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Last post Author Topic: Why 24-bit/192kHz music files make no sense - and may be bad for you!  (Read 63631 times)

40hz

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It's been a while since I've been over to the xiph.org website. But a heads-up on the Hacker News RSS feed directed me to this excellent article by Redhat's 'Monty' Montgomery entitled:

24/192 Music Downloads...and why they make no sense

cochlea-and-responses.png

Articles last month revealed that musician Neil Young and Apple's Steve Jobs discussed offering digital music downloads of 'uncompromised studio quality'. Much of the press and user commentary was particularly enthusiastic about the prospect of uncompressed 24 bit 192kHz downloads. 24/192 featured prominently in my own conversations with Mr. Young's group several months ago.

Unfortunately, there is no point to distributing music in 24-bit/192kHz format. Its playback fidelity is slightly inferior to 16/44.1 or 16/48, and it takes up 6 times the space.

There are a few real problems with the audio quality and 'experience' of digitally distributed music today. 24/192 solves none of them. While everyone fixates on 24/192 as a magic bullet, we're not going to see any actual improvement.
First, the bad news

In the past few weeks, I've had conversations with intelligent, scientifically minded individuals who believe in 24/192 downloads and want to know how anyone could possibly disagree. They asked good questions that deserve detailed answers.

I was also interested in what motivated high-rate digital audio advocacy. Responses indicate that few people understand basic signal theory or the sampling theorem, which is hardly surprising. Misunderstandings of the mathematics, technology, and physiology arose in most of the conversations, often asserted by professionals who otherwise possessed significant audio expertise. Some even argued that the sampling theorem doesn't really explain how digital audio actually works [1].

Misinformation and superstition only serve charlatans. So, let's cover some of the basics of why 24/192 distribution makes no sense before suggesting some improvements that actually do.

Very interesting argument, and well worth going through and thinking about if you're involved in music production, are a recording musician, or are an interested consumer of digital audio.

Those involved or interested in migrating music collections over to their home theater systems or media server would do well to read and ponder what Monty is saying in this article.

Because it runs counter to much of what I "just know" about audio, I took the time to experiment with sampling rates and do some critical listening over the last few days. Apparently I'm not alone in misunderstanding what I "know" about sampling rates:

Sampling theory is often unintuitive without a signal processing background. It's not surprising most people, even brilliant PhDs in other fields, routinely misunderstand it. It's also not surprising many people don't even realize they have it wrong.

Much to my surprise, I found the information in this article to be spot on as far as my ears were concerned - although YMMV since no two people hear things exactly the same way.

Monty argues further that 192kHz music files not only don't provide the promised benefits their endorsers claim, they actually introduce problems for audio that weren't there before:

192kHz considered harmful

192kHz digital music files offer no benefits. They're not quite neutral either; practical fidelity is slightly worse. The ultrasonics are a liability during playback.

Neither audio transducers nor power amplifiers are free of distortion, and distortion tends to increase rapidly at the lowest and highest frequencies. If the same transducer reproduces ultrasonics along with audible content, harmonic distortion will shift some of the ultrasonic content down into the audible range as an uncontrolled spray of intermodulation distortion products covering the entire audible spectrum. Harmonic distortion in a power amplifier will produce the same effect. The effect is very slight, but listening tests have confirmed that both effects can be audible.
.
.
.
Inaudible ultrasonics contribute to intermodulation distortion in the audible range (light blue area). Systems not designed to reproduce ultrasonics typically have much higher levels of distortion above 20kHz, further contributing to intermodulation. Widening a design's frequency range to account for ultrasonics requires compromises that decrease noise and distortion performance within the audible spectrum. Either way, unneccessary reproduction of ultrasonic content diminishes performance.

There are a few ways to avoid the extra distortion:

1) A dedicated ultrasonic-only speaker, amplifier, and crossover stage to separate and independently reproduce the ultrasonics you can't hear, just so they don't mess up the sounds you can.

