Effects

Basic audio effects.

class tiliqua.dsp.WaveShaper(*args, src_loc_at=0, **kwargs)

Waveshaper maps every sample x to f(x), where f can be any arbitrary python function.

f(x) is evaluated at N=lut_size points at elaboration time, to create a LUT (lookup table ROM) mapping the input domain (ASQ) to output samples. For any input sample that sits between elements in the ROM, linear interpolation is used to determine the output sample.

This can be used for waveshaping, but is also useful for arbitrary remapping of samples, for example tanh-based soft clipping, linear- to exponential or linear-to-log space conversion.

Members:

  • i (In(stream.Signature(ASQ))) – Input stream for sending samples to the waveshaper.

  • o (In(stream.Signature(ASQ))) – Output stream for getting samples from the waveshaper.

__init__(lut_function=None, lut_size=512, continuous=False, macp=None)
lut_functionfunction

Function taking and emitting float values in a valid ASQ range.

lut_sizeint

Size of the LUT ROM in elements. Larger provides a better approximation.

continuousbool

Behavior of linear interpolation at ASQ endpoints. For ASQ.i_bits==1 and for a function where f(+1) ~= f(-1), this should be used to ensure an incoming saw results in a continuous output.

macpmac.MAC

Optional shared MAC provider.

class tiliqua.dsp.PitchShift(*args, src_loc_at=0, **kwargs)

Granular pitch shifter. Works by crossfading 2 separately tracked taps on a delay line - both tap positions are moving towards the write head (for pitching up) or away from the write head (for pitching down). Whenever the tap positions are close to overflowing, the discontinuity is smoothed by a crossfade of length xfade.

Maximum pitch-shifting grain size is the delay line ‘max_delay’ // 2. Smaller grain sizes or crossfades result in a ‘fluttering’ effect, but have lower latency. To reduce fluttering at low latency, one can dynamically track the grain_sz based on the input frequency.

The delay line write head must be hooked up to the input source from outside this component (this allows multiple shifters to share a single delay line).

Members:

  • i (In(stream.Signature(StructLayout({"pitch": ..., "grain_sz": ...}))) – Input stream, one element per desired output sample. pitch is a fixed.SQ i where 0 is no pitch shift, positive shifts up (e.g. 1 is 2x speed), negative shifts down. grain_sz is the length of audio grain used for pitch shifting - up to the tap.max_delay

  • o (In(stream.Signature(ASQ))) – Output stream of pitch shifted samples.

__init__(tap, xfade=256, macp=None)
tapdelay_line.DelayLineTap()

DelayLineTap which pitch shifter reads at 2 tap positions for every output sample. The delayline write head must be hooked up to the input source.

xfadeint

Crossfade length between taps, in samples. Crossfades occur at every transition where we switch from one part of the delayline to the other. Longer crossfades and grain sizes produce less ‘fluttering’.

macpmac.MAC

Optional shared MAC provider.