What causes this?

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Guitarhacker
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2011/02/03 20:19:52 (permalink)

What causes this?

I have a wave file that shows clipping on one side of the wave...at the bottom. Look at measure 15 where the clipping is shown. the top is clean with headroom. What causes this, and how do you prevent it?


Track 1 is the active track after melodyne. Track 2 is the original wave track as imported from a collaborator's DAW.  So this track was not recorded in my DAW but I have seen uneven wave forms in my own DAW.

I'm guessing that the track was recorded a bit too hot. It's after the fact now. On playback, I was hearing a bit of distortion.... mostly in the highs.... kind of an unpleasant squashing of the highs rather than nice clean highs. Most people not involved in music recording would not hear this on a casual listen. Fortunately, it doesn't have the digital distortion sound of a totally clipped/over that I have heard on other occasions. A thought just occurred to me.... it might be heavy compression on the other DAW in the recording.......

Anyway... thoughts and comments?






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    The Maillard Reaction
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    2011/02/03 20:26:30 (permalink)




    post edited by mister happy - 2018/02/01 12:10:10


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    Guitarhacker
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    Re:What causes this? 2011/02/03 20:39:26 (permalink)
    OK... it is a vocal track... and I was suspecting it was recorded too hot.

    I had heard someone a while back mention DC offset as a cause of asymmetrical waves.

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    jimmyman
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    Re:What causes this? 2011/02/03 21:28:13 (permalink)
    mike_mccue


    Asymmetrical waveforms are associated with harmonic overtones and harmonic distortion and can be quite common on some sources or types of instruments.

    The fact that it is asymmetrical is no big deal... but in this case the signal is/was just to hot.

    best regards,
    mike


       This is the best explanation to this date that I have heard so far and makes the most
    since of the subject matter. I remember having that problem some time ago when
    recording vocs. My recording (of) the vocs weren't all that hot but apparently hot
    enough to cause that. I'm only guessing but maybe the peaks were -6 or so. I found
    that as I lowered some "lows" or "low mids" (during) the recording of that part
    that did lesson the problem of the flat line (on just the flat side of the wavform).

     (and) if I remember right (lowering) the recording level didn't change anything,
    only the EQing did. It didn't sound like distortion but was clearly a flat line on
    one half of the waveform. I have also had times where there was no flat line but
    the "top" and "bottom" half of the waveform were not symmetrical like you would
    normally see, even though upon "listening" to it nothing sounded wrong.

      I would go direct by way of bypassing EQ or the pre used and no problem
    (but) the sound was very muddy in doing so. I'm starting to think now as I look
    back that somewhere in that signal chain that there was some kind of problem,
    whatever that was? As if maybe there was something causing that "loss" of
    clarity and it showed up in the "visual" of the waveform when trying to "clear it up"
    in the recording.

      I may have been using a sound blaster card at the time and maybe it
    would "take" a untreated sound/input, but not anything that was (in this case)
    EQ'd. I also remember that as I recorded the vocs that the (what I heard)
    quality of sound as opposed to (hearing it back was a huge difference).

      I would have expected that the (card) wouldn't sound like a made "for audio"
    card but nothing "that" drastic.

     
    post edited by jimmyman - 2011/02/03 21:33:54
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    Guitarhacker
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    Re:What causes this? 2011/02/03 21:51:02 (permalink)
    Jimmy, you are right, lowering the levels, and even reducing the output of melodyne did nothing to fix the problem.  I haven't tried EQ but I can't go to drastic on that since it is a vox track and a flat eq is almost perfect..... so any drastic cuts will affect it in a negative way.

    I guess the issue was the harmonics that caused the asymmetrical wave to start with and the signal was just too hot and the lower part got clipped.

    I have seen this often in my own guitar and vox tracks... the harmonics thing makes as much sense as anything I've heard, and... there is no real degradation of the sound on those parts....

    I was just a bit curious since it is obviously clipping but not sounding like typical digital overages clipping, which is really intolerable.

    I had one vocal track that was recorded hot...and it sounded pretty good..... no clipping, but after melodyne finished processing it...... aye carramba! I had to go back and reduce some levels seriously to get it to a workable track. It was on the song that you gave me the inspiration to write.... Ought to count for something.....



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    7-string_guy
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    Re:What causes this? 2011/02/04 00:04:44 (permalink)
    I've seen similar waves on my bass tracks. top has headroom, bottom was missing or clipping...i always just adjusted and re-recorded the part...thanks for the answer.. I finally understand.

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    Bristol_Jonesey
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    Re:What causes this? 2011/02/04 04:39:47 (permalink)
    I'm seeing exactly the same thing on a bass synth patch from Dim Pro.

    It sounds absolutely fine, but I was taken aback by the skewed nature of the wave after I'd frozen the synth.


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    batsbrew
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    Re:What causes this? 2011/02/04 10:39:43 (permalink)
    dc offset

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    The Maillard Reaction
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    2011/02/04 10:48:55 (permalink)

    post edited by mister happy - 2018/02/01 12:10:21


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    The Maillard Reaction
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    2011/02/04 11:10:31 (permalink)

    post edited by mister happy - 2018/02/01 12:10:30


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    jimmyman
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    Re:What causes this? 2011/02/04 17:39:20 (permalink)
    mike_mccue


    I think I should add that the asymmetrical results are not specifically the overtones and distortion but rather the results of comb filtering and phase cancellation caused by the existence of overtones and distortion.

    It is also important to realize that it is because the harmonics and distortions occur as short events that come and go... rather than as a constant tones.

    If you simply attempt to generate a complex tone it will appear constant and the peaks will seem symmetrical.



    best regards,
    mike


        This in addition to what you referred to earlier to me sheds even more light on the
    subject.  Back when I had that issue it seems that I recall checking the DC offset
    of that waveform and it was (in the zero's) like .0003 or something, which would
    have me think that dc offset was not the problem although I guess there is some
    relation but not just the offset in and by itself.


    I had one of two situations, either one half of the waveform was "flat lined" in places
    (or) the top half of the waveform was a different (shape) than the bottom half and
    farther or closer away from center than the other half. (even if it wasn't flat lined).

      And it seemed that it was more from the lower frequencies. Maybe because of
    a longer wave length and/or more (or less) RMS strength?  
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    ohhey
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    Re:What causes this? 2011/02/05 00:38:22 (permalink)
    mike_mccue


    I think I should add that the asymmetrical results are not specifically the overtones and distortion but rather the results of comb filtering and phase cancellation caused by the existence of overtones and distortion.

    It is also important to realize that it is because the harmonics and distortions occur as short events that come and go... rather than as a constant tones.

    If you simply attempt to generate a complex tone it will appear constant and the peaks will seem symmetrical.



    best regards,
    mike


    Could it be that the wav the following a very low frequency curve that draws it to one side ?  I've seen this is CD rips of major label recordings and it doesn't seem to affect the sound, at least not to me. I've tried doing DC offset on them and I can't tell the difference, if anything it gets worse. I'd leave it alone.  If you really did have a converter related DC offset problem it would show up on everything.
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    The Maillard Reaction
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    2011/02/05 07:59:41 (permalink)

    post edited by mister happy - 2018/02/01 12:10:44


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