Pixim's Compression Advantage
It's widely recognized that Pixim's Digital Pixel System® image capture and processing technology enables video security cameras to produce high-resolution, color-accurate images regardless of a scene's lighting conditions. There's another benefit that isn't as visually obvious: Pixim's Digital Pixel System technology produces images that are more efficiently compressed, which can lead to dramatically lower system costs for storing security video or moving it around a network.
Digital Pixel System technology and compression
In today's networked systems, video is compressed before it is stored. In the case of CCTV cameras, this happens at the DVR. With IP cameras, this happens within the camera itself. The efficiency of a compression algorithm such as MPEG-4 or H.264 is affected by a number of factors, but two of these factors can be directly influenced by a camera's video sensor technology:
- The amount of temporal noise present in the video – Video compression algorithms "see" temporal noise as if it were motion, and more motion leads to higher bit rates and larger file sizes for compressed images.
- The amount of high-frequency content in a scene – Sharp edges such as the lines separating brightly lit and deeply shadowed areas, the edge of a building, or stripes or other color patterns against the solid background of an item of clothing are seen by the compression algorithm as high-frequency content that increases the compressed bit rate as well as the resulting recorded file size.
Pixim's Digital Pixel System technology optimizes what the compression algorithm receives as input from a scene. This is done in a variety of ways:
- Noise reduction and elimination. Pixim's Digital Pixel System technology is based on intelligent exposure, color, and noise processing algorithms that maximize SNR under all lighting conditions. It is an all-digital technology, so noise doesn't get randomly introduced at any point during image processing. Also, true black is clamped at a digital black level that is not modulated with random noise, so black areas in a scene show up as black areas instead of as noisy sparkles that look like moving objects to a compression algorithm.
- Elimination of "false motion". Pixim's Digital Pixel System technology uses a global electronic shutter and progressive capture to image the entire scene all at once. It also includes special capture modes for eliminating flicker and color roll that occur with scenes illuminated by fluorescent lighting. Analog sensor technologies use rolling shutters and interlaced image capture which can actually introduce false motion and high-frequency content into captured images.
- High-frequency content reduction. Pixim's Digital Pixel System technology uses image processing algorithms that have been designed to produce sharp, color accurate images while not over-sharpening them like other image processors do. Over-sharpening introduces high-frequency content into the scene that does not compress efficiently. Note the unnecessary noise introduced into the blacktop and chain link fence in the over-sharpened image below.
The advantages of better compression
More efficiently compressed video images have lower bit rates and smaller file sizes – in some cases 20-30 percent smaller - which means they take less room to store on a DVR or NVR and require less bandwidth on a network. This gives video security system operators a tremendous amount of flexibility in terms of how they take advantage of Pixim's compression advantage. For instance, they can:
- Use smaller, less-expensive hard drives and backup systems to reduce their overall security system costs.
- Store additional hours of video per camera.
- Store higher-quality video for one or more cameras.
- Increase the video frame rate stored for one or more cameras.
No matter how you look at it, Pixim's Digital Pixel System technology delivers compelling benefits for video security systems. Pixim's technology begins with low-noise digital pixels and uses advanced processing to enhance image quality and eliminate image noise. The result is clean video that compresses better. Cameras powered by this innovative technology are able to capture the crisp, accurate, and true-to-life images required for effective security applications while also offering tangible financial benefits for their operators.
For more information, including results from an independent test lab's side-by-side comparison between a Pixim-powered camera and two CCD cameras, download the Compression White Paper and view Pixim's newest Flash Flip-book on Pixim's Compression Advantages.