I want to build an iOS app (using Swift 3 and Xcode 8.2.1) that records from the microphone of an iPhone and saves the record to a .caf
file.
First, I've added the following lines to the Info.plist file of my project:
<key>NSMicrophoneUsageDescription</key>
<string>Some description to explain why access is required</string>
Then, I've created a simple UIViewController
that sets a AVAudioEngine
and install/remove an audio tap when tapping on Record
and Stop
buttons.
ViewController.swift
import UIKit
import AVFoundation
class ViewController: UIViewController {
var engine = AVAudioEngine()
var file: AVAudioFile?
var player = AVAudioPlayerNode()
override func viewDidLoad() {
super.viewDidLoad()
guard let url = urlFor(filename: "test.caf") else { return }
do {
file = try AVAudioFile(forWriting: url, settings: engine.inputNode!.inputFormat(forBus: 0).settings, commonFormat: engine.inputNode!.inputFormat(forBus: 0).commonFormat, interleaved: false)
} catch {
print("Error: \(error)")
}
engine.attach(player)
engine.connect(player, to: engine.mainMixerNode, format: engine.mainMixerNode.outputFormat(forBus: 0))
do {
try engine.start()
} catch {
print("Error: \(error)")
}
}
@IBAction func record(sender: AnyObject) {
engine.inputNode?.installTap(onBus: 0, bufferSize: 1024, format: engine.mainMixerNode.outputFormat(forBus: 0)) { (buffer, time) -> Void in
do {
try self.file?.write(from: buffer)
} catch {
print("Error: \(error)")
}
}
}
@IBAction func stop(sender: AnyObject) {
engine.inputNode?.removeTap(onBus: 0)
// Print the url of the saved file
let urls = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask)
print(urls[urls.endIndex - 1])
}
func urlFor(filename: String) -> URL? {
// Get url of saved file
if let dir = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.allDomainsMask, true).first {
let path = dir.appending(filename)
return URL(fileURLWithPath: path)
}
return nil
}
}
The app works fine on the simulator: I can record my voice, grab the url of the recorded file and test that my voice has correctly been recorded. However, the app crashes as soon as I launch it on a device (tested with an iPhone 6s on iOS 10.2.1). The console gives me the following logs:
2017-02-08 17:09:14.330151 AudioEngineSimpleApp[7100:2659416] Audio files cannot be non-interleaved. Ignoring setting AVLinearPCMIsNonInterleaved YES.
2017-02-08 17:09:14.333715 AudioEngineSimpleApp[7100:2659416] [central] 54: ERROR: [0x1b7440c40] >avae> AVAudioFile.mm:160: AVAudioFileImpl: error -54
2017-02-08 17:09:14.333796 AudioEngineSimpleApp[7100:2659416] [central] 54: ERROR: [0x1b7440c40] >avae> AVAudioFile.mm:122: ReadMagicCookie: error -50
2017-02-08 17:09:14.334369 AudioEngineSimpleApp[7100:2659416] *** Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'error -50'
This problem seems to be related to the Stack Overflow thread AVAudioPlayer working on Simulator but not on Real Device but I can't figure how to implement its response into my own code in order to solve my problem.
I've refactored my code and have replaced my old urlFor(filename: String) -> URL?
method with the following url
property:
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("test.caf")
As a result, the following code works properly on device:
import UIKit
import AVFoundation
class ViewController: UIViewController {
@IBOutlet weak var recordButton: UIButton!
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("test.caf")
//let url = URL(fileURLWithPath: NSTemporaryDirectory().appending("test.caf")) also works
var engine = AVAudioEngine()
override func viewDidLoad() {
super.viewDidLoad()
recordButton.setTitle("Record", for: .normal)
let file: AVAudioFile
do {
file = try AVAudioFile(forWriting: url, settings: engine.inputNode!.outputFormat(forBus: 0).settings)
} catch {
print("Error: \(error)")
return
}
engine.inputNode?.installTap(onBus: 0, bufferSize: 1024, format: engine.inputNode!.outputFormat(forBus: 0)) { (buffer, time) -> Void in
do {
try file.write(from: buffer)
} catch {
print("Error: \(error)")
}
}
}
@IBAction func toggleAction(_ sender: AnyObject) {
engine.isRunning ? stopRecording() : startRecording()
}
func startRecording() {
do {
// Start engine
try engine.start()
// Toggle button title
recordButton.setTitle("Stop", for: .normal)
} catch {
print("Error: \(error)")
}
}
func stopRecording() {
// Stop engine
engine.stop()
// Toggle button title
recordButton.setTitle("Record", for: .normal)
print(url)
}
}