[kidtexas]

Nope. Just did a copy in iTunes (from AIFF, not from MP3). I'd do it more thoroughly, but I really don't feel like burning CD's and stuff, and this was the only CD original/copy pair that I have on hand right now.

I'd be interested to see what other people get from device copies and such.

[Swiss Bob]

From http://www.cdpage.com:

"There are two basic types of data that reside on a compact disc: audio and visual data, which degrades gracefully; and text and computer data, which does not. Graceful degradation means that the data is not rendered inaccurate or unusable by uncorrected errors. A missing byte of information does not make much difference in audio or visual data. A one-bit error in text or computer information, however, could change a letter of text or crash a program."

[Developer]

Originally posted by Swiss Bob:
"There are two basic types of data that reside on a compact disc: audio and visual data, which degrades gracefully; and text and computer data, which does not."

I believe you are misinterpreting that sentence. You think it says

"Audio data degrades, computer data does not degrade."

To make sense though it must mean

"When data degrades, audio data does so gracefully, computer data does not gracefully."

Whether or not the original poster's copy contained "degraded" data or wheter the perceived difference was purely psychological, we will only know when he compares the checksums.

[Swiss Bob]

Originally posted by Developer:
Whether or not the original poster's copy contained "degraded" data or wheter the perceived difference was purely psychological, we will only know when he compares the checksums.

And therein lies the problem. We don't want the checksums at the desktop, we want them at the CD data stream.

Neither of us is going to win with this you know.

[kidtexas]

Originally posted by Swiss Bob:
And therein lies the problem. We don't want the checksums at the desktop, we want them at the CD data stream.

Neither of us is going to win with this you know.

Actually, as I interpret that statement, an error is an error, whether its in a text file or in audio. The difference is that an error in a text file will change your data, just like in audio, but that change will have a more obvious effect in the text file. The word "cat" might show up as the word "car".

In audio, there are enough data points (not to mention the error correction and the speed at which that data is coming at us) for us to ignore an error or two.

Witness the extreme over-compressing and volume boosting going on in music today. We've sucked out the dynamics completely, and now all thats left is to master our music up past digital "0", creating digital overs. However, a couple "overs" in a song is not necessarily perceptible, jsut like we don't see our monitors refresh 75 times a second.

[chabig]

Originally posted by The Godfather:
Could it be that all the ones and zeros are well copied, but the density of the indentations and lines is irregular in the copied CD? That would result in a skew in frequency and maybe noise in simple CD players.

No. "Indentations and lines" don't constitute data. All there is are ones and zeros. And the ones and zeros describe the waveform.

[Hornet]

Rightio all, I'm back with the results.

The test: I borrowed some jazz CD that my audiophile friend listens to (so that he will know what he will be hearing, rather than one of my CD's). I made a toast cd copy (which I presume is bit for bit) - at 2x, to take into consideration this whole laser strength thing. I checked the CD's in the finder, both were identical in size in bytes. The CD I burned on to was some professional black CD-R that he gave me that was given to him by an audio waveform analyst he knows working for CSIRO (big research company in australia, though they usually do environmental based stuff I think), who said this CD-R was his best bet quality wise.

To take perception and anticipation out of the equation, I changed and loaded CD's without him knowing which was which (like a 3rd party test). First I loaded up the copy, played 2 mins. Then, to mess around with things, I didnt load the original, but the copy again. He still said nothing (was doing that whole "eyes closed visualising the scene thing"). 2 mins on that too. Then, I put the real one in. 10 seconds into the track he said "I bet thats the original, and the other two were the copy".

Bang, he could pick the difference. He said the difference was less profound than previously (8x burning on regular CD-Rs - but that was with different albums), he could still hear a difference. It sounded "less real", less like he was there.

Now, his set up. His CD player is quite old (and expensive, along with his amps and speakers and whatever else those other boxes stacked on his table are), 15 or so years in fact. His amps and all that are valve amps, which while he said he notices some digital systems he has come across (through this waveform analyst guy) sound minorly better to him, the rest sound no where near as good, so he is still very keen on the old valve systems.

So umm thats the result. He's going up today to that analyst he knows, they are going to study the difference on all his various systems he has (and on newer cd players as well, as I said the age of it might make a difference as to what data it is/isnt picking up off the CD).

Any idea (without buying a new cd recorder or him buying a new drive) how the quality can be improved from here? He seems to think that the black professional cd-r's I used may have made a difference.




