Modern people are paying more and more attention to personal and property safety, which has prompted the video security surveillance market to become popular. Based on the attention paid to this market and the development of digital signal processing technology (DSP) and network technology, video surveillance has been developed from analog video surveillance (VCR, Video Cassette Recorder) to digital and analog DVR (Digital Video Recorder). Development of digital video surveillance to IP video surveillance systems. At present, DVR systems account for 50% of the global video surveillance market, which is a day in the sky. However, the industry is optimistic about the development trend of IP video surveillance, and the video surveillance system has become a development trend toward digitalization.
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Advantages of IP Camera
The IP video surveillance system differs from the traditional analog monitoring and DVR in terms of distance control, expansion capability and cost of control. From the perspective of the control distance, the network server in the IP video surveillance system is directly connected to the network. There is no cable length and signal attenuation limitation, and there is no geographical concept. In terms of scalability, this system has no restrictions on the number of devices, and increases the number of devices. It only means the expansion of the IP address. In terms of cost, the IP video surveillance system occupies less bandwidth and can utilize the existing LAN of the enterprise to save the cost of wiring construction during installation. In contrast, for other video surveillance systems, if a new monitoring point needs to be rebuilt, new devices are difficult to add to the original system and are limited by cable length and signal attenuation.
IP Camera Monitoring System Common Development Platform Analysis
The IP video surveillance system includes a network video server monitoring system and an IP Camera monitoring system, wherein the IP Camera is a front-end processing part of the system. The CCD/CMOS image sensor converts the optical signal of the scene into an electrical signal, which is converted into a digital signal and transmitted to the DSP memory through the data interface. As the main image processor of IP Camera's digital image processing and compression and operating system, DSP completes image compression and encoding and sends the data stream to the hard disk or other storage device for storage. It is conceivable that the front-end device has a great influence on the quality of the video image. Therefore, the choice of processor plays an important role in how developers can successfully meet the design needs of digital video surveillance products.
Currently, ASICs, FPGAs, and traditional DSPs are common solutions on the market, each with its own characteristics. Among them, ASIC is more suitable for R & D team without algorithm basis, because the compression algorithm of ASIC chip itself can help speed up product development. However, as audio/video formats and standards continue to evolve, the flexibility of this approach has become a limitation for its widespread use in video surveillance. In contrast, traditional DSP processing has more flexible processing power and is more powerful in data processing. However, the focus of DSP's traditional processing architecture is still on data computing capabilities, which is not optimized for video surveillance applications. For system-level applications with complex control capabilities and higher speed media streaming requirements, traditional DSPs are not ideal—more system resources in the DSP are wasted. Due to its powerful parallel processing capabilities, FPGAs should have significant advantages in high-end video surveillance where complex and intensive video signal processing is required. Unfortunately, the industrial ecosystem of FPGAs, large power consumption, and high cost have dragged its back legs, making it difficult to become a competitor in this application.
Another solution is to use MCU (ARM core) + DSP. Because ARM uses the RISC instruction set, it is suitable for processing control codes, and the video encoding and decoding is not enough. DSP can make up for the shortcomings of ARM, and its computing power can meet people's demand for video fluency. The idea of ​​this scheme is to play the control role of the ARM core and the processing power of the DSP processor. However, R&D personnel need to master and maintain the MCU and DSP sets of codes, and the R&D costs and requirements for R&D personnel are relatively high.
Obviously, if there is a processing platform that combines the performance of the MCU and the DSP, it can not only overcome the flaws of the ARM core + DSP, but also retain the advantages of the two. The Blackfin processor platform is such a convergence platform that brings new power to video surveillance product development. The aggregation processor combines the performance of the MCU and DSP to process the uCLinux, protocol stack, and media streams on a single core, optimizing real-time multimedia data streams and control-oriented tasks. The Blackfin family uses the MSA (Micro Signal Architecture) architecture to provide programmable 16/32-bit MCU and DSP functionality in a single core architecture that partitions control, networking, multimedia, and signal processing areas. The same development environment applies to all Blackfin product lines, enabling IP video surveillance products to be time-to-market and cost-effective.
IP Camera's video performance and dynamic range
Through powerful video processing algorithms, rich peripheral interfaces, etc., the Blackfin series can significantly improve the video performance and dynamic range of the IP Camera system.
At present, the wide dynamic IP camera on the market mainly has two technical implementation modes. One is to realize wide dynamic effect by means of image sensor and digital signal processor, and the main realization forms are double speed CCD+DSP, ordinary CCD+double shutter and the like. The technical solution adopts a double exposure or multiple exposure mode, and converts the collected analog signal into a digital signal output through a DSP, and finally combines the images formed by the double exposure or the multiple exposures to obtain a light in the light. A picture in which a dark object can be clearly expressed. Generally, such a camera is a CCD wide dynamic camera. The other is a DPS (Digital Image Sensor and Processing System) solution, in which DPS can perform multiple lossless sampling on the shooting area and directly output digital signals, so there is no need to convert the signals through the DSP. For DPS wide dynamic camera. The Blackfin platform is used in CCD wide dynamic cameras, because Blackfin has a dedicated underlying video instruction set support and a higher dominant frequency, which is more efficient and flexible in image processing. In DPS wide dynamic cameras, Blackfin does not contribute to wide dynamic range like other DSP processors, mainly for video compression.
