MP3 compression question

Discussion in 'Mac Apps and Mac App Store' started by believo, Nov 23, 2004.

  1. believo macrumors regular


    May 21, 2004
    Los Angeles, CA
    when you have an MP3 file and you convert it to AIFF or burn it as a track on a CD does this then improve the quality or is it still lack the quality that the MP3 lacked?
  2. Maxicek macrumors regular

    Apr 23, 2004
    Recompressing it to AAC is likely to make the quality worse - lossy compression format over lossy compression format. Leave it as MP3.

    I think that burning to CD will keep the same quality. It certainly shouldn't make it any worse. I'm not sure it will get any better though.
  3. johnnyjibbs macrumors 68030


    Sep 18, 2003
    London, UK
    When you convert a sound/music file to MP3, you are compressing it to approx 1/10th of its size, hence you are losing quality (but quality is better than 1/10th that of the original AIFF file).

    Because you have lost the quality information from the original file in order to save space, you can never recall that quality again from that MP3.

    What this means is that if you burn a CD or convert back to a lossless format like AIFF, you are increasing the file size again to 10 times that amount but the quality will remain EXACTLY the same as the MP3. (Therefore, while burning a CD is done practical purposes, there is no advantage whatsoever in converting an MP3 file into an AIFF file to listen to in iTunes as it is the same quality as the MP3 but takes up much more space.)

    If you convert the MP3 (or MP3 converted back to AIFF or burnt to a CD) back into MP3 or AAC or WMA, the quality will get worse because you are now compressing the already compressed file a second time.

    The same applies to any compressed audio file - like AAC or WMA too.
  4. pianojoe macrumors 6502


    Jul 5, 2001
    N 49.50121 E008.54558
    Johnny is practically right. When you listen to MP3 music on your computer, core audio decompresses the audio stream (into something very AIFF-like) and hands it to the audio output. Since the MP3 is being converted to an uncompressed format anyway en route to your ear, there will be no audible difference to creating an AIFF first, and listening to that AIFF in a 2nd step.

    However, if we had a d/a converter that was capable of creating an analog output directly from the MP3 (without converting to an uncompressed audio stream first), there would be a slight difference. But this might very well be beyond human audible perception.

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