如果不在Float，Int16或Int32中，如何访问AVAudioPCMBuffer通道数据？

Question

我正在使用那些NSData到PCMBuffer函数，一旦它尝试获取指向浮动通道数据（可变通道）的指针，就不能将其作为Float64，或者我也尝试了其他格式，并且没有输入浮动频道数据。它给我返回错误：

“致命错误：UnsafeBufferPointer的起始位置为零，且计数为非零”

任何帮助或见识都会有用。

func toPCMBuffer(data: NSData) -> AVAudioPCMBuffer {
let audioFormat = AVAudioFormat(commonFormat: AVAudioCommonFormat.pcmFormatFloat64, sampleRate: 48000, channels: 2, interleaved: true)  // given NSData audio format

        let PCMBuffer = AVAudioPCMBuffer(pcmFormat: audioFormat!, frameCapacity: UInt32(data.length) / audioFormat!.streamDescription.pointee.mBytesPerFrame)
        PCMBuffer!.frameLength = PCMBuffer!.frameCapacity
        let channels = UnsafeBufferPointer(start: PCMBuffer?.floatChannelData, count:2)
        data.getBytes(UnsafeMutableRawPointer(channels[0]) , length: data.length/8)
        data.getBytes(UnsafeMutableRawPointer(channels[1]) , length: data.length/8)
        return PCMBuffer!
}