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What's the point of higher sampling rates in audio?, Such as 96 and 192kHz.
stranhoROX
post Oct 16 2011, 18:03
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Could someone explain to me why there are some recordings with sample rates as high as 192kHz? If most of us hear up to 20kHz, wouldn't 44.1kHz or even 48kHz be enough? Or is there other practical aspects besides boosting maximum frequency in higher sampling rates I am not aware of?
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C.R.Helmrich
post Oct 16 2011, 18:18
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Good question! My answer: People record with 96 or 192 kHz simply because they can and because they believe it sounds better. Yes, 48 kHz is enough, and no solid scientific evidence on the perceptual superiority of higher sampling rates has been presented to date. There were some experiments by Dr. Kunchur, for example, but these involved synthetic signals and actually provided more questions than answers. You can find plenty of discussions in older threads here on HA.

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Brand
post Oct 16 2011, 18:29
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Yeah, this has been discussed a lot on HA.

But in short, I think that if (!) we assume that people can't hear frequencies over 20 kHz, then 44.1 kHz should be enough when listening to the final product.

However, using higher sample rates can indeed have some advantages during production. Off top of my head: pitch shifting of samples is more precise at higher sample rates, you get lower latency and some synths and effects might sound better (the good ones should sound good always and oversampling can be used).
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benski
post Oct 16 2011, 20:38
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There are some advantages to recording, mixing and producing in higher samplerates, similar to using higher bit depths. In particular, non-linear digital audio manipulation will produce overtones according to the order of the equation.

For example, tape saturation distortion has an effect roughly equivalent to output=log(input). If we use the fourth order taylor series expansion of log(x)


We will produce distortion overtones at 4x the frequency of the existing frequencies in the input. Using a higher sample rate can help prevent or reduce aliasing due to this effect. Sure, you can upsample before the effect, and then downsample after, but it might be easier (less CPU) to just have the whole processing chain be 192kHz or 384kHz, and use a lowpass filter before the effect to lop off any input spectra that would lead to aliasing.

Another advantage is that resonant IIR filters (the kind used in synthesizer filters and guitar effects) typically have non-linear responses between theoretical Fc and actual Fc (due to frequency warping and the non-linear effects of resonance, especially if you use a sub-sample delay in the feedback path to compensate for phase differences, see section 5.3 of http://dafx04.na.infn.it/WebProc/Proc/P_061.pdf). It might be mostly linear, however, to Fs/8, so using a higher sample rate allows the usable audio band to have a linear (and predictable) response to the filter controls.

This post has been edited by benski: Oct 16 2011, 21:21
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saratoga
post Oct 16 2011, 21:32
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QUOTE (Brand @ Oct 16 2011, 13:29) *
However, using higher sample rates can indeed have some advantages during production. Off top of my head: pitch shifting of samples is more precise at higher sample rates, you get lower latency and some synths and effects might sound better (the good ones should sound good always and oversampling can be used).


True, but if you can always record at 48k, upsample to 192k for processing, and then downsample again for distribution if you think your software has problems (really bugs...) at lower sample rates. So thats not really a reason to record at 192k, only a reason you might want to use it to work around problems with software.
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Canar
post Oct 16 2011, 21:50
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Trivial case where higher-sampling rates can become audible: Slowing the recording down. For playback at 1/N times the original speed, you need N times the sampling rate to capture all audible frequencies.

This post has been edited by Canar: Oct 16 2011, 21:50


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Notat
post Oct 16 2011, 22:48
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+1 to saratoga

Canar's scenario is applicable to recordings of bats. I don't think you generally want formerly ultrasonic material to become audible on a slowed recording.

There have been demonstrations where listeners can reliably distinguish 48 and 96 kHz recordings. There are generally more variables in play (e.g. ADC behavior) than just sample rate in these trials.

Production engineers like to think of their process as an information funnel. They capture enormous amounts of information and, as they work, whittle it down to what they want people to hear in the final product. In this context, many are comforted by recording equipment and procedures that capture much more than necessary.
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krabapple
post Oct 17 2011, 03:57
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QUOTE (Notat @ Oct 16 2011, 17:48) *
There have been demonstrations where listeners can reliably distinguish 48 and 96 kHz recordings. There are generally more variables in play (e.g. ADC behavior) than just sample rate in these trials.


Links?
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Juha
post Oct 17 2011, 04:14
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Still there are plenty of audiointerfaces which won't give flat enough frequency response when running @44.1kHz (nor @48kHz) mode but, does it when set to 96kHz or higher.

(IIRC, many plug-ins (VST) works @192kHz (or maybe even at higher samplerate) internally.)

