Digital Harmony

One of the most vexing problems plaguing studios everywhere is the mass of techno spaghetti needed to get various signals from point A to point B. Each
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One of the most vexing problems plaguing studios everywhere is the mass of techno spaghetti needed to get various signals from point A to point B. Each type of signal (analog and digital audio and video, MIDI, sync, and so forth) requires a different type of cable and/or interface, and all signal types must be made to work together as a unified whole. Wouldn't it be great if these signals could be fully integrated and sent over a single cable?

One of the most promising developments in this regard is a digital interface called IEEE 1394. This high- speed serial interface was first developed by Apple in the 1980s. Apple named it FireWire and submitted the specification to the Institute of Electrical and Electronics Engineers (IEEE), which established it as international standard 1394. Power Mac G4, PowerBook 2000, and blue-and-white Power Mac G3 computers have FireWire ports, and other 1394-equipped products such as hard drives and digital cameras are now widely available.

Devices with 1394 ports can form a network using a variety of topologies simultaneously-daisy chain, star, tree, and so on-as long as there are no closed loops. No more than 17 devices (called nodes in network parlance) can occupy a single daisy chain, and the cable length between nodes is limited to 4.5 meters for cheap twisted-pair cable or 100 m for fiber-optic or CAT5 cable. A network can contain up to 63 nodes, and as many as 1,023 networks can be bridged. Each node can include up to 256 terabytes of addressable space.

IEEE 1394 is ideal for media applications in many respects. For one thing, its current bandwidth ranges from 100 to 400 Mbps. A speed of 800 Mbps is expected later this year, and 1.6 Gbps won't be far behind. In addition, 1394 provides isochronous data transport for streaming media data. Isochronous data transport guarantees that all nodes have periodic access to the bus, allowing them to send data packets every 125 microseconds. It doesn't provide handshaking or retransmission if an error occurs, but errors are very rare. Even if a packet is lost, 125 (gamma)s corresponds to only a few samples of audio data, which is an inaudible gap.

The protocols for sending video data via 1394 are well defined in IEC 61883, a suite of standards codified by the International Electrotechnical Commission. This suite was recently expanded to include an extensible set of audio and MIDI protocols that began life as Yamaha's mLAN (see "Tech Page: Fire in the Wire" in the July 1996 issue of EM) and was later adopted by the IEC.

Among the companies working hardest on 1394 media applications is Digital Harmony (www.digitalharmony.com). In partnership with manufacturers of professional and consumer audio/video products, Digital Harmony has developed a licensing program to ensure that products adhere to the IEC 61883 protocols and are therefore completely compatible. The company also wants to be certain that all 1394 media products operate smoothly as a system, shielding the end user from the technicalities of network administration.

Because audio protocols were added to the 61883 suite only recently, no 1394 chips currently include them, so audio manufacturers must build expensive prototyping boards to develop products. Digital Harmony is working with several chip companies on an inexpensive 1394 chip that includes all media protocols. Scheduled for completion early next year, this chip will make it possible to produce reasonably priced 1394 products.

In collaboration with Digital Harmony, Peavey Electronics (www .peavey.com) is developing several 1394-based products for the personal studio (see Fig. 1). Such products will provide artists with unprecedented media integration, enabling them to easily complete multimedia projects and publish them on the Internet while banishing techno spaghetti from their studios forever.