Why is this the case? Well, the USB developers, according to Wright, came to the MIDI community very late in their development stage, and thus the MMA and its Japanese counterpart, AMEI, didn’t have much of a chance to give their input about how MIDI on USB was going to be handled (although Roland, acting on its own, got involved much earlier). On a USB cable, MIDI uses asynchronous timing (that is, there’s no underlying clock as there is with, say, AES/EBU digital audio), which means if there’s a lot of traffic on the line, then the MIDI data will be delivered in fits and starts, and there’s no guaranteed delivery time, even under the best of circumstances. (The same is true for a standard MIDI cable, but preventing this is what multiport interfaces are for!)

Audio on USB, on the other hand, uses isochronous timing, which means the delivery time is guaranteed. So the problem is further compounded by the fact that because they use different timing schemes, MIDI and audio data on the same USB cable can easily lose sync with each other. Getting MIDI and audio to work together in perfect sync is something software and hardware developers have labored hard for years to achieve, and now we’re potentially seeing all those efforts being tossed away.

The interface manufacturers are not unaware of these problems—it’s this very issue that’s behind the huge advertising campaign that MOTU has been running promoting its “MTS,” a proprietary system of time-stamping MIDI events as they enter the USB cable to overcome USB’s timing problems. Time-stamping of MIDI events has never really been necessary before, because the latency and jitter of the synthesizers themselves have been greater than that of any delays in the MIDI network (or the resolution of MIDI itself, for that matter), but that’s no longer true with USB. Emagic has followed MOTU’s lead and is using its own version of time-stamping, and Steinberg is reportedly planning something similar.

But it’s the same old song: None of these solutions are compatible with each other, which negates the entire philosophy of MIDI and USB. MOTU’s MTS works only if you have the company’s software and hardware and not with Emagic’s hardware or Steinberg’s software, and vice versa, et cetera, ad infinitum.

It’s the computer manufacturers who are potentially in the best position to do something about this, and perhaps they will. Mac OS X might include time-stamping in its MIDI drivers, according to some sources. Doug Wyatt, the developer of the Opcode MIDI System, the best software driver for multiport MIDI on the Macintosh (and the primary casualty in the train wreck Gibson has made of that poor company—more on this next month), is reportedly leading the OS X MIDI team, but Apple isn’t saying much about it just yet. (And, sad to say, their corporate track record on MIDI support has been consistently pretty miserable.)

Similarly, according to Jim Wright, the Windows Streaming MIDI API has a 1ms time-stamping feature already built-in, but it only works on output, not on input. Microsoft’s DirectMusic supports time-stamping (at a far greater resolution: 100 nanoseconds!), but apparently none of the hardware interface makers are taking advantage of this yet.

Last April, the USB-IF (led by Intel) announced USB 2.0, in which throughput is increased by a factor of (take a deep breath) 40. Will it solve the timing problems? Until someone comes out with a USB 2.0 computer and a USB 2.0 MIDI interface and someone (else) tests them, we won’t know.

IEEE-1394, though it’s more expensive, seems to hold a lot more promise for the future of MIDI. I’ll talk about that next month, as well as some new and proposed enhancements to the Standard MIDI File spec and (dare it be whispered) the possibility of MIDI 2.0.

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Reprinted with permission from Magazine, January, 2001
© 2001, Intertec Publishing, A Primedia Company All Rights Reserved