Juha
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2Bdecided
post Oct 17 2011, 10:07
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@benski,

...but if you're simply relying on the high sample rate to keep processing aliases out of the audible band, you need to go into the MHz for some operations. Or do them in a smarter way. I agree that keeping the base Nyquist limit a little higher when you're resampling through each of many different DSPs can help in an objective and measurable sense: it can mitigate some of the effects of careless processing and/or resampling in each DSP module. This can be audible is the processing is bad enough - e.g. really trashy resampling. But is the improvement enough to turn trash into perfection? No.

C.R.Helmrich's response is right IMO - people do it because they can, and they believe it sounds better. Despite an almost total lack of any corroborating evidence. Plus a few people will pay more for a recording at a higher sample rate, for the same reason.

EDIT Examples:
http://www.soundkeeperrecordings.com/purchase.htm
http://www.paulmccartney.com/bandontherun/gbp.html

I guess the question becomes: why wouldn't you do it? If it costs nothing, and sells one more copy, or lets you charge some people more, or gets you bragging rights in some circles, then it's "worth it" - even if the technical benefit is zero.

Cheers,
David.

This post has been edited by 2Bdecided: Oct 17 2011, 10:11
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benski
post Oct 17 2011, 11:47
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QUOTE (2Bdecided @ Oct 17 2011, 05:07) *
@benski,

...but if you're simply relying on the high sample rate to keep processing aliases out of the audible band, you need to go into the MHz for some operations. Or do them in a smarter way. I agree that keeping the base Nyquist limit a little higher when you're resampling through each of many different DSPs can help in an objective and measurable sense: it can mitigate some of the effects of careless processing and/or resampling in each DSP module. This can be audible is the processing is bad enough - e.g. really trashy resampling. But is the improvement enough to turn trash into perfection? No.
David.


Sure, but for polynomial equations (or polynomial approximations of transcendental functions), the aliasing is predictable. Because multiplying two signals M and N will produce a sideband at M+N, each polynomial order will require an equivalent increase in sampling frequency. Certainly there are other aliasing-reducing techniques such as using an all-pass for fractional delays and minBLEP for waveform generation, but for resonant IIR filters, especially, the higher sample rate can really make a difference (and admittedly most plugins probably upsample/downsample internally)

Note that I'm not at all trying to imply that high sample rate in final, delivered, consumer audio is justified. I'm just pointing out that doing the mixing and production at high sample rate is worthwhile. And if you already have a 192kHz master, why not try to sell it for a few bucks more?
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Northpack
post Oct 17 2011, 16:34
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QUOTE (benski @ Oct 17 2011, 10:47) *
And if you already have a 192kHz master, why not try to sell it for a few bucks more?

Because you don't want to make your money by fooling people?
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dhromed
post Oct 17 2011, 17:05
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QUOTE (benski @ Oct 17 2011, 12:47) *
And if you already have a 192kHz master, why not try to sell it for a few bucks more?


Great, so why not sell the 44.1 version for a few bucks less?
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knutinh
post Oct 17 2011, 18:34
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QUOTE (benski @ Oct 17 2011, 12:47) *
I'm just pointing out that doing the mixing and production at high sample rate is worthwhile.

Sounds to me like a sound engineer wasting bandwidth, storage and money assuming that he is better at analyzing dsp algorithms than the guy designing the dsp algorithm was. If a given algorithms works better at 192kHz than 44.1kHz, why didnt the algorithm designer just do the resampling internally? Or redesign the algorithm so that it worked satisfactory at the lower rate?


Not saying that there could never be a situation where what you are saying makes sense for the well-informed technician, but I get the feeling that we could have better sounding CDs and radio transmissions if sound engineers stopped thinking of sample rates and focused on how to _use_ their EQs and dynamic processors instead.

-k

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Wombat
post Oct 17 2011, 18:45
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QUOTE (dhromed @ Oct 17 2011, 18:05) *
QUOTE (benski @ Oct 17 2011, 12:47) *
And if you already have a 192kHz master, why not try to sell it for a few bucks more?


Great, so why not sell the 44.1 version for a few bucks less?

They do sell both versions sometimes at least. Reading the reviews of such sales and how much better the 96kHz version sounds and with 192kHz even the micro-macro details come to shine you have to wonder. smile.gif

Enough said about PCM. PCM is so yesterday. Real audiophiles need DSD these days. I see the market for this slowly coming.
All ways of playing PCM and forcing DSD to be PCM on PCM hardware is just bad!! You need to buy DSD DACs and DSD recordings, this is the real deal today
----Sarcasm mode off----

Sorry if some think this is OT but these days DSD is part of the Hires delusion.