In fact, the Blackfin series of DSPs specifically integrate parallel peripheral interfaces (PPIs) for high-speed parallel data, especially video data, adding a dedicated data throughput channel to the traditional data bus. The PPI interface works in the "hardware synchronization" mode of the BT.601 video stream and automatically decodes the BT.656 video stream preamble, enabling seamless connection to multiple video sources and image sensors, as well as direct memory access ( DMA) controller is used together. The PPI can read-only valid video information in the complete video frame information, or only the blanking area. Significant bandwidth savings can be achieved when full video frames are not needed. In this performance, the Blackfin platform provides strong support for IP Camera applications. In addition, the PPI can ignore all second field image information of the interlaced BT.656 video stream, thereby providing a method for quickly extracting the input signal. PPI can also be directly connected to a video decoder like the ADV7183A to simplify circuit design.
The Blackfin processor is ideal for implementing flexible multimedia intelligence analysis algorithms with dedicated video processing instructions. At the same time, the Image Tool Box intelligent monitoring software package is specially optimized for some common and basic functions in the intelligent monitoring algorithm, which can accelerate the implementation and optimization of the upper layer algorithm. There are a variety of intelligent processing modules on the Blackfin platform, such as fisheye correction, moving object detection and motion detection based upper layer algorithms such as intrusion detection and positioning.
In HD and standard definition IP Camera applications, MPEG 4 and H.264 compression formats have become mainstream. Compared with the traditional video codec formats H.263 and MJPEG, the H.264 video compression format can reduce the required bandwidth and provide effective network extraction for efficient data block transmission. Floor. The single-core architecture of the Blackfin aggregation platform delivers core frequency performance up to 600MHz (1200MMACs), multi-channel audio, VGA/D1 video applications and MPEG-4, H.264 and Windows Media compression formats for advanced video at higher resolutions Codec is processed. These capabilities are applied to software that supports the Blackfin platform. For different media formats and functions, simply change the advanced software.
By aggregating MCUs and DSPs onto a single-core platform, the Blackfin processor accelerates the development of video surveillance systems, and the large number of integrated peripherals saves a lot of time and cost in reconfiguring these devices.
In addition, in video surveillance applications, the image of the monitored object is overexposed or underexposed, which makes people very annoyed. Wide dynamic range products are well adapted to different light intensity differences in different parts of the same scene, and can fade the difference in light brightness in the final video, making each part of the entire picture clear and identifiable, avoiding Image quality is degraded.
With the development of China's domestic security surveillance market, there is a growing demand for such wide dynamic range IP Camera products. At present, the mainstream wide dynamic camera technology is to acquire two images of high-speed shutter and low-speed shutter for each frame through a camera, and synthesize it into one frame image through DSP processing in the background. Such a technical system has higher requirements for the entire camera from shutter to image sensor (such as CCD or CMOS) to background processing programs and processors.
Processor selection
According to the specific circumstances and occasions of the application, the correct selection of the processor can effectively improve the image quality and detection capability. Performance is clearly a key factor. Since all of the processor's workload is concentrated on image processing, this requires the processor to be optimized to handle a large number of different video tasks. Depending on the application, the Blackfin platform includes a variety of products to choose from.
For example, the BF51x series, which includes a variety of products such as BF512, BF514, BF516 and BF518, is suitable for a variety of instrumentation, portable medical diagnostics and VoIP phones. These single-core aggregation processors reduce the number of components and reduce power consumption compared to MCU+DSP solutions. The BF51x processors feature clock rates up to 400 MHz (800 MMACS) and integrate Lockbox security technology. Each processor includes two dual-channel synchronous serial communication ports (SPORT), a high-speed parallel peripheral interface, an I2C-compatible TWI, two PC-compatible UARTs, and two SPI-compatible serial peripheral interface ports. .
In the BF52x family, the processor consumes as little as 0.16mW/MHz at 250MHz. The processor operates at 600MHz and its low-power family implements frequencies up to 400MHz. Lockbox security technology provides effective protection in terms of intellectual property security and network security capabilities. As a media co-processor, ADI optimizes processors with fewer peripheral circuits, allowing additional features to be added during design. In addition, thanks to its high-efficiency signal processing capabilities and rich peripheral interfaces, seamless connectivity to Ethernet and Wi-Fi 802.11 a/b/g modules is easy to implement and is ideal for IP cameras.
The BF534 processor's system peripheral includes an integrated CAN 2.0B controller, two UART ports, one SPI port, two serial ports, two external DMA request signal lines, 48 ​​general purpose I/O pins, and a parallel peripheral. Interface, etc. The ADSP-BF536/537 further expands its capabilities to include IEEE 802.3 10/100 Ethernet MAC and enhanced DMA systems to provide high network bandwidth capabilities.
The BF561 is a dual-core 600MHz processor that delivers maximum performance and maximum design flexibility in signal processing and control integration and segmentation.
Overall, Blackfin is a platform suitable for video surveillance applications and effectively helps accelerate the design and construction of IP Camera systems. It is effective in improving the video performance and wide dynamic range of IP Camera.
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