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High Definition Radio

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59 pointszdw29 comments

The radio stations I listen to where I live are definitely HD as in "high def" compared to their analog signal. I can hear the high frequencies when HD comes in. Problem is I'm on the edge of HD reception for both stations I like.

I should note that I've heard other HD stations that seem to be doing extreme digital compression that really makes the music sound bad. Mostly pop music.

Yes, I perhaps failed to state one very real advantage... due to the advanced codec and fairly generous bitrate of HD Radio it will pretty universally sound superior to analog FM (unless there's something going wrong somewhere). That said some stations do make the decision to run their HD2 at a much lower bitrate that results in reduced quality, but usually that's done when their HD2 is talk or news programming only, and HDC at low bitrate handles voice pretty well even if it does get some noticeable raspiness in the high frequencies. Because radio tends to have such a bimodal distribution between "mostly music" and "mostly voice" I wondered if there has been work done on using a dedicated speech codec such as CELP or a derivative, but I think that in practice AAC (which uses the MDCT method that is also common for speech coding) performs well enough for low-bitrate speech that a dedicated speech codec would not gain a lot of efficiency or quality. Moreover, since decoding was to be implemented in hardware having any radio station using a different codec would end up driving up the cost of receivers...

People tend to look down on HD radio when I saw "98kbps typical" but it's important to realize that HDC performs very noticeably better than MPEG 1/2 at those bitrates. It does not sound like a <100kbps MP3 would.

Unfortunately, probably due to the low adoption of HD radio receivers it seems surprisingly common for radio stations to have quality problems with their HD audio due to misconfiguration. One station in my market had some kind of failure that resulted in no audio at all on their HD feed and it persisted for over a week.

Interesting, I’ve always thought HD was for High Definition, not Hybrid Digital. I don’t think we have similar radios in Europe.

You don't. In the 00's I was into this tech and largely felt good about the FM implementation, though the initial work did make some very aggressive trade offs, some of which may be improved by now.

One was receiver side synthesized high frequency sound. Initially, real audio cutoff around 5khz and on a Bangles song, a finger cymbal could not be heard. There were some other issues, and I believe it was bumped up to 8.5 or maybe 10 on higher bitrate streams.

Some radios detect the IBOC easily, making seek, scan type functions less useful. My own SONY car radio was impacted. Would tune static, then the station, then static on a scan.

On AM the system was not all that robust, but did deliver low noise, but compression artifact laden audio. To be fair satellite radio does too.

In order to make it work, AM stations had to use a brick wall 5khz filter. Many stations were running 8khz. Major downgrade on nicer radios. It also required analog AM stereo be removed.

Analog stereo worked well and I listened a lot. Fringe areas were good too. Basically the noise floor would come up and eventually the broadcast would go mono, then fade away. Classic AM.

IBOC did not work well, and the difference in sound was jarring! Fringe areas were maybe half too, so very limited range. Buildings and other things made a mess of it all.

Rural flat terrain AM HD worked! I even liked it.

Analog AM Stereo at 8Khz worked better overall everywhere else, but there were not many radios...

I could go on, but AM was a mess and few stations are on air today.

FM sort of happened. There are plenty of stations and the in car experience has been improved a lot.

In Europe we use DAB or DAB+, which use a different frequency and are 100% digital.

Coverage seems to be limited to a few countries. We don't have it at all in Finland.

https://upload.wikimedia.org/wikipedia/commons/8/8a/DAB_cove...

Almost nobody does. There is just no advantage in switching to digital radio, and most likely there never be.

You've never heard it, I suppose? It's not like it's a must, I agree, but it's definitely a big improvement.

I did hear ot, I have it and its a dead birth. Not worth the investment. Instead of classic FM broadcast DAB+ might be aside a while next to FM and.then give way to internet radio.

No FM radio was able to stream my favorite songs without cutting off a lot of important tones. That problem is gone with digital, my speakers became the limiting factor.

Absolutely not. While FM has a bit lower bandwith than healthy ears, digital adds fake high frequencies.

There is just no way to cram enough data in the same signal to make digital any better.

even with AAC compression ?

I guess no, or it is barely worth it. The thing is that FM is very robust. It only needs to be a little bit stronger than competing signals, which doesn't really give much room for data, considering that the typical bandwith is 150kHz or even less in some countries. Which means you could cram in some 150-200kbps before the reception becomes clearly worse, or you need more power than for FM.

The obvious advantage is that more channels fit in the same frequency range. More channels is more money.

Yes, you can do that, but the sound quality is very poor.

