority: GB
Inventors: Peter Robin Watson Vaughan
Original assignee: JASMIN SIMTEC Ltd
Current assignee: JASMIN SIMTEC Ltd
Priority date: 1998-09-04
Filing date: 1998-09-04
Publication date: 2000-03-08
Also published as: GB9819182D0

Abstract

A method of operating a surveillance system (10) comprising a video imaging means (11), and a data recorder (14) having a temporary data storage means (17) which permits of random access to the data stored thereon, and a processor means (18), the method including processing a video signal provided by the video imaging means (11), of an event being surveyed, according to an algorithm, to produce compressed data and writing the compressed data to the temporary data storage means (17).

Description

2341290

Title: Method of Operating a Surveillance System Description of Invention

This invention relates to a method of operating a surveillance system.

In a security environment, such systems are used to survey events occurring in a surveyed area. Conventionally, such systems comprise one or more video cameras and a video recorder of the kind which uses video tape to record surveyed events.

In one typical application, a video signal from the camera or cameras is stored directly onto a video tape. Although such video tape may be reused, it is often necessary to store a substantial volume of video tapes to keep a record of events which may need to be reviewed subsequently. For example where a surveillance system is used in an environment where there is no continual real time monitoring of events, e.g. by an operator viewing the video output from the camera or cameras on a video monitor, a substantial duration of time may be recorded on video tape which may need to be kept for a long time so that in the event that it is necessary to review a recorded event subsequently, such record is available.

Commercially available video tapes are bulky, and events recorded thereon may only be reviewed sequentially, i.e. in the order in which they occurred, although such tapes may be played at faster rates to assist searching for an event. The problem of storage is aggravated because of the need to keep a master copy for evidence when required, requiring the copying of the master for other uses.

An advantage of video tapes is however that it is simple to record, at the same time as recording the event, the time of the event, by wntina this information onto the video tape. Thus although the tampering with such video 0 2 tapes is possible, it is made difficult by the inclusion of time information. Evidence of an event in the format of a video tape has thus been found to be acceptable even in legal proceedings.

In an application where an event surveyed by a video camera, for example, is monitored in real time by an operator, it is a requirement that an operative is able substantially instantly to replay a record of an event. Where only, a single video recorder is used this would involve the operator rewinding the tape to the correct position during which rewinding time the operator would not be able to continuing monitoring in real time. In a large and complex system, e.g. which comprises several video cameras and perhaps several video recorders all of which may not be readily available to the operator, the instant replaying of a surveyed event can be difficult.

It is known to utilise a computer for data recording purposes and particularly,, for recording video information. However, particularly where C evidence of an event is required for legal proceedings, such evidence in the form of computer stored data has not been considered to be acceptable.

This is because to store digitally a video signal on a digital storage 0 medium such as a computer hard disc, the video signal has to be processed. Such processing necessarily involves producing compressed data to optimise the hard disc space available. Such processing involves using an algorithm.

Available algorithms such as MPEG produce compressed data in a predictive sense, in that in order to re-process the stored data for playing a frame of video image, it is necessary to have information available of C> subsequent frames of irnage. Thus although such algorithms are useful for entertainment purposes for example, due to the nature of the algorithm, compressed data relating to a surveyed event is considered unreliable from a legal point of view. Additionally, it is not convenient to include on the record, a record of the time of the event, and accordingly such data is more capable than video tape say, of being tampered with.

3 Moreover although a computer may be programmed to facilitate the playback of a recorded event, by the nature of the known MPEG algorithm used to produce the compressed data, it is not possible to view an event sequentially forwards and backwards which may be necessary to establish the exact nature of the event. Rather, it is necessary to View the recorded event sequentially forwardly.

Another compression standard is JPEG but this is for still picture compression on digital storage medium. This has been adapted for use in compressing a sequence of (digital) still images, in a format known as MJPEG. Although the video quality achieved using MJPEG is higher than with MPEG, the amount of data compression achieved is much less, making the use of MJPEG for storing long video sequences, unattractive.

Accordingly conventional computer based video information storage systems have not lent themselves to use in the surveillance industry for recording surveyed events.

According to a first aspect of the invention we provide a method of operating a surveillance system comprising a video imaging means, and a data recorder, the data recorder comprising a temporary data storage means which permits of random access to the data stored thereon, and a processor means, the method including processing a video signal provided by the video imaging means, of an event being surveyed, according to an algorithm, to produce compressed data and writing the compressed data to the temporary data storage C means- Thus a digital data recording system may be successfully used in a surveillance application.

