10 September 2008

Feedback on "Waveform Plots Considered Harmful"

I received lots of feedback on my HA thread and some in the comments. I intend to update the paper incorporating this feedback, archive the original somewhere, and post it for more general consumption soon.
  • Several people commented that the tone of the article in general was too inflammatory, and given that I used waveform plots to make a few important points, potentially hypocritical. I blame the insanely late hour that I wrote it. It will be edited to be a bit more evenhanded.
  • One person commeneted that the particular waveform examples I used seemed to imply that the vinyl master is clipping significantly less than the CD master. I'm seeing that too, and I cant' really explain it. It's clearly not some sort of analog effect in the playback system, and it seems to be consistent across the entire disc. The fundamental issue is the same - buying vinyl does not always mean you are getting a product without hard limiting - so I think the article still stands up well. But the specific point of that example, that there exists a vinyl master which provably has just as much clipping as the CD master, is compromised significantly.

    Note, also, that other people have observed vinyl waveform plots that don't share Mirrored's subtle difference in clipping levels. The clipping levels really do seem to match in those cases.
  • A clearer distinction needs to be made between periodic clipping of periodic signals - which is extremely audible even in small amounts - and clipping of transients, which is far less audible. Modern mastering practices can occupy either extreme or somewhere in between.
  • I'm equivocating between clipping and hard/brickwall limiting; clipping is only one form of hard limiting. A proprietary hard limiter is capable of doing the same job that clipping does, but with potentially far less audible distortion. It's an open question as to how much more audible clipping is than a good hard limiter. Nevertheless, the damage done to the audio is quite significant for all hard limiters.
  • While we're on the subject of things that should be made more clear, the extensive use of dynamic range compression (of the non-limiting variety) clearly has a far more audible effect on the sound than limiting/clipping.
  • Important tip: Bob Katz commented that he always sends vinyl masters out without the use of the hard limiters used on the CD masters. Yay!

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