A beginner's guide
Last month we explained how cameras and servers in IP networks differ from traditional cameras – instead of producing an analogue TV image and signal, they produce a digital image and signal.

A digital image in itself is not startling – it can be of better resolution than an analogue image, or may be deliberately of lower resolution, depen-ding on the purpose – but the quality of the image is not where the huge benefits of IP lie. These benefits stem from the fact that the image is being carried over an IP network, and that digital images can be used in ways that analogue images cannot.

Because an IP network is being used, the CCTV images can be transmitted to almost anywhere in the world, starting in the local private network, and then if required into wider private networks and beyond into world-wide public networks, including the Internet. Contrast this with the limited distribution of a typical CCTV network, and the cost of extending such a network.

The other major benefit of an image being in digital format – that is, in a format easily recognised by computers – is that it can be processed in a number of different ways. It is these processing options plus other management functions, and the software that carries them out, that is the subject of our article this month.

The software functions fall into five basic categories:

  • camera control and picture mixing
  • digital signal processing
  • alarm handling
  • recording, archiving, and searching
  • scheduling and management.

But before we explain each of these features, it is worth talking a little more about the term "software", because it is not a term that appears in analogue systems, and is therefore one of the important new ideas for installers to understand as they develop their skills in the area of IP.

Software is another name for a computer program. It needs a processor (computer) on which to run, which may either be a general purpose PC, or a purpose designed chip located in a camera, server, or other device. Common examples of software include common PC packages such as word processors or web browsers like Internet Explorer, operating systems such as Windows, or the logic in the controller of a washing machine.

Some CCTV IP software is delivered on a CD, loaded onto a PC or server, and has the advantage that it can be upgraded as more advanced versions come along with minimal effort simply by loading from the new CD (although often with a charge by the software supplier). Software that runs in embedded chips, for example in cameras, cannot usually be upgraded in this simple way after installation.

The benefit of software is that it can undertake routine tasks that in traditional systems were carried out by people, and it completes them in an extremely reliable fashion. Software can scrutinise images in the minutest detail across any number of cameras. It can switch any part of the system on or off at exactly the time required. It can handle alarms according to precise rules. It can search recordings and find the images of interest in a fraction of the time it takes on a VCR. As we all know, computers and their software packages lack judgement, but they are excellent at following complicated rules in detail.

  • Camera control and viewing
    With an IP system, the control of the cameras all takes place through the browser-like screen of the control software. In some ways, this is similar to the way images are viewed in a control room in a traditional system. But there are two important differences.

    The first is that IP software provides a greater range and depth of functions than traditional systems. The second is that the location of viewing and control is much more flexible with an IP system. In a traditional system, the location is determined by the physical location of the control devices, their monitors, and the cabling. In IP systems, the location of control can be moved easily around the network within the location, and can also be located at a remote site anywhere in the world, subject of course to organisational constraints.

    The scope of software is clearly very wide and is further broadened by the ability to develop bespoke systems ... although such developments are best left to the experts

    The functions of the software for camera control and viewing include:

    • PTZ control – the software controls Pan/Tilt/Zoom units in the normal way, although using screen buttons and a mouse rather than physical devices
    • picture mixing – simultaneous display of multiple cameras looks like a standard multiplexer. However, the mixing and sizing of pictures is more sophisticated, and more pictures can be viewed simultaneously (up to 25)
    • instant recording playback – a feature that VCRs cannot offer is instant playback; computers can simultaneously record and playback, so an incident on a camera can be reviewed immediately after it has happened without affecting in any way the continuity of recording, and of course without any physical handling of any storage media.

    Digital Signal Processing
    Digital signals can be examined in various ways using the power of computer software. This is called Digital Signal Processing, often shortened to DSP.

    The software can ask the questions that a person may want to ask - is there anything significant happening in this image? Have there been any changes since we last looked? Are any doors open that should be closed?

    The three features that digital signal processing most commonly detects are:

    • motion – a change in the image that appears in any part of the screen, indicating that something has moved. The area of the image that the software monitors for motion can be specified – particular parts of the image only, or the whole image.
    • colour change – as for motion detection this can be applied to all the image or defined parts, but colour change rather than motion is examined.
    • brightness change – watching out for lights or a torch being switched on, software can monitor the overall brightness of all or part of the image.

      When an alarm condition is triggered, the image on the monitor can be highlighted around the border to more easily highlight the image among others on the screen.

  • Alarm handling
    When the system has detected that a significant change has taken place in the image, there are a number of options available for taking action.

    These options fall under the headings of:

    • increased recording pre- and post-alarm
    • communicating the alarm to those who need to know.

    Pre- and post-alarm recording involves increasing the number of images recorded around the time of an alarm incident.

    Just like traditional systems, most digital CCTV systems are set up with time lapse recording, for exactly the same reason as for VCRs – recording all of the continuous feed would fill the recording capacity far too quickly. However with digital devices, unlike analogue, it is possible to increase the recording frequency of a particular camera after an alarm condition has been identified. It is also possible to record all the images for a pre-set time before the alarm condition occurred, because the system holds all images for a short period of time before recording some and discarding others.

    The recordings that relate to an alarm condition are flagged in the recorder so that they can be easily searched for later.

    At the same time as the image is being recorded, the software can use a number of ways to communicate the fact that an alarm has occurred.

    The actions taken can be set to differ according to the nature of the alarm, if required, so different alarm conditions will be communicated in different ways:

    • emails – the software can automatically send a pre-worded email stating that the alarm has occurred to a specified distribution list of people both within the organisation and outside – for example a security company, or the police
    • image attachments to emails – the email can include an attached file of images, usually an AVI (movie) file, showing the image stream around the immediate time of the incident
    • SMS – as well as emails, notification of an alarm can be sent to mobile phones by text message, network providing. The limitation on this is one of mobile phones rather than the software - at present not many mobile phones or service providers can handle an accompanying image, which is a very useful addition to the basic fact of an alarm.
    • interfacing to other systems – because CCTV IP systems are often using the same communications network as other systems, including Access Control and Fire Alarm, communication between the systems is relatively easy.

  • Recording, archiving and searching
    Recording, archiving, and searching can be a time-consuming chore with analogue systems and VCRs. All these activities require a staff member to be present, with the attendant costs and operational overheads.