By Peter Dempsey, Key Account Manager, Ireland, Axis Communications
Over the course of the past 10 years we have seen surveillance camera technology steadily advance offering better and better image quality and detail. Today's cameras feature Megapixel and full HDTV image resolutions with first models already taking the leap to 4K Ultra HD. Frame rates up to 60 fps are not uncommon. Wide Dynamic Range technology enables today's cameras to capture detailed images even in complex scenes with high contrasts such as when sunlight creates both very bright zones as well as very dark shadow areas. Advanced image sensors allow for color video even in very dark and extreme low-light conditions. With these advances in surveillance camera technology the requirements in terms of bandwidth and storage consumption have steadily increased. This has put a lot of pressure on system operators to manage the underlying network infrastructure as well as storage resources in a smart way. After all, the best video surveillance evidence is of no value at all if the system was configured to automatically overwrite the footage before it was needed. Also it makes little sense to invest in high quality cameras when reducing the video bit rate, resolution or frame rate to a level where important details are no longer captured and footage does not provide clear evidence anymore.
The H.264 video compression standard
Most IP-based video surveillance systems today are based on the H.264 video compression standard lowering bandwidth and storage requirements. This is achieved by reducing and removing redundant information. The video compression algorithm identifies regions in the video that have already been transferred and do not need to be sent again in the next image frame. However the H.264 standard does not specify the algorithm used to compress video but only the syntax and the method to perform playback. This allows for improved H.264 encoding solutions to be created while maintaining the same file format for interoperability with existing H.264 network infrastructure and video management software.
Improving H.264 compression with Axis’ Zipstream technology
This is where Axis saw the opportunity to take the H.264 compression standard to the next level. Fully compatible with existing H.264 network infrastructure and video management software, the Zipstream technology is a radically more efficient H.264 implementation, lowering bandwidth and storage requirements by an average 50% or more. This is achieved by adding a new module inside the video compression engine of a network camera that ensures that important details in the image get enough attention in the video stream while unnecessary data can be removed.
Axis’ Zipstream technology analyzes and optimizes the network camera’s video stream in real-time. Scenes containing interesting details are recorded in full image quality and resolution while other areas are filtered out to optimally use available bandwidth and storage. Important forensic details like faces, tattoos or license plates are isolated and preserved, while irrelevant areas such as white walls, lawns and vegetation are sacrificed by smoothing in order to achieve better storage savings. Zipstream reduces the bit rate of the video stream by applying the concepts of dynamic Region of Interest (ROI) and dynamic Group of Pictures (GOP).
The dynamic ROI optimizes bandwidth in real-time by analyzing where available bits will offer the maximum benefit from a forensic perspective. This process is performed for all image content, resulting in a totally flexible dynamic ROI. This dynamic ROI automatically expands, shrinks, changes shape, splits, merges, disappears and reappears depending on content, to optimize bandwith and storage consumption in real time. Since it is unknown in which parts of the image relevant information may appear, Zipstream prepares the system for unexpected events. This dynamic automatic ROI is much more efficient than other ROI implementations where the region is set manually.
The dynamic GOP reduces the bit rate by avoiding storage consuming I-frame updates. I-frames contain all details in an image while following P-frames and B-frames build upon the preceding I-frame and contain only the changes in the image, not the entire image. Typical surveillance scenes with limited motion can be compressed to an extremely small size this way without any loss of detail. Zipstream automatically adapts GOP length in real-time depending on the amount of motion in a scene. This allows for always the optimal setting being applied reducing bandwidth and storage requirements significantly without compromising on image detail should an incident occur.
What about H.265?
The H.265 standard is still very new. If we take a look back at how many years it has taken until H.264 was broadly supported by both hardware and software vendors in the video surveillance industry then it's fair to say that the market will still take some time. A big hurdle on the road to H.265 is certainly the steep migration path. Not only do the cameras have to support H.265 but also all other elements of a video surveillance system and the underlying network infrastructure – be that video encoders, storage systems, video management software or intelligent video analytics solutions. Zipstream offers an open, non-proprietary approach to the bandwidth and storage challenges at hand without a need to invest in new hardware and software.
In Ireland I expect to see a high demand for H.265 in the coming months so why switch to a codec which does not have full VMS support and introduces high decoding CPU usage when you can work with a proven codec in H.264 from a trusted manufacturer like AXIS for further information on this breakthrough technology please do not hesitate to contact me also use the link provided to see Zipstream in action www.youtube.com