src/sigil/dsp/osc.sgl

1;;; (sigil dsp osc) - Oscillators

2;;;

3;;; Wavetable, bandlimited, FM, and phase oscillators.

4;;;

5;;; ```scheme

6;;; (import (sigil dsp core) (sigil dsp osc))

7;;; (dsp-init)

8;;; (define osc (make-oscillator 'sine 440.0 0.5))

9;;; (osc-compute osc) ; => one sample

10;;; ```

12(define-library (sigil dsp osc)

13 (export

14 make-oscillator

15 make-osc make-osc-ft osc-compute osc-set-freq! osc-set-amp!

16 make-posc3 posc3-compute posc3-set-freq! posc3-set-amp!

17 make-blsaw blsaw-compute blsaw-set-freq! blsaw-set-amp!

18 make-blsquare blsquare-compute blsquare-set-freq! blsquare-set-amp!

19 make-bltriangle bltriangle-compute bltriangle-set-freq! bltriangle-set-amp!

20 make-fosc fosc-compute fosc-set-freq! fosc-set-index! fosc-set-amp!

21 make-phasor phasor-compute phasor-set-freq!

22 make-ks ks-compute ks-trigger!

23 ks-set-freq! ks-set-decay! ks-set-excite-gain!

24 make-fm4 fm4-set-op! fm4-set-algorithm! fm4-set-feedback!

25 fm4-compute fm4-algorithm-name)

27 (begin

28 (define-native make-osc)

29 (define-native make-osc-ft)

30 (define-native (osc-compute osc))

31 (define-native (osc-set-freq! osc freq))

32 (define-native (osc-set-amp! osc amp))

33 (define-native make-posc3)

34 (define-native (posc3-compute osc))

35 (define-native (posc3-set-freq! osc freq))

36 (define-native (posc3-set-amp! osc amp))

37 (define-native (make-blsaw freq amp))

38 (define-native (blsaw-compute osc))

39 (define-native (blsaw-set-freq! osc freq))

40 (define-native (blsaw-set-amp! osc amp))

41 (define-native make-blsquare)

42 (define-native (blsquare-compute osc))

43 (define-native (blsquare-set-freq! osc freq))

44 (define-native (blsquare-set-amp! osc amp))

45 (define-native (make-bltriangle freq amp))

46 (define-native (bltriangle-compute osc))

47 (define-native (bltriangle-set-freq! osc freq))

48 (define-native (bltriangle-set-amp! osc amp))

49 (define-native (make-fosc freq car mod indx amp))

50 (define-native (fosc-compute osc))

51 (define-native (fosc-set-freq! osc freq))

52 (define-native (fosc-set-index! osc indx))

53 (define-native (fosc-set-amp! osc amp))

54 (define-native make-phasor)

55 (define-native (phasor-compute phasor))

56 (define-native (phasor-set-freq! phasor freq))

57 (define-native (make-ks freq decay excite-gain))

58 (define-native (ks-compute ks gate))

59 (define-native (ks-trigger! ks))

60 (define-native (ks-set-freq! ks freq))

61 (define-native (ks-set-decay! ks decay))

62 (define-native (ks-set-excite-gain! ks gain))

64 ;; Four-operator FM voice (fm4.h). Operators are 0..3; algorithm

65 ;; 0..7; feedback 0..1 on operator 3; velocity scales the index

66 ;; through (1 - vel-depth + vel-depth * velocity^vel-curve).

67 ;;; Create a four-operator FM voice. `algorithm` is 0..7 (see

68 ;;; fm4-algorithm-name), `feedback` 0..1 self-modulates operator 3,

69 ;;; and velocity scales the index through

70 ;;; (1 - vel-depth + vel-depth * velocity^vel-curve).

71 (define-native (make-fm4 algorithm feedback vel-depth vel-curve)

72 (: number? number? number? number? -> foreign?))

73 ;;; Set operator `op` (0..3): frequency ratio, level 0..1 and a

74 ;;; linear ADSR (attack, decay, release in seconds; sustain 0..1).

75 (define-native (fm4-set-op! fm4 op ratio level attack decay sustain release)

76 (: foreign? integer? number? number? number? number? number? number? -> any?))

77 (define-native (fm4-set-algorithm! fm4 algorithm)

78 (: foreign? integer? -> any?))

79 (define-native (fm4-set-feedback! fm4 feedback)

80 (: foreign? number? -> any?))

81 ;;; One sample. A rising edge on `gate` (> 0.5) resets every

82 ;;; operator's phase and restarts its envelope; index 0 makes each

83 ;;; carrier a pure sine at freq * ratio.

84 (define-native (fm4-compute fm4 freq gate index velocity)

85 (: foreign? number? number? number? number? -> number?))

86 ;;; Name of algorithm 0..7, or #f out of range.

87 (define-native (fm4-algorithm-name algorithm)

88 (: integer? -> (maybe string?)))

90 ;;; Create an oscillator by type.

91 ;;; Types: sine, saw, square, triangle, fm

92 (define (make-oscillator type freq amp . opts)

93 (case type

94 ((sine) (make-osc freq amp))

95 ((saw) (make-blsaw freq amp))

96 ((square) (if (null? opts)

97 (make-blsquare freq amp)

98 (make-blsquare freq amp (car opts))))

99 ((triangle) (make-bltriangle freq amp))

100 ((fm) (if (>= (length opts) 2)

101 (make-fosc freq (car opts) (cadr opts)

102 (if (>= (length opts) 3) (caddr opts) 1.0)

103 amp)

104 (error "make-oscillator: fm requires car and mod ratios" opts)))

105 (else (error "make-oscillator: unknown type" type))))))