Telepresence equipment provider Polycom is employing a version of H.264 compression ideally suited for delivering high-quality talking head video at radically reduced bit rates. For example, the firm claims that 720p telepresence-quality resolution on a 50-inch plasma screen can be delivered at 512 kilobits per second, or half the rate required by other systems.
Such claims have now been independently verified in a series of tests conducted at Polycom’s bidding by Wainhouse Research.
An advanced form of videoconferencing, telepresence has traditionally used lots of bandwidth to achieve its lifelike quality: typically 4 megabits per second or more for 1080p resolution on very large screen “immersive” room-size systems and at least 1 mbps for 720p on smaller systems. But not every enterprise – particularly small businesses – can afford to upgrade its bandwidth to support telepresence, including several simultaneous sessions.
“The typical enterprise does not want to deploy more pipe for videoconferencing,” says Ira Weinstein, senior analyst at Wainhouse Research. “So when they go to their service provider and say, ‘I’d like you to host some high-quality video over the WAN,’ the service provider has a bit of a challenge.”
“If I have 5 megabits to play with, and I want HD quality, maybe I can get seven or eight calls in there instead of five,” Weinstein says.
Polycom is leveraging the High Profile of the widely used H.264 video compression standard. Polycom says its High Profile implementation uses 50-65 percent less bandwidth than rival products. The vendor hired Wainhouse to test that claim partly in response to rival vendors’ scoffing.
“We had thoroughly tested various call scenarios in our own labs and were confident in our claims,” says Sudhakar Ramakrishna, Polycom’s chief development officer and general manager of unified communications products. “We can understand why our competitors were skeptical. The ability to dramatically reduce bandwidth requirements without compromising quality of experience is a huge benefit for our customers.”
Wainhouse set up four Polycom HDX 8000 room-sized telepresence systems to enable comparisons at various levels of resolution and frame rates – 720p30 and 60, 1080p30, etc. – between High Profile and the Baseline Profile commonly used by most suppliers and then throttled back the bandwidth incrementally, starting at 25 percent. In half of the test calls, Wainhouse reported Polycom achieved bandwidth reductions of at least 50 percent, with two tests recording bandwidth savings of 65 and 67 percent.
It wasn’t until a 75 percent cutback that the compression affected video quality to the point that Wainhouse felt a layperson would notice, Weinstein says. “If I put it on a scope, absolutely there is a technical difference,” he notes. “But if I put the typical user in a typical meeting room for a typical talking-head video call, they wouldn’t notice it.”
H.264 High Profile leverages the fact that the vast majority of telepresence sessions involve only talking heads. That means most of what’s in each video frame is relatively unchanged, making it much easier to compress than, say, a movie or TV show.
“This is an example of a wise compromise, considering the use case,” Weinstein says.
H.264 High Profile also leverages Moore’s Law: As computing power increases, it becomes easier for telepresence vendors to develop products that can do that level of real-time compression – ideally without a hefty price premium on the hardware side.
If end users agree that H.264 High Profile products strike the right balance between quality and bandwidth, the impact could be far-reaching. For example, besides the general enterprise market, H.264 High Profile telepresence could be a good fit for telemedicine applications such as telepsychiatry, where HD video can capture the subtle body language and facial expressions that are helpful for accurate diagnoses.
Given the benefits, Weinstein expects more vendors to use H.264 High Profile and other tactics.
“The Tandberg C series has a lot of power. I wouldn’t be surprised to see them deploying other things, as well,” he says. “This is a logical step in the evolutionary curve. The other vendors are all doing things similar.”