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Logic 9 m4a: aac not in sync!?!

Discussion in 'Logic 9' started by afavreau, May 23, 2015.

  1. afavreau

    afavreau Senior member

    I want to send a mix to my guitarist so he can track his guitars.

    So I then bounce a m4a for him, but just before I send it, I think, mmm... let's just check if it's ok. So I bring it back to my session only to find out, everything is flanging!?! Nothing is in sync! I don't understand.

    So I make more tests and this time bounce a mp3, m4a and aif only to find out that the .aif (16 and 24 bit) and .mp3 are in perfect sync, but not the m4a again.

    Wow! is this normal? Anyone ever noticed this before? Am I doing something wrong? Or maybe it's the (VBR) playing tricks? I don't know.

    Any comments?
  3. sonnykeyes

    sonnykeyes Senior member

    As you may know, m4a is a lossy compression, so you're eliminating data in the signal. No surprise then that it flanges with your original. If you're really concerned about sync (as I'm sure we all are!) then send your guitarist a WAV or AIF. (You can use a file-transfer service like WeTransfer or DropBox)
    Happy collaborating!
  4. afavreau

    afavreau Senior member


    Yeah, my mp3 are ok though. I brought them back in the session and everything is fine
  5. sonnykeyes

    sonnykeyes Senior member

    I've successfully used mp3s as a bed for a vocalist, but vocal timing is more forgiving. I wouldn't trust a compressed file for something as finicky as an instrumental performance where a microsecond can throw the feel.
  6. afavreau

    afavreau Senior member

    Thanks. It makes sense.
  7. bayswater

    bayswater Senior member

    I'm sure you mean a few milliseconds? Not a millionth of a second.
  8. bambony

    bambony Administrator Staff Member

    I am sure MP3 files are fine for tracking overdubs. In effect you have answered your own question in the OP.

  9. afavreau

    afavreau Senior member

    OP means Original Post?

    So you mean the VBR of .m4a would be doing that?
  10. bambony

    bambony Administrator Staff Member

    Just that MP3 is the way to go for smaller file size transfer for collaboration...

    OP = Orig post... well done!


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