**diff options**

author | Tom Schouten <doelie@users.sourceforge.net> | 2006-08-15 15:11:52 +0000 |
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committer | Tom Schouten <doelie@users.sourceforge.net> | 2006-08-15 15:11:52 +0000 |

commit | 4a83a80c044c9613bd50a63dd9ac5a97e2c028b5 (patch) | |

tree | b424886f7e10d928a27ae16a64d577d749768a4d /modules/resofilt~.c | |

parent | 55ba904ccef240df1056157e4a376d4cb1eb476d (diff) |

creb 0.9.2 import

svn path=/trunk/externals/creb/; revision=5607

Diffstat (limited to 'modules/resofilt~.c')

-rw-r--r-- | modules/resofilt~.c | 57 |

1 files changed, 34 insertions, 23 deletions

diff --git a/modules/resofilt~.c b/modules/resofilt~.c index ba74532..0227dfc 100644 --- a/modules/resofilt~.c +++ b/modules/resofilt~.c @@ -86,15 +86,19 @@ static t_int *resofilt_perform_fourpole(t_int *w) t_float f_prev = ctl->c_f_prev; t_float r_prev = ctl->c_r_prev; - /* use rms of input to drive freq and reso - this is such that connecting a dsp signal to the inlets has a reasonable result, - even if the inputs are oscillatory. the rms values will be interpolated linearly - (that is, linearly in the "analog" domain, so exponentially in the z-domain) */ + /* use rms of input to drive freq and reso. this is such that + connecting a dsp signal to the inlets has a reasonable result, + even if the inputs are oscillatory. the rms values will be + interpolated linearly (that is, linearly in the "analog" domain, + so exponentially in the z-domain) */ reso_rms = freq_rms = 0.0f; for (i=0; i<n; i++){ - t_float _freq = *freq++; /* first input is the reso frequency (absolute) */ - t_float _reso = *reso++; /* second input is the resonnance (0->1), >1 == self osc */ + /* first input is the reso frequency (absolute) */ + t_float _freq = *freq++; + /* second input is the resonnance (0->1), >1 == self osc */ + t_float _reso = *reso++; + freq_rms += _freq * _freq; reso_rms += _reso * _reso; } @@ -104,12 +108,14 @@ static t_int *resofilt_perform_fourpole(t_int *w) r = sqrt(sqrt(reso_rms)); - /* calculate the new pole locations - we use an impulse invariant transform: the moog vcf poles are located at + /* calculate the new pole locations. we use an impulse invariant + transform: the moog vcf poles are located at + s_p = (-1 +- r \sqrt{+- j}, with r = (k/4)^(1/4) \in [0,1] - the poles are always complex, so we can use an orthogonal implementation - both conj pole pairs have the same angle, so we can use one phasor and 2 radii + the poles are always complex, so we can use an orthogonal + implementation both conj pole pairs have the same angle, so we + can use one phasor and 2 radii */ /* compute phasor, radius and update eqs @@ -179,7 +185,8 @@ static t_int *resofilt_perform_fourpole(t_int *w) *out++ = x; - /* saturate (normalize if pow > 1) state to prevent explosion and to allow self-osc */ + /* saturate (normalize if pow > 1) state to prevent explosion + * and to allow self-osc */ _sat_state(stateA); _sat_state(stateB); @@ -222,13 +229,15 @@ static t_int *resofilt_perform_threepole(t_int *w) t_float f_prev = ctl->c_f_prev; t_float r_prev = ctl->c_r_prev; - t_float sqrt5 = sqrtf(5.0f); + t_float sqrt5 = sqrt(5.0); /* use rms of input to drive freq and reso */ reso_rms = freq_rms = 0.0f; for (i=0; i<n; i++){ - t_float _freq = *freq++; /* first input is the reso frequency (absolute) */ - t_float _reso = *reso++; /* second input is the resonnance (0->1), >1 == self osc */ + /* first input is the reso frequency (absolute) */ + t_float _freq = *freq++; + /* second input is the resonnance (0->1), >1 == self osc */ + t_float _reso = *reso++; freq_rms += _freq * _freq; reso_rms += _reso * _reso; } @@ -238,8 +247,9 @@ static t_int *resofilt_perform_threepole(t_int *w) r = cbrt(reso_rms); - /* calculate the new pole locations - we use an impulse invariant transform: the 303 vcf poles are located at + /* calculate the new pole locations. we use an impulse invariant + transform: the 303 vcf poles are located at + s_p = omega(-1 + r sqrt(5) e^{pi/3(1+2p)}) real pole: omega * (-1 -r) @@ -248,13 +258,13 @@ static t_int *resofilt_perform_threepole(t_int *w) imag = omega (+- 2 r) - this is a strange beast. legend goes it was "invented" by taking the moog vcf - and moving one cap up, such that the not-so controllable 3-pole that emerged - would avoid the moog patent.. + this is a strange beast. legend goes it was "invented" by taking + the moog vcf and moving one cap up, such that the not-so + controllable 3-pole that emerged would avoid the moog patent.. - so, the sound is not so much the locations of the poles, but how the filter - reacts to time varying controls. i.e. the pole movement with constant reso, - used in the tb-303. + so, the sound is not so much the locations of the poles, but how + the filter reacts to time varying controls. i.e. the pole + movement with constant reso, used in the tb-303. */ @@ -320,7 +330,8 @@ static t_int *resofilt_perform_threepole(t_int *w) *out++ = x; - /* saturate (normalize if pow > 1) state to prevent explosion and to allow self-osc */ + /* saturate (normalize if pow > 1) state to prevent explosion + * and to allow self-osc */ _sat_state(stateA); _sat_state(stateB); |