Streaming Media Technology Overview

Write in front

Always want to write a more comprehensive introduction of streaming media technology articles, but for various reasons, has been slow to pen. One reason is that the current online streaming media technology articles too much, from all aspects said, search can find a lot of professional information, so it is doubtful whether the need to write this thing still exists. Another reason is, really do not want to repeat some of the conceptual things, do not want to simple collation and excerpt, or want to really deep from the concept to the principle of careful introduction of this thing, so you need to grasp the technical and language standards, both to make readers feel relaxed and interesting, but also to let people read valuable things, I'm worried about whether I can grasp it well. In fact, two reasons are attributed to the non-confident performance.

But think about it, or should write something, after all, people can not spend every day in the busy, or should put some valuable things recorded just good, on the one hand is the collation of their own work, on the other hand is also regarded as a contribution to the open Network world, are still good. To say such a few digression, or the book to the Truth.

Development history

     streaming media first appeared in the late 90 's, in order to achieve the smooth playback of AV content under limited bandwidth conditions. We know that at that time the end user bandwidth is very small, general home or 56KPBS ~ 256Kbps Dial-up network, most of the enterprise access network is still around 2M, perhaps this is a little strange for most of the young people, and the reality is this. At that time, the coding technology has not appeared, resulting in the transmission of video on the network is more laborious, to tell the truth, at that time who said to be on the internet to watch video, is simply wishful. However, there are a number of high-tech pioneers to achieve this dream, because they clearly predicted from text to pictures and video is the trend of Internet development, although this forecast some early, the middle dead a large number of pioneers, but streaming media technology is constantly developing, a generation of technology updates, until today this way.

Streaming media technology around 2000 is dominated by three major vendors, with Microsoft, Macromedia and real,2005 Macromedia being acquired by Adobe. The three companies of the technology is not the absolute advantages and disadvantages, the basic is a level, application goals are the same, the application scale has not said which leading to where to go, after all, there are few people on the internet to watch video, whether domestic or foreign, in addition to watch a film on the internet to endure constant buffering, No one thinks it's a pleasure to watch video in that kind of network condition. In specific applications, Microsoft has always been that way, applauded not good, adobe with Flash Player occupies a little advantage, and real with the RM compression format has many users. No broadband users, no open technical specifications, no high-performance intelligent terminal, everything is useless, the three big companies so tepid toss, real in the process was first dragged to death.

Sometimes the turnaround is so fast, 2005 years later, it seems a short period of time, our bandwidth has widened, the popularity of smart phones, h.254 coding standards are soon accepted, the Internet video application spring finally came. Bandwidth more and more wide, mobile phone faster and more and more video content on the internet, YouTube, Youku and other domestic and foreign video content operations as the main web site springing up, watching video on the internet gradually from fashion to become a habit.

In this process, the streaming media technology is also changing dramatically. Microsoft's Windows Media streaming technology, due to technology closures and unresponsive, and can not cross-terminal issues such as elimination, although Microsoft has introduced Silverlight and IIS smooth streaming technology, but it does not help, ultimately nobody. With the advantages of the Flash Player, Adobe occupies the majority of the user market on the PC terminal. In the mobile terminal, the HLS streaming media technology standard made by Apple has become the biggest winner, due to its open technology, simple protocol, and full use of established technical standards, development and implementation is relatively simple, quickly accepted by all parties, not only Apple's own iOS system all support the standard, The Android system is also quickly used as a built-in streaming technology protocol for support. So now streaming media technology, the mainstream two are Adobe and apple,adobe Flash technology and Flash Player is the absolute backbone of the PC side, smart phones and pad and other mobile terminals on the most widely used HLS.

principle of technique and technique

Why is streaming media technology after so many years of development still have such a strong vitality, and constantly maintain a rapid renewal? This should start from the technical nature and application target of streaming media.

We know that streaming media technology (streaming media) technology is relative to the traditional download-Play technology (downloading). Download play is the convergence of two technology mechanically, a download technology, a play technology, download technology is only responsible for downloading, playing the technology is only responsible for playing, the two do not have any collaboration, the user must first download the file before playing the video, and then to play, if the file is large, The waiting process is upsetting, and few people are willing to wait. Download playback is a waste of network bandwidth and server computing resources, which is a boring technology, regardless of which part of the video you are viewing needs to download all the files.

Streaming media technology is a great way to solve these problems in download playback, is a completely different playback experience. First of all, streaming media technology to achieve a click-to-play, the user in the video playback no longer need to download the entire file, as long as the download of very little data can start playing, play to download which part of the video corresponding data, do not play not downloaded, watching video on the network and watching local video file response time almost no difference. Second, the user can also jump broadcast, you can drag the playback progress to any playback position, the progress bar dragged to where to start playback, and almost no waiting, that is, point-to-broadcast. Not only is the playback experience radically improved, but also the consumption of servers and bandwidth is greatly reduced, allowing servers and networks to serve more users and greatly improve concurrency responsiveness.

Streaming media technology is able to achieve point-and-click, on-Demand download, the essence of its technology is the server and player between the tacit cooperation. Under the guidance of the well-designed protocol standard, the server and player not only pass the video data, but also pass the play control instruction, such as play, pause, stop, jump (seek), etc. In this way, the player can send playback control instructions to the server based on the user's play request, and the server will send the appropriate data according to the needs of the player after receiving these instructions. In the streaming media technology system, this kind of transmission video audio data and control instruction protocol is called the streaming media protocol, the server is called the streaming media server, the player is called the streaming media player.

Currently, the widely used streaming media protocol has Adobe's rtmp protocol, Apple's HLS protocol, and Real's participation in the drafting of the RTSP protocol. The RTSP protocol is widely used in the field of surveillance, but few people use it in the field of Internet video applications. There is also a protocol, Microsoft's MMS protocol, although also smash hit, but now very few people use.

here the key to the HTTP protocol, we all feel that the HTTP protocol is the transmission of web pages and pictures of the Protocol, in fact, it is the most extensive streaming media transmission protocol! Due to the sophistication, simplicity and ability to traverse firewalls, more and more companies are starting to develop audio and video transmission and playback technologies on HTTP protocols, HLS, HTML5 video,http Pseudo-streaming use HTTP as the data sending protocol, most of the current Internet video is transmitted through the HTTP protocol. I will further explain the technical principles and implementation details of these protocols.

This article is from the "Streaming Media server technology Research" blog, please be sure to keep this source http://livestreaming.blog.51cto.com/3135568/1833109

Streaming Media Technology Overview