GB2406454A

GB2406454A - Transceiver controlling flow of digital video data to analogue transmission line

Info

Publication number: GB2406454A
Application number: GB0322433A
Authority: GB
Inventors: John Alan Douglass
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-09-25
Filing date: 2003-09-25
Publication date: 2005-03-30
Anticipated expiration: 2023-09-25
Also published as: GB0322433D0; GB2406454B

Abstract

A transceiver interface unit (204) for a closed circuit video monitoring system (200) including analogue video cameras (202) and digital video cameras (203), data routeing equipment (208), a CCTV computer (210) and a screen (212), includes a processor which controls the flow of digital data and an output which is impedance matched to an analogue co-axial cable (205), which is used to carry the digital video signal to other transceivers that in turn connect to data routeing equipment (208) to form a bridge between the analogue transmission lines and the network at large. The data routeing equipment (208) combines the digital video signal with at least one other digital video signal and outputs the digital video signal to the CCTV (210) computer and the screen (212).

Description

CLOSED CIRCUIT VIDEO SYSTEM

This invention relates to a closed circuit video system and a transceiver unit. More particularly, but not exclusively, the invention relates to a closed circuit video system comprising at least one video camera and a transceiver unit arranged to facilitate the transmission of digitised video signals along existing analogue co-axial video cabling.

A Closed Circuit Television (CCTV) system, whether digital or analogue, typically comprises a number of CCTV cameras connected to a multiplexer or monitor. Each camera is connected to the recording or monitoring equipment via a single dedicated video cable. The capacity of the analogue video cable is therefore restricted to carrying a signal from a single camera.

Modern digital video cameras, such as internet protocol (IP) addressable or network cameras, can achieve much greater channel capacity by compression of the video signal through well known techniques such as joint photographic experts group (JPEG) and motion picture experts group (MPEG) algorithms and transmitting the digital video through conventional information technology (IT) network cabling. Depending on the network speed and compression ratio the transmission capacity can be increased typically by 10 or 20 times, compared to traditional analogue video cable transmission. Thus, one cable can be used to carry many video signals.

However, part of the reluctance of users to adopt the new IP addressable digital cameras is the requirement to use different cabling, such as CAT5. This reluctance is coupled with the problems of integrating high data rate digital video cameras with standard IT networks, many of which are already overstretched in terms of capacity. Generally, IP cameras have limited bandwidth control and there is no guarantee that either the associated viewing software or the users will have adequate control to prevent the network from becoming flooded with CCTV video data.

Furthermore, there is little scope for users to integrate traditional analogue cameras with new IP addressable cameras since the signals and transmission cabling are incompatible.

In many instances users resort to installing a separate network to carry the digital CCTV video. Even if the existing IT network can be used, there will normally be a requirement to install new cabling between the digital cameras and the nearest network connection point. Installation of video cabling is an expensive labour intensive task often involving civil works, which frequently account for more than 50o of the cost of a new CCTV system.

According to a first aspect of the present invention there is provided a transceiver unit suitable for connecting to a video camera comprising an input, an output and a processor, wherein the input is arranged to receive video data corresponding to a scene captured by the video camera, the output is arranged to be impedance matched to an analogue video transmission line, and the processor is arranged to control the flow of digital data through the transceiver unit and to transmit the digital data over the analogue video transmission line, thereby enabling the analogue transmission line to form part of a digital network.

It will be appreciated that although reference is made to a single data input there may be multiple data inputs to the transceiver unit.

Furthermore, it is possible to connect both IP addressable cameras and traditional analogue cameras to the same network via the transceiver unit, enabling both standard analogue cameras and new IP addressable cameras to co-exist along the same cabling structure. This eliminates the need to provide separate cabling for the two types of camera.

Such a transceiver unit also enables other digital networks to interface with existing analogue transmission lines, by forming a bridge between the existing IT network and the analogue transmission lines, allowing digital CCTV data to be selectively routed to other parts of the wider network.

