I have some NSSound objects that I'd like to convert to AVAudioPlayer instances. I have file paths (NSURLs) associated with the NSSound objects, but the original file may not exist. Here is what I have so far:
class SoundObj: NSObject {
var path: NSURL?
var sound: NSSound?
var player: AVAudioPlayer
}
let aSound = SoundObj()
aSound.path = NSURL(fileURLWithPath: "file:///path/to/sound.m4a")
aSound.sound = NSSound(contentsOfURL: aSound.path)!
do {
try aSound.player = AVAudioPlayer(contentsOfURL: aSound.path)
} catch {
// perhaps use AVAudioPlayer(data: ...)?
}
How do I convert an NSSound object to an AVAudioPlayer instance?
So I didn't see a public interface to get the URL from an NSSound object, so I went digging through the private headers to see what I could find. Turns out there are private instance method url and _url which return the URL of an NSSound. Presumably these are getters for an NSURL ivar or property.
With Objective-C this would be easy: we would just add the methods to a new interface or extension. With pure Swift things are a little trickier, and we need to expose the accessor via an Objective-C protocol:
#objc protocol NSSoundPrivate {
var url: NSURL? { get }
}
Since url is an instance method, you may get better results with func url() -> NSURL? instead of using a variable. Your milage may vary: using a var to emulate the behavior of a read-only property seemed to work for me.
I wrote a new convenience initializer in an extension on AVAudioPlayer:
extension AVAudioPlayer {
convenience init?(sound: NSSound) throws {
let privateSound = unsafeBitCast(sound, NSSoundPrivate.self)
guard let url = privateSound.url else { return nil }
do {
try self.init(contentsOfURL: url)
} catch {
throw error
}
}
}
Usage:
let url = NSURL(...)
if let sound = NSSound(contentsOfURL: url, byReference: true) {
do {
let player = try AVAudioPlayer(sound: sound)
player?.play()
} catch {
print(error)
}
}
After attempting to find anything related to NSData in the ivars, instance methods, and properties of an NSSound, I have come to the conclusion that the data portion of whatever you use to initialize an NSSound is obfuscated somewhere in the implementation of the class, and is not available like the URL is.
Related
I'm a student studying iOS development currently working on a simple AI project that utilizes SNAudioStreamAnalyzer to classify an incoming audio stream from the device's microphone. I can start the stream and analyze audio no problem, but I've noticed I can't seem to get my app to stop analyzing and close the audio input stream when I'm done. At the beginning, I initialize the audio engine and create the classification request like so:
private func startAudioEngine() {
do {
// start the stream of audio data
try audioEngine.start()
let snoreClassifier = try? SnoringClassifier2_0().model
let classifySoundRequest = try audioAnalyzer.makeRequest(snoreClassifier)
try streamAnalyzer.add(classifySoundRequest,
withObserver: self.audioAnalyzer)
} catch {
print("Unable to start AVAudioEngine: \(error.localizedDescription)")
}
}
After I'm done classifying my audio stream, I attempt to stop the audio engine and close the stream like so:
private func terminateNight() {
streamAnalyzer.removeAllRequests()
audioEngine.stop()
stopAndSaveNight()
do {
let session = AVAudioSession.sharedInstance()
try session.setActive(false)
} catch {
print("unable to terminate audio session")
}
nightSummary = true
}
However, after I call the terminateNight() function my app will continue using the microphone and classifying the incoming audio. Here's my SNResultsObserving implementation:
class AudioAnalyzer: NSObject, SNResultsObserving {
var prediction: String?
var confidence: Double?
let snoringEventManager: SnoringEventManager
internal init(prediction: String? = nil, confidence: Double? = nil, snoringEventManager: SnoringEventManager) {
self.prediction = prediction
self.confidence = confidence
self.snoringEventManager = snoringEventManager
}
func makeRequest(_ customModel: MLModel? = nil) throws -> SNClassifySoundRequest {
if let model = customModel {
let customRequest = try SNClassifySoundRequest(mlModel: model)
return customRequest
} else {
throw AudioAnalysisErrors.ModelInterpretationError
}
}
func request(_ request: SNRequest, didProduce: SNResult) {
guard let classificationResult = didProduce as? SNClassificationResult else { return }
let topClassification = classificationResult.classifications.first
let timeRange = classificationResult.timeRange
self.prediction = topClassification?.identifier
self.confidence = topClassification?.confidence
if self.prediction! == "snoring" {
self.snoringEventManager.snoringDetected()
} else {
self.snoringEventManager.nonSnoringDetected()
}
}
func request(_ request: SNRequest, didFailWithError: Error) {
print("ended with error \(didFailWithError)")
}
func requestDidComplete(_ request: SNRequest) {
print("request finished")
}
}
It was my understanding that upon calling streamAnalyzer.removeAllRequests() and audioEngine.stop() the app would stop streaming from the microphone and call the requestDidComplete function, but this isn't the behavior I'm getting. Any help is appreciated!
