HD Radio Time & Level Alignment

For several years I've maintained a web page that lists the time and level alignment error for every Southern California FM station I can receive in HD Radio. Since the alignment can vary with time, I try to update the list every couple months. I've slacked off lately, but I just updated it this morning. Before you visit the page, try to guess how many stations out of the 55 listed have a transparent analog/digital transition, which I define as a delay error within the 68 µs iBiquity spec, no waveform inversion, and a level error magnitude of 1 dB or less.

http://ham-radio.com/k6sti/roster.htm

Brian

Are you serious? Why?

Why? Because if you're driving around and your HD car radio is flipping in and out of HD which is all too common, it's annoying as hell if the audio is stuttering out of sync and the volume is jumping up and down. That's why Ibiquity sets a standard where the audio is supposed to "blend" smoothly back and forth from HD to analog and back again. Brian's point - backed up by data - is that most broadcasters aren't following that standard, just another reason for HD Radio's failure.

It's not unlike regular (non-HD) radios that auto-blend as they transition from stereo to mono as the signal gets weaker, to minimize the audio artifacts. What's not to take seriously about things like that?

On AM I'd rather not hear the awful digital artifacts that come in when it's in digital mode. On FM the difference in quality seems not all that significant to me. I'm trying to figure out a way to turn the HD off completely (I just got a new car). I will say that the latency problem is much improved, however. If the current standard is 68us, the time shift would be not noticeable to most people and even though there may be some stations outside of this window, I'd think you could be outside of it by quite a lot and still not notice it. But again, to my ears on AM the switch-over gives screechy artifacts that suddenly occur in digital. And on FM, I barely notice anything, but there is slight change that is unnatural and I'd rather just turn it all off.

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"there is slight change that is unnatural"

After reading the linked article above, I believe that change I'm hearing on FM could be due to the peak unlimiting going into HD and then limiting when switching back. It does bother me a little, and I'd rather hear a consistent sound. Maybe 1 dB is a little high.

Theater of My Mind said:

Why? Because if you're driving around and your HD car radio is flipping in and out of HD which is all too common,

Click to expand...

This is an old problem of ten years ago. Most major market stations are using devices (Inovonics makes an inexpensive synchronizing device), including all-in-one audio processors that have all but eliminated the delay between analog and HD streams from a listener perspective. A web site to complain about switching in and out of HD by YOUR radio? Subjective on the part of a handful of picky radio hobbyists at best. Certainly not anything your average listener will ever notice nor care about. That being said; I guess everyone needs a hobby.

Kelly A said:

This is an old problem of ten years ago. Most major market stations are using devices (Inovonics makes an inexpensive synchronizing device), including all-in-one audio processors that have all but eliminated the delay between analog and HD streams from a listener perspective.

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As just one of many engineers who are frustrated with this situation I can tell you that it's not as simple as you might think, Kelly. It is an old problem, and it's still with us. Hence the devices from Inovonics (along with Belar and Day Sequerra) to provide feedback to the delay mechanism and automatically keep the delay in sync. But they are far from inexpensive, and you have to have compatible exciters and/or audio processors to make everything work. Time alignment is by far the biggest complaint from consumers regarding HD radio, and if it was as simple as it should be there wouldn't be a large number of out-of-sync stations in the Los Angeles market.

I've always felt that Ibiquity was kind of a company on a shoestring and that's why they were slow to come up with fixes for things like this, among other things. Think about it - where else do you find after-market devices to fix a manufacturing defect? But there are lots of similar examples with Ibiquity. For a long time the Importer would only run on Windows XP, and after Microsoft ended support their solution was to disconnect the computer from the Internet so it wouldn't be subject to exploits. That works, but it just seems backwards. I haven't had to deal with DTS yet, but the support from Ibiquity on this and other issues was less than stellar.

Dave B.

Hi Dave,

I'm not necessarily defending Ibquity, but I don't see this sort of thing as their responsibility, since Ibquity doesn't sell the audio processing to the station, nor the STL path or method, or the transmission equipment. They license the technology. That's about it.

It seems to me that if stations (or their parent companies) bother making the sizable investment to broadcast HD/IBOC on their stations, they should be prepared to add or upgrade hardware and firmware as the technology evolves. According to BSWUSA.com. the Inovonics Justin 808 retails for $3,400.00 and is currently on sale for $2,699.00: http://www.bswusa.com/Audio-Processing-Inovonics-Justin-808-P11072.aspx As part owner of some small market radio stations in Eastern Washington State that don't broadcast HD, even I wouldn't have heartburn spending less than three grand to do what is a required upgrade over the way it was fifteen years ago, nor do I know of any major market stations that are that penny wise and pound foolish.

Kelly A said:

This is an old problem of ten years ago. Most major market stations are using devices (Inovonics makes an inexpensive synchronizing device), including all-in-one audio processors that have all but eliminated the delay between analog and HD streams from a listener perspective. A web site to complain about switching in and out of HD by YOUR radio? Subjective on the part of a handful of picky radio hobbyists at best. Certainly not anything your average listener will ever notice nor care about. That being said; I guess everyone needs a hobby.

