provided by: 
The Internet is about to deliver beautiful high-definition TV to your PC. Matrixstream of Vancouver, British Columbia, has introduced technology for streaming real-time, interactive HDTV signals to home computers over the public Internet.
Today's PCs are more than capable of decoding and displaying both standard-definition TV (with a resolution of 480 pixels vertically and from 640 to 720 pixels horizontally) and high-definition TV (720 to 1,080 pixels vertically and 1,280 to 1,920 pixels horizontally). Indeed, media organizations have been using digital video processors and the Internet's underlying communications standard to send TV signals over private networks for years -- a practice called Internet Protocol TV, or IPTV.
Still, it may be hard to imagine the Web offering high-definition video, which has as many as 1,080 lines of vertical resolution, when sites like CNN.com and YouTube still deliver TV pictures at a measly 320 by 240 pixels of resolution. Delivering HDTV signals has always been the province of cable and satellite TV companies and over-the-air broadcasters, all of which own or license private, dedicated, high-bandwidth channels to get their shows into consumers' living rooms.
The challenge is how to get high-definition TV signals into a computer, short of hooking it directly to a subscription cable line. One solution is to translate a TV signal into standard Internet Protocol packets -- IPTV -- and send it to homes via broadband Internet connections, which are increasingly common. As of March 2006, 42 percent of U.S. homes had broadband Internet connections via DSL or cable modems, according to the Pew Internet and American Life Project.
But HDTV is a big bandwidth hog. Transmitting HDTV signals in real time, using the telecommunications industry's usual MPEG-2 compression standard for moving images, means sending data at 18 to 20 megabits per second (Mbps). The typical consumer DSL connection, by contrast, delivers data at only 1.5 to 3 Mbps, and the fastest cable-modem connections top out at 5 Mbps.
And even a 5-Mbps Internet connection isn't guaranteed to operate that fast all the time: engineers call the Internet a "best effort" network, meaning data packets are delivered as quickly as the myriad bottlenecks in data centers, the Internet backbone, and the last-mile connections into homes allow. Hence the long wait while your PC's media player software is "buffering" an audio or video download.
Matrixstream, founded in 1999 and headquartered in Vancouver, British Columbia, claims to have found a way around these difficulties. Like other companies in the video-processing business, it has adopted a new compression format, called MPEG-4 Part 10/H.264, which allows high-quality video transmissions at less than half the bit rate of MPEG-2. "But it's not just a compression issue -- it's an Internet transport issue," says Jack Chung, Matrixstream's chief technology officer.
According to Chung, Matrixstream's engineers developed a system of video servers that encode and encrypt a video signal, then send it to a special player program on the user's PC, using proprietary buffering and error-correction techniques that compensate for Internet bottlenecks. In this way, Matrixstream can transmit a DVD-quality TV signal at 1.5 Mbps and a high-definition signal at 2.5 Mbps -- well within the capacity of a cable-modem connection.
By Wade Roush
Read article at techreview.com