I Phone Review

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.

For the last decade, Apple has been selling QuickTime Streaming Server, which uses an RTSP (Real-Time Streaming Protocol) server to stream live or rebroadcast video feeds to viewers. Apple uses this technology to stream some of its own live events. However, despite offering royalty free streaming and also delivering it as an open source project, QuickTime's RTSP streaming server hasn't gained the traction it was once expected to achieve. A large part of this is due to the fact that RTSP traffic is blocked by many firewalls, making it difficult to deliver streams reliably. The audio and video conferencing used by iChat also relies on RTSP, causing some users frustrating problems for the same reason. Getting RTSP video streaming to work on the iPhone would be even more difficult, as it routinely moves between mobile and WiFi networks.

Enter HTTP Live Streaming. The basic mechanics involve using software on the server to break an MPEG-2 transport stream into small chunks saved as separate files, and an extension to the .m3u playlist specification (.m3u8) to tell the client where to get the files that make up the complete stream. The media player client merely downloads and plays the small chunks in the order specified in the playlist, and in the case of a live stream, periodically refreshes the playlist to see if there have been any new chunks added to the stream.

What's next? The obvious followup is to add support for HTTP Live Streaming in Apple TV, allowing for HD streams direct from broadcasters, facilitating the ability to only pay for channels you want to watch, skipping around the local cable monopoly while gaining access to content they don't carry. The same content would also be accessible on the iPhone, a desktop PC, or any other device with the capacity to play modern video codecs. And that's why Apple is not supporting Mozilla's efforts to use the obsolete Ogg Theora on the web, which lacks silicon support for hardware acceleration on mobiles and appliances.

The real benefit to HTTP Live Streaming is that the server can maintain multiple versions of the clips in different formats. This allows an iPhone user with a WiFi connection to negotiate a higher quality version of the video than if only EDGE were available. Even better, the phone can renegotiate a higher or lower quality dynamically if it improves or loses signal. This enables the watcher to experience the best video quality possible at the current bandwidth available, continually optimized as new segments are requested. Unlike Microsoft's Smooth Streaming trojan horse for Silverlight, HTTP Live Streaming works with any playback client on any platform and does not involve a layer of DRM, although it does support encryption, allowing broadcasters to limit access to their content. Because support is built directly into the iPhone's embedded QuickTime player, users don't even need to download apps for every broadcaster or channel; content creators can simply publish their feeds within a standard website, and iPhone can access them just like a desktop client. Other phones can similarly support the same interoperable standard, providing a leg up for mobile platforms with less commercial attraction or no ability to run real applications, like the Palm Pre.