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Editor's Blog and Industry Comments

H.264 compression fever at IFSEC

19 May, 2008
A significant change in the 12 months since the last IFSEC exhibition was the offering en masse of H.264 compression capabilities and HDTV monitoring
H.264 isn't a new standard and has been around in a number of forms for many years but the last twelve months has seen a frenzy of activity in the surveillance industry to offer it as the latest video compression standard.

In its raw form, video footage requires large amounts of bandwidth and memory to transmit and store it so compression standards were developed to enable larger files to be used with reduced overhead. The simplest compression technology involves simply removing redundant information which doesn't reduce image quality but compression ratios of any significance couldn't be achieved with this alone. An example of this kind of compression is a static file archiving programme like Winzip. If you zip a word file, the file size reduces significantly but if you try and reduce a video file, there is virtually no compression.

Usable video compression is therefore achieved using complex mathematical algorithms that interpolate data between video frames, thus removing real content prior to storage or transmission and then reconstructing it using a decoding algorithm for displaying. The quality of the reconstruction therefore relates to how much material is used and the mechanism for reconstruction. Consequently, there are some big trade-offs involved.

Two principal bodies have been involved in the development of compression technologies over recent years, the International Telecommunications Union (ITU) responsible for the H.26x formats and the International Standards Organisation (ISO) responsible for the familiar MPEG formats. The original H.264 compression format was used in such applications as video conferencing for a number of years but the two organisations (ITU and ISO) worked together in the early part of the decade to come up with H.264/AVC which is now considered sufficiently developed for use in surveillance applications.

The use of the standard has come about for two main reasons, the first being the requirement for improved bandwidth usage for IP video and the second being the demand for HDTV monitoring. Imagine the impossible for a moment - plugging the latest megapixel camera directly into a large format high definition monitor without compression. This would represent the best achievable image quality but the worst case in terms of usefulness; the images aren't stored anywhere, can't be analysed, replayed or presented as evidence. The other option is taking a compression standard that doesn't support HD. In this case, all the defects inherent in the compression algorithm will be presented in all their glory.

At first sight, H.264 offers the best of both worlds providing Hi-Def support and almost double the compression achievable with MPEG4 but there are disadvantages. In order to achieve such compression levels, H.264 requires higher processing power to run the algorithm. With more edge analytics and image processing being performed by the camera, they are inevitably becoming more expensive with more on-board processing power. Another factor to consider is latency which is higher with H.264, although depending on the application this may not be of significance.

The CCTV manufacturers are pushing digital surveillance technology and there's no doubt that this is where the future lies. However, the vast majority of existing installations and new camera sales remain analogue. One reason for this is the perceived problems concerning bandwidth demands on crowded IP networks so by offering higher compression levels and hence lower bandwidth demands, the IP camera manufacturers can gain a foothold into a market that's proving difficult to penetrate.

H.264 offers another route into digital surveillance but choose carefully based on full information.
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