Square One: Into the Ether

HOW ETHERNET AND OSC IMPROVE ON MIDI
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HOW ETHERNET AND OSC IMPROVE ON MIDI
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Musicians and engineers are always connecting one gadget to another, and as a result tend to develop a refined understanding of wiring standards, connectors, and, in the digital age, communication protocols. One such protocol, Ethernet, is showing up in an increasing number of audio devices. That fat telephone-style plug once used only for hooking up to a local area network is finding new and interesting uses.

The Lay of the LAN

Ethernet is the most common protocol for interconnecting devices on a network. It's a slight but useful oversimplification to say that the term refers to the RJ-45 (technically 8P8C) connector, Cat-5 cable, and packetized data format with which we're all familiar. Developed in the mid-1970s at Xerox, Ethernet offers speed, simplicity, and reliability. It also offers adaptability, as it is capable of carrying any sort of data, MIDI included. Although USB 2.0 and FireWire offer similar speed, availability, and flexibility, Ethernet allows longer cable runs.

Ethernet comes in three major types, defined by their bandwidth. 10Base-T offers 10 megabits per second of throughput, whereas 100Base-T and 1000Base-T offer 100 Mbps and 1,000 Mbps, respectively. 1000Base-T is also known as gigabit Ethernet. Ten-gigabit Ethernet is also defined, but it has not yet become commonplace. For comparison, FireWire 400 (IEEE-1394a) has a bandwidth of 400 Mbps, and USB 2.0 has a bandwidth of 480 Mbps.

It wasn't that long ago that conventional wisdom led the savvy DAW builder to remove any network devices from an audio computer. Since that time, however, network functionality has become ever more deeply integrated into the OS, and Ethernet ports have become ubiquitous on motherboards, including those in notebooks. Although one might still choose to keep a DAW disconnected from the Internet, local area networking has become an essential part of file and session management. Special servers can even allow streaming of audio and video assets across a network in real time.

Seizing Control

With a fast and proven data pipeline built into virtually every PC and Mac, it was inevitable that developers would start writing audio applications and creating devices to take advantage of it. Since the introduction of its first major control surface, the Pro Control, Digidesign has used Ethernet to exchange control gestures with Pro Tools. Even 10Base-T Ethernet, the stated minimum requirement for all Digidesign control surfaces, provides several times the 31.25-kilobaud bandwidth of MIDI, which is common in less expensive controllers.

This increased bandwidth allows the Pro Control, C|24, D-Control, and other Digidesign work surfaces to provide real-time metering, expansion to include dozens of faders, and reporting of track names and other information to the work surface. More speed allows more simultaneous control of level, pan, and plug-in parameters along with more-responsive writing of automation than is typical with MIDI controllers.

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FIG. 1: The Euphonix MC Mix uses a protocol called EuCon to communicate with host applications via Ethernet more quickly and precisely than MIDI would allow.

Similarly, Euphonix takes advantage of Ethernet's speed in its control surfaces, including the MC Pro and System 5 MC. A special protocol called EuCon translates the control surface's gestures into messages that can be understood by various host DAWs and that provide greater resolution than MIDI. This same arrangement has also been implemented in the more affordable MC Mix (see Fig. 1) and MC Control.

Either-net

Ethernet is also being used extensively to move MIDI and digital audio signals between audio devices. Distributed audio-playback systems in convention centers, theme parks, and other large installations often use one of various networking protocols — Cirrus Logic's CobraNet or Digigram's EtherSound, to name just two — to deliver dozens of streams of high-quality digital audio from centralized servers to background music systems. Performance venues are using these same protocols to replace multicore analog cabling in sound-reinforcement systems.

Roland's REAC recording system lets audio signals be digitized onstage and sent via standard Ethernet to a PC running Cakewalk Sonar to be recorded. An audio interface is required on the PC only for confidence monitoring.

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FIG. 2: This screen shot shows the configuration of a network MIDI port on a Mac. Since OS X 10.4, support for MIDI over LAN has been standard.

