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Jeeves87
Apr 3, 2008, 08:59 PM
I currently have quite a few (~4500) songs in mp3 format in my Itunes of varying bitrates. I was wondering if it would be worth it to convert all of music to 256kbps AAC, will I notice any quality differences?? Can a song sound better after it has been compressed down to 128k MP3 then uncompressed slightly to 256 kbps?? Or would I be wasting my time??

Thanks for any advice, this is my first post on MacRumors.



psychofreak
Apr 3, 2008, 09:00 PM
You would be wasting your time.

Eidorian
Apr 3, 2008, 09:01 PM
Stick with what you already have. I've only made sure to have my personal collection of discs encoded at a high MP3 VBR bitrate since I can't control Amazon or iTunes.

Jeeves87
Apr 3, 2008, 09:02 PM
Thanks for the advice

IJ Reilly
Apr 4, 2008, 10:16 AM
It depends on what you are trying to accomplish, and the quality of the source material. If you're trying to squeeze more songs onto your iPod, then recoding them as AAC gets you more bang for the MB. At any given bitrate, AAC is going to give you better audio quality than MP3. So it might be a waste of time, or not.

telecomm
Apr 4, 2008, 10:29 AM
It depends on what you are trying to accomplish, and the quality of the source material. If you're trying to squeeze more songs onto your iPod, then recoding them as AAC gets you more bang for the MB. At any given bitrate, AAC is going to give you better audio quality than MP3. So it might be a waste of time, or not.

But these songs are already compressed as MP3 files. Transcoding will lower the quality even further, independently of the AAC settings used.

IJ Reilly
Apr 4, 2008, 10:36 AM
But these songs are already compressed as MP3 files. Transcoding will lower the quality even further, independently of the AAC settings used.

So I have heard, but would this would be a significant issue going from, say, 256 bit MP3 to 128 bit AAC? I've done quite a bit of this myself, and haven't heard any significant degradation.

telecomm
Apr 4, 2008, 12:22 PM
So I have heard, but would this would be a significant issue going from, say, 256 bit MP3 to 128 bit AAC? I've done quite a bit of this myself, and haven't heard any significant degradation.

I've never tried this myself; maybe some of the local audio pros will have something to say about this.

At any rate, the OP was interested to know if there would be any sound quality benefits in doing this, and the answer to that is definitely "no."

killmoms
Apr 4, 2008, 12:24 PM
There are never any sound quality benefits to transcoding lossy files to other lossy formats. You can't get back what's been thrown out, ever, without going back to the source.

IJ Reilly
Apr 4, 2008, 12:30 PM
I've never tried this myself; maybe some of the local audio pros will have something to say about this.

At any rate, the OP was interested to know if there would be any sound quality benefits in doing this, and the answer to that is definitely "no."

There are never any sound quality benefits to transcoding lossy files to other lossy formats. You can't get back what's been thrown out, ever, without going back to the source.

Actually, he asked if there would be any "quality difference," which I took to mean loss of audio quality. I realize that you couldn't possibly get any benefit.

zainjetha
Apr 4, 2008, 12:34 PM
Leave them the way they are.

MP3 is more universal as it can go on any player whereas AAC is locked to iTunes...

4500 songs probably isnt alot of music to you..wow

gnasher729
Apr 4, 2008, 05:10 PM
I currently have quite a few (~4500) songs in mp3 format in my Itunes of varying bitrates. I was wondering if it would be worth it to convert all of music to 256kbps AAC, will I notice any quality differences?? Can a song sound better after it has been compressed down to 128k MP3 then uncompressed slightly to 256 kbps?? Or would I be wasting my time??

You would be wasting time, space, and lose quality.

Every time you convert music to any lossy format (that is anything except Apple Lossless, WAV or AIFF) you lose quality. An analogy from old times: You have recorded music on a tape cassette using a cheap tape recorder. If you copy that cassette using a much better recorder, it won't get better. It will get worse. Not by much if you use a very good recorder, but it will get worse.

killmoms
Apr 4, 2008, 05:12 PM
MP3 is more universal as it can go on any player whereas AAC is locked to iTunes...

Not true. There are many software and hardware players which support AAC just fine. Only DRMed AAC files from the iTunes Store are locked to iTunes.

IJ Reilly
Apr 4, 2008, 07:09 PM
You would be wasting time, space, and lose quality.

Every time you convert music to any lossy format (that is anything except Apple Lossless, WAV or AIFF) you lose quality. An analogy from old times: You have recorded music on a tape cassette using a cheap tape recorder. If you copy that cassette using a much better recorder, it won't get better. It will get worse. Not by much if you use a very good recorder, but it will get worse.

You could certainly save space. That would be the reason to do it.

The tape analogy is kind of imperfect. Tape is noisy, so the problem with multiple generation re-recording is an accumulation of noise.

telecomm
Apr 5, 2008, 12:14 PM
Actually, he asked if there would be any "quality difference," which I took to mean loss of audio quality. I realize that you couldn't possibly get any benefit.

I think it's pretty clear killmoms and I were responding to...

Can a song sound better after it has been compressed down to 128k MP3 then uncompressed slightly to 256 kbps?

IJ Reilly
Apr 5, 2008, 01:18 PM
I think it's pretty clear killmoms and I were responding to...

Ah. I did miss that. :o

origbow
Apr 8, 2008, 08:21 PM
Hi,

Just reading about this debate on converting as originally posted. I have a slight variation on this for my question. I currently have imported my music (~1200 songs so far) into iTunes as an MP3 256kbps VBR encoder. Total file storage approx 9.2GB. Using a 4GB iPod Nano 2nd Gen. At the time I started importing, I read that this would allow more options if I ever wanted to move my music away from iTunes (unlikely, but I never say never!). Also, AAC wasn't so common on other MP3 players, whereas now it is. And there was a hot debate about AAC vs MP3 quality too!

