MP3 to AAC at same bitrate - worth it?

Discussion in 'Mac Basics and Help' started by nope7308, Sep 29, 2013.

  1. nope7308 macrumors 65816

    nope7308

    Joined:
    Oct 6, 2008
    Location:
    Ontario, Canada
    #1
    I'm trying to decide if I should convert my entire iTunes library from MP3 (@320kbps) to AAC (@320kbps).

    There's two motivations for this:
    - Better sound quality
    - Less HDD space

    AAC is supposed to be better for sound quality, but is that true when you convert from an existing MP3 file, keeping the same bitrate? I'm worried that converting one compressed file format to another might further degrade the original "copy", and therefore the overall sound quality. Can someone please clarify?

    Also, assuming I have about 30GB of music in MP3 format, how much space can I reasonably expect to save if I convert all of it to AAC? Again, I would keep the same 320kbps bitrate.

    I have an iPhone, iPod, and iPad, so compatibility isn't an issue. I'm only concerned with (1) audio quality, and (2) space requirements.

    Thanks!
     
  2. jon3543, Sep 29, 2013
    Last edited: Sep 29, 2013

    jon3543 macrumors 6502

    Joined:
    Sep 13, 2010
    #2
    You would not save any space staying at the same bitrate, and you can only degrade quality when you encode to a lossy format. Transcoding lossy to lossy stands to multiply the problems.

    That said, if you must transcode higher bitrate lossy to a lower bitrate to save space, AAC is much better about preserving quality than MP3. I have iTunes convert everything larger than 128 to 128 Kbps AAC when syncing to my Touch, and even the MP3 tracks still sound good. That would not be the case if, say, LAME had been used to convert higher bitrate MP3 to 128 Kbps. I did that experiment on my computer with LAME 3.98, and it introduced obvious artifacts right away in real content. Not so for AAC. For lossless content, AAC is still a lot better than LAME, and it's easy for me to tell them apart, particularly with "killer samples", some of which cause artifacts all the way to 192 Kbps with LAME, while they're pretty much clean even at 128 Kbps AAC. YMMV. Whatever you do, please perform proper blind tests using software like foobar2000's ABX comparator.
     
  3. nope7308 thread starter macrumors 65816

    nope7308

    Joined:
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    Location:
    Ontario, Canada
    #3
    Ah, so my fear of lossy to lossy was well founded. I think you're wrong about the space saving, though. All things being equal, an AAC file uses less space than an MP3 file, even when ripped at the same bitrate. I know that much is true. What I don't know is if that's true when converting from MP3 to AAC.

    That brings up a new question...

    What will sound better - my existing 320 kbps MP3 files (ripped from CD/Lossless)... OR ...256kbps AAC files through iTunes matching program?

    I'd really like to save space, so this might be a viable option. It would do all of the conversions for me, it would legitimize a great portion of my library (lol), and I wouldn't have to correct metadata tags and whatnot. I don't mind forking over the $20 or whatever it costs, provided it doesn't reduce the sound quality. Can you (or anyone else) confirm this?

    Thoughts?
     
  4. jon3543 macrumors 6502

    Joined:
    Sep 13, 2010
    #4
    I guess it's possible, but I wouldn't expect a huge difference. I just tried it on a lossless file, and the 320 Kbps AAC version was actually .9% larger than the 320 Kbps MP3.

    Assuming they were mastered from the same lossless source, I'd expect them to be indistinguishable, but see what I wrote about valid comparisons in my last message. The tricky thing is always, "What is the source?" A great deal of music has undergone remastering, and it often comes out worse due to dynamic range compression and re-eq'ing. So two lossless versions of the (nominally) same recording can sound very different. More rarely, albums are released with different versions of the songs (ZZ Top and Ozzy Osbourne come to mind).
     
  5. nope7308 thread starter macrumors 65816

    nope7308

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    Ontario, Canada
    #5
    But that's just my question - would it be the same source? I ripped my files from CD, whereas I presume Apple would use the digital master copy?

    Also, does iTunes Match not update the metadata? I have so many files from all over the place that I want the metadata to be synced with what's in the iTunes store. Compilations are all over the place and it's difficult to keep track. If iTunes match doesn't do this, then that's a deal-breaker for me. I can't believe Apple wouldn't give you the option, but then again, it's Apple...
     
  6. apunkrockmonk macrumors 6502a

    apunkrockmonk

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    Location:
    Rochester, NY
    #6
    iTunes Match leaves your metadata intact.

    The reasoning behind this is most likely music obtained by legitimate means should have good metadata already.
     
  7. nope7308, Sep 29, 2013
    Last edited: Sep 29, 2013

    nope7308 thread starter macrumors 65816

    nope7308

    Joined:
    Oct 6, 2008
    Location:
    Ontario, Canada
    #7
    Not that it matters, but I don't buy that argument. There's a number of legitimate reasons to want to sync metadata. For instance, I used to manually remove/edit the genre listing for some albums because the genre would be different even though the artist would remain the same (created some issues when I sorted/browsed based on genre). I now see the error of my ways, but I don't want to sift through 30GB+ of music just to fix that.

    And yes, pirated music usually has inaccurate metadata, but isn't that the target audience for iTunes Match in the first place? You know, the people that want to legitimize their music library, and download decent quality files?

    I mean, how hard would it be to actually give customers the option to update metadata? Not giving us the option is just a pain in the ass; it doesn't do anything to curb illegal downloading.
     
  8. jon3543 macrumors 6502

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    Sep 13, 2010
    #8
    I don't think there's any way to know what you're going to get. This is a major reason some people will only buy CDs, to know which mastering they're getting. Though I hesitate to mention it due to the crackpottery that reigns over much of the site, people talk endlessly about different masterings at:

    http://forums.stevehoffman.tv
     
  9. Fishrrman macrumors G4

    Joined:
    Feb 20, 2009
    #9
    [[ I'm trying to decide if I should convert my entire iTunes library from MP3 (@320kbps) to AAC (@320kbps).
    AAC is supposed to be better for sound quality, but is that true when you convert from an existing MP3 file, keeping the same bitrate? I'm worried that converting one compressed file format to another might further degrade the original "copy", and therefore the overall sound quality. Can someone please clarify? ]]

    You will gain NOTHING (shouting intentional).

    Mp3 is already a "lossy" compression scheme. You cannot expect to hear anything more after a "conversion" than you heard before it -- because the conversion process cannot "recover fidelity" that has already been lost through the original compression process.

    My advice:
    A 320kbps bitrate for mp3 is already about as good as it gets for the mp3 format. In most listening situations, you aren't going to hear much of a difference between an mp3 at that bitrate and "uncompressed" (remember, I said in _most_ situations, not all).

    Stick with mp3 -- it's the more "open" format, no DRM to mess with, playable anywhere.
     

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