Generating Float32 Array (Float32 PCM data) using CMSampleBuffer - swift

Question

I get the callbacks from camera with for audio with data in the format of CMSampleBuffer but I am unable to convert this data to PCM data.
I followed the docs provided by Apple copyPCMData, UnsafeMutablePointer, AudioBufferList but all I get is 0.0 at the end.
Here is my code:
private let pcmBufferPointer = UnsafeMutablePointer<AudioBufferList>.allocate(capacity: 1024)
init(....){
//...
let unsafeRawPointer = UnsafeMutableRawPointer.allocate(byteCount: 4, alignment: 0)
let audioBuffer = AudioBuffer(mNumberChannels: 1, mDataByteSize: 4, mData: unsafeRawPointer)
let audioBufferList = AudioBufferList(mNumberBuffers: 0, mBuffers: audioBuffer)
self.pcmBufferPointer.initialize(repeating: audioBufferList, count: 1024)
}
//CMSampleBuffer obtained from AVCaptureAudioDataOutputSampleBufferDelegate
private func audioFrom(sampleBuffer: CMSampleBuffer) -> Void {
let status = CMSampleBufferCopyPCMDataIntoAudioBufferList(sampleBuffer, 0, 1024, pcmBufferPointer)
if status == 0 {
Logger.log(key: "Audio Sample Buffer Status", message: "Buffer copied to pointer")
let dataValue = pcmBufferPointer[0].mBuffers.mData!.load(as: Float32.self) //Tried with Int, Int16, Int32, Int64 and Float too
Logger.log(key: "PCM Data Value", message: "Data value : \(dataValue)") //prints 0.0
}else{
Logger.log(key: "Audio Sample", message: "Buffer allocation failed with status \(status)")
}
}

Answer 1

Finally got it working.
Had to add extra step for the conversion of AudioBufferList pointer to AudioList pointer
if status == 0 {
let inputDataPtr = UnsafeMutableAudioBufferListPointer(pcmBufferPointer)
let mBuffers : AudioBuffer = inputDataPtr[0]
if let bufferPointer = UnsafeMutableRawPointer(mBuffers.mData){
let dataPointer = bufferPointer.assumingMemoryBound(to: Int16.self)
let dataArray = Array(UnsafeBufferPointer.init(start: dataPointer, count: 1024))
pcmArray.append(contentsOf: dataArray)
}else{
Logger.log(key: "Audio Sample", message: "Failed to generate audio sample")
}
}else{
Logger.log(key: "Audio Sample", message: "Buffer allocation failed with status \(status)")
}
Above code works only for single channel PCM data. For 2 channels data refer the following GIST - https://gist.github.com/hotpaw2/ba815fc23b5d642705f2b1dedfaf0107