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strad.rb
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strad.rb
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# strad.rb -- Translation CLM --> Snd-Ruby
#
# Bowed string physical model with stiffness. CLM version adapted
# from the Matlab and C versions courtesy of JOS and Stefania Serafin
# from code revised on 7/14/01
#
# CLM version by Juan Reyes
#
# Translator/Author: Michael Scholz <mi-scholz@users.sourceforge.net>
# Created: Sun Mar 16 02:46:52 CET 2003
# Changed: Wed Nov 17 23:56:56 CET 2010
require "ws"
class DCBlock
def initialize(input = 0.0, output = 0.0)
@dc_input = input
@dc_output = output
end
def dcblock(sample)
@dc_output = sample + (0.99 * @dc_output - @dc_input)
@dc_input = sample
@dc_output
end
def inspect
format("#<%s: input: %1.3f, output: %1.3f>", self.class, @dc_input, @dc_output)
end
end
add_help(:bow, "bow(start = 0, dur = 1, freq = 440, amp = 0.5, *args)
:bufsize 2205 @srate 22050
:fb 0.2 bow force (0.0..1.0)
:vb 0.05 bow velocity (0.0..0.8)
:bp 0.08 bow position (0.0 bridge, 0.5 middle of string, 1.0 nut)
:inharm 0.1 inharmonicity (0.0 harmonic, 1.0 not harmonic)
:ampenv [0, 0, 20, 1, 48, 1, 92, 0, 100, 0]
:degree 45
:dist 0.0025
:reverb 0.005")
def bow(start = 0, dur = 1, freq = 440, amp = 0.5, *args)
bufsize, fb, vb, bp, inharm, ampenv, degree, dist, reverb = nil
optkey(args, binding,
[:bufsize, 2205],
[:fb, 0.2],
[:vb, 0.05],
[:bp, 0.08],
[:inharm, 0.1],
[:ampenv, [0, 0, 20, 1, 48, 1, 92, 0, 100, 0]],
[:degree, 45],
[:dist, 0.0025],
[:reverb, 0.005])
len = seconds2samples(dur)
ampf = make_env(:envelope, ampenv, :scaler, amp, :length, len)
dcblocker = DCBlock.new
vinut = make_vct(bufsize)
vinbridge = make_vct(bufsize)
vinutt = make_vct(bufsize)
vinbridget = make_vct(bufsize)
vib = vin = vibt = vint = 0.0
mus = 0.8 # friction coeff
twavespeedfactor = 5.2
posl = posr = poslt = posrt = indexl = indexr = indexlt = indexrt = 0
indexl_1 = indexr_1 = indexlt_1 = indexrt_1 = indexl_2 = indexr_2 = indexlt_2 = indexrt_2 = 0
updl = updr = updlt = updrt = 0
# biquad coefficients from jos follow
b0b = 0.859210
b1b = -0.704922
b2b = 0.022502
a1b = -0.943639
a2b = 0.120665
b0n = 7.0580050e-001
b1n = -5.3168461e-001
b2n = 1.4579750e-002
a1n = -9.9142489e-001
a2n = 1.8012052e-001
# bridge side, torsional waves
b0bt = 9.9157155e-001
b1bt = -8.2342890e-001
b2bt = 8.8441749e-002
a1bt = -8.3628218e-001
a2bt = 9.2866585e-002
# finger side, torsional waves
b0nt = 4.3721359e-001
b1nt = -2.7034968e-001
b2nt = -5.7147560e-002
a1nt = -1.2158343e+000
a2nt = 3.2555068e-001
# initializations for the filters
xm1bt = xm2bt = xm1nt = xm2nt = ym1bt = ym2bt = ym1nt = ym2nt = xm1b = xm2b = ym1b = ym2b = 0.0
xm1n = xm2n = ym1n = ym2n = ynb = ynbt = ynn = ynnt = ya1nb = ynba1 = y1nb = 0.0
# friedlander friction inits
aa = bb1 = cc1 = delta1 = bb2 = cc2 = delta2 = v = v1 = v2 = rhs = lhs = vtemp = f = 0.0
string_impedance = 0.55
string_impedancet = 1.8
stick = 0
zslope = 1.0 / ((1.0 / (2.0 * string_impedance)) + (1.0 / (2.0 * string_impedancet)))
xnn = xnb = xnnt = xnbt = 0.0