I lately stumbled across an eye opening thread here on Hydrogen that should be read carefully. Much knowledge in these few pages!
http://www.hydrogenaudio.org/forums/index....=37717&st=0
I even have to quote this cool sentense of David here:
"...ultrasonic information is somehow audio - this is plain and simple 'all the ultrasonic junk changes the way imperfect audio equipment works'"

This post has been edited by Wombat: Oct 17 2011, 18:48
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HTS
post Oct 18 2011, 03:45
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Do microphones have to be good enough to take advantage of the high sample rates? Otherwise why not just record at 44.1 and up sample to 192khz for release?

http://www.lavryengineering.com/documents/...ling_Theory.pdf

This guy says that microphones don't "respond" to stuff at and over 96khz, and musical instruments don't produce overtones that go that high.
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saratoga
post Oct 18 2011, 03:47
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QUOTE (HTS @ Oct 17 2011, 22:45) *
Otherwise why not just record at 44.1 and up sample to 192khz for release?


Indeed. Why precisely processing needs to be coupled to the recording and distribution is beyond me. Its very easy to change the sampling rate, and all kinds of DSP processing do just that in practice.
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FreaqyFrequency
post Oct 18 2011, 04:12
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There are, in fact, at least two omni capsules out there now which extend well beyond 20 kHz, both made by Microtech Gefell: MK222, and MK221. The 222 is flat within +/- 1 dB from 0.5 Hz to 80 kHz, and the 221 is the same spec from 10 Hz to 80 kHz. So there exist microphones do now have the ability to capture those sounds, but it will remain true that human beings cannot hear them.

The only usage I could see for high sample rates is for recording and analysis of high frequency sounds in nature. As Lavry explains (quite well) in that white paper, there is just no justification for such high rates when working with a human audience. All filtering can be dealt with benignly at the antialiasing stage using DSP, and after that there should be no issue getting proper, accurate results with 44.1 as a final delivery format.

This post has been edited by FreaqyFrequency: Oct 18 2011, 04:24


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Dirk95100
post Oct 18 2011, 05:06
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QUOTE (knutinh @ Oct 17 2011, 19:34) *
QUOTE (benski @ Oct 17 2011, 12:47) *
I'm just pointing out that doing the mixing and production at high sample rate is worthwhile.

Sounds to me like a sound engineer wasting bandwidth, storage and money assuming that he is better at analyzing dsp algorithms than the guy designing the dsp algorithm was. If a given algorithms works better at 192kHz than 44.1kHz, why didnt the algorithm designer just do the resampling internally? Or redesign the algorithm so that it worked satisfactory at the lower rate?


This.



Mics that have a high frequency responce, also produce more noise. So total resolution does not increase with just adding frequency responce. Its a thing explained by information theory. You can not have the cake and eat it.
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hellokeith
post Oct 18 2011, 07:14
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Seems like a worthwhile experiment would be to run a set of samples - all from the same source but at different sampling rates - through a series of mixing, eq, fx, etc and then examine if the highest sampling rate sample has fewer issues from the series of processes.

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unekdoud
post Oct 18 2011, 08:01
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QUOTE (stranhoROX @ Oct 17 2011, 01:03) *
Could someone explain to me why there are some recordings with sample rates as high as 192kHz? If most of us hear up to 20kHz, wouldn't 44.1kHz or even 48kHz be enough? Or is there other practical aspects besides boosting maximum frequency in higher sampling rates I am not aware of?


I doubt my answer is accurate, but the first thing that came to mind is that the same 192kHz signal can be downsampled to both 44.1 and 48kHz without creating artifacts. If the audio was recorded at 44.1kHz and resampled to 48kHz the result would be different from just recording at 48kHz.
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2Bdecided
post Oct 18 2011, 11:26
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QUOTE (Northpack @ Oct 17 2011, 16:34) *
QUOTE (benski @ Oct 17 2011, 10:47) *
And if you already have a 192kHz master, why not try to sell it for a few bucks more?

Because you don't want to make your money by fooling people?
It's retailing. It's based on fooling people, and people want to be fooled. They want to believe expensive food tastes better, for example. They want to read about all the reasons it tastes wonderful. The sunshine in the fields. The beautiful maidens who picked each crop by hand. Reading about all those reasons will make the food taste better to them - even though none of those reasons changes the actual taste of the food at all.

The biggest problem IMO is when there's only fooling, and real progress disappears where it might otherwise have been possible and beneficial. Also, where outright lies are told.

I don't mind a free market where several quality levels are offered; I can try them, and pay for the one I find acceptable.

I know certain people will claim that they hear differences I cannot. However, with all these quality levels available, I can set up rigorous ABX testing wink.gif


Anyway, back to reality: if you are making high quality recordings, and some of the people purchasing your high quality recordings want to pay you $10 extra for a 192kHz version, why on earth wouldn't you make one available? As long as it doesn't make the quality worse, and doesn't cost you more than the financial return, it's really not a problem if people want to pay more for no tangible benefit.

I think it should be quite clear to anyone here that it's of no audible benefit what-so-ever, but it may create an excuse (that the accountants will accept) to create better (re-)masters. Which will then be used for the 44.1kHz version that can now be bought for a bargain price. wink.gif Everyone's a winner.

