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Using all that CD has to offer?, What types of music and specific discs use the full bits and freq.
dhromed
post Jun 9 2012, 12:30
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QUOTE (BearcatSandor @ Jun 9 2012, 00:19) *
I have read (somewhere a long time ago) that the reason 44.1 was picked was because that gave you a frequency range of 44.1/2 on either side of the middle.


What middle? There is no middle for frequency, and I'm not sure where you got the 18.xHz value. I think you may be confusing dynamic range* with frequency bandwidth**.

*) the vertical component of a sine wave, a.k.a. the volume or intensity, which has a middle. If expressed as a signed integer, then, due to the peculiarities of numbers stored in bits, you have half the possible values above the middle, and half below.

**) The horizontal component of a sine wave. The lower frequency bound is the length of the signal (you can't put a big wave into a small space), and the upper one by the sample rate: you need a sample rate at least 2f if you wish to capture a maximum sound frequency of f. 20KHz max for human perception, plus some headroom, times two, results in a 44.1KHz sample rate.
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greynol
post Jun 9 2012, 16:45
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I assumed it was a typo and thought he was talking (albeit awkwardly) about Nyquist with everything higher in frequency than the middle (22.05 kHz) being the portion that causes imaging/aliaing problems when not filtered properly. I found the following graphic to hopefully illustrate this. I would replace the word harmonics in the legend with periodic images or replicas, as harmonics was not a good choice, IMO. Also, the horizontal axis extends but the images don't keep repeating. This is wrong and potentially misleading.



Anyhow, upon reading again I finally now see that he really did mean 18.1 Hz and not 18100 Hz.

Reproducing low frequencies is not and never was a problem with digital. CDs can very easily store information for the reproduction of a DC signal, all the way in amplitude to full scale on either side of zero (-∞ dB).

I guess I'm used to people arguing over the high frequencies. Now I'm the one looking at the wrong end. laugh.gif

This post has been edited by greynol: Jun 9 2012, 22:26


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BearcatSandor
post Jun 9 2012, 22:16
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Ah, i see where i screwed up. Thanks folks. Greynol, that graph helped. I was misunderstanding what the 44.1k portion of "16/44.1k" meant. I was looking at it as thought it was a frequency range with a bottom and upper limit (which would be split in half like a signed data type)



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greynol
post Jun 9 2012, 22:35
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44.1kHz is how many samples there are in a second. It dictates how much frequency can be generated with the upper bound being half the sample rate. If you digitize an analog signal but fail to filter frequencies beyond fs/2 (the point where the blue and green curves intersect), they will be folded backwards into the bandwidth that can be generated as shown in the graph. This is known as aliasing.

In case it still isn't completely obvious, we desire the right half of the blue shape to be preserved (or at least the audible part of it) without introducing aliasing. In order to accomplish this you need to filter frequencies beyond fs/2.

You may want to go over my previous post, I made an edit to mention the graph's error in failing to show that the green replicas actually repeat along with the extending horizontal axis in both directions.

This post has been edited by greynol: Jun 9 2012, 23:51


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stephan_g
post Jun 10 2012, 13:28
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QUOTE (BearcatSandor @ Jun 9 2012, 22:16) *
I was looking at it as thought it was a frequency range with a bottom and upper limit (which would be split in half like a signed data type)

In a way, it is... except it extends from -fs/2 to +fs/2.
I've tried to come up with a (hopefully) halfway layman-compatible introduction here.
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mzil
post Jun 10 2012, 20:43
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QUOTE (greynol @ Jun 9 2012, 17:35) *
44.1kHz is how many samples there are in a second. It dictates how much frequency can be generated with the upper bound being half the sample rate...


That part I've heard before and accept, but can anyone tell me the specifics of why that very particular sampling rate was chosen? Why not just use 44.0 kHz, for example? Who decided the upper limit needed was 22.05 kHz, exactly? Why not just 20 kHz?

Who decided this? Denon?

What's the top frequency of CD anyway? Am I correct CD's are incapable of 22.05 kHz, they can only do 22.0499999999...? Thanks.[My questions are to all]
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db1989
post Jun 10 2012, 20:58
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QUOTE (mzil @ Jun 10 2012, 20:43) *
[] can anyone tell me the specifics of why that very particular sampling rate was chosen? Why not just use 44.0 kHz, for example? Who decided the upper limit needed was 22.05 kHz, exactly? Why not just 20 kHz?

