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Comment by cogman10 | Hacker News Reader

> it doesn't degrade gradually as signal gets worse

That has a lot more to do with the dated implementation and less to do with digital radio. There are a number of digital broadcasting techniques which can minimize and compensate for noise, including a slight delay with a signal correction and fault tolerant codecs.

DAB was implemented using the old MPEG2 audio codec. DAB+ uses the now 15 year old codec HE-AAC which isn't really designed to handle corruption. Opus handles loss a lot better (see their examples https://opus-codec.org/examples/ )

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> DAB was implemented using the old MPEG2 audio codec. No, it was MPEG 1 layer 2 often at 192 kbps. Later they switched to HE-AAC with DAB+.

DAB+ uses EEP (and RS) which was deliberately chosen to give better signal quality all the way to the point of losing reception. Old DAB used UEP which degrades faster, but instead of having no signal, it went to a muddier / warbling kind of sound that characterised early DAB receivers.

And technically while some people do call it MPEG2, it's actually MP2, also known as MPEG-1 Audio Layer 2, an audio codec in the same family as MP3 (MPEG-1 Audio Layer 3).

I imagine that today they'd probably use something like Opus and a fountain code or similar, yes... But you can't expect everyone to replace their radio every 10-15 years ;)

> I imagine that today they'd probably use something like Opus and a fountain code or similar, yes... But you can't expect everyone to replace their radio every 10-15 years ;)

Certainly not, which is why I believe DAB (no plus) is still floating around. And I'm not really suggesting that they made a bad choice.

I'm mostly pushing back on the notion that digital means all or nothing audio. If broadcast audio stays alive (which it may not) then I hope the next standard is opus, fountain codes, and QAM-64 or similar so we can stuff a bunch of bits into error correction while still having graceful degradation, better than analog, when the signal degrades.

I could be wrong, but I think DAB uses DQPSK (which can be thought of as a special version of QAM 4 if you squint a bit) and not anything like the higher QAM constellations because it's deliberately designed for mobile (road, train etc) where you don't have a steady signal, it can vary a lot with motion, so QAM 64 wouldn't really be possible.

Though I did a quick check and apparently DRM+ uses QAM-16, so perhaps my knowledge is far too out of date :S

LTE and 5g both use QAM 256 and higher. Wifi 7 can use QAM 4096 (though not a lot of motion there).

That's a good point about LTE/5G. Thanks!

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