DSP
Modules
Controls
Generating sound

DSP

Worp comes with a library with basic constructs for doing audio synthesis and processing. This library provides abstracts for modules, which are objects that process of generate sound, and can be controlled by controls.

Modules

Technicaly, a module is a Lua table with a __call entry in its metatable. This allows the table to be called like a function, but also to have callable methods.

Modules are instantiated by calling the appropriate library function, and can optionally be passed initial values for the controls. The following will generate a sine oscillator with an initial frequency of 500 Hz:

  osc = Dsp:Osc { f = 1500 }

osc can be handled as a function, and will generate a new sample each time it is called.

For example, to see the above oscillator in action try:

  for i = 1, 100 do
     print(osc())
  end

The Worp console output will print the sample values:

  0.21209065141554
  0.41453117669030
  0.59811053049122
  ...

Some modules like filters can also process audio, and will take one or more sample values when called. To send the output of a 30 Hz saw wave into a 100 Hz low pass filter with a resonance of 3:

  o = Dsp:Saw { f = 30 }
  f = Dsp:Filter { f = 100, Q = 3 }
  
  for = i 1, 100 do
    print(f(o())
  end

For more details, check the modules page

Controls

Modules often have one or more controls to effect the behaviour. The module object provides a handy :help() method to show what controls are available:

  f = Dsp:Filter { f = 100, Q = 3 }
  f:help()

will print

  Biquad filter:
   - type: Filter type (lp/hp/bp/bs/ls/hs/eq/ap)
   - f: Frequency (0..20000)
   - Q: Resonance (0.1..100)
   - gain: Shelf/EQ filter gain (-60..60)

To set the value of a control, use the :set() method:

  f:set { type = "hp", f = 200 }

The Jack library knows about controls, and provides a shorthand to map controls to midi CC's. The following snippet will map all four filter controls to CC 10, 11, 12 and 13 on midi channel 1:

  j = Jack:new("worp")
  f = Dsp:Filter()
  m = Jack:midi("midi")
  m:map_mod(1, 10, f)

To map a single control, use:

  m:map_control(1, 10, f:control "Q")

Generating sound

This is where the Jack and Dsp libraries come together. The fragment below will low-pass filter a saw wave, send the result to a jack audio port called 'worp:synth-out-1', and connect this port to all available input ports in the system:

  s = Dsp:Saw { f = 50 }
  f = Dsp:Filter { ft = "lp", f = 1500, Q = 4 }
  
  j = Jack:new("worp")
  
  j:dsp("synth", 0, 1, function()
     return f(s())
  end)
  
  j:connect("worp")