Well what do you know, our friends at MSNBC think the sound quality is not quite "up to par." In fact they think that "Apple downloads ring sour note."
Fitting. Considering the article is written for MSNBC.
I don't know how everyone else feels, but I've recently noticed that I can identify AAC encoded files in other people's iTunes shares... This is before I select view options to confirm the type/rate.... And, more alarmingly, this is with music I don't know well.
I can't really express what I'm hearing, it's nothing obvious like the ringing or someone in sodden rubbers trodding all across your music that happens with say.... 128kbps mp3. It's not particularly abrasive, but there just appears to be *something* in the music that makes me say.... that's an AAC... and boom, it IS.
I realize that all that sounds about as convincing as seeing the Virgin Mary in a mound of cigarette ash, but hey, it's what I'm hearing.
I'm sure there's a little alternative motivation behind the articles, BUT, they're not entirely off the mark. For a dollar a song, basically the cost of a pressed CD (when you add up the tracks.) iTMS really ought to offer better quality than 128Kbps. You're getting convenience and flexibility, but not "quality".
Add me to the list of people who can tell the difference between an MP3 and a CD track, rather easily. Tested out a few differnet bit rates of Cohen, Springsteen, Susan Vega, The Doors, Mazzy Star, SRV, just a little this and that, what was in the CD changer, and a quick disc of MP3's from 128kpbs, a bunch of 224-256 and a few 320. You can tell, but the later are not offensive and quite listenable.
Didn't try out AAC yet.
Now I could have some (or all) of this wrong, but converting an MP3 to a CD track should further reduce the fidelity because of way MP3's work. They throw out info, this much we agree on, but what do they do when they play back? This sound must be reconstructed out of somewhere. A CD, while not a compression format, has a finite resolution described by a sampling rate and a word length. Mebbe it's not perfect, but working from a good recording you can do some nice things. Working from an MP3 it has to sample 44.1K 16bit words (1422kbps of data) from a maximum of 320kbps of data. It's like having only one of every fifth bit and having to guess the rest in the conversion process. I probably still haven't explained it well, but this is what I meant by "Not fooling your CD player" These "new" bits are a fabrication, they're plotted against a general guide to what the sound should be, but basically they're another level of guessing. In the MP3 source, sound is merely "missing" in the CD made from said MP3, the "missing" sound has been effectively "estimated/invented" to get the requisite "bits" into the track. It's even at this stage further removed from the original than the MP3, not because you throw out more info, but because you have to invent some to get the fomat to fit. If you then make an MP3 rip of this CD (created from an MP3 source) you create yet another generational loss.
That's the way I understand it, the quality is worse than the Mp3, (probably not noticeably) because now the bits are not only a smaller sample of the original, they're mixed iin with 4/5ths worth of psuedo-bits!
Naturally, if we stay within the realm of MP3, like any digital medium, it can be copied infinitely without a loss in quality, but if we start converting from one format to the other, regardless of the direction conversion, "fidelity" (the sameness to the original recording) diminishes.
This is why, I think that if the goal is to allow me to have a track that I can use to make a "CD" copy for myself, for play in my car, on my stereo, etc etc... then it needs to be the highest bit rate possible, if they're just for computer/Mp3-portable player use, then a slightly lower quality is OK, but by no means ideal.
Now, if you buy good albums from good artists, then the cost of buying all the tracks is still worth it. iTunes is strickly for "one hit wonders" or one or two "singles" from otherwise weak artists.
MP3 file -> decoding -> 16-bit * 44.1K/sec audio stream -> store to CD
When you playback the CD made from the MP3:
read from CD -> 16-bit * 44.1K/sec audio stream -> digital-to-analog converter -> amplification -> speakers/headphones -> your ears
This sound must be reconstructed out of somewhere. A CD, while not a compression format, has a finite resolution described by a sampling rate and a word length. Mebbe it's not perfect, but working from a good recording you can do some nice things. Working from an MP3 it has to sample 44.1K 16bit words (1422kbps of data) from a maximum of 320kbps of data. It's like having only one of every fifth bit and having to guess the rest in the conversion process. I probably still haven't explained it well, but this is what I meant by "Not fooling your CD player"
A digital-to-audio convertor (DAC) has exactly the same demands that you state that a CD has. Your Mac (or your PC or your iPod) does not contain any built-only-for-compressed-audio DAC that can be fed directly from an MP3 file. That very same data that you write when you burn a CD is the same data that gets fed to a DAC so you can listen to an MP3.
