How much audio quality is lost converting 320kbps MP3 to 128kbps AAC?

Discussion in 'iPhone' started by kuykee, Feb 18, 2013.

  1. macrumors newbie

    Joined:
    May 20, 2010
    #1
    How much audio quality is lost converting 320kbps MP3 to 128kbps AAC?

    I'd like to know so that I can store more files on my iPhone and iPod classic (also to make the iPod classic hard drive spin less). Also to save space on my Macbook hard disk
     
  2. macrumors 68030

    basesloaded190

    Joined:
    Oct 16, 2007
    Location:
    Wisconsin
    #2
    My guess would be that it depends on what kind of headphones you are using. If you are using something along the lines of Apple's earphones, my guess would be not that much. But if you have a $200+ set you might notice the decrease in quality.
     
  3. macrumors 6502a

    jamesjingyi

    Joined:
    Dec 20, 2011
    Location:
    UK
    #3
    Why not test it out yourself

    Oh and why not try iTunes Match... Then nothing is on your MB at all and your Classic is fine!
     
  4. macrumors 6502a

    Joined:
    Jul 29, 2007
    #4
    I use 192kpps compression when syncing my IPhone with ITunes. Best trade off in quality vs size for me. Your listening environment is more important than compression for sound quality.
     
  5. macrumors 603

    scaredpoet

    Joined:
    Apr 6, 2007
    #5
    there is an option to down convert to 128kbps when syncing to iPods and iOS devices, so you might want to try that. If you don't like it, you can just uncheck the box and resync.
     
  6. macrumors 603

    Interstella5555

    Joined:
    Jun 30, 2008
    #6
    192kbps?
     
  7. macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    上海 (Shanghai)
    #7
    Why would you buy a classic to save space? :confused:


    The loss in quality cannot be quantified. You need to physically listen to each song, and it's possible if you have poor headphones, or even a bad hearing, you can't tell the difference.
     
  8. macrumors demi-god

    xraydoc

    Joined:
    Oct 9, 2005
    Location:
    192.168.1.1
    #8
    On good equipment you will almost certainly hear a difference. How much it bothers you is what matters most.
     
  9. macrumors 6502

    Joined:
    Sep 13, 2010
    #9
    It won't be nearly as bad as converting MP3 to MP3 using LAME, which can produce obvious artifacts after just one generation of transcoding. In fact, high bitrate MP3 to AAC will probably be pretty good. Let your ears be the judge, but please perform valid comparisons using foobar2000's ABX comparator or similar. There are apps that will let you do the comparison right on the Touch.
     
  10. macrumors G5

    gnasher729

    Joined:
    Nov 25, 2005
    #10
    Plug in your iPod. In iTunes, click on the iPod. Click on "Summary", and "Convert higher bitrate to 128KBit". That option is non-destructive. Nothing on your hard drive is changed, so you don't have to worry about any loss. iTunes converts the music while it gets downloaded to the iPod. If you don't like it, you just change the option. I cannot distinguish AAC 192KBit from originals. 128KBit loses something. It's not the same.
     
  11. thread starter macrumors newbie

    Joined:
    May 20, 2010
    #11
    foobar2000 comparator looked interesting, but it's still only listening by ear according to this video http://www.youtube.com/watch?v=jt7GyFW4hOI

    Is there something else that can give you a graph or more statistical view of what is being lost from or changed in the file or in which parts there have been changes?
     
  12. macrumors 65816

    Joined:
    Jul 23, 2012
    #12
    depends on what earbuds/headphones you're using and how good your hearing is. Personally, I would never rip in 128 because it sounds so awful.
     
  13. JAT
    macrumors 603

    Joined:
    Dec 31, 2001
    Location:
    Mpls, MN
    #13
    This question and discussion has been ongoing since the 70s. (only the formats have changed) Good luck on receiving an answer.
     
  14. macrumors 6502

    Joined:
    Sep 13, 2010
    #14
    Viewing things like waveform difference files is not particularly relevant. The only thing that matters is your own subjective perception and performing a valid blind test. Besides using foobar ABX or equivalent, the two files to be compared must be derived from the same mastering, and preferably the exact same source (one from the other obviously counts); otherwise, you may be testing for differences in mastering, not encoding, and differences in mastering can be genuinely profound and trivial for anyone to ABX.

    There is an infinite amount of nonsense in discussions about these things. Here is a fairly detailed slideshow of a scholarly presentation that used high-end equipment under ideal conditions:

    http://www.music.mcgill.ca/~hockman/documents/Pras_presentation2009.pdf

    Its conclusion were:

    • Trained listeners can hear differences between CD quality and mp3 compression (96-192 kb/s) and prefer CD quality.
    • Trained listeners can not discriminate between CD quality and mp3 compression (256-320 kb/s) while expert listeners could.
    • Ability to discriminate depends on listeners’ expertise and musical genre.
    • Artifacts can be verbalized and do not depend on musical genre.

    I think AAC is a lot better than MP3 at low bitrates, judging by my threshold for hearing artifacts in various "killer samples", which disappear for me at AAC 128 Kbps but persist in LAME 3.98 MP3 up to 192 Kbps and a little beyond. I've also found transcoding high bitrate MP3s to AAC to be much more transparent than going MP3->MP3, which introduces obvious artifacts after one generation. If you want to read a lot of subjective crazy talk including things like cable directionality, try the stevehoffman.tv forums. For people who value blind listening tests, try hydrogenaudio.org.
     
  15. macrumors 6502a

    Joined:
    Nov 2, 2008
    #15
    For me, where I listen to my iPhone, I don't see that it matters. In my truck, there is enough wind noise that I don't notice.
     
  16. macrumors member

    Joined:
    Mar 17, 2011
    #16
    8.4% i spent 4 months studying this
     

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