Digtal vs Analog; Why Isn't Digital Better? (long)

[meuge]

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On 5/9/2005 1:59:26 PM D-MAN wrote:

Also it is patently untrue that there is no signal degredation between generations of digital copies, and NO you cannot make digital copies ad infinitum. That's why commercial cd's are PRESSED, not burned.

Also there are generational losses with digital, as well as the physical limitations of lasers. All DACs have error correcting circuits to account for that, and some are better than others.

DM

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Yes you can make digital copies ad infinitum. The error correction mechanisms applied by current operating systems are damn near perfect.

I conducted an experiment for someone who kept insisting that there is generational degradation of data on CDs. I used a collection of ebooks, about 300MB worth... all text files, burned at high speed to a cheap CD-R. I made 10 successive copies and used a verification program to monitor changes. At the 10th copy the data was bit-perfect-accurate and I decided that going further was unnecessary.

When proper checksum and error-correction processing is applied, any bidirectional digital data transmission is bit-perfect. There is no room for signal degradation, because you can't degrade a binary signal. Each bit is either on or off. If a "1" is (numbers only as examples) 1.0 on a reflective scale, and "0" is 1.5, it doesn't matter if the signal degrades a "1" to 0.9 or 1.1 - it's still going to be read as "1". The only type of degradation possible with a digital signal are true errors... and they are instantly detected because the checksum will no longer match the original. The same magnitude errors in an analog storage medium would cause collossal amounts of distortion.

This is the primary virtue of digital information storage -> as long as the media does not physically degrade, the data will not be affected. Plus, the ability to make PERFECT copies ensures the permanent integrity of the data.

The problem with CDs is that they do not include as much parity data as they probably should (in order to maximize available storage space)... which is why you can actually lose data, and create unresolvable errors. This says nothing about the idea of digitized music... it just points out imperfections in one type of storage media. The same information, stored in solid-state devices, would be impervious to such damage.

[DrWho]

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On 5/9/2005 2:17:07 PM psg wrote:

I'm pretty sure the 12kHz subharmonic would NOT be recorded because it doesn't exist without the 30kHz tone. If you were to plot the frequencies on a histogram, you wouldn't see anything at 12kHz or 48kHz.

Exactly. As I said earlier, it doesn't exist as souns at that frequency, but rather as amplitude changes of the other frequencies (beating, or modulation). It would be recorded because it's that recordable frequency that we hear going up and down.

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I had to think about this one for a while, lol.

The problem is that the process of removing the 30kHz tone (implementing an EQ) is also going to remove the amplitude changes incured upon the 18kHz tone. The whole 12kHz subharmonic is simply a product of the phase relationship between the two waves. Introducing an EQ is basically adding a third phase relationship that is going to cancel out the effects of the 30kHz tone (so now you're back to the original phase of the 18kHz tone, thus no 12kHz subharmonic).

[D-MAN]

As far as the error correction on a Meridian player handle a peice of dust, it is much the same as listening to a dust POP on vinyl. However, for the money, it has a great liquidity to its presentation - just like one would expect from the Brits, and THAT isn't on the digital recording, its in the DAC, etc...

Burning a copy of music is not the same as burning a copy of a computer program, etc. There are many aspects of music that are not used in the copying of computer data, computer information lacking the need for defining signal amplitude, channel divisions, etc. You will also note that there are different cd materials used as well as different reading/writing formats for this purpose. Music cds are different than data cds, but then if its all 1:1 why worry?

The point is anyone who buys into the propoganda that digital is a 1:1 perfect copy is totally mistaken. An error ratio is always present and a software algorythym is used to fill in the missing bits. It will never be 100%.

But it will be a mathematical approximation. Are we splitting hairs?

Let's go one further, is your cd player optimized for one format or the other, that is glass-pressed or burnt? There is a physical difference in the materials used in each. Is your laser more effective on one than the other? Only the correction software knows for sure.

The use of pressing a cd from a glass master (quite a bit like vinyl pressing) is indeed faster to manufacture, the medium is not light sensitive, and is therefore quite a bit more durable, especially temperature-wise. It can be assumed that there are less error corrections written to the commercial cd than a burnt copy.

DM

[sfogg]

DM,

"As far as the error correction on a Meridian player handle a peice of dust, it is much the same as listening to a dust POP on vinyl. "

Not even remotely. On the Meridian you will never hear any change in the music. On vinyl you get a POP that interrupts the music.

