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Live Streaming in the Works at BitTorrent
The P2P giant is close to bringing the immediacy of television to online viewers, without bandwidth issues.

BitTorrent's peer-to-peer sharing may soon learn a new trick, as Bram Cohen, chief scientist and co-founder of the company (and the originator of the BitTorrent protocol itself) has been at work on live streaming technology for the past two years. While he won't say when it will be ready, he's getting closer.

The key challenge to creating peer-to-peer (P2P) live streaming has been cutting down the latency, says Cohen, noting that the way TCP/IP handles congestion creates high latency. The streamed video needs to be close enough to live that people holding a text chat about what they're watching won't get out of sync. Most of the delays have to do with how fast light can travel, he says, as optical signals need to be passed back and fourth. That's why the time delay that viewers experience will be related to the physical distance between them and the BitTorrent client sending the signal. He's had to create a detection system so that more data wasn't being sent to each line than it could handle, but that all available bandwidth was being used.

Cohen has now gotten the delay down to about 5 seconds, with a 99 percent offload. That means that 99 percent of the bandwidth is handled by the viewers' BitTorrent clients, not the person or organization originating the content.

With latency issues mostly solved, Cohen is now working on packet loss. In order to test the software, he has a virtual network on his computer, a system he created, that he uses to emulate router queues. In his tests, he typically sets it for 100 to 500 virtual users. Using his program, he's able to see when queues get too full and packets are dropped.

"It would be impossible to debug this thing without it," Cohen says.

Since he's able to do most of his testing on paper or with this model, he won't move on to actually beta testers until he's worked out all the major issues.

The P2P live streaming technology is also known as Project Pheon, which refers to a type of arrowhead. Cohen won't guess when the finished product might be available. While a ZDNet article said the company was hoping for the end of the year, that sounds like it might be ambitious. Once the major obstacles are cleared away, Cohen says he has a long list of finer details to deal with.

For testing, Cohen is using a modified Flash player as the client, although he doesn't know what the final end-user client might look like.

Many potential partners have approached BitTorrent about the live technology, but Cohen says he needs to get it working before thinking about partnering up. His end goal is to bring a television-like experience to the Web. The majority of video is consumed on television, he notes, and that's a low-latency medium.

"I'm trying to get it so all that video compression can be moved online, so that television will truly move to the Internet," he says.

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