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Redbook CD: What would specs be if it were invented today?
Old 21st January 2013
  #1
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Redbook CD: What would specs be if it were invented today?

Redbook CD standards specify a 5.25" disc carrying up to 79 minutes of audio with a frequency response from 20Hz up to 20kHz, 16bit resolution, bandwidth of 44.1kHz.

Given today's technology, or a more advanced technology in 1979, what would CD have looked like?
Old 21st January 2013
  #2
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A Blu-Ray disc with FLAC-compressed audio, samples rates up to 192 kHz and arbitrary channel count. Standard configuration would be 20 bit / 60 kHz stereo, higher channel counts should also include a stereo stream.
Old 22nd January 2013
  #3
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1" disk, AC3 audio @ 256kbps, 40KHz sample rate, 7.1-channel, holds up to 20 hours of audio, so full of copy protection, it's unplayable even in compliant players.
Old 22nd January 2013
  #4
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IDK. Get a stratch on a CD and it skips but get the same stratch on a more densely packed disc and it will skip longer.

USB sticks would be fine with me.
Old 22nd January 2013
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Assuming DVDs were already invented; people would be wondering what's the point bringing out another optical disc for audio when, I can download music off the net and store it on memory sticks or hard drive.

My guess is, it will be more flexible than the red book standards.
You can record a 16 or 24 bit file, at either 44.1KHz, 48KHz, 96KHz, & 192KHz and the CD player will adjust itself to playback at different frequencies.
The way I see it; if CD's came out today, music downloads will kill off sales.
Old 22nd January 2013
  #6
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The reason I ask this question is because (1): I seem to get the impression that back when CD was new a lot of people, and not just audiophiles, seemed to have the same reaction to them when compared to LPs as many folks have today regarding MP3 when compared to CD! lol

(2): I'm also picking up that for those whose hearing is in better shape than mine, the redbook standards were just barely adequate to resolve complex passages.

Should Sony, Philips, et al have allowed for a 22kHz top limit as opposed to 20kHz? Should the bottom have been lowered to 15Hz? Was 16bit EVER enough resolution(even though an improvement over the original spec 14bit?).

Would the CD have to have been "not so" compact(may be 6" in diameter) by late '70s standards of digital development, to accommodate these changes?

Interesting, in retrospect.
Old 23rd January 2013
  #7
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1: From what I can remember back in the 80's; the reason most people brought CD's was because they could play back the CD many times over and not hear any deterioration in sound quality plus, you could operate a CD player with a remote control to change tracks. With a turntable, you have to get up out your seat, lift the arm and lower the arm to play specific track.

2: The 44.1KHz sampling frequency was used so digital recordings could easily be stored on European & US video formats of the era. Here's a link that explains it in more detail. http://www.cs.columbia.edu/~hgs/audio/44.1.html