The overall benefit of the transceiver unit is that users can utilise their existing analogue transmission lines as a digital network, offering the increased capacity and versatility of a dedicated digital network, without the problems and costs associated with re-cabling.

In addition users could utilise the resulting digital network for the transmission of other related digital data, such as access control data.

As a further enhancement, by controlling the video transmission rates through digital techniques the effective bandwidth could be significantly increased to possibly 30 or 40 cameras. To illustrate this, using the concept of foreground and background transmission rates, video from cameras on general surveillance could transmit at 1 frame per second, but cameras on alert could transmit at 25 frames per second. Thus cameras on background transmission require less than one twentieth of the bandwidth of active cameras, enabling a large number of cameras to share the same analogue transmission line which would previously not be possible.

The output may be arranged to connect to a co-axial cable, for example RG59 cable. The output may have characteristic impedance close to 75Q.

The input may be arranged to connect directly to a digital video camera.

The digital video camera may be an IP addressable video camera. The input may be an RJ45 or other suitable industry standard network connector.

The input may be arranged to connect directly to an analogue video camera. The transceiver may include an analogue to digital video converter (ADC) arranged to convert an analogue video signal to a digital video signal. The input may comprise a BNC or similar type of connector.

The processor may be arranged to control the flow of data by means of a suitable data control protocol, for example the TCP/IP protocol. The processor may be arranged to compress the digital data. Typically, the processor is arranged to compress the digital data by means of an MPEG- 4 compression routine, JPEG or any other suitable video compression routine.

The compression of the digital data reduces output signal bandwidth making the compressed signal suitable for continuous video streaming.

The processor may be arranged to encrypt at least the intra (I) frames of the compressed digital data by use of a selective encryption algorithm.

The processor may be arranged to encrypt a header of both, or either of the predicted (P) and/or bi-directional (B) frames of the compressed digital data. The processor may be arranged to compress and/or encrypt the digital data in real time.

The use of encryption provides added security and reduces the opportunity for interception and alteration of data.

According to a second aspect of the present invention there is provided a closed circuit video monitoring system comprising a video camera fitted with a first transceiver unit according to the first aspect of the present invention, a viewing means and/or a recording means; the video camera being arranged to capture real time video images of a scene; the first transceiver unit being arranged to receive a video signal from the video camera and output a digitised video signal over an analogue transmission line to either, or both, of the viewing means or/and the recording means via a second transceiver unit.

There may be a data routeing means between the transceiver and either, or both, of the viewing means or/and the recording means.

The data routeing means may be arranged to combine said digitised video signal with at least one other digital video signal and to output a combined digital video signal to either, or both, of the viewing means or/and the recording means.

The data routeing means may be arranged to combine said digital video signal with at least one other digital video signal such that at least some of the component video signals are viewable and/or recordable. At least some of the component video signals may be viewable and/or recordable substantially simultaneously.

The data routeing means may be any one, or combination of the following: a network switch, a hub any other suitable data routeing means.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which; Figure 1 is a schematic diagram of an embodiment of a closed circuit video monitoring system of the prior art; and Figure 2 is a schematic diagram of an embodiment of a closed circuit video monitoring system according to an aspect of the present invention incorporating a transceiver unit according to another aspect of the present invention and a video camera.

Referring now to Figure 1, a typical analogue closed circuit video monitoring system 100 comprises a plurality of analogue video cameras 102, a video recorder 104, a multiplexer 106 and a display screen 108.

Each of the video cameras 102 captures real time analogue video signals comprising images of their respective viewed scenes and passes each of these signals down a respective co-axial, RG59, transmission line 110, to the multiplexer 106. Thus, there must be as many transmission lines 110 as there are video cameras 102, with each transmission line 110 being dedicated to a single video camera 102.

A multiplexer 106 combines the analogue video signals by sequentially interleaving them to produce a multiplexed signal. In a sixteen camera system each camera is sampled, typically once every second or thereabouts.

