diff options
author | Anthony Wang | 2023-03-12 17:53:37 +0000 |
---|---|---|
committer | Anthony Wang | 2023-03-12 17:53:37 +0000 |
commit | 44b8c5f7311eccb8058df27be1a4d55651580940 (patch) | |
tree | 478ff6ef7c83c0d81ae02db1cb6ec699a252ef7b /musiclib.nim | |
parent | ba1c702d34ebb9cf7971e165e8e0e96ba1a63c78 (diff) | |
parent | 5fe21ce19c52326c79c1fe09000218af66f386c5 (diff) |
Merge pull request 'Nim port' (#1) from iacore/Lambeat:main into main
Reviewed-on: https://git.exozy.me/a/Lambeat/pulls/1
Diffstat (limited to 'musiclib.nim')
-rw-r--r-- | musiclib.nim | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/musiclib.nim b/musiclib.nim new file mode 100644 index 0000000..c21cb95 --- /dev/null +++ b/musiclib.nim @@ -0,0 +1,75 @@ +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) |