In any case, thank you all very much for your responses - this has been an extremely educational thread!!

[climber]

That is not quite a double blind test. For one, It would be fairly easy for you to tip off the listener without you even knowing it. The setup you described is almost texbook full of the errors described in a first year Stats course.

[Spheric Harlot]

Originally posted by climber:
That is not quite a double blind test. For one, It would be fairly easy for you to tip off the listener without you even knowing it. The setup you described is almost texbook full of the errors described in a first year Stats course.

Yes, but for the purposes of this thread, it's probably acceptable.

We have checksums above that seem to indicate that the computer-read data is in fact changed, and we have admittedly one-off anecdotal evidence that someone can tell the difference, so that'll just have to do for now.

-s*

[Developer]

Originally posted by Swiss Bob:
And therein lies the problem. We don't want the checksums at the desktop, we want them at the CD data stream.

I'm arguing on the assumption that if a computer CD-ROM drive can read both the original and the copy without errors, a CD player can do so as well.

[Swiss Bob]

Originally posted by Developer:
I'm arguing on the assumption that if a computer CD-ROM drive can read both the original and the copy without errors, a CD player can do so as well.

This is a flawed assumption - audio players aren't computers.

[chabig]

The audiophile guy could have made a lucky guess. Statistically, the experiment didn't prove anything. You should play the CDs maybe 20 times. If he can figure out which is real and which is the copy on a regular basis I'll be impressed. Otherwise I chaulk up his success to luck.

Knowing how CDs are encoded, there should be no difference between the two. Period.

This is a flawed assumption - audio players aren't computers.

True, but the optics are the same. Also, they don't have to read the data the same way. Remember that eight bits of data are encoded into 14 bits for error correction. Even if one drive makes some read errors, the original data stream will be recreated identically.

And the data stream is all that matters. The data stream could come from a CD, it could be streamed, it could be stored on punch cards, or on a USB keychain drive. It doesn't matter. If you pump those bits into the same decoder, they will sound the same.

[Spheric Harlot]

Originally posted by Developer:
I'm arguing on the assumption that if a computer CD-ROM drive can read both the original and the copy without errors, a CD player can do so as well.

a) as has been pointed out, audio CD players aren't computers, and

b) the assumption that ANY drive can read an optical medium without errors is just WRONG.

-s*

[Spheric Harlot]

Originally posted by chabig:
Even if one drive makes some read errors, the original data stream will be recreated identically.

This is incorrect. If this were true, there would be no need for error correction units in CD players (beyond what would be needed to reconstruct flawed data using the error correction info on the medium).

However, fact is, without EXTRA error correction, NO audio CD player would work. The data stream is NOT identical on any two CD players, nor likely on one and the same, depending on whether people are walking around the room, air pressure, dust particles, what have you.

Any time you listen to a CD, a certain portion of what you hear has been artificially generated by best-guess data interpolation. To believe otherwise is simply WRONG and buying into the Myth of Digital Equality. (A renowned German magazine - Stiftung Warentest - at one point declared that, since all CD players were digital 16-bit/44.1kHz, there was no point in testing machines for anything other than build quality, since the sound quality was equal for all!)

Also, a computer CD-ROM drive can go back and try to re-read faulty data (though I don't think it does for audio). An audio CD player does not have that luxury.

-s*

[kidtexas]

I always thought that the big difference between cheap cd players and expensive cd players is mostly NOT in the transport, but in the DAC's and other tasty components.

I think what we have going on here is not necessarily that the computer drive is reading the cd differently, but in the process of writing it, something is coming out differently. Mind you, my test wasn't very scientific, but I did read a cd twice, and the imported file had the same checksum both times.

More importantly, don't get all high and mighty by saying audio players and cd-rom drives are all that different. Audio is stored as data files on computers a hell of a lot nowadays in the recording process... witness protools, etc. ****, a portion of engineers use the Masterlink, which is nothing more that a stand alone harddrive recorder with a COMPUTER cd-rom in it. When done, you don't even mix down to an audio CD, you just burn a data CD with a 24 bit "tracks" on it (actually files).