The multiplexed signal is passed to the video recorder 104 where it is stored. The video recorder 104 may be either an analogue video cassette recorder or a digital video recorder, for example a magnetic hard disc drive or a DVD drive. The multiplexed signal is then passed to the display screen 108 where it is output in the form of a series of time lapse images of the respective viewed scenes for viewing by a user of the system, typically a security guard.

Referring now to Figure 2, a CCTV monitoring system 200 according to the present invention comprises a mixture of analogue video cameras 202 and IP addressable digital video cameras 203, each having a transceiver unit 204 associated therewith, analogue co-axial transmission lines 205, a data router 208, a computer 210 and a monitoring screen 212. The data router 208 is typically a network switch, hub or any other data routing equipment.

The analogue video cameras 202 capture analogue video images of respective viewed scenes. Each analogue video camera 202 is connected to a respective transceiver unit 204 via a standard BNC connection 213.

The analogue video signals received at the inputs to the respective transceiver units 204 are passed to respective analogue to digital converters (ADC) 214. The ADC's 214 convert the analogue video signals to digital video signals and pass them to a processor 216 within each of the transceiver units 204.

The digital video cameras 203 capture digitised images of respective viewed scenes and produce digital video signals, which are passed to the transceiver units via a short length of CAT-5 or similar cabling 218. The digital video signals are input to the transceiver interfaces 204 via suitable connectors such as RJ45 connectors 220. The digitised video signals are passed to the processor 216 within the respective transceiver unit 204.

The processors 216 manage the flow of data traffic through the transceiver units 204. The processors 216 also compress and or encrypt the video data received from the analogue cameras using MPEG-4 or JPEG compression routines or another suitable compression routine.

Digital data received via digital cameras is generally already compressed, but can, additionally, be encrypted by the transceiver unit processor, as can the digitised data originating from the analogue video cameras. It is envisaged that a bespoke compression routine peculiar to the system may be used. The use of a bespoke compression routine increases data security as it results in the generation of a proprietary compressed digital video signal, requiring a proprietary decoder algorithm, available only to an authorised user of the system. In addition to compressing the data the processors 216 may also be arranged to encrypt some or all of the frames of the compressed data. For example, in the case of MPEG-4 compressed data - the header of the intra (I) frames can be encrypted as can either, or both, the headers of the predicted (P) and bi-directional (B) frames, to give increased security against hacking or tampering with the digitised video signals.

Once the digital video signals have been processed by the respective processors 216 they are passed to respective transceiver unit outputs 222.

These transceiver unit outputs 222 are impedance matched to the analogue co-axial transmission lines 205, typically at close to 75Q for an RG 59 co-axial cable. This allows pre-existing co-axial video cables to be used for the transmission of digitised video signals, carrying typically data at rates of up to, but not limited to, 10 Mbits per second. Each transmission line 205 may be terminated in a network terminator 223 in order to prevent ringing.

The digitised video signals from the transceiver unit outputs 222 are introduced into the co-axial transmission lines 205 via T-piece connectors 224. Thus, multiple digitised video signals can be carried along each of the analogue co-axial transmission lines 205. Previously the analogue co axial transmission lines 205 had been restricted to carrying only one analogue video signal. The digitised video signals pass along the analogue co-axial transmission lines 205 to transceivers 226 close to the network switcher or hub 208. These transceivers 226 receive the digitised video signals via a BNC or suitable connector 228 and output them via an industry standard network connector such as an RJ45 connector 230 to CAT5 or similar network cables 231, connected in this case to the data router 208.

The data router 208 shown is connected to the network via a number of RJ45 bi-directional data ports 232. Although shown as having five ports it will be appreciated that the data router 208 is not restricted to five.

The data router 208 is shown with one port connected to some other network, such as an IT network, thus forming a bridge between the CCTV network and the IT network at large. The system will typically have additional data storage and display devices attached at some point to the network thereto for storing and displaying the digital video data.

