I am hacking a little project using iOS 10 built-in speech recognition. I have working results using device's microphone, my speech is recognized very accurately.
My problem is that recognition task callback is called for every available partial transcription, and I want it to detect person stopped talking and call the callback with isFinal
property set to true. It is not happening - app is listening indefinitely.
Is SFSpeechRecognizer
ever capable of detecting end of sentence?
Here's my code - it is based on example found on the Internets, it is mostly a boilerplate needed to recognize from microphone source.
I modified it by adding recognition taskHint
. I also set shouldReportPartialResults
to false, but it seems it has been ignored.
func startRecording() {
if recognitionTask != nil {
recognitionTask?.cancel()
recognitionTask = nil
}
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setCategory(AVAudioSessionCategoryRecord)
try audioSession.setMode(AVAudioSessionModeMeasurement)
try audioSession.setActive(true, with: .notifyOthersOnDeactivation)
} catch {
print("audioSession properties weren't set because of an error.")
}
recognitionRequest = SFSpeechAudioBufferRecognitionRequest()
recognitionRequest?.shouldReportPartialResults = false
recognitionRequest?.taskHint = .search
guard let inputNode = audioEngine.inputNode else {
fatalError("Audio engine has no input node")
}
guard let recognitionRequest = recognitionRequest else {
fatalError("Unable to create an SFSpeechAudioBufferRecognitionRequest object")
}
recognitionRequest.shouldReportPartialResults = true
recognitionTask = speechRecognizer?.recognitionTask(with: recognitionRequest, resultHandler: { (result, error) in
var isFinal = false
if result != nil {
print("RECOGNIZED \(result?.bestTranscription.formattedString)")
self.transcriptLabel.text = result?.bestTranscription.formattedString
isFinal = (result?.isFinal)!
}
if error != nil || isFinal {
self.state = .Idle
self.audioEngine.stop()
inputNode.removeTap(onBus: 0)
self.recognitionRequest = nil
self.recognitionTask = nil
self.micButton.isEnabled = true
self.say(text: "OK. Let me see.")
}
})
let recordingFormat = inputNode.outputFormat(forBus: 0)
inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer, when) in
self.recognitionRequest?.append(buffer)
}
audioEngine.prepare()
do {
try audioEngine.start()
} catch {
print("audioEngine couldn't start because of an error.")
}
transcriptLabel.text = "Say something, I'm listening!"
state = .Listening
}
It seems that isFinal flag doesn't became true when user stops talking as expected. I guess this is a wanted behaviour by Apple, because the event "User stops talking" is an undefined event.
I believe that the easiest way to achieve your goal is to do the following:
You have to estabilish an "interval of silence". That means if the user doesn't talk for a time greater than your interval, he has stopped talking (i.e. 2 seconds).
Create a Timer at the beginning of the audio session
:
var timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: "didFinishTalk", userInfo: nil, repeats: false)
when you get new transcriptions in recognitionTask
invalidate and restart your timer
timer.invalidate()
timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: "didFinishTalk", userInfo: nil, repeats: false)
if the timer expires this means the user doesn't talk from 2 seconds. You can safely stop Audio Session and exit