140 lines
5.2 KiB
Swift
140 lines
5.2 KiB
Swift
// Copyright (C) 2026 ysicing
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// SPDX-License-Identifier: AGPL-3.0-or-later
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import AVFoundation
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import Localization
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public enum RestSound: String, CaseIterable, Identifiable, Sendable {
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case off, white, pink, rain
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public var id: String { rawValue }
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var title: String {
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switch self {
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case .off: tr("关闭")
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case .white: tr("白噪音")
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case .pink: tr("粉红噪音")
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case .rain: tr("雨声")
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}
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}
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}
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/// 实时生成采样，无文件、下载或麦克风访问。render block 内不分配内存，也不访问 UI 状态。
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@MainActor
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final class RestSoundPlayer {
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private var engine: AVAudioEngine?
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private(set) var playing: RestSound = .off
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/// 启动失败后短暂冷却；调用方每秒同步一次，不能每秒重建引擎。
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private var failed: RestSound?
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private var retryAfter: UInt64?
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private var configurationObserver: NSObjectProtocol?
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private let startEngine: (AVAudioEngine) throws -> Void
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private let clock: () -> UInt64
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init(startEngine: @escaping (AVAudioEngine) throws -> Void = { try $0.start() },
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clock: @escaping () -> UInt64 = { RestClock.now() }) {
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self.startEngine = startEngine
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self.clock = clock
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}
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func play(_ sound: RestSound) {
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guard sound != playing else { return }
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if sound == failed, let retryAfter, clock() < retryAfter { return }
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stop()
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guard sound != .off else { return }
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let engine = AVAudioEngine()
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let format = AVAudioFormat(standardFormatWithSampleRate: 44_100, channels: 2)!
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let node = makeNoiseSourceNode(format: format, mode: sound)
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engine.attach(node)
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engine.connect(node, to: engine.mainMixerNode, format: format)
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engine.mainMixerNode.outputVolume = 0.16
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do {
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try startEngine(engine)
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self.engine = engine
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playing = sound
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// 切换耳机等输出设备时系统会停止引擎；按新配置重建，否则本次休息剩余时间都没有声音。
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configurationObserver = NotificationCenter.default.addObserver(
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forName: .AVAudioEngineConfigurationChange, object: engine, queue: .main) { [weak self] _ in
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MainActor.assumeIsolated {
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guard let self else { return }
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let current = self.playing
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self.stop()
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self.play(current)
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}
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}
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} catch {
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engine.stop()
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failed = sound
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retryAfter = clock() + 10_000_000_000
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}
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}
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func stop() {
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if let configurationObserver { NotificationCenter.default.removeObserver(configurationObserver) }
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configurationObserver = nil
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engine?.stop()
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engine = nil
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playing = .off
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failed = nil
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retryAfter = nil
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}
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}
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/// AVAudioSourceNode 在音频线程调用此闭包；在非隔离函数中创建，避免继承播放器的 MainActor。
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nonisolated private func makeNoiseSourceNode(format: AVAudioFormat, mode: RestSound) -> AVAudioSourceNode {
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let generator = NoiseGenerator(mode: mode)
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return AVAudioSourceNode(format: format) { _, _, frameCount, audioBufferList in
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let buffers = UnsafeMutableAudioBufferListPointer(audioBufferList)
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for frame in 0..<Int(frameCount) {
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let sample = generator.next()
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for buffer in buffers {
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buffer.mData!.assumingMemoryBound(to: Float.self)[frame] = sample
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}
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}
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return noErr
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}
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}
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/// 单个 source node 的渲染回调独占采样状态，不向其他线程暴露。
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nonisolated private final class NoiseGenerator {
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let mode: RestSound
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private var seed: UInt64 = 0x9E3779B97F4A7C15
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private var lowA: Float = 0
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private var pink0: Float = 0
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private var pink1: Float = 0
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private var pink2: Float = 0
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private var pink3: Float = 0
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private var pink4: Float = 0
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private var pink5: Float = 0
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private var pink6: Float = 0
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private var drops: Float = 0
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init(mode: RestSound) { self.mode = mode }
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func next() -> Float {
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seed ^= seed << 13
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seed ^= seed >> 7
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seed ^= seed << 17
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let white = Float(seed & 0xFFFF) / 32767.5 - 1
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switch mode {
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case .off: return 0
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case .white: return white * 0.35
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case .pink:
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// Paul Kellett 的 pink-noise 滤波系数；多极点近似 1/f 频谱。
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// https://www.musicdsp.org/en/latest/Filters/76-pink-noise-filter.html
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pink0 = 0.99886 * pink0 + white * 0.0555179
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pink1 = 0.99332 * pink1 + white * 0.0750759
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pink2 = 0.96900 * pink2 + white * 0.1538520
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pink3 = 0.86650 * pink3 + white * 0.3104856
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pink4 = 0.55000 * pink4 + white * 0.5329522
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pink5 = -0.7616 * pink5 - white * 0.0168980
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let sample = pink0 + pink1 + pink2 + pink3 + pink4 + pink5 + pink6 + white * 0.5362
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pink6 = white * 0.115926
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return sample * 0.11
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case .rain:
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lowA += 0.035 * (white - lowA)
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if seed & 0x1FFF == 0 { drops = 0.75 }
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drops *= 0.998
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return lowA * 0.7 + white * drops * 0.25
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}
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}
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}
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