Conversion and Application of Broadcasting Technology in Video Surveillance System
As IP high-definition monitoring has gradually become the development trend of security, more and more monitoring equipment and management systems have more intersections with the radio and television field in terms of reference coefficients, applications and functions. The high-definition, network, openness, and intelligence that security is currently experiencing cannot be discussed without these capabilities in the broadcast and television field. This article takes the application of ASMF system technology, intelligent transition identification technology, and MSB technology in the security industry as an example to discuss the development trend of radio and television technology in the security industry, so as to provide reference for the industry.
In the past two years, the security industry has developed rapidly. The "Safe China", "Safe City" and the hosting of the Olympic Games have injected vitality into the development of China's security industry. It has also provided opportunities for the rapid development of China's security industry and enterprises, and has driven security. The rapid development and improvement of technology. The development in recent years shows that the general trend of security technology is to make great strides in the direction of high-definition, intelligence and networking. In the field of radio and television, through years of development, high-definition production and broadcasting, intelligent image analysis and network-wide technology have become very mature and have been widely used in various television stations.
ASMF high bit rate can meet the needs of high-definition security
Initially, the concept and standard of "high-definition" were proposed by the broadcast and television industry. There are three main standards: 720P, 1080i, 1080P, the aspect ratio of which is defined as 16: 9. 720P is 1280 & TImes; 720 resolution, 1080i and 1080P are 1920 & TImes; 1080 resolution, suffix "i" and "p" respectively Indicates interlaced scanning and progressive scanning. Among them, 1080P is the highest level of high-definition video definition standard. For image acquisition of fast-moving targets, progressive scanning can obtain better dynamic images than interlaced scanning. Interlaced scanning will produce image shaking. The most commonly used encoding formats for high-definition video encoding are MPEG-2, MPEG-4, H.264 and VC-1. Compared with MPEG-2 and MPEG-4, H.264 has the highest compression efficiency among the three encodings. (see picture 1)
Coding structure
High-quality, high-efficiency codec is the key to high-definition image processing, and the technology that can simultaneously support efficient full-format frame accurate codec is a necessary condition for building high-definition security systems. In the radio and television, different bit rates are used according to the content of high-definition programs. For example, low-end news and education programs use a lower bit rate of 18Mbps, while high-end program production, including TV shows and sports, generally use 200Mbps. Code rate. Compared with the high-definition code rate of 4Mbps to 10Mbps of security, the broadcast and television program production system's real-time processing requirements for the encoding and decoding of high-definition images far exceed the requirements of the security high-definition system.
We know that the data stream of MPEG series compression and preservation is mainly composed of a group of pictures (GOP) composed of I, B, and P frames. Only I frames are full frames (reference frames), and B and P are predicted frames. During the stream playback, if you directly switch the code stream, you must wait until the I frame arrives, which creates a delay, the delay time depends on the length of the group of pictures (GOP). Does it not need to use I-frames as an entry point to achieve accurate arbitrary frame playback and retrieval? This is possible. In the non-linear editing system of radio and television, accurate frame playback and fast continuous search are realized. During playback and search, You can see each frame smoothly, and can stop at any frame (I, B, P frame) accurately, you can search frame by frame, and you can also achieve accurate fast continuous playback and frame by frame search. Similarly, for H.264 and MPEG-4 compression formats, precise frame positioning with millisecond response is also achieved. In the field of security, currently, only second-level search positioning is achieved.
As we all know, high definition means high bit rate. How to take into account the requirements of high security, high real-time, and high performance when implementing high bit rate data storage? To solve this problem, we need to start with the file format. MXF is the acronym for English Material Exchange Format. MXF is designed to package MPEG-2 data streams, DV data streams, YUV data streams, PCM audio files, and database files in several formats (synchronous or asynchronous mode). MXF can process audio, video and database files of multiple tracks at the same time. It is designed to support both streaming and file transmission. MXF is widely used in professional broadcast and television environments. Combining the characteristics of high-definition stream data for security monitoring, we have designed a format dedicated to high-definition image storage based on MXF, called Advanced Security Media Format Abbreviated as ASMF.
The file is composed of file header, file body and file tail. As the beginning of the file, the file header contains the basic structure information such as the number of audio and video tracks and time length of the file. The file body is used to store information such as video and audio data and the corresponding index. And metadata information, at the same time can be used to determine whether the update information is available.
ASMF is completely independent of the operating system, reads and writes directly to the disk, has extremely high I / O read and write performance, and fully meets the read and write requirements of high-definition systems. The intelligent disk I / O scheduling algorithm can effectively avoid disk read and write "conflicts". The distributed real-time backup of ASMF RAID can provide data security greater than RAID0 + 1, ensuring that the data is not affected if the disk is accidentally damaged. (See Figure 2)
File system format
At the same time, ASMF files support the aggregation and storage of video and audio data for channels and multiple different time segments. Makes the association between various audio and video clips more logical. For example, we can store scenes recorded by several cameras related to a case, and the fragments corresponding to several involved persons are all stored in the same file, and related event information, scene description information, and key paragraph information (MetaData) As auxiliary and descriptive information is also saved in the ASMF file, so that the data use process has better access performance and more convenient and efficient extraction and operation.
The ASMF file format supports efficient access to content and fast "frame-accurate" positioning. Support multi-layer, distributed, pyramid-type super index mode, and use layer-by-layer segmented query access when positioning, which can quickly and accurately determine any frame and video segment in the file without analyzing the entire index, greatly improving the file Positioning and response.
