Changing MPEG's to AAC. Any Advantages?

[mileslong]

or possible any disadvantages to doing this? does AAC have a better sound quality? im thinking about doing this with my entire itunes catalog but i dont want to waste my time if it doesnt really do anything. thanks in advance!

[Lacero]

Only to save space.

I'll convert any MP3 over 192 Kbps to 128 Kbps AAC. But anything under 192 Kbps MP3, I'll just leave it alone.

Here's to the Crazy Ones http://forums.macrumors.com/attachment.php?attachmentid=35452 (http://www.uriah.com/apple-qt/movies/think-different.mov)

[mileslong]

thanks for the reply lacero, why is 192kbps a magic number for you? also, what if space is not a concern for me? i always try and get the highest kbps i can get per song...

does AAC take up less space than mp3?

[PlaceofDis]

AAC does take up slightly less space. converting music though will degrade quality a little though. try converting some tracks and see how they sound before you stick with it. personally i try and keep everything above 192 AAC or MP3. lower sounds crappy to me. but everyone has different ears.

[Lacero]

Most songs ripped from CD I encode at 320 Kbps, add album art, full tags, etc, and then I archive it. Space isn't a concern with me too, but once the collection starts going into tens of thousands of songs, it makes sense to keep them as small as possible. I make a 128 Kbps AAC version for general listening on iPods.

192 Kbps is a good sacrifice for MP3 song quality and size. At 256 Kbps for instance, the file size is double that of 128 Kbps but song quality isn't twice as good. At most, maybe a 2-5% subjective noticeable improvement. But given the environments in which songs are played (treadmills, sidewalks, car interiors, etc) the added quality of 256 Kbps gets lost in background noise of everyday life.

AAC is a more efficient codec than MP3 so 128 Kbps AAC is roughly equivalent to 192 Kbps MP3.

But even 128 Kbps MP3 isn't that bad, either (http://www.dplay.com/dv/mp3test/).

Looks like ALS (MPEG-4 Audio Lossless Codec) will supplant AAC in the near future.

Here's to the Crazy Ones http://forums.macrumors.com/attachment.php?attachmentid=35452 (http://www.uriah.com/apple-qt/movies/think-different.mov)

[howesey]

Most songs ripped from CD I encode at 320 Kbps, add album art, full tags, etc, and then I archive it. Space isn't a concern with me too, but once the collection starts going into tens of thousands of songs, it makes sense to keep them as small as possible. I make a 128 Kbps AAC version for general listening on iPods.

192 Kbps is a good sacrifice for MP3 song quality and size. At 256 Kbps for instance, the file size is double that of 128 Kbps but song quality isn't twice as good. At most, maybe a 2-5% subjective noticeable improvement. But given the environments in which songs are played (treadmills, sidewalks, car interiors, etc) the added quality of 256 Kbps gets lost in background noise of everyday life.

AAC is a more efficient codec than MP3 so 128 Kbps AAC is roughly equivalent to 192 Kbps MP3.

But even 128 Kbps MP3 isn't that bad, either (http://www.dplay.com/dv/mp3test/).

Looks like ALS (MPEG-4 Audio Lossless Codec) will supplant AAC in the near future.

Here's to the Crazy Ones http://forums.macrumors.com/attachment.php?attachmentid=35452 (http://www.uriah.com/apple-qt/movies/think-different.mov)
How do you measure "2 - 5%"?

[CanadaRAM]

They key concept is that once they are MP3 encoded, there is NOTHING you can do to recover the sound quality that has been traded away for compression. Re-encoding an MP3 as anything else can only degrade it further, no matter the quality of the 2nd codec.

The only way to get better quality is to go back to high quality original source material and encode again,

[balamw]

Looks like ALS (MPEG-4 Audio Lossless Codec) will supplant AAC in the near future.

:confused: What makes you think that? ALS is potentially poised to supplant FLAC/Apple Lossless/Monkey's Audio. Just like those lossless codecs it offers something like 700 kbps bitrates i.e. still more than double the file size of your 320 kbps archival MP3s.

AFAIK The only real competition for AAC as we know it in iTunes, a.k.a AAC-LC is aacPlus/HE-AAC, which might enable bitrates below 128 kbps. http://en.wikipedia.org/wiki/MPEG-4_Part_3

B

[jmufellow]

Re-encoding an MP3 as anything else can only degrade it further, no matter the quality of the 2nd codec.
Except when you go from a compressed file (mp3 aac) to uncompressed (WAV AIFF). Tho I don't know who in their right mind would do that. Correct me if I'm wrong...

