| Today many security managers and business | | | | that require the highest possible frame-rates and |
| professionals are switching to digital options for their | | | | resolutions if you are to correctly identify problems. |
| CCTV. While this represents a slightly larger | | | | For these reasons, when purchasing a DVR it’s |
| investment, it also largely increases flexibility, quality | | | | highly important that you find out what compression |
| and efficiency through a variety of different options | | | | types it supports (sometimes referred to simply as |
| and functions. One of these options is the ability to | | | | ‘video formats’) and what the different |
| select which format to compress videos in. | | | | titles represent. |
| On your computer you may have downloaded a | | | | The two main types of compression format for |
| variety of videos; if you look at each of these by | | | | digital CCTV are ‘H.264 format’ and |
| right clicking on them and selecting | | | | ‘MPEG’ (AKA Motion JPEG, and by which is |
| ‘properties’, you will notice that some of | | | | usually meant MPEG2). The key thing to note here |
| them are different file types. These will vary from | | | | however, is that H.264 format is also known as |
| .WMV to .MPEG to .AVI and each has different | | | | MPEG4, meaning that it is in fact an updated version |
| properties. What this refers to is the videos’ | | | | of the alternate format. H.264 video compression |
| ‘compression type’. If you consider the size | | | | format therefore drastically reduces both the |
| (in terms of kilobites or megabites) that an image | | | | bandwidth and storage requirements of the files by |
| size takes up, you can imagine why it’s | | | | keeping them small while keeping the image quality |
| important that these images are somehow ‘cut | | | | high. Usually however this results in a lower ‘bit |
| down’ in order to save space when potentially | | | | rate’ for the video which means that fewer |
| millions of them are strung together to create a | | | | ‘bits’ of information are available per second, |
| video. This happens at the level of the code (the | | | | but the method of encoding ensures that these lost |
| language that the computer or video device reads), | | | | ‘bits’ are unnecessary (high frequencies for |
| but can be visible in the videos’ appearances as | | | | example). With an average set up with four cameras |
| washed out colours, lower resolutions, blurry edges | | | | at thirty frames per second and a resolution of 320 x |
| or fuzzy motion. The aim here is to find a | | | | 240 (with motion sensors), you can expect MPEG4 |
| satisfactory balance between viewing quality and file | | | | compression to provide 80 hours worth of footage |
| size – so that you can store as much information | | | | at 20-25 gigabites. |
| onto a hard drive or disk as possible without | | | | However unlike MP2, MP4 has no government |
| sacrificing too much detail. | | | | enforced standard and as such does not have |
| When recording with a DVR (digital video recorder), | | | | universal interchange across codecs of various |
| this works in much the same way and the videos | | | | designs. This means that MP2 is more flexible and |
| must be compressed when they’re saved. Only | | | | adaptable as well as having a higher bit rate giving it |
| in cases of CCTV, compression type is far more | | | | its own unique advantages. Fortunately however, |
| crucial as you’re not only dealing with larger | | | | today most cameras support both formats and even |
| quantities of footage (sometimes hours’ and | | | | where they do not file conversion is often available. |
| hours’ worth) but also with delicate situations | | | | |