By the way, all of this applies to AAC or any other compressed audio format as well as to MP3.
Thanks shetline, mebbe I'm a "little" dense here -- or a lot! -- but I'm still not getting it. OK, so I know the DAC converts the signal to something listenable (audio, hence D A C), and then this is recorded to CD. See, I'm haven't explained myself well, but it seems to me that it is impossible for the recorded CD to have more resolution than the source (in this case an MP3) yet the recording of a CD requires 1422bits of info. Sure the DAC plays back an MP3 at 44Khz 16 bit quality, but this is from a real maximum of only 320 bits. The rest of the resolution recorded onto the CD (the other 1102 bits) where do they come from? They have to be recorded from a model that is essentially missing them, or allowing an algorthym to reconstruct them (is this not the psycho-acoustic model of MP3). I think in a sense, it is valid to say that "bits" have been invented or guestimated when you do this.
Ahh, I don't have the lingo, and more than likely a cloudy understanding, someone help?
Thanks shetline, mebbe I'm a "little" dense here -- or a lot! -- but I'm still not getting it. OK, so I know the DAC converts the signal to something listenable (audio, hence D A C)
We're going along fine here, and then...
, and then this is recorded to CD.
The output from a DAC is not what gets recorded to a CD. CDs are digital, and the output from a DAC is analog.
It's the output from an MP3 decoder, which is a decompression algorithm that gets fed into a DAC so you can listen to an MP3, or that gets written onto a CD when you burn the MP3.
You're concerned about missing bits? (That's not exactly the right way to look at it, but it'll do for now.) Even with CDs totally out of the picture, you can't listen to an MP3 until those "missing bits" have been filled in. A DAC needs to have every bit spelled out too, just like a CD, or it isn't going to be able to create a listenable signal.
See, I'm haven't explained myself well, but it seems to me that it is impossible for the recorded CD to have more resolution than the source (in this case an MP3)
No, not more resolution. Equal resolution. I never claimed that a CD made from an MP3 file sounds better than the source MP3. It is equal in resolution to the MP3 from which it is created, and, like the MP3, lower in resolution than the original CD from which the MP3 was derived.
yet the recording of a CD requires 1422bits of info. Sure the DAC plays back an MP3 at 44Khz 16 bit quality, but this is from a real maximum of only 320 bits. The rest of the resolution recorded onto the CD (the other 1102 bits) where do they come from?
The CD and the DAC both get these "missing bits" from the very same place -- the same MP3 decoder that unpacks the MP3 data to feed either a DAC or a CD burner.
They have to be recorded from a model that is essentially missing them, or allowing an algorthym to reconstruct them (is this not the psycho-acoustic model of MP3). I think in a sense, it is valid to say that "bits" have been invented or guestimated when you do this.
I'll try to find a good link later for how MP3 and most other audio compression schemes work. Fascinating stuff! (Well, at least to an appropriately geeky mind. )
I can hear that a CD burned at low speed sounds better.
I've also heard that painting the edges of your CDs with a green magic marker will make them sound better. That putting a brick on top of your amplifier will make CDs sound better.
Subjective opinions of sound quality are notoriously susceptible to the power of suggestion.
Burning speed effecting sound quality, short of blatantly obvious skipping, popping, and clicking, etc., makes no sense at all if you know anything about the way CDs work.
Of course, many people don't give a hoot whether something makes sense or not. They tried slower burning. They heard an improvement. That settles it. But really, when usually this kind of stuff is just a placebo affect, just how many placebo effects do we need to collect and disseminate in the guise of sage advice over and over again?
