Burning AAC files then re-importing them
I'm aware that when dealing with lossy compression, it's best to avoid extra decode/recode cycles. However, I was curious just how much effect I would notice if I burned some of my new AAC files to CD, and then reimported them.
The original files were AAC at 128K, from the iTunes music store (a couple of Tori Amos cuts, and one Suzanne Vega). I burned these files to CD to get them into uncompressed form, then reimported from the CD using AAC at 192K -- choosing a higher bit rate than the originals in hopes of reducing the impact of an extra compression cycle.
I then burned both the originals and the second-generation files to a CD-RW, and took the results down to my "real" stereo system which has some nice B&W P6 speakers.
I didn't spend a whole lot of effort fishing for differences -- it's very easy to fool yourself that way unless you've got a way to "blind" the experiment anyway -- but certainly, there weren't any glaring problems and the second generation files were just as satisfying for me to listen to as the first.
Using Amadeus (audio editing software), I tried taking a pair of AIFF files (one first gen, the other second), and tried to get a difference signal between the two by inverting one file and blending it with the other. (I've done this before testing MP3 -- you can get some weird sound effects this way!) Unfortunately, I couldn't get the two signals properly in phase with each other.
I don't have any desire to pirate music -- I've never been into Napster-ish kinds of things, Apple's already started making money from me selling music, and they will continue to do so -- but the DRM on the purchased has the potential to get annoying.
For convenience I'm thinking it might be worth it to strip off the DRM using this kind of decode/encode cycle at the risk a slight loss of quality. I'm not doing anything now except backing up my purchases as standard CDs, but I think that from what I've seen (or rather, heard) I won't mind too much if I have to reimport and recompress from the decoded music at a later date if I run into any DRM hassles.
The original files were AAC at 128K, from the iTunes music store (a couple of Tori Amos cuts, and one Suzanne Vega). I burned these files to CD to get them into uncompressed form, then reimported from the CD using AAC at 192K -- choosing a higher bit rate than the originals in hopes of reducing the impact of an extra compression cycle.
I then burned both the originals and the second-generation files to a CD-RW, and took the results down to my "real" stereo system which has some nice B&W P6 speakers.
I didn't spend a whole lot of effort fishing for differences -- it's very easy to fool yourself that way unless you've got a way to "blind" the experiment anyway -- but certainly, there weren't any glaring problems and the second generation files were just as satisfying for me to listen to as the first.
Using Amadeus (audio editing software), I tried taking a pair of AIFF files (one first gen, the other second), and tried to get a difference signal between the two by inverting one file and blending it with the other. (I've done this before testing MP3 -- you can get some weird sound effects this way!) Unfortunately, I couldn't get the two signals properly in phase with each other.
I don't have any desire to pirate music -- I've never been into Napster-ish kinds of things, Apple's already started making money from me selling music, and they will continue to do so -- but the DRM on the purchased has the potential to get annoying.
For convenience I'm thinking it might be worth it to strip off the DRM using this kind of decode/encode cycle at the risk a slight loss of quality. I'm not doing anything now except backing up my purchases as standard CDs, but I think that from what I've seen (or rather, heard) I won't mind too much if I have to reimport and recompress from the decoded music at a later date if I run into any DRM hassles.
Comments
Anyway, to do a 'blind' test, I have an idea (although I'm too lazy to do what you've done.) Burn the same song on one CD 6 times. The first 3 the original AAC from Apple, and the second 3 the 192 kbs AAC you created. Then just put on some headphones and shuffle the CD. Listen to the song 3-4 times and decide if you ever heard a difference.
Originally posted by Messiah
What's DRM?
Digital Rights Management. The effort to control who has what access to data, and when they can have that access.
Originally posted by shetline
I'm aware that when dealing with lossy compression, it's best to avoid extra decode/recode cycles. However, I was curious just how much effect I would notice if I burned some of my new AAC files to CD, and then reimported them.
The original files were AAC at 128K, from the iTunes music store (a couple of Tori Amos cuts, and one Suzanne Vega). I burned these files to CD to get them into uncompressed form, then reimported from the CD using AAC at 192K -- choosing a higher bit rate than the originals in hopes of reducing the impact of an extra compression cycle.
If you want to be sure if this reduces the quality of your sound, you can do this (If you have time to spare, that is):
1. burn original AAC to disc
2. Import song again
3. Burn imported AAC to disc
4. repeat step 2 and 4 lots of times, and listen to the difference.
You should use a CD-RW for this task, not to use lots of CDs. If you do this say, 10 times and still cannot hear anything significant, then theres not too much to loose from this, if you can hear a significant difference, then you know it degrades it each time.
Still you can burn your AAC files straight to CD. This will use one of the three legal copies of the song, but as long as you have that CD, you can still copy THIS music any computer (Since CDs are read only, once they are burned. Theres no way of updating the watermark on the songs on the CD-R).
.:BoeManE-_
Originally posted by BoeManE
If you do this say, 10 times and still cannot hear anything significant, then theres not too much to loose from this, if you can hear a significant difference, then you know it degrades it each time.
There's no question that if you encode and re-encode enough times (or even once) you'll lose information. The question is only if the loss from ONE re-encoding is noticable. Because once you've done it once, there's no need to ever do it again. You can make unlimited perfect digital copies of the re-encoded, DRM-free file.
