FCP X clipping audio on export for no apparent reason

Discussion in 'Digital Video' started by jamesdrm, Aug 27, 2012.

  1. jamesdrm macrumors newbie

    Joined:
    Feb 7, 2012
    #1
    I'm trying to export a video with an audio track on FCP x (h.264) but for some reason the audio on the exported clip is clipping (only on the left channel though:confused:).

    The .wav track itself peaks at about -.01db, so that's not the problem.

    I've tried lowering the track in FCP to -2db but the exact same problem happens.

    If anyone could offer some advice I'd be most grateful.

    Thanks!
     
  2. ppc_michael Guest

    ppc_michael

    Joined:
    Apr 26, 2005
    Location:
    Los Angeles, CA
    #2
    That's still a little too close for me. Have you tried dropping it down to -6 dB or so and seeing if it still clips? And do the levels actually reach and exceed 0dB, or does it just sound distorted (like it's a problem instead with the source clip)?

    What is the sampling rate and resolution of both your original audio and the output audio? It could also maybe be a dithering issue or something.
     
  3. jamesdrm thread starter macrumors newbie

    Joined:
    Feb 7, 2012
    #3
    If I take it down to something silly like -6db the clipping stops. It's almost like there's some channel bias. Like I said, when leaving it at what I exported it at (-0.1) the right channel is perfect, it's only the left channel that's clipping.

    It's almost like there's some invisible pan fader I'm not seeing (I'm fairly new at FCPx, so don't put it past me)

    The audio was bounced at 24bit/44.1
    It's not clipping at all. It can't, it's been limited to max out at -0.1, so the problem must lie within FCP/something I've done in FCP

    When exporting in FCP, I'm just using the default settings with the h.264 template
     
  4. ppc_michael Guest

    ppc_michael

    Joined:
    Apr 26, 2005
    Location:
    Los Angeles, CA
    #4
    An H264 template is going to convert your audio down to 16 bits if it's not there already, and could possibly introduce some distortion especially if your 24-bit file is peaking so close to the ceiling. Can you bounce it out of your audio program as a distortion-free 16 bit file and see if you have the same problem?
     
  5. jamesdrm thread starter macrumors newbie

    Joined:
    Feb 7, 2012
    #5
    I didn't know that, thanks!

    Just sampled down to 16bit with dithering and tried the rendering the video again; still clipping on the left channel.

    Going to have to be begrudgingly forced back to Sony Vegas if I can't figure this out
     
  6. KeithPratt macrumors 6502a

    Joined:
    Mar 6, 2007
    #6
    As could compressing to AAC.

    How do you know it's clipping?
     
  7. jamesdrm thread starter macrumors newbie

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    Feb 7, 2012
    #7
    The clip light going off. Plus the stereo field sounds different. It's louder on the left channel.
     
  8. bimmzy macrumors regular

    bimmzy

    Joined:
    Dec 29, 2006
    Location:
    London
    #8
    The levels are too high.

    Using audio in FCP X, or legacy, or Avid, or whatever, When editing on the timeline (storyline) it's advisable not to drive the audio mix over -12dB when looking at the VU meter... seriously!

    For example, dialog, without shouting should be around -20dB (-18dB in Europe).

    If after you done your edit, you want to export the audio at a higher level you must use a limiter, and not drive anything over -6dB on the VU meter.
     
  9. jamesdrm thread starter macrumors newbie

    Joined:
    Feb 7, 2012
    #9
    The entire track is audio (it's a music video), so the levels have to be where they are - again, not clipping. Even if I do lower the levels dramatically, there's still a noticeable bias to the left channel.
     
  10. nateo200, Sep 1, 2012
    Last edited: Sep 1, 2012

    nateo200 macrumors 68030

    nateo200

    Joined:
    Feb 4, 2009
    Location:
    Northern District NY
    #10
    Woah!!! Thats a HOT track (audio level wise :D). I master my audio tracks at -6Db MAX...usually go to -6Db for YouTube/Vimeo stuff because some peoples iPods can't be cranked up too loud...for short films I do that I expect to be played over nice headphones or better yet in my surround mix I worked tirelessly over I master at -12 or Db with peaks no higher than -8 or -6...I watch those audio meters like a hawk...if I see it hit red I lower it...BUT during action scenes with splosions and guns Im fine with yellow at -6db.

    BTW a proper down sample dither or not, to 16-bit won't give you clipping unless you just somehow rape the dynamic range! Many pro audio mixers do not think dither even makes a difference but use it because when done right it does not hurt and could theoretically help....none the less I do like staying in 24bit if I can....but again keep your levels down...when I started editing more seriously I screwed up a project by paying no attention to audio levels, I thought 0db was the way it was supposed to be :O :O lmao. and adjust levels accordingly...dont think of it as a volume nob...volume is for the entire mix while levels are different for different things....
     
  11. jamesdrm thread starter macrumors newbie

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    Feb 7, 2012
    #11

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