alphar = alphal = alphart = alphalt = 0
l = (mus_srate() / freq) - 2
lt = l / twavespeedfactor
del_right = l * bp
del_left = l * (1 - bp)
del_leftt = lt * (1 - bp)
del_rightt = lt * bp
samp_rperiod = del_right.floor
samp_lperiod = del_left.floor
samp_lperiodt = del_leftt.floor
samp_rperiodt = del_rightt.floor
samp_rperiod = [samp_rperiod, 0].max
samp_rperiod = [samp_rperiod, bufsize - 1].min
samp_lperiod = [samp_lperiod, 0].max
samp_lperiod = [samp_lperiod, bufsize - 1].min
alphar = (del_right - samp_rperiod).to_f
alphal = (del_left - samp_lperiod).to_f
samp_rperiodt = [samp_rperiodt, 0].max
samp_rperiodt = [samp_rperiodt, bufsize - 1].min
samp_lperiodt = [samp_lperiodt, 0].max
samp_lperiodt = [samp_lperiodt, bufsize - 1].min
alphart = (del_rightt - samp_rperiodt).to_f
alphalt = (del_leftt - samp_lperiodt).to_f
posr = (len + posr) % bufsize
posl = (len + posl) % bufsize
posrt = (len + posrt) % bufsize
poslt = (len + poslt) % bufsize
bowfilt = lambda do |inharmon|
# initialize coefficients
ynb = ((b0b * vib + b1b * xm1b + b2b * xm2b) - a1b * ym1b) - a2b * ym2b
xm2b, xm1b = xm1b, vib
ym2b, ym1b = ym1b, ynb
ynn = ((b0n * vin + b1n * xm1n + b2n * xm2n) - a1n * ym1n) - a2n * ym2n
xm2n, xm1n = xm1n, vin
ym2n, ym1n = ym1n, ynn
# filters for torsional waves
ynbt = ((b0bt * vibt + b1bt * xm1bt + b2bt * xm2bt) - a1bt * ym1bt) - a2bt * ym2bt
xm2bt, xm1bt = xm1bt, vibt
ym2bt, ym1bt = ym1bt, ynbt
ynnt = ((b0nt * vint + b1nt * xm1nt + b2nt * xm2nt) - a1nt * ym1nt) - a2nt * ym2nt
xm2nt, xm1nt = xm1nt, vint
ym2nt, ym1nt = ym1nt, ynnt
inharmon = [inharmon, 0.00001].max
inharmon = [inharmon, 0.9999].min
ya1nb = y1nb = -(inharmon * ynb) + ynba1 + inharmon * ya1nb
ynba1 = ynb
y1nb = -y1nb
ynn = -ynn
ynbt = -ynbt
end
friedlander = lambda do |vh|
aa = zslope
bb1 = ((0.2 * zslope + 0.3 * fb) - zslope * vb) - zslope * vh
cc1 = ((0.06 * fb + zslope * vh * vb) - 0.2 * zslope * vh) - 0.3 * vb * fb
delta1 = bb1 * bb1 - 4 * aa * cc1
bb2 = ((-0.2 * zslope - 0.3 * fb) - zslope * vb) - zslope * vh
cc2 = (((0.06 * fb + zslope * vh * vb) + 0.2 * zslope * vh) + 0.3 * vb * fb) + 0.1 * fb
delta2 = bb2 * bb2 - 4 * aa * cc2
if vb.zero? or fb.zero?
v = vh
else
if vh == vb
v, stick = vb, 1
else
if vh > vb
lhs, rhs = 0.0, 1.0
else
rhs, lhs = 0.0, 1.0
end
if rhs == 1.0
if delta1 < 0
v, stick = vb, 1
else
if stick == 1
vtemp = vb
f = 2.0 * zslope * (vtemp - vh)
if f >= (-(mus * fb))
v = vtemp
else
v1 = (-bb1 + sqrt(delta1)) / (2.0 * aa)
v2 = (-bb1 - sqrt(delta1)) / (2.0 * aa)
v = [v1, v2].min
stick = 0
end
else
v1 = (-bb1 + sqrt(delta1)) / (2.0 * aa)
v2 = (-bb1 - sqrt(delta1)) / (2.0 * aa)
v = [v1, v2].min
stick = 0
end
end
elsif lhs == 1.0
if delta2 < 0
v, stick = vb, 1
else
if stick == 1
vtemp = vb
f = zslope * (vtemp - vh)
if f <= (mus * fb) and f > 0
v = vtemp
else
v1 = (-bb2 - sqrt(delta2)) / (2.0 * aa)
v2 = (-bb2 + sqrt(delta2)) / (2.0 * aa)
vtemp = [v1, v2].min
stick = 0
if vtemp > vb
v, stick = vb, 1
else
v = vtemp
f = zslope * (v - vh)
end
end
else
v1 = (-bb2 - sqrt(delta2)) / (2.0 * aa)
v2 = (-bb2 + sqrt(delta2)) / (2.0 * aa)
v = [v1, v2].min
stick = 0
end
end
if v > vb
v, stick = vb, 1
end
end
end