"There are many aspects of music that are not used in the copying of computer data, computer information lacking the need for defining signal amplitude, channel divisions, etc. "

What defines channel amplitude in the audio CD is *nothing* more then the audio data bits. Channel divisions are just a bit in the subcode of the frame to say if the current sample is for the left or right channel. It is all just data....

"Music cds are different than data cds, but then if its all 1:1 why worry?"

Because CD-Rs labeled 'For Music' also include a royalty payment to some companies. Firmware in stand alone CD burners is required to only write to 'Music' CD-Rs. Of course in many of them you could put a 'Music' CD-R in them to think it had one, then pull open the front draw and replace it with a normal data CD-R and it would work fine.

If you burn your CDs on a computer there is no need whatsoever for you to use 'Music' CD-Rs. Because it is just data you can use data or Music CD-Rs... whatever you heart desires.

The difference between the two is not technical, it was a royalty licensing thing.

"An error ratio is always present and a software algorythym is used to fill in the missing bits. It will never be 100%."

Wrong, error correction is 100% when it does its job.

" It can be assumed that there are less error corrections written to the commercial cd than a burnt copy."

You make an awful lot of assumptions. Of course anyone can use a verify program to verify that the burnt copy is bit for bit identical to the master. Many CD-R burning programs will do this for you if you want them too.

How exactly would you go about verifying the copy of your vinyl?

Shawn

[meuge]

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On 5/9/2005 3:35:24 PM D-MAN wrote:

The point is anyone who buys into the propoganda that digital is a 1:1 perfect copy is totally mistaken. An error ratio is always present and a software algorythym is used to fill in the missing bits. It will never be 100%.

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But you're WRONG!

If you copy the text of a book over and over again the letters in the text will not change. I just don't think you understand how digital data storage works. There is NO DIFFERENCE whether it's images, music, text, or anything else for that matter. It's just binary. And current copies are BIT-PERFECT.

There are no gradations in digital data. You can't have an "ALMOST 1" or "ALMOST 0". Talking about signal "degradation" in terms of digital data, is like saying that someone is "partially dead". You either read the data correctly or you don't. But when you don't read it correctly, the checksum will not match, and the same sector will be read again... until the checksum matches.

If you don't know what a checksum is, here's the simplest type of a checksum algorythm -> a simple summation.

Let's say you have 4 values you need to store digitally: 1, 2, 3, and 4.

While your CD-R is writing the data, and the information is still in the main memory, it will sum the values, which yields 10. It will then write the sum, immediately after the actual information.

When a CD-ROM reads the data, let's say it misreads it, and reads 1,2,2,4. Now as it's reading, it will perform the same summation as the source, but now the sum will be 9. The software will recognize that the sum doesn't match, which means there is an error. It will then redirect the drive to re-read the sector... until it gets 10 as a sum.

This is a simplistic version of what actually happens, but the gist of it is the same -> it's bit-perfect.

[DrWho]

I get the impression that a lot of people mistakingly picture the data on a CD being just like the data on an LP. Almost as if there's a little wave form running around in circles that if you magnify it, it looks like stair steps are making the wave form. And then you have a fancy laser that follows it or something...I dunno what people are thinking, but a lot of the discussion makes one wonder if they really know what's going on.

Might I suggest a few links:

http://electronics.howstuffworks.com/framed.htm?parent=cd.htm&url=http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/95x7.htm

http://electronics.howstuffworks.com/analog-digital.htm

http://electronics.howstuffworks.com/cd.htm

http://electronics.howstuffworks.com/bytes.htm

[D-MAN]

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On 5/9/2005 4:19:08 PM sfogg wrote:

DM,

"As far as the error correction on a Meridian player handle a peice of dust, it is much the same as listening to a dust POP on vinyl. "

Not even remotely. On the Meridian you will never hear any change in the music. On vinyl you get a POP that interrupts the music.

Shawn

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Thank you, Shawn - I own a Meridian cd player.

DM

[sfogg]

Which model?

Only the current units which use computer type CD/DVD-ROM drives (800 and 808 series) read memory into RAM at high speed and play it out of that. Their G series uses a CD type drive too but I'm not sure if it plays from RAM or not. From their literature it doesn't sound like it.

Their older units do not function that way. I have one of their older players too. When you hear a drop out like that on it it isn't from error concealment, it is from mistracking.

Shawn

[sunnysal]

meuge and shawn have done a nice job of clarifying the issues. in the end I suspect that LP lovers will not be swayed by science. I say use what you like...just listen! tony

[sfogg]

Tony,

"I say use what you like...just listen!"

I agree.

I was just pointing out some incorrect info posted about how digital works.

