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Digital delay effect: avoiding clicks on delay time change

up vote 14 down vote favorite

I'm implementing a digital audio delay effect using a simple circular delay line. Changing the delay time by making the delay line longer or shorter introduces discontinuities in the audio signal, resulting in clicks.

What would be the best (most pleasing for the ears) strategy to avoid such clicks when changing delay time?

2 Answers

up vote 4 down vote accept

If you are not changing the delay length very often, and you don't want to have a Doppler effect that comes from continuously changing the delay length, then try a cross-fade. Both delay lengths should be running simultaneously for a moment, and you would fade the old one out while fading the new one in.

up vote 3 down vote

If you have a continuously varying delay like, for example, a chorus or flanger, you need a to implement a time varying fractional delay in addition to your regular (integer) delay line.

If you only need to change the delay occasionally in discrete steps, a cross fade will work fine.


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Digital delay effect: avoiding clicks on delay time change

up vote 14 down vote

I'm implementing a digital audio delay effect using a simple circular delay line. Changing the delay time by making the delay line longer or shorter introduces discontinuities in the audio signal, resulting in clicks.

What would be the best (most pleasing for the ears) strategy to avoid such clicks when changing delay time?


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up vote 9 down vote

If you are not changing the delay length very often, and you don't want to have a Doppler effect that comes from continuously changing the delay length, then try a cross-fade. Both delay lengths should be running simultaneously for a moment, and you would fade the old one out while fading the new one in.

edit

That can be musically pleasing/useful, too, and appropriate for continuously changing delay control. It needs a fractional delay line with interpolation. - Olli Niemitalo Jan 13 '17 at 8:08

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