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
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.
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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.
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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 
Cool vid. Watch it!
