* Posts by Unobtanium

2 posts • joined 26 Sep 2014

How the FLAC do I tell MP3s from lossless audio?

Unobtanium

Re: "Everything between sample points is lost" (@the spectacularly refined chap)

"FOR FUCK'S SAKE HAS NOBODY EVEN BOTHERED TO READ THE ARTICLE?

Read the quote again: "Everything between sample points is lost". If there is a signal faster than that it is gone. That is not conditional on anything. You can argue about whether it is relevant or not but it is gone never to be recovered. That is precisely what Shannon said."

Strident, profane, but wrong. If you understood sampling theory you'd know that frequencies above half the sampling rate are not "gone"; their energy is aliased back down into the baseband (the spectrum is effectively "folded" back on itself). It's actually more complicated than that, but that's close enough for this discussion. The article's phrasing is unfortunate, at minimum, but I lean toward "wrong".

Unobtanium

Re: "Everything between sample points is lost" (@the spectacularly refined chap)

"ultra"-sound meaning beyond sound, I presume?

You can't hear it; that's why we only pass up to about 20 kHz into the recording chain. If it's not present in the input, its not "lost" from the output. Nyquist's theorem is the law. The reproduction of a low-pass signal is essentially perfect - nothing is "lost".

Of course, no real-world implementation is perfect, but there's no big mathematical or philosophical discussion hiding here.

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