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Video signals are digitally encoded and transmitted or stored, which has incomparable advantages over analog video signals. Digital coding compression of video signals comes at a price, and the cost of compression determines the cost of the system.
Digital video surveillance has only entered the practical stage after the emergence of a single video encoding chip. Due to the diversity requirements of digital video surveillance applications, video processors using SOC technology (VIDEO PROCESSOR, some also called DSP) will dominate the mainstream of digital video surveillance products.
First, the special compression chip brings the digital video surveillance market
In surveillance applications, video image digitization is real-time encoded and compressed, which is completely different from VCD and DVD programming (VCD and DVD programming can take dozens or even hundreds of times to encode and compress). The video codec has a very high computational strength. It is almost impossible to implement video codec with the original DSP. The optimization technique of the compression algorithm is still immature. It must be used in a dedicated ASIC with some specific hardware accelerators such as motion estimation (ME) and DCT. Module, format conversion, variable length codec (VLX), etc. to achieve real-time encoding. Due to the complexity of image coding and decoding, pure hardware implementation is too large, almost impossible, and must be done with a powerful processor. This is why the dedicated image compression chip also needs to download the microcode. Currently, the MPEG-1/2 encoding chip used has microcode, and the hard compression or chip compression has a processor. It is also the emergence of these compression chips, especially the emergence of single-chip coding chips, the complexity of the monitoring system is greatly reduced, and the cost is also reduced, which makes video digital monitoring possible. In the case that the general-purpose DSP or video processing chip has not been developed to be able to compress the video signal in real time, the emergence of a dedicated video compression chip drives the video analog monitoring to digital video surveillance.
In addition to the processor, the video image processing chip (VIDEO-PROCESSOR) integrates some other IP (INTELLIGENT PROPERTY) modules, such as VIDEO IN, VIDEO OUT, AUDIO IN, AUDIO OUT, etc. Like compression hardware acceleration modules. Such a chip is called SOC (SYSTEM ON CHIP), which is a single-chip system. In essence, the dedicated video compression chip and the general-purpose video processing chip belong to the SOC. The difference is that the former has a fixed compression module, a fixed processing method and a fixed micro-code, and the latter needs to monitor the product developer to develop a video compression algorithm program. .
Dedicated video chips are designed for consumer applications, and they are applied to the surveillance field. There are other issues:
1. Consumer use is a single video encoding. It does not require simultaneous compression of multiple channels of video at the same time, and monitoring often requires multiple channels of video to be compressed at the same time.
2, the continuous use of consumer time is generally not long, and monitoring use is often used for a long time.
3. Consumer use often requires post-processing and editing of video image signals. The monitoring system emphasizes real-time compression. In real-time compression, necessary processing must also be performed, such as motion detection, time generator, LOGO. Identification, watermarking, etc. These processes are pre-processing. These auxiliary functions are also very important for compression products. These processes are performed before or during compression.
4. The more important difference is that consumer use does not require dynamic adjustment of coding parameters. In the field of surveillance, there is a strong need to dynamically adjust coding parameters such as frame rate, image quality, and frame structure.
Compared with the consumer market, the monitoring market is too small, and the demand for monitoring applications is diverse, and it is impossible to use a chip to meet the whimsical application requirements. It is also impossible for chip manufacturers to develop a series of chips for the monitoring market, and the chip development cycle is very long, the cost is too high, the market is constantly changing, and the product is updated very quickly. For the monitoring market, waiting for integration After the algorithm's dedicated video compression chip matures and develops the product, it certainly cannot keep up with the development of the market. Dedicated video compression chips that have been widely used in the monitoring field, such as W99200AF, Z1510, SM2210, SM2288, IVT15, etc., have been unable to meet the requirements of the monitoring market application.
Second, video processor to promote the digital video surveillance market
With the advancement of IC technology and the development of processor technology, processors of DSP, RISC and VLIW are gradually unified. The current multimedia processor combines three processor technologies.
SOC technology is developing very fast and VIDEO PROCESSOR is already very powerful. The video processor integrates many peripheral circuits, including VI unit (VIDEO IN UNIT), VO unit (VIDEO OUT UNIT), AI unit (AUDIO IN UNIT), AO unit (AUDIO OUT UNIT), and some coprocessors inside. Such as variable length code / decoder VLX, motion prediction ME, DMA controller, IIC controller, etc., the integration of these IP modules greatly enhances the processing power of VP, these VP also appear under the name of DSP.
With the continuous improvement of DSP frequency, the increasing processing power, and the continuous improvement of video coding technology, it is possible to develop video compression software on DSP to realize real-time video compression. Among them, it is very important to develop high-efficiency video compression software based on the general DSP platform with independent knowledge products. Our ability to develop a general-purpose DSP is not enough. We have not enough ability to develop a dedicated video compression chip, but we can develop high-efficiency video compression software on a general-purpose DSP and add new ones according to the needs of monitoring market applications. The function. Due to the closed nature of the surveillance market, the video compression software can be free from the limitations of the standard, and can absorb the video coding results in time to meet the market demand and meet the user requirements as the first purpose. The dedicated video compression chip is designed for consumer use, emphasizing compatibility. Therefore, in order to meet the needs of the surveillance market, custom compression software is developed on the video processor with the following features:
1, can be subject to standard restrictions, adopt compression technology, in line with the characteristics of the monitoring market. For example, monitoring is a long-term recording, and the requirements for low bit rate are very high. Therefore, in video compression software, the first pursuit is a high compression ratio.
2. Remote monitoring emphasizes the function of the network and the limitation of low network bandwidth, which leads to the requirement of low bit rate. In some applications, the network latency is very low and low latency is required. Therefore, the video compression software can implement different functions for different applications according to different application requirements: the target can be achieved with a low code rate, and the design can be achieved with low latency.
3. According to the application and environment changes, the coding parameters such as image quality, frame rate, frame structure, etc. can be dynamically modified during the compression process.
4, can easily realize video signal overlay icons, strings, etc., such as time information, location information.
5. In many monitoring situations, voice compression is also required. Generally, consumer chips support sound compression. The bandwidth of the sound is much larger than the bandwidth of the voice (the voice is within 3400 Hz, and the bandwidth of the sound is from 0 to 20 KHz). The voice compression can be G.729a, G.729, G.723, G.723.1, etc., the compressed code stream is only 8Kbit/s, 6.3Kbit/s, 5.3Kbit/s, and the compressed stream of sound is at least 16Kbit/s. Generally, it is above 32Kbit, which is not much different for storage, but it is especially important for transmission on narrowband.
6, support "watermark" technology to prevent the record file from being changed.
In short, the development of its own compression software on the video processor, with independent intellectual property rights, can be adjusted according to the actual needs of the application of the corresponding coding software, the significance is particularly significant: no longer subject to compression chip constraints, can be free to play. It is the strength of the Chinese people to realize the software compression coding of video images on the video processor (DSP). The Chinese people are mutually reinforcing, seize the opportunity, and create national brands in the growing field of surveillance.
Third, the conclusion
Hangzhou Hikvision Digital Technology Co., Ltd. is a professional company dedicated to the research and development of video and audio codec core technology, development and production of independent digital video and audio compression products, as a pioneer in the development of video coding software on video processors (DSP) in China. It has made very useful attempts on a variety of video and video processors (DSPs), and has made very significant progress. The current COIN DS-400XM and COIN DS-400XH two series of products represent the monitoring class. The development direction of digital video and audio coding products.