Styjun

Currently, I'm getting an EXC_BAD_ACCESS error on the audio thread, and I'm trying to deduce what is going wrong.

When converting .wav file data from Data to an AVAudioPCMBuffer, do I need to strip the RIFF header first?

import AVFoundation

public class Player : NSObject 
 let engine = AVAudioEngine()

 public override init() 
 super.init()
 do 
 let _ = engine.mainMixerNode
 try engine.start()
 catch 
 print("Player error: (error)")
 
 

 @objc public func play(_ data: Data) 
 let format = AVAudioFormat(commonFormat: .pcmFormatInt16, sampleRate: 48000, channels: 2, interleaved: true)!
 let buffer = data.toPCMBuffer(format: format)!

 let player = AVAudioPlayerNode()
 engine.attach(player)
 engine.connect(player, to: engine.mainMixerNode, format: nil)

 player.scheduleBuffer(buffer, at: nil, completionCallbackType: .dataPlayedBack) 
 callbackType in
 // Nothing in here.
 
 player.play()
 

Here's the toPCMBuffer extension:

// Taken from: https://stackoverflow.com/a/52731480/2228559
extension Data 
 func toPCMBuffer(format: AVAudioFormat) -> AVAudioPCMBuffer? 
 let streamDesc = format.streamDescription.pointee
 let frameCapacity = UInt32(count) / streamDesc.mBytesPerFrame
 guard let buffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: frameCapacity) else return nil 

 buffer.frameLength = buffer.frameCapacity
 let audioBuffer = buffer.audioBufferList.pointee.mBuffers

 withUnsafeBytes addr in
 audioBuffer.mData?.copyMemory(from: addr, byteCount: Int(audioBuffer.mDataByteSize))
 

 return buffer
 

Note: I cannot use AVAudioFile because the .wav file data is loaded over-the-wire.

IDK, but my mac crashes if I play interleaved AVAudioPCMBuffers, and garbled audio if they're not float data, so you could convert to non-interleaved float data:

@objc public func play(_ data: Data) 
 let sampleRate: Double = 48000

 let interleavedFormat = AVAudioFormat(commonFormat: .pcmFormatInt16, sampleRate: sampleRate, channels: 2, interleaved: true)!
 let interleavedBuffer = data.toPCMBuffer(format: interleavedFormat)!

 let nonInterleavedFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: sampleRate, channels: 2, interleaved: false)!
 let nonInterleavedBuffer = AVAudioPCMBuffer(pcmFormat: nonInterleavedFormat, frameCapacity: interleavedBuffer.frameCapacity)!
 nonInterleavedBuffer.frameLength = interleavedBuffer.frameLength

 let converter = AVAudioConverter(from: interleavedFormat, to: nonInterleavedFormat)!
 try! converter.convert(to: nonInterleavedBuffer, from: interleavedBuffer)

 let player = AVAudioPlayerNode()

 engine.attach(player)
 engine.connect(player, to: engine.mainMixerNode, format: nil)

 player.scheduleBuffer(nonInterleavedBuffer, at: nil, completionCallbackType: .dataPlayedBack) 
 callbackType in
 // Nothing in here.
 

 player.play()


extension Data 
 func toPCMBuffer(format: AVAudioFormat) -> AVAudioPCMBuffer? 
 assert(format.isInterleaved)

 let streamDesc = format.streamDescription.pointee
 let frameCapacity = UInt32(count) / streamDesc.mBytesPerFrame
 guard let buffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: frameCapacity) else return nil 

 buffer.frameLength = buffer.frameCapacity

 let b = UnsafeMutableBufferPointer(start: buffer.int16ChannelData![0], count: buffer.stride * Int(frameCapacity))
 let bytesCopied = self.copyBytes(to: b)
 assert(bytesCopied == count)

 return buffer