Lossless encoder

Discussion in 'Mac Apps and Mac App Store' started by jeffy.dee-lux, May 13, 2004.

  1. jeffy.dee-lux macrumors 6502a

    Joined:
    Nov 19, 2003
    Location:
    montreal
    #1
    does anyone have any clue as to how the Apple Lossless encoder, which seems to have an average of about 600kbps or so, rips cds at about 8x while i can only encode mp3s at 160kbs at about 3x or 4x?
    Doesn't make all that much sense to me. I guess maybe the more you compress the data, the more time it takes or something?
    I was pretty disappointed that burnt cd's still have a tiny gap in between tracks, its very distracting for some albums.
    of course i suppose i could just pay for the music i wanna listen to...
     
  2. kgarner macrumors 68000

    kgarner

    Joined:
    Jan 28, 2004
    Location:
    Utah
    #3
    Having looked through most of the referenced thread and not seeing an answer to your question, I figured I would put in my semi-educated guess. I think that the rip speed is higher for the lossless codec because the CPU does not have to compress as much information so it should do it faster. Like I said, this is only a semi-educated guess, but it makes sense to my feeble mind.
     
  3. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #4
    As the original poster guessed, the speed of the rip is determined almost entirely by how fast your computer can process the uncompressed audio it's sucking in from the CD drive. Assuming that you've got a 16X or 24X CD drive, and your hard drive is capable of around 10MB/s (almost all are), the computer can read faster than the processor can probably handle data, and it can definitely write what it processes as fast as it needs to.

    So, the answer to the question is simply that whatever lossless compression scheme Apple is using must not be very processor intensive, whereas MP3 and AAC are. This isn't really surprising, since the lossless scheme probably isn't doing anything wildly tricky to trim out some repetitive bits, while the more sophistocated lossy schemes do all kinds of fancy processing tricks to squeeze sound without too much noticible loss.


    For reference, using a G4 1000DP Power Mac on an on-hard-drive MP3 file:
    160K AAC: 20 sec (11X; iTunes reported about 12X)
    160K MP3: 18 sec (12.5X; iTunes reported about 14X)
    Lossless: 8 sec (28X)

    I remember back in the 68k days when you could decompress an MP3 into uncompressed audio, but it took something like 2 hours per minute of audio. Compared to the miserable quality of .au files and the size of an AIFF, MP3 seemed like magic back then.
     

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