Still you can burn your AAC files straight to CD. This will use one of the three legal copies of the song, but as long as you have that CD, you can still copy THIS music any computer (Since CDs are read only, once they are burned. Theres no way of updating the watermark on the songs on the CD-R).
Keep in mind that AFAWK Apple doesn't limit the number of copies of the file you can have, only the number of computers you can play it on. You can also burn an unlimited number of regular audio (AIFF) CDs (which can play anywhere, anytime, and seen to be completely DRM-free) from your downloaded tracks, as well as making backup CDs of the AAC files. Shetline was talking about burning the music as DRM-free AIFF then re-encoding the burned AIFF as DRM-free AAC.
Originally posted by BoeManE
Still you can burn your AAC files straight to CD. This will use one of the three legal copies of the song, but as long as you have that CD, you can still copy THIS music any computer (Since CDs are read only, once they are burned. Theres no way of updating the watermark on the songs on the CD-R).
you have unlimited burns... it does not count as "one of the three" that only refers to the number of versions of iTunes you can play the song on... and it doesn't matter how it gets there either (as long as you don't change the format)... iTunes has to be "authorized" from the iTMS to play any protected songs and only 3 computers can be authorized at any given time...
Originally posted by Paul
you have unlimited burns... it does not count as "one of the three" that only refers to the number of versions of iTunes you can play the song on... and it doesn't matter how it gets there either (as long as you don't change the format)... iTunes has to be "authorized" from the iTMS to play any protected songs and only 3 computers can be authorized at any given time...
Ah, that changes things. I thought the DRM was stored within the song itself. But it makes more sense to do it like that.
Originally posted by Towel
There's no question that if you encode and re-encode enough times (or even once) you'll lose information. The question is only if the loss from ONE re-encoding is noticable. Because once you've done it once, there's no need to ever do it again. You can make unlimited perfect digital copies of the re-encoded, DRM-free file.
Anyways, what I was saying, is that even though there are a reduction to the sound quality per encode/decode cycle, if you do it 10 ogr 15 times and still cant hear a noticable difference, then there shouldnt be a problem with doing this once. But if you can hear a difference while doing this 10, or even 5 times you know that you loose a lot of information when you decode/encode once.
I didnt try to imply that the encode/decode could be done without losing any information. (Allthough it might have sounded that way
Originally posted by tonton
Good news! You don't have to burn to CD to convert to AIF anymore. Just use Toast Titanium.
Article on iPoding
tonton, you just made my day. Thanks.
Originally posted by tonton
Good news! You don't have to burn to CD to convert to AIF anymore. Just use Toast Titanium.
Article on iPoding
Okay, this is a good start, but what if I want to turn the AIFF file back into AAC? I can use a program like Amadeus to load an AIFF file and save it as MP3, but how do I do AIFF -> AAC? QuickTime Pro? Some free option?
Originally posted by tonton
iTunes
Can you elaborate? I'm not sure how to use iTunes to turn an AIFF file into AAC. I tried "Import" in the file menu, but that wouldn't let me select an AIFF file.
Originally posted by Towel
Keep in mind that AFAWK Apple doesn't limit the number of copies of the file you can have, only the number of computers you can play it on.
So if there's no limit to how many copies of a file you can have, how does iTunes on one computer know what the iTunes on a different computer is doing? For instance, if I have a particular track on three machines at work, but then bring a fourth copy home, how does my copy of iTunes know that I've already blown my "3 times" allocation at work?
Is it like Sony's MagicGate tech. where you have to continually book the files in and out? Each time you "authorise" a computer, does it automatically alter all of the copies of a track that you might have?
I don't understand! My head hurts!
Originally posted by Paul
you have unlimited burns... it does not count as "one of the three" that only refers to the number of versions of iTunes you can play the song on... and it doesn't matter how it gets there either (as long as you don't change the format)... iTunes has to be "authorized" from the iTMS to play any protected songs and only 3 computers can be authorized at any given time...
Originally posted by Messiah
So if there's no limit to how many copies of a file you can have, how does iTunes on one computer know what the iTunes on a different computer is doing? For instance, if I have a particular track on three machines at work, but then bring a fourth copy home, how does my copy of iTunes know that I've already blown my "3 times" allocation at work?
Is it like Sony's MagicGate tech. where you have to continually book the files in and out? Each time you "authorise" a computer, does it automatically alter all of the copies of a track that you might have?
I don't understand! My head hurts!
i believe some type of personal identifier is used on the files. each copy of iTunes doesn't really "know" what the others are doing. it just knows that it is authorized to play that file. the only way a copy of iTunes knows that's it's authorized is by being authorized by the ITMS. the ITMS handles which machines are/aren't authorized.
i hope that makes sense.
Originally posted by tonton
So without an active internet connection, it's impossible to authorize iTunes to play a particular file?
i believe so. but iTunes only needs to be authorized once, not for every single file.
Originally posted by tonton
Good news! You don't have to burn to CD to convert to AIF anymore. Just use Toast Titanium.
Article on iPoding
Actually, you shouldn't even need toast. In iTunes, if you change the import settings to AIFF, and then select a song from your library, you should be able to go to the Advanced menu and see an option to 'Convert Song to AIFF'
Originally posted by agent302
Actually, you shouldn't even need toast. In iTunes, if you change the import settings to AIFF, and then select a song from your library, you should be able to go to the Advanced menu and see an option to 'Convert Song to AIFF'
not with protected AAC, which is the point...
Originally posted by Paul
not with protected AAC, which is the point...
Figured there was a catch. My mistake.