My point is that maybe there are differences in cd-roms and cd players, etc, but the difference between audio and files is not the thing that is making the big "difference". I'd imagine the errors introduced are from the burning process, not from the reading process. Again, the two times I imported the same track from the same cd, i got the same checksum - the cd player was consistent in reading that disc. This is the same drive that read the original audio disc to make the copy. So (again, this isn't overly scientific because I'm not going to burn a bunch of cd's to prove my point), but my computer can consistently read audio off of a cd, it read the original audio cd (correctly presumably - even if not, it reads it wrongly the same way each time), but somewhere between the burning process, and the import of the same track from the copy, errors were introduced.

[Swiss Bob]

Originally posted by kidtexas:
I think what we have going on here is not necessarily that the computer drive is reading the cd differently, but in the process of writing it, something is coming out differently.

I would hope that the drive is reading the disk differently, because factory created CDAs and consumer created CDRs are two different formats.

Originally posted by kidtexas:
Audio is stored as data files on computers a hell of a lot nowadays in the recording process... witness protools, etc. ****, a portion of engineers use the Masterlink, which is nothing more that a stand alone harddrive recorder with a COMPUTER cd-rom in it.

The Masterlink produces Red Book (when you want it to), not Orange Book, which is why a lot of pros are using it. Your computer drive wouldn't produce a Red Book CD if your life depended on it.

Originally posted by kidtexas:
When done, you don't even mix down to an audio CD, you just burn a data CD with a 24 bit "tracks" on it (actually files).

Ermm... Good luck with playing that on a standard CD player.

[chabig]

I think what we have going on here is not necessarily that the computer drive is reading the cd differently, but in the process of writing it, something is coming out differently.

I agree with you except for one minor point. I don't think it's the writing that's different, but the coding. Here's the test I did:

1. I did an md5 checksum on an aiff file from a commercial audio CD. I repeated this three times. Each time I got the same result.

2. I then copied this aiff file to my hard drive and made two duplicates. I ran the md5 checksum on all three files. All three were identical and were also identical to the results from test 1.

3. I then used iTunes to make three audio CDs from the aiff file. I ran the checksum on the file from each CD and they were identical to each other, yet different from the original CD.

Conclusion: I have eliminated read and write errors as the source of the difference. The data correction built-in to the CD ensures that the data is read correctly--the aiff files are identical. The only thing that can be causing the copy to be different from the original is iTunes. There must be something in the way it encodes the CD audio that makes the file different.

Addendum: As iTunes is the only program I own that can burn audio CDs, I am stuck at this point. Perhaps someone with other software could run similar tests.

Chris

[kidtexas]

Originally posted by Swiss Bob:

The Masterlink produces Red Book (when you want it to), not Orange Book, which is why a lot of pros are using it. Your computer drive wouldn't produce a Red Book CD if your life depended on it.

Hmm. ok. If you say so. The Masterlink has a consumer CD-R burner in it. So why can it burn Red Book CD's, and a computer CD-R can't? Different software? Its not different media since they use the same blanks....

Originally posted by Swiss Bob:

Ermm... Good luck with playing that on a standard CD player.

Thanks for pointing out the obvious. My point for say this was to show that a lot of the audio that we listen to lives a significant portion of its life as audio files, i.e. data, that can't be played back by traditional audio players, but can be by "computers". I say "computers" because the Masterlink merely records its 24-bit audio (which is what most pro's are going to use) as AIFF files (I believe) onto a standard data disc that any computer should be able to read. Whether its a computer or a Masterlink, we're talking about reading files, not cd-a.

The point of all this is that distinctions between "audio" tracks on a cd and audio "files" is not necessarily a huge point... but maybe it is.


About the iTunes test just that was just run: Makes sense... iTunes converts aiff to whatever is stored on a cd (cda?) and changes occur. Presumably you could use Toast to make a device copy or something like it to get bit for bit copies...

[Swiss Bob]

Originally posted by kidtexas:
The point of all this is that distinctions between "audio" tracks on a cd and audio "files" is not necessarily a huge point... but maybe it is.

In the context of this thread, this is exactly the point. CDA is not equal to CDR, even bit-for-bit copies.

[kidtexas]

Originally posted by Swiss Bob:
In the context of this thread, this is exactly the point. CDA is not equal to CDR, even bit-for-bit copies.

Are you sure you mean CDA and CDR? Because once I burn my CDR (granted, from "data" and put it in a cd player, its treated as CDA. Likewise, once I put my CDA in a computer and read it/rip it, etc, its being treated not as CDA, but as a file storage device. Further more, that CDA that you are referring to was most likely an AIFF or an SD2 at some point in its life.