2) Speakers and amplifiers carefully designed not to reproduce ultrasonics anyway.

3) Not encoding such a wide frequency range to begin with. You can't and won't have ultrasonic intermodulation distortion in the audible band if there's no ultrasonic content.

They all amount to the same thing, but only 3) makes any sense.


So why be concerned - or just refuse to play the 192kHz marketing game? The article's conclusion sums it up better than I could:

Outro

    "I never did care for music much.
    It's the high fidelity!"
         —Flanders & Swann, A Song of Reproduction


The point is enjoying the music, right? Modern playback fidelity is incomprehensibly better than the already excellent analog systems available a generation ago. Is the logical extreme any more than just another first world problem? Perhaps, but bad mixes and encodings do bother me; they distract me from the music, and I'm probably not alone.

Why push back against 24/192? Because it's a solution to a problem that doesn't exist, a business model based on willful ignorance and scamming people. The more that pseudoscience goes unchecked in the world at large, the harder it is for truth to overcome truthiness... even if this is a small and relatively insignificant example.

    "For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring."
         —Carl Sagan



Great article. Read it! Link here.

 8) :Thmbsup:

----

Note: There's also a very good 30-min introduction video called:A Digital Media Primer for Geeks that's worth watching to get a quick rundown on what all this techspeak is about. Monty does one of the best quick intros ever for this 'confusing for non-professionals' topic.

Might even be worth a watch if you do know most of this stuff. I thought I "knew some" about digital audio, but discovered I was dead wrong about something else I thought I knew about digital video.

"It isn't what we don't know that gives us trouble,
it's what we know that ain't so."
- Will Rogers
;D


Cool vid. Watch it!

 8)
« Last Edit: March 06, 2012, 11:30 AM by mouser, Reason: added image »

Carol Haynes

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I really liked the video - cleared up quite a few misconceptions (and probably spawned a few more too ;))

mouser

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Nice find, thanks for sharing  :up:

Renegade

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Still in Seoul, which means... not totally sober...

But this is a VERY interesting topic for me. I will be looking into it and doing some thinking on it.

My gut reaction is BS. I cannot off the top of my not-so-sober head think of any sort of reason that uncompressed audio would have any sort of issue, perhaps other than size.

Analog to digital, then digital to analog... Seems like the speaker quality plays an important role there...

I need to check this stuff out though. It sounds very interesting!

Slow Down Music - Where I commit thought crimes...

Freedom is the right to be wrong, not the right to do wrong. - John Diefenbaker

superboyac

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Thanks 40!  Fascinating...I never ever thought about that.

As a person who messes around with this stuff, I always found the 24/192 stuff to be a big headache.  The arguments in that article remind me off the similar issues that came up for quadrophonic technology of our hippie era.

I've never really had a chance to do a personal examination of these issues.  With this music stuff, I can't trust anyone.  Whether it's a discussion about monster cables, or mp3 vs. flac,...there's so much fluff to filter through.  And no graphs or written analysis is very effective.  I need to go to someone who has a very hi-fi setup with and personally test all the different audio qualities, and I'll have a better idea.  I've never even tried an epensive headphone amp to answer the question "Does it make $1000 difference?"

40hz

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I cannot off the top of my not-so-sober head think of any sort of reason that uncompressed audio would have any sort of issue

Ah Renegade! ;D Best read the article then. It's anything but off the top of the head or gut.

The issue he raises with ultrasonics and intermodulation distortion is valid and well documented. People running sound clamp down on the high end in the stage mix as much as possible while trying not to remove any more 'sizzle' than necessary. If you don't do that, your 'house sound' gets very harsh and your hi-freq drivers burn out much more often.

