將音頻轉換為 [Double] 類型的原始 PCM 數據

Question

我正在嘗試將錄制的音頻文件轉換為 [Double] 類型的原始 PCM 數據。 我找到了一種加載音頻並將其轉換為 [Float32] 類型的 PCM 數據的方法，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)))

問題是，我需要數據為 [Double] 並且 AVAudioPCMBuffer() 只知道.PCMFormatFloat32 。 有人知道解決方法嗎？ 謝謝。

Answer 1

但AVAudioFormat確實知道.PCMFormatFloat64 ：

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

也許您的意思是AVAudioPCMBuffer沒有float64ChannelData便利屬性？

沒關系，您可以使用AVAudioPCMBuffer的超類， AVAudioBuffer擁有您需要能夠獲得原始Double / Float64樣本的Float64 ：

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

全文：

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)

Answer 2

那個代碼可能不再工作了。
這是新的工作代碼。

斯威夫特 3.2

let file = try! AVAudioFile(forReading: soundFileURL)
let format = AVAudioFormat(commonFormat: .PCMFormatFloat64, sampleRate: file.fileFormat.sampleRate, channels: file.fileFormat.channelCount, interleaved: false)
let buf = AVAudioPCMBuffer(PCMFormat: format, frameCapacity: AVAudioFrameCount(file.length))
try! file.readIntoBuffer(buf)
let abl = Array(UnsafeBufferPointer(start: buf.audioBufferList, count: Int(buf.audioBufferList.pointee.mNumberBuffers)))
let buffer = audioBufferList[0].mBuffers
let mDataList = Array(UnsafeMutableRawBufferPointer(start: buffer.mData, count: Int(buffer.mDataByteSize)))

Answer 3

更新到Swift 5

        do {
            let file = try AVAudioFile(forReading: soundFileURL)
            if let format = AVAudioFormat(commonFormat: .pcmFormatFloat64, sampleRate: file.fileFormat.sampleRate, channels: file.fileFormat.channelCount, interleaved: false), let buf = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: AVAudioFrameCount(file.length)){
                try file.read(into: buf)
                let abl = Array(UnsafeBufferPointer(start: buf.audioBufferList, count: Int(buf.audioBufferList.pointee.mNumberBuffers)))

                let buffer = buf.audioBufferList[0].mBuffers
                let mDataList = Array(UnsafeMutableRawBufferPointer(start: buffer.mData, count: Int(buffer.mDataByteSize)))
            }
        } catch{
            print("Audio Error: \(error)")
        }