Audio Video News

Bandwidth limitations have long been a primary obstacle to transmitting broadcast-quality video over the Internet. Even digital subscriber lines (DSL), so useful for quick access to text and graphics, are typically capable of quality video over short distances only.

Those limitations are being pushed back, thanks to engineering efforts by companies like Norwalk, CT–based mPhase Technologies. On October 25, mPhase announced that it had achieved a breakthrough in the delivery of video over DSL, one greatly extending the useful distance over which a broadcast-quality MPEG-2 signal can be transmitted. The transmission technology involves a "repeater," or loop extender, which successfully supports an MPEG-2 grade, real-time video channel over the DSL spectrum at over 20,000 feet (approximately 3.5 miles) via a single twisted-pair copper loop. The distance achieved by mPhase "nearly doubles the currently prevailing service distance of digital TV-over-ADSL (Asymmetric DSL) and potentially exceeds the service reach of VDSL-based (Very High Data Rate DSL) systems by four to five times the current distance capability," according to a company announcement.

Repeaters have been used for decades to boost low-level signals over long distances. mPhase engineers therefore didn't reinvent the wheel, but did adopt it in such a way as to make it perform nicely in a digital environment. The experiment propagated a digital video signal at 4.4Mbps (megabits per second), "sufficient to support the highest quality broadcast television signals, particularly live action events such as sports programs and concerts."

Company engineers hope to achieve even greater coverage; such efforts will eventually make high-definition television over telephone lines—ie, on the Internet—a viable reality. Research firm Strategy Analytics predicts that 46 million homes worldwide will receive digital TV delivered via phone lines by 2008. DSL will account for 11% of worldwide digital TV services vs 1% in use today, according to the prediction.