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authorAnthony Wang2023-03-16 22:59:41 -0400
committerAnthony Wang2023-03-16 22:59:41 -0400
commit0da46c8a33e7a9b61b564cce5c4c4526fe3d84dc (patch)
tree1c3948cdb3a6cd6119f2ede76279cde26e464eba /yue.nim
parent46911993234b7c9cc07546f56843b35621b7f811 (diff)
Clean up code and rename to yue
Diffstat (limited to 'yue.nim')
-rw-r--r--yue.nim120
1 files changed, 120 insertions, 0 deletions
diff --git a/yue.nim b/yue.nim
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+++ b/yue.nim
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+import std/[algorithm, math, sugar, strformat, logging]
+
+type
+ OscFn* = proc (f: float, t: float): float
+
+ Note* = tuple
+ len: float ## seconds
+ freq: float
+ vol: float
+ osc: OscFn
+
+ ProcessedNote* = tuple
+ start: float ## absolute time in seconds
+ stop: float ## absolute time in seconds
+ freq: float
+ vol: float
+ osc: OscFn
+
+const HACK_LONGEST_NOTE = 16.0
+
+func process*(music: var seq[ProcessedNote], notes: openArray[Note]; start_init: float, speed: float=1) =
+ ## Adds a list of notes to the music list
+ ##
+ ## `notes` sequence of notes with no rests in between
+ var start = start_init
+ var t = start
+ for note in notes:
+ assert note.len >= 0.0
+ assert note.len <= HACK_LONGEST_NOTE, &"note too long: {note.len}"
+ start = t
+ let stop = t + note.len / speed
+ music &= (start, stop, note.freq, note.vol, note.osc)
+ t = stop
+
+func sortByStart*(music: var seq[ProcessedNote]) =
+ music.sort((a, b) => cmp(a.start, b.start))
+
+func bisect(music: openArray[ProcessedNote], x: float): int =
+ ## Return the index where to insert item `x` in list `music`
+ ##
+ ## assumes `music` is sorted by `.start`
+
+ music.lowerBound(x, (m, key) => cmp(m.start, key))
+
+const GAIN_BIAS: float = pow(2.0, 31.0)
+
+proc at*(music: openArray[ProcessedNote], t: float): int32 =
+ ## Returns the total intensity of music sampled at time t
+ ##
+ ## assumes `music` is sorted by `.start`
+
+ var i: int = music.bisect(t) - 1
+
+ var ret: float = 0
+
+ while i >= 0:
+ let m = music[i]
+ assert m.start <= t
+ if m.start + HACK_LONGEST_NOTE < t:
+ break
+ else:
+ ret += m.vol * m.osc(m.freq, t - m.start)
+ i -= 1
+
+ ret *= GAIN_BIAS
+
+ # clip sample
+ if ret >= int32.high.float:
+ warn(&"audio clipping at t={t}")
+ int32.high
+ elif ret <= int32.low.float:
+ warn(&"audio clipping at t={t}")
+ int32.low
+ else:
+ int32(ret)
+
+func osc_weird_pluck*(f, t: float): float =
+ # I got this as a bug
+ let w = 2 * PI * f
+ let wxt = w * t
+ let exp_swxt = math.exp(-0.001 * wxt)
+ let y0 = 0.6 * math.sin(wxt)
+ let y1 = 0.2 * math.sin(2 * wxt)
+ let y2 = 0.05 * math.sin(3 * wxt)
+ let y3 = (y0 + y1 + y2) * exp_swxt
+ let y4 = (1+y3)*y3*y3 # this line is different
+ y4 * (1 + 16 * t * math.exp(-6 * t))
+
+func osc_piano*(f, t: float): float =
+ ## Returns the intensity of a tone of frequency f sampled at time t
+ ## t starts at 0 (note start)
+ # https://dsp.stackexchange.com/questions/46598/mathematical-equation-for-the-sound-wave-that-a-piano-makes
+ # https://youtu.be/ogFAHvYatWs?t=254
+ let w = 2 * PI * f
+ let ewt = math.exp(-0.001 * w * t)
+ var Y = 0.6 * math.sin(w * t) * ewt +
+ 0.2 * math.sin(2 * w * t) * ewt +
+ 0.05 * math.sin(3 * w * t) * ewt
+
+ let Y2 = Y * (Y * Y + 1)
+ Y2 * (1 + 16 * t * math.exp(-6 * t))
+
+func osc_pulse*(f, t: float, phasedrift: float = 0.0): float =
+ let doublewidth = 1.0 / f
+ let width = doublewidth / 2
+ let phase: float = (t + doublewidth * phasedrift) mod doublewidth
+ if phase < width: 1.0 else: -1.0
+
+func osc_saw*(f,t:float, phasedrift: float = 0.0):float =
+ let doublewidth = 1.0 / f
+ let width = doublewidth / 2
+ let phase: float = (t + doublewidth * phasedrift) mod doublewidth
+ if phase < width:
+ -1.0 + 2.0 * phase / width
+ else:
+ 1.0 - 2.0 * (phase - width) / (1.0 - width)
+
+func freq*(octave, step: float): float =
+ ## Returns the frequency of a note
+ 55 * pow(2, (octave + step / 12 - 1))