Does this explain why parts of the industry are heading down this route? And those who should speak out, don't? Granted, it could be The Emperor's New Clothes all over again, but I suspect many people know exactly what they're doing.

The downside is that we don't get proper surround. Though some people are still quietly working on that too.

Cheers,
David.
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Dirk95100
post Oct 18 2011, 12:33
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QUOTE (2Bdecided @ Oct 18 2011, 12:26) *
Anyway, back to reality: if you are making high quality recordings, and some of the people purchasing your high quality recordings want to pay you $10 extra for a 192kHz version, why on earth wouldn't you make one available? As long as it doesn't make the quality worse, and doesn't cost you more than the financial return, it's really not a problem if people want to pay more for no tangible benefit.

I think it should be quite clear to anyone here that it's of no audible benefit what-so-ever, but it may create an excuse (that the accountants will accept) to create better (re-)masters. Which will then be used for the 44.1kHz version that can now be bought for a bargain price. wink.gif Everyone's a winner.


Not necessaraly so....

A general rule of measurements is that accuracy and measurement time are related. Low measuring times means low accuracy and high accuracy means long measuring times.
So there comes a time that while you think you increase the amount of information (increase sampling rates), you are actualy decreacing the amount of information. Again information theory explains this all.
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Cavaille
post Oct 18 2011, 13:34
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Guys, you all disappoint me. The point of higher sampling rates is capturing at best quality possible, regardless if the quality improvement to 16/44.1 is only theoretical. The point is: you can always dowsample later. Really, all your shiny, biting and ironic arguments would have made sense ten years ago but in present times itīs completely superfluous: nowadays we have plenty of HDD space, more than capable hardware, fast processing (even 32/384.000 can be edited and processed very fast if I may be allowed to indulge in that exaggeration fantasy) and extremely fast internet connections. It just doesnīt make sense to use 16/44.1 or lossy compression nowadays and even less sense to promote it as the only format worthwile.

Did it occur to you that for example the Grammy foundation and the Deutsche Grammophon are doing backups of their precious analogue tapes with 24/192 before the tapes degrade and are lost? They are doing this because for example the IASA recommends it. They also donīt care if the quality is better or not, they just want to capture everything. They apparently do it according to the motto 'Better safe than sorry'. Are you calling them stupid or deluded? They obviously know the times they are in and behave accordingly, they exploit the technical possibilities they have and donīt stand still. Which is what has been missing here since a few years now. You guys are still doing comparisons of lossy formats at 96 kBit/s! Why? The world wonīt need them for much longer. Furthermore, you make fun of people who donīt share your opinion. Granted, some of them deserve it. But for a few years now everyone who promotes something like higher samplerates, 24 bit, hell, anything else that deviates from established norms is treated like a little dumb child. You have become close minded people, living in their own secluded world that is becoming smaller and smaller every day.

This forum clearly has lost its edge, I really feel that the world has turned - but without you.

I will no longer participate here (youīll applaud it, Iīm sure) and I know that sentences will be put out of context. If there would be a delete-button for my profile Iīd use it.


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2Bdecided
post Oct 18 2011, 14:46
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QUOTE (Dirk95100 @ Oct 18 2011, 12:33) *
QUOTE (2Bdecided @ Oct 18 2011, 12:26) *
Anyway, back to reality: if you are making high quality recordings, and some of the people purchasing your high quality recordings want to pay you $10 extra for a 192kHz version, why on earth wouldn't you make one available? As long as it doesn't make the quality worse, and doesn't cost you more than the financial return, it's really not a problem if people want to pay more for no tangible benefit.

I think it should be quite clear to anyone here that it's of no audible benefit what-so-ever, but it may create an excuse (that the accountants will accept) to create better (re-)masters. Which will then be used for the 44.1kHz version that can now be bought for a bargain price. wink.gif Everyone's a winner.


Not necessaraly so....

A general rule of measurements is that accuracy and measurement time are related. Low measuring times means low accuracy and high accuracy means long measuring times.
So there comes a time that while you think you increase the amount of information (increase sampling rates), you are actualy decreacing the amount of information. Again information theory explains this all.
There are two ways to realise this is misleading...

1) It's the RMS noise that typically increases as sampling frequency increases. The dB/Hz noise doesn't. So the noise level within the audio band remains roughly constant as sample rate is increased. When we didn't have enough bits to out-do the real world, the in-band noise fell as the sample rate increased.

2) No ADCs or DACs run at 44.1kHz natively. They run at a higher rate internally. The 96kHz output is no less accurate than the 48kHz output - both are usually derived from the same higher rate version internally. The 96kHz version can't be worse than the 48kHz version.

Cheers,
David.
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