I can hear that a CD burned at low speed sounds better.
Thanks for the tip. I was having lots of problems getting my burned discs (24x) to play in my 4 year old SONY CD changer (car). Sometimes it just wouldn't recognize the disc and maybe skip tracks at best. After reading your comments last night, I tried burning at (1x) with the same burner and same CD-R brand. This (1X) burnt disc works just fine in my car. So, I guess burning speed does indeed have an effect on playback quality and compatibility with most players out there.
I couldn't hear any sound difference when played on my (same car) in-dash CD receiver though.
Thanks for the tip. I was having lots of problems getting my burned discs (24x) to play in my 4 year old SONY CD changer (car). Sometimes it just wouldn't recognize the disc and maybe skip tracks at best.
This kind of failure from different burn speeds makes sense. Nearly any failure in a digital medium is not subtle.
What needs to be taken with a massively large grain of salt is when someone claims that a slower burn makes a CD "sound better", aside from blatantly obvious clicking, skipping, and outright failure to play.
"The vocals sounded richer and more detailed. There was better localization of the sound stage..." Blah. Blah Blah. Odds are that no matter how certain someone is that they've heard these effects and that they aren't fooling themselves -- they are being fooled. It's just placebo effect, the power of suggestion.
This kind of failure from different burn speeds makes sense. Nearly any failure in a digital medium is not subtle.
What needs to be taken with a massively large grain of salt is when someone claims that a slower burn makes a CD "sound better", aside from blatantly obvious clicking, skipping, and outright failure to play.
"The vocals sounded richer and more detailed. There was better localization of the sound stage..." Blah. Blah Blah. Odds are that no matter how certain someone is that they've heard these effects and that they aren't fooling themselves -- they are being fooled. It's just placebo effect, the power of suggestion.
I'm not talking about a richer sound, better localization and so on.
You obviously agree that burning discs at high speed means more errors. Many errors on a CD = bad sound.
I'm not talking about a richer sound, better localization and so on.
You obviously agree that burning discs at high speed means more errors. Many errors on a CD = bad sound.
If by "bad sound" you mean obviously blatant clicking, skipping, and failure to play, yes. That's definitely bad sound!
But "bad sound" as in some sort of general gestalt quality of the sound -- hissy, tinny, muffled, grainy, poor imaging, etc. -- no, I won't agree there. High error rates will not produce these kinds of effects.
There are three classes of errors when reading data from a CD:
Recoverable errors: The audio data is not read perfectly, but any errors are detected and corrected, restoring the signal exactly to its original intended form. This can have no effect on sound quality, because you're still recovering exactly all of the audio data in its original form.
Simple experiments have shown that even with cheap CD players the most typical result of playing a CD that's in reasonably good condition is that errors are infrequent, and when they do occur, they are nearly all of the recoverable variety.
Concealed errors: The audio data is not read perfectly, errors are detected, but the proper values for the corrupted data cannot be determined. In this case, the CD player must use guesswork to determine the missing data. Does this decrease fidelity? Sure... but only for a very brief moment. For an over-all unsatisfying sound quality to result from concealed errors you'd have to be getting concealed errors at such an extraordinarily high and continuous rate that you couldn't help but also having plenty of unrecoverable, unconcealed errors at the same time.
Unrecoverable, unconcealed errors: The audio data is so corrupted that errors can no longer be either corrected or concealed. The audible results are blatant: pops, clicks, chirps, skipping, complete failure to play.
It's in the nature of digital media: You get perfect recovery of data, or you get obvious failures. There is the remote theoretical chance of something in between, but the odds against getting such results, especially on a consistent basis ("All I know is that my 1x CDs sound better to me than my 12x CDs!) are astronomically high.
