QuickTime Cuts Chop in Video Stream
When you’re watching video on the Web, you’re rarely alone. You’re usually accompanied by the Three Musketeers of Internet video: blocky, jerky and chunky. They turn faces into pixilated mosaics and motion into freeze frames.
The Internet’s decentralized, distributed design is ideal for many things, but video isn’t one of them. If incoming data are lost or delayed when you’re surfing, you simply have to wait a bit longer to see a Web page. But if delays occur during a video stream, the Musketeers step in and do their act.
In version 5 of its QuickTime multimedia and streaming software, Apple Computer Inc. has added a feature designed to keep the Musketeers at bay. Apple calls the feature “skip protection,” and judging from the Webcast of Apple Chief Executive Steve Jobs’ Macworld Expo keynote address last month, it works well.
I’ve watched several Jobs keynotes via QuickTime, and last month’s looked better than any of them. No, it wasn’t high-definition television--it wasn’t even aluminum foil bow ties attached to rabbit ears. But unlike a lot of live video Webcasts, it was watchable.
And it was popular. Frank Casanova, Apple’s director of QuickTime product marketing, said the keynote Webcast was, at its peak, viewed by 44,234 simultaneous viewers--more than twice the number who tuned in to his speech in July 2000. About 22,000 users viewed a high-bandwidth version that streamed at 300 kilobits per second. The Webcast blasted up to 6 gigabits of data over the Internet every second. These audience stats put Steve Jobs up there with Madonna and Paul McCartney as one of the top draws for live Webcasts. And Jobs has yet to sing on stage.
The logistics of delivering a large-scale Webcast are staggering. Producers in San Francisco fed the live satellite link from New York into a bank of Power Mac G4s running encoding software, which compressed the feed for Internet delivery. Apple delivered four streams: an audio-only stream for modem users connecting at 28.8 Kbps, and separate video streams running at 56, 100 and 300 Kbps. The QuickTime playback software automatically selects the stream that best matches your connection speed.
Those streams were then routed into a content-delivery network operated by Akamai Technologies Inc., of which Apple is part owner. Like other delivery networks, Akamai streamlines data transmission across the Internet by, among other things, distributing data to geographically dispersed servers. This reduces the number of “hops” that data must make on their journey to your desktop. And that helps keep blocky, jerky and chunky off the screen.
But what really made the difference in the keynote Webcast was QuickTime 5’s skip-protection features working in tandem with the latest version of Apple’s QuickTime Streaming Server. To improve streaming reliability in QuickTime 5, Apple turned to the portable CD player for inspiration. By reading more data from the CD than it actually needs at a particular moment, a portable CD player works even when strapped to a jogger’s hip: When bumps occur, playback isn’t interrupted because the player already has read enough data to weather the storm.
QuickTime 5 works similarly. The other major streaming technologies, Microsoft’s Windows Media and RealNetworks’ RealSystem, have similar features.
Speaking of streaming competitors, Microsoft demonstrated a Mac OS X version of its Windows Media Player at the Macworld Expo. The new version will run only under OS X and sports an elegant look and feel--a stark contrast to the ugly beast that Microsoft shipped for Mac OS 9. The Mac version of Windows Media Player always has lagged behind its Windows counterpart, but the OS X version may change that.
Of the three streaming media titans, only RealNetworks has yet to announce OS X support. The company had better show its hand soon, because its competitors’ players are looking better than ever.
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Jim Heid is a contributing editor of Macworld magazine.
