ios - 几分钟后 SpeechRecognizer 失败

Question

我正在开发一个使用 SFSpeechRecognizer 的 iOS 项目，它在开始时运行良好。我说了一些话，它就回应了。但是一两分钟后，它就失败了。它不提供任何认可结果的反馈。 我想知道这是否与缓冲区有关，但我不知道如何解决。

我基本上是用SpeechRecognizer的demo来搭建工程的。不同的是我把识别出来的结果一个字一个字的存储在一个数组中。程序会分析数组并响应某些单词，例如“播放”或先前设置的其他一些命令。程序响应命令后，删除该数组元素。

话不多说，代码如下:

1. 识别器，可以看到supportedCommands数组过滤了一些特定的词让程序响应。其他部分与https://developer.apple.com/library/content/samplecode/SpeakToMe/Listings/SpeakToMe_ViewController_swift.html#//apple_ref/doc/uid/TP40017110-SpeakToMe_ViewController_swift-DontLinkElementID_6的demo类似。

   class SpeechRecognizer: NSObject, SFSpeechRecognizerDelegate {
   
       private var speechRecognizer: SFSpeechRecognizer!
       private var recognitionRequest: SFSpeechAudioBufferRecognitionRequest!
       private var recognitionTask: SFSpeechRecognitionTask!
       private let audioEngine = AVAudioEngine()
       private let locale = Locale(identifier: "en-US")
   
       private var lastSavedString: String = ""
       private let supportedCommands = ["more", "play"]
   
       var speechInputQueue: [String] = [String]()
   
       func load() {
           print("load")
           prepareRecognizer(locale: locale)
   
           authorize()
       }
   
       func start() {
           print("start")
           if !audioEngine.isRunning {
               try! startRecording()
           }
       }
   
       func stop() {
           if audioEngine.isRunning {
               audioEngine.stop()
               recognitionRequest?.endAudio()
   
           }
       }
   
       private func authorize() {
           SFSpeechRecognizer.requestAuthorization { authStatus in
               OperationQueue.main.addOperation {
                   switch authStatus {
                   case .authorized:
                       print("Authorized!")
                   case .denied:
                       print("Unauthorized!")
                   case .restricted:
                       print("Unauthorized!")
                   case .notDetermined:
                       print("Unauthorized!")
                   }
               }
           }
       }
   
       private func prepareRecognizer(locale: Locale) {
           speechRecognizer = SFSpeechRecognizer(locale: locale)!
           speechRecognizer.delegate = self
       }
   
       private func startRecording() throws {
   
           // Cancel the previous task if it's running.
           if let recognitionTask = recognitionTask {
               recognitionTask.cancel()
               self.recognitionTask = nil
           }
   
           let audioSession = AVAudioSession.sharedInstance()
           try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, with: .defaultToSpeaker)
           try audioSession.setMode(AVAudioSessionModeDefault)
           try audioSession.setActive(true, with: .notifyOthersOnDeactivation)
   
           recognitionRequest = SFSpeechAudioBufferRecognitionRequest()
   
           let inputNode = audioEngine.inputNode
           guard let recognitionRequest = recognitionRequest else { fatalError("Unable to created a SFSpeechAudioBufferRecognitionRequest object") }
   
           // Configure request so that results are returned before audio recording is finished
           recognitionRequest.shouldReportPartialResults = true
   
           // A recognition task represents a speech recognition session.
           // We keep a reference to the task so that it can be cancelled.
           recognitionTask = speechRecognizer.recognitionTask(with: recognitionRequest) { result, error in
               var isFinal = false
   
               if let result = result {
   
                   let temp = result.bestTranscription.formattedString.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines).lowercased()
                   //print("temp", temp)
                   if temp != self.lastSavedString && temp.count > self.lastSavedString.count {
   
                       var tempSplit = temp.split(separator: " ")
                       var lastSplit = self.lastSavedString.split(separator: " ")
                       while lastSplit.count > 0 {
                           if String(tempSplit[0]) == String(lastSplit[0]) {
                               tempSplit.remove(at: 0)
                               lastSplit.remove(at: 0)
                           }
                           else {
                               break
                           }
                       }
   
                       for command in tempSplit {
                           if self.supportedCommands.contains(String(command)) {
                               self.speechInputQueue.append(String(command))
                           }
                       }
                       self.lastSavedString = temp
   
                   }
                   isFinal = result.isFinal
               }
   
               if error != nil || isFinal {
                   self.audioEngine.stop()
                   inputNode.removeTap(onBus: 0)
                   self.recognitionRequest = nil
                   self.recognitionTask = nil
               }
           }
   
           let recordingFormat = inputNode.outputFormat(forBus: 0)
           inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer: AVAudioPCMBuffer, when: AVAudioTime) in
               self.recognitionRequest?.append(buffer)
           }
   
           audioEngine.prepare()
   
           try audioEngine.start()
   
       }
   }
   

2. 我们如何使用它:

       if self.speechRecognizer.speechInputQueue.count > 0 {
       if self.speechRecognizer.speechInputQueue[0] == "more" {
           print("temp", temp)
           print("content", content)
          // isSpeakingContent = true
           self.textToSpeech(text: content)
       }
       else if self.speechRecognizer.speechInputQueue[0] == "play" {
           print("try to play")
           let soundURL = URL(fileURLWithPath: Bundle.main.path(forResource: "cascade", ofType: "wav")!)
   
           do {
               audioPlayer = try AVAudioPlayer(contentsOf: soundURL)
           }
           catch {
               print(error)
           }
           audioPlayer.prepareToPlay()
           audioPlayer.play()
       }
       else {
           self.textToSpeech(text: "unrecognized command")
       }
       self.speechRecognizer.speechInputQueue.remove(at: 0)
       print("after :", self.speechRecognizer.speechInputQueue)
   }
   

它响应某些命令并播放一些音频。

Buffer有问题吗？也许识别一两分钟后，缓冲区就满了？识别器只是随着时间的推移而失败。

Answer 1

来自 WWDC 2016 Session 509: Speech Recognition API :

For iOS 10 we're starting with a strict audio duration limit of about one minute which is similar to that of keyboard dictation.