To optimise efficiency of the use of the temporary data storage means C the method may include processing the video signal of an event being surveyed with the processor means to produce first compressed data which is able to be re-processed and played back on a video monitor at a first real time fi-ame rate, 4 and second compressed data which is able to'be re-processed and played back on a video monitor at a second, slower, real time frame rate, the processor means being adapted to write the first and the second data to the temporary data storage means, and to overwrite the first data after a predetermined time.

Thus where it is unnecessary to store data for all the video information, e.g. where no significant event is surveyed, excess data can be overwritten to free up storage space of the temporary data storage means.

However means may be provided to inhibit overwriting of at least some of the first data e.g. as and ',A,'hen a significant event is surveyed. This may be initiated manually by an operator or automatically in response to the event, but in each case the data recorder may have means to provide an external input to the processor means, and the processor means may be adapted to respond to the external input by not overwriting at least a portion of the first data after the predetermined time.

By virtue of the algorithm, preferably the data which is written to the temporary data storage means is capable of being re-processed and played back on a video monitor so that the surveyed event may be viewed or reviewed in a forwards or reverse sequence.

If desired an auxiliary data recording device is provided, the data recorder including a port to which the auxiliary data recording device is =1 47, connectable, the method comprising connecting the auxiliary data recording device to the port of the data recorder and copying the data from the temporary data storage means onto a pernianent data storage means, such as a writable CD 0 zl ROM or other permanent data storage devlqe. A CD ROM and the like is inherently unable to be tampered xvith subsequent to the data being recorded and thus provided in an irrefutable forinat, a record of surveyed events. As such the CD ROM or other permanent storage means may thus be used as evidence in a court of law.

In an alternative arrangement, the data may be transmitted from the data recorder to the auxiliary data recording device e.g. over a transmission or network.

In one embodiment, in order to view a recorded event, an ancillary video monitor may be temporarily connected to the data recorder and the data stored on the temporary data storage means accessed and re-processed for display on ancillai-y video monitor. Alternatively or additionally, the data may be remotely accessed e.g. on a remote computer, from the permanent data storage means or a copy thereof, re-processed and displayed on a remote video monitor.

In another embodiment the system includes a video monitor and is characterised in that the method comprises viewing an event being surveyed in real time on the monitor, and accessing the stored data of the temporary data storage means to review a previously surveyed event.

In each embodiment, in order to provide additional security against the data being tampered with, preferably the method includes storing time information relevant to surveyed events with the compressed data and/or frame identification information.

According to a second aspect of the invention we provide a surveillance system adapted for operation according to the method of the first aspect of the invention.

Preferably the algorithm is provided on a ROM device of the data recorder but may be provided in software on a hard disc of the data recorder.

So that the data recorder may be used in environments which present a risk to the components of the data recorder, preferably the data recorder comprises a substantially hermetically sealed housing in which the temporary data storage means, the processor means, and where provided the ROM device, 0 are housed. The housing may include external formations which act as a heat sink to dissipate heat generated within the housing.

Within the housing there may be provided at least one of - C> 6 a fan means for circulating the air to enhance heat dissipation; a power stabilising means for stabilising the power supply to the components of the data recorder thus to protect the data recorder against power surges and the like; anti vibration mounting means for the processor means and the temporary data storage means at least; According to a third aspect of the invention we provide a method of providing evidence of an event comprising performing the method of the first aspect of the invention, and copying the data written to the temporary data storacle means on a permanent data storage means, and re- processing the data to provide a video signal to a video monitor.

The invention will now be described with reference to the accompanying drawings in which:- FIGURE 1 is a diagrammatic view of a first surveillance system which may be operated by the method of the invention; and FIGURE 2 is a diagrammatic view of a second surveillance system which may be operated by the method of the invention.

Referring first to figure 1 there is shown a surveillance system 10 which in this example is intended for use in a train or other vehicle. The system includes a video imaging means 11 which in this example is a standard CCTV camera. The camera 11 produces a video signal of an event to be recorded, which is sent down a line 12. The position of the video camera 11 in relation to a surveyed area may be fixed, or may change automatically e.g. under computer control, and/or the position of the camera 11 may be manipulated from a remote location to look in certain directions.

