How to Implement SFSpeechRecognizationTaskDelegates - swift

Question

I am trying to implement a speech to text application,i am able to record the audio from Microphone by using SFSpeechRecognizer .The use case is as soon as the user stop speaking ,a method should invoke and stop the recording automatically .Would you be able to help me the use case.
Please find the below code
func startRecording() {
// Clear all previous session data and cancel task
if recognitionTask != nil {
recognitionTask?.cancel()
recognitionTask = nil
}
// Create instance of audio session to record voice
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setCategory(AVAudioSession.Category.record, mode: AVAudioSession.Mode.measurement, options: AVAudioSession.CategoryOptions.defaultToSpeaker)
try audioSession.setActive(true, options: .notifyOthersOnDeactivation)
} catch {
print("audioSession properties weren't set because of an error.")
}
self.recognitionRequest = SFSpeechAudioBufferRecognitionRequest()
let inputNode = audioEngine.inputNode
guard let recognitionRequest = recognitionRequest else {
fatalError("Unable to create an SFSpeechAudioBufferRecognitionRequest object")
}
recognitionRequest.shouldReportPartialResults = true
self.recognitionTask = speechRecognizer?.recognitionTask(with: recognitionRequest, resultHandler: { (result, error) in
var isFinal = false
if result != nil {
self.lblText.text = result?.bestTranscription.formattedString
print(result?.bestTranscription.formattedString)
print(result?.isFinal)
isFinal = (result?.isFinal)!
}
if error != nil || isFinal {
self.audioEngine.stop()
inputNode.removeTap(onBus: 0)
self.recognitionRequest = nil
self.recognitionTask = nil
self.btnStart.isEnabled = true
}
})
let recordingFormat = inputNode.outputFormat(forBus: 0)
inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer, when) in
self.recognitionRequest?.append(buffer)
}
self.audioEngine.prepare()
do {
try self.audioEngine.start()
} catch {
print("audioEngine couldn't start because of an error.")
}
self.lblText.text = "Say something, I'm listening!"
}
}

Answer 1

As far as I understand you want to stop recognition when user stops speaking. I suggest to use Timer in order to track time spent in silence.
Add var detectionTimer: Timer? outside your startRecording(). And inside resultHandler of recognitionTask insert
self.detectionTimer?.invalidate()
self.detectionTimer = Timer.scheduledTimer(withTimeInterval: 2, repeats: false, block: { (timer) in
self.stopRecording()
})
This way after every recognised word you will start timer which will stop recognition if nothing was captured for 2 seconds. stopRecording should look something like this
audioEngine.stop()
recognitionRequest?.endAudio()
recognitionRequest = nil
audioEngine.inputNode.removeTap(onBus: 0)
// Cancel the previous task if it's running
if let recognitionTask = recognitionTask {
recognitionTask.cancel()
self.recognitionTask = nil
}

Answer 2

You can use a timer to achieve this. Start the time as soon as you start playing the audio engine to recognize the speech.
If speech will be recognized continuously the timer will get re started continuosly.
If there will be silence after fixed seconds selector method will get called and stop the recognition.
Below is the code -
func timerReStart() {
if timer != nil {
timer?.invalidate()
timer = nil
}
// Change the interval as per the requirement
timer = Timer.scheduledTimer(timeInterval: 20, target: self, selector: #selector(self.handleTimerValue), userInfo: nil, repeats: false)
}
#objc func handleTimerValue() {
cancelRecording()
}
func timerStop() {
guard timer != nil else { return }
timer?.invalidate()
timer = nil
}
func startRecording() {
// Clear all previous session data and cancel task
if recognitionTask != nil {
recognitionTask?.cancel()
recognitionTask = nil
}
// Create instance of audio session to record voice
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setCategory(AVAudioSession.Category.record, mode: AVAudioSession.Mode.measurement, options: AVAudioSession.CategoryOptions.defaultToSpeaker)
try audioSession.setActive(true, options: .notifyOthersOnDeactivation)
} catch {
print("audioSession properties weren't set because of an error.")
}
self.recognitionRequest = SFSpeechAudioBufferRecognitionRequest()
let inputNode = audioEngine.inputNode
guard let recognitionRequest = recognitionRequest else {
fatalError("Unable to create an SFSpeechAudioBufferRecognitionRequest object")
}
recognitionRequest.shouldReportPartialResults = true
self.recognitionTask = speechRecognizer?.recognitionTask(with: recognitionRequest, resultHandler: { (result, error) in
var isFinal = false
if result != nil {
self.lblText.text = result?.bestTranscription.formattedString
print(result?.bestTranscription.formattedString)
print(result?.isFinal)
isFinal = (result?.isFinal)!
self.timerReStart()
}
if error != nil || isFinal {
self.audioEngine.stop()
inputNode.removeTap(onBus: 0)
self.recognitionRequest = nil
self.recognitionTask = nil
self.btnStart.isEnabled = true
self.timerStop()
}
})
let recordingFormat = inputNode.outputFormat(forBus: 0)
inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer, when) in
self.recognitionRequest?.append(buffer)
}
self.audioEngine.prepare()
do {
try self.audioEngine.start()
//Start timer to check if there is silence
self.timerReStart()
} catch {
print("audioEngine couldn't start because of an error.")
}
self.lblText.text = "Say something, I'm listening!"
}
}
func cancelRecording() {
if audioEngine.isRunning {
let node = audioEngine.inputNode
node.removeTap(onBus: 0)
audioEngine.stop()
recognitionTask?.cancel()
recognitionTask = nil
}
self.timerStop()
}