5 ms·

Digital radio remains working at much worse SNR than intelligible fuzzy analog.

greesil 2y ago
For comparable BER. I wonder what SNR is needed for speech to be intelligible? To be fair, if someone made a voice encoding only with that had a lot of error correction bits, it would probably work at much longer distances. Some of the codecs are 2 kilobits per second for human voice? That's got to have a way better margin for the same channel bandwidth than analog decoded by the human brain. This way we get the digital advantage and lossy compression.
- moandcompany 2y ago
  You may find the MELP Vocoder and history interesting: https://melp.org/ https://melp.org/ (MIL-STD-3005) MELP targets 2.4kbps, and there are later examples for even lower bitrates (e.g. 1.2kbps, 600bps) One thing to keep in mind is that a lot of these codecs or technologies are designed to operate at very low bit rates because the signal carrier is required to be capable of operation in "contested environments" where jamming and/or other environmental effects are present (and throughput potential is the tradeoff for assurance).
hulitu 2y ago
Citation needed.
- cogman10 2y ago
  https://opus-codec.org/demo/opus-1.5/ https://opus-codec.org/demo/opus-1.5/ Especially for speech, there are aggressive and impressive algorithms that can turn a trickle of bits into understandable voice.
  - sitkack 2y ago
    There isn't an FEC format that uses Opus over a radio signal. We could make one, but analog AM is the best we have for extremely wide area robust voice broadcast.
  - hulitu 2y ago
    The claim was: > Digital radio remains working at much worse SNR than intelligible fuzzy analog. Your opus codec needs to demodulate the signal first.
    - EraYaN 2y ago
      Both of those things can be true, the smaller the bandwidth is you need the more extra information you can pack in your channel width to make it possible to reconstruct a lot of data errors. And modern digital codecs can squeeze data much further than plain analog audio, hence it's easier to get it to go long distances if the system were to have that as a design goal.
      - cogman10 2y ago
        Yup, but I was also specifically pointing out that opus is quite tolerant of missing data (part of the article). With 90% data loss you can still pretty intelligibly understand what is being said. So long as you can get pops of decodable signal, you'll be able to understand what's being said. Using a more robust modulation scheme would also go a long way in improving reach. AM gets it's range benefits not from the modulation used, but from the frequencies it occupies.
Tor3 2y ago
In my anecdotal experience I have to agree (though I dislike digital radio for completely different reasons). The reception is perfect everywhere around here, while FM was very different, from the exact same transmitter point. The same goes for UHF TV, the quality was very sensitive to the exact position of the antenna on my roof, after they switched to digital, using the same frequency and the same transmitter, everything is perfect even though the wind has turned the antenna 90 degrees. I don't bother adjusting it, there's zero need.
- vel0city 2y ago
  A lot of the complaint for "I used to get channel x before the digital transition now I can't" is often because channel x got remapped from VHF to UHF.
  - sidewndr46 2y ago
    When the migration from NTSC to ATSC happened, the transmitter power was often reduced by a large factor as well.
sitkack 2y ago
Is capable of, but does not currently. This isn't an argument for turning off AM radio.

For comparable BER. I wonder what SNR is needed for speech to be intelligible? To be fair, if someone made a voice encoding only with that had a lot of error correction bits, it would probably work at much longer distances. Some of the codecs are 2 kilobits per second for human voice? That's got to have a way better margin for the same channel bandwidth than analog decoded by the human brain. This way we get the digital advantage and lossy compression.

moandcompany 2y ago
You may find the MELP Vocoder and history interesting: https://melp.org/ https://melp.org/ (MIL-STD-3005) MELP targets 2.4kbps, and there are later examples for even lower bitrates (e.g. 1.2kbps, 600bps) One thing to keep in mind is that a lot of these codecs or technologies are designed to operate at very low bit rates because the signal carrier is required to be capable of operation in "contested environments" where jamming and/or other environmental effects are present (and throughput potential is the tradeoff for assurance).

hulitu 2y ago

Citation needed.

cogman10 2y ago
https://opus-codec.org/demo/opus-1.5/ https://opus-codec.org/demo/opus-1.5/ Especially for speech, there are aggressive and impressive algorithms that can turn a trickle of bits into understandable voice.
- sitkack 2y ago
  There isn't an FEC format that uses Opus over a radio signal. We could make one, but analog AM is the best we have for extremely wide area robust voice broadcast.
- hulitu 2y ago
  The claim was: > Digital radio remains working at much worse SNR than intelligible fuzzy analog. Your opus codec needs to demodulate the signal first.
  - EraYaN 2y ago
    Both of those things can be true, the smaller the bandwidth is you need the more extra information you can pack in your channel width to make it possible to reconstruct a lot of data errors. And modern digital codecs can squeeze data much further than plain analog audio, hence it's easier to get it to go long distances if the system were to have that as a design goal.
    - cogman10 2y ago
      Yup, but I was also specifically pointing out that opus is quite tolerant of missing data (part of the article). With 90% data loss you can still pretty intelligibly understand what is being said. So long as you can get pops of decodable signal, you'll be able to understand what's being said. Using a more robust modulation scheme would also go a long way in improving reach. AM gets it's range benefits not from the modulation used, but from the frequencies it occupies.

Tor3 2y ago

In my anecdotal experience I have to agree (though I dislike digital radio for completely different reasons). The reception is perfect everywhere around here, while FM was very different, from the exact same transmitter point. The same goes for UHF TV, the quality was very sensitive to the exact position of the antenna on my roof, after they switched to digital, using the same frequency and the same transmitter, everything is perfect even though the wind has turned the antenna 90 degrees. I don't bother adjusting it, there's zero need.

vel0city 2y ago
A lot of the complaint for "I used to get channel x before the digital transition now I can't" is often because channel x got remapped from VHF to UHF.
- sidewndr46 2y ago
  When the migration from NTSC to ATSC happened, the transmitter power was often reduced by a large factor as well.

sitkack 2y ago

Is capable of, but does not currently. This isn't an argument for turning off AM radio.