Zheng Yan from Shenzhen Radio and Television Transmission Center

Li Xin from Shenzhen Television Station

Summary: This article elaborates on the networking principles and related storage, compression, and management technologies of television station networking, discusses the main implementation links of networking, analyzes the technical essence of media asset management system, and combines the actual situation of Shenzhen Television Station to provide a comprehensive network planning scheme that integrates production, broadcasting, storage, and management services.

Keywords: video network media asset management, production, broadcasting, storage, networked SAN

1、 The significance of networking

The television industry is currently in a transitional stage of coexistence of analog and digital, single machine and network. The goal of television stations is to move towards digitalization and networking, but the implementation of networking also brings many confusions. Understanding the process of networking and exploring the connotation of networking has profound significance.

The technical system of a television station generally includes the main links of the studio, broadcasting vehicle, pre recording, post editing, editing and broadcasting, signal transmission, tape storage, and program retrieval and utilization. Some of these links have been digitized, but video tapes still serve as information carriers throughout all processes. Due to the wide variety of television equipment and systems and poor compatibility, multiple inputs and outputs of video tape programs are always difficult to avoid. In a lack of networked environment, it is inevitable that programs will be uploaded and downloaded multiple times on different systems, and multiple inputs and outputs will not only waste time but also cause significant loss in signal quality.

If the entire station is networked, programs can be stored on a shared hard drive at once, and video and audio programs can be transmitted through high-speed networks, completing multiple production processes and ultimately broadcasting. Networking has also expanded the channels for program exchange, allowing for the transmission of information from shared libraries through satellite and internet channels. Therefore, networking can avoid repetitive operations, improve the way programs communicate, and ultimately enhance the quality of video and audio technology.

Networking also provides conditions for high-level management of television stations. By relying on computer networks and large-scale database application systems, various business processes of the entire station are communicated with each other, achieving program production, broadcasting, column revenue and expenditure, channel accounting, user management, office automation, and other businesses in the network environment. This achieves the process, standardization, and high efficiency of management.

In summary, networking is the platform for media asset management systems, and at the same time, it has a broader extension than media asset management systems. Networking brings the following advantages:

● Improve the final visual and audio quality

Improve the process oriented mode of television production and broadcasting, and promote the integration of business across the entire station

● Expand channels for program and information exchange

Realize standardization and high efficiency in the operation and management of television stations

Networking will ultimately replace traditional magnetic tapes, reduce program storage costs, and improve their reuse value

2、 The networked process

Networking is deeply integrated into the main production and broadcasting processes of television. Networking includes the following important links, as shown in the attached figure:

1. Production system

The networking of production systems is aimed at solving the sharing of materials and semi-finished programs, avoiding multiple input and output of programs, which is mainly reflected in the networking of non-linear editing systems. The networked production system can achieve:

● Sharing of materials and semi-finished programs

The assembly line operation of editing, subtitles, special effects, animation, synthesis and other processes

Intelligent management of computer rooms

2. Broadcasting system

The networking of broadcasting systems is mainly manifested in hard disk broadcasting systems and automatic broadcasting systems, which are used to improve the quality of video and audio broadcasting and the degree of automation in broadcasting. The broadcasting system requires long-term multi-channel operation and is also the intersection of various video and audio signals and management control signals. Relying on manual management is difficult to ensure high efficiency and reliability of broadcasting. The networked broadcasting system reduces intermediate processes, improves technical quality, and also improves broadcasting safety.

3. Video and audio program storage system

The networked storage of programs is aimed at achieving concurrent online retrieval of program information across the entire station. The storage of television programs has long relied on magnetic tapes, which greatly affects the storage period and reuse of programs. Networking has brought fundamental changes to program storage. Currently, computer related technology is developing rapidly, and hard drives, data stream tapes, and optical discs have provided better availability, longer storage periods, and lower prices as storage media. In the future, traditional magnetic tapes will gradually disappear, and hard drives, data stream tapes, and optical discs will become the mainstream storage media for video programs.

Meanwhile, the program adopts a hierarchical storage system. Hard drives have high cost and fast speed, and are used to store programs that need to be produced or broadcasted within 10 days, known as online storage; Data stream tapes and CDs have a large capacity and slow speed, and are used to store other programs that are not needed in the near future, known as near line and offline storage. The online, near line, and offline storage systems extend the shelf life of programs and can be migrated to each other through the network. The networked storage of programs will make the retrieval and reuse of inventory programs extremely convenient, promoting the level of programs to a new level.

