Trouble streaming microphone audio between devices using Multipeer Connectivity

Question

I have set up the basics of Multipeer Connectivity successfully and my two devices recognize and connect to each other as peers. However, I am having trouble streaming and playing audio using AVAudioPlayerNode. I have a StartRecording() function called when a button is toggled, and it should open and close the OutputStream.

My general understanding is that you need to create an AVAudioEngine, attach an AVAudioPlayerNode, connect the AVAudioPlayerNode to the main mixer or output node (?). Then, from the sending device, start an outputStream, and installTap() on the Audio Engine's inputNode, which will continuously send the bytes converted from AVAudioPCMBuffer.

In the Multipeer functions, once stream data is received, I set the ViewController's inputStream which I think is handled using the StreamDelegate functions. The incoming bytes should then be handled (if there is space). The code seems to be functional, but .hasBytesAvailable is rarely called. I have microphone access enabled on both devices too.

Since it's hard to fit all the code in this post, I have created a public gist with relevant files. Here are the relevant parts from 3 main classes : ViewController.swift, MultipeerHandler.swift, StreamHelper.swift:

In ViewController.swift:

override func viewDidLoad() {
    super.viewDidLoad()
    configureAudioSession()
    audioEngine = AVAudioEngine()
    inputNode = audioEngine.inputNode
    audioFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 8000, channels: 1, interleaved: false)
    multipeerSetup()
    viewSetup()
}

private func configureAudioSession() {
    do {
        try audioSession.setCategory(.playAndRecord, options: .defaultToSpeaker)
        try audioSession.setMode(.voiceChat)
        try audioSession.setActive(true)

        audioSession.requestRecordPermission() { [unowned self] (allowed: Bool) -> Void in
            DispatchQueue.main.async {
                if allowed {
                    print("allowed")
                }
            }
        }
    } catch { }
}

@objc func startRecording() throws {
    // start streaming
    if !(self.isRecording) {
        audioEngine.stop()
        let inputFormat = inputNode.inputFormat(forBus: 0)

        audioEngine.attach(audioPlayer)
        audioEngine.connect(audioPlayer, to: mainMixer, format: audioFormat)
        // audioEngine.connect(audioPlayer, to: audioPlayer.outputNode, format: inputFormat)

        do {
            if multipeerHandler.session.connectedPeers.count > 0 {
                if outputStream != nil {
                    outputStream = nil
                }

                outputStream = try multipeerHandler.session.startStream(withName: "voice", toPeer: multipeerHandler.session.connectedPeers[0])
                outputStream.schedule(in: RunLoop.main, forMode: .default)
                outputStream.delegate = self
                outputStream.open()

                inputNode.installTap(onBus: 0, bufferSize: AVAudioFrameCount(inputFormat.sampleRate/10), format: inputFormat) { (buffer: AVAudioPCMBuffer, when: AVAudioTime) in

                    let convertedFrameCount = AVAudioFrameCount((Double(buffer.frameLength) / inputFormat.sampleRate) * inputFormat.sampleRate)
                    guard let pcmBuffer = AVAudioPCMBuffer(pcmFormat: inputFormat, frameCapacity: convertedFrameCount) else {
                        print("cannot make pcm buffer")
                        return
                    }

                    print("\(#line)")

                    let bytes = StreamHelper.copyAudioBufferBytes(pcmBuffer)
                    if(self.outputStream.hasSpaceAvailable){
                        self.outputStream.write(bytes, maxLength: bytes.count)
                        print("\(#line)")
                    }
                }
                audioEngine.prepare()
                try audioEngine.start()

            } else {
                print("no peers to connect to")
            }
        } catch let error {
            print(error.localizedDescription)

        }
        self.isRecording = true
    } else {
        // stop streaming
        inputNode.removeTap(onBus: 0)
        self.isRecording = false
    }
}

In MultipeerHelper.swift:

func session(_ session: MCSession, didReceive stream: InputStream, withName streamName: String, fromPeer peerID: MCPeerID) {
    print("didReceiveStream")
    if streamName == "voice" {
        print(#line)
        viewController.inputStream = stream
        viewController.inputStream.delegate = viewController
        viewController.inputStream.schedule(in: RunLoop.main, forMode: .default)
        viewController.inputStream.open()
    }
}

Also, it is important to note that I have found a lot of similar posts but they're somewhat old. Here are some of the sources I used to understand what's going on:

Once again, I have posted a public gist for this inquiry. Any help would be greatly appreciated.

Trouble streaming microphone audio between devices using Multipeer Connectivity

0 Answers0