I've read about the CD burning speed issue, and I think it might be dirctly related to the depth of the pits burned on the disc. According to Yamaha, it is possible to burn deeper pits, more like from a pressed CD, and thus more easily read by even older CD players. I haven't encountered a CD player that won't play burned discs, even my slightly older carousel. I imagine that as speeds of media increase, they make a slighter impression on discs. No problem for CD-rom drives, but sometimes the pits and valleys may not be distinct enough for some players, so burning at a slower rate might ensure that each pit is deeper. I forget what Yamaha calls this feature of their burners, but they claim it results in a disc with pits almost as deep as stuio pressed CD. Interestingly, this feature only works up to 4X speeds. iDunno. I would imagine that all bit for bit copies of CD's have IDENTICAL audio quality to the original, and any reductions in quality would have to be directly due to an inability to read the burned media.
Still can't quite wrap my head around the MP3 to CD thing, though. Ah well.
Instead of mechanically pressing a CD with indentations, a CD-R writes data to a disc by using it's laser to burn 'pits' into the organic dye. When heated beyond a critical temperature, the area "burned" becomes opaque (or absorptive) through a chemical reaction to the heat and subsequently reflects less light than areas that have not been heated by the laser. This system is designed to mimic the way light reflects cleanly off a "land" on a normal CD, but is scattered by a "pit", so a CD-R disc's data is represented by burned and non-burned areas, in a similar manner to how data on a normal CD is represented by its pits and lands. Consequently, a CD-R disc can generally be used in a normal CD player as if it were a normal CD.
Just a quick question- is there a difference betweenthe AIFF and CDDA formats? I've tried ripping CD's to AIFF in iTunes and get slightly larger files, but have been told that they are synonymous. What's the real deal?
Ah, an earlier article I read referred to the technology making "pits" and "lands" and even earlier Yamaha graphics suggested "pits" but what they're really playing with is the length of the reflective/opaque dots and dashes. Still within tolerances, but just a bit longer to make a clearer distinction between peak and valley. The result should be playable in more players then, and last a bit longer before it's susceptible to errors.
I've listened to AAC files from both iTunes and AACelerator, at varying bit rates, and compared them to MP3 files in the same bit-rate range. My very general conclusion is that AAC encoded files are about the same size at the same bit rate as MP3, however you can save space because you don't have to go up around 256 kbps or higher to get close to CD quality with AAC.
I don't suspect 128 kbps is really "CD quality"; that's RDF all the way. I do think however, that 128 kbps AAC is easily equivalent to about 224 kbps MP3, maybe 256 on certain types of audio. But it's not as pure as what you get from a CD at this point IMO.
One person mentioned this but no one else commented on it: you should definitely turn off the Sound Enhancer and Sound Check in your iTunes preferences.
I was wondering what the heck was going on when I was listening to my music and in some parts, the music would get quieter... I thought there was something wrong with this AAC stuff, but it also happened on my old mp3s too. So I discovered the Sound Enhancer and Sound Check options and turned them both off. Now the music plays as it should--no funky changes in volume levels...
Nothing is "CD Quality" that is the biggest farce and marketing Misnomer of the new century. I have 300 CDs and they all have varying levels of quality. Some sound like pure crap and others pristine. Anyone can claim CD Quality.
Comments
Fitting. Considering the article is written for MSNBC.
I can't really express what I'm hearing, it's nothing obvious like the ringing or someone in sodden rubbers trodding all across your music that happens with say.... 128kbps mp3. It's not particularly abrasive, but there just appears to be *something* in the music that makes me say.... that's an AAC... and boom, it IS.
I realize that all that sounds about as convincing as seeing the Virgin Mary in a mound of cigarette ash, but hey, it's what I'm hearing.
Add me to the list of people who can tell the difference between an MP3 and a CD track, rather easily. Tested out a few differnet bit rates of Cohen, Springsteen, Susan Vega, The Doors, Mazzy Star, SRV, just a little this and that, what was in the CD changer, and a quick disc of MP3's from 128kpbs, a bunch of 224-256 and a few 320. You can tell, but the later are not offensive and quite listenable.
Didn't try out AAC yet.