No, the sound quality is actually very good, it’s digital and it’s better than mp3 that people listen to all the time. But you can also make the sound quality poor and fit even more channels.

But the important point is that normal people don’t care and they are the target audience.

Digital doesn't imply good. It isn't better than MP3, it's typically 80kbps or less. 48 is not uncommon. It's no better than AM, it's only made sound superficially good with fake high frequencies and often fake stereo. But it's bad. There is just no way to fit that much data into the same channel. You would have to blast it with MW strong transmitters, which would make it much more expensive.

Analog radio is efficient, and there never was such a dearth of channels like with TV. It would be easy to pack in more channels, FM was chosen for quality.

Obviously digital compression means more data fits in the same channel, for audio an order of magnitude with transparent quality.

Nobody cares that the stereo is fake, it’s for radio stations playing mp3 files that have ‘fake stereo’ to begin with.

If you really want to believe that there is some conspiracy going in to change from analog to digital radio with worse results, to force people to buy new stuff, or for whatever reason, go ahead. But it’s not true. The reality is that with DAB+ more stations fit with good quality. Perhaps not good enough for ‘discerning ears’ like yours but clearly good enough for the general public.

No you absolutely cannot increase the capacity tenfold. DAB takes ten times the bandwidth (1536kHz vs 150kHz for an FM channel, albeit without gaps).

There is no conspiracy, it is done completely openly, while almost nobody really wants it.

Be aware that DAB+ is not the same as DAB, it uses far better, more modern compression so you get better audio using less bandwidth.

DAB and DAB+ are robust against multipath interference which means that you can have much more frequency reuse.

Wikipedia has a calculation for how much spectrum is used by one channel, comparing a 192 kbit digital stream to a typical analog FM station. The digital stream is about 3 times more efficient.

Of course you can try arguing that a 192kbit stream is worse than FM quality. But really it isn’t.

Yes it’s different, it’s annoying you need a new radio and sure, in 1% of all cases you get no reception where with analog FM you’d get some barely recognizable noise. But 99% of the time you get crystal clear digital audio, exactly as transmitted, of pretty high quality.

https://en.wikipedia.org/wiki/Digital_Audio_Broadcasting

The problem is that it isn't better. No amount of sweet PR talk, neither any far fetched calcualtion is going to change the very obvious fact it's something that should never be used in practice. It's less reliable, has lower sound quality, uses more energy and is more expensive to both broadcast and receive.

In terms of vinyl is better than cd, yes.

Anyway, whether you want it or not, it’s the future.

No. In terms it's worse as it's worse.

It ends up forgotten once the last patents expire and there is no value to salvage anymore. It's nothing but sunk cost fallacy that should have been stopped back in the 90s before money and careeers were wasted on it.

Too bad. It doesn’t really matter what you or I think about the technology, the people in charge of deciding chose DAB+, for whatever reason you do or do not believe. I’m fine with it, you’re not, it’s irrelevant to anyone but you.

Yes. It's too bad that politicians got corrupted as usual. Not in all countries though, many have shut it down.

There's an ironclad rule of broadcast, and that is given a choice between the number of channels and the quality, they will pick number of channels every time, meaning users will get low effective quality almost all of the time.

Here's a thought experiment to tell you why that is:

Say you have a choice of two stations, or streams. One of them is boring, but is of exemplary quality. The other one is fantastically compelling, but sounds mediocre trending poor frankly.

Which one do you use, and what do you think other people will do?

And the answer really is compelling wins every time. Quality is nice to have, but when more concurrent offerings can be delivered in the same bitstream, the vast majority of broadcasters will do that, because that means more money more ad dollars the whole nine.

Here in my market, we have exactly one full definition, full bitrate television broadcast station over-the-air. It looks amazing. The funny thing is, I don't watch that station much at all.

Every one of the others has 2, 3 sometimes concurrent streams. And they don't look amazing.

In radio, there are a fair number of stations that didn't do the digital system. Of the ones that did, almost all of them have two streams. Same story here, the streams I really like, are low-quality. Such is life.

I expect to see similar choice and quality trade-offs all over the place. The only way to bring quality up to exemplary standards would be to mandate it. Otherwise the majority of broadcasters won't do it.

Also don't miss that one DAB multiplex takes the space of about 10 FM stations.

In the UK they butcher the bitrate and even broadcast in mono just to cram more channels on each frequency. A lot of it sounds worse than analog FM. Pretty horrible practice

Yes I know (and I use) it. But it has arrived quite late than Radio HD

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