HD Video Surveillance
are displayed with a 4:3 aspect ratio. As a result, supporting products are designed with this in mind, including camera chips, video displays, video management devices, etc.. HDTV differs, in that it follows prescribed standards (SMPTE 296M and SMPTE 274M being the most significant) which ensure delivery of higher resolutions at prescribed frame rates and aspect ratio. There are three main formats for HDTV. These encompass two resolutions: 1280 x 720 or 1920 x 1080 pixels. These resolutions are achieved via progressive scan, or can also be interlaced in the case of the latter resolution. This gives rise to the designations of HD720p for the lower resolution, and HD1080p or HD1080i in the case of the higher resolution: the ‘p’ and ‘i’ designation letting you know the scan type. HDTV must be delivered in real-time. Under
the PAL standard this is 25 frames per second. This frame rates must be achieved as a minimum by HD equipment, and it is not uncommon to see designations such as HD1080p30, indicating the camera’s frame rate. HD1080p video is often referred to as ‘Full
HD’. This has it roots in consumer sector marketing, and is biased towards making the public buy the highest specification model! Whilst the term isn’t incorrect, as it does identify the highest spec, it should in no way be considered to imply that HD1080i or HD720p isn’t genuine HDTV equipment. With regard to aspect ratio, HDTV images
are 16:9 ratio, whereas traditional composite CCTV is 4:3. This can lead to confusion - some not intended and some designed to shift product - as the term ‘HD quality’ has started to appear in order to imply that 4:3 products share the resolution of HD alternatives. This will be addressed in more detail later in the guide, but for now it is sufficient to state that products that carry the HD logo must meet the standards.
One significant issue that the video
surveillance industry faces is the misunderstanding about what is and what isn’t HDTV. The consumer world is pretty well
policed, but the security industry uses the technology involved in a slightly different way. However, if products, systems and solutions are labelled as HD, then they should be standards-compliant HD.
The fact that the security industry can utilise HD technology has come about because of changes in infrastructure. Moving away from PAL has allowed higher resolutions to be achieved, and this has allowed the introduction of HD and megapixel technologies. HD and megapixel are often mentioned in the same breath, and there have even been statements from alleged experts pointing out that: ‘all HD cameras are megapixel, but not all megapixel cameras are HD’. Of course, this statement is wrong as the resolution of HD720p is below one megapixel, but the sentiment is worth acknowledging!
Significantly different
As already pointed out, when you look at a HD designation there are a lot of things that you already know. For example, if a device is HD1080p, you know a number of things for certain. You know that the device is high definition and meets the relevant standards, and so the image should be compatible with other HD devices. You know that the image resolution is 1920 x 1080 pixels, you know that the image is progressive scan, and you know that the device is capable of handling real- time video. Taking the same attitude with a megapixel
camera, what does the specification tell you? Well, if the camera is a 1.3 megapixel unit, or a 5 megapixel unit, or indeed whatever value is stated, all you really know is that the image will consist of that many pixels. Therefore, the only certainty you have with a 1.3 megapixel camera is that the image will contain approximately 1.3 million pixels. Megapixel is an image size; the designation
tells you nothing about frame rate or aspect ratio. Additionally, there is no defined benchmark for the specification, so you could effectively put a number of 1.3 megapixel cameras side-by-side - as Benchmark has
www.benchmarkmagazine.com 9
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60