Now I could have some (or all) of this wrong, but converting an MP3 to a CD track should further reduce the fidelity because of way MP3's work. They throw out info, this much we agree on, but what do they do when they play back? This sound must be reconstructed out of somewhere. A CD, while not a compression format, has a finite resolution described by a sampling rate and a word length. Mebbe it's not perfect, but working from a good recording you can do some nice things. Working from an MP3 it has to sample 44.1K 16bit words (1422kbps of data) from a maximum of 320kbps of data. It's like having only one of every fifth bit and having to guess the rest in the conversion process. I probably still haven't explained it well, but this is what I meant by "Not fooling your CD player" These "new" bits are a fabrication, they're plotted against a general guide to what the sound should be, but basically they're another level of guessing. In the MP3 source, sound is merely "missing" in the CD made from said MP3, the "missing" sound has been effectively "estimated/invented" to get the requisite "bits" into the track. It's even at this stage further removed from the original than the MP3, not because you throw out more info, but because you have to invent some to get the fomat to fit. If you then make an MP3 rip of this CD (created from an MP3 source) you create yet another generational loss.
That's the way I understand it, the quality is worse than the Mp3, (probably not noticeably) because now the bits are not only a smaller sample of the original, they're mixed iin with 4/5ths worth of psuedo-bits!
Naturally, if we stay within the realm of MP3, like any digital medium, it can be copied infinitely without a loss in quality, but if we start converting from one format to the other, regardless of the direction conversion, "fidelity" (the sameness to the original recording) diminishes.
This is why, I think that if the goal is to allow me to have a track that I can use to make a "CD" copy for myself, for play in my car, on my stereo, etc etc... then it needs to be the highest bit rate possible, if they're just for computer/Mp3-portable player use, then a slightly lower quality is OK, but by no means ideal.
Now, if you buy good albums from good artists, then the cost of buying all the tracks is still worth it. iTunes is strickly for "one hit wonders" or one or two "singles" from otherwise weak artists.
Originally posted by JLL
...I think that 128bit AACs sound great, and I've compared them to the original CD on my stereo.
But when you burn them onto CDs, make sure that you are burning them at low speed - 1x preferably.
Quick techie question:
Does burning music onto CDs at lower speeds enhances playback quality on a cd player or just makes CDs more compatible?
Originally posted by Matsu
Now I could have some (or all) of this wrong, but converting an MP3 to a CD track should further reduce the fidelity because of way MP3's work.
Sorry to say, but your first conclusion here shows some confusion about how MP3s work.
They throw out info, this much we agree on, but what do they do when they play back?
MP3's do exactly the same thing, in terms of audio data, when you play them back directly, or when you write them to a CD.
Here's the typical direct playback chain:
MP3 file -> decoding -> 16-bit * 44.1K/sec audio stream -> digital-to-analog converter -> amplification -> speakers/headphones -> your ears
Here's the MP3 burn process:
MP3 file -> decoding -> 16-bit * 44.1K/sec audio stream -> store to CD
When you playback the CD made from the MP3:
read from CD -> 16-bit * 44.1K/sec audio stream -> digital-to-analog converter -> amplification -> speakers/headphones -> your ears
This sound must be reconstructed out of somewhere. A CD, while not a compression format, has a finite resolution described by a sampling rate and a word length. Mebbe it's not perfect, but working from a good recording you can do some nice things. Working from an MP3 it has to sample 44.1K 16bit words (1422kbps of data) from a maximum of 320kbps of data. It's like having only one of every fifth bit and having to guess the rest in the conversion process. I probably still haven't explained it well, but this is what I meant by "Not fooling your CD player"
A digital-to-audio convertor (DAC) has exactly the same demands that you state that a CD has. Your Mac (or your PC or your iPod) does not contain any built-only-for-compressed-audio DAC that can be fed directly from an MP3 file. That very same data that you write when you burn a CD is the same data that gets fed to a DAC so you can listen to an MP3.
By the way, all of this applies to AAC or any other compressed audio format as well as to MP3.
