diff options
Diffstat (limited to 'musiclib.nim')
| -rw-r--r-- | musiclib.nim | 108 |
1 files changed, 54 insertions, 54 deletions
diff --git a/musiclib.nim b/musiclib.nim index 7050dd3..4984596 100644 --- a/musiclib.nim +++ b/musiclib.nim @@ -1,68 +1,68 @@ -import std/[algorithm, math, sugar] +import std/[algorithm, math, sugar, strformat] -type Note* = tuple - len: float - octave: float - step: float - vol: float +type + OscFn* = proc (f: float, t: float): float -func n*(a, b, c, d: float = 1): Note = - (a, b, c, d) + Note* = tuple + len: float ## seconds + freq: float + vol: float + osc: OscFn -type ProcessedNote* = tuple - start: float - `end`: float - octave: float - step: float - vol: float + ProcessedNote* = tuple + start: float ## absolute time in seconds + stop: float ## absolute time in seconds + freq: float + vol: float + osc: OscFn -func process*(music: var seq[ProcessedNote], notes: openArray[Note]; m_start: float, speed: float=1, gain:float = 1) = +## give some seconds for the note to fade out +const HACK_DROPOFF_DELAY = 2.0 + +const HACK_LONGEST_NOTE = 16.0 + +func process*(music: var seq[ProcessedNote], notes: openArray[Note]; start_init: float, speed: float=1, gain:float = 1) = ## Adds a list of notes to the music list - var start = m_start + ## + ## `notes` sequence of notes with no rests in between + var start = start_init var t = start for note in notes: - let vol = note[3] - start = min(t, t + note[0] / speed) - let `end` = max(t, t + note[0] / speed) - music &= ((start, `end`, note[1], note[2], vol * gain)) - t = `end` + 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 * gain, note.osc) + t = stop -func bisect(music: openArray[ProcessedNote], x: (float, float)): int = - ## Return the index where to insert item `x` in list `music`, assuming `music` is sorted. - music.lowerBound(x, (m, key) => cmp((m[0], m[1]), key)) +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` -func freq(octave, step: float): float = - ## Returns the frequency of a note - 55 * pow(2, (octave + step / 12 - 1)) + music.lowerBound(x, (m, key) => cmp(m.start, key)) -func tone(f, t: float): float = - ## Returns the intensity of a tone of frequency f sampled at time t - # https://dsp.stackexchange.com/questions/46598/mathematical-equation-for-the-sound-wave-that-a-piano-makes - # https://youtu.be/ogFAHvYatWs?t=254 - # return int(2**13*(1+square(t, 440*2**(math.floor(5*t)/12)))) - # Y = sum([math.sin(2 * i * math.pi * t * f) * math.exp(-0.0004 * 2 * math.pi * t * f) / 2**i for i in range(1, 4)]) - # Y += Y * Y * Y - # Y *= 1 + 16 * t * math.exp(-6 * t) - let w = 2 * PI * f - var Y = 0.6 * math.sin(w * t) * math.exp(-0.001 * w * t) - Y += 0.2 * math.sin(2 * w * t) * math.exp(-0.001 * w * t) - Y += 0.05 * math.sin(3 * w * t) * math.exp(-0.001 * w * t) - Y += Y * Y * Y - Y *= 1 + 16 * t * math.exp(-6 * t) - Y +const GAIN_BIAS: float = pow(2.0, 28.0) -const bias: float = pow(2.0, 28.0) -func at*(music: openArray[ProcessedNote], t: float): int32 = +proc at*(music: openArray[ProcessedNote], t: float): int32 = ## Returns the total intensity of music sampled at time t - let i: int = music.bisect((t, pow(2.0, 31.0))) - # This is actually pretty efficient ngl - # Because people usually don't have that many overlapping notes + ## + ## assumes `music` is sorted by `.start` + + var i: int = music.bisect(t) - 1 + var ret: float = 0 - # this `32` is flaky - # maybe some notes are longer? - for j in (max(i - 32, 0) ..< i): - let m = music[j] - if m[0] + m[1] > t: - ret += m[4] * tone(freq(m[2], m[3]), t - m[0]) - int32(ret * bias) + + while i >= 0: + let m = music[i] + assert m.start <= t + if m.stop + HACK_DROPOFF_DELAY >= t: + ret += m.vol * m.osc(m.freq, t - m.start) + if m.start + HACK_LONGEST_NOTE + HACK_DROPOFF_DELAY < t: + break + i -= 1 + + int32(ret * GAIN_BIAS) |