The weird thing about digital is the way distortion manifests itself. With analog, distortion generally increases and decreases with the total signal level. With digital, noise is fixed and has this weird way of sounding like it's increasing as you lower the volume. That's not something that occurs in nature, so your lower brain goes into a tailspin subconsciously trying to figure it out. The end result is that humans tend to be bothered (on a gut level) by digital distortion much more than they are by analog distortion. Probably because the way digital distortion behaves is "not of this earth." And on an instinctive level, your brain knows it - and flags it as potential danger.

Which is also why digital recordings sound so "hot." You want to get as much audible signal up above the 'noise floor' as possible in order to mask the fixed amount of quantizing distortion in the signal. So you crank the recording levels. With analog you can only push it up so far without introducing more distortion. So the name of the game with analog is to push it up just short of clipping.

Yup. Times have changed. In the old days, the way to cut back on distortion was to "turn it down." With digital, one way to minimize perceived distortion is to "crank it up."

« Last Edit: March 06, 2012, 01:52 PM by 40hz »

Curt

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The weird thing about digital is the way distortion manifests itself. With analog, distortion generally increases and decreases with the total signal level. With digital, noise is fixed and has this weird way of sounding like it's increasing as you lower the volume. That's not something that occurs in nature, so your lower brain goes into a tailspin subconsciously trying to figure it out. The end result is that humans tend to be bothered (on a gut level) by digital distortion much more than they are by analog distortion. Probably because the way digital distortion behaves is "not of this earth." And on an instinctive level, your brain knows it - and flags it as potential danger.

Well said, and trustworthy.  :up:

However, 24/192 being fragile, is no excuse for Monty's clever argued distortion,
because 24/192 is superior, only the recording may not be.

Stoic Joker

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I don't like it when they digitally remaster things. I liked the way Molly Hatchet sounded on an 8-track back in the day.

This sounds like a new twist on why the old way was better - I like that - I'll have to read more when I have time.

40hz

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because 24/192 is superior,


Because?

Did you read the entire article and understand what he was saying? It's not just about distortion. It primarily deals with using music files at resolutions and sample rates that add no audible improvements to the playback. And that also have the potential to create worse sound in the process. At the very least, he's saying they waste space. At worst, they don't sound as good as theoretically lower resolution sampling sizes..

Also note he's talking about the final playback files (i.e. the ones you buy for your iPod) - not the intermediate work files that get created and used during the recording process. He explains why high sampling rates are not a bad thing when recording or mastering.

He's arguing for the lower sample rate for distributed songs.

 :)
« Last Edit: March 06, 2012, 02:22 PM by 40hz »

superboyac

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You know, this is a really good article and makes a lot of sense of the mysterious world of audiophiles.  Most of us know now that those stupid expensive cables are all a scam for digital music.  Monster cables?  gold plated connectors?  really people?

But the one piece of equipment I have recently accepted as being effective are pre-amps.  And if I'm understanding it correctly, the article actually confirms this belief.  For a given volume, I've noticed equipment with good or better pre-amps makes the sound more pleasing to the ear.  Why?  Well, apparently, for digital music, amplifying the signal reduces the effect of noise...and it's the opposite for analog.

You can tell the difference a pre-amp makes.  Compare a high end Sony mp3 player to an ipod or any other cheapo player.  If you try it with different speakers, different headphones, in the car, in a room...you will soon notice that pre-amping the signal makes it buttery better.

40hz

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But the one piece of equipment I have recently accepted as being effective are pre-amps.  And if I'm understanding it correctly, the article actually confirms this belief.  For a given volume, I've noticed equipment with good or better pre-amps makes the sound more pleasing to the ear.  Why?  Well, apparently, for digital music, amplifying the signal reduces the effect of noise...and it's the opposite for analog.

Bingo!

Which is why one of the more expensive devices you'll find in any recording studio are the outboard preamps. It's also the main thing that separates a PA or "live" mixing board from a studio console - the quality of the preamps.

