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16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain



 
 
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  #101  
Old November 20th 03, 01:05 PM
Garthrr
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article >, Jay -
atldigi > writes:

>The transfer function really does become linear with dither, at the
>expense of a noise floor.


Ok, there's another important piece of the puzzle (at least for me).
So if I understand correctly, its a situation where what would seem to be ideal
on paper is problematic as far as implementation because of the side effects of
distortion and aliasing. So dither cures these problems at the expense of the
noise floor by somehow either correcting the quantization error or rendering it
harmless. So what would be stairstep errors in voltage are smoothed over by
dither and thus the resolution of the system in the higher levels becomes, for
all practical purposes, perfect. Is that an essentially correct
oversimplification?

Garth~


"I think the fact that music can come up a wire is a miracle."
Ed Cherney
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  #102  
Old November 20th 03, 01:05 PM
Garthrr
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article > , Justin Ulysses
Morse > writes:

>I thought it was about the 4th or 5th time I said it in these threads
>over the past 2 days, and I thought I was repeating myself. But I'm
>glad to hear it's starting to gel.


You may well have said it and I could have either missed the post or missed the
point. Either way it is starting to make sense to me even though its still a
little blurry.

<<Suppose you have an input signal whose voltage at some arbitrary point
in time is 3.26534263219541623 volts. Now, off the top of my head I
estimate that the best approximation of this voltage you can represent
with 24 bits is maybe 3.2653426 volts. And 16 bits would round it off
to around 3.26534. So what's going on in the 24-bit audio that's
missing from the 16-bit audio? A signal in the neighborhood of 2.6
microvolts. Which is pretty dang low-level if you ask me. >>

Here is a bblluurrrryy moment for me. Is it that there is a _signal_ which is
2.6 microvolts or... is it that there is an error of 2.6 microvolts in the
reproduction of a signal which is the above 3.26534263219541623 volts? To me
this seems like a qualitative difference (no matter how insignificant the
quantity in question may be).

I think its difficult for someone who knows a lot about a thing to explain it
to someone who knows nothing about it because the one who knows is apt to
assume certain understandings on the part of the one who doesnt.

Garth~


"I think the fact that music can come up a wire is a miracle."
Ed Cherney
  #103  
Old November 20th 03, 01:29 PM
Garthrr
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article >, "Arny Krueger"
> writes:

>
>The information that falls between the pairs of 16 bit values is obviously
>very small, so I guess its fair to call it "low level information".


Oh I never thought about it in that way. I took "low level" to mean low dB
level as in -100dB or something of that sort. I guess instead it was meant as
"insignificant".

Garth~


"I think the fact that music can come up a wire is a miracle."
Ed Cherney
  #104  
Old November 20th 03, 01:29 PM
Garthrr
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article >, Jay -
atldigi > writes:

>what you see on paper with an ideal quantizer is not what you see in
>actual practice with digital audio's intentionally non-ideal quantizers.


I think this is really important for anyone who is struggling to get this stuff
as I am. Until this morning I was not aware of this although it doesnt surprise
me.

Garth~


"I think the fact that music can come up a wire is a miracle."
Ed Cherney
  #105  
Old November 20th 03, 01:29 PM
Garthrr
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article >, Jay -
atldigi > writes:

> There are probably a few other helpful things that
>you may have missed or that didn't quite make sense the first time
>through.


Good lord! You have a singular gift for understatement!

Garth~


"I think the fact that music can come up a wire is a miracle."
Ed Cherney
  #106  
Old November 20th 03, 01:29 PM
Garthrr
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

In article >, "Arny Krueger"
> writes:

>"Garthrr" > wrote in message

>
>> In article > , Carey
>> Carlan > writes:

>
>>> The other bits provide 256 more possible levels between each of the
>>> 16- bits' levels.

>
>>> Do you disagree with any of the above? It's just math.


GW
>> This the question I keep trying to get an answer to but after trying
>> a number of times over several years I have not gotten one. Its like
>> the question just bounces right off.


AK
>It's doesn't bounce off everybody. I for one strongly affirm what Carey said
>above. The relevant facts are very compelling to me. It's simply how things
>work.


I guess what I'm trying to find out is whether others do not agree with what
Carey said--whether this is in contention or not.
From something I just read I'm beginning to think that dither is somehow
responsible for negating the advantage of that extra resolution at least in
higher level signals.

Garth~



"I think the fact that music can come up a wire is a miracle."
Ed Cherney
  #107  
Old November 20th 03, 02:39 PM
Arny Krueger
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Roger W. Norman" > wrote in message

> "Kurt Albershardt" > wrote in message
> ...
>> Also: due to the way computers store information, 18 bit PCM takes
>> the same amount of disk space as does 24 bit PCM (and often the same
>> amount as does 32 bit floating point PCM data.)
>>

>
> Well, my point wasn't that using 24 bit has anything wrong with it,
> nor, with the cost of storage today, is there a problem with using 24
> bit for any project. In fact, the processing aspects of digital
> certainly require that you use 24 bit, and save it as 32 bit floating
> point if you can. I was just trying to make it clear that there are
> technical aspects of 24 bit converters that wouldn't necessarily make
> them better than 16 bit in given circumstances. Pretty much the
> concept of choosing one's tools to fit the job.


Agreed. One thing to realize is that most if not all of the major chip
makers have unflinchingly released 24/96 and 24/192 converters with worse
measured dynamic range than some of their earlier 16/44 converters. There's
a part of the market that is all about numbers.