4. Taiwan wide management information system

A networked management information system is designed to achieve standardized and efficient management of various business processes and processes in television stations. The large-scale, multi-channel, and multi business operation of television stations has put forward higher requirements for management. It is urgent to use networked large-scale computer management information systems to carry out deep and diversified quantitative management of program production, broadcasting, column revenue and expenditure, channel accounting, user management, etc., in order to ensure the efficient operation of television stations and ensure that the mainstream business of television stations operates on a standardized, intelligent, and efficient framework.

3、 The implementation process of networking

Networking is built on the foundation of digitization. Only when digitization reaches a certain scale can networking have practical significance. In the current transitional era of digital analog mixing, the implementation of networking also needs to go through a process of development and improvement. Local networking can be piloted separately in production systems and broadcasting systems, namely implementing networked non-linear editing systems and hard disk broadcasting systems, while program storage still follows the traditional magnetic tape method. Subsequently, the connotation of local networking should be gradually extended and implemented in a certain subsystem. The most valuable one is the news production, broadcasting, and storage system, because news has strong timeliness, frequent access to historical materials, and high requirements for resource sharing and rapid operation, which can best reflect the significance of networking. At the same time, the completion of news is very short, with low requirements for editing, strong operability, and lower costs. At present, the news collection, recording, production and broadcasting integrated network constructed using SAN technology has been promoted and applied in foreign television stations.

When local networking is implemented to a certain stage, comprehensive networking emerges, and comprehensive networking will promote the withdrawal of traditional magnetic tapes from the stage. If the television station already has a good foundation in digitalization and local networking, the following steps need to be taken to complete the networkization of the entire station:

Expand network bandwidth and extend the network to all relevant departments, columns, and research groups

Add storage capacity for online, near line, and offline systems, and integrate video and audio storage systems with production and broadcasting systems into one

Develop new large-scale video and audio operation software, transplant the core production, broadcasting, storage, and retrieval services of all channels and columns in the entire station to the video and audio network, and promote the networked production and broadcasting processes of programs

Establish a large-scale management information system that runs through every corner of the entire station, achieving comprehensive computer management of television stations

4、 Networked video compression format

The digital compression format is the primary issue of networking. The higher the compressed bitstream, the better the image quality, but it also occupies a large storage space and consumes a lot of network bandwidth. Generally speaking, the broadcast level compressed bitstream can be selected between 6M-50M, and the retrieval level compressed bitstream can be selected between 300K-1.6M. At present, the coexistence of different compression technologies has brought great difficulties to the unified operation of networking. The television industry has a wide range of compression formats, with the most common being file based MXF and AAF video compression formats such as M-JPEG, MPEG-1/2/4, DV, and SONY. M-JPEG is a compression algorithm based on frame by frame content, making it particularly suitable for precise frame editing; MPEG-1/2/4 provides a very high compression ratio, including both inter frame and intra frame compression; The DV format is divided into MINI DV, DVCPRO, and DVCAM, which are also encoding techniques based on intra frame compression, so they can also support precise frame editing. In general, production uses MPEG2 I frame and M-JPEG encoding, broadcasting uses MPEG2 IBP frame encoding, and retrieval uses MPEG1/MPEG4 encoding.

MPEG is the most important compression format for networking, as it has high compression efficiency and can meet the needs of various fields such as signal acquisition, transmission, production, archiving, broadcasting, and distribution. The mainstream formats of MPEG include MPEG1, MPEG2, and MPEG4, where MPEG1 and MPEG4 are commonly used for low-quality video compression with low bitstreams, and MPEG2 is used for broadcast level video compression. MPEG2 is further divided into intra frame compression of I-frames, IB frames (short GOP frames), and IBBP frames (long GOP frames). The different bit rates and frame structures of MPEG2 are not directly compatible and must be transcoded. The temporal requirements for transcoding are high, and there is currently no satisfactory technical support. The compromise transcoding method is to decompress the compressed data into a baseband signal, and then compress it into the desired format. This transcoding will result in a decrease in image quality.

Networking must avoid multiple compression/decompression of videos. Based on current technological analysis, it is appropriate to choose MPEG2's I frame encoding as the mainstream format for storage and production. The bitstream can be selected between 20M-50M based on image quality, which can facilitate the integration of program storage and production. As for the broadcast of the program, using MPEG2 I frame encoding is not appropriate, and using MPEG2 IBP long frame encoding would be more appropriate. The completed film needs to be transcoded before being broadcasted. Currently, the transcoding time is still long and the effect is not ideal. We believe that mature and efficient transcoding technology will be available in the future.

A promising approach in the future is through file level interconnection. SONY has introduced MXF and AAF file formats using MPEG2 compression with the IMX series cameras, which can transfer MPEG files from servers to another server through high-speed networks.

From:<<Modern Television Technology>>