In China's surveillance market, digital hard disk recorders (DVRs) once occupied half of the video surveillance market. However, with the development of network surveillance, network cameras (IPC) and network hard disk recorders (NVR) have also caught up. Among them, intelligent video analysis is becoming a hot spot for digital video surveillance, and DSP has become the driving force of this technology. The powerful SoC system is also one of the driving forces of intelligent analysis technology.
From the perspective of technology development trends, network video surveillance will gradually become the mainstream model; this is already an unquestionable trend. With the development of network surveillance, intelligent video analysis has become the next important direction for the development of IP video surveillance. However, for most chip manufacturers and system manufacturers, as IP video surveillance gradually develops in the direction of high-definition and intelligence, it brings them not only huge market opportunities, but also new challenges. The main technical trends in designing digital video surveillance systems are the need to achieve high image quality (1080p resolution), video analysis, intelligent management, IP, H.264 video compression standards, higher image signal processing clarity, and device functions for applications And cooperate with the project algorithm function. These new trends make developers have to face the challenges of low power consumption, low cost and environmental protection.
Powerful SoC system
TI's digital signal processor (DSP) has strongly promoted the development of digital video surveillance technology, among which the milestone is the TMS320DM642 universal digital media processor. The digital media processing single-chip system Davinci (DavinciTM) launched by TI has provided a powerful platform for digital video surveillance. DaVinci's various series of platforms can completely cover the various application directions of digital video surveillance, including ARM as the main control processor and DSP as the main processor. Its common feature is that it can support multiple video compression formats, including H.264 / MPEG-4, etc. All DSP cores have the ability to support VCA.
The current DSPSoC-based solutions dominate the monitoring market. At the same time, some FPGA manufacturers hope to show their advantages in differentiation and customization. By combining FPGA devices and MPU / DSP for monitoring applications, designers can benefit from the inherent flexibility of programmable coprocessors, and they can also use FPGAs to focus on developing algorithms to take full advantage of MPU / DSP Processing power. Some manufacturers have adopted the DSP FPGA method in their multi-channel video surveillance system hardware platform, using TI's TMS320DM6437, only one digital video input interface, in order to connect to the 8-channel video decoder, the video decoder The coupling logic is added between the video input interface of the DSP, and the programmable FPGA can easily realize the coupling logic between the two.
In order to meet the requirements of the future digital video surveillance market, greater flexibility is necessary. Video compression technology will develop to intelligent codecs. Traditional surveillance will still develop to real-time intelligent analysis. Optical systems will be combined with digital electronic systems. Closer integration.
DSP processor enhances intelligent analysis and processing capabilities
After several generations of technological evolution, video surveillance systems are moving towards networked (IP) and intelligence. In addition, the coexistence of analog and digital monitoring systems will also be a feature of the Chinese security market in the coming years. As a mid-to-high-end option, DSP is currently the mainstream processor in the Chinese surveillance market. ASICSoC is a latecomer and has a certain impact on the market. In addition, FPGA is also trying to enter the market, but there is no obvious success story. Since there is no standard algorithm for intelligent analysis and processing at this stage, the implementation of intelligent video analysis and processing based on different compression formats will have very different MIPS requirements for DSP, so the optimization of the algorithm is very critical. Due to its flexibility and high performance, DSP is better at intelligent analysis and processing.
The ideal DSP processor for image processing applications must have the following characteristics: strong core processing capability; instruction set specifically for image processing; low-power hardware architecture that is easy to transfer large amounts of data; high integration; rich software module library ; Powerful development tools. For a video surveillance system, the most suitable control and processing should be a convergent processor that combines control functions and digital signal processing functions.
Most of the early domestic video surveillance products in China use DSP. In multi-channel, high-resolution video codec applications, DSP software is difficult to meet the system requirements. FPGA adopts hardware acceleration method, which can perform multi-channel compression in real time. The advantage of FPGA is that it is programmable, which is very suitable for applications that require high flexibility and provide differentiated applications. Currently, video surveillance products using FPGA chips have been mass produced.
H.264 video codec technology
In the history of video surveillance, there have been various video compression standards. Standards defined by the International Telecommunication Union ITU for low-bit-rate video telephony, including H.261 / 2/3; the International Organization for Standardization ISO for consumer applications defines MPEG standards for moving image compression, including MPEG1 / 2 / 4; H.264 codec technology is defined by ITU and ISO according to the target application cooperation (Joint Video Team JVT), and some standards still exist today. At present, M-JPEG, MPEG4 and H.264 are mainly used in the application. We compare these standards through the following points.
Implementation cost: including the complexity of implementation of the algorithm and the degree of resource occupation, the difficulty and cost of technology acquisition, and the cost of its final reflection in the product;
Coding performance: mainly reflected in the same subjective and objective visual quality, the size of the code stream obtained after compression, which is very critical for network transmission and storage;
Network support: The quality of network support mainly depends on the fault tolerance of network packet loss and errors and the adaptive ability of the support network;
Application support scope: Due to the ever-changing application requirements in the field of video surveillance, the ability of a platform to support different needs is also very important;
Future potential: From the perspective of development, the potential of a standard is reflected in the broad acceptance of the industry in the future, the smoothness of conversion in related applications, and the degree of support for interconnection.
In video surveillance products, the encoder is always the focus of the program. A suitable encoder program can often determine the success or failure of a product. The H.264 coding scheme is becoming the mainstream of the market, and it has been widely recognized by the market for its excellent coding performance and good network adaptability. It can not only support a wide range of application environments, but also meet the needs of different resolutions, different bit rates, and different transmission and storage environments.
H.264 is an advanced video processing technology, which is recognized by the industry. Under the same video playback quality, H.264 saves nearly 40% of the transmission bandwidth or hard disk storage space compared to MPEG4, which is undoubtedly the promotion and application of remote monitoring To a very important role. However, H.264's coding efficiency comes at the cost of much more complex calculations than MPEG4. It uses the most advanced frame prediction mode, including complex motion estimation, 1/2 and 1/4 pixel prediction; far more than MPEG4 Advanced intra-frame prediction modes, including up to 13 intra-frame prediction modes; H.264 introduces a new in-loop filter (in-loopfiltering) technology, which greatly contributes to the substantial improvement of video playback quality.
However, the application of new technologies requires a lot of arithmetic processing, and it also puts forward new requirements for the video codec processing platform. For video codecs in the form of software, such as those implemented with general-purpose processors such as DSPs, due to processing power limitations, many of H.264 ’s most advanced technologies (such as intra-frame, inter-code prediction mode, loop Road filter, etc.), such a result is that its encoding effect returns to the level of MPEG4. What is more serious is that the code stream output by such an encoder does not comply with the H.264 standard, and all general decoders cannot be matched with them to form an open system. When choosing non-standard encoders, users can only limit the use of non-standard decoders, which turns into a closed system.
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