6 ms·

High Definition Radio

59 points by zdw 5y ago

giuliomagnifico 5y ago
Interesting, I’ve always thought HD was for High Definition, not Hybrid Digital. I don’t think we have similar radios in Europe.
- ddingus 5y ago
  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.
  - HNHatesUsers 5y ago
- martijnvds 5y ago
  In Europe we use DAB or DAB+, which use a different frequency and are 100% digital.
  - weberer 5y ago
    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_coverage_map.jpg https://upload.wikimedia.org/wikipedia/commons/8/8a/DAB_cove...
  - ElephantsMyAnus 5y ago
    Almost nobody does. There is just no advantage in switching to digital radio, and most likely there never be.
    - emteycz 5y ago
      You've never heard it, I suppose? It's not like it's a must, I agree, but it's definitely a big improvement.
      - jhoechtl 5y ago
        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.
        emteycz 5y ago
        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.
        ElephantsMyAnus 5y ago
        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.
jtbayly 5y ago
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.
- HNHatesUsers 5y ago
- jcrawfordor 5y ago
  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.
  - deleted 5y ago
    [deleted]

59 points by zdw 5y ago

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

ddingus 5y ago
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.
- HNHatesUsers 5y ago
martijnvds 5y ago
In Europe we use DAB or DAB+, which use a different frequency and are 100% digital.
- weberer 5y ago
  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_coverage_map.jpg https://upload.wikimedia.org/wikipedia/commons/8/8a/DAB_cove...
- ElephantsMyAnus 5y ago
  Almost nobody does. There is just no advantage in switching to digital radio, and most likely there never be.
  - emteycz 5y ago
    You've never heard it, I suppose? It's not like it's a must, I agree, but it's definitely a big improvement.
    - jhoechtl 5y ago
      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.
      - emteycz 5y ago
        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.
        ElephantsMyAnus 5y ago
        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.

jtbayly 5y ago

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.

HNHatesUsers 5y ago
jcrawfordor 5y ago
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.
- deleted 5y ago
  [deleted]