Note: Good info on preamps (along with tons of other stuff) can be found here. I'm a big fan of Sweetwater. One of the best info sources and suppliers of all things musical. If you're a "music creative" looking for rock solid information and advice, browse their site and/or give them a call. They're fantastic. I usually don't buy anything musical (that doesn't have strings on it) without talking to them first.
 :Thmbsup:
« Last Edit: March 06, 2012, 05:07 PM by 40hz »

superboyac

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But the one piece of equipment I have recently accepted as being effective are pre-amps.  And if I'm understanding it correctly, the article actually confirms this belief.  For a given volume, I've noticed equipment with good or better pre-amps makes the sound more pleasing to the ear.  Why?  Well, apparently, for digital music, amplifying the signal reduces the effect of noise...and it's the opposite for analog.

Bingo!

Which is why one of the more expensive devices you'll find in any recording studio are the outboard preamps. It's also the main thing that separates a PA or "live" mixing board from a studio console - the quality of the preamps.

Note: Good info on preamps (along with tons of other stuff) can be found here. I'm a big fan of Sweetwater. One of the best info sources and suppliers of all things musical. If you're a "music creative" looking for rock solid information and advice, browse their site and/or give them a call. They're fantastic. I usually don't buy anything musical (that doesn't have strings on it) without talking to them first.
 :Thmbsup:
I second that.  I bought some keyboard equipment from them several years ago and was shocked at how good their customer service was.  I remember having like 1/2 hour conversations on the phone about mind-numbingly dull audio geek topics.

IainB

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Thanks for this @40hz. V interesting post and links.
It is in line with and updates my research from some years ago, providing some new material - so I have learned some new things.

Nowadays I usually listen to all my music via headphones on my laptop, from mp3's at 128kHz. I had always been skeptical of the need for using 192kHz and considered it to be inefficient in space terms and with no perceptible benefit in my case.

I guess the important variable in all of this is really your native hearing faculties, which tend to deteriorate with age and you tend to also gradually lose your pitch sense. That means the requirement for high fidelity that you might have had drops off with age. Fortunately, I used to  use earplugs when I went to noisy places - e.g., discos or pop music concerts - so my hearing is still pretty acute, but I can't really hear bats squeaking anymore, though I can still hear around 8kHz tones quite clearly in the upper registers, and bass always gets through (can be uncomfortable).

superboyac

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Thanks for this @40hz. V interesting post and links.
It is in line with and updates my research from some years ago, providing some new material - so I have learned some new things.

Nowadays I usually listen to all my music via headphones on my laptop, from mp3's at 128kHz. I had always been skeptical of the need for using 192kHz and considered it to be inefficient in space terms and with no perceptible benefit in my case.

I guess the important variable in all of this is really your native hearing faculties, which tend to deteriorate with age and you tend to also gradually lose your pitch sense. That means the requirement for high fidelity that you might have had drops off with age. Fortunately, I used to  use earplugs when I went to noisy places - e.g., discos or pop music concerts - so my hearing is still pretty acute, but I can't really hear bats squeaking anymore, though I can still hear around 8kHz tones quite clearly in the upper registers, and bass always gets through (can be uncomfortable).
IainB...you're using the numbers 128, 192 in reference to your mp3 files...are you sure you mean kHz?  Don't those refer to the kbps of the mp3?  kHz is a whole other thing.  Personally, I can totally tell the difference between 128 kbps vs. the higher bitrates like 192, or even 320.  I'm betting most of your mp3s are 44.1 kHz and 128 kbps.

nudone

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I can also tell the difference between 128 and 192 kbps, a very obvious difference in the high end I'd say. Though, clearly, depends on what you are listening to and how well your ears are working.

mouser

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Nudone you do not count, your sensory perception exceeds that of humans.

40hz

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Nudone you do not count, your sensory perception exceeds that of humans.

