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Simple Scrub Discussion

This Sound uses a Waveshaper module to implement a simple scrub. The Waveshaper looks into its ShapingFunction at the location specified by the Index. So, by moving the Index you move through the sample in the ShapingFunction field. However, the index needs to be smoothly varying to avoid skips and jumps in the output.

The !TimeIndex fader is scaled and offset in the Constant to be in the range of zero to one, then it is smoothed by the AmplitudeFollower module, and finally shifted back the original -1 to +1 range. (The scale and offset is needed because the AmplitudeFollower will always have a positive output.)

-- KurtHebel - 29 Feb 2004

I like this Sound, but I discovered an interesting anomaly. I changed the time constant in the AmplitudeFollower to a Hot Parameter, played the Sound and set the Hot Parameter to '1 s' ( same as in your original). The behavior was entirely different. It was as though the Hot Parameter value was not actually getting to the TimeConstant!

I put an oscilloscope on it and could see that there was no apparent smoothing.

I tried further experiments with AmplitudeFollowers and the oscilloscope and found that when using a Hot Parameter, values greater than about 0.08 no longer seem to affect the output shape. If a larger value is typed directly into the TimeConstant field, it works fine.

-- BillMeadows - 05 Mar 2004

I submitted this as a report in the Know section: AmpFollowHotTimeConst.

-- KurtHebel - 11 Mar 2004

yep the sound is cool. i play it with hot wacom pen controls. is there actually another solution to "upsample" hot controlers to audio rate signals? or is this amplitudeFollower the only workaround?

-- MichaelStrohmann - 06 Apr 2006

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