In each case, the line 12 is connected to a data recorder 14 which may be mounted in a compartment of the train or other vehicle in which the system 10 is installed, or under a scat for examples only.

7 Where the data recorder 14 is provided in an environment which provides a risk of damage to components of the recorder 14, such as a hot/cold/polluted/dusty environment, preferably the recorder 14 includes a substantial hermetically sealed housing 15. To provide for dissipation of heat generated in the data recorder 14, the housing 15 may include external formations 16 which act as a heat sink. Within the housing 15, there may be provided a fan 17 and/or heat sinks to cause circulation of air within the housing 15 to assist the dissipation of heat.

The data recorder 14 includes a processor means 18 which processes the video ignal from the camera 11, and writes information directly to a temporary data storage means 19 of the recorder 14. The processor means 18 processes the video signal using an algorithm provided on a ROM device 20, to produce compressed data. The data thus stored may be re-processed to produce a video signal which may subsequently be viewed as hereinafter explained.

Additionally, the video signal fi-orn the camera 11 may be buffered in RAM of the data recorder 14, for example the last 5 minutes recording may be so buffered if the RAM is suitably large.

The processor means 18, fan and/or heat sinks 17 and ancillary stabilised power supply componentry, the data storage means 19, the ROM device 20 and other components of the data recorder 14 may each be mounted on antivibration mountings 21 for robustness.

The processor means 18 is adapted to process the video signal from the camera 12 and write two alternative sets of data to the temporary data storage means 19. First, the processor means 18 may produce first compressed data which is able to be re-processed and played back on a video monitor at a first real time fi-ame rate, and second compressed data which is able to be reprocessed and played back on a video monitor at a second, slower, real time fi-ame rate.

8 Thus the second data may be less complete than the first data. For example, the fast frame rate may be substantially the maximum number of frames of image per time unit which the camera 11 is capable of producing, and the slower frame rate may omit at least some.of the frames of image produced by the camera 11.

Thus a video image from the first data is capable of being viewed to provi& the maximum information of an event under surveillance, and would be the desired data to store of a significant event, e.g. of a criminal action. A video image of no significant event may not require to be stored for any future viewing, but may much later be found to contain information relating to a significant event, and this may be stored as second, less complete data.

Thus to optimise use of the temporary data storage means 19 preferably the processor means 18 is adapted to overwrite the first data after a predetermined time, In the s-ystem 10 of figure 1, it will be appreciated that there is no real time human monitoring of the video signal provided by the camera 11. Thus the C> time before which the first data may be overwritten may be relatively long, and could for example be an entire journey time of the vehicle. Thus in the event that no significant events are perceived during the journey by the train t j guard/driver for examples, the first data may be over-written during the next journey, or journey pail, whilst the second data remains stored.

However in the event that a significant event is perceived, such as an act of vandalism or the unauthorised use of an emergency system of the vehicle, the processor means 18 may be provided with a signal which will inhibit the o-,.,ei-writin(, of at least first data relating to such a significant event..

Such signal may be provided manually by a guard providing an input along a signal line 23) from a guard station for example when a suspected act of vandalism is seen or heard, or may be provided automatically along line 23 in response to the operation of an emergoency stop control 24 or similar. The Z:> 9 surveillance system 10 could be adapted to respond to other events such as the tampering or opening of a door, an unusual noise, or even, where the system includes an image recognition function, the automatic recognition of a person or event.

In each case because only limited first data, which will require substantially more memory than the second data, is stored without being overwritten, there is optimum use of the storage capability of the system 10.

Although the system 10 shown does not have an integral video monitor which would allow the real time viewing of the signal from the camera 11, the data recorder 14 is adapted to be connected to a video monitor 26. Typically this could comprise a hand held device for example useable by train staff on a train to identify the perpetrator of a significant event. For example in the event that a train in which the system 10 is provided is stopped by the unauthonsed operation of emergency stop control 24, the guard or other security personnel, may connect the hand held monitor 26 to the-data recorder, e.g. via a plug 27 and socket 30 connection, and operate a keypad 31 or the like of the hand held monitor 26 to view the event as recorded by the data recorder 14.

The hand held monitor 26 may have an integral data storage device 32 comprising in this example a device for writing to CD Rom storage medium 3)3) or another permanent data storage means, or a separate permanent data storage device may be used, so that a permanent copy of the data or selected data stored on the temporary data storage means 19 of the data recorder 14 may be made which would be acceptable as evidence of a recorded event in a court of law.

