ios - 将音频转换为 [Double] 类型的原始 PCM 数据

Question

我正在尝试将录制的音频文件转换为 [Double] 类型的原始 PCM 数据。我找到了一种方法来加载音频并将其转换为 [Float32] 类型的 PCM 数据，如下所示:

    // load audio from path
    let file = try! AVAudioFile(forReading: self.soundFileURL)
    // declare format
    let format = AVAudioFormat(commonFormat: .PCMFormatFloat32, sampleRate: file.fileFormat.sampleRate, channels: 1, interleaved: false)
    // initialize audiobuffer with the length of the audio file
    let buf = AVAudioPCMBuffer(PCMFormat: format, frameCapacity: UInt32(file.length))
    // write to file
    try! file.readIntoBuffer(buf)
    // copy to array
    let floatArray = Array(UnsafeBufferPointer(start: buf.floatChannelData[0], count:Int(buf.frameLength)))

问题是，我需要作为 [Double] 的数据，而 AVAudioPCMBuffer() 只知道 .PCMFormatFloat32。有人知道解决方法吗？谢谢。

Answer 1

但是AVAudioFormat确实知道.PCMFormatFloat64:

let format = AVAudioFormat(commonFormat: .PCMFormatFloat64, sampleRate: file.fileFormat.sampleRate, channels: 1, interleaved: false)

也许你的意思是 AVAudioPCMBuffer 没有 float64ChannelData 便利属性？

没关系，你可以使用 AVAudioPCMBuffer 的父类(super class)，AVAudioBuffer 拥有你需要的一切，能够获得原始的 Double/Float64 示例:

let abl = buf.audioBufferList.memory
let doubles = UnsafePointer<Double>(abl.mBuffers.mData)
doubles[0] // etc...

完整:

let file = try! AVAudioFile(forReading: self.soundFileURL)
let format = AVAudioFormat(commonFormat: .PCMFormatFloat64, sampleRate: file.fileFormat.sampleRate, channels: 1, interleaved: false)

let buf = AVAudioPCMBuffer(PCMFormat: format, frameCapacity: UInt32(file.length))
try! file.readIntoBuffer(buf)
let abl = buf.audioBufferList.memory
let doubles = UnsafePointer<Float64>(abl.mBuffers.mData)