The computer 210 may be connected to any point on the network either via the data router 208 or via a transceiver 226 and is used to decrypt and decompress the digitised video signal for display. In this example, the computer is used to store the digitised video signals either on a magnetic hard disc 246 or on a DVD in a DVD-writer 248 for example, and also to control which of the digitised video signals is displayed upon the screen 212. The computer 210 can be configured to display the views from a single camera or multiple cameras and can allow replay of sections of video footage when required.

It is envisaged that processing of the video images is possible on the computer 210, for example sharpening of images, or other feature enhancement routines.

Additionally, it will be appreciated that although shown as having connections suitable for connecting to both analogue and digital video cameras, transceiver units may be produced having connections suitable for connecting to only analogue video cameras or digital video cameras.

It will be appreciated that although a network switcher or hub has been described as the industry standard data routing equipment, the digital data can be routed by other similar standard data routing equipment.

It will also be appreciated that the term input and output refers to the general flow of data, but each input or output may be capable of receiving or transmitting data.

Claims

1. A transceiver unit suitable for connecting to a video camera comprising the input, an output and a processor, wherein the input is arranged to receive video data corresponding to a scene captured by the video camera, the output is arranged to be impedance matched to an analogue video transmission line, and the processor is arranged to control the flow of digital data through the transceiver unit and to transmit the digital data over the analogue video transmission line, thereby enabling the analogue transmission line to form part of a digital network.

2. A unit according to Claim 1 wherein the output is arranged to connect to a co-axial cable.

3. A unit according to either of Claims 1 or 2 wherein the output has characteristic impedance close to 75Q.

4. A unit according to any preceding claim wherein the input is arranged to connect directly to a digital video camera.

5. A unit according to Claim 4 wherein the input is arranged to connect directly to an IF addressable digital video camera.

6. A unit according to any preceding claim wherein the input is an RJ45 connector or other suitable industry standard network connector.

7. A unit according to any one of Claims 1 to 3 wherein the input is arranged to connect directly to an analogue video signal.

8. A unit according to Claim 7 wherein the interface comprises an analogue to digital converter arranged to convert an analogue video signal to a digital video signal.

9. A unit according to either of Claims 7 or 8 wherein the input comprises a BNC connector, or similar connector type.

10. A unit according to any preceding claim wherein the processor is arranged to compress the digital video signal.

11. A unit according to any preceding claim wherein the processor is arranged to generate headers of individual frames of the compressed digital data that are of a proprietary format.

12. A unit according to any preceding claim wherein the processor is arranged to encrypt at least the intra (I) frames of the compressed digital data by use of a selective encryption algorithm.

13. A unit according to any preceding claim wherein the processor is arranged to encrypt a header of either, or both, of the predicted (P) and/or bi-directional (B) frames of the compressed digital data.

14. A closed circuit video monitoring system comprising a video camera fitted with a first transceiver unit according to any one of Claims 1 to 13, a viewing means or/and a recording means; the video camera being arranged to capture real time video images of a scene; the first transceiver unit being arranged to receive a video signal from the video camera and output a digitised video signal over an analogue transmission line to either, or both, of the viewing means or/and the recording means via a second transceiver unit.

15. A system according to Claim 14 comprising a data routeing means between the transceiver and either, or both, of the viewing means or/and the recording means.

16. A system according to Claim 15 wherein the data routeing means is arranged to combine said digitised video signal with at least one other digital video signal and to output a combined digital video signal to either, or both, of the viewing means or/and the recording means.

17. A system according to Claim 16 wherein the data routeing means is arranged to combine said digital video signal with at least one other digital video signal such that at least some of the component video signals are viewable and/or recordable.

18. A system according to either of Claims 16 or 17 wherein at least some of the component video signals are viewable and/or recordable substantially simultaneously.

19. A transceiver unit substantially as hereinbefore described with reference to Figure 2.

20. A closed circuit video monitoring system substantially as hereinbefore described with reference to Figure 2.