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Image optimisation

Compression techniques and your security system.

As performance on video surveillance technologies improves, so too does the demand for footage storage. With a 50-fold performance increase on IP cameras predicted for the next 10 years, this also means an increase in the size of the footage. Businesses will need to find ways in which footage and images can be stored more effectively and cost efficiently.

Compression offers a viable option without visible differences in the quality of the footage. These techniques have been so effective that we have seen compression of between 50% and as much as 95% achieved with no visible difference.

But with so many compression techniques – and several options available in each – choosing the best for varying business environments can be overwhelming. For video surveillance, we recommend three options: Motion Jpeg (MJPEG), MPEG and H.264.

So how does compression work? Generally it means that the original file is condensed by either decreasing the visual quality of the file as with MJPEG (but not so much that the visual impact affects the usability of the file).

However, other techniques like MPEG and H.264 can also be used to provide greater compression with very little reduction in image quality. If you can imagine a scene from a video clip containing three slides – the technique will take the first slide and ‘delete’ the objects in the following slides that do not change like a house, tree, car, etc. This means that the compressed file will only include new information from slides two and three and not duplicate information. However, if one slide is compromised it has a greater effect on the video clip, which is where MJPEG is more robust.

Used effectively these techniques will not only be a valuable complement to your video surveillance system but will also deliver substantial cost savings by extending the life cycle of your storage hardware.

For a more detailed list of techniques, readers can download this Axis white paper (http://www.axis.com/files/whitepaper/wp_videocompression_33085_en_0809_lo.pdf).

Roy Alves

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