Regardless, there is a diffence that we are seeing. Is it truly due to the different ways a pressed CD is made and a CDR, or is it in the software that processes the data to put on the CD. I have no reason to believe that iTunes is particularly faithful to the original source - in my mind that it doesn't matter if it is. I'd like to see the same test performed a couple posts ago done on a CD made by some bit-for-bit copying utility. Does Toast do this? I know there is a program on PC that does it - can't remember the name though.

[chabig]

Originally posted by kidtexas:
About the iTunes test just that was just run: Makes sense... iTunes converts aiff to whatever is stored on a cd (cda?) and changes occur.

Yes but...I would have expected iTunes to encode the data according to standard (i.e. the same as commercial audio CD).

Chris

[kidtexas]

Originally posted by chabig:
Yes but...I would have expected iTunes to encode the data according to standard (i.e. the same as commercial audio CD).

Chris

And it does. Thats why you can play it on cd players that are made to play standard Cd-r's. But just because the info put on the cd by iTunes is standard doesn't mean it has to have a bit-for-bit accurate method of getting that data. Or accuracy in any other method. ****, for all I know it could take our AIFF's, convert them to 128 kbs MP3's, then convert it to CDA to burn on the CD. Just because that final CDA file is compatible to a standard doesn' t mean our audio didn't degrad/change. Obviously, the bit about the mp3 conversion is not true, but it does make my point.

[Swiss Bob]

Originally posted by kidtexas:
Are you sure you mean CDA and CDR? Because once I burn my CDR (granted, from "data" and put it in a cd player, its treated as CDA.

Tex, the only way you can make a "CDA" (in the way that I'm referring to it) is to get it pressed in a factory. Everything else is "CDR" (in the way that I'm referring to it).

What they put on the shelves of record stores and what your home burner comes out with are two completely different formats which play differently (notice the problems with CDRs on early CD players - if they played the same there wouldn't have been any problems whatsoever).

[voodoo]

Subject: [4-18-2] The audio data matches exactly, why do they sound different?
(2002/12/11)

Suppose you extract the audio track from the copy, and it's an exact binary match of the track you wrote from your hard drive, but the CDs don't sound quite the same. What then?

Most people don't notice any difference between originals and duplicates. Some people notice subtle differences, some people notice huge differences; on better CD players, the differences are harder to hear. Some say CD-R is better, some say worse. While it's true that "bits are bits", there *are* reasons why CD-Rs may sound different even when the data matches exactly.

The most prominent problem is jitter. This isn't the DAE "jitter" described in section (2-15), but rather a timebase error. A good overview can be found in the jitter article on http://www.digido.com/. A brief explanation follows.

Most CD players use a clock derived from the incoming digital signal to drive the digital-to-analog conversion. Even if the CD player gets all of the digital bits accurately, it will produce inferior results if the timing of the bits on the disc isn't precise. Put another way, something has to send a sample to the speakers 44100 times per second, and if it's speeding up and slowing down many times each second your ears are going to notice.

If you play a CD digitally (e.g. by ripping it and then playing it through a sound card), the quality of the CD doesn't matter, because it's the timing of the clock in the sound card that drives the output.

A fancy CD player could provide its own clock to drive the DAC, buffering up bits and playing them out in carefully controlled time. This is tricky though, because when you have two clocks in a system they are likely to drift apart, and you have to deal with buffer underruns and overruns when one outpaces the other. (A man with two watches never knows what time it is, because the watches almost never agree.) The timing from the disc is generally good when considered over a long period, so the challenge to CD player manufacturers is to design circuitry that produces a stable timing signal from a somewhat unstable source.

(This begs the question: does a CD player with anti-shock protection produce better sound? The player has to read the disc at 2x so it can buffer enough data to continue playing even when the CD player is jolted and loses tracking. Such players tend to do *worse* with CD-Rs because the higher read speed magnifies problems with marginal discs, but it's possible that they have less of a problem with jitter -- assuming, of course, that their internal clock is accurate and stable.)

It has been asserted that the clocking of bits on a CD-R isn't as precise as on a pressed CD. Writing at different speeds on different types of media requires adjustments to the "write strategy" (section (3-31)) that can result in individual "marks" being sloppier than at other speeds. This could account for inferior -- or at least different -- sound.