That's right. Nudone is a god! ;D
« Last Edit: March 07, 2012, 09:59 AM by 40hz »

Innuendo

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Nowadays I usually listen to all my music via headphones on my laptop, from mp3's at 128kHz. I had always been skeptical of the need for using 192kHz and considered it to be inefficient in space terms and with no perceptible benefit in my case.

Not only is hearing a factor, but what genres of music you listen to as well. The lossy compression of MP3s is more well suited to some types of music than others.

(All this talk reminds me of a few months ago when I had to replace my dead Klipsch ProMedia Ultra 5.1 speakers for my PC. What a trip down the rabbit hole that was....with the time invested in researching what to buy...yeesh!)

Innuendo

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Nudone you do not count, your sensory perception exceeds that of humans.

Depends on the source material. You can easily tell the difference between 256 bit-rate and 320 bit-rate on certain songs. Crashes of cymbals during certain musical stretches are often the most telling.

40hz

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27 more pages worth of good reading on sample rates and theory in this paper by Dan Lavry of Lavry Engineering, Inc. LE is one of the leading names in high-end professional audio production and engineering. Makers of gorgeous, powerful, and very $$$$ rack gear. (Note: link is for PDF.)
 8) :Thmbsup:

IainB

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IainB...you're using the numbers 128, 192 in reference to your mp3 files...are you sure you mean kHz?  Don't those refer to the kbps of the mp3?  kHz is a whole other thing.  Personally, I can totally tell the difference between 128 kbps vs. the higher bitrates like 192, or even 320.  I'm betting most of your mp3s are 44.1 kHz and 128 kbps.
Yes, UR quite right - I am confusing the two (kHz and bps). My apologies. I know the difference as well. Stupid of me. Ahem...something I was drinking at the time...I slept like a log last night and felt rather thick-headed on waking this morning.     :-[
I think I must have gone hastily through the whole of the post with the misconception of confusing bps with kHz - except, I think, when I mentioned the 8kHz tone that I can hear.

Also, though I used to be a bit of an audiophile (I even used to build my own pre-amp and amp), my hearing might now be shot, compared to yours. Nowadays, I rather suspect that I only imagine that I can tell the difference between 128 kbps vs. the higher bitrates like 192 or 320, and so am not really sure whether it's a true perception - whereas you are sure, it seems.

Yes, my mp3s are of course likely to be mostly 44.1 kHz and 128 kbps.

40hz

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@IainB - if it's any consolation, I know that too - and I still routinely forget or confuse it. So you're not alone.

I had to read Montgomery's article about three times before it sunk in, mainly because I kept getting kHz and kbps (and what they represent) confused in my head and found myself objecting to what he was saying because of it.

Maybe if the number 192 hadn't been used in connection with both... ;D
« Last Edit: March 08, 2012, 08:00 AM by 40hz »

superboyac

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Maybe if the number 192 hadn't been used in connection with both... ;D
;D ;D
I think you're right!!  So true...I totally think if 192 wasn't in both buckets, we wouldn't get so confused about it.  (What's the psychological analysis there?)
I remember the first time I had to deal with 192 as it relates to kHz in a recording setting, and it took me a while before I realized that they're two different things...but until I started recording, I never even thought about the frequency, only the bitrate.

iphigenie

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one think I am picking up from this is that I probably should re-encode all my CDs - that it is likely that the ogg encoder I used in 2000 could have been of lower quality than the one I could use now (although it was not the one in ffmpeg). And I have much better processing power now so it should be less painful.

Who am I kidding, this would take months - there's between 300 and 500 CDs in that basement, if not more :S

IainB

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one think I am picking up from this is that I probably should re-encode all my CDs - that it is likely that the ogg encoder I used in 2000 could have been of lower quality than the one I could use now (although it was not the one in ffmpeg). And I have much better processing power now so it should be less painful.
Who am I kidding, this would take months - there's between 300 and 500 CDs in that basement, if not more :S
That sort of tedium would be makework akin to sharpening a mountain of pencils.       :D