The Missing Link

Now that affordable computers are powerful enough to record multiple tracks of digital audio and simultaneously run software synthesizers that can play
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Now that affordable computers are powerful enough to record multiple tracks of digital audio and simultaneously run software synthesizers that can play multiple MIDI parts, you might think that electronic musicians finally have everything they need to realize their creative vision. However, a corollary to Murphy's Law states that a system's capabilities will always fall just short of what's required to finish a project, giving rise to the familiar refrain, “If only the computer could handle a few more audio channels (or plug-in slots or MIDI tracks).”

Steinberg (www.us.steinberg.net) has addressed the problem with a new addition to its suite of technologies: VST System Link. This ingenious scheme lets you connect any number of computers and share their resources via one digital audio cable to and from each machine in a peer-to-peer network with a daisy-chain or closed-ring topology.

VST System Link is platform independent, allowing Mac and Windows machines to work together on the same network. Each computer must have some sort of ASIO hardware with the appropriate drivers and one or more System Link — enabled applications (which currently includes the latest version of Cubase and Nuendo). You simply connect the digital-audio output from one computer's ASIO interface to the digital-audio input of another computer, using any type of digital-audio connection, such as ADAT, TDIF, AES/EBU, or S/PDIF.

The network messages, which include synchronization, signal routing, transport control, and MIDI, are transmitted using a single bit of one digital-audio channel, providing a total network bandwidth of 96 kbps and leaving 23 bits available for digital audio. (To accomplish this, the audio's 24th bit is truncated, then added back in with a value of zero at the end of the process.) That bandwidth can accommodate up to three MIDI ports' worth of data (each port has a bandwidth of 31.25 kbps), but a given port rarely if ever actually carries that much data. So VST System Link is designed to address 16 ports with 16 channels each for a total of 256 channels. If necessary, the System Link audio channel can be completely dedicated to data, relieving any bottleneck.

Once everything is connected, you can run any compatible application on each computer and allocate processing tasks according to each machine's capabilities, which lets you make use of older computers. For example, you can use one computer for digital audio tracks, another for virtual synths, a third for effects, and a fourth for mixdown. Alternatively, you could run the same program on several computers to extend its capabilities severalfold (see Fig. 1).

The first computer in the chain is designated as the “master,” which normally sends sync signals to the others, but the entire system can be controlled from any computer on the network. Speaking of sync, Steinberg claims that VST System Link is sample-accurate, thanks to the Positioning Protocol already built into ASIO. In addition, the system can sync to an external clock source or the embedded clock.

For now, Steinberg will concentrate on incorporating VST System Link into its own products, including a video-player application that was shown running full-screen video in sync with Nuendo and Cubase on separate computers at the recent European AES convention in Munich. In addition, the next version is intended to have Save and Load commands, as well as the ability to bundle each computer's data into a “meta-project” file. Music computing will never be the same.