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分类： LINUX
2012-06-30 07:59:50
If you are interested in any of the following:
Streaming audio or video to iPhone, iPod touch, iPad, or Apple TV
Streaming live events without special server software
Sending video on demand with encryption and authentication
you should learn about HTTP Live Streaming.
HTTP Live Streaming lets you send audio and video over HTTP from an ordinary web server for playback on iOS-based devices—including iPhone, iPad, iPod touch, and Apple TV—and on desktop computers (Mac OS X). HTTP Live Streaming supports both live broadcasts （直播）and prerecorded content (video on demand)（预先录制，点播）. HTTP Live Streaming supports multiple alternate streams at different bit rates（不同比特率的多个可选择的流）, and the client software can switch streams intelligently as network bandwidth changes.（当网络带宽变化的时候，客户单软件可以在多个流间智能切换） HTTP Live Streaming also provides for media encryption and user authentication over HTTPS, allowing publishers to protect their work.
All devices running iOS 3.0 and later include built-in client software for HTTP Live Streaming 内建客户端软件. The Safari browser can play HTTP streams within a webpage on iPad and desktop computers, and Safari launches a full-screen media player for HTTP streams on iOS devices with small screens, such as iPhone and iPod touch. Apple TV 2 and later includes an HTTP Live Streaming client.
Important iPhone and iPad apps that send large amounts of audio or video data over cellular networks are required to use HTTP Live Streaming. See “Requirements for Apps.”
Safari plays HTTP Live streams natively as the source for the
Important Always use the
Because it uses HTTP, this kind of streaming is automatically supported by nearly all edge servers, media distributors, caching systems, routers, and firewalls. 使用HTTP协议，那么几乎所有的。。。都支持。
Note: Many existing streaming services require specialized servers to distribute content to end users. These servers require specialized skills to set up and maintain, and in a large-scale deployment this can be costly. HTTP Live Streaming avoids this by using standard HTTP to deliver the media. Additionally, HTTP Live Streaming is designed to work seamlessly无缝的 in conjunction结合 with media distribution networks for large scale operations. HTTP LIVE Streaming使用标准的HTTP来传递每天，另外，他还与媒体分布式网络无缝结合，用以处理大尺度的操作。
The HTTP Live Streaming specification is an IETF Internet-Draft.
At a GlanceHTTP Live Streaming is a way to send audio and video over HTTP from a web server to client software on the desktop or to iOS-based devices.
You Can Send Audio and Video Without Special Server Software 不用特殊的服务器软件，一个普通的web sever就好。You can serve HTTP Live Streaming audio and video from an ordinary web server. The client software can be the Safari browser or an app that you’ve written for iOS or Mac OS X.
HTTP Live Streaming sends audio and video as a series of small files, typically of about 10 seconds duration, called media segment files. An index file, or playlist, gives the clients the URLs of the media segment files. The playlist can be periodically refreshed to accomodate live broadcasts, where media segment files are constantly being produced. You can embed a link to the playlist in a webpage or send it to an app that you’ve written.
Relevant Chapter: “HTTP Streaming Architecture”
For video on demand from prerecorded media, Apple provides a free tool to make media segment files and playlists from MPEG-4 video or QuickTime movies with H.264 video compression, or audio files with AAC or MP3 compression. The playlists and media segment files can be used for video on demand or streaming radio, for example.
苹果提供的是什么工具啊？能从live的带H.264 视频和AAC或者MP3 音频的 MEPG-2 编程媒体分割文件和播放列表。
For live streams, Apple provides a free tool to make media segment files and playlists from live MPEG-2 transport streams carrying H.264 video, AAC audio, or MP3 audio. There are a number of hardware and software encoders that can create MPEG-2 transport streams carrying MPEG-4 video and AAC audio in real time.
下面讲的是加密
Either of these tools can be instructed to encrypt your media and generate decryption keys. You can use a single key for all your streams, a different key for each stream, or a series of randomly generated keys that change at intervals during a stream. Keys are further protected by the requirement for an initialization vector, which can also be set to change periodically.
Relevant Chapter: “Using HTTP Live Streaming”
You should have a general understanding of common audio and video file formats and be familiar with how web servers and browsers work.
iOS Human Interface Guidelines—how to design web content for iOS-based devices.
—the IETF Internet-Draft of the HTTP Live Streaming specification.