From OP's edition:
So I've realized it was a SwiftUI problem. I was calling the startAudioEngine() function in the initializer of the view it was declared on. I thought this would be fine, but since this view was embedded in a parent view when SwiftUI updated the parent it was re-initializing my view and as such calling startAudioEngine() again. The solution was to call this function in on onAppear block so that it activates the audio engine only when the view appears, and not when SwiftUI initializes it.
I don't believe you should expect to receive requestDidComplete due to removing a request. You'd expect to receive that when you call completeAnalysis.
I'm trying to test how my App responds to different AVFoundation configurations. I'm using the techniques described in the WWDC video 'Engineering for Testability.'
I created a protocol to represent the pieces of an AVCaptureDevice that my app uses.
public protocol AVCaptureDeviceProperties: class {
//MARK: Properties I use and need to test
var position: AVCaptureDevice.Position { get }
var focusMode: AVCaptureDevice.FocusMode { get set }
var exposureMode: AVCaptureDevice.ExposureMode { get set }
var whiteBalanceMode: AVCaptureDevice.WhiteBalanceMode { get set }
//MARK: Functions I use use and need to test
func lockForConfiguration() throws
func unlockForConfiguration()
func isFocusModeSupported(_ focusMode: AVCaptureDevice.FocusMode) -> Bool
func isExposureModeSupported(_ exposureMode: AVCaptureDevice.ExposureMode) -> Bool
func isWhiteBalanceModeSupported(_ whiteBalanceMode: AVCaptureDevice.WhiteBalanceMode) -> Bool
}
I have an extension that makes AVCaptureDevice conform to my protocol.
extension AVCaptureDevice: AVCaptureDeviceProperties {
//Don't need anything because AVCaptureDevice already has implementations of all the properties and functions I use.
}
I can now make an object for myself where I can configure all the properties for different test cases. Works great!
However, I need to take it another step further and get a mock AVCaptureDeviceInput object. This object only has one initializer that takes a AVCaptureDevice but I want to be able to mock initialize with my protocol type. So far I have this:
extension AVCaptureDeviceInput {
convenience init?(device: AVCaptureDeviceProperties) throws {
guard let downcast = device as? AVCaptureDevice else {
return nil
}
try self.init(device: downcast)
}
}
However, I will never get a successful initialization with a mock object that conforms to my protocol. How to I solve this problem so I can test?
I'm trying to use Apple's AVMIDIPlayer object for playing a MIDI file. It seems easy enough in Swift, using the following code:
let midiFile:NSURL = NSURL(fileURLWithPath:"/path/to/midifile.mid")
var midiPlayer: AVMIDIPlayer?
do {
try midiPlayer = AVMIDIPlayer(contentsOf: midiFile as URL, soundBankURL: nil)
midiPlayer?.prepareToPlay()
} catch {
print("could not create MIDI player")
}
midiPlayer?.play {
print("finished playing")
}
And it plays for about 0.05 seconds. I presume I need to frame it in some kind of loop. I've tried a simple solution:
while stillGoing {
midiPlayer?.play {
let stillGoing = false
}
}
which works, but ramps up the CPU massively. Is there a better way?
Further to the first comment, I've tried making a class, and while it doesn't flag any errors, it doesn't work either.
class midiPlayer {
var player: AVMIDIPlayer?
func play(file: String) {
let myURL = URL(string: file)
do {
try self.player = AVMIDIPlayer.init(contentsOf: myURL!, soundBankURL: nil)
self.player?.prepareToPlay()
} catch {
print("could not create MIDI player")
}
self.player?.play()
}
func stop() {
self.player?.stop()
}
}
// main
let myPlayer = midiPlayer()
let midiFile = "/path/to/midifile.mid"
myPlayer.play(file: midiFile)
You were close with your loop. You just need to give the CPU time to go off and do other things instead of constantly checking to see if midiPlayer is finished yet. Add a call to usleep() in your loop. This one checks every tenth of a second:
let midiFile:NSURL = NSURL(fileURLWithPath:"/Users/steve/Desktop/Untitled.mid")
var midiPlayer: AVMIDIPlayer?
do {
try midiPlayer = AVMIDIPlayer(contentsOfURL: midiFile, soundBankURL: nil)
midiPlayer?.prepareToPlay()
} catch {
print("could not create MIDI player")
}
var stillGoing = true
while stillGoing {
midiPlayer?.play {
print("finished playing")
stillGoing = false
}
usleep(100000)
}
You need to ensure that the midiPlayer object exists until it's done playing. If the above code is just in a single function, midiPlayer will be destroyed when the function returns because there are no remaining references to it. Typically you would declare midiPlayer as a property of an object, like a subclassed controller.