Originally posted by Bill M
Quick techie question:
Does burning music onto CDs at lower speeds enhances playback quality on a cd player or just makes CDs more compatible?
I can hear that a CD burned at low speed sounds better.
Ahh, I don't have the lingo, and more than likely a cloudy understanding, someone help?
Originally posted by Matsu
Thanks shetline, mebbe I'm a "little" dense here -- or a lot! -- but I'm still not getting it. OK, so I know the DAC converts the signal to something listenable (audio, hence D A C)
We're going along fine here, and then...
, and then this is recorded to CD.
The output from a DAC is not what gets recorded to a CD. CDs are digital, and the output from a DAC is analog.
It's the output from an MP3 decoder, which is a decompression algorithm that gets fed into a DAC so you can listen to an MP3, or that gets written onto a CD when you burn the MP3.
You're concerned about missing bits? (That's not exactly the right way to look at it, but it'll do for now.) Even with CDs totally out of the picture, you can't listen to an MP3 until those "missing bits" have been filled in. A DAC needs to have every bit spelled out too, just like a CD, or it isn't going to be able to create a listenable signal.
See, I'm haven't explained myself well, but it seems to me that it is impossible for the recorded CD to have more resolution than the source (in this case an MP3)
No, not more resolution. Equal resolution. I never claimed that a CD made from an MP3 file sounds better than the source MP3. It is equal in resolution to the MP3 from which it is created, and, like the MP3, lower in resolution than the original CD from which the MP3 was derived.
yet the recording of a CD requires 1422bits of info. Sure the DAC plays back an MP3 at 44Khz 16 bit quality, but this is from a real maximum of only 320 bits. The rest of the resolution recorded onto the CD (the other 1102 bits) where do they come from?
The CD and the DAC both get these "missing bits" from the very same place -- the same MP3 decoder that unpacks the MP3 data to feed either a DAC or a CD burner.
They have to be recorded from a model that is essentially missing them, or allowing an algorthym to reconstruct them (is this not the psycho-acoustic model of MP3). I think in a sense, it is valid to say that "bits" have been invented or guestimated when you do this.
I'll try to find a good link later for how MP3 and most other audio compression schemes work. Fascinating stuff! (Well, at least to an appropriately geeky mind.
Originally posted by JLL
I can hear that a CD burned at low speed sounds better.
I've also heard that painting the edges of your CDs with a green magic marker will make them sound better. That putting a brick on top of your amplifier will make CDs sound better.
Subjective opinions of sound quality are notoriously susceptible to the power of suggestion.
Burning speed effecting sound quality, short of blatantly obvious skipping, popping, and clicking, etc., makes no sense at all if you know anything about the way CDs work.
Of course, many people don't give a hoot whether something makes sense or not. They tried slower burning. They heard an improvement. That settles it. But really, when usually this kind of stuff is just a placebo affect, just how many placebo effects do we need to collect and disseminate in the guise of sage advice over and over again?
Originally posted by JLL
I can hear that a CD burned at low speed sounds better.
Thanks for the tip. I was having lots of problems getting my burned discs (24x) to play in my 4 year old SONY CD changer (car). Sometimes it just wouldn't recognize the disc and maybe skip tracks at best. After reading your comments last night, I tried burning at (1x) with the same burner and same CD-R brand. This (1X) burnt disc works just fine in my car. So, I guess burning speed does indeed have an effect on playback quality and compatibility with most players out there.
I couldn't hear any sound difference when played on my (same car) in-dash CD receiver though.
Thanks,
Bill
Originally posted by Bill M
Thanks for the tip. I was having lots of problems getting my burned discs (24x) to play in my 4 year old SONY CD changer (car). Sometimes it just wouldn't recognize the disc and maybe skip tracks at best.
This kind of failure from different burn speeds makes sense. Nearly any failure in a digital medium is not subtle.
What needs to be taken with a massively large grain of salt is when someone claims that a slower burn makes a CD "sound better", aside from blatantly obvious clicking, skipping, and outright failure to play.
