IPTV system based on streaming media technology
With the popularization of the Internet, the demand for using the network to transmit audio and video signals is increasing. After media such as radio and television go online, they all hope to release their own audio and video programs through the Internet. However, the volume of files in the storage of audio and video is generally very large. When the network bandwidth is still very limited, it is a headache to spend tens of minutes or even longer waiting for the transmission of an audio and video file. The emergence of streaming media technology has improved the difficulty of audio and video transmission over the Internet to a certain extent. Streaming media technology originated in the United States, and the application of streaming media in the United States is now common. For example, HP's product launches and sales staff training are all conducted with online video. Unlike traditional playback methods, streaming media does not download the entire file before playing, but only caches part of the content, so that the streaming media data is transmitted and played while streaming, which saves download waiting time and storage space. Network TV came into being by combining the characteristics of streaming media technology. It can adapt to the rapid development trend of today's network and make full and effective use of network resources. Therefore, the development of Internet TV is inseparable from streaming media technology. This article focuses on the application and development of Internet TV based on streaming media technology.
1 Streaming media technology
1.1 The principle of streaming media technology
Streaming media is also called streaming media. It refers to businesses that use a video delivery server to send out programs as data packets and deliver them to the network. After the user decompresses the data through the decompression device, the program will be displayed as before transmission. A series of related packages in this process is called a "flow". Streaming media actually refers to a new media delivery method, not a new media. After the full application of streaming media technology, people can directly voice input in online chat; if you want to see each other’s face and expression, as long as both sides have a camera; if you see the product of interest on the Internet, click it, the explainer The video of the product and the product will pop out; more realistic video news will also appear.
If the file transfer is regarded as a process of receiving water, the past transfer method is like a rule for users. You must wait until a bucket of water is full before you can use it. This waiting time is naturally affected by the size of the water flow and the bucket. The size of the impact. The streaming method is to turn on the tap, wait a short while, the water will flow out continuously, and it can be used at any time. Therefore, regardless of the size of the water flow or the size of the bucket, the user can Use water at any time. In this sense, the term streaming media is very vivid.
The implementation of streaming requires caching. Because the Internet performs intermittent asynchronous transmission based on packet transmission, for a real-time A/V source or stored A/V file, they must be broken down into many packets during transmission. Because the network changes dynamically, each packet is selected. The route may be different, so the time delay to reach the client is also different, and even the first data packet may arrive later. To this end, a cache system is used to compensate for the effects of delay and jitter, and to ensure the correct sequence of data packets, so that the media data can be output continuously without pauses in playback due to temporary network congestion. Usually the cache capacity is not large, because the cache uses a circular linked list structure to store data: by discarding the content that has been played, the stream can reuse the free cache space to cache the subsequent unplayed content. The realization of streaming requires a suitable transmission protocol. Because TCP requires more overhead, it is not suitable for transmitting real-time data. In the implementation of streaming, HTTP/TCP is generally used to transmit control information, and RTP/UDP is used to transmit real-time sound data. The process of streaming transmission is generally as follows: After the user selects a streaming media service, the Web browser and the Web server use HTTP/TCP to exchange control information, so that the real-time data that needs to be transmitted can be retrieved from the original information; then the client The web browser on the machine starts the A/VHelper program, and uses HTTP to retrieve the relevant parameters from the Web server to initialize the Helper program. These parameters may include directory information, A/V data encoding type or server address related to A/V retrieval.
It should be noted that in streaming transmission, two different communication protocols, RTP/UDP and RTSP/TCP, are used to establish contact with the A/V server in order to redirect the output of the server to a different one from running A/V. The destination address of the client where the Helper program is located. Realization of streaming transmission generally requires a dedicated server and player, the basic principle of which is shown in Figure 1.
1.2 The realization process of streaming media technology
The streaming media system includes the following five aspects:
(1) Coding tools: used to create, capture and edit multimedia data to form a streaming media format.
(2) Streaming media data.
(3) Server: Store and control streaming media data.
(4) Network: A network suitable for multimedia transmission protocols and even real-time transmission protocols.
(5) Player: For the client to browse streaming media files.
Some of these five parts are required by the website, some are required by the client, and different streaming media standards and solutions of different companies will be different in some respects.
