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24/192 music downloads make no sense

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Re: 24/192 music downloads make no sense

#181

Post by nullc »

lmm wrote: post #112
ska wrote: post #56

Earlier quoted context omitted.

No, dithering (properly) is usually what you should be doing when you quantize. See Vanderkooy and Lipshitz 1987 for why.

Paper seems to be paywalled. I can't imagine any possible purpose for dithering before encoding that wouldn't be better served by dithering on playback.

At 16 bits dithering is probably pointless for listening purposes.

What dithering does is it decorrelates the quantization noise with the signal. Absent it, quantization generates harmonic spurs. In theory, on a very clean and noiseless signal these harmonic spurs might be more audible than you'd expect from the overall quantization level.

In practice, 16 bits is enough precision that these harmonics are inaudible even in fairly pathlogical cases. But quantization eliminates the potential problem by replacing the harmonic content with white noise.

Adding noise on playback just adds noise, it would not remove the harmonic generation.

The _best_ kind of dithering scheme is a subtractive dither, where noise is added before quanitization and then the _same_ noise is subtracted from the dequantized signal on playback. This is best in the sense that it's the scheme that completely eliminates the distortion with the least amount of additional noise power. But it's not ever used for audio applications due to the additional complexity of managing the synchronized noise on each side.

Re: 24/192 music downloads make no sense

#182

Post by xiphmont »

rplst8 wrote: post #83

First, let me state that I believe that CD audio, played through a modern DAC and quality stereo equipment is pretty much the pinnacle of home audio listening. That is to say, I think 44.1kHz 16-bit PCM audio is plenty good and I'm in no rush to replace my CD collection, nor do I think significant investment in higher bandwidth audio (for playback, mixing and mastering are another story) buys you much. That said, the…

>That said, there's one thing the article does not address and that is "beating", or really inter-modulation distortion from instrumental overtones.

Beating and intermodulation distortion are entirely different things. They look similar on an oscilloscope, but they're not and they don't sound the same.

>Instruments are not limited to 20-20kHz. They can have overtones well above this range.

Correct. You can't hear the overtones beyond the upper portion of the hearing range (many people believe you can).

>In a real listening environment (i.e. live performance) these overtones have a chance to interact with one another in the air.

In reality they do not unless you're driving the air so hard the trough rarification is approaching hard vacuum. (That's not actually impossible. It's how ultrasonic audio 'beaming' devices work). Some performances are powerful enough to get close, eg, if you're sitting six feet from the pipe organ.

Once you're driving air so hard it becomes nonlinear, thus introducing intermodulation distortion in the air, that distortion produces actual audible-range distortion products. And because the distortion you're hearing is in the audible range, a recording will sample and reproduce it accurately.

You're hearing the audible _result_ of IMD, you're not somehow listening to the distortion curve itself.

> It is possible that these overtones may beat with one another

You're continuing to confuse beats and IMD, but here you're talking about beat frequencies, so Yes. But beat frequencies are a sort of auditory illusion. If one of the frequencies that would produce a beat is inaudible--- there's no beat. Easy to test, go try it.

> and cause inter-modulation products in the audible range.

IMD is not a beat. Inaudible ultrasonics will produce audible artifacts when the underlying reproduction system is nonlinear (another way of saying 'there's intermodulation distortion'). However, that's a playback artifact. If the IMD products were audible in the original signal, audible range sampling would reproduce them.

If it wasn't audible in the original performance, it should not be part of the recording, and it should not be part of the playback.

Re: 24/192 music downloads make no sense

#183

Post by xiphmont »

idlewords wrote: post #75

I love the idea the author mentions in passing of a dedicated speaker assembly for ultrasonics. This seems like something that could be a huge margin business, and the parts costs would be as low as you wanted.

You're late to the game. Such high margin products have existed for some time. There are even published papers about them()!

The published papers tend to be by the same people making the supertweeters

Re: 24/192 music downloads make no sense

#184

Post by rplst8 »

darkmighty wrote: post #105
tonecluster wrote: post #86

Earlier quoted context omitted.

"...and cause inter-modulation products in the audible range." AFAIK, this is true in acoustic environments under conditions as described in the original post.

There are no inter-modulation products in the sense rplst8 expects. The interaction of waves of 1000Hz and 1001Hz doesn't produce 1Hz waves in linear media. Even if it did produce some new frequencies through some non-linearity (which is negligible in most environments afaik), the recording equipment would capture the low frequency waves produced by those interactions. So the only question is whether there are signif…

The recording equipment won't necessarily pick it up. If the microphones are place very close the instruments relative to the other instruments creating the interaction.

Re: 24/192 music downloads make no sense

#185

Post by lfam »

chillingeffect wrote: post #179
beat wrote: post #169

Earlier quoted context omitted.

I've played acoustic and electric instruments for over 30 years, and recorded numerous albums. Compression is the best tool we have for accurately reproducing the musicality and emotion of a musical performance. Without compression, most recordings would be unlistenable. Don't confuse the foolishness of the loudness wars for "compression is bad". That's like saying the internet is bad because there's porn on it.

