Audio Over CAT5: Divide and conquer

This post is a supplement to my article 'CAT5 tracks: Audio goes the distance, reliably and on time' in the July 7, 2005 issue of EDN.

The latest v7 of Apple's Logic Pro audio creation software, the result of Apple's mid-2002 acquisition of Emagic, includes a distributed audio-processing feature called Logic Node. If you, for example, tether a PowerBook laptop to a more powerful PowerMac desktop, you can employ the PowerMac to subdivide the processing of mixing, producing, post-production and sound design tasks, over the standard TCP protocol. Apple claims that a Gigabit Ethernet connection enables you to work with as many as 128 streams, but lower performance distributed processing over 100-Mbit Ethernet, along with 400-Mbit and 800-Mbit FireWire, is also possible.

Video algorithms have also received distributed processing focus at Apple. The Compressor 2 algorithm employed by DVD Studio Pro, along with algorithms contained within the Shake compositing software, are distributed processing-enabled courtesy of their underlying Qmaster networking engine. And distributed processing isn't an Apple-only play; Microsoft partner company GridIron Software released X-Factor, which enables distributed Windows Media encoding, at this spring's NAB conference.

Muse Research offers a conceptually related scheme called Uniwire for its Receptor hardware-based audio plug-in processor. Bryan Lanser, vice president of business Development, explains; “Our solution involves the packetizing and management of Audio, MIDI, and VNC-based remote control between our product and a host computer. Our physical interface between the computer and host is standard, off-the-shelf CAT5 cable using all standard Ethernet protocols, but the interface to and from that physical layer is done via a host application plug-in.

“These plug-ins can be one of several varieties: VST is the most common, but there is also DirectX as well as Audio Units from Apple and RTAS from Digidesign.We create a proprietary plug-in in one of these formats that serves as the network interface for the Audio and MIDI that flows to and from our Receptor product. The host computer, specifically applications like Logic, Cubase, Nuendo, etc. all have automatic delay compensation built into the application, and they take care of keeping everything in sync. Our primary goal with Uniwire is to allow the off-loading of processor-intensive plug-ins onto Receptor, with the audio results being brought back into the host with a minimum amount of hassle for the end-user.”