Nov
8
HTTP Video Streaming For iPhone
November 8, 2009 | Leave a Comment
Apple announced the new features of the iPhone OS 3.0, that the iPhone would be capable of streaming video and audio directly over HTTP. Apple also advertised HTTP streaming as a feature of QuickTime X, the update of its media architecture coming in Snow Leopard. What it failed to explain, at least publicly, is how this streaming would be accomplished. Fortunately, Apple submitted its proposed protocol last month to the Internet Engineering Task Force (IETF) in the hopes that it will become a ubiquitous standard.
HTTP streaming works through a very simple mechanism. Every time a seek operation is performed, the media player makes a request to the server side script with a couple of GET variables. One is the file to play and one is the start position. The server side script then starts the video from the offset given. Below is a short example. After you start the video, you can directly jump to any part in the video without having to wait until it is loaded.
Before Adaptive Streaming, video on the web had always been plagued by two major issues: quality of the video (either too small or too blurry) and reliability of the playback (constant rebuffering or stuttering). The problem was that the two variables were interrelated. Increasing the quality requires higher bandwidth, and using less bandwidth to minimize re-buffering sacrificed video quality.
This is in contrast to real-time streaming, as there would necessarily be a minimum latency of whatever duration the server slices the stream into (Apple refers to 10 seconds as an example). As the server encodes the video and slices it into 10 second clips, for instance, it creates or updates a playlist for the stream with the URL of the next clip. The client begins by downloading one or more of the clips, playing them in order. As one clip plays, the client begins downloading the next specified clip until it reaches a tag in the playlist that signals the end of the stream.
Adaptive Streaming allows programmers to offer a higher quality viewing experience to a broader audience. Being able to offer HD streams all the way down to low bandwidth streams, without pauses or interruptions of the video, makes for a significantly improved consumer experience.
Learn more about iPhone HTTP Streaming segments. Stop by Ankoder site where you can find out all about Online Video Encoding and what it can do for you.
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