I respect your opinion, but it's only your opinion, not a global truth. Compression is a style. There is far more to musicality and emotion than compression. The problem compression solves is that the environments where industrialized cultures now listen in are not dedicated listening areas, but alternately loud and quiet places, so compression makes all parts of the music almost equally loud so there are no drop out…

> it just sounds like a waterfall with a few bandpass filters changing between the verse and chorus.

That's a good way to put it. I hate over-compressed music. It sounds terrible and is no fun to listen to once you notice the issue.

But, are you an audio engineer? I ask because I work in the field, and all engineers I know accept that dynamic range compression is a necessary part of creating recorded music. The problem is when you abuse compression to create a wall of noise with no dynamic range.

It's like autotune: you can use it to correct one bad note, or you can abuse it create T-Pain.

The engineers behind The Pixies and Nirvana [1], and all dubstep producers use or have used compression at various stages of the creative process.

[1] I guarantee you that whoever mixed Smells Like Teen Spirit spent a lot of time doing the compression on that song.

Re: 24/192 music downloads make no sense

#186

Post by lfam »

earlz wrote: post #119
shmageggy wrote: post #113

Earlier quoted context omitted.

Mastering for vinyl is very common in the industry. I don't have time to dig up a reference right now, but the medium has different constraints than digital so is usually mastered separately, especially for big budget stuff. The differing constraints are mainly that while CD has a hard amplitude limit (hence brickwall limiting), the constraint on vinyl is not hard in the same way -- it mostly has to do with amplitude…

My understanding is that with vinyl, if the signal has too high of an RMS at low frequencies the needle can literally skip off the groove, and for this reason vinyl can't necessarily be as compressed and loud..

This is true. Mastering for vinyl is basically a completely different set of skills than mastering for other media.

Re: 24/192 music downloads make no sense

#187

Post by cdcarter »

lfam wrote: post #185
chillingeffect wrote: post #179

Earlier quoted context omitted.

I respect your opinion, but it's only your opinion, not a global truth. Compression is a style. There is far more to musicality and emotion than compression. The problem compression solves is that the environments where industrialized cultures now listen in are not dedicated listening areas, but alternately loud and quiet places, so compression makes all parts of the music almost equally loud so there are no drop out…

> it just sounds like a waterfall with a few bandpass filters changing between the verse and chorus. That's a good way to put it. I hate over-compressed music. It sounds terrible and is no fun to listen to once you notice the issue. But, are you an audio engineer? I ask because I work in the field, and all engineers I know accept that dynamic range compression is a necessary part of creating recorded music. The probl…

Obviously there is a difference between "excessive compression" (the term the GP used...) and "no compression at all" (what you seem to be arguing against).

Re: 24/192 music downloads make no sense

#188

Post by darkmighty »

rplst8 wrote: post #184
darkmighty wrote: post #105

Earlier quoted context omitted.

There are no inter-modulation products in the sense rplst8 expects. The interaction of waves of 1000Hz and 1001Hz doesn't produce 1Hz waves in linear media. Even if it did produce some new frequencies through some non-linearity (which is negligible in most environments afaik), the recording equipment would capture the low frequency waves produced by those interactions. So the only question is whether there are signif…

The recording equipment won't necessarily pick it up. If the microphones are place very close the instruments relative to the other instruments creating the interaction.

If no recording equipment would pick it up, no human would pick it up either.

Quoting xiphmont

> Once you're driving air so hard it becomes nonlinear, thus introducing intermodulation distortion in the air, that distortion produces actual audible-range distortion products. And because the distortion you're hearing is in the audible range, a recording will sample and reproduce it accurately.

> You're hearing the audible _result_ of IMD, you're not somehow listening to the distortion curve itself.

Re: 24/192 music downloads make no sense

#189

Post by lfam »

some-guy wrote: post #82

This article hits close to home: before I became a programmer I worked as an audio engineer at a fledgling studio in my hometown. The amount of misinformation / junk-science in the audio world is preposterous. There's a religious-cult of an industry that feeds off the ignorance and placebos of its participants. I have many friends who swear by their What.cd 24/192 FLAC vinyl rips and spend hundreds of dollars on audi…

In the case of sites like what.cd, I think that FLAC 16/44 rips of CDs and vinyl are useful for creating distributed backups of our cultural corpus. But I agree that 24/192 FLACs of vinyl are ridiculous.

Re: 24/192 music downloads make no sense

#190

Post by schiffern »

nullc wrote: post #181
lmm wrote: post #112

Earlier quoted context omitted.

Paper seems to be paywalled. I can't imagine any possible purpose for dithering before encoding that wouldn't be better served by dithering on playback.

At 16 bits dithering is probably pointless for listening purposes. What dithering does is it decorrelates the quantization noise with the signal. Absent it, quantization generates harmonic spurs. In theory, on a very clean and noiseless signal these harmonic spurs might be more audible than you'd expect from the overall quantization level. In practice, 16 bits is enough precision that these harmonics are inaudible ev…

> But it's not ever used for audio applications due to the additional complexity of managing the synchronized noise on each side.

Mersenne twister with a shared seed in metadata?

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