When using streaming media technology, audio and video files should adopt corresponding formats, and files of different formats need to be played with different player software. The so-called "a key opens a lock". Currently, audio and video files using streaming media technology mainly have three major "genres", namely RealMedia from RealNetworks, Windows Media from Microsoft, and QITIckTIme from Apple.
According to the method of content submission, streaming media can be divided into two types: live streaming media broadcast (ie, Web broadcast) and archived video and audio that are accessed by users on demand. Regardless of the type of streaming media, it takes a certain process from filming the original footage to the playback of the media content. The following takes RealMedia as an example to illustrate the process of making, transmitting and using streaming media:
(1) Use a video capture device to record the event.
(2) Edit the acquired content, and then use video editing hardware and software to digitally process it.
(3) The digitized video and audio content is encoded into a streaming media format.
(4) The media files or live data streams are saved on the host computer where the streaming media server software is installed.
(5) The user clicks on the web page to request a video stream or access the database of the stream content.
(6) The host server submits digital content to the end user through the network.
(7) The end user uses the playback program that displays the media content on the desktop or mobile terminal to play back and watch.
Because streaming media technology has broken through the limitation of network bandwidth to the transmission of multimedia information to a certain extent, it is widely used in online live broadcasting, online advertising, video-on-demand, distance education, telemedicine, video conferencing, corporate training, e-commerce, etc. field.
2 The main solution of streaming technology
Due to its mature and stable technical performance, Internet giants such as America Online (AOL), ABC, AT&T, Sony and TIme Life and other major online radio stations use RealSystem to deliver real-time audio-visual media information and real-time music broadcasts to all parts of the world. In my country, a large number of movies, music on demand, and online live broadcasts of the Spring Festival Gala and the opening ceremony of the Kunming World Expo all use the RealSystem system.
Windows Media Technology is an information streaming program proposed by Microsoft. Its main purpose is to realize the transmission of multimedia streaming information including audio and video information on the Internet and Intra-net. Its core is the ASF file. ASF is a data format that contains multimedia information such as audio, video, image, control commands, scripts, etc., which is transmitted over the Internet by dividing into individual network data packets to realize streaming multimedia content publishing. Therefore, the content transmitted on the network is called ASF Stream. ASF supports arbitrary compression/decompression coding methods, and can use any underlying network transmission protocol, which has great flexibility. Microsoft has bundled Windows Media technology into Windows 2000 and intends to use ASF as the standard file format for multimedia content in future versions of Windows. This will undoubtedly have a significant impact on the Internet, especially the application and development of streaming technology.
Windows Media Technology is composed of Media Tools, Media Server and Media Player tools. Media Tools is an important part of the entire program. It provides a series of tools to help users generate multimedia streams in ASF and formats. They are divided into creation tools and editing tools. The creation tools are mainly used to generate multimedia streams in ASF format, including Media. Encoder, Author, VidToASF, WavToASF, Present-ter five tools; editing tools mainly edit and manage multimedia stream information in ASF format, including post-production editing tools ASF Indexer and ASFChop, as well as check and correct errors in ASF streams ASF-Check. Media Server can guarantee the confidentiality of files, not to be downloaded, and enable every user to browse the web with the best video quality, and has a variety of file release forms and monitoring and management functions. Media Player provides powerful streaming information playback function.
Apple began to release QuickTIme in 1991. It supports almost all mainstream personal computing platforms and various formats of static image files, videos and animation formats. It has built-in Web browser plug-in technology, supports IETF streaming standards and RTP, RTSP, SDP , FTP and HTTP and other network protocols. Many new movie clips retrieved through Hollywood Studios are stored in QuickTime format.
QltickTime includes a server, QuickTime Player with editing functions, a producer, an image browser, and a QuickTime plug-in that enables an Internet browser to play QuickTime movies. QuickTime 4 supports two types of streaming: real-time streaming and quick-start streaming. QuickTime movies that use real-time streaming must be played from a server that supports QuickTime streaming. It is a real Streaming Media and uses Real-Time Transport Protocol (RTP) to transmit data. Quick start movies can be played from any Web Server, using Hypertext Transfer Protocol (HTTP) or File Transfer Protocol (FTP) to transfer data.
