The widespread adoption of High-Definition TV (HDTV) standards for the consumer market has started to tantalize surveillance and security professionals with the possibility of clearer, sharper images in their own industry--where tracking moving objects and accurately identifying image details are vital. While some may argue that megapixel network cameras are already providing this level of clarity, the high resolution often comes at the expense of frame rate because bandwidth requirements are so high. In contrast, the latest network cameras that comply with HDTV specifications set forth by the Society of Motion Picture and Television Engineers (SMPTE) not only guarantee a high resolution, frame rate and color fidelity, they also ensure quality video transmission using the latest standard compression technologies.
Improved resolution
In the IT world where network video standards originated, the basic resolution was set at 640 x 480 pixels. This configuration conformed to the VGA (video graphic array) resolution, a de facto standard specified by the IBM Corporation. When digitizing analog security cameras, integrators commonly used a 4CIF resolution of 704 x 480. But as the popularity of the widescreen high-definition format in home entertainment has taken hold, security professionals are growing increasingly dissatisfied with the basic resolution they are receiving on their computer screens at work. This has stimulated replacement of those traditional displays with large, flat-screen monitors and sparked demand for crisper, full-screen images better suited to the new 16:9 aspect ratio.
HDTV constitutes a tremendous leap forward in image quality with resolution up to five times higher than standard analog TV and an aspect ratio of 16:9 that fits the dimensions of large flat-screen video monitors. With HDTV standards ranging from 720p to 1080i/p – 1280 x 720 resolution and 1920 x 1080 resolution respectively – the widescreen format delivers sharper images and more vibrant color fidelity. The higher resolution standard delivers the image clarity so critical to real-time surveillance and archived video used for investigative purposes and as evidence in court proceedings.
Standards make sense
The fact that HDTV is regulated by a standardization organization like SMPTE also makes it a lot easier to conduct side-by-side comparisons of the various network cameras that support HDTV.
One of the thornier issues in the standards work was establishing a suitable frame rate because the stability of a country’s electrical supply affects the stability of an image. Some countries favored either 25/50 fps, while others favored 30/60 fps. Both rates are considered compliant with HDTV and meet the full frame rate requirements of video surveillance. As a comparison, many high resolution megapixel cameras which are non-HDTV compliant have limited frame rates, typically around 10 to 20 fps.
Network cameras with HDTV capability deliver true color representation and clear images even if the object is moving quickly. This makes the cameras highly attractive for surveillance operations that need greater image detail, such as at retail stores, airports, passport control stations, casinos and highways. For instance, an HD network camera could accurately depict the color of the chips thrown down in a hand of poker or the shade of paint on a getaway car--which might prove to be pivotal details in a criminal investigation. This has spurred popularity of HDTV in city center surveillance applications.
On the cusp of adoption
The final prerequisite for delivering HDTV video surveillance has been a more efficient compression technique. Many of the early megapixel cameras only supported Motion JPEG compression, increasing the cost of storage and making the solution economically unfeasible for many installations. The alternative was to cut the frame rate to such a low level that there was a risk of missing crucial event details.
With the advent of H.264, all the components are now in place. H.264 is an open, licensed standard that can reduce the size of a digital video file by more than 80 percent compared with Motion JPEG and by as much as 50 percent compared with MPEG-4 Part 2.
The improvements in image quality brought on by high-definition TV have generated widespread demand in the consumer market. A similar trend is already unfolding in traditional video surveillance markets. HDTV-compliant network cameras deliver a resolution, color representation, aspect ratio and frame rate that are in accordance with international standards. This makes them an appealing solution for surveillance environments requiring exceptional visual clarity.
Fredrik Nilsson is General Manager of the Americas for Axis Communications and author of the book Intelligent Network Video.
