aif/mp3 tif/jpg is this analogy valid on more than a superficial level?

Discussion in 'Digital Audio' started by dogbone, Jul 22, 2006.

  1. dogbone macrumors 68020

    dogbone

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    #1
    I know from experience that if I have a high quality jpg that I can convert it to a tif and back to a low res jpg without really suffering any discernable artifact intrusion.

    I'm wondering if the same holds true for aif/mp3.

    You see I've got a bunch of low quality (recorded) talks, lots of boominess and background rumble. Some are in aiff but some are in high quality mp3, (that's high quality but crap recording).

    If the analogy holds true it would suggest that I could convert the mp3 to aiff by importing into garageband (or audacity) and try to improve the sound then export an aiff and try to crush it down to a small mp3.

    I know it's better to leave it as an aiff all the way through till the end but i'm wondering if pulling a 160kbps mp3 into GB then converting to a 32kbps mp3 is going to be that much worse than if it was an aiff to begin with yet badly recorded.

    I'm not certain that I've made myself clear but I hope so :)
     
  2. zimv20 macrumors 601

    zimv20

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    #2
    converting an mp3 to an aiff and then back to an mp3 will gain you nothing.

    however, if you're doing operations on the audio file, there may be some benefit to, say, doing those operations on a 96/24 file, rather than a 44/16 one. but i wouldn't expect any benefit to be pronounced, especially if you're just rolling off the low end. boominess is a record-time issue.

    btw, if that 160 kbps mp3 is in mono, that's pretty decent quality, imo -- the same as 320 stereo. once i start encoding mp3s at 256 kbps stereo, i can no longer differentiate between that and the original source. at least i can't on my monitoring system.
     
  3. dogbone thread starter macrumors 68020

    dogbone

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    #3
    Yeah I know the recording at 160kbps is good quality, as a faithful reproduction of something that has been recorded badly.

    But what I need to do is compress these files by at least a factor of 4. I only mentioned converting to aiff because I thought that is what garageband does when you import an mp3.

    I want to import into gb to see if I can apply some of the filters to improve the sound quality. These are just talks. then when I've got it as good as I can, instead of saving it as a big size file, I want to make it about a quarter of the size say about 32kbps.

    Now I know I can do this with an image. I can bring in a bad scan that is a hi res jpg and work on it in photoshop then save it at probably 1/5 the size of the original jpg and it will be quite good. But is this how it works with compressed audio?
     
  4. zimv20 macrumors 601

    zimv20

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    #4
    i find analogies between audio and visual to always be a bit flawed.

    any filter/plug-in processing aside, let's consider these two workflows:
    1. 160 kbps mp3 -> aiff -> 32 kbps mp3
    2. 160 kbps mp3 -> 32 kpbs mp3

    i would expect the two resultant files to be the same.

    regarding GB doing everything internally as AIFF, i don't know. pro tools does, fwiw. i record at 24-bit and do my operations (which take place at higher bitrates) before dithering down to 16-bit. imo, this does produce better results than starting off at 16-bit.
     
  5. dogbone thread starter macrumors 68020

    dogbone

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    #5
    OK that's good so far. Now to stretch it a bit further.

    Let's say my original bad quality scan that I needed to fix in photoshop was a tiff file rather than a high quality jpg to begin with. Now I know from experience that my final result would have been the same whether I started with a high quality jpg or a tif, can I say the same with audio? And instead of a bad scan I start with a bad recording?
     
  6. zimv20 macrumors 601

    zimv20

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    #6
    the visual analogue analogy is only confusing me :)

    given the choice of a bad recording at full resolution vs. the same bad recording in a lossy format, i'd take the full resolution. not that it would make much difference.

    i've lost track of what you're asking, i think. you have bad lossy recordings, and you want to treat them and make them even smaller. if GB converts them to aiff regardless, what choice of workflow do you have? you're going to put them in GB, roll off the low end, then bounce down to a low bitrate lossy mp3.

    was there something else you were considering? if not, do the work and see what you get.
     
  7. dogbone thread starter macrumors 68020

    dogbone

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    #7
    It's like this, I'm being sent these files through skype. So if it makes no difference whether I get a 50mb mp3 or a huge fracking aif, I'd go for the mp3 but if this was no good then I'd have to insist on aifs.
     
  8. zimv20 macrumors 601

    zimv20

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    #8
    i would get the same file in the two formats and do a test.
     

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