Various products allow MIDI control of soft synths and synchronization of DAWs over Ethernet. Apple's Mac OS X has had this capability built in since 10.4 (Tiger) was released (see Fig. 2). MusicLab's MIDIoverLAN CP extends this concept to include both Macs and PCs in any combination.

Digital audio connections such as S/PDIF and AES3 let audio be shared between DAWs, but they require some sort of audio interface. Plasq Wormhole2 offers an open-source cross-platform way to send a stream of audio from one machine to another and back through a 100Base-T or gigabit Ethernet connection for processing on the remote machine. FX-Max offers FX Teleport, a Windows-only application that off-loads the processing of a VST plug-in running on the host DAW to a remote computer.

Muse Research has developed UniWire, a cross-platform method of communicating both audio and MIDI between the host DAW and the company's Receptor hardware plug-in host via standard Ethernet connections. This not only simplifies wiring, but also allows the plug-in to be instantiated from within the host DAW. Because both audio and MIDI are sent, both audio effects and virtual instruments can be controlled. Waves makes two hardware processors, the APA-32 and APA-44, that stream audio through Ethernet from a host computer to be processed by Waves plug-ins running on the processors' DSP chips. The plug-ins are instantiated within the host DAW's mixer, but they actually run within the hardware unit.

In sending MIDI and digital audio over Ethernet, manufacturers must be careful about introducing latency. Most such products not only are optimized for low-latency performance, but also provide ways of measuring and compensating for latency.

In Performance

Many of the most interesting current performance controllers are using Ethernet to provide fast and flexible communication of real-time gestures. Rather than transmitting MIDI messages, however, the Ethernet-enabled devices listed here use or can use a newer data protocol called Open Sound Control (we'll show you how to get two devices to communicate via OSC in next month's “Square One”). Developed and maintained by the UC Berkeley Center for New Music and Audio Technologies (CNMAT), OSC lets computers, instruments, and other devices share performance data across a network. OSC is optimized for real-time use and offers advantages in both speed and flexibility over MIDI. It is also extensible enough to allow for incorporation into applications ranging from James McCarthy's SuperCollider to MIT's Csound to Cycling '74's Max/MSP.

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FIG. 3: JazzMutant''s Lemur and Dexter controllers offer sophisticated, multitouch-screen gestural control over DAWs, soft synths, and performance applications.

JazzMutant's Dexter and Lemur controllers use a 100Base-T Ethernet connection to the host computer (see Fig. 3). This gives them ample bandwidth for the devices' multitouch display to convey multiple streams of real-time information. Both devices are supremely configurable, and OSC allows great latitude in determining precisely how to convey performance gestures.

IRCAM, the Institut de Recherche et Coordination Acoustique/Musique, has developed EtherSense, a device that digitizes the output of real-time performance sensors, such as motion, heat, and proximity sensors, and converts it to OSC. The OSC stream is then conveyed to one or more computers running compatible applications such as Max/MSP, Miller Puckette's Pure Data, or Native Instruments Reaktor. A single EtherSense unit supports up to 32 analog sensors, converts each of their readings into a 16-bit value at 500 Hz, and sends those values via 10/100Base-T Ethernet to a Mac or PC.

With Ethernet ports on virtually every modern computer, the opportunities for imaginative hijacking of what most people know as a networking protocol are almost limitless. Most of the implementations I've listed require only 10 or 100 Mbps connections — imagine the sort of applications that will take full advantage of gigabit Ethernet. One thing is certain: the days of removing or disabling a network card when building a DAW are gone for good.

Brian Smithers is department chair of workstations at Full Sail University in Winter Park, Florida, and the author of Mixing in Pro Tools: Skill Pack (Cengage Learning, 2006).

ONLINE LINKS

UC Berkeley Center for New Music and Audio Technology home page
cnmat.berkeley.edu/

Using MIDI over Ethernet
www.midi.org/about-midi/ethernet.shtml