bpf
bpf — Break point function with linear interpolation
Syntax
ky bpf kx, kx1, ky1, kx2, ..., kxn, kyn
iy bpf ix, ix1, iy1, ix2, ..., ixn, iyn
kys[] bpf kxs[], kx1, ky1, kx2, ..., kxn, kyn
iys[] bpf ixs[], ix1, iy1, ix2, ..., ixn, iyn
ky bpf kx, kxs[], kys[]
iy bpf ix, ixs[], iys[]
ay bpf ax, kx1, ky1, kx2, ..., kxn, kyn
ay bpf ax, kxs[], kys[]
ky, kw bpf kx, kxs[], kys[], kws[]
Performance
kx -- Input value
kxn, kyn -- Defines a breakpoint. Can be changed at krate, but all kxs must be sorted
The points (kx1, ky1), (kx2, ky2), etc, define a linearly interpolated function. This function is evaluated at point kx. This function extends to both -inf and +inf, so if kx < kx1 then ky = ky1 and the same holds true the other end.
These are equivalent:
ky bpf kx, 0, 0, 0.5, 10, 1.02, 200
itab ftgenonce 0, 0, -27, 0, 0, 50, 10, 102, 200
ky = tablei(limit(kx, 0, 1.02)*100, itab)
![[Note]](images/note.png)
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Note |
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x values need to be sorted. Both x and y values can change but x values must stay sorted. |
Examples
Here is an example of the bpf opcode. Play bpf.csd
Example 107. Example of the bpf opcode.
<CsoundSynthesizer> <CsOptions> -odac </CsOptions> <CsInstruments> ; Example for opcode bpf /* bpf stands for Break Point Function Given an x value and a series of pairs (x, y), it returns the corresponding y value in the linear curve defined by the pairs It works both at i- and k- time ky bpf kx, kx0, ky0, kx1, ky1, kx2, ky2, ... kys[] bpf kxs[], kx0, ky0, kx1, ky1, kx2, ky2, ... NB: x values must be ordered (kx0 < kx1 < kx2 etc) See also: bpfcos, linlin, lincos */ sr = 44100 ksmps = 64 nchnls = 2 0dbfs = 1 instr 1 kx line -1, p3, 2.5 ky bpf kx, \ 0, 0, \ 1.01, 10, \ 2, 0.5, \ 2.5, -1 if metro(10) == 1 then printsk "kx: %f ky: %f \n", kx, ky endif endin instr 2 ; test i-time ix = 1.2 iy bpf ix, 0,0, 0.5,5, 1,10, 1.5,15, 2,20, 2.5,25, 3,30 prints "iy: %f", iy turnoff endin instr 3 ; bpf also works with arrays kx[] fillarray 0, 0.15, 0.25, 0.35, 0.45, 0.55, 0.6 ky[] bpf kx, 0,0, 0.1,10, 0.2,20, 0.3,30, 0.4,40, 0.5,50 printarray ky, 1, "", "ky=" turnoff endin instr 4 ; bpf as an envelope generator, like linsegb but driven by external phase ; bpf + rms can also be used as compressor atime linseg 0, p3*0.62, p3, p3*0.38, 0 aenv = bpf(atime, 0,0, 0.1,1, 0.5, 0.2) ^ 2 kbw = bpf(timeinsts(), 0, 0, p3*0.62, 1) ^ 3 asig = (beosc(1000, kbw, -1, rnd(6.28)) + beosc(1012, kbw, -1, rnd(6.28))) * 0.3 kratio bpf dbamp(rms:k(asig)), -12, 1, -6, 0.4, -3, 1/100 asig *= aenv * interp(lagud(kratio, 0.01, 0.1)) outs asig, asig endin </CsInstruments> <CsScore> ; i 1 0 3 ; i 2 0 -1 ; i 3 0 -1 i 4 0 3 </CsScore> </CsoundSynthesizer>