Swift中的AudioBufferList分配

Question

我正在努力学习这个API和Swift中的语法

audioBufferList = AudioBufferList(mNumberBuffers: 2, mBuffers: (AudioBuffer))

我不知道带()的(AudioBuffer)是什么意思？有什么想法吗?我该如何初始化它？这是来自标题的：

  public struct AudioBufferList {

      public var mNumberBuffers: UInt32
      public var mBuffers: (AudioBuffer) // this is a variable length array of mNumberBuffers elements
      public init()
      public init(mNumberBuffers: UInt32, mBuffers: (AudioBuffer))
 }

Answer 1

这里有一种初始化AudioBufferList的方法，使用一个空的单声道缓冲区数组，您可以将其传递给音频单元调用，如AudioUnitRender()，然后根据需要分配和填充缓冲区：

var bufferList = AudioBufferList(
        mNumberBuffers: 1,
        mBuffers: AudioBuffer(
            mNumberChannels: UInt32(1),
            mDataByteSize: 1024,
            mData: nil))

Answer 2

通过使用AVAudioPCMBuffer类，通过如下方式解决了这个问题：

import AVFoundation

// noninterleaved stereo data
let processingFormat = AVAudioFormat(
  commonFormat: .pcmFormatFloat32,
  sampleRate: 44100,
  channels: 2,
  interleaved: false
)!

// this line also creates AudioBufferList instance.
let buffer = AVAudioPCMBuffer(
  pcmFormat: processingFormat,
  frameCapacity: 1024)!
// this line updates mDataByteSize properties
buffer.frameLength = 1024

let bufferList: UnsafePointer<AudioBufferList> = buffer.audioBufferList

print(bufferList.pointee) // Prints: AudioBufferList(mNumberBuffers: 2, mBuffers: __C.AudioBuffer(mNumberChannels: 1, mDataByteSize: 4096, mData: Optional(0x00007ff253840e00)))