The red book states 20Hz as a lower limit but digital players can be designed to go down to 0Hz if the designer chooses.
Old 23rd January 2013
  #8
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There's a lot of reasons why the CD is the way it is. My understanding is most people thought of it favorably at least on the surface, as mine was. Then, the more people listened to it, the more they felt something was wrong with it. Bandwidth isn't the issue. Jitter, non-linearities of the converters and anti-aliasing filters were the issue. To go from no attenuation to 96dB attenuation between 20KHz and 22KHz is not an easy thing to do. Early pro digital machines recorded at 50KHz and used 10-pole filters, set at 18KHz, which would give you -96dB at 30KHz, meaning aliasing could be heard down to 14KHz and about a 90 degree phase shift as low as 3KHz. Sony was interested in primarily one thing, bringing CDs to the public, which meant low price. In order to do that, it had to be mastered on U-Matic video tape, which was common and relatively inexpensive as far as pro video recorders were concerned. The highest sample rate they could safely support was 44.055KHz or something like that in the U.S. and 44.1KHz in Europe. Extending the bandwidth of the CD to 22Khz would allow alias distortion in the 10Khz range. Part of the "low cost" criterion forced most manufacturers to use 8-pole filters, which would allow aliasing at even lower frequencies.
Quantization error; the most basic direct, linear, 16-bit ADC requires 17 resistors, 16 comparators and the associated hardware to turn the parallel data into serial data. The first resistor/comparator pair accounts for half of the total signal voltage and each subsequent resistor/comparator accounts for half the value of the one previous pair. Now, most electronics guys will tell you that a 1% tolerance in a resistor is difficult to obtain. Even if you had a .001% tolerance, the margin of error in the most significant bit (the first resistor/comparator pair) will be far greater than several of the least significant bits.
Jitter is not really something that was well known even to the engineers that designed early digital systems. I don't know of anybody that has tested the jitter on a PCM 1600 mastering processor, but I'm sure it's way higher than my old 24-bit M-Audio cards that perform at about a 17-bit level, largely due to jitter.
Also, early digital to analogue converters had all the same problems as the ADCs.
A lot of those problems were somewhat circumvented by #1, Delta-Sigma, oversampling converters. If you only use 1-bit dithered converters and sample at say 2.8MHz, you get around the issues of non-linearity in the quantization stage and can switch to 5-pole filters around 50Khz instead of 8-pole filters at 18KHz. Now, leave the signal at that, and you get DSD, which is the basis for SACD. Digitally filter and quantize down to 44.1KHz 16-bit and you get 20KHz audio with 90dB dynamic range with hardly any filtering in the audible range (80dB attenuation usually), no phase shift (at the cost of pre-ringing) and it costs a lot less than the old system. #2, clocking has gotten a lot better, especially where the PLLs that sync the converters to the clocks have gotten a lot better and jitter is almost negligible now, so 24-bit converters can easily achieve 22-bit performance.

What I'm saying is, it was barely good enough in the early-mid 90s and only thanks to advantages in technology. 44.1KHz was stuck to us by Sony to fit a price point and it absolutely was NOT good enough even at that time it was invented. All the other manufacturers begged Sony to use at least 50Khz as the standard, but that would have required a $30,000 recording system instead of $3,000 or so. One thing Phillips suggested was using 14-bit converters and 50.4KHz sampling, which would be the same bandwidth, but Sony was stuck on 16-bit, even though the converters didn't perform up to the theoretical 16-bit capability. I think that works in our favor today, but for 1979, I think Phillips was right.

MP3 encoding/decoding has gotten better as well, but I recently revisited my old favorite CODEC from 10 years ago and the best of today isn't THAT much better. However, revisiting my old PCM processor showed sound akin to nails on chalkboard.
To the previous poster, the Soundstream 8-track digital recorder could record down to DC since it used servo-balanced inputs and outputs.
Old 23rd January 2013
  #9
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Quote:
Originally Posted by The_K_Man ➑️
Redbook CD standards specify a 5.25" disc
I don't think that size is right. It's closer to 4.75"
Old 23rd January 2013
  #10
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sure it wouldn't say "provide white noise up to -12dBFS and then add 4 bits of modulated noise"?

Oh - and aim for +6 dBFS.
Old 23rd January 2013
  #11
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The other part of the CD story is the Philips video disk that could be pressed in a vinyl plant. This allowed Sony and Philips to bring a digital disk to market years ahead of their competition.
Old 23rd January 2013 | Show parent
  #12
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Quote:
Originally Posted by Waltz Mastering ➑️
I don't think that size is right. It's closer to 4.75"
Youre right - slightly less than 4.75". I'm on the small side, so it feels more like 5+" in my hand!
Old 23rd January 2013
  #13
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Since this is a What If thread, rather than a historical one,

I'd vote for a Blu-Ray disc with full resolution PCM audio, up to 24-bit 192kHz.

With 2.0, 5.1, 7.1, etc. capability, Perhaps multiple streams like DVD-A.

program length determined by the format & disc capacity.

JT

And of course it already exists, but seems no one exploits it:

http://www.blu-raydisc.com/assets/Do...0423-17830.pdf

See page 18 for audio specs.
Old 23rd January 2013 | Show parent
  #14
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Quote:
Originally Posted by Jerry Tubb ➑️
I'd vote for a Blu-Ray disc with full resolution PCM audio, up to 24-bit 192kHz.