[balamw]

Except when you go from a compressed file (mp3 aac) to uncompressed (WAV AIFF). Tho I don't know who in their right mind would do that. Correct me if I'm wrong...
It's a decent way to archive iTMS purchased tracks. Burn a playlist using iTunes and re-rip in Apple Lossless.

B

[howesey]

Here's one for you...

Even a copied CD of the original doesn't sound the same.

Make a copy, listen to both in a good hi-fi, and come back to us. I have tested this on many people, this includes people who do not have a trained ears, and they always pick out the copied CD.

[Blue Velvet]

Here's one for you...

Even a copied CD of the original doesn't sound the same.

Make a copy, listen to both in a good hi-fi, and come back to us. I have tested this on many people, this includes people who do not have a trained ears, and they always pick out the copied CD.


Now that I find hard to believe. Particularly if the copy is burned at a slow speed to reduce any jitter or other burning errors. I can't see why a byte-for-byte copy should sound any different at all, especially in blind tests.

[Lacero]

Except when you go from a compressed file (mp3 aac) to uncompressed (WAV AIFF). Tho I don't know who in their right mind would do that. Correct me if I'm wrong...
People who want to circumvent the DRM so they can use the AIFF in programs like Final Cut Pro.

I don't buy much from iTMS simply because all devices, other than the iPod, do not support AAC. Unless Apple licenses Fairplay to audio car deck and home stereo manufacturers, I'm a bit apprehensive of buying solely from iTMS.

Here's to the Crazy Ones http://forums.macrumors.com/attachment.php?attachmentid=35452 (http://www.uriah.com/apple-qt/movies/think-different.mov)

[bousozoku]

Except when you go from a compressed file (mp3 aac) to uncompressed (WAV AIFF). Tho I don't know who in their right mind would do that. Correct me if I'm wrong...

As long as the mp3 or AAC decoder doesn't mangle bits, that's a good assumption. Then, the WAV or AIFF encoder has a clean image with which to work. Any time, you re-encode rather than re-rip, you can assume degradation of the original information.

Personally, I'm waiting for mp3 pro to take hold but it's been a while coming for several enhanced codecs to hit the mainstream. Better sound with smaller file sizes are a reality but of course, there is no iTunes support for it. I'm still okay with my 256 Kbps VBR mp3 files but having them in nearly half the size would be much better.

[Counterfit]

Now that I find hard to believe. Particularly if the copy is burned at a slow speed to reduce any jitter or other burning errors. I can't see why a byte-for-byte copy should sound any different at all, especially in blind tests.
http://forums.macrumors.com/showthread.php?t=159036

[devman]

Here's one for you...

Even a copied CD of the original doesn't sound the same.

Make a copy, listen to both in a good hi-fi, and come back to us. I have tested this on many people, this includes people who do not have a trained ears, and they always pick out the copied CD.

How are you making the copy?

[balamw]

Now that I find hard to believe. Particularly if the copy is burned at a slow speed to reduce any jitter or other burning errors. I can't see why a byte-for-byte copy should sound any different at all, especially in blind tests.
Only one other thing I could imagine as being a potential issue here is that the "high end" CD player might not support burnable media properly and thus introduces more errors on playback of the copy.

One possible way to check if it's generational loss would be to copy the original to copy #1, copy copy #1 to copy #2, copy copy #2 to copy #3, etc...Do this about 10 times and compare copy #1 to copy #10.

B

[rasp]

or possible any disadvantages to doing this? does AAC have a better sound quality? im thinking about doing this with my entire itunes catalog but i dont want to waste my time if it doesnt really do anything. thanks in advance!


If you mean transcoding from mp3 to aac, you will gain nothing in sound quailty, all the properties of the mp3 encoding will remain, and you will gain the added noise of aac. In practical application, I don't here any terrible side effect of one conversion, but I usually listen in my car or walking or other high noise area.

I usually buy cd's so I can encode them how I like, and if I need to, can rip them again. For the ipod I just use 128k aac, sounds good enough to me.

[Frungi]

Back to the original question…
Changing MPEG's to AAC. Any Advantages? or possible any disadvantages to doing this? does AAC have a better sound quality? im thinking about doing this with my entire itunes catalog but i dont want to waste my time if it doesnt really do anything. thanks in advance!
No. No advantages. MP3 and AAC are both lossy formats—anything you encode in either of them will lose at least some quality. If you convert from one lossy format to another, then you’ve lost quality twice. Apple claims AAC is more efficient than MP3 (i.e. 128kbps AAC sounds as good as 192kbps MP3), so if you want AAC, do NOT convert the MP3s. Re-rip all your CDs to AAC, that’s what I did.