Yamaha believes they have found a partial solution for jitter problems with their Audio Master Quality feature. See section (2-41).


Some people have asserted that *any* two CDs, pressed or otherwise, will sound slightly different. Some claim to hear differences in identical CDs from different pressing plants. The former is silly, but the latter makes sense if one pressing plant is using a less-precise technology.

The manual for the CDD2000 reportedly states that the drive uses 4x oversampling when playing pressed CDs, but switches to 1x for CD-R. This affects the quality of the D/A conversion, and can make an audible difference.

http://www.mrichter.com/cdr/primer/losses.htm has some further thoughts, including a table showing signal level differences.

A paper was reportedly submitted to the Audio Engineering Society, entitled, "An Investigation of the Sonic Differences Between Numerically Identical Compact Discs", by Julian Dunn. Preprint 4339, the 101st AES convention.

An extremely technical introduction to CD reading is available at http://www.tc.umn.edu/~erick205/Papers/paper.html. This may shed some light on why reading audio CDs is difficult, as well as explain concepts like aliasing and dither.

If you are finding your CD-Rs to be noticeably inferior, try different media, different write speeds, a different player, or perhaps a different recorder. There is some evidence that different brands of media and recorders may work better for audio, but in the end it's a highly subjective matter. Some people say CD-Rs sound worse, some people say they sound better (and some people think vinyl records are still the best).



***********

from: http://www.cdrfaq.org/

[climber]

Voodo, you are still assuming that there is a difference in the data steams before the D/A converter. I still don?t see it. And I have yet to see anyone able to differentiate these differences when subjected to a proper double blind tests.

The theory about timing on the CD sounds awfully like the argument circulating a few years back, when marking the edge of a CD with a highlighter marker was in vogue.

If there is a difference, and I am not stating there isn?t, then it would be fairly trivial to show this using the proper test. But these anecdotal observations with a sample size of three are far from persuasive.

[voodoo]

I only posted the above for discussion. IMO digital is digital and that is the end of it. If a digital copy is flawless from the original as it is most of the time then there is no difference nor can there possibly be.

[chabig]

Thats why you can play it on cd players that are made to play standard Cd-r's. But just because the info put on the cd by iTunes is standard doesn't mean it has to have a bit-for-bit accurate method of getting that data.

If iTunes is encoding to the "standard" then it ought to be doing the same EFM coding and framing, and interleaving, etc. So I'd expect the result to be bit-for-bit identical.

Chris

[talisker]

Originally posted by chabig:
I agree with you except for one minor point. I don't think it's the writing that's different, but the coding. Here's the test I did:

1. I did an md5 checksum on an aiff file from a commercial audio CD. I repeated this three times. Each time I got the same result.

2. I then copied this aiff file to my hard drive and made two duplicates. I ran the md5 checksum on all three files. All three were identical and were also identical to the results from test 1.

3. I then used iTunes to make three audio CDs from the aiff file. I ran the checksum on the file from each CD and they were identical to each other, yet different from the original CD.

Conclusion: I have eliminated read and write errors as the source of the difference. The data correction built-in to the CD ensures that the data is read correctly--the aiff files are identical.

I'm afraid you havent eliminated read and write errors by this test. Just because the three checksums you ran on the original CD in step one were identical, does not mean all the data was read correctly from the CD. All it means is that the same data was read each time. They could all have had the same errors. I don't know enough about it to know whether that is possible (ie - do the errors occur at random, or could there be a level of fine detail that the CD player will consistently ignore or interpolate every time?), and unless you do, you can't draw any conclusions.

The only conclusive test I could imagine would be comparing a CD read using a high end CD tranport and digital output, to one read from the computer's CD player.

[imaxxedout69]

Uhm... okay, if you did this on a TiBook you had to ENCODE the old disc, then decode it and burn it onto a disc, correct? I'm guessing any quality loss was through the coding of hte MP3.

- Ca$h

[tooki]

Some comments:

1. Some computer CD-ROM drives read audio CDs in one pass only (the way an audio CD player will always do), interpolating any errors. But in more recent times, it's become relatively common for computer drives to re-read whenever errors (beyond those corrected by interleaving and EFM) are detected, usually slowing down the read speed. My Teac CD-RW drive will slow down to as low as about 1/8x when reading marginal discs.