With 2.0, 5.1, 7.1, etc. capability, Perhaps multiple streams like DVD-A.

program length determined by the format & disc capacity.
Sounds like PureAudio BluRay. mShuttle is a nice extra feature to satisfy most listener's preferences since you can add FLAC or DSD.

All we now need is robust Hi-Res DDP. Currently preparing and receiving assets for authoring is not as easy as it should be. The entire process could be much more streamlined.

cheers,
Reynaud
Old 23rd January 2013 | Show parent
  #15
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Quote:
Originally Posted by Deleted User ➑️
Sounds like PureAudio BluRay. mShuttle is a nice extra feature to satisfy most listener's preferences since you can add FLAC or DSD.

All we now need is robust Hi-Res DDP. Currently preparing and receiving assets for authoring is not as easy as it should be. The entire process could be much more streamlined.

cheers,
Reynaud
Excellent link, thanks!

JT
Old 23rd January 2013 | Show parent
  #16
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Quote:
Originally Posted by Jerry Tubb ➑️
Since this is a What If thread, rather than a historical one,

I'd vote for a Blu-Ray disc with full resolution PCM audio, up to 24-bit 192kHz.

With 2.0, 5.1, 7.1, etc. capability, Perhaps multiple streams like DVD-A.

program length determined by the format & disc capacity.

JT

And of course it already exists, but seems no one exploits it:

http://www.blu-raydisc.com/assets/Do...0423-17830.pdf

See page 18 for audio specs.
Actually it's kinda both - historical and what-if.

If you could go back to the late 1970s what would you change about the spec -

The bit resolution(16) - First of all I do not have a CLUE as to what 16bit, 14bit, 24bit, or a two-bit suitcase all mean, but I'm just assuming that more bits SOUND better, so maybe increase that.

Secondly, people with hearing that didn't drop off above 14kHz(like mine!) had issue with 20kHz. Apparently they could either hear stuff into the mid-20s or were "subconsciously aware of" and "affected by" its presense - in analog, and turned off by its absence on CD.

But raising the top end apparently causes more noise in the teens, according to one of the replies on here.


Finally, 5.1, 7.1 surround sounds great, but that, and all of the above, would probably be dictated by the smallest pits & lands that could be burned by late-'70s technology.

Future replies to this thread must be from the perspective of the year 1978-79.

That might help guide what I'm looking to take back here.

Last edited by The_K_Man; 23rd January 2013 at 04:54 PM.. Reason: Committed a MAJOR Bush: replied within Mr. Tubb's reply!! smh
Old 23rd January 2013
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Yep, SACD, the hindsight (hindhearing) is 20/20 and woulda/coulda/shoulda, of optimally standardized for sonic superiority, mass marketed and distributed CD media digital formats.
Old 23rd January 2013 | Show parent
  #18
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Quote:
Originally Posted by string6theory ➑️
Yep, SACD, the hindsight (hindhearing) is 20/20 and woulda/coulda/shoulda, of optimally standardized for sonic superiority, mass marketed and distributed CD media digital formats.
The issue remains: Could the smaller pits & lands required for that have been doable with the contemporary technology - or would a not-so "compact" disc have been necessary?

On the other hand, if they were just in a hurry to sell "compact"ness to the public and make money - that would indeed be a shame!
Old 23rd January 2013
  #19
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Are we excluding any possible advent of Internet? If that's taken into account, it means no physical music format specs would never again be needed.
Old 23rd January 2013
  #20
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The reason for higher sample rates is keeping crap out of the audio well below 20kHz. when using real world gear as opposed to "perfect" imaginary gear.
Old 23rd January 2013 | Show parent
  #21
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Quote:
Originally Posted by The_K_Man ➑️
The issue remains: Could the smaller pits & lands required for that have been doable with the contemporary technology - or would a not-so "compact" disc have been necessary?

On the other hand, if they were just in a hurry to sell "compact"ness to the public and make money - that would indeed be a shame!

I don't know... just that CD's are "the pits" compared to SACD-land.
Old 24th January 2013 | Show parent
  #22
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Quote:
Originally Posted by The_K_Man ➑️
Actually it's kinda both - historical and what-if.