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Guess my market (and many of the markets in California) haven't heard of the "inexpensive synchronizing device". My wife (who is not a radio hobbyist) frequently notices the sync issue from analog to digital since we live a bit at the fringe of our metro.

I am not in the industry. As an average listener with an HD radio in my car, I can say I notice this probablem more on AM, especially on AM 980. Drives me nuts.

AM FM listener said:

I am not in the industry. As an average listener with an HD radio in my car, I can say I notice this probablem more on AM, especially on AM 980. Drives me nuts.

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What AM's in Los Angeles are still running HD aside from 980 KFWB?

We've seen several stations turn off their HD in Sacramento.

AM FM listener said:

I am not in the industry. As an average listener with an HD radio in my car, I can say I notice this probablem more on AM, especially on AM 980. Drives me nuts.

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You're right, there is no excuse anymore for noticeable switching delay between an HD1 and analog on FM. That being said, I suspect some listeners are hearing the differences in high frequencies at the HD fringe areas between FM analog and digital, equating that to the same thing as delay. Unless the station rolls off high frequencies on their HD stream to match the analog carrier, that isn't going to change anytime soon.

For AM HD delay adjustment is pretty much the same as when HD rolled out, with the option (that some stations have never used) of locking the delay(s) to GPS. There aren't the same choices of devices used for FM time alignment for AM-HD, I assume because the adoption of AM HD hasn't moved technically past the beginning.

Kelly A said:

Hi Dave,
I'm not necessarily defending Ibquity, but I don't see this sort of thing as their responsibility, since Ibquity doesn't sell the audio processing to the station, nor the STL path or method, or the transmission equipment. They license the technology. That's about it.

Click to expand...

Yeah, I see what you mean, but manufacturers are very limited in what they can do. For example you still don't see an Importer based on Linux or VXWorks or any other embedded technology. It still runs on clunky Windows machines, and it comes compiled that way from Ibiquity. Other than this function you'll be hard-pressed to find a Windows machine as a single point of failure in any broadcast chain. Also, the delay should be a simple thing to correct for - which Ibiquity thought was the case originally (we had a Dextar, and the instructions were simple - it just didn't stay set). When time alignment cropped up as a real-world problem you started to see the equipment manufacturers coming up with solutions to try to sell new transmitters, keeping their business alive. I can't blame them, it's not like radio was exactly a growth industry (until the LPFM era - and that's a whole different ballgame).

Kelly A said:

It seems to me that if stations (or their parent companies) bother making the sizable investment to broadcast HD/IBOC on their stations, they should be prepared to add or upgrade hardware and firmware as the technology evolves.

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Therein lies the problem. It has to do with the lifecycle of a broadcast transmitter vs. a computer. HD Radio is a hybrid, and so far the ROI on HD is minimal for anyone who isn't lucky enough to lease out their HD-2 and/or have it duplicated on a fill-in translator. So the response from management is something like "you want to spend more money on that turkey" or something like that. Even so, a $2,600 expenditure would probably pass muster. The trouble is, these new time-alignment devices only work with certain transmitter chains. If you have to buy a new Omnia, or upgrade your Nautel exciter, or move the processing to the transmitter, or whatever, it can easily increase the price tag to $15,000.00 or more. At that point the response is "just keep resetting it and we'll see if HD really takes off". I'm lucky in that we have one of the more-stable HDE-200's, synced via Ethernet and the only time I have to re-time it is when we reboot the importer. Still, it's an inordinate amount of work considering the number of listeners.

Dave B.

"What AM's in Los Angeles are still running HD aside from 980 KFWB?"

KNX is one.

k6sti said:

For several years I've maintained a web page that lists the time and level alignment error for every Southern California FM station I can receive in HD Radio. Since the alignment can vary with time, I try to update the list every couple months. I've slacked off lately, but I just updated it this morning. Before you visit the page, try to guess how many stations out of the 55 listed have a transparent analog/digital transition, which I define as a delay error within the 68 µs iBiquity spec, no waveform inversion, and a level error magnitude of 1 dB or less.

http://ham-radio.com/k6sti/roster.htm

Brian

Click to expand...

This is noticeably irritating, actually. I like to listen to KYSR - it sounds like they're using two different audio processors for HD and analog. HD-1 I thought was probably 1.5 lower than analog. Your data says 1.4. Trust your ears.

That one is actually very tinny in HD. I've inquired about this many times before, but there has been no change. I suspect an Omnia 6 EXi FM+HD - I've dealt with that exact issue before.

KOST is a prime offender in loudness and density - though the time sync is great on that one.

Some of the stations are absolutely excellent as HD. Others... intermodulation and other headroom artifacts CODEC inherent... not so much.

As far as quality, ones which stand out as really good (particularly in HD) are KCBS, KSWD, KRTH, and KROQ (I particularly like how they float the AGC, which allows far more room to breathe before smattering SBR in the high frequency content - it just sounds timbre natural and dynamic. I would guess an Orban 8600 HD is at work here - it aligns with some of its demonstrated abilities, though I never got to play with one.)