Dali's DVR-based Surveillance Systems Are
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Today, cameras are everywhere. Video surveillance systems are routinely deployed in banks, businesses, retail outlets, homes, day care centers, manufacturing facilities, and transportation (airport/seaport/bus) systems. Surveillance cameras are also often used at restaurants and food courts, helping management to maintain proper hygiene and ensuring that operational procedures are followed. In recent years, advances in video compression techniques have spawned cost reductions for video equipment. This has made digital video extremely attractive for many applications, including security surveillance, which has become so widespread.
Zhejiang Dali Technology Co., Ltd. (Dali, for short) is a manufacturer that specializes in the scientific research, production and sales of such products as infrared cameras and digital video recorders (DVRs). The company's competitively priced DV series of embedded video products, used for surveillance, are renowned for advanced technology and system stability, selling well throughout China and available for export anywhere in the world. Dali turned to Analog Devices, Inc. (ADI) for its Blackfin ADSP-BF532 processors, which are now widely deployed in Dali's existing DVR surveillance systems.
How DVR-based Surveillance Systems Work
In many ways, a DVR is a hard drive inside a box, which is connected to the outside world through a variety of jacks. Much easier to use and more efficient than the outdated VCR tape, a DVR captures video digitally and writes it to the digital storage device. The system usually contains an MPEG-2 encoder (MPEG-2 is a compression standard used to fit information onto a DVD), which converts data from analog to digital. From the encoder, the signal is shipped off to the hard drive for storage, and then to an MPEG-2 decoder, which converts the signal back to analog and sends it to the monitor for viewing.
A PC and industry-standard operating system can be the hub of a DVR-based surveillance system. An "embedded" DVR typically uses a customized operating system (residing on a hard disk), an embedded microprocessor, recording space, and a buffer for real-time viewing.
In a typical system, cameras are attached to the back of the system through PCI slots. Users can view and record surveillance footage, which is stored on the hard drive, and can search archives for incidents, marking a grid or area of video where the incident occurred. This will show anything that happened in that area without having to view hours of footage. Remote view features enable users to view both live and recorded surveillance footage stored on a DVR system from any computer with an Internet connection.
The frame rate of a card is how many frames per second it will show. The higher the frame per second (fps), the smoother the picture, and more hard drive space is also required. The frame rate per each camera is equal to the frame rate of the card divided by the number of cameras. Example: 120fps card, 4 cameras=30fps for each camera. When DVRs are advertised with "real-time" performance, they usually mean a frame rate of about 30fps, which ensures that the picture is smooth.
Optimized for Video
Dali says Blackfin's low price, small package, and low power consumption made it the ideal processor for its DVR series, especially for the DV-1016CM - the first 16-channel DVR-based surveillance system in China. The DV-1016CM features dual embedded 32-bit CPUs, a Blackfin ADSP-BF532 processor, a built-in 16 x 4 matrix, optimized MPEG4 encode/decode algorithms, hard-disk management technology to shorten hard-disk working time, low power consumption to prevent overheating, and a 25fps frame rate for near real-time viewing. The system can view and record streaming video using up to 16 cameras.
Dali says that porting the MPEG4 CIF and D1 algorithms it developed to Blackfin was easy because of the Blackfin processor's RISC-like instruction set. (Common Image Format, or CIF, is a standard frame size for digital video; Digital 1, or D1, is a broadcast-quality component digital videotape format that records uncompressed frames and requires a 27MB/sec transfer rate.) In addition, Dali says that ADI's VisualDSP++, an easy-to-install and use integrated development and debugging environment (IDDE) that enables efficient management of projects from start to finish, also helped to simplify product development and speed time to market.
A Stronger Signal
The Blackfin processors' efficiency in processing digital media comes from a combination of pure horsepower and the fact that Quad 8-bit video ALUs are embedded into the architecture. This allows for very efficient processing of industry standard video algorithms such as JPEG, MPEG, Windows Media, and H.263/264 in a variety of screen sizes and frame rates.
The Blackfin processor architecture also includes instructions specifically designed to enhance performance in video processing applications. For example, Discrete Cosine Transform (DCT) is supported with an IEEE 1180 rounding operation, while the "SUM ABSOLUTE DIFFERENCE" instruction supports motion estimation algorithms used in video compression algorithms such as MPEG2, MPEG4, and JPEG. Implementing video compression algorithms in software allows OEMs such as Dali to adapt to evolving standards and new functional requirements without hardware changes.
The enhanced instructions also allow Blackfin processors to be considered in applications previously addressed primarily by ASICs, VLIW media processors, or hardwired chipsets. Dali says for DVRs, a programmable processor such as Blackfin is preferable over an ASIC because of its flexibility; the Blackfin processor will allow Dali to easily upgrade its product line to include higher resolution algorithms in the future.
Dali felt that power management was especially important for its line of DVRs that will undoubtedly operate for long periods of time in disparate locations. Fortunately, all Blackfin processors employ multiple power saving techniques. For one, the processors are based on a gated clock core design that selectively powers-down functional units on an instruction-by-instruction basis. Blackfin processors also support multiple power-down modes for periods where little or no CPU activity is required. Lastly, and probably most importantly, Blackfin processors support a dynamic power management scheme whereby the operating frequency and voltage can be tailored to meet the performance requirements of the algorithm currently being executed.
Because the Blackfin core architecture is consistent across the product line, it was an easy decision for Dali to choose the ADSP-BF561 processor to upgrade its 16-channel DVR. A high-performance member of the Blackfin family, the ADSP-BF561 is comprised of two independent Blackfin cores in one processor. The new Blackfin ADSP-BF561 processor, which extends processing performance while retaining the low power attributes found in the original Blackfin processors, will also reduce the cost of Dali's surveillance system.
For more information, visit dali-tech.com.
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