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Oversampling converters vs. high SRs



 
 
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  #11  
Old February 9th 19, 07:11 AM posted to rec.audio.pro
nickbatz
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Posts: 97
Default Oversampling converters vs. high SRs

> You need more virgins.

I do get the appeal, but I'm more interested in super-freaky women.

>> > But I don't understand why having more samples to describe a sine wave that can only go one direction or the other makes any sense whatsoever.

>
> It's more of a mastering argument. Everything you do to a waveform adds
> more bits and usually creates harmonics. 24-bits leaves room for the
> bits, and a doubling the sample rate keeps those harmonics that you can
> deal with more gracefully if you leave them there until it's time to
> bring the project back to a standard format.


Increasing the number of bits, I'm with you (because you're keeping low-level detail).

It's doubling the sample rate that makes no sense to me, unless you believe that - again - super-freqs way above hearing and at a really low level make any difference.

In other words, a 20K sine wave - and of course it's all sine waves - sounds identical sampled at 44.1KHz and at 96kHz - basic sampling theory, as you undoubtedly know.

> > I work mostly with instrument plug-ins and sample libraries these days, with occasional live overdubs, so it's not practical to sacrifice half my computer horsepower for such a small improvement - especially when the samples are recorded at 44.1 or 48 anyway.

>
> You won't double your computer usage, but you'll increase it some.


Well, I'm thinking about sample-streaming off drives, not so much running processing plug-ins. Doubling the file size halves the number of voices you can stream before bringing your computer to its knees. It also uses twice as much memory for loading samples into the head-start buffer - i.e. you can't have as many instrument articulations loaded and ready to play.

Having said that, SSDs totally changed the game. And my largest template uses less than 40GB of the 64GB in my main machine. Voice count and RAM aren't unlimited resources, but we've come a long way from the days of needing several slave computers to run a sampled orchestra all at once.

I'm
> not arguing for 2x or 4x sample rates all the time. I record everything
> at 24-bit 44.1 kHz because just about all the recording I do is live, in
> the field. The less crap I record, the less I have to worry about what
> to get rid of. If you like what you're doing, then just keep doing it.


Sure.

> On the rare occasions that I have a paying customer, if he asks for 96
> kHz, I just push that button. The customer may not always be right, but
> doing what he wants makes getting paid more certain.


Nobody can stand to listen to audio that's recorded at only 96kHz. Your customer should pay double for 192kHz, or why even unpack your mics?
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  #12  
Old February 9th 19, 10:06 AM posted to rec.audio.pro
Don Pearce[_3_]
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Posts: 2,250
Default Oversampling converters vs. high SRs

On Fri, 8 Feb 2019 14:00:50 -0800 (PST), nickbatz
> wrote:

>Don, if you read my last post in response to Scott, you'll probably understand my lack of understanding.
>
>I don't really know how else to phrase the question: what is the argument for storing audio files post-converter at anything over 44.1/48 if the filtering is being done way above the audible spectrum anyway?


OK, now I get you. Very little point at all, unless you are doing
something other than reproduce sound. The response of even the best
microphones will go horribly peaky above 20kHz, and it is as well to
get rid of it. All that extra spectrum can possibly do is waste power,
and possibly cause intermodulation distortion down into the actual
audible range.

But - although an A/D that works at 192kS/sec may be wasted digits,
the fact that it has been designed that way is usually a good
indication that its performance at 44.1 will be exemplary. Not always,
but usually.

d
  #13  
Old February 9th 19, 12:46 PM posted to rec.audio.pro
Mike Rivers[_2_]
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Default Oversampling converters vs. high SRs

On 2/9/2019 4:06 AM, Don Pearce wrote:
nickbatz wrote:

>> what is the argument for storing audio files post-converter at anything over 44.1/48 if the filtering is being done way above the audible spectrum anyway?


> OK, now I get you. Very little point at all, unless you are doing
> something other than reproduce sound. The response of even the best
> microphones will go horribly peaky above 20kHz, and it is as well to
> get rid of it. All that extra spectrum can possibly do is waste power,
> and possibly cause intermodulation distortion down into the actual
> audible range.


Ages ago, it seems, a sample company came up with 96 kHz and 192 kHz
sample sets for their pipe organs. Nick probably remembers them. I asked
why, and the reply wasn't absurdly silly. They sample individual pipes.
There are mics that can indeed capture sound above 20 kHz fairly
accurately. What they're sampling has overtones higher than 20 kHz. They
don't travel very far, but they can interact with other overtones and
fundamentals. Call it IM distortion (it is) but that's the way the
instrument works.

When they play back the samples, they have to reproduce those ultrasonic
frequencies, and they do (they sold complete electronic organ systems).
At the time, they needed a rack of about 8 computers to build an organ
playback system. I suspect that after selling two or three systems, they
went out of business or changed their business. But it was an
interesting concept from back in the day when samples were something you
used to make beats, before they were called beats.


--
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  #14  
Old February 9th 19, 05:56 PM posted to rec.audio.pro
John Williamson
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Posts: 1,593
Default Oversampling converters vs. high SRs

On 09/02/2019 06:11, nickbatz wrote:

> In other words, a 20K sine wave - and of course it's all sine waves - sounds identical sampled at 44.1KHz and at 96kHz - basic sampling theory, as you undoubtedly know.


