Stream audio from microphone via bluetooth to another iPhone

Question

I am trying to take incoming microphone audio and stream it to another iPhone. Basically a phone call but via bluetooth. I have the audio coming in via AVAudioRecorder:

func startRecording() {
    audioRecorder = nil
    let audioSession:AVAudioSession = AVAudioSession.sharedInstance()
    audioSession.setCategory(AVAudioSessionCategoryRecord, error: nil)

    var recordSettings:NSMutableDictionary = NSMutableDictionary(capacity: 10)
    recordSettings.setObject(NSNumber(integerLiteral: kAudioFormatLinearPCM), forKey: AVFormatIDKey)
    recordSettings.setObject(NSNumber(float: 44100.0), forKey: AVSampleRateKey)
    recordSettings.setObject(NSNumber(int: 2), forKey: AVNumberOfChannelsKey)
    recordSettings.setObject(NSNumber(int: 16), forKey: AVLinearPCMBitDepthKey)
    recordSettings.setObject(NSNumber(bool: false), forKey: AVLinearPCMIsBigEndianKey)
    recordSettings.setObject(NSNumber(bool: false), forKey: AVLinearPCMIsFloatKey)

    soundPath = documentsDirectory.stringByAppendingPathComponent("record.caf")
    refURL = NSURL(fileURLWithPath: soundPath as String)
    var error:NSError?

    audioRecorder = AVAudioRecorder(URL: refURL, settings: recordSettings as [NSObject : AnyObject], error: &error)

    if audioRecorder.prepareToRecord() == true {
        audioRecorder.meteringEnabled = true
        audioRecorder.record()
    } else {
        println(error?.localizedDescription)
    }
}

Then I tried using StreamReader from HERE - StreamReader from @martin-r

Using:

if let aStreamReader = StreamReader(path: documentsDirectory.stringByAppendingPathComponent("record.caf")) {
                while let line = aStreamReader.nextLine() {
                    let dataz = line.dataUsingEncoding(NSUTF8StringEncoding)
                    println (line)

Then send the data to another device using:

self.appDelegate.mpcDelegate.session.sendData(data: NSData!, toPeers: [AnyObject]!, withMode: MCSessionSendDataMode, error: NSErrorPointer )

I convert line to NSData, then using a dispatch_after 0.5 seconds running constantly, I send it to another device via bluetooth.

It does not seem to work and I don't think this is a practical way of doing it. I have done numerous searches and haven't seen much on streaming data via bluetooth. The key word streaming (understandably) sends me to pages about server streaming.

My question is, how can I take audio from a microphone and send it to another iPhone via bluetooth? I have the bluetooth part all set up and it works great. My question is very similar to THIS except with iPhones and Swift - I want to have a phone call via bluetooth.

Thank you in advance.

Answer 1

To simultaneously record and redirect output you need to use the category AVAudioSessionCategoryMultiRoute.

Here's the link to the categories list: https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVAudioSession_ClassReference/#//apple_ref/doc/constant_group/Audio_Session_Categories

If all else fails you can use a pre-made solution: http://audiob.us

It has an API that lets you integrate audio streaming from one app to another: https://developer.audiob.us/

It supports multiple output endpoints.

Hope this helps.