Of course once a permanent record of compressed data on the temporary data storage means 17 of the recorder 14 has been made, all that temporarily recorded data may then be overwritten to permit of repeated use of the temporary data storage means 17.

Further features of the system 10 are as follows.

A power supply will be required for the recorder 14. Although this could comprise a battery supply, which may be rechargeable, such power supply may be obtained from the power supply from the train or other vehicle. In this latter case, some power stabilising means may be required to protect the recorder 14 from power surges and the like.

If desired, instead of there being a single camera 11 to provide a single input to the data recorder 14, a plurality of cameras such as camera 11 may be used, each providing an input to the data recorder 14, and the data recorder 14 processing and storing as compressed data, information fi-om the video signals from all of the cameras 11.

Although it is envisaged that no video monitor would be integrally provided with the system 10 so far described for real time monitoring of the output for the camera 11, if desired at a security station of the train or other vehicle such a monitor could be provided.

In accordance with the algorithm provided on ROM device 20, the processor means 18 may analyse each frame received fl-om the video camera 1, and distinguish pails of the image which have changed since the last image 0 C.) frame from pails of the image which have not changed. Thus the image c Z:5 C information may be compressed by storing only information about the image C) frame which has changed since the preceding image frame, although the W -- c C1 omitted information will need to be made available so that a complete image frame may be viewed when required. Such an algorithm thus enables information about a surveyed event to be more reliably stored than with known video compression algorithms. However other kinds of algorithm to that described may be utilised to process the image information from the camera 11.

1 C Preferably, though, the algorithm used is able to store for each or substantially 0 each frame of image, time information e.g. the time of day when the image was C1 viewed, and an individual frame identification, to minimise the risk of the data being tampered with, and where multiple cameras 11 are used, the number of c the camera for example per other identifier. Such information may be provided on the top line of each frame.

Referring now to figure 2, an alternative surveillance system 40 is diagrammatically shown. Like with the system 10 of figure 1 there is a video camera 11 although again another kind of video imaging means may alternatively be provided, and a data recorder 14a, although data recorder 14a may be an adapted computer rather than an especially constructed item, like data recorder 14 of the figure 1 system.

The video signal from the camera 11 passes to the data recorder 14a along a line 12a, and also is provided to a real time video monitor 41 from a line 4 1 a fl-om the recorder 14a. The system 40 is intended for use for example for the monitoring of motorways or other roads or crowds, by, the police, in real time, and for recording surveyed events.

In this example the position, magnification etc. of the camera 11 may be controlled by an operative sending signals to the camera 11 along line 12a or another line, or even by wireless link, and the operator may thus observe a selected area with the camera 11.

The data recorder 14a is similar to the data recorder 14 of the figure 1 embodiment, but where the recorder 14a is not mounted where it will be subjected in use to vibration and other hostile environmental factors, no special mountings such as mountings 21 in the recorder 14 of figure 1 for the components of the recorder 14a are necessary. Also, the housing 15athereof need not be hermetically sealed.

However, like the recorder 14 of the figure 1 systern, the recorder 14a may include a processor means which processes the video siggnal from the camera 11 in accordance with an algorithm provided on a ROM device, so that first complete, and second less complete, compressed data relating to the surveyed event may be stored, with the first data being, overwritten after a predetermined time, and the video signal may be buffered in RANI.

12 It can be seen in figure 2 that the system 40 includes an operator input device.42 e.g. a keyboard. The input device 42 may be used not only to enable an operator to control the camera 11, but also to enable the operator instantly to review a recorded event. For example, the input device 42 may enable an operator readily to review the past few seconds of records of a surveyed event, for example by pressing a single key, so that the operator can check the nature of an event the operator believes he saw. This may be achieved by retrieving the video information from RAM of the recorder l4a or the video inforination may be retrieved from the temporary data storage means.

Convenient retrieval of information is inherent with a computer storage type system in which image information rather than being stored on a tape, is stored digitally on a temporary data storage medium such as a hard disc, which can be randomly accessed and/or in a RAM device.

Whenever a video information is required to be replayed from the compressed data stored on the temporary data storage means, the processor means of the recorder 14a will need to re-process stored compressed data according to the algoritlim, and to store the re-processed data in RAM for C) C) playback through the monitor 4 1.