Should I convert my MP3 256kbps to AAC or is that just going to downgrade the quality? What about moving my import format to AAC for all future songs so I have a mixture, or will that cause it's own problems? How much file space will I likely gain by switching over to AAC? Any other issues I need to be aware of before deciding? Will appreciate your comments and thoughts on this.

killmoms
Apr 9, 2008, 12:07 PM
Should I convert my MP3 256kbps to AAC or is that just going to downgrade the quality? What about moving my import format to AAC for all future songs so I have a mixture, or will that cause it's own problems? How much file space will I likely gain by switching over to AAC? Any other issues I need to be aware of before deciding? Will appreciate your comments and thoughts on this.

Please, please, PLEASE read the thread before posting. I will reiterate:

Any lossy-to-lossy transcode will result in reduced quality, always, without exception, forevermore, Amen.

Also, 256kbit MP3 will sound better than 128kbit AAC. If you were to convert to, say, 256kbit AAC, you wouldn't save any space at all—kbit = kbit, no matter the codec in question.

In any event, if you already have a lossy library, the only way to go to another format is to re-encode from the original lossless sources (namely CDs). Anything else is a transcode and a bad idea.

macgruder
Apr 9, 2008, 12:27 PM
MP3 is more universal as it can go on any player whereas AAC is locked to iTunes...

Where does this misconception come from I wonder? Do people think that the 'A' stands for 'Apple' or something. AAC is basically MP4, and is probably less legally unencumbered than MP3.

The answer to transcoding is not always straightforward. For example, sometimes when building websites designers will send me 95% JPEGs which are about 400K. Rather than chasing them down, I just 'transcode' to 70% which knocks the size down to less than 50K usually. Now of course the quality is less than the original but it's a lot smaller too, and the difference is pretty difficult to spot.

A 256kbs MP3 is essentially transparent. A 192 kbs AAC is also near enough transparent, and because the methodology of the two systems is different the transcoding will probably not have too much effect. (A 128kbs on the other hand ...). So yes you will lose quality, but it may be not significant depending on your system and your ears, and you would gain a certain amount of space.

That said. Personally, I wouldn't do it, and transcoding from 256 -> 256 is pointless.

killmoms
Apr 9, 2008, 12:30 PM
A 256kbs MP3 is essentially transparent. A 192 kbs AAC is also near enough transparent, and because the methodology of the two systems is different the transcoding will probably not have too much effect. (A 128kbs on the other hand ...). So yes you will lose quality, but it may be not significant depending on your system and your ears.

Perhaps not, but my point is that you are losing MORE quality than you would if you re-encoded from the original source down to 192kbps.

Also, keep in mind that transparency is entirely subjective and depends on a number of factors, including a persons auditory acuity and playback equipment.

macgruder
Apr 9, 2008, 12:52 PM
Perhaps not, but my point is that you are losing MORE quality than you would if you re-encoded from the original source down to 192kbps.

Yes, of course. I agree with you. But if you don't have the original source this is not an option.


Also, keep in mind that transparency is entirely subjective and depends on a number of factors, including a persons auditory acuity and playback equipment.
And mainly on people's imagination :-) My system consists of KEF 4 Reference speakers etc, and I've done a few experiments. Nobody has ever spotted the difference between a 224kbps AAC and the original, and I tend to hang out with musicians. Until I see a double blind study with accurate volume leveling, I'm going to go with the transparency at around 200 - 250. I think it's like the placebo effect. :D

roland.g
Apr 9, 2008, 01:09 PM
If you want to put them in AAC at whatever bitrate you are going to need to reimport them from the original source material. Converting them from MP3 is a waste of time.

zainjetha
Apr 9, 2008, 01:18 PM
You would definitely lose quality, lose your precious life doing it...
You never have to actually see the files themselves in Finder, you use iTunes so it would never bother you... iTunes handles everything so you dont have to worry what format they are in. They will go on your iPod/iPhone/AppleTV so thats all you need to worry about.

Fuchal
Apr 9, 2008, 01:33 PM
You could certainly save space. That would be the reason to do it.

The tape analogy is kind of imperfect. Tape is noisy, so the problem with multiple generation re-recording is an accumulation of noise.

Actually this is pretty similar. MP3 compression is not just a reduction of the frequency. Upon decoding an MP3, psychoacoustics are used to rebuild an approximation of the original sound, which encompass a number of different methods to mask the missing sounds, including noise. Depending on how much was removed depends on how accurately it can recreate the original sound (or really, how much it can convince you you are listening to an unaltered sound).

Converting MP3 to MP3, or MP3 to AAC is not just a further reduction of the bitrate, it's trying to encode the last iteration of the approximation as faithfully as possible, which is already nothing like the original. So, as you continue to transcode, you are quickly drifting further and further away from the original audio. You end up approximating noise with noise repeatedly.

(Whether you can tell the difference is up to your brain and your ears, but the fact is each time you transcode, the resulting file is considerably less like the original.)

IJ Reilly
Apr 9, 2008, 07:35 PM
(Whether you can tell the difference is up to your brain and your ears, but the fact is each time you transcode, the resulting file is considerably less like the original.)

Right, I say let your ears decide. If you can't tell the difference between 256 bit MP3 audio and 128 bit AAC audio transcoded from these files, and your goal is to save space, then it's worth doing. You might want to archive the originals though.