f = zslope * (v - vh)
xnn = y1nb + (f / (2.0 * string_impedance))
xnb = ynn + (f / (2.0 * string_impedance))
end
end
i = 0
run_instrument(start, dur, :distance, dist, :reverb_amount, reverb, :degree, degree) do
indexl = ((i + posl + bufsize) - samp_lperiod) % bufsize
indexr = ((i + posr + bufsize) - samp_rperiod) % bufsize
indexlt = ((i + poslt + bufsize) - samp_lperiodt) % bufsize
indexrt = ((i + posrt + bufsize) - samp_rperiodt) % bufsize
indexl_1 = (((i + posl + bufsize) - samp_lperiod) - 1) % bufsize
indexr_1 = (((i + posr + bufsize) - samp_rperiod) - 1) % bufsize
indexlt_1 = (((i + poslt + bufsize) - samp_lperiodt) - 1) % bufsize
indexrt_1 = (((i + posrt + bufsize) - samp_rperiodt) - 1) % bufsize
indexl_2 = (((i + posl + bufsize) - samp_lperiod) - 2) % bufsize
indexr_2 = (((i + posr + bufsize) - samp_rperiod) - 2) % bufsize
indexlt_2 = (((i + poslt + bufsize) - samp_lperiodt) - 2) % bufsize
indexrt_2 = (((i + posrt + bufsize) - samp_rperiodt) - 2) % bufsize
# fractional delay lines
vib = ((vinbridge[indexl_2] * (alphal - 1) * (alphal - 2)) / 2.0) +
(vinbridge[indexl_1] * -alphal * (alphal - 2)) +
((vinbridge[indexl] * alphal * (alphal - 1)) / 2.0)
vin = ((vinut[indexr_2] * (alphar - 1) * (alphar - 2)) / 2.0) +
(vinut[indexr_1] * -alphar * (alphar - 2)) +
((vinut[indexr] * alphar * (alphar - 1)) / 2.0)
vibt = ((vinbridget[indexlt_2] * (alphalt - 1) * (alphalt - 2)) / 2.0) +
(vinbridget[indexlt_1] * -alphalt * (alphalt - 2)) +
((vinbridget[indexlt] * alphalt * (alphalt - 1)) / 2.0)
vint = ((vinutt[indexrt_2] * (alphart - 1) * (alphart - 2)) / 2.0) +
(vinutt[indexrt_1] * -alphart * (alphart - 2)) +
((vinutt[indexrt] * alphart * (alphart - 1)) / 2.0)
# biquad filters
bowfilt.call(inharm)
vh1 = ynn + y1nb + ynnt + ynbt
# now solve set of simultaneous equations for v and f
friedlander.call(vh1)
f = zslope * (v - vh1)
xnnt = ynbt + (f / (2.0 * string_impedancet))
xnbt = ynnt + (f / (2.0 * string_impedancet))
updl = (i + posl + bufsize) % bufsize
updr = (i + posr + bufsize) % bufsize
updlt = (i + poslt + bufsize) % bufsize
updrt = (i + posrt + bufsize) % bufsize
vinbridge[updl] = xnb
vinut[updr] = xnn
vinbridget[updlt] = xnbt
vinutt[updrt] = xnnt
out_val = env(ampf) * dcblocker.dcblock(xnb)
lhs = rhs = 0.0
i += 1
out_val
end
end
=begin
with_sound(:channels, 2) do bow(0, 3, 400, 0.5, :vb, 0.15, :fb, 0.1, :inharm, 0.25) end
with_sound(:channels, 2) do bow(0, 2, 440, 0.5, :fb, 0.25) end
with_sound(:channels, 2) do bow(0, 4, 600, 0.8) end
with_sound(:channels, 2) do bow(0, 6, 147, 2, :fb, 0.035, :vb, 0.1) end
with_sound(:channels, 2) do bow(0, 3, 1100, 0.5, :vb, 0.45, :fb, 0.9, :inharm, 0.3) end
with_sound(:channels, 2) do bow(0, 3, 1500, 0.5, :vb, 0.25, :fb, 0.9, :inharm, 0.3) end
with_sound(:channels, 2) do bow(0, 3, 1525, 0.5, :vb, 0.25, :fb, 0.9, :inharm, 0.3) end
with_sound(:channels, 2, :reverb, :jc_reverb_rb) do bow(0, 1, 400, 0.5, :reverb, 0.0051) end
with_sound(:channels, 2, :reverb, :jc_reverb_rb) do
bow(0, 3, 366, 0.5, :degree, 0)
bow(0, 3, 422, 0.5, :degree, 90)
bow(4, 6, 147, 2, :fb, 0.035, :vb, 0.1, :reverb, 0.051)
end
=end
# strad.rb ends here