If you could go back to the late 1970s what would you change about the spec -

The bit resolution(16) - First of all I do not have a CLUE as to what 16bit, 14bit, 24bit, or a two-bit suitcase all mean, but I'm just assuming that more bits SOUND better, so maybe increase that.

Secondly, people with hearing that didn't drop off above 14kHz(like mine!) had issue with 20kHz. Apparently they could either hear stuff into the mid-20s or were "subconsciously aware of" and "affected by" its presense - in analog, and turned off by its absence on CD.

But raising the top end apparently causes more noise in the teens, according to one of the replies on here.


Finally, 5.1, 7.1 surround sounds great, but that, and all of the above, would probably be dictated by the smallest pits & lands that could be burned by late-'70s technology.

Future replies to this thread must be from the perspective of the year 1978-79.

That might help guide what I'm looking to take back here.
If you're talking about the late 70's, quadraphonic (4 channel format) was already dead so surround sound wouldn't have happened and I doubt it would have been possible to make Blu-ray discs and Blu-ray players cheap & reliable enough to be sold to the public.

1978-1979 digital audio I guess would have been at best, 13 bit & 50KHz sampling frequency or, not even digital.
It might have been analogue encoded on an FM carrier wave like VHS & Betamax video players.
Old 24th January 2013 | Show parent
  #23
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Quote:
Originally Posted by Hane ➑️
If you're talking about the late 70's, quadraphonic (4 channel format) was already dead so surround sound wouldn't have happened and I doubt it would have been possible to make Blu-ray discs and Blu-ray players cheap & reliable enough to be sold to the public.

1978-1979 digital audio I guess would have been at best, 13 bit & 50KHz sampling frequency or, not even digital.
It might have been analogue encoded on an FM carrier wave like VHS & Betamax video players.
LOL!

All kidding aside, if perhaps a couple extra $million were spent, what *minor* improvements could have been made to CD, given the tech of that time, to just push it over the top?
Old 24th January 2013 | Show parent
  #24
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Quote:
Originally Posted by The_K_Man ➑️
LOL!

All kidding aside, if perhaps a couple extra $million were spent, what *minor* improvements could have been made to CD, given the tech of that time, to just push it over the top?
Truly, 16 bits and 44.1kHz as a spec was more or less at the limit of the digital hardware at the time. Increasing it would not really have improved the sound. And isn't a couple of million kind of a drop in the ocean compared to the money spend? I don't know the figures but I'm fairly confident Philips would have gone under if CD had flopped, if not Sony as well!

CD audio is very well designed considering the limitations at the time. I think EFM is a marvellous technique because it's such a counterintuitive way of increasing the effective data density, but without it CDs would be significantly shorter.
Old 24th January 2013 | Show parent
  #25
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Quote:
Originally Posted by haberdasher ➑️
Truly, 16 bits and 44.1kHz as a spec was more or less at the limit of the digital hardware at the time. Increasing it would not really have improved the sound. And isn't a couple of million kind of a drop in the ocean compared to the money spend? I don't know the figures but I'm fairly confident Philips would have gone under if CD had flopped, if not Sony as well!

CD audio is very well designed considering the limitations at the time. I think EFM is a marvellous technique because it's such a counterintuitive way of increasing the effective data density, but without it CDs would be significantly shorter.
EFM?

Translate for 20th century ears.
Old 24th January 2013 | Show parent
  #26
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For starters, we'd need to go back to the 1930s to solve the problems with CD. Bell Labs conducted several experiments trying to find out what "good enough" was in order for people to accept an electronically transmitted signal as the same as an orchestra right in front of them. I don't remember the exact specs of the top of my head, but I think they stated that 30Hz-15KHz +-0.5dB, 80dB dynamic range, true 3-channel L/C/R to be the minimum. Any variations, like two channels, two channels matrixed through three speakers or three channels through two speakers etc. severely compromised stereo placement (the listeners had to draw where each sound source was, all equipment was behind a curtain). So using 2-channel stereo instead of 3-channel stereo was the first real compromise. Now, you can go crazy with a bunch of extra channels over people's heads etc. but IMO, the point of diminishing return for true surround sound is 7.2, with the subs by the SL and SR channels (not front or rear channels). 5.2 does quite well for most stuff and 3.2 for stereo (with subs by the L and R channels). We're talking CDs, though, so discrete 3-channel is ideal as LFE channels are not needed, just full range drivers. 2-channel stereo was forced upon the masses because the manufacturers didn't want to take the time and money to develop true 3-channel stereo.

