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Lossless audio formatsLossless audio formatsPosted Aug 26, 2008 15:36 UTC (Tue) by johnkarp (guest, #39285)In reply to: Lossless audio formats by pr1268 Parent article: Interview with Richard Hulse of Radio New Zealand, on the decision to offer Ogg Vorbis (Groklaw)
Signal sampling *isn't* lossy for information below the Nyquist frequency: perfect reconstruction is possible. Thats what the Nyquist-Shannon sampling theorem shows.
And since audio has a finite bandwidth and bounded resolution, its therefore quite possible to losslessly represent an audio signal using samples.
Also, I don't see how you can claim non-sampled recordings are closer to lossless than sampled ones. The only effective distinction between the two is that the frequency response of non-sampled signal trails off to zero at higher frequencies, whereas sampled signals have a uniform response that cuts off quickly at a particular frequency. The bandwidth of one isn't necessarily greater than the other, it all depends on the particular technology involved.
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Lossless audio formats Posted Aug 26, 2008 16:08 UTC (Tue) by epa (subscriber, #39769) [Link] And since audio has a finite bandwidth and bounded resolution, its therefore quite possible to losslessly represent an audio signal using samples.Does it really have a bounded resolution? Do air molecules move in discrete jumps? I am not a physicist so I don't know the answer, but I kind of assumed that in the real world the resolution is infinite. Of course the human ear has only limited capacity, but that comes back to the same discussion as before: some of the information from the original sound has been lost, but it is not perceptible to ordinary listeners.
Lossless audio formats Posted Aug 26, 2008 16:46 UTC (Tue) by johnkarp (guest, #39285) [Link]
Not exactly, its more that particles, even macroscopic ones, don't *have* exact positions. Only probability distributions describing where you'll measure them to be.
Also, I was being somewhat redundant: since the bandwidth is proportional to resolution, if the bandwidth is finite, the resolution must be too.
Lossless audio formats Posted Aug 26, 2008 16:57 UTC (Tue) by dmaxwell (guest, #14010) [Link] I am not a physicist so I don't know the answer, but I kind of assumed that in the real world the resolution is infinite.That is not a good assumption. Signal to noise ratio and slew rate determine the "resolution" of an analog format like tape or vinyl. To put it another way, signals like what is coming off a mike will do things that either don't wind up on the vinyl or imperfectly on the vinyl. What Nyquist and Shannon do for us is tell us the sample rate we need to reproduce signals at given level of fidelity expressed in dB. If the sample rate is high enough to meet or exceed the vinyl then one cannot fairly say that the vinyl has higher resolution. One reason vinyl often sounds better is that CDs are "hot mixed" by egomanic producers who want to have the loudest record in the jukebox. Google up the "loudness war" for more. A vinyl stylus will literally jump out of the groove if hot mixed the way many CDs are. Hot mixing increases average loudness at the expense of dynamic range. It sounds terrible. It also turns out that the capabilities of human hearing can be objectively quantified and yes CDs exceed that for 99% of individuals. The intersection of "golden ear audiophiles" and that remaining 1% is very very low. If we add the set of people "knowledgeable about the physics of sound, engineering of electronics, and understanding of information theory" then the intersection is all but non-existent.
Lossless audio formats Posted Aug 26, 2008 17:48 UTC (Tue) by pr1268 (subscriber, #24648) [Link] One reason vinyl often sounds better is that CDs are "hot mixed" by egomanic producers who want to have the loudest record in the jukebox. Yes, that's true, but back in the 1980s most CDs were pressed with soft-volume masters created for vinyl phono equalization. While the LP would have effects created on the playback end reversed ("undone") by this equalization, the CDs didn't and thus they sounded like crap (IMO). But I agree that the "loudness wars" have had a detrimental effect on the audio quality of music CDs for the past 12 years or so. My impression is that most CDs mastered from 1988 to 1996 (or thereabouts) sounded best, as this time period was after the mastering engineers wised up to CD equalization and before the loudness wars started. If the sample rate is high enough to meet or exceed the vinyl then one cannot fairly say that the vinyl has higher resolution. As the earlier comment said, analog recordings will have their frequency response tail off slowly at high frequencies, but I don't think that vinyl LPs are limited by a Nyquist frequency--I read somewhere a while back that some high-quality ("extra virgin") vinyl could reproduce audio frequencies all the way to 60 kHz and beyond. Of course, this is all moot considering that:
Lossless audio formats Posted Aug 26, 2008 19:10 UTC (Tue) by vmole (guest, #111) [Link] Yes, that's true, but back in the 1980s most CDs were pressed with soft-volume masters created for vinyl phono equalization. While the LP would have effects created on the playback end reversed ("undone") by this equalization, the CDs didn't and thus they sounded like crap (IMO). "Most" seems unlikely, since it's an obvious mistake. Anyway, even the DDD CDs sounded like crap, often even worse than the AAD CDs. I think a lot of it was that the D/A and A/D converters sucked for audio. Remember the modded CD players of the 80s/90s? Remember the cult of the Burr-Brown D/A converters? They really were much better than the typical $0.05 piece in a cheap CD player.
CD audio issues Posted Aug 26, 2008 20:34 UTC (Tue) by pr1268 (subscriber, #24648) [Link] Anyway, even the DDD CDs sounded like crap, often even worse than the AAD CDs. I agree, but I think a lot of the crappy sound also came from engineers' lack of experience using digital recording/mixing/mastering equipment. Plus, I once heard a recording engineer comment that he felt "artistically and functionally limited" when mixing an album purely in the digital domain (which may explain the appearance of DAD discs in the early 90s). There were a few excellent-sounding DDD discs from the early 80s; Donald Fagen's The Nightfly (1982) was/is one of the nicer-sounding all-digital albums from that era. Remember the modded CD players of the 80s/90s? Remember the cult of the Burr-Brown D/A converters? They really were much better than the typical $0.05 piece in a cheap CD player. Can't say that I have--I would love to have heard a disc played on such a player. Understand that I was a whole lot younger back then and not nearly the hacker I am today. :-)
Lossless audio formats Posted Aug 27, 2008 3:07 UTC (Wed) by pr1268 (subscriber, #24648) [Link] "Most" seems unlikely, since it's an obvious mistake. I stand by my original claim about most early/mid-1980s CDs mastered with vinyl phono equalization (based on an article I read in Stereo Review magazine around 1995), but the "mistake" wasn't so obvious back then. Most CDs were rushed to market using the most convenient master handy--which was often the RIAA Phono-Equalized master. But, in retrospect, I think that the rapid commercial success of the audio CD sort of necessitated getting discs to market quickly. Not that I'm rationalizing the recording industry's decision to do so...
Lossless audio formats Posted Aug 27, 2008 22:04 UTC (Wed) by jrigg (subscriber, #30848) [Link]
RIAA phono equalisation is applied on the way into the cutting lathe, not on the master tape (which has its own IEC or NAB equalisation applied during recording and removed during playback). Some CDs were recorded from master tapes that were optimised for vinyl reproduction, but that's nothing to do with the RIAA equalisation that takes place in the cutting lathe preamplifier.
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