Shawn

[DizRotus]

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On

<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />

5/9/2005

4:30:33 PM

meuge wrote: <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

There is NO DIFFERENCE whether it's images, music, text, or anything else for that matter. It's just binary. And current copies are BIT-PERFECT.

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I understand the concept of binary and that the copy should be a bit-perfect duplication of the collection of 1s and 0s comprising the original.

Nevertheless, when a music CD is copied using a computer is that a bit-perfect copy of the data from the original?

Or, does the computers software perform some compression and/or processing of the data that result in a copy that might sound like the original but is not bit-perfect?

[Seadog]

Although this is an interesting topic, reading this thread is really making me tired!

I think I'll turn off the computer and pick out a good LP to listen to!

[sfogg]

The following pictures are a 1000hz sine wave recorded on CD at -20dB AND a 1000hz sine wave generated by my HP function generator. For the CD player I was just using my laptop and its sound card.

Same thing but with a shorter time base (zoomed in)....

More zoom....

Even more zoom....

Both traces overlaid on top of each other but not time aligned (out of phase) with each other....

Both traces overlad on top of each other but adjusted to be in phase (almost) with each other....

So which trace is the 'connect the dots' CD recording of a 1000hz sine wave vs. a sine wave from a function generator?

Shawn

[sfogg]

"Nevertheless, when a music CD is copied using a computer is that a bit-perfect copy of the data from the original? "

If you are using good extraction software you will have a bit-perfect extraction of the audio data on the original CD.

Shawn

[psg]

Thanks for doing that Shawn!

[psg]

Thanks for doing that Shawn!

[scriven]

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On 5/9/2005 9:08:44 PM DizRotus wrote:

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On

<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />

5/9/2005

4:30:33 PM

meuge wrote: <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

There is NO DIFFERENCE whether it's images, music, text, or anything else for that matter. It's just binary. And current copies are BIT-PERFECT.

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I understand the concept of binary and that the copy should be a bit-perfect duplication of the collection of 1s and 0s comprising the original.

Nevertheless, when a music CD is copied using a computer is that a bit-perfect copy of the data from the original?

Or, does the computer’s software perform some compression and/or processing of the data that result in a copy that might sound like the original but is not bit-perfect?

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When the computer reads a CD it will get an exact copy of what is on the CD. The only exception is when the CD is damaged and the drive cannot read it. On the extremely rare cases when that happens the software will tell you there is an error. It will never just "gloss over" or "fill in" an unreadable part. In fact, most programs will stop on the error and refuse to continue.

The only way the software will compress the data is if you tell it to store the copy in a compressed format. Store it as a wav file and you get every last bit! However, if you rip a CD and store it in MP3 format it will not be identical because MP3 is a compressed format. Even the lowest level of compression in MP3 will loose some information. The up side is that the file is smaller. The more you compress the more data alteration and the smaller the file. Even when storing the data in MP3 the program is starting with a perfect copy of the data.

[scriven]

Shawn,

You have the patients of a saint! And, you are dead on right.

[sunnysal]

-----------------------------333

[Mallette]

Dr Who...

Where can I get a copy of your book? While I've developed a vast amount of experiential opinion and methodology over the years, I also like to have some facts at hand. From what I see of your posts, you are in possession of them.

As a devoted user of Exact Audio Copy for years, I've arrived experientially at what I see being quoted here as having good factual foundation: an EAC extraction is as close to a file copy operation as you can get. I've run a number of blind A-B tests with "golden eared" audiophiles at my home and my playback of CD information from HDD through a Card Deluxe has equaled or exceeded any standalone player at any price. As the PC I built for my system is fanless and dead silent (ambient noise in my listening room is about -33db and you cannot tell it's been switched on except by the lights) and has the added convenience of random access to my 300 or so CD's, I've never purchased a standalone unit beyond your basic consumer grade for my wife and kids to use.

Also, I'd like your opinion of my statement earlier in this thread that CD/SACD/DVD-A or whatever will becoming moot issues with the advent and adoption of extremely high density storage media, such as the first gen of blu-ray, HDDVD, and such. I already have 4 channel 24/192 surround material (truly awesome to hear) on HDD and see no reason why the current stand alone players that already can read .wav and other non-mass consumer designed formats will not continue to evolve with the new high density formats...unless the RIAA or other interest groups find a way to block it.

As a "mom and pop" recording operation with a passion for pure acoustic music recorded as close to the old "direct to disc" methodology (I use no mixers or any process of any kind), the freedom to publish to my "niche" audiophile targets in a "pure" digital format is a great prospect.

Dave