Who decided this? Denon?
Compatibility with existing broadcast formats, mainly: http://en.wikipedia.org/wiki/44,100_Hz#Why_44.1_kHz.3F

QUOTE
What's the top frequency of CD anyway? Am I correct CD's are incapable of 22.05 kHz, they can only do 22.0499999999...? Thanks.[My questions are to all]
Yes, any sampling rate n can represent (unambiguously) frequencies only <0.5n. Not ≤0.5n, which is a common misunderstanding.
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mzil
post Jun 10 2012, 21:28
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So our CD audio sampling rate could have been 40.5, 41.4, 42.3, 43.2, 44.1, 45, 45.9, or 46.8 kHz, for compatibility with both the NTSC and PAL VTRs they were using to record the signal at the time, and to stay away from the need for sharper filters on the low end and not to intrude on the vertical blanking interval on the high end, 44.1, right in the middle, was chosen. Good to know, thanks.

[Although that wiki article implies it was Sony's "defacto selection", whereas it was actually Denon in conjunction with the NHK which started the use of 44.1, (14 bit though), if I understand correctly, also recording on VTRs, in 1970 or so.]

This post has been edited by mzil: Jun 10 2012, 21:34
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greynol
post Jun 10 2012, 21:55
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Actually there is no reason why a CD can't produce a 22.05kHz tone, as it can be represented in 44.1kHz PCM at any amplitude that the bit depth will support.

Sampling a 22.05kHz tone and getting the amplitude correct is another matter entirely.


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lvqcl
post Jun 10 2012, 22:01
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QUOTE (greynol @ Jun 11 2012, 00:55) *
it can be represented in 44.1kHz PCM at any amplitude

But not at any phase wink.gif
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greynol
post Jun 10 2012, 22:11
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Of course not! smile.gif


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DVDdoug
post Jun 12 2012, 20:54
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QUOTE
This got me wondering what styles of music generally do use the full bandwidth and bit-width available on CDs?
When CDs were introduced, I predicted that (popular) music would evolve and become more dynamic, taking advantage of the format... Boy, was I WRONG! Instead, we got rap. biggrin.gif Then hyper-compression and the loudness war.

It's ironic that the most dynamic music is (generally) the oldest... Classical.

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Porcus
post Jun 12 2012, 21:20
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Well CD can give you some very impressively silent fade-outs wink.gif


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greynol
post Jun 12 2012, 21:53
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...and reverb tails. Better still with high-rez! cool.gif


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Arnold B. Kruege...
post Jun 13 2012, 12:43
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QUOTE (greynol @ Jun 12 2012, 16:53) *
...and reverb tails. Better still with high-rez! cool.gif


Really?

I've yet to find a so-called hi-rez recording with enough dynamic range to give 16 bits a problem. The last one that a hi-rez advocate tipped me off to had a noise floor that was no more than 70 dB below FS.
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greynol
post Jun 13 2012, 13:16
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Oh FFS, I was continuing with the joke; but seriously, you can't possibly find it inconceivable that one could end a track with a digitally-generated reverb tail which could make use of the increased bit depth causing an audible difference when amplified by an unreasonable amount for normal playback?

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stephan_g
post Jun 13 2012, 13:40
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Back in the olden days this kind of signal actually was quite popular for evaluating low-level DAC nonlinearity. The results would be quite boring with a properly dithered signal on a modern-day DAC though.

QUOTE (DVDdoug @ Jun 12 2012, 20:54) *
When CDs were introduced, I predicted that (popular) music would evolve and become more dynamic, taking advantage of the format... Boy, was I WRONG!

Well, people did take advantage of it, sometimes, for a few years. Productions up to about 1985 tend to be pretty good IME (after when it slowly got more and more spotty until the mid-'90s). One of the most dynamic pop albums I know (and with well-used dynamics at that) is Peter Gabriel's 4th ("Security") from 1982.

Then the CD went mainstream and productions started to cater to mainstream (read: modest) reproduction equipment. And the rest is history...
QUOTE (DVDdoug @ Jun 12 2012, 20:54) *
It's ironic that the most dynamic music is (generally) the oldest... Classical.

What's more, it used to be a driving force in the evolution of recording and reproduction technology because of that. I think it's quite difficult to "get" large-scale orchestra works without having playback equipment that does them justice. (Which, with the kind of headphones available today, is not as expensive as it used to be, but some dedication is still required.)

Funnily enough, I can pretty much listen to classical indefinitely, while some hyper-compressed modern-day music will give me a headache in no time (fortunately, most of it remains more or less listenable). Which makes me think that there is a limit beyond which the lack of dynamics is perceived as unnatural and hence irritating.