What this means is that, for errors that interleaving and EFM cannot correct, different drives can produce varying output data streams. It also means that your iTunes copy will be different based on what drive was used to read the source disc. (I.e. the source disc may have had unrecoverable errors that were interpolated, while the copy has no unrecoverable errors -- but used "faulty" data to begin with.)

2. Binary data can't discriminate between certain frequencies. (Data is data, and the digitizing process abstracts the audio content from specific bits.) A damaged bit is no more likely to "attack" one frequency range than another. Binary errors in the error-corrected data stream thus will cause noise but not specific tonal differences. Any tonal differences cannot be functions of the digital transport, but rather of the A/D and D/A process. (Different DACs definitely sound different.)

3. A burned CDDA (audio CD) is absolutely red-book compliant. If it weren't, it couldn't be played in an audio CD player at all. (This is, btw, the key to some types of audio CD copy protection... they monkey with the disc to where it's no longer fully red-book compliant. A computer (as well as most DVD players and game consoles) expects it to be fully compliant, and when it sees that it's not, it considers it damaged. Most audio CD players are "dumb" and just ignore the intentional errors, thus happily playing the disc.)

4. CD-R, believe it or not, is not a standard!!! In fact, while media-drive compatibility has (largely) been established, the only "standard" a CD-R has to meet is to be readable by the CDDA/CD-ROM standard. Thus, CD-R discs and writers have in mind only to produce a disc that any "normal" CD transport will recognize. (CD-RW, on the other hand, is standardized on both the write and read ends of the process. CD-RW's optical characteristics are also fundamentally different from those of CD-ROM.)

Even an old CD player shouldn't have trouble with CD-Rs. If it does, then either the old transport is marginal, or the CD-R disc is, or both.

5. It's hard to exactly compare files ripped from an original and a copy because (unless you used a standalone copier) CD ripping mastering programs may leave in extra (or cut off early) a couple of frames of audio when ripping or burning. So to properly compare files, you'd have to very, very carefully "align" the data in both ripped samples and THEN examine what differences exist.

6. (My apologies to anyone this might offend.) It seems to me that audiophiles often lack common sense, or use mumbo-jumbo to fill in gaps in knowledge. Almost nobody is disputing that different audio systems sound different. But the reasons given by audiophiles are often devoid of any scientific validity. In particular, a lack of understanding of digital audio theory leads to application of analog audio principles (where the voltage stream is in direct relation to the sound being transmitted) to digital audio (where the voltage stream is HIGHLY abstracted from the sound being transmitted). This is like using an English spell checker on Chinese.



To the person who started this thread: I highly doubt that burning new copies of the disc from the existing audio files will make a difference. Instead, try burning new copy from audio data ripped using a different drive than the one it was ripped with originally. It may capture the audio from the original CD differently.

tooki

[zigzag]

Thanks tooki - very interesting.

[The Godfather]

Originally posted by voodoo:
snip Most CD players use a clock derived from the incoming digital signal to drive the digital-to-analog conversion. Even if the CD player gets all of the digital bits accurately, it will produce inferior results if the timing of the bits on the disc isn't precise. Put another way, something has to send a sample to the speakers 44100 times per second, and if it's speeding up and slowing down many times each second your ears are going to notice.

If you play a CD digitally (e.g. by ripping it and then playing it through a sound card), the quality of the CD doesn't matter, because it's the timing of the clock in the sound card that drives the output.

A fancy CD player could provide its own clock to drive the DAC, buffering up bits and playing them out in carefully controlled time. This is tricky though, because when you have two clocks in a system they are likely to drift apart, and you have to deal with buffer underruns and overruns when one outpaces the other. (A man with two watches never knows what time it is, because the watches almost never agree.) The timing from the disc is generally good when considered over a long period, so the challenge to CD player manufacturers is to design circuitry that produces a stable timing signal from a somewhat unstable source. snip

CDRFAQ seems to support my theory...

Originally posted by chabig:

Originally posted by The Godfather:
Could it be that all the ones and zeros are well copied, but the density of the indentations and lines is irregular in the copied CD? That would result in a skew in frequency and maybe noise in simple CD players.

No. "Indentations and lines" don't constitute data. All there is are ones and zeros. And the ones and zeros describe the waveform.

