Defining HD and megapixel camera resolution

Why high definition and megapixel resolution aren't the same


[Editor's Note: HD and megapixel video surveillance has been a hot topic for the security industry, and the trend for IP video installations has been toward the installation of HD and megapixel cameras instead of standard-resolution IP cameras. In this guest column, Raul Calderon of Arecont Vision (a manufacturer of megapixel and HD security cameras) puts forth the argument for using megapixel video and explains the differences and similarities between HD and megapixel security cameras.]

As IP-based video systems continue to gain widespread popularity in the video surveillance market, one of the benefits is the ability to capture high-resolution images through megapixel video. Also emerging is use of the HDTV standards that are prevalent in the consumer video market. The images produced by this new generation of cameras are often collectively referred to as high definition (HD) or as megapixel images. Because the terms HD and megapixel both indicate an improved level of imaging performance compared to traditional analog images, they are often thought to be the same, but there is a difference.

In fact, the broadcast (or consumer) HD resolution should not be seen as the goal in video surveillance. Megapixel cameras can offer image resolutions higher than broadcast HD resolution, and I think an explanation is in order.

Megapixel vs. HD

One could consider HD a subset of megapixel. HD is defined by specific resolutions at specific frame rates with a specific aspect ratio. Any camera with a resolution of more than a million pixels is by definition a megapixel camera. The lowest resolution in the megapixel range in the security market is around 1.3 megapixels, which provides 1280 x 1024-pixel resolution (or 1.3 million pixels), and we're already seeing security cameras with resolutions as high as 10 megapixels (3,648 x 2,752 pixels). The range of megapixel cameras continues to expand to accommodate various application requirements. For example, at my own firm Arecont Vision, we have a wide range of megapixel cameras that includes 1.3, 1080p, 2, 3, 5, 8 and 10 megapixel offerings, and we're also planning 20 megapixel security camera solutions.

HD refers to cameras with a standardized resolution of 720p or 1080p. The numbers 720 and 1080 refer to the horizontal resolution. Therefore, 720p HD camera resolution provides images that are 1280 x 720 pixels (that adds up to 921,600 pixels, which means a 720p HD camera is not technically a megapixel camera), and 1080p HD cameras provide 1920 x 1080-pixel resolution, or 2.1 megapixels. The HD video format also uses an aspect ratio of 16:9 (rather than 5:4 or 4:3), and the frame rate is standardized at 60, 50, 30 or 25 frames per second (the fps depends on your TV).

Momentum for HD and megapixel IP video

According to a report by TechNavio Insights, IP surveillance is poised for significant growth among end-users and large organizations. The benefits of software-driven functionality and the control, scalability and broad availability of video are often listed as factors contributing to this growth. However, among the biggest performance features of IP surveillance is the ability to provide a broad range of video resolutions. With H.264 compression and programmable resolutions and streaming, the new standard for video resolution can be defined simply as "whatever the application calls for." With IP/megapixel video, cameras assigned to cover critical areas can now capture any level of resolution up to 10 or more megapixel images (3,648 x 2,752 pixels – nearly five times the resolution of a 1080p camera).

With the ability of today's megapixel cameras to be adjusted to specific surveillance locations at different resolutions, cameras of varying resolutions can be combined on the same network. Core areas can then be viewed and recorded with higher resolution quality while secondary areas are viewed at less resolution with slower frame rates. Video analytics can also be applied to trigger megapixel streaming only when automatically activated; it's an approach that can be used to conserve bandwidth for existing network pipelines and to conserve recorder storage space.

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