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pdq
post Jun 13 2012, 13:57
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"Nights in White Satin" was an experiment to apply to popular music the technology that had been developed for classical music. Who knew that the CD will end up killing what started out with such great promise. sad.gif

I haven't listened for it on the CD version, but on the LP version of "A Day in the Life", if you turn the volume up really high as the final piano chord is fading away, you can hear the squeek of the piano bench. smile.gif

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Nessuno
post Jun 13 2012, 14:46
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QUOTE (pdq @ Jun 13 2012, 14:57) *
I haven't listened for it on the CD version, but on the LP version of "A Day in the Life", if you turn the volume up really high as the final piano chord is fading away, you can hear the squeek of the piano bench. smile.gif


Yessss: I remember it was faintly audible even on the cassette tape recorded from the CD I first had Sgt. Pepper on, some twenty years ago... smile.gif


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krabapple
post Jun 13 2012, 15:52
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QUOTE (stephan_g @ Jun 13 2012, 08:40) *
One of the most dynamic pop albums I know (and with well-used dynamics at that) is Peter Gabriel's 4th ("Security") from 1982.


...whose dynamic range was reduced on the remaster (as I'm sure will not surprise you)
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Arnold B. Kruege...
post Jun 13 2012, 16:14
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QUOTE (greynol @ Jun 13 2012, 08:16) *
Oh FFS, I was continuing with the joke; but seriously, you can't possibly find it inconceivable that one could end a track with a digitally-generated reverb tail which could make use of the increased bit depth causing an audible difference when amplified by an unreasonable amount for normal playback?


You don't have to generate a thing - just do a really long fade out, and it will make the naturally-occurring reverb tail look like its setting new records for dynamic range.
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Arnold B. Kruege...
post Jun 13 2012, 16:55
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QUOTE (stephan_g @ Jun 13 2012, 08:40) *
Back in the olden days this kind of signal actually was quite popular for evaluating low-level DAC nonlinearity. The results would be quite boring with a properly dithered signal on a modern-day DAC though.

QUOTE (DVDdoug @ Jun 12 2012, 20:54) *
When CDs were introduced, I predicted that (popular) music would evolve and become more dynamic, taking advantage of the format... Boy, was I WRONG!

Well, people did take advantage of it, sometimes, for a few years. Productions up to about 1985 tend to be pretty good IME (after when it slowly got more and more spotty until the mid-'90s). One of the most dynamic pop albums I know (and with well-used dynamics at that) is Peter Gabriel's 4th ("Security") from 1982.


The eponymous album by Rickie Lee Jones (recorded and released in the late 1970s) was the all-time dynamic range champ in my investigations until just lately, with real live passages (not fade ins or fade outs) that were recorded about 70 dB below FS. Engineer? The late, great Roger Nichols.
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mzil
post Jun 13 2012, 17:32
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QUOTE (krabapple @ Jun 13 2012, 10:52) *
QUOTE (stephan_g @ Jun 13 2012, 08:40) *
One of the most dynamic pop albums I know (and with well-used dynamics at that) is Peter Gabriel's 4th ("Security") from 1982.


...whose dynamic range was reduced on the remaster (as I'm sure will not surprise you)

I remember that album was the first DDD (SPARS code) release of music I was actually interested in, so I bought it (and was very impressed). Thank goodness I bought it then.

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Stone Free
post Jun 14 2012, 16:29
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QUOTE (Arnold B. Krueger @ Jun 13 2012, 16:55) *
The eponymous album by Rickie Lee Jones (recorded and released in the late 1970s) was the all-time dynamic range champ in my investigations until just lately, with real live passages (not fade ins or fade outs) that were recorded about 70 dB below FS. Engineer? The late, great Roger Nichols.
So is this 1984 copy the one to get? http://www.amazon.co.uk/Rickie-Lee-Jones/d..._pr_product_top

I loved "Ugly Man" from "The Evening of My Best Day" which I got on one of my "Total Guitar" CDs, here in the UK.

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stephan_g
post Jun 14 2012, 21:04
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I bought this one new a few years ago, and it seems they are still selling the same 1983 CD issue. (Same, btw, for Alphaville's Forever Young from '84, another one that needs a remaster job about as much as a hole in the ... err ... reflecting layer.) At least my CD posts the same results as found in the DR Database, i.e. DR15. Sounds quite nice, if a touch bland maybe (showing its age). I might be more fond of it if I could make out what she's singing more consistently.

Looking at the tracks in Audacity, I can't find any passages remotely close to -70 dBFS though... -50 dBFS is about it.

I actually have both CD issues of Peter Gabriel #4. The remastered version has a far more informative booklet, and some might prefer its somewhat different sonic balance - but ultimately there was little to gain from a digitally mixed master, and some dynamic range to lose at the top. The loudest drum hits at the very end of The rhythm of the heat come out audibly clipped. That, IMO, is not acceptable.

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