Everyone knows what HDTV means when it comes to home entertainment, but what about when HDTV is used in video surveillance? How does the HDTV technology stack up against Megapixel IP cameras?

 Market awareness and demand for highest pos­sible resolution is on the increase. The HDTV phenomenon is a case in point. Offering higher resolution than SD (SD = Standard Definition - the resolution that your old TV used to display), plus wider viewing that gives that movie theatre look on a wide screen TV. HD has become so popular that Blu-ray (HD) movies titles are outselling DVD (SD).

HDTV may be a hit with the mass consumer market, but is HDTV the best way to go for video surveillance? IP camera manufacturers backing HDTV are saying yes, but let's consider the facts.

HDTV&Megapixel - what's the difference?

A HDTV camera is a megapixel camera that is confined to the HDTV standard. Depending on the model, a HDTV camera produces between 1 to 2.1 megapixel resolution at up to 30fps (frames per second), with an aspect ratio of 16:9. Video is compressed using H.264. HDTV is restricted to a maximum resolution of 2.1 megapixel (1920x1080).

Well before HDTV cameras were released, mega­pixel camera technology has been delivering the same resolutions and wide screen format - they just weren't labeled "HD".

Megapixel cameras are not constrained by the HDTV resolution limitation. When recording above 2.1 megapixels, some cameras may not be able to match the HDTV frame rate, due to the in­creased processing load at the camera, however this is largely irrelevant as only a very small per­centage of sites require a recording speed of 30fps (frames per second). Most installations are setup to capture video at between 5fps - 20fps on event. Very few applications require higher recording frame rates.

Is HDTV better because it's a standard?

HDTV is a standard developed for the television industry; however the video requirements for surveillance applications are vastly dif­ferent than for home entertainment. When it comes to surveillance, captur­ing what is moving in the scene at the best possible image quality is most im­portant. The key problem with HDTV cameras is that H.264 is the codec used for video delivery. While it's true, H.264 is great for streaming High Definition video at low bit rates, there is a catch. H.264 applies very high com­pression to anything moving in the scene - thus captured in low­er resolution. It's a simple trick applied, that goes unnoticed by the human eye - but only while the video is streaming. When the video is paused and a still im­age extracted, for the purposes of identifying a moving person or object, it lacks detail. That's the nature of H.264. But this makes sense because it was only designed for streaming movies - not for examining what is mov­ing in high detail, or pausing and extracting stills as is required in a surveillance application. (Article: Video codec made for surveillance)

Does HDTV offer the best image quality?

When it comes to image quality HDTV does not offer any special capabilities over megapixel tech­nology, and it's capped at 2.1 megapixels. As a comparison, a MOBOTIX 3.1 megapixel camera produces 51% higher image resolution than a HDTV IP camera, and captures a much greater viewing area than the HD format.

Which is best - 16:9 or 4:3 aspect ratio?

Capturing the critical areas of a scene in the high­est possible image quality should always be given top priority. Megapixel cameras with clipping functionality allows users to create any sized as­pect ratio required, meaning they can pre-define any area from within the camera's field of view. Once the unwanted parts of the scene have been clipped out, the camera will produce video ac­cording to the preselected size and ratio. This is particularly useful when you want to capture, stream and store only the area of interest within the scene. This in turn lowers the storage and

Bandwidth usage dramatically.

Another benefit to the clipping function is that the aspect ratio can be defined to suit any sized viewing monitor, therefore you're not confined to any one aspect ratio.  

Why so much hype around HDTV?

The term "HD" is little more than a marketing vehicle being aggressively used by IP camera manufacturers who know the mass market re­lates HD to highest image quality - but don't be fooled. While HDTV may represent best image quality for television, there are megapixel camera technologies available offering higher resolution and image quality than HD. Customers should examine different high resolution lP video products, seeing them in action to make an informed comparison.

Mike Davis

President

Davis Fire and Security