Shulou(Shulou.com)06/02 Report--

The rapid commercialization of videoconferencing systems around the world is related to its standard setting. The International Telecommunication Union (ITU) and the International Organization of Engineers (IETF) formulate international standards for the video conference industry. By limiting the scope of video conference voice, video, digital signal coding format, user control mode and other elements, it not only provides a relatively unified technical specification for video conference, but also provides a solid foundation for the global application of video conference system today.

ITU-T standard era

The International Telecommunication Union (ITU-T) proposed and implemented the H.320 protocol in 1990, which is the first international standard protocol for video conferencing in the world, which is mainly used in group video conferencing on ISDN.

H.320 is a set of standards, which includes the compression and decompression of video and audio, still image, multipoint conference, encryption and so on. It is mainly used in the design of system terminal and MCU. H.320 standard contains more than H.200 and T.120 series standards, in which H.200 series refers to audio-visual services, specifically, communication services based on the transmission of moving images. T.120 series is mainly aimed at audio-visual services, that is, communication services that transmit still images.

Since then, H.323 protocol, which was born in 1997, is one of the mainstream standard protocols in the market, which mainly serves the hardware-based video conference system and provides multimedia communication standards for the existing packet network PBN (such as IP network). The mainstream video conference hardware products in the early market are compatible with H.320 protocol and H.323 protocol. The H.323 standard is established to allow multimedia products and applications from different manufacturers to interoperate. For a wide range of multimedia communication applications based on IP network, H.323 standard is a very important component. In addition, the standard also allows direct connection to PPP-based networks through ISDN and POTS. The H.323 standard covers the communication standards of audio, video and data over IP packet-based networks-LAN, INTRANET, EXTRANET and INTERNET.

Based on the agreement under the international standard, the terminals and MCU produced by the mainstream video conference manufacturers in the market can be interconnected, which realizes the basic requirements of unified market connectivity for the video conference system industry, and is conducive to the interconnection and integration of products in all markets, which has a great impact on the video conference system market.

MPEG-4 standard era

The MPEG4 standard is formulated by ISO (International Organization for Standardization) and IEC (International Electronic Committee).

MPEG-4 is an international standard for the integration and compression of digital television, interactive drawing applications (audio-visual content), interactive multimedia (WWW, data capture and dispersion) and other integration and compression technologies. The MPEG-4 standard integrates many multimedia applications into a complete framework, which aims to provide standard algorithms and tools for multimedia communication and application environment, so as to establish a unified data format that can be widely used in multimedia transmission, storage, retrieval and other application fields.

MPEG-4 standard has three characteristics: "content-based interaction, efficient compression, general accessibility". Based on these characteristics, the current mainstream software video conference systems in the market basically adopt this technical standard. Compared with other standards, MPEG-4 standard has higher compression ratio, less storage space and better image quality. it is especially suitable for transmitting video under low bandwidth and can maintain image quality.

H.264 standard era

H.264 is proposed jointly by International Organization for Standardization (ISO) and International Telecommunication Union (ITU). This standard is a new generation of digital video compression format after MPEG4.

H.264 is one of the video codec standards named after H.26x series by ITU-T. This standard combines H.263 protocol and MPEG-4 protocol in H.323 protocol, and solves the problem that there is no way for terminals based on software video conference MPEG-4 to be compatible with H.323 protocol, making it the best video compression protocol at present.

The main advantages of H.264 are as follows: 1. Compared with compression techniques such as MPEG2 and MPEG4 ASP, under the same image quality, the amount of data compressed by H.264 technology is only MPEG2's 1 prime 8 MPEG4's 1 prime 3. High-quality images can provide continuous, smooth and high-quality images. 3. Strong fault tolerance, providing a necessary tool to solve packet loss and other errors that are easy to occur in unstable network environment. 4. The network has strong adaptability.

Among these characteristics, it is especially worth mentioning that H.264 not only has a high compression ratio, but also has a high quality and smooth image. because of this, the video data compressed by H.264 requires less bandwidth in the process of network transmission. it is also more conducive to cost control for users.

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