Audio Video News

If it were legal, how would you record a high definition television program? High-definition digital video signals propagate at a data rate of 24Mbits/second, a rate that would quickly fill up the approximately five gigabytes of storage available on standard recordable DVDs. That's barely enough to record a half-hour sitcom, if the commercials were deleted.

An alternate to the recordable optical disc is a large-capacity hard disk, as in some "interactive" set-top boxes and personal video recorders (PVRs). The problem with such devices is that they lack portability. A better solution is increasing the data density of the recordable optical disc through the use of short-wavelength blue lasers. Research at Sony Corporation, Philips Electronics, and elsewhere holds great promise for possible commercial development of blue laser DVD-recordables, with a data capacity so high that they would make sense for capturing HD programming.

Recent research by Philips scientists indicates a potential data density of up to 25Gbytes on a DVD with a read/write data rate up to 50mbs, using a blue laser as a read/write device. "The high rate and capacity enable recording of HDTV and new features like simultaneous recording and playback of standard-definition TV (SDTV) material. Moreover, the system achieves seamless playback of edited material," according Philips Research principal scientist S.B. Luitjens, whose paper on the subject appeared in the June 14 edition of PlanetAnalog.

The optical disc's many proven advantages—random and instant access, for example—make it superior to tape and more convenient for users. Editing is also easier and more precise, Luitjens explains. He also alludes to a proposed format for digital video recording that would accommodate "digital broadcast signals based on the Advanced Television Standards Committee (ATSC) standard for digital broadcasting in the United States, the International Services Digital Broadcast (ISDB) standard in Japan, and the Digital Video Broadcast standard in Europe." A blue-laser DVD-recordable would have enough capacity for "two hours of HDTV broadcast (at 24mbs) and close to eight hours of SDTV broadcast material (at an average data rate of 6mbs)," Luitjens writes.

Despite three years of research, blue laser devices are far from being finished technology. Some prototype recorders have been demonstrated—Luitjens states that Sony and Philips will show more advanced laboratory creations later this year—but it may be several years before video fans can get their hands on affordable recorders. Even when that comes to pass, consumers will still have to work around the inevitable legal restrictions on the use of recorders, imposed by governments at the behest of the television and film industries.