Switch Hitting

Live sound is getting on the net. Long runs of heavy copper cable are by no means obsolete, but the future belongs to digital signal distribution via Cat-5e and fiber optic cable. With a growing number of portable and installed systems using digital technology to cut costs and boost flexibility, manufacturers are bringing more products to market with network capability.
But which network? While we're waiting the market's decision on one or perhaps two de facto network standards, manufacturers are like baseball managers in the late innings of a tight game wondering who should bat next. Switch-hitting-the ability to bat both right- and left-handed-can be a strategic advantage in baseball. Similarly, being able to accommodate multiple audio transports in your audio product can be a strategic advantage in professional audio markets.

Lab X Technologies is often asked what it takes to field a "switch-hitting" networked audio product. We have experience with a wide range of audio network technologies, and our ESX EtherSound network module was developed specifically to allow manufacturers to bring both "lefty" (CobraNet) and "righty" (EtherSound) versions of the same base product to market.
In our experience, there are four areas to focus on when designing for networking flexibility: the audio data interface, the host interface, the network topology, and network control. Let's take them in order.
The audio data interface may be the least of your design challenges. Any audio subsystem that utilizes I2S (Inter-IC Sound) or TDM (time division multiplexed) audio data formats can readily transport audio over most digital audio networks.

The host interface, where network modules typically have a control interface to the embedded controller of the audio product, is an aspect of design where special attention needs to be paid to the "switch hitting" concept. The key design principle is to "abstract" the details of the host interface. Ideally, we can allow for multiple network modules by mapping memory to compatible electrical interfaces, and embedding code that accommodates differences in the "devilish details" of host interfaces. For instance, EtherSound using 256 16-bit registers, while CobraNet's host interface is based on a 24-bit address/data space.

Different networks allow different topologies. EtherSound supports both daisy chain and star topologies, while other choices are restricted to star networks. Still other networking options use the same Cat-5e cable that Ethernet uses, but don't work with other equipment such as switches and media converters. These differences don't affect what's "inside the box," but with digital products, technical documentation, help screens, and user manuals are part of the product itself. System designers, installers and end users must be properly informed of the different options that are available to them on different networks. Don't forget that when someone makes a mistake using your product, they usually consider it to be your fault.

The fourth aspect is command and control via the audio network. Designing a "switch-hitting" product requires plenty of forethought in this area. We have found that the key is to abstract the lowest layer of the GUI control application so that network topology and control protocols can be localized in a single area. This does require a certain amount of discipline at the initial design stage. But if the concept is followed rigorously, it becomes easy to pop different "virtual network modules" into the desktop (or laptop) application. Each software object will correspond to a particular hardware network module installed in your audio product.

In today's networked audio environment, "switch hitting" means the ability to evolve with changing technology, not simply to accommodate a fixed range of options. Sure, there's extra engineering time needed up front, as well as ongoing support issues. But just as switch-hitters can help baseball teams win games, products with the ability to support different audio network transports can help you win business. And that is, after all, the name of the game.