How Does mp3 Compression Work?

Discussion in 'Tracking / Mixing / Editing' started by agreatheight, Feb 8, 2010.

  1. agreatheight

    agreatheight Guest

    Mods - feel free to move this if there is a better spot for it.

    I am in a situation where I may need to edit mp3 audio. I have a video background and know that if I have a piece of video that has been compressed, and I edit it and save it the compressing is being applied a second time and will often look worse and/or contain artifacts. Does mp3 compression work this way? I doesn't seem to, or maybe I just can't tell. I did a test where I opened an mp3, and pasted in new info and saved it. I reopened it and repeated this action 10 times. It didn't seem to cause any noticeable differences, from the initial piece to the last one pasted in. Could I simply not discern the difference, or does mp3 compression work a different way?

    Thanks!
     
  2. Boswell

    Boswell Moderator Distinguished Member

    Creating MP3s is a destructive process. Opening MP3s in a standard wave editor de-compresses them to PCM (as used in .wav format). If you edit the track and re-save it as MP3, it will compress them again. Whether you can hear this difference after 1 or 10 passes depends on how good your ears, gear and listening environment are.

    Be aware that some wave editors keep a copy of every project in uncompressed form, and simply re-opening the last file saved may just re-open the un-compressed project, and not unpack the MP3.
     
  3. AudioGaff

    AudioGaff Well-Known Member

    Open ended question, so I can't help myself.

    If you have ever heard the results of MP3 compared it to the raw recording you would find that it works pretty crappy no matter how it is used. Sure it squeezes the file size. But file size should not dicate audio quality.
     

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