[Ardour-Users] click free editing and zero crossings?

[John Emmas]

On 20 May 2010, at 12:48, Thomas Vecchione wrote:

> 
> 
> On Thu, May 20, 2010 at 7:18 AM, John Emmas <johne53 at tiscali.co.uk> wrote:
> 
> Most people can visualize how difficult it would be to produce such an edit successfully - and yet they continue to believe that editing at a zero crossing is somehow easier (which it isn't, for all the reasons stated already).  
> 
> 
> What reasons exactly, I just listed exactly why it IS easier.  If you are referring to matching of slopes, that is the only reason I could see for it being listed as not being 'easier' 
> 

Consider the case of two identical waveforms (i.e. theoretically capable of being perfectly edited).  Start off with the simplest case (a continuous, uniform frequency such as a sine wave).  Detecting two corresponding zero crossings and producing a flawless edit should be easy enough.  But uniform frequencies don't make for interesting waveforms.  Most waveforms will have a fundamental frequency, modulated by harmonics.  In a small window either side of the preferred zero crossing (the one corresponding to the fundamental frequency) there'll often be further zero crossings caused by the harmonics.  Detecting two that match mightn't be so difficult if the waveforms are (literally) identical.  But if they're (say) two different takes of the same bit of music, there's a good chance that the harmonics will have slightly different phase and timing relationships in each case.  This makes it no more reliable to edit at a zero crossing point than to edit at any other arbitrary value.  Of course, if you can see the waveforms visually, that's a great help - but seeing them would be a great help anyway, no matter where you wanted to place your edit.

The only thing that's intrinsically helpful about zero crossings is that crossing point is guaranteed to exist in all alternating waveforms.

John
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