Ole André Vadla Ravnås
ad7ffcdabc
Eight channels, each with its own patch and pattern on its own step clock, mixed on the audio device's thread: storage allocated once, reached through unsafe pointers, and a lock-free ring for control, so nothing under the callback allocates, retains or locks. The image performs a tune, names it, and sounds chords.
47 lines
1.5 KiB
Swift
47 lines
1.5 KiB
Swift
import Foundation
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/// Sounds arriving events: the same activity that drives a shader effect
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/// picks a degree of a pentatonic scale, so a busy target climbs. Off until
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/// asked for -- instrumentation that makes noise unbidden is not a feature.
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@MainActor
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public final class EventChime {
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public var isEnabled = false {
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didSet {
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guard isEnabled != oldValue else { return }
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if isEnabled {
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synth.start()
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synth.use(.blip, channel: chimeChannel)
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} else {
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synth.stop()
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}
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}
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}
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public let synth: Synth
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/// Semitone offsets of a minor pentatonic, spanning two octaves.
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private let degrees: [Float] = [0, 3, 5, 7, 10, 12, 15, 17, 19, 22]
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private let rootHz: Float = 196
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private let minimumSpacing: TimeInterval = 0.06
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private var lastSoundedAt: TimeInterval = 0
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/// Its own channel, so sounding events never restyles a tune's voices.
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private let chimeChannel = SynthEngine.channelCount - 1
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public init(synth: Synth = Synth()) {
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self.synth = synth
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}
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public func report(activity: Float, at now: TimeInterval = Date.timeIntervalSinceReferenceDate) {
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guard isEnabled, now - lastSoundedAt >= minimumSpacing else { return }
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lastSoundedAt = now
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let degree = degrees[min(Int(activity * Float(degrees.count)), degrees.count - 1)]
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synth.play(
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frequency: rootHz * pow(2, degree / 12),
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velocity: 0.35 + activity * 0.5,
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channel: chimeChannel)
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}
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}
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