The input device 42 may also be used by the operator to provide an input to the recorder 14a to prevent the automatic overwriting of first data after a predetermined time. For example upon the giving of a command to the recorder 14a, first data relevant to a predetermined time period either side of a significant event, e.g. five minutes either side of a motor accident being surveyed, may be protected from being overwritten.

Like with the system 10 of figure 1, there are provided means whereby a permanent record of data stored on the temporary data storage means of the recorder 14a, may be made, which again may comprise a writable CD ROM device 44. This may be integral with the data recorder 14a as shown, or may be separate therefrom.

13 Again, the system 40 may comprise more than one video imaging means 11, and may comprise more than a single monitor 41 so that the video signals from one or more cameras 11 may be simultaneously viewed by more than one operator.

Although any one of a number of different algorithms may be used to process the video image information, preferably the algorithm used is of a specialised nature to reduce the possibility of tampering with the stored information In another an-angement, instead of the algorithm being provided on a ROM device, this may be provided in software, e.g. on a hard disc of the data recorder.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific

C forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

14 CLAIMS

1. A method of operating a surveillance system comprising a video imaging means, and a data recorder, the data recorder comprising a temporary data storage means which permits of random access to the data stored thereon, and a procesor means, the method including processing a video signal provided by the video imaging means, of an event being surveyed, according to an algorithm, to produce compressed data and writing the compressed data to the temporary data storage means.

2. A method according, to claim I characterised in that the method includes processing the video sional of an event bein,(,, surveyed with the processor to produce first compressed data which is able to be reprocessed and played back on a video monitor at a first real time frame rate, and second compressed data which is able to be re-processed and played back on a video monitor at a second, slower, real time frame rate, the processor means being adapted to write the first and the second data to the temporary data storage means, and to overwrite the first data after a predetermined time.

A method according to claim 2 characterised in that the data recorder C has means to provide an external input to the processor means, and the processor means is adapted to respond to the external input by not overwriting at least a portion of the first data after the predetermined time.

4. A method according to claim I oi- clairn 2 or claim 33 characterised in that by virtue of the algorithm, the data which is written to the temporary data storage means is capable of being re-processed and played back on a video monitor so that the surveyed event may be viewed or reviewed in a forwards or reverse sequence.

5. A method according to any one of the preceding claims characterised in that there is provided an auxiliary data recording device, the data recorder including a port to which the auxiliary data recording device is connectable, the method comprising connecting the auxiliary data recording device to the port of the data recorder and copying the data from the temporary data storage means onto a permanent data storage means.

6. A method according to claim 5 characterised in that to view a recorded event, an auxiliary video monitor is temporarily connected to the data recorder and the data stored on the temporary data storage means is accessed and reprocessed for display on the auxiliary video monitor, or the data is remotely accessed from the permanent data storage means or a copy thereof, reprocessed and displayed on a remote video monitor.

7. A method according to any one of the preceding claims wherein the system includes a video monitor and characterised in that the method comprises viewing an event being surveyed in real time on the monitor, and accessing the stored data on the temporary data storage'rneans to review a previously surveyed event.

8. A method according to any one of the preceding claims which includes storing time information relevant to surveyed events with the compressed data.

9. A method of operating a surveillance system substantially as hereinbefore described with reference to the accompanying drawings.

10. A surveillance system adapted for operation accoi.din,(,,, to the method of any one of the preceding claims.

16

11. A system according to claim 10 characterised in that the algorithm is provided on a ROM device of the data recorder.

12. A system according to claim 10 or claim 11 characterised in that the data 0 recorder comprises a substantially hermetically sealed housing in which the c temporary data storage means, the processor means, and where provided the ROM device, are housed, the housing including external formations which act C as a heat sink to dissipate heat generated within the housing.

13. A system according to claim 12 characierised in that within the housing there is provided at least one of.a fan means for circulating the air. a power stabilising means for stabilising the power supply, to the components of the data recorder, anti vibration mounting means for the processor means and the temporary data storage means at least; Z 1

14. A system substantially, as hereinbefore described with reference to and as shown in the accompanying drawings.

1 c, c

15. A method of providing evidence of an event comprising performing the method of any one of claims 1 to 9 and copying the data written to the temporary data storage means on a permanent data storaee means, and re- W) processing, the data to provide a video signal to a video monitor.

c

16. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings C c