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Comment by steve1977 | Hacker News Reader

steve1977

I think the constraint of using a band limited signal is the big misunderstanding many people have in regards to digital audio.

Yes, you can perfectly reproduce a band limited signal as long as the highest frequency is below fs/2.

But to get a band limited signal from a “real life” signal without any artifacts can be trickier than one might think. Especially when the Nyquist frequency is near the limit of human hearing.

And this is the one big argument in favor of Hi Res audio - moving those filter frequencies high above the hearing threshold.

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>And this is the one big argument in favor of Hi Res audio

It's really not. For redbook, fs/2 is 22 kHz and while human hearing maxes at 20 kHz, it's not a hard cutoff: combine our low sensibility to high frequencies (cf ISO 226), the average listener's hearing not going much further than 18 in reality and frequency masking by other simultaneous notes and the small aliasing/imaging issues near fs/2 aren't a real problem.

But the real important factor rarely mentioned is material: the amount of music with meaningful content at a meaningful volume at those frequencies is statistically negligible.

Hi Res audio is snake oil designed to sell the same thing multiple times, period.

And for higher price too.

"Hi Res audio is snake oil designed to sell the same thing multiple times, period."

The "period" is unwarranted, because there are too important caveats. Firstly, it has been extremely common for albums to be sold with very compressed dynamic range, assuming the average consumer will be listening in noisy environments etc. However, the mastering supplied to Hi Res shops sometimes lacks that compression, so that is where you can hear the album with room to breathe.

Secondly, the SACD format allowed adding a layer for 5.1 surround sound. In classical music, this is especially important for works where the performers are spread out around the hall, not just all on stage in front of the listeners.

So, with Hi Res the higher frequencies and 24 bit depth are snake oil, but the ancillary benefits are audible to anyone with a good listening environment.

> However, the mastering supplied to Hi Res shops sometimes lacks that compression, so that is where you can hear the album with room to breathe.

I've almost never heard of Hi Res with a totally new master that wouldn't have been previously available as CD, to be honest. This isn't common, right?

> the SACD format allowed adding a layer for 5.1 surround sound

Well, yeah. Too bad I don't have a PS3 to rip the SACD layer =)

"I've almost never heard of Hi Res with a totally new master that wouldn't have been previously available as CD, to be honest. This isn't common, right?"

It has been a few years now since I did all this collecting, but I do remember instances where the CD was brickwalled, but both the Hi Res downloads and the vinyl release got a mastering with more dynamic range.

Well, if you add vinyl, yeah. I had Celtic Frost's Monotheist in that situation, and I bought the horrible CD first.

> Firstly, it has been extremely common for albums to be sold with very compressed dynamic range, assuming the average consumer will be listening in noisy environments etc. However, the mastering supplied to Hi Res shops sometimes lacks that compression, so that is where you can hear the album with room to breathe

I had a friend who was extolling the virtues of Hi Res for the pop music he was buying so I asked him to send me a track, and it had the same brick compression as the standard iTunes version and sounded just as flat (I was hoping that even if it was compressed the same, the extra resolution meant that you could recover the detail, but there wasn't an audible improvement).

If that's what they want to sell, they need to create an actual term for that, like the audio version of "Director's Cut", not just sneak it into some random Hi Res releases and hope you find "the good ones" while the rest are snake oil.

> Hi Res audio is snake oil designed to sell the same thing multiple times, period

There's a karaoke bar I go to with "Hi Res" logos on the speakers. These are basically MIDI files, in a loud bar atmosphere, who is going to hear the difference, haha.

The only thing really in favor of hi-res audio is that is allows you to have rather lazy circuit design. You can have a super lazy 20 kHz -> 48 kHz anti-aliasing filter that is cheap... or you could just properly make a nice 20-22k sharp filter, and stop wasting all that bandwidth on worthless doubled sample rate audio.

In reality, there is absolutely 0 use for digital audio sampled above 16-bit, 48 kHz for listening. (44.1 kHz is fine too, I guess, but the sample rate is annoying for compatibility with a lot of modern systems) It has uses for music production, but that's about it. Final mix should be 16-bit/48k.

Also, at least according to https://pubs.aip.org/asa/jasa/article/145/1/458/638769/Small... smallest percieved time difference between ears is half the sample time of 44.1kHz

That's unrelated. This difference is the inter-aural or inter-channel difference and 16/44.1k can capture that to much greater precision than microseconds.

Some math [1]

44.1k file containing pulses with sub-sample delays [2]

Something similar, but square wave, and nicely showing that timing precision actually depends on bit-depth and not the sampling rate [3]

Some practical experiments with capturing the playback of such files and verifying that the delay is preserved: pulse [4] and square [5]

[1] https://troll-audio.com/articles/time-resolution-of-digital-...

[2] https://www.audiosciencereview.com/forum/index.php?threads/t...

[3] https://audiophilestyle.com/forums/topic/58511-time-resoluti...

[4] https://www.head-fi.org/threads/can-you-hear-upscaling.97295...

[5] https://www.head-fi.org/threads/can-you-hear-upscaling.97295...

Super thanks! This is exactly the kind of non-handwavy math I have trouble coming upon myself.

It gets much more complicated with more and modern speakers doing room calibration (at least Genelec and Neumann have their own, and Sonos also has some iphone waving trueplay thing). And just saying "Niquist!" does not help to understand, e.g., how precisely can phase be aligned by applying FIR filters, and what impact does the sample rate or bit depth have.

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