DSP Functions

While SynthBuilder and STK include many of the same basic DSP elements, the implementations can vary slightly. As a precaution, I did not make the assumption that they were necessarily equivalent given the same parameters. For example, the help file for the exponential envelope generator in SynthBuilder states the output signal as

currentValue = currentValue+(1-rate)*(targetValue-currentValue).

While the related STK class Asymp uses the following,

$$\texttt{value\_ = factor\_ * value\_ + constant\_}$$ (1)

where

$$\texttt{constant\_ = ( 1.0 - factor\_ ) * target\_}$$ (2)

It is not immediately obvious whether the implementation is the same. However, substituting (2) into (1) and expanding using the same variables gives

$$v = v+t-v-rt+rv$$ (3)

$$v = rv+t-rt$$ (4)

The $v$ 's in (3) cancel out, confirming the functions are equivalent.