Stream Microphone Audio from one device to another using Multipeer connectivy and EZAudio - swift

Question

[TLDR: Receiving an ASSERTION FAILURE on CABufferList.h (find error at the bottom) when trying to save streamed audio data]
I am having trouble saving microphone audio that is streamed between devices using Multipeer Connectivity. So far I have two devices connected to each other using Multipeer Connectivity and have them sending messages and streams to each other.
Finally I have the StreamDelegate method
func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
// create a buffer for capturing the inputstream data
let bufferSize = 2048
let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
defer {
buffer.deallocate()
}
var audioBuffer: AudioBuffer!
var audioBufferList: AudioBufferList!
switch eventCode {
case .hasBytesAvailable:
// if the input stream has bytes available
// return the actual number of bytes placed in the buffer;
let read = self.inputStream.read(buffer, maxLength: bufferSize)
if read < 0 {
//Stream error occured
print(self.inputStream.streamError!)
} else if read == 0 {
//EOF
break
}
guard let mData = UnsafeMutableRawPointer(buffer) else { return }
audioBuffer = AudioBuffer(mNumberChannels: 1, mDataByteSize: UInt32(read), mData: mData)
audioBufferList = AudioBufferList(mNumberBuffers: 1, mBuffers: audioBuffer)
let audioBufferListPointer = UnsafeMutablePointer<AudioBufferList>.allocate(capacity: read)
audioBufferListPointer.pointee = audioBufferList
DispatchQueue.main.async {
if self.ezRecorder == nil {
self.recordAudio()
}
self.ezRecorder?.appendData(from: audioBufferListPointer, withBufferSize: UInt32(read))
}
print("hasBytesAvailable \(audioBuffer!)")
case .endEncountered:
print("endEncountered")
if self.inputStream != nil {
self.inputStream.delegate = nil
self.inputStream.remove(from: .current, forMode: .default)
self.inputStream.close()
self.inputStream = nil
}
case .errorOccurred:
print("errorOccurred")
case .hasSpaceAvailable:
print("hasSpaceAvailable")
case .openCompleted:
print("openCompleted")
default:
break
}
}
I am getting the stream of data however when I try to save it as an audio file using EZRecorder, I get the following error message
[default] CABufferList.h:184 ASSERTION FAILURE [(nBytes <= buf->mDataByteSize) != 0 is false]:
I suspect the error could be arising when I create AudioStreamBasicDescription for EZRecorder.
I understand there may be other errors here and I appreciate any suggestions to solve the bug and improve the code. Thanks

Answer 1

EZAudio comes with TPCircularBuffer - use that.
Because writing the buffer to file is an async operation, this becomes a great use case for a circular buffer where we have one producer and one consumer.
Use the EZAudioUtilities where possible.
Update: EZRecorder write expects bufferSize to be number of frames to write and not bytes
So something like this should work:
class StreamDelegateInstance: NSObject {
private static let MaxReadSize = 2048
private static let BufferSize = MaxReadSize * 4
private var availableReadBytesPtr = UnsafeMutablePointer<Int32>.allocate(capacity: 1)
private var availableWriteBytesPtr = UnsafeMutablePointer<Int32>.allocate(capacity: 1)
private var ezRecorder: EZRecorder?
private var buffer = UnsafeMutablePointer<TPCircularBuffer>.allocate(capacity: 1)
private var inputStream: InputStream?
init(inputStream: InputStream? = nil) {
self.inputStream = inputStream
super.init()
EZAudioUtilities.circularBuffer(buffer, withSize: Int32(StreamDelegateInstance.BufferSize))
ensureWriteStream()
}
deinit {
EZAudioUtilities.freeCircularBuffer(buffer)
buffer.deallocate()
availableReadBytesPtr.deallocate()
availableWriteBytesPtr.deallocate()
self.ezRecorder?.closeAudioFile()
self.ezRecorder = nil
}
private func ensureWriteStream() {
guard self.ezRecorder == nil else { return }
// stores audio to temporary folder
let audioOutputPath = NSTemporaryDirectory() + "audioOutput2.aiff"
let audioOutputURL = URL(fileURLWithPath: audioOutputPath)
print(audioOutputURL)
// let audioStreamBasicDescription = AudioStreamBasicDescription(mSampleRate: 44100.0, mFormatID: kAudioFormatLinearPCM, mFormatFlags: kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked, mBytesPerPacket: 4, mFramesPerPacket: 1, mBytesPerFrame: 4, mChannelsPerFrame: 1, mBitsPerChannel: 32, mReserved: 1081729024)
// EZAudioUtilities.audioBufferList(withNumberOfFrames: <#T##UInt32#>,
// numberOfChannels: 1,
// interleaved: true)
// if you don't need a custom format, consider using EZAudioUtilities.m4AFormat
let format = EZAudioUtilities.aiffFormat(withNumberOfChannels: 1,
sampleRate: 44800)
self.ezRecorder = EZRecorder.init(url: audioOutputURL,
clientFormat: format,
fileType: .AIFF)
}
private func writeStream() {
let ptr = TPCircularBufferTail(buffer, availableWriteBytesPtr)
// ensure we have non 0 bytes to write - which should always be true, but you may want to refactor things
guard availableWriteBytesPtr.pointee > 0 else { return }
let framesToWrite = availableWriteBytesPtr.pointee / 4 // sizeof(float)
let audioBuffer = AudioBuffer(mNumberChannels: 1,
mDataByteSize: UInt32(availableWriteBytesPtr.pointee),
mData: ptr)
let audioBufferList = AudioBufferList(mNumberBuffers: 1, mBuffers: audioBuffer)
self.ezRecorder?.appendData(from: &audioBufferList,
withBufferSize: UInt32(framesToWrite))
TPCircularBufferConsume(buffer, framesToWrite * 4)
}
}
extension StreamDelegateInstance: StreamDelegate {
func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
switch eventCode {
case .hasBytesAvailable:
// if the input stream has bytes available
// return the actual number of bytes placed in the buffer;
guard let ptr = TPCircularBufferHead(buffer, availableReadBytesPtr) else {
print("couldn't get buffer ptr")
break;
}
let bytedsToRead = min(Int(availableReadBytesPtr.pointee), StreamDelegateInstance.MaxReadSize)
let mutablePtr = ptr.bindMemory(to: UInt8.self, capacity: Int(bytedsToRead))
let bytesRead = self.inputStream?.read(mutablePtr,
maxLength: bytedsToRead) ?? 0
if bytesRead < 0 {
//Stream error occured
print(self.inputStream?.streamError! ?? "No bytes read")
break
} else if bytesRead == 0 {
//EOF
break
}
TPCircularBufferProduce(buffer, Int32(bytesRead))
DispatchQueue.main.async { [weak self] in
self?.writeStream()
}
case .endEncountered:
print("endEncountered")
if self.inputStream != nil {
self.inputStream?.delegate = nil
self.inputStream?.remove(from: .current, forMode: .default)
self.inputStream?.close()
self.inputStream = nil
}
case .errorOccurred:
print("errorOccurred")
case .hasSpaceAvailable:
print("hasSpaceAvailable")
case .openCompleted:
print("openCompleted")
default:
break
}
}
}