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Barber: Digital Alignment a “Huge” Issue

Ben Barber is president/CEO of Inovonics Inc. This is one in a series of occasional interviews with executives of our industry’s technology suppliers.

RW: Digital time alignment is one of the quality control issues we hear mentioned as a concern for HD Radio broadcasters. How serious a problem is this, and what do listeners hear as a result?
Barber: The alignment between analog FM and HD Radio is a huge issue. Everyone is used to tuning in their radio and hearing music start playing. That’s great, and that still happens even with the presence of HD Radio, but the difference now is that a few seconds later they hear a stutter or a skip in the audio and wonder what just happened. Is my radio broken? If it’s a brand-new car and you just paid big bucks for it, this is not acceptable. If you pressed your foot on the accelerator pedal and the car “hiccupped” or “stuttered” a few seconds later, you bet you’d drive that car back to the dealer and demand that they fix it.

This is exactly what happens when the FM and HD Radio time alignments are off. Car dealers are getting the brunt of the frustration and they don’t have the power to do anything. Worse than that, if someone tunes in station “A” and the problem happens because they are an HD Radio station with their time alignment off, and station “B” is a traditional FM station without HD Radio, station “B” sounds better because you don’t have the stutter or echo effect.

The problem is exacerbated even worse if your listeners are in a fringe area and the radio is blending in and out of FM/HD Radio mode on a continual basis.

RW: Describe your new product offering; how does it approach this problem?
Barber: Our Justin 808 is a sophisticated yet simple solution for solving the stuttering/echoing problem of FM and HD Radio blending. At NAB 2014 Alan Jurison spoke up and said, “Somebody needs to make a box that goes in line with your HD Radio audio and fixes the issue 24/7,” and that is what we did. The Justin 808 is a single-box solution that you loop your AES audio through and then into your HD Radio exciter. It has an FM and HD Radio receiver in it and monitors both audio signals off air so it’s “hearing” exactly what the listener is hearing.

Typically the HD Radio delay is roughly 8 seconds. If you program your audio processor’s FM chain to have 8.5 seconds of delay, that gives the Justin 808 approximately 0.5 second window to move back and forth in, to perfectly match up the two audio streams.

There’s an alternative mode that the Justin 808 can run in and that’s in the FM air chain. In this mode the delay of the HD Radio is still typically 8 seconds but now the Justin can provide up to 16 seconds of delay in order to align the FM and HD Radio audio.

Though two operating modes are available, we recommend putting it in the HD Radio chain so the broadcaster can take advantage of one more of its features, Audio Level Matching. This is a very slow, long-term gain stage that monitors the audio level of the FM and then matches that level in the HD Radio audio. It can also check for an out-of-phase condition and correct that too.

RW: What goes into creating the DSP correlation algorithms you use?
Barber: An amazing amount of math. Simply put, the Justin 808 records up to 16 seconds of audio from both the FM and HD Radio receiver and then runs it through a correlation routine.

Think of it in a similar way to how radar works. Radar puts out a high-powered pulse of energy that bounces off an object and then is received back by a very sensitive receiver that calculates the time difference between the pulse going out and the pulse being received. This is the theory of how the correlation routine works except that no pulse is sent out, but instead both program channels are recorded and then similarities are found and lined up. It’s actually a lot more complicated than that, but you get the idea.

Once the difference between the two audio sources is calculated, that much delay can slowly be added or subtracted from the audio path so that the two audio channels line up perfectly. By doing this, it is quite reasonable to get the audio alignment stable within ±1 sample and to keep it there.

RW: How is your box different from other devices that address the issue?
Barber: Other boxes receive the audio off air and then send a correction factor to either the audio processor or the HD Radio exciter. This two-step approach works but relies on two boxes “playing nicely together” from different manufacturers. Not necessarily a “match made in heaven.”

Our Justin 808 not only does everything in one box but it gives you powerful graphs and data sets of what is currently happening, and a history of what went on days and even weeks ago. It also can alarm you with email or SMS notifications when something goes out of bounds.

RW: What kind of reaction are you getting from the beta testers of the Justin 808?
Barber: Amazing. We have a number of units on the air around the country right now in major markets being evaluated before we release the product to the industry. Jeffrey Mahaney of Maine Public Broadcasting told us, “We have a working unit that is user friendly, remote accessible and does what we want, control shifts in timing in STL delivery systems.” Paul Shulins of Greater Media Boston said, “The blend is virtually undetectable. The best part is that you can choose to run only the HD audio through the device while leaving the analog alone.” He told us he was very pleased with the reliability and performance in a high RF environment at the Prudential Building in Boston.

The comments have been absolutely positive and most stations are asking to keep their evaluation boxes on the air until we are ready for the full product launch. Our production department is ramping up for initial deliveries as preorders have been very strong. Our target release date is on schedule for six weeks.

Info on the Justin 808 can be found here.