> When I go out and do
> location recordings, I still use Tascam DA38s and I've not had one
> client that wasn't happy with the recordings. They might not have
> liked the performances, but that's a different story. My last
> submission to A Fifth of RAP was recorded onto DA38, and it sounds
> pretty good to me (obviously biased) with plenty of dynamics. The
> room lacked something and 24 bits wouldn't necessarily have bought me
> anything more. The same with Scott Dorsey's extremely dynamic
> recording. And again, Tonebarge absolute knocks one out of the park
> with his Mackie/Adat combination (although he uses different pres for
> tracking).


> I just didn't want any lurkers to think that only 24 bit converters
> are a solution to any recording problems they might have. Again,
> it's the use of the tools rather than the tools themselves.


I think that this is one of the most important messages that a group like
this has to present to newbies.



  #108  
Old November 20th 03, 02:48 PM
Arny Krueger
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Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Garthrr" > wrote in message

> In article >, "Arny Krueger"
> > writes:
>
>> "Garthrr" > wrote in message
>>
>>
>>> In article > , Carey
>>> Carlan > writes:


>>>> The other bits provide 256 more possible levels between each of the
>>>> 16- bits' levels.


>>>> Do you disagree with any of the above? It's just math.

>
> GW
>>> This the question I keep trying to get an answer to but after trying
>>> a number of times over several years I have not gotten one. Its like
>>> the question just bounces right off.


> AK
>> It's doesn't bounce off everybody. I for one strongly affirm what
>> Carey said above. The relevant facts are very compelling to me. It's
>> simply how things work.


> I guess what I'm trying to find out is whether others do not agree
> with what Carey said--whether this is in contention or not.


On Usenet, *anything* can be in contention! ;-)

> From something I just read I'm beginning to think that dither is
> somehow responsible for negating the advantage of that extra
> resolution at least in higher level signals.


Not if dither is used correctly, and these days it often is used correctly.

Usually, dither is sized to match the actual size of the smallest
quantization step. This number has to be chosen carefully because the
smallest step being quantized by just about all 24-bit converters isn't the
theoretical 1 sixteen-millionth of full scale. It's something vastly bigger,
and it varies quit a bit from converter to converter. But the education
process has worked and most chip designers know about this.

Dither makes the size of the quantization steps much more sonically
palatable, no matter how big or small they are.

From the standpoint of technical accuracy, dither doesn't negate any
advantages, and it doesn't level any playing fields.

These days, *everybody* uses dither in their quantizers, and IME *everybody*
makes pretty good use of it. However a converter with a relatively coarse
step size is still going to be noisier than one that has a smaller step
size.



  #109  
Old November 20th 03, 02:54 PM
Arny Krueger
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Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Garthrr" > wrote in message

> In article > , Justin
> Ulysses Morse > writes:
>
>> I thought it was about the 4th or 5th time I said it in these threads
>> over the past 2 days, and I thought I was repeating myself. But I'm
>> glad to hear it's starting to gel.

>
> You may well have said it and I could have either missed the post or
> missed the point. Either way it is starting to make sense to me even
> though its still a little blurry.


> <<Suppose you have an input signal whose voltage at some arbitrary
> point in time is 3.26534263219541623 volts. Now, off the top of my
> head I estimate that the best approximation of this voltage you can
> represent with 24 bits is maybe 3.2653426 volts. And 16 bits would
> round it off to around 3.26534. So what's going on in the 24-bit
> audio that's missing from the 16-bit audio? A signal in the
> neighborhood of 2.6 microvolts. Which is pretty dang low-level if
> you ask me. >>


> Here is a bblluurrrryy moment for me. Is it that there is a _signal_
> which is > 2.6 microvolts or... is it that there is an error of 2.6

microvolts
> in the reproduction of a signal which is the above
> 3.26534263219541623 volts?


Both. You can think of 3.26534 volts as 3.26534263219541623 volts with an
approximately 2.6 microvolt error, or you can think of .26534 volts as a
3.26534263219541623 volt signal with an approximately 2.6 microvolt error
voltage added.

> To me this seems like a qualitative
> difference (no matter how insignificant the quantity in question may
> be).


It is a small qualitative difference. It's an error that is about 120 dB
down in the presence of a signal which is close to full scale (0 dB), which
means don't worry about it. If the size of a significant signal was -100 dB,
then it would be worth worrying about.




  #110  
Old November 20th 03, 03:03 PM
Arny Krueger
external usenet poster
 
Posts: n/a
Default 16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain

"Garthrr" > wrote in message

> In article >,
> Jay - atldigi > writes:
>
>> The transfer function really does become linear with dither, at the
>> expense of a noise floor.

>
> Ok, there's another important piece of the puzzle (at least for me).
> So if I understand correctly, its a situation where what would seem
> to be ideal on paper is problematic as far as implementation because
> of the side effects of distortion and aliasing. So dither cures these
> problems at the expense of the noise floor by somehow either
> correcting the quantization error or rendering it harmless.


Dither clearly doesn't correct quantization error. Dither does change
quantization error into something that is sonically more benign. What dither
does is sort of like turning sewage into beer. The sewage hasn't been
exactly been turned into chemically pure water. But, the sewage has been
turned into beer, which is something that is more palatable to most of us
than sewage.

>So what
> would be stairstep errors in voltage are smoothed over by dither and
> thus the resolution of the system in the higher levels becomes, for
> all practical purposes, perfect. Is that an essentially correct
> oversimplification?


The stairstep errors don't get smoothed, they become randomized. Think of
quantization errors as being splats of paint on the wall. Without dither the
splats of paint would tend to be grouped, so they would look like bigger
messier splats.

Dither makes the splats more uniformly distributed so they appear to be
smaller and actually more like some nicely shaded, more neutral color.

BTW, dithering pretty much works this way when it's applied to computer
graphics.



 




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