"The vocals sounded richer and more detailed. There was better localization of the sound stage..." Blah. Blah Blah. Odds are that no matter how certain someone is that they've heard these effects and that they aren't fooling themselves -- they are being fooled. It's just placebo effect, the power of suggestion.
Originally posted by shetline
This kind of failure from different burn speeds makes sense. Nearly any failure in a digital medium is not subtle.
What needs to be taken with a massively large grain of salt is when someone claims that a slower burn makes a CD "sound better", aside from blatantly obvious clicking, skipping, and outright failure to play.
"The vocals sounded richer and more detailed. There was better localization of the sound stage..." Blah. Blah Blah. Odds are that no matter how certain someone is that they've heard these effects and that they aren't fooling themselves -- they are being fooled. It's just placebo effect, the power of suggestion.
I'm not talking about a richer sound, better localization and so on.
You obviously agree that burning discs at high speed means more errors. Many errors on a CD = bad sound.
Originally posted by JLL
I'm not talking about a richer sound, better localization and so on.
You obviously agree that burning discs at high speed means more errors. Many errors on a CD = bad sound.
If by "bad sound" you mean obviously blatant clicking, skipping, and failure to play, yes. That's definitely bad sound!
But "bad sound" as in some sort of general gestalt quality of the sound -- hissy, tinny, muffled, grainy, poor imaging, etc. -- no, I won't agree there. High error rates will not produce these kinds of effects.
There are three classes of errors when reading data from a CD:
- Recoverable errors: The audio data is not read perfectly, but any errors are detected and corrected, restoring the signal exactly to its original intended form. This can have no effect on sound quality, because you're still recovering exactly all of the audio data in its original form.
- Concealed errors: The audio data is not read perfectly, errors are detected, but the proper values for the corrupted data cannot be determined. In this case, the CD player must use guesswork to determine the missing data. Does this decrease fidelity? Sure... but only for a very brief moment. For an over-all unsatisfying sound quality to result from concealed errors you'd have to be getting concealed errors at such an extraordinarily high and continuous rate that you couldn't help but also having plenty of unrecoverable, unconcealed errors at the same time.
- Unrecoverable, unconcealed errors: The audio data is so corrupted that errors can no longer be either corrected or concealed. The audible results are blatant: pops, clicks, chirps, skipping, complete failure to play.
It's in the nature of digital media: You get perfect recovery of data, or you get obvious failures. There is the remote theoretical chance of something in between, but the odds against getting such results, especially on a consistent basis ("All I know is that my 1x CDs sound better to me than my 12x CDs!) are astronomically high.Simple experiments have shown that even with cheap CD players the most typical result of playing a CD that's in reasonably good condition is that errors are infrequent, and when they do occur, they are nearly all of the recoverable variety.
Still can't quite wrap my head around the MP3 to CD thing, though. Ah well.
Instead of mechanically pressing a CD with indentations, a CD-R writes data to a disc by using it's laser to burn 'pits' into the organic dye. When heated beyond a critical temperature, the area "burned" becomes opaque (or absorptive) through a chemical reaction to the heat and subsequently reflects less light than areas that have not been heated by the laser. This system is designed to mimic the way light reflects cleanly off a "land" on a normal CD, but is scattered by a "pit", so a CD-R disc's data is represented by burned and non-burned areas, in a similar manner to how data on a normal CD is represented by its pits and lands. Consequently, a CD-R disc can generally be used in a normal CD player as if it were a normal CD.
I don't suspect 128 kbps is really "CD quality"; that's RDF all the way. I do think however, that 128 kbps AAC is easily equivalent to about 224 kbps MP3, maybe 256 on certain types of audio. But it's not as pure as what you get from a CD at this point IMO.
I was wondering what the heck was going on when I was listening to my music and in some parts, the music would get quieter... I thought there was something wrong with this AAC stuff, but it also happened on my old mp3s too. So I discovered the Sound Enhancer and Sound Check options and turned them both off. Now the music plays as it should--no funky changes in volume levels...