If I'm digitising an analogue source such as a vinyl LP or tape, then
using the highest available sample frequency and bit depth lets me do
more in the way of throwing out clicks and other problems. There might
not be much if anything, recorded above 20 kHz, but clicks and pops go
way up...

Recording live, I record at the sample rate that matches the final
product, so for CD or other audio work, it's 44.1, or, rarely, when I'm
likely to have to clean stuff up drastically, 88.2 kHz, and for video,
it's 48 or 96.


--
Tciao for Now!

John.
  #15  
Old February 9th 19, 07:21 PM posted to rec.audio.pro
Don Pearce[_3_]
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Posts: 2,250
Default Oversampling converters vs. high SRs

On Sat, 9 Feb 2019 06:46:35 -0500, Mike Rivers >
wrote:

>On 2/9/2019 4:06 AM, Don Pearce wrote:
>nickbatz wrote:
>
>>> what is the argument for storing audio files post-converter at anything over 44.1/48 if the filtering is being done way above the audible spectrum anyway?

>
>> OK, now I get you. Very little point at all, unless you are doing
>> something other than reproduce sound. The response of even the best
>> microphones will go horribly peaky above 20kHz, and it is as well to
>> get rid of it. All that extra spectrum can possibly do is waste power,
>> and possibly cause intermodulation distortion down into the actual
>> audible range.

>
>Ages ago, it seems, a sample company came up with 96 kHz and 192 kHz
>sample sets for their pipe organs. Nick probably remembers them. I asked
>why, and the reply wasn't absurdly silly. They sample individual pipes.
>There are mics that can indeed capture sound above 20 kHz fairly
>accurately. What they're sampling has overtones higher than 20 kHz. They
>don't travel very far, but they can interact with other overtones and
>fundamentals. Call it IM distortion (it is) but that's the way the
>instrument works.
>
>When they play back the samples, they have to reproduce those ultrasonic
>frequencies, and they do (they sold complete electronic organ systems).
>At the time, they needed a rack of about 8 computers to build an organ
>playback system. I suspect that after selling two or three systems, they
>went out of business or changed their business. But it was an
>interesting concept from back in the day when samples were something you
>used to make beats, before they were called beats.


Well, intermodulation is a distortion problem, but beats are linear -
just superposition. And no tone is actually generated at the beat
frequency.

And of course if the original high tones have already generated
audible tones by way of intermod, then you only need the audible
spectrum recorded to reproduce them. It may be that the interaction
happens later - the ear is the only place that can happen as air is
not non-linear at these levels. But the interaction will depend on
absolute volume levels, and accurate re-creation is very unlikely.

d
  #16  
Old February 10th 19, 12:40 AM posted to rec.audio.pro
nickbatz
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Posts: 97
Default Oversampling converters vs. high SRs

Don, that's what I was going to say - that IM (not even distortion, just natural eigentones - like the ones Mike R is talking about) have to be in the audible spectrum to be of any consequence.

Mike, was it Notre Dame de Budapest? That's an amazing sampled pipe organ from the old GigaSampler days. But what they call sampling every pipe individually is what you or I would call sampling every note individually - which is how all sample libraries are recorded, unless they're pitch-shifted, and that's before you get to all the different dynamic levels and articulations.

Anyway... my original question is less about the value of high sample rates (that's an old debate) than about the difference between oversampling converters and high SRs.

But then Scott says they're all sigma-delta converters nowadays - which I guess are 1-bit? - leaving me even more confused than I thought I was.

So let me try again: since the 1-bit signal isn't what's recorded, but instead it's what my brain tells me is super-oversampling, how is that different from converting high sample rates?

I guess the latency goes down at HSRs...
  #17  
Old February 10th 19, 01:27 AM posted to rec.audio.pro
Mike Rivers[_2_]
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Posts: 1,982
Default Oversampling converters vs. high SRs

On 2/9/2019 6:40 PM, nickbatz wrote:
> Mike, was it Notre Dame de Budapest? That's an amazing sampled pipe organ from the old GigaSampler days.


I don't know which organ they used, but it wasn't Gigasampler. The
company name was three letters. I could probably find it if I looked
through all of my old NAMM show reports.

--
For a good time, call http://mikeriversaudio.wordpress.com
  #18  
Old February 10th 19, 03:56 AM posted to rec.audio.pro
Les Cargill[_4_]
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Posts: 1,354
Default Oversampling converters vs. high SRs

nickbatz wrote:
> Don, if you read my last post in response to Scott, you'll probably
> understand my lack of understanding.
>
> I don't really know how else to phrase the question: what is the
> argument for storing audio files post-converter at anything over
> 44.1/48 if the filtering is being done way above the audible spectrum
> anyway?
>


Some plugins work better at higher SR. Higher SR may make lower round
trip latency possible. It may emerge that for significant recordings,
future generations will find a use for the additional bandwidth.

The last bit seems unlikely but you never know.

--
Les Cargill
 




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