HD Surveillance Performance Improves as Demand Rises
January’s SSI feature “Video Continues to Enhance Its Security Image” has a dozen top technology providers identifying the latest and greatest video surveillance technologies. Among the participants was Pelco by Schneider Electric Sr. Product Marketing Manager for Imaging and Storage Systems Sara Scroggins, who addressed the topic of megapixel/high definition (HD) recording and how it is overcoming technical challenges and misperceptions.
In the following extention of that piece, Scroggins provides keen insights into how megapixel technology works and how manufacturers are improving performance, especially as it pertains to bandwidth consumption and low-light surveillance. She also speaks to increasing opportunities as regulations and end-user demands propel HD surveillance forward.
As we begin 2011, what is the latest and greatest in megapixel cameras and systems?
Sara Scroggins: Some of the most exciting developments are coming in the advancement of wide dynamic range imagers with megapixel resolution. These developments are being driven by advancement in CMOS imager technology. Historically, CMOS has not performed as well as CCD under low-light conditions and in warmer environments. The challenges associated with CMOS imagers include smaller pixel size, dark current, higher read noise, and column correction processing. Over the past three to four years, CMOS imager manufacturers have been working in each of these areas to increase the performance of CMOS devices. We have seen dramatic improvements, and in fact, testing in our labs confirms that today’s CMOS imagers perform at par or better than CCD imagers in similar conditions.
What are the greatest challenges or hurdles megapixel technology faces and what is being done to make it even stronger and more viable?
Megapixel technology presents technical challenges in two key areas – low-light performance and bandwidth consumption. Let’s consider low-light performance first. For a given image format size, CMOS sensors are typically megapixel arrays, as compared to standard definition CCDs, which results in less light gathered in each pixel. Active circuits in CMOS share light gathering space, which results in less light gathered in each pixel. Also, in the past, the smaller pixels in CMOS imagers yielded an effectively lower Signal-to-Noise Ratio, when compared with CCD imagers. You can see the issues this could cause when deploying megapixel cameras in low-light environments. The good news is the advancements in CMOS technology have eradicated the low-light performance gap between CCD and CMOS, making CMOS a viable or even preferable choice for low-light imaging. Now to bandwidth consumption, storage and image file sizes. More pixels mean more data, which means larger files for each image captured by a megapixel camera. When you consider that a typical 1.3-megapixel camera consumes 2 to 5Mbps of bandwidth, or higher, it’s easy to how you can quickly use up all the bandwidth in the network while filling up all available storage. H.264 encoding offers the ability to optimize image quality while minimizing file size, particularly compared to previous compression schemes, such as MJPEG, earlier parts of MPEG-4,etc.
It’s important for integrators and system designers to understand that not all flavors of H.264 are the same. Some manufacturers only utilize base profile H.264 that offers some improvement in compression but not as much as high profile H.264, which offers the greatest benefits and flexibility in compression and image quality. Integrators should also be aware that the effectiveness of H.264 compression varies, depending upon the complexity of the surveillance scene – scenes with more motion and more varied lighting will create larger image sizes. However, even though the incremental gain in compression, from base profile H.264 to high profile H.264, may seem relatively small on an individual camera scale, when you start to multiply it across tens or hundreds of cameras that additional bandwidth savings can really add up.
The type of storage system also has a big impact on overall system cost and design. Traditional COTS data servers, while being relatively inexpensive, are designed for the ‘write once, read many’ duty cycle of traditional data applications. With video surveillance, the burden placed on storage is opposite – because video is being recorded all the time, so storage devices need to be able to write data to hard disks all the time. If the storage subsystem is not tuned for massive amounts of write operations, the cost of deploying a storage solution increases dramatically. Some manufacturers have designed and developed video storage hardware specifically for the special challenges of recording video surveillance data. This should be an important consideration in any video system design decisions. Matching cameras and recording/storage using high profile H.264 gives users the greatest outcome, allowing them to maximize the benefits of HD/megapixel imaging while mitigating or minimizing bandwidth issues on their network.
Why should installing security integrators care about megapixel technology and what are some of the specific opportunities it afford them from both services and market niche standpoints?
Our industry is constantly striving toward producing better images with more detail, to inform better business decisions – whether for responding to real-time events or conducting forensic investigations. To be sure, today’s IP cameras can produce a significantly better picture than their recent analog predecessors. In our experience, once most end users have seen megapixel images, they want megapixel cameras for their system. That means successful integrators will have to know how to optimize networks for megapixel streams. But it’s more than just the end users saying, ‘I see it, I want it.’ Other factors are driving megapixel adoption as well. New regulations have begun mandating minimally acceptable quality, frame rate, and retention periods, in market niches ranging from gaming to criminal justice to public safety and city surveillance. End-user demand is also increasing for higher quality video footage, driving a need to deliver cost-effective recording solutions for today’s IP and megapixel cameras.
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