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| -rw-r--r-- | docs/design.org (renamed from design.org) | 43 | ||||
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2 files changed, 37 insertions, 6 deletions
diff --git a/design.org b/docs/design.org index 5e00379..4f5e701 100644 --- a/design.org +++ b/docs/design.org @@ -25,20 +25,25 @@ by Godot. - *Continuous* - whether or not to produce a continuous tone or use ADSR envelope - *Waveform* - a selection of basic waveforms will be implemented in Rust. We can control which one is being generated via a switch in Godot. -- *Phasor* - the shape of the waveform can be dynamically modified by changing the - shape of the phasor driving the oscillator. Given an (x,y) vector, the shape of - the phasor can be "bent" away from it smooth 0-1 slope. -- *Amplitude Envelope* - this controls the volume of sound over time. Typical envelopes +- *Envelope* - this controls the volume of sound over time. Typical envelopes have parameters for: - *Attack* - amount of time before the waveform is at its peak - *Decay* - amount of time it takes to go from peak to sustained level - *Sustain* - the level (amplitude) to sustain while a note is held - *Release* - the amount of time to go to 0 from sustain when note is released +- *Frequency Modulator* - an oscillator that modulates the main tone generator which + has the effect of producing more complex sounds with sidebands of the main signal. + It has two controllable parameters: + - *Frequency multiple* integers create harmonic sidebands while non-integers make + inharmonic tones similar to a bell or metallic sound. + - *FM Depth* the amount of modulation to apply. Increasing by a lot can make some + interesting effects + +Not implemented (yet): + - *Filter* - a low pass filter with a two parameters: - *Cutoff* the frequency where the filter begins - *Resonance* ? i think its like an amplitude boost at the cutoff? -- *Modulator* - a low frequency oscillator that can effect the frequency or filter cutoff - *** Output @@ -47,4 +52,30 @@ a float between -1.0 and 1.0. You can request a certain number of frames, and ge the calculated samples to fill them. We can think of this as essentially the stereo audio jack from a synthesizer. +* Signal Generator Model + +In Puredata, one of the key abstractions is the Signal object, which all of the +audio specific related bits implement. Signals abstract away time, and you can build +an audio pipleine by connecting them together. A phasor drives an oscillator which +sends its signal through a line amplitude signal to shape its volume. + + [[file:diagrams/pd-phasor-oscillator.png]] + +This is roughly what we've built with Rust as iterators. Each ~.next()~ is like a +tick of the =phasor~= object. =cos~= calculates the cosine value like our the +~impl Iterator for Osc~ does in its ~.next()~ function. + +=line~=, when triggered by an input, produces a ramp from 0 to 1 over 1000 ms. +It also "ticks" at the same rate as the other signals (the underlying sample rate). +Each sample value from the cosine is multiplied by the values from the line signal. +At the end of the 1000ms, the =*~= object is now constantly at the max amplitude. + +** Iterator as Signal ? + +Assuming we're calling ~next()~ on each part of our signal chain in the same cycle, +at the same rate, we can utilize Rust's =Iterator= trait as our version of the Signal. +This is how its working now. It is possible this will only get us so far, but +I think we can roll with it. The currently implemented [[../klangfarbrs/src/envelope.rs][Envelope]] module is actually +wrapping three of the =line~= type objects. ~attack~ ~decay~ and ~release~ could +all be described by a ~Line~ struct that has a target amplitude and a duration. diff --git a/docs/diagrams/pd-phasor-oscillator.png b/docs/diagrams/pd-phasor-oscillator.png Binary files differnew file mode 100644 index 0000000..a89a7c0 --- /dev/null +++ b/docs/diagrams/pd-phasor-oscillator.png |
