By Brian Boyko
Recently, we had a chance to speak to Joe Miller, VP of Platform and Technology Development at Linden Labs, the makers of online “virtual world” Second Life, regarding their plans to rollout VoIP on the popular world, known for being the online virtual homes of businesses (such as Cisco), news organizations (such as Reuters), and political campaigns (such as John Edwards).
According to Miller, the VoIP product is unique because of the ability to project the sound in three dimensional space, as a function of distance and direction from one avatar to another. It takes a 32khz signal at 32kbps from clients, sends it to an Intel based audio server where the input signals are mixed and properly positioned, acoustically, in three dimensions, and a stereo stream is sent back to the client at 64kbps. Even with 100 people speaking at once, the bandwidth requirements are the same for each individual because the servers (dual quad-core Xeons) mix the voices together into a single data stream.
The codec used is Siren 14/G.722.1 Annex C, developed by Polycom but now an international standard. It was chosen because it uses relatively low bandwidth but can carry a wide and dynamic range of audio – not just human voices – making it an ideal codec to broadcast, say, a musical event.
“It carries the complete human hearing range – it’s not just a speech codec, it carries music and ambient sounds quite well.”
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As for bandwidth requirements, Miller was a little concerned about the “last mile” but he said that voice is a very small percentage of the game’s overall traffic, and it doesn’t go through the main game pipes, and doesn’t impinge on the performance of the Second Life Simulator Grid.
“The actual bandwidth requirement for this particular codec is quite low for the frequencies it’s carrying… We’re using well-under 100kbps of signal to take and send this audio stream, that won’t put a dent in the traffic we send to and from our servers to maintain our visual services,” Miller said.
“We have dynamic channels we can assign on the fly to large events. If we get a surge of traffic into a particular set of regions in Second Life, we can automatically and dynamically assign additional channels to handle the load without creating stress on the other parts of the Second Life grid. … Monitoring systems that run on our core switches and routers that allow us to see at any moment in time how much bandwidth we’re using – in different parts of the day, different parts of the system, different physical locations of the grid.”
The program has been in development for over a year and Linden Labs has been testing it internally for over a year, Miller said. Next week, Linden Labs will start with a by-invitation technical trial available to about 1000 simultaneous audio users, after which a public beta will be available. VoIP is expected to become a standard feature in future versions of Second Life, and the roadmap includes letting users eventually “design” the sound of their voice much like they currently design the current look of their avatars.
Users will be able to opt-out of voice or ignore individuals, and they’ll be able to privately talk person to person or join an affinity group which allows intra-group discussion. Eventually, Linden plans to charge Linden Dollars for the service to be activated on privately owned land. People who own land can pay to have VoIP activated for all users on their property, people who sublease from others (such as Linden) can choose to deactivate VoIP on their property if they choose.
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