The application of intelligent transition recognition technology in security
On the other hand, the unique intelligent transition identification technology in the field of radio and television can also be used in security systems. The transition is a transition or transition between video scenes and scenes. For example, when reporting on a company, the last shot of the previous scene was a product shot in the enterprise, and the next shot was a product shot in the market, and the report was transferred from the workshop. Stores have shifted from production to sales, and the conversion of this scenario is called a transition in the field of broadcasting. At that time, this intelligent identification technology for transition was mastered by foreign manufacturers. Later, domestic manufacturers mastered the core technology of transition identification through independent research and development.
Through the intelligent identification technology of transition, the stored material can be divided into shots according to the transition, and a sub-shot list of the material can be automatically generated, and fast sub-lens positioning can be provided. In terms of purpose, the goals of intelligent transition recognition and security motion detection and recognition are the same. Both recognize different scenes by detecting changes in the image of the image, but the intelligent recognition technology of transition is a more advanced video analysis technology. The recognition accuracy is higher. And based on the transition intelligent recognition technology, it can further realize the detection of the black field, color bars, and snowflakes of the image. These technologies can be used to detect the working state of the camera in the security system and become a technical means for automatically detecting the working state of the camera image system.
In the field of radio and television, the sports program production department often produces a highlight of football shooting. Previously, through the production staff to browse the football game video data one by one, the highlights of the clips were edited together, which is very time-consuming and very inefficient. Later, radio and television equipment manufacturers have developed an intelligent algorithm for football highlight analysis, which can automatically analyze the football shots in the video and automatically edit these shots into a short film. The producer only needs to make simple adjustments to the edited short film. Broadcasting greatly shortened the program production cycle. The intelligent algorithm for football exciting analysis here is actually the video intelligent algorithm mentioned in the field of security. It can accurately identify the wonderful shots by shooting the parameters such as the crowd density in the picture, the speed of the football, the characteristics of the goal, and the color of the goalkeeper ’s special clothing. .
In addition to the intelligent analysis of images based on video, the radio and television also has an intelligent analysis technology of voice, which is mainly used to analyze the announcer's voice and automatically align the subtitles below the screen through voice recognition. In the field of security, this technology can be applied to the identification of abnormal sounds in the monitoring environment, such as explosions, gunshots, and calls for help.
The advantages of MSB in the field of network video surveillance
At present, with the development of network video surveillance, video surveillance has begun to penetrate into new application fields such as road traffic, enterprise informatization, family, education, and medical treatment. Network video surveillance has unique advantages. Compared with analog and digital surveillance technologies, network video surveillance utilizes a TCP / IP network, enabling remote monitoring and low-cost expansion of the monitoring range. However, we should also see that the current security network focuses on the networking of multiple monitoring subsystems, and the combination of monitoring and related services and work processes is still relatively small. In this regard, the technical architecture of the MSB (Media Service Bus, see Figure 3) high-definition full station network in the field of broadcasting and television is well integrated with the user's business and processes. Through the application of CCTV and the Olympic Games, The good effect is very worthy of reference for the majority of security manufacturers when designing video surveillance systems.
HD system structure diagram
In the field of broadcasting and television, MSB is based on the characteristics of the industry, based on SOA as the technical theoretical basis, combined with a variety of development technologies and protocol specifications, and is used as the core architecture for the informatization construction of TV stations. MSB is divided into two parts: architecture and protocol specifications. Architecturally speaking, MSB is a basic platform and business integration goal for the broadcasting and television industry and multimedia-related applications in various industries. Taking SOA ideas as a blueprint, it has absorbed advanced concepts such as ESB and BEPL in SOA. It has all the core advantages of SOA system loose coupling, protocol conversion, routing, process definition, etc .; supports media bus functions. Realize the loose coupling, format conversion, routing and exchange functions of media files; realize the interconnection of multiple subsystems with the idea of ​​"service" as the main idea. From the perspective of protocol specifications, MSB uses XML schema to gradually define a set of business specifications based on the typical service abstractions of TV stations; the "services", "interfaces", and "parameters" express the business specifications.
The main functions defined by each module are as follows:
· System resource registration: realize the registration and storage of standard service categories, technical system categories, communication address and other parameters provided by each system
· Protocol conversion intermediary: Using the "technical implementation irrelevant business specifications" as a guideline, the format conversion of business protocols encapsulated by different technologies is realized. It can further realize the conversion of standardized content;
· Media processing intermediary: realizes the interface between media migration, format conversion, media analysis and other functions;
· Information bus: a logical link that carries metadata communications;
· Business specification: Completed the establishment of a business specification basic framework that has nothing to do with technology implementation, and gave XSD definition that has nothing to do with protocol encapsulation;
· Media bus: A logical link that carries the flow of media files;
· Business monitoring and management services: provide service interfaces for obtaining system service status registered on the bus, browsing system operation logs, and interfering with service operation status;
· Business process definition service: provides a service interface that sets policies according to users and defines the service execution process among several systems.
From a macro perspective, MSB is a bus structure, and other business systems are plugged into the bus through a service interface layer. From the overall concept, it is more like a passive industrial control computer motherboard, which resides some basic configuration modules and routing modules. The business system is connected to interfaces of different specifications through standard plug-in parts.
In general, the relevant technologies in the field of radio and television have great portability in the field of security, and provide a new idea for the construction, integration and development of security systems. On the one hand, we can adopt the doctrine of using advanced technology in the field of radio and television to the construction of security systems. On the other hand, we must also make technological innovations based on the characteristics of security to jointly promote the advent of the era of intelligent high-definition surveillance.
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