The chip set includes a DVD-write processor for writing data to DVDs; an analog front end that reads analog RF data from a laser detector and converts it to digital format; and a DSP that serves as a combo controller for CD reads, DVD-ROM read and CD-R(W) writes.

In building a consumer recordable-DVD system, Oak's chip set will require a separate back-end compression/decompression subsystem, with which it communicates via a DVD drive's standard IDE/Atapi interface. For a PC DVD application, OEMs need to add only a microcontroller, flash ROM, SDRAM and motor drives, according to the company.

In a growing market for recordable-DVD solutions dominated by vertically integrated drive suppliers that design their own chip sets, Oak's entry represents "the industry's first merchant-market recordable-DVD-drive solution," said Jim Chase, director of product marketing for optical storage at Oak.

By exploiting the company's proven combo solutions, which offer both CD-RW and DVD read in a single drive controller, Oak's chip set is designed to support all popular media types by reading DVD-ROM, DVD-R, DVD+R, DVD+RW and DVD-RW disks. Such features are critical for a broader market acceptance of recordable-DVD drives, since without them, the welter of recordable formats means consumers will bump into media-incompatibility issues.

While many current solutions consist of five to seven discrete ASICs, Oak offers a more highly integrated approach, which the company hopes will enable lower OEM cost points for consumer and PC versions of recordable DVD drives.

One set, two processes

Oak's chip set, priced at $25 in production quantities of 10,000, is now sampling. It is being fabricated by Taiwan Semiconductor Manufacturing Co. using two processes: 0.25 micron for the analog front end and CD-RW/DVD-ROM combo controller, and 0.18 micron for the DVD write processor.

In a DVD recorder, incoming video data must first be digitized if it is in analog form, then compressed into a DVD-compliant video stream by the back-end subsystem. That subsystem must also control the DVD drive so that it's prepared to record the video stream to disk as it is compressed in real-time. The key here, said Chase, is that "the record process must be fast and reliable since the back-end subsystem cannot buffer more than a few seconds of compressed video data unless a hard drive is present."

Chase explained that Oak's drive controller chip set receives the DVD-compliant MPEG video stream and adds all the DVD error correction and channel timing before writing it to the media. "Before and during the writing of the data to the disk, the Oak chip set reads the address and other information in the wobble track of the disk to find out the characteristics of the media," he said. The wobble track is a faint, prewritten spiral on a blank disk that the drive uses as a guide when writing data. Address and other information is modulated in the wobble track and can be read by the drive so that data is always written in the correct area of the disk.

When recording is finished, the drive must then finalize the disk by adding the table of contents and other information required to make the disk readable by other drives. Navigation menus may also be added by the back-end system and recoded to the disk as part of the DVD disk-creation process.

Oak offers all these DVD-drive functions through the OTI-9832 combo analog front-end device; OTI-9838 combo controller capable of 24x CD-RW writing speeds; and OTI-9831 DVD write processor, capable of 4x write speeds, according to the company.

In designing this chip set, Chase said, "The biggest challenge was architecting the solution in a way that maximized the usage of our high-performance and proven combo CD-RW and DVD-read solution while not making compromises on the DVD-recording features and performance." In contrast, he said, "competitors' solutions add the CD-recording function as a standalone chip and do not support high-speed CD recording."