Convert AVAudioPCMBuffer to NSData and vice versa

Question

How to convert AVAudioPCMBuffer to NSData ? If you need to do it like

 let data = NSData(bytes: buffer.floatChannelData, length: bufferLength) 

then how to calculate bufferLength ?

And how to convert NSData to AVAudioPCMBuffer ?

Answer 1

The buffer length is frameCapacity * bytesPerFrame. Here are the functions that can convert between NSData and AVAudioPCMBuffer.

 func toNSData(PCMBuffer: AVAudioPCMBuffer) -> NSData { let channelCount = 1 // given PCMBuffer channel count is 1 var channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: channelCount) var ch0Data = NSData(bytes: channels[0], length:Int(PCMBuffer.frameCapacity * PCMBuffer.format.streamDescription.memory.mBytesPerFrame)) return ch0Data } func toPCMBuffer(data: NSData) -> AVAudioPCMBuffer { let audioFormat = AVAudioFormat(commonFormat: AVAudioCommonFormat.PCMFormatFloat32, sampleRate: 8000, channels: 1, interleaved: false) // given NSData audio format var PCMBuffer = AVAudioPCMBuffer(PCMFormat: audioFormat, frameCapacity: UInt32(data.length) / audioFormat.streamDescription.memory.mBytesPerFrame) PCMBuffer.frameLength = PCMBuffer.frameCapacity let channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: Int(PCMBuffer.format.channelCount)) data.getBytes(UnsafeMutablePointer<Void>(channels[0]) , length: data.length) return PCMBuffer }