Understand that the data rate (samples per second) affects the frequency of the music at the DAC output. If you feed the sound samples from a CD to the DAC at 44100 samples per second, you get the intended frequencies. Now you have a CDR with the same bits as the CD, but the burner wrote them at a different density (bits per inch), the sound samples are going to be fed to the DAC at a faster (or slower) rate. This faster (or slower) rate of the same digital data will result in a frequency increase (or decrease). This frequency increase can be of a few hundredths of octave, and only audiophiles will be able to detect it.

I am not an audiophile and all my CDs are CDRs.

[Swiss Bob]

Originally posted by tooki:
3. A burned CDDA (audio CD) is absolutely red-book compliant. If it weren't, it couldn't be played in an audio CD player at all.

This is just plain wrong. Take a modern burned CD and pop it in an early 80's CD player. If it's fully Red Book it should play. They don't.
What you're seeing is that modern CD players can do more than Red Book.

Under the premise quoted, MP3 discs shouldn't be able to play (they're not Red Book), but... ...they do.

[G4ME]

i made a copy of Momentary Lapse of reason using toast, via disc copy. I can play it in my Old (early 90's) Tech Cd player, that normaly can't play regular CDRs, the ones i make in iTunes.

As for audio quality i can't tell the differance.

[chabig]

Originally posted by Swiss Bob:
Take a modern burned CD and pop it in an early 80's CD player. If it's fully Red Book it should play. They don't.
What you're seeing is that modern CD players can do more than Red Book.

I disagree. The reason the older CD player can't read a CD-R is because the physical media is different than a regular CD and the older players weren't designed to read it. The format of the data is identical.

[talisker]

Originally posted by tooki:

6. (My apologies to anyone this might offend.) It seems to me that audiophiles often lack common sense, or use mumbo-jumbo to fill in gaps in knowledge. Almost nobody is disputing that different audio systems sound different. But the reasons given by audiophiles are often devoid of any scientific validity. In particular, a lack of understanding of digital audio theory leads to application of analog audio principles (where the voltage stream is in direct relation to the sound being transmitted) to digital audio (where the voltage stream is HIGHLY abstracted from the sound being transmitted). This is like using an English spell checker on Chinese.

Thanks for the informative post. Regarding this particular comment, from this thread it's clear that there is another viewpoint that is equally wrong, that of the IT-geek digital devotee (ie. it's digital therefore it has to be perfect and cannot fail to be played perfectly on any equipment. The reason for that is...well, it's digital.)

[andymcdeee]

What capacity disk were you using Hornet?

If I recall correctly, a 640 MB audio CD contains 21 layers of the same information. Because errors are guaranteed.

A 700MB disk was introduced once it was discovered that less layers were needed to ensure safe playback - they were being overly cautious. There are only 19 layers on a 700MB disk.

And you can get larger capacity disks than that but there reliability is more questionable - they sacrifice error correction for space.

This is just from memory (and not a great one at that) and could explain why your CD-R's sound different.

If you've used 640MB disks then my theory is screwed.

[Spheric Harlot]

Originally posted by imaxxedout69:
Uhm... okay, if you did this on a TiBook you had to ENCODE the old disc, then decode it and burn it onto a disc, correct? I'm guessing any quality loss was through the coding of hte MP3.

- Ca$h

You may note that he transcoded to AIFF, not mp3.

[chabig]

If I recall correctly, a 640 MB audio CD contains 21 layers of the same information.

This is a new one! It's completely false. There is only one physical layer on an audio CD. It's just a big sprial of pits and lands.

Data on the disk is encoded with redundancy. Eight bits of audio data is encoded into 14 bits. Furthermore, the placement of the data is interleaved. Together these two techniques protect to a certain degree against both random and burst errors.

Chris

[Webscreamer]

This is kinda off the subject, but, are those black CDRs actually better?! I always thought the light ones ould be because thats how regular CDs are.

[awaspaas]

The amount of blatant misinformation from people who think they know what they're talking about is mind-boggling in this thread. But, I shouldn't be surprised, this is an internet forum after all.

[tooki]

Originally posted by Swiss Bob:
This is just plain wrong. Take a modern burned CD and pop it in an early 80's CD player. If it's fully Red Book it should play. They don't.
What you're seeing is that modern CD players can do more than Red Book.

Under the premise quoted, MP3 discs shouldn't be able to play (they're not Red Book), but... ...they do.

Sorry, then you have no understanding of the CD-R "format" or how programs like Toast or iTunes burn CDs.

