There has been significant debate in recent years about the CCTV market finally reaching the tipping point into IP technology as the common standard. However, in reality it’s only within the last 12 months that the emergence of megapixel camera technology has made this view possible. Many of the global camera manufacturers are now seriously pushing megapixel technology and have managed to make their products price competitive enough to warrant the inclusion of megapixel cameras in appropriate projects.

In this interview with Craig Howie of Visimetrics, we set out to uncover the implications of megapixel technology for the future of storage requirements, and the overall design of the CCTV surveillance solution of the (near) future.

By Vibeke Ulmann

“A fundamental issue of specifying megapixel cameras - and it could be argued IP systems generally - is that many do not fully appreciate the implications of the technology from a storage and bandwidth perspective. Camera manufacturers tend to focus on the camera in isolation rather than the effects of each cameras data output on the overall network and storage system. The underlying codec implementation within the camera, fixed or PTZ format, static or motion filled scenes all have a significant effect on the overall bandwidth and storage required. 
A crude but common historical approach to specify the recording capacity on DVR’s has been based on storage and channel count i.e. stating a 2TB, 16-channel hard disk recorder is required. While you could probably – just- get by in this way with analogue cameras the effects on moving the compression from the DVR to the IP camera increases the potential margin of error significantly. This makes the specifying of storage for each camera far more critical. By way of a fairly simple example the storage needs for continuous recording of 64 megapixel cameras at 4Mbps, 24hrs per day for 31 days is almost 96TB. Reduce the bit rate (i.e. quality while maintaining frame rate) from 4Mbps to 3Mbps takes the overall storage needed down from 96TB to 72TB! Clearly the specification of output per camera can make a huge difference – not least to the costs for what may seem a trivial difference in output.
Craig continues,” The adoption of megapixel technology can seem very confusing. Firstly the increasing number of manufacturers makes selecting the right camera(s) more complicated simply by choice. Secondly, you need to consider the individual bandwidth and storage needs for each camera. Generally, calm scenes with little activity require far less storage than scenes of constant activity. However, every manufacturer implements the compression technology independently. This is why you find cameras that appear identical on datasheets perform completely differently in practice. Unfortunately in many cases there seems to be a fair bit of ‘trial and error’ or field testing to actually determine how much storage capacity you really need under various conditions. When your system includes a lot of cameras with a long retention period then the technical risk of specifying the storage increases.”
Everyone appreciates that there is always a compromise between what you would like to have and what you can reasonably afford. If you want 31 day’s storage at the highest frame rate, quality and resolution then your storage system is going to have to be pretty large. So there is a compromise to be had, and it’s a question of understanding this compromise and in particular understanding camera compression and scene effects on the overall storage.

A constantly moving target
“Unfortunately, the influences on storage aren’t static! Storage requirements by day – under natural light – can vary significantly to those of night images for the same camera. Darkness introduces noise into the images, so digitising these with motion based compression algorithms produces much larger files. Scenes with lots of activity use far more storage than calm scenes.” Craig says.
The advice is to be very selective in which megapixel cameras you chose. Focus on a small subset of products to fully understand particular cameras and how they respond under various conditions. Be aware the implementation of compression algorithms i.e. MPEG4/H.264 etc. - is not the same from camera A to camera B. While the underlying tool box of codec type may be the same, the way in which it’s implemented by the manufacturers can be wildly different. This can result in significant variances in storage requirements.

A growing elephant in the room
Craig continues, “As I look at the current market its clear it will have to become more standardised for complete adoption to be reached. I’m sure it will over time. However the current status is still some way away and doesn’t look to be reaching the concept of plug and play anytime soon.”
The complexity of integrating IP systems looks to be leading to a future elephant in the room when it comes to support. Consider this in the context of sending an engineer to site where he determines the IP camera must be replaced. He has to ensure the replacement camera is compatible with the recording and management system software levels.  Potentially he could be looking at replacing the camera AND upgrading all recording/display systems to get to the status quo of viewing and recording the scene of the failed camera while ensuring all other elements of the system remain unaffected by the software changes! No small feat for a simple camera replacement.