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The Role of Video Coding Chips in Digital Video Surveillance
The video signal is digitally encoded for transmission or storage and has unparalleled advantages over analog video signals. The digital coding of video signals is costly, and the cost of compression determines the cost of the system.
Only after the emergence of a single-chip video encoder chip, digital video surveillance has entered the practical stage. Due to the diversity of requirements for digital video surveillance applications, video processors (VIDEO PROCESSOR, also known as DSPs) using SOC technology will dominate the digital video surveillance products.
I. Dedicated Compression Chips Bring Digital Video Surveillance Market
In surveillance applications, the digitization of video images is encoded in real-time, which is totally different from the production of VCD and DVD programs (the production of VCD and DVD programs can take tens or even hundreds of times of encoding compression). Video codec operation is very large, it is almost impossible to use the original DSP to achieve video codec, compression algorithm optimization technology is not yet mature, must use a specific hardware accelerator in a dedicated ASIC such as motion estimation (ME), DCT Module, format conversion, variable length codec (VLX), etc. to achieve real-time encoding. Due to the complexity of image coding and decoding, the scale of pure hardware implementation is too large, it is almost impossible, and it must be completed with a powerful processor. This is the reason why the dedicated image compression chip also needs to download the microcode. At present, there are microcodes in the used MPEG-1/2 code chips, and the hard compression or chip compression has a processor. It is also the emergence of these compressed chips, especially the emergence of a single-chip encoding chip, the complexity of the monitoring system is greatly reduced, and the cost is also reduced, which makes video digital monitoring possible. In the case of a general-purpose DSP or video processing chip that has not yet been developed to compress video signals in real time, the advent of dedicated video compression chips has driven video analog surveillance to digital video surveillance.
In addition to the processor, the video image processing chip (VIDEO-PROCESSOR) also integrates some other INTELLIGENT PROPERTY modules, such as VIDEO IN, VIDEO OUT, AUDIO IN, AUDIO OUT, etc. Like compression hardware acceleration module. Such a chip, called SOC (SYSTEM ON CHIP), is a monolithic system. In essence, both dedicated video compression chips and general-purpose video processing chips are SOCs. The difference is that the former has a fixed compression module, a fixed processing method, and fixed microcode. The latter needs to monitor product developers to develop video compression algorithm programs. .
Dedicated video chips are designed for consumer applications and apply them to the monitoring field. There are still other problems:
1. Consumer use is a single video encoding, which does not require multiple video compression at the same time, and monitoring often requires multiple video compression at the same time.
2. The time for continuous use of the consumer is generally not long, and the monitoring use is often continuous use for a long time.
3, Consumer use often requires post-processing of video image signals for editing; while the monitoring system emphasizes real-time compression, in real-time compression must also carry out some necessary processing, such as motion detection, time generator, LOGO Identity, watermarks, etc. These processes are pre-processing, and these ancillary functions are also very important for compressed 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 application of surveillance, there is a strong need for dynamic adjustment of 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. It is impossible to use a chip to meet the demand for bizarre applications. 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, the speed of product replacement is very rapid, for the monitoring market, waiting for integration After the maturity of the dedicated video compression chip for the algorithm, the development of products will certainly not keep up with the development of the market. The dedicated video compression chips that have been widely used in the surveillance field such as the W99200AF, Z1510, SM2210, SM2288, IVT15, etc., can no longer meet the requirements for monitoring the market applications.
Second, video processor to promote digital video surveillance market
With the advancement of IC technology and the development of processor technology, DSP, RISC, and VLIW processors of three different technologies are gradually unified. Nowadays, multimedia processors incorporate three processor technologies.
SOC technology is developing very fast and VIDEO PROCESSOR is already very powerful. The video processor integrates many peripheral circuits including VIDEO IN UNIT, VIDEO OUT UNIT, AUDIO IN UNIT, AUDIO OUT UNIT, and some internal coprocessors. Such as variable-length encoder/decoder VLX, motion prediction ME, DMA controller, IIC controller, etc., the integration of these IP modules greatly enhances the processing power of VP. These VPs also appear under the name of DSP.
With the continuous improvement of DSP main frequency, the continuous enhancement of processing capacity, and the continuous progress of video coding technology, video compression software is developed on DSP to realize real-time video compression. Among them, it is very important to develop high-efficiency video compression software based on a general-purpose DSP platform with autonomous knowledge products. Our ability to develop general-purpose DSP is not enough. We have not enough capacity to develop dedicated video compression chips, but we can develop high-efficiency video compression software on general-purpose DSPs and add new ones according to the needs of monitoring market applications. The function. Due to the closedness of the surveillance market, video compression software can be unconstrained by standards, and it can absorb the latest video coding results in time to meet market demand and meet user requirements as the first goal. The dedicated video compression chip is designed for consumer use, emphasizing compatibility. Therefore, in order to meet the needs of the surveillance market, developing custom compression software on the video processor has the following features:
1, can not be limited by the standard, adopt the latest compression technology, in line with the characteristics of the monitoring market. For example, monitoring is a long time recording, and it requires high bit rates. Therefore, in video compression software, the first pursuit is a high compression ratio.
2. Remote monitoring emphasizes the functions of the network. The limitation of low network bandwidth leads to the requirement for low bit rate. Some applications require low latency on the network and require low latency. Therefore, the video compression software can implement different functions for different applications according to different application requirements: the target can be achieved at a low code rate, and the design goal can be low latency.
3, according to the change of the application situation and the environment, you can dynamically modify the encoding parameters in the compression process, such as image quality, frame rate, frame structure.
4. Video signal superimposition icons, character strings, etc. can be easily implemented, such as time information and location information.
5. In many monitoring situations, voice compression is also required. The general consumer chip supports voice compression. The voice bandwidth is much larger than the voice bandwidth (voice is within 3400 Hz, and the voice bandwidth is from 0-20 KHz). Voice compression can use G.729a, G.729, G.723, G.723.1, etc. The compressed bitstream is only 8Kbit/s, 6.3Kbit/s, 5.3Kbit/s, and the compressed voice stream has a minimum of 16Kbit/s. Generally speaking, it is more than 32Kbit. This is not a big difference for storage, but it is particularly important for transmission over narrowband.
6, support "watermark" technology, to prevent the record file is modified.
In short, developing its own compression software on the video processor, with its own intellectual property rights, according to the actual needs of the application to do the corresponding adjustment of the encoding software, the significance is particularly significant: no longer constrained by the compression chip, you can freely play. Software compression coding of video images on a video processor (DSP) is a strength of the Chinese people. The people of the country work together to seize opportunities and create national brands in the ever-growing area of ​​surveillance.
Third, the conclusion
Hangzhou Hikvision Digital Technology Co., Ltd. is a professional company engaged in the research and development of video and audio codec core technology, and the development and production of independent digital video and audio compression products, as the pioneer in the development of video encoding software on the domestic video processor (DSP). , On a variety of video and video processors (DSP) has been a very useful attempt, has made very significant progress, the current launch of the COIN DS-400XM and COIN DS-400XH two series of products, representing the monitoring class The development direction of digital video and audio coding products.