Combining Brendan and Steve's answers, the key is sleep or usleep and sticking the play method outside the loop to avoid revving the CPU.
player?.play({return})
while player!.isPlaying {
sleep(1) // or usleep(10000)
}
The original stillGoing value works, but there is also an isPlaying method.
.play needs something between its brackets to avoid hanging forever after completion.
Many thanks.
I'm trying to access an application delegate from SDK that does not know the class name of the application delegate. I mean that my SDK doesn't know what class will be an application delegate in a basic project. So I find a class that conforms to the protocol UIApplicationDelegate.
let numberOfClasses: UnsafeMutablePointer<UInt32> = UnsafeMutablePointer<UInt32>.alloc(0)
let classes = objc_copyClassList(numberOfClasses)
var appDelegateClass: AnyClass? = nil
for i in 0...Int(numberOfClasses.memory) {
if class_conformsToProtocol(classes[i], UIApplicationDelegate.self) {
appDelegateClass = classes[i]
}
}
But the result has "type" "AnyClass?". The following code results getting an error "'applicationDelegateClass' is not a type":
if let applicationDelegateClass = appDelegateClass {
if let delegate = UIApplication.sharedApplication().delegate as? applicationDelegateClass.self { }
}
How could I solve it?
I actually shouldn't use the specific application delegate class. The right code:
if let delegate = UIApplication.sharedApplication().delegate! as? UIApplicationDelegate {}
here is my code (Swift):
import UIKit
import AVFoundation
class PlaySoundViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
if var filePath = NSBundle.mainBundle().pathForResource("movie_quote",ofType: "mp3"){
var filePathUrl = NSURL.fileURLWithPath(filePath)
AVAUdioPlayer audioPlayer = AVAudioPlayer(contentsOfURL:filePathUrl) throws
}
else{
print("filePath is empty")
}
}
#IBAction func playSlowAudio(sender: UIButton) {
}
func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
this is the method I found on my "Documentation and API References" to play audio:
``
initWithContentsOfURL:error:
init(contentsOfURL url: NSURL) throws
So, I return a String as source path, then conver it to NSURL. Now i want to play the audio but the method I am using needs to throw the error and handle it. How should I throw and handle the error ?
Swift 2.0
AVAudioPlayer will throw an exception if its initializer fails. Catch the error by wrapping its initialization in a do/catch clause.
do {
let audioPlayer = try AVAudioPlayer(contentsOfURL: filePathUrl)
// use audioPlayer
} catch {
// handle error
}
As you can see, the keyword try is inserted before any method call that can throw exceptions. As long as the try statement doesn't throw, you can continue your code as normal. If the try statement does throw, you program will jump to the catch clause.
Examining the error
If you'd like to examine the error, you can convert it to an NSError by writing your catch statement like so (as seen in Apple's Objective-C/Swift Interoperability Docs):
do {
let audioPlayer = try AVAudioPlayer(contentsOfURL: filePathUrl)
// use audioPlayer
} catch let error as NSError {
// error is now an NSError instance; do what you will
}
Converting to NSError is only necessary if you want to examine an error thrown by one of Apple's Cocoa objects. Native Swift code, throwing native ErrorType errors, require no conversion.
I recommend you read Apple's new docs on error handling in Swift.
Swift 1.2
If you are using Swift 1.2, then there is no error handling available. Instead, AVAudioPlayer's initialization method will fail and return nil.
If you are using Swift 1.2, I would recommend initializing the audio player like this:
var initError: NSError?
if let audioPlayer = AVAudioPlayer(contentsOfURL: filePathUrl, error: &initError) {
// use audioPlayer
} else {
println(initError) // handle error
}
Since Swift 1.2, you cannot throw/handle exceptions. While it is available in swift2 (need XCode7 support) which is still in beta. See this article for detail (https://www.hackingwithswift.com/new-syntax-swift-2-error-handling-try-catch).