What if you took the decentralized, distributed theory that powers torrent technology and applied it to live streaming?
That question, or one similar to it, is what BitTorrent inventor Bram Cohen must've asked himself a few years ago. The answer is BitTorrent Live, and it's currently working its way through a series of weekly real-world tests at the BitTorrent headquarters in San Francisco.
BitTorrent Live is a live-streaming technology that leverages the bandwidth of everybody watching the stream to lighten the stream's network load. It could be applied to everything from family weddings to corporate conference calls to multiday music festivals, says Cohen.
"Live streaming is a big challenge that people have been trying to solve," he said. "We're hoping that this is a fundamental technology that will change how people use the Internet."
Basically, BitTorrent Live is torrent theory applied to a live stream, but powered by completely different code. Even in its current buggy beta form, it's attracted early interest from little-known local electronic music makers to movers and shakers like Hank Shocklee, founder of Public Enemy, current music producer, and president of Shocklee Entertainment.
"The concept is incredible," Shocklee said when checking out BitTorrent Live during an impromptu visit to the BitTorrent offices last Friday night. "I come from marketing and promotion. If you can make the technology connect with people, that's a wrap."
How does it work?
The way you use it is extremely simple and accessible. You download a small executable file for Windows, Mac, or Linux, run it, and then point your browser to a site that's powering its stream with BitTorrent Live. Neither your computer nor your browser will have to be rebooted. But how does it do it?
BitTorrent Live has to solve four problems simultaneously: low latency, high reliability, high offload, and congestion control. Basically, Cohen explained, the data blasts out in pieces from the source using a "screamer" protocol that always uses the lowest latency path. The data gets blasted out to a subset of the peers, which get the benefits of high reliability and low latency, but at the very last hop it uses a nonscreamer protocol so that it gains back congestion control and efficiency. High offload is the fraction of data coming from peers instead of the source.
Cohen said that this is what creates a low-latency, high-reliability stream, and it only requires an upload capacity of five times the original bit rate on the original uploading machine. BT Live does its network congestion control based on delays, not packet loss, similar to uTorrent Protocol (uTP).
Cohen also noted that BT Live scales very well, with projected modeling showing a 4- to 4.5-second delay for up to 1 million peers. BT Live uses the H.264 codec, in large part because of its broad support base. Google's WebM alternative to H.264, he said, just doesn't have the the kind of support that BT Live requires.
There's a few features left to include, Cohen said, most notably fixing stream glitches, adding encryption, and what he called "graceful failure," so that it has higher tolerance for when the stream misbehaves.
One of the biggest recent tests of BT Live has been from the Dean Guitar's NAMM Jam, and Cohen reported that there were no major hiccups there. However, BitTorrent continues to put the protocol through a latency and scalability gantlet with its weekly tests. If you want to check those out, they're available at live.bittorrent.com Fridays from 8 to 10 p.m. Pacific. If you're interested in using the streaming technology, BitTorrent has provided an e-mail for queries: email@example.com.
The company plans to release BitTorrent Live to the public later this year, with an SDK and a Web site sometime in the second quarter. It's likely, though unconfirmed, that it will go with a freemium model not unlike with its mainline BitTorrent and uTorrent software.