Currently, FOX News Online, FOX Sports Online, BBCWORLD, Weather Channel and other institutions have joined the ranks of QuickTime content providers, using QuickTime technology to produce live broadcast programs. In addition to the three main formats of the above-mentioned streaming media technology, in terms of multimedia courseware and animation The streaming media technology of Macromedia also includes Shock-wave technology of Macromedia and Meta Stream technology of MeataCreation company.
Through Shockwave technology, operations such as images, animations, and interactive interfaces can be easily added to Web pages. With this kind of Streaming Shockwave, the user can realize the function of downloading and playing on the client side by means of streaming, which saves the waiting time. Shockwave and Macromedia products are closely linked, including Flash, Shockwave for Authorware, Shockwave for Di-rector and other technologies.
The graphics design software of MetaStream 3D is Ray Dream studio 5 and Ray Dream 3D, which can easily create, publish and browse zoomed 3D graphics on the Internet. It has the characteristics of small file size and streaming, which is more existing than any other kind. All Internet 3D technologies have high compression rates. Mainly used in game developers, page designers, e-commerce, scientific researchers, professional designers, etc.
3 Application of Streaming Media Technology in Internet TV
At present, my country's communications industry is developing rapidly, and users are increasingly demanding information services, especially broadband video information. It can be said that China has basically possessed the technical and market conditions for vigorously developing IPTV, and the competition in the IPTV network TV market is becoming increasingly fierce. Market competition is more beneficial to ordinary consumers. Regardless of this, the concern here is how to realize network TV. For general users, network set-top boxes + ordinary TV sets are generally used. As shown in Figure 2, the computer and the set-top box share an ADSL Modem for broadband Internet access. Usually ADSL user's computer and ADSL Modem are in the same place, therefore, ADSL Modem leads to Category 5 network cable to connect to the set-top box. Considering that most ADSL Modem has only one 10BaseT network port, one more HUB should be added. Internet TV can provide services such as distance education, video-on-demand, web live broadcasting, and video conferencing, making people's lives more colorful. The following will discuss the application of streaming media from these aspects.
3.1 Distance education
The popularization of computers, the development of multimedia technology and the rapid rise of the Internet have brought new opportunities to distance education. Countries all over the world are vigorously developing distance education including online education. In the process of remote teaching, the most basic requirement is to transfer information from the teacher to the remote student. The information that needs to be transferred may be diversified, including various types of data: such as video, audio, text, and pictures. Wait. Passing these materials from one end to the other is a problem that distance education needs to solve, and how to effectively combine these information materials to achieve better teaching effects is an important aspect of people's thinking. Due to the limitation of current network bandwidth, streaming media is undoubtedly the best choice. Students can participate in remote teaching through a computer, a telephone line, and a modem at home. For teachers, there is no need to do too much preparation. The teaching method is basically the same as the traditional teaching method, except that the camera and the computer are faced.
At present, most of the technologies that can be used for multimedia interactive teaching on the Internet are streaming media, and technologies such as RealSystem, Flash, and Shockwave are often used in network teaching. Distance education is a revolution to the traditional education model. It integrates teaching and management, breaks through the limitations of traditional "face-to-face instruction", and provides convenience for learners in terms of space and time.
In addition to real-time teaching, the use of VOD (Video on Demand) technology in streaming media can also achieve the purpose of teaching students in accordance with their aptitude and interactive teaching. Students can also share their learning experience and results through the Internet. Large enterprises can use streaming technology-based distance education systems as a means of training employees. Not only video and audio can be used here, but also graphics captures from computer screens can also be streamed to students. Now Microsoft itself uses a large number of its own streaming technology products as a means of training and communicating with employees in its global branches. With the development of network and streaming media technology, more and more distance education websites begin to adopt streaming media as the main online teaching method.
3.2 Broadband network video on demand
VOD video-on-demand was mentioned in the previous distance education. Video-on-demand technology is not a new concept. The original VOD was applied to karaoke on-demand. At that time, the VOD system was semi-automatic and required manual participation. With the development of computers, VOD technology is gradually applied to local area networks and cable television networks. At this time, VOD technology is becoming more and more perfect, but there is a difficulty that hinders the development of VOD technology, that is, the huge capacity of audio and video information. In this way, the server side not only requires a large amount of storage system, but also loads a large amount of data transmission, which makes the server unable to perform large-scale on-demand. At the same time, due to the small coverage of VOD in the local area network, users cannot listen to or watch programs in the local area network through network media such as the Internet. At this time, the emergence of streaming media technology can completely abandon the local area network and use the Internet in terms of video-on-demand. Because the streaming media has undergone special compression coding, it is very suitable for transmission on the Internet. The client uses a browser for on-demand broadcast, basically no maintenance. Due to the advanced cluster technology, large-scale concurrent on-demand requests can be processed in a distributed manner, making it suitable for large-scale on-demand environments.