On another note, Delta-Sigma modulation was first demonstrated in the 60s. Had Sony considered that instead of PCM, we probably would have avoided the anti-aliasing filters' issues entirely at the cost of lower dynamic range (at first).



Quote:
Originally Posted by Hane ➑️
If you're talking about the late 70's, quadraphonic (4 channel format) was already dead so surround sound wouldn't have happened and I doubt it would have been possible to make Blu-ray discs and Blu-ray players cheap & reliable enough to be sold to the public.
The problem there was that channel separation with the matrix quad systems was at best 4.5dB; almost mono. Who wants to pay double for something that's inferior to 2-channel stereo? It was yet another deal where they pushed to get a product to the masses before it was ready. Later, they came out with logic steering, but you really can't have anything happening in adjacent channels at a time. Dolby's notion of L/C/R/S makes more sense, but that's not standard quad anymore and still doesn't allow for full mixes.



Quote:
1978-1979 digital audio I guess would have been at best, 13 bit & 50KHz sampling frequency or, not even digital.
It might have been analogue encoded on an FM carrier wave like VHS & Betamax video players.
The best digital machines available off the shelf at the time was Mitsubishi's with 16-bit 50.4KHz. The worst machines at the time were 44.1KHz, 14-bit, but 3M's peculiar system was considered the most sonically neutral. It was 12-bit, 50KHz resolution with an extra 4-bit gain stage. So, it's 12-bit resolution, but 16-bit dynamic range because at lower levels, the gain stages would change to keep the signal quantization bits active. Philips's Videodisc, later known as Laserdisc, was the basis for the CD and it used a very good FM analogue carrier system, similar to VHS but without the obnoxious buzz that breathes with the dynamics of the material. The decision to go digital was a combination of insisting on a smaller size (going digital meant about half the area was needed) and Sony's vision of digital being the future.

Don't quote me on this, but I think THE first commercially viable digital multitrack tape recorder in 1972 used 13-bit 47.25kHz resolution. Really, Sony's 44.1K sampling was the worst that existed outside of prototyping experiments.
Old 24th January 2013
  #27
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Please, somebody - what does "EFM" stand for?
I'm really that sucko when it concerns abbreviations.
Old 24th January 2013 | Show parent
  #28
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Quote:
Originally Posted by The_K_Man ➑️
LOL!

All kidding aside, if perhaps a couple extra $million were spent, what *minor* improvements could have been made to CD, given the tech of that time, to just push it over the top?
I'm not kidding, even 16 bit convertors didn't exit in the late 70's.

It's not a case of companies deliberately holding back the technology to save money. I'm sure in the late 70's the designers had in mind more storage capacity, more channels, higher date rate but, It either wasn't possible to implement or there was no demand for it.
Old 24th January 2013 | Show parent
  #29
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Quote:
Originally Posted by Hane ➑️
I'm not kidding, even 16 bit convertors didn't exit in the late 70's.

It's not a case of companies deliberately holding back the technology to save money. I'm sure in the late 70's the designers had in mind more storage capacity, more channels, higher date rate but, It either wasn't possible to implement or there was no demand for it.
I don't know if you caught on but I did politely ask what "EFM" stood for and have yet to get an answer. I googled it but it stands for a dozen different things.
Old 24th January 2013
  #30
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Quote:
Originally Posted by The_K_Man ➑️
I don't know if you caught on but I did politely ask what "EFM" stood for and have yet to get an answer. I googled it but it stands for a dozen different things.
Hi K-man,

Try the below link.

(EFM = Eight-to-fourteen modulation)

http://en.m.wikipedia.org/wiki/Eight...een_modulation


Best,

Owen Gillett
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