"MP3 discs" are ISO9660 CD-ROMs full of mp3 files. Only very few players know how to read and decode this.

Audio CDs burned from MP3 files are red-book compliant, as the MP3 audio is decoded to PCM and THAT is burned to the CD along with all the necessary codes, etc.

Originally posted by chabig:
I disagree. The reason the older CD player can't read a CD-R is because the physical media is different than a regular CD and the older players weren't designed to read it. The format of the data is identical.

As I already stated, there is no CD-R read standard. CD-R is supposed to mimic the read characteristics of a pressed CD. If the CD reader, the disc, or both, are marginal, then they may not play well (just as is the case with a marginal pressed CD!). But the fact remains that the only read standards that CD-R adheres to are the SAME standards that pressed CDs must follow.

Originally posted by talisker:
Thanks for the informative post. Regarding this particular comment, from this thread it's clear that there is another viewpoint that is equally wrong, that of the IT-geek digital devotee (ie. it's digital therefore it has to be perfect and cannot fail to be played perfectly on any equipment. The reason for that is...well, it's digital.)

Indeed. Digital doesn't guarantee anything, other than that different physics apply to the signal. (As it so happens, digital signals have many positive characteristics, among others low sensitivity to noise and easy duplicability, at the cost of a MUCH lower data "payload".)

Originally posted by andymcdeee:
What capacity disk were you using Hornet?

If I recall correctly, a 640 MB audio CD contains 21 layers of the same information. Because errors are guaranteed.

A 700MB disk was introduced once it was discovered that less layers were needed to ensure safe playback - they were being overly cautious. There are only 19 layers on a 700MB disk.

And you can get larger capacity disks than that but there reliability is more questionable - they sacrifice error correction for space.

This is just from memory (and not a great one at that) and could explain why your CD-R's sound different.

If you've used 640MB disks then my theory is screwed.

CDs don't have multiple data layers. (DVDs can, and SACDs do.) What IS true is that higher-capacity discs squeeze the track spiral closer together, thus reducing the margin for error.

I for one have long lamented the disappearance of 550MB and 650MB CD-Rs from the market -- I essentially never need 700MB/80min worth on a disc, so basically, we are reducing data integrity in order to add space that most people never use. (Yamaha once determined that CD-Rs, on average, are burned only 1/3 full.) That also explains why Yamaha's final CD burner, the F1, has the audio mastering mode that burns 60 minutes of audio onto an 80 minute disc by increasing the length of the pits and lands, ostensibly increasing the playback quality.

Note that squeezing the track to fit longer playback isn't something new -- even before CD burners became omnipresent, some CDs were extra-long, like Michael Jackson's 78-minute CD "Dangerous" album.



CDs are in fact made of layers: 1. a polycarbonate plastic substrate, into which the data [in a pressed CD] or the pregroove [in a CD-R] is pressed; 2. a dye layer in a CD-R; 3. a reflective metal layer [aluminum in pressed CDs, gold in the best CD-Rs and in some special-edition pressed CDs, silver or other metals in other CD-Rs]; 4. a layer of protective lacquer; 5. any silk-screened labeling, or a printable coating [on printable CD-Rs].

In a double-layer DVD, layers 1, 3 and 4 are repeated, but with the outermost reflective layer being very thin such as to be half-reflective, half-transmissive. In double-sided DVDs, two such sandwiches are glued back-to-back. (Single-layer DVDs simply use thicker substrates. Single-sided DVDs are just one "sandwich" glued to a clear substrate to bring it up to the necessary thickness.)

tooki

[andymcdeee]

Originally posted by tooki:
CDs don't have multiple data layers. (DVDs can, and SACDs do.) What IS true is that higher-capacity discs squeeze the track spiral closer together, thus reducing the margin for error.

Alright. So a little bit of what I said may have been accurate. Ah well, I had a go.

[tooki]

Yup.

Oh yeah, one thing I forgot to add:
"Black" CD-R discs are not intrinsically of any higher (or lower) quality than traditional clear ones. The "black" (actually, dark red-purple) is invisible to the infrared light of the laser, so as far as the CD drive is concerned, it is clear.

That said (and this is totally unsubstantiated by any kind of evidence) I could imagine that the dark discs could filter out UV or visible light radiation that could theoretically help degrade the data layer (since CD-Rs are negatively sensitive to sun exposure).

THAT said, I still rely on Verbatim DataLife CDs.

tooki