With the development of broadband networks and information appliances, streaming media technology will be more and more widely used in video-on-demand systems. Perhaps one day you can also enjoy streaming video programs equivalent to TV programs in your own home. At present, many large-scale news and entertainment media provide streaming technology-based audio and video programs on the Internet, such as foreign CNN, CBS, my country’s CCTV, Beijing TV, etc. Some people broadcast this on the Internet. The program is called "Webcast".
3.3 Internet live broadcast
Perhaps everyone has only heard of terms such as live broadcasting and satellite broadcasting. They are not very familiar with the concept of Internet broadcasting (or web broadcasting). With the popularity of the Internet, more and more netizens are watching directly from the Internet. Sports events, major celebrations, and trade exhibitions have become the wishes of many netizens. Many manufacturers hope to spread their products and activities all over the world by means of live webcasts, which may not be achieved by any kind of media. All this contributed to the formation of Internet live broadcast. However, the problem of network bandwidth has always plagued the development of Internet live broadcast. However, with the continuous popularization of broadband networks and continuous improvement of streaming media technology, Internet live broadcast has moved from the experimental stage to the practical stage, and can provide more satisfactory audio and video effects. Streaming media technology plays an important role in Internet live broadcast. First, streaming media realizes the provision of high-quality audio and video in a low-bandwidth environment. Secondly, smart streaming technologies like Real's SureStream can ensure that users with different connection rates can get different quality audio and video effects. In addition, Streaming Media's Multicast (multi-address broadcast) technology can greatly reduce the load on the server side, while saving bandwidth to the greatest extent. Regardless of technical considerations or market considerations, Internet live broadcast is now the most mature of many streaming media applications. Many companies already provide live webcast services, and the annual "Spring Festival Gala" provides live webcasts.
3.4 Video conference
There are many video conferencing systems on the market, and these products basically support the TCP/IP network protocol, but the systems that use streaming media technology as the core technology do not account for the majority. Video conferencing technology involves multiple technologies such as data collection, data compression, and network transmission. Streaming media is not a necessary choice for video conferencing, but the emergence of streaming media technology has played a very important role in the development of video conferencing. Using streaming media format to transmit video and audio, users can watch continuously in real time without waiting for the transmission of the entire movie. This not only improves the waiting problem before watching, but also achieves real-time effects. Although some picture quality is lost, as far as video conferencing is concerned, high audio and video quality is not required. Video conferencing is a commercial use of streaming media. Point-to-point communication can also be carried out through streaming media. The most common example is videophone. As long as there is a computer connected to the Internet and a camera, you can communicate with people anywhere in the world in audio and video. In addition, large enterprises can use streaming technology-based video conferencing systems to organize cross-regional meetings and discussions, thereby saving a lot of expenses. A practical example is that the second largest securities dealer in the United States has adopted the streaming technology solution provided by Starlight Network since 1998 to provide real-time information to its branch brokers and investment consultants in more than 500 cities and regions around the world. Desktop financial news enables their customers to obtain more investment profits.
4 Conclusion
With the continuous development of network communication, IPTV is bound to become a development trend. Streaming media technology is one of the key technologies of IPTV, and its development and application have attracted much attention. Although there are many similarities between the streaming media service system and the traditional network file service system, the streaming media technology emphasizes the access support for high-speed, stable and borderline search streams, as well as the support for the synchronization of different media, so as to ensure The media data arrives with minimal delay and is played back synchronously on the local terminal. Because the current streaming media service system has strict requirements for continuity, real-time, and a huge amount of data, the current stage of the network is still somewhat avoidable. With the further development of computer networks, the continuous expansion of network bandwidth, and the continuous improvement of network multimedia platforms, streaming media technology will certainly play a greater role in future network applications. Just as the original image processing requirements have affected computers, it is foreseeable that streaming media service systems will also have a major impact on the hardware and software design of networks and terminals.
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