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Ask HN: How much digital data could fit on a standard vinyl LP?

10 points| AdmiralGinge | 5 years ago

This came up in a chat at work, and it's got me curious. I've done lossless vinyl rips to preserve stuff I can't find good digital copies of (the Loving Awareness album for example) which came out to about half a gig, but I think that's more to do with the unreasonably overkill sample rate I was using (I know better now!) rather than any meaningful way of measuring data storage because 192 kHz FLAC is going to have a far better noise floor than vinyl.

As vinyl records are fundamentally analogue we need a digital modulation technique, apparently vinyl has about 18 kHz of bandwidth available so perhaps we could employ several frequency-shift keying channels? Could we do better than audio frequency shift keying^1 since vinyl records have more bandwidth available than the phone lines this is used on?

https://en.wikipedia.org/wiki/Frequency-shift_keying#Audio_frequency-shift_keying

7 comments

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[+] PaulHoule|5 years ago|reply
Usually the top performing codec is OFDM or something similar, which is a lot like FSK with a huge number of channels.

You have to equalize that signal to match the capabilities of the channel. I think you can record well past 18k bandwidth with vinyl, this was used to encode quad audio in the classic rock era. That part of the signal rubs off when you play it unfortunately.

[+] AdmiralGinge|5 years ago|reply
Cheers for the heads up about OFDM, I hadn't heard of that before! I wonder if that 18 kHz I've heard is per channel ie the sum and difference channels are both 18 kHz?
[+] hctaw|5 years ago|reply
Napkin math, could be wrong:

At 18kHz per channel and 70dB S/N the Shannon-Hartley theorem suggests the maximum channel capacity of a vinyl record is around 50k bits per second. Note that SH is an ideal metric

So if your LP has 23 minutes of playtime you've got around 69Mbit of storage.