AVAudioSession issue when using SFSpeechRecognizer after AVSpeechUtterance

I am trying to use SFSpeechRecognizer for speech-to-text, after delivering a welcome message to a user via AVSpeechUtterance. But randomly speech recognition doesn't start (after talking the welcome message) and it throws the below error message.

[avas] ERROR: AVAudioSession.mm:1049: - [AVAudioSession setActive: withOptions: error:]: deactivation of audio session with start of I / O. All I / O operations must be stopped or paused before deactivating the audio session.

It works several times. It's not clear why it doesn't work consistently.

I tried the solutions mentioned in other SO posts where it is mentioned to check if there are audio players. I added that speech check for the textual part of the code. It returns false (i.e. no other audio player works). But nevertheless, speech in the text does not begin to listen to the user's speech. Can you tell me what is going wrong.

Testing on iPhone 6 running iOS 10.3

Below are the code snippets:

TextToSpeech

- (void) speak:(NSString *) textToSpeak {
    [[AVAudioSession sharedInstance] setActive:NO withOptions:0 error:nil];
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback
      withOptions:AVAudioSessionCategoryOptionDuckOthers error:nil];

    [synthesizer stopSpeakingAtBoundary:AVSpeechBoundaryImmediate];

    AVSpeechUtterance* utterance = [[AVSpeechUtterance new] initWithString:textToSpeak];
    utterance.voice = [AVSpeechSynthesisVoice voiceWithLanguage:locale];
    utterance.rate = (AVSpeechUtteranceMinimumSpeechRate * 1.5 + AVSpeechUtteranceDefaultSpeechRate) / 2.5 * rate * rate;
    utterance.pitchMultiplier = 1.2;
    [synthesizer speakUtterance:utterance];
}

- (void)speechSynthesizer:(AVSpeechSynthesizer*)synthesizer didFinishSpeechUtterance:(AVSpeechUtterance*)utterance {
    //Return success message back to caller

    [[AVAudioSession sharedInstance] setActive:NO withOptions:0 error:nil];
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient
      withOptions: 0 error: nil];
    [[AVAudioSession sharedInstance] setActive:YES withOptions: 0 error:nil];
}

      

        
        
        
      

    

Speech to Text :

- (void) recordUserSpeech:(NSString *) lang {
    NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:lang];
    self.sfSpeechRecognizer = [[SFSpeechRecognizer alloc] initWithLocale:locale];
    [self.sfSpeechRecognizer setDelegate:self];

    NSLog(@"Step1: ");
    // Cancel the previous task if it running.
    if ( self.recognitionTask ) {
        NSLog(@"Step2: ");
        [self.recognitionTask cancel];
        self.recognitionTask = nil;
    }

    NSLog(@"Step3: ");
    [self initAudioSession];

    self.recognitionRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
    NSLog(@"Step4: ");

    if (!self.audioEngine.inputNode) {
        NSLog(@"Audio engine has no input node");
    }

    if (!self.recognitionRequest) {
        NSLog(@"Unable to created a SFSpeechAudioBufferRecognitionRequest object");
    }

    self.recognitionTask = [self.sfSpeechRecognizer recognitionTaskWithRequest:self.recognitionRequest resultHandler:^(SFSpeechRecognitionResult *result, NSError *error) {

        bool isFinal= false;

        if (error) {
            [self stopAndRelease];
            NSLog(@"In recognitionTaskWithRequest.. Error code ::: %ld, %@", (long)error.code, error.description);
            [self sendErrorWithMessage:error.localizedFailureReason andCode:error.code];
        }

        if (result) {

            [self sendResults:result.bestTranscription.formattedString];
            isFinal = result.isFinal;
        }

        if (isFinal) {
            NSLog(@"result.isFinal: ");
            [self stopAndRelease];
            //return control to caller
        }
    }];

    NSLog(@"Step5: ");

    AVAudioFormat *recordingFormat = [self.audioEngine.inputNode outputFormatForBus:0];

    [self.audioEngine.inputNode installTapOnBus:0 bufferSize:1024 format:recordingFormat block:^(AVAudioPCMBuffer * _Nonnull buffer, AVAudioTime * _Nonnull when) {
        //NSLog(@"Installing Audio engine: ");
        [self.recognitionRequest appendAudioPCMBuffer:buffer];
    }];

    NSLog(@"Step6: ");

    [self.audioEngine prepare];
    NSLog(@"Step7: ");
    NSError *err;
    [self.audioEngine startAndReturnError:&err];
}
- (void) initAudioSession
{
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryRecord error:nil];
    [audioSession setMode:AVAudioSessionModeMeasurement error:nil];
    [audioSession setActive:YES withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:nil];
}

-(void) stopAndRelease
{
    NSLog(@"Invoking SFSpeechRecognizer stopAndRelease: ");
    [self.audioEngine stop];
    [self.recognitionRequest endAudio];
    [self.audioEngine.inputNode removeTapOnBus:0];
    self.recognitionRequest = nil;
    [self.recognitionTask cancel];
    self.recognitionTask = nil;
}

      

        
        
        
      

    

As for the logs added, I can view all logs up to "Step7".

When debugging code on a device, it sequentially triggers breaks on the bottom lines (I have the exception breakpoints), although the continuation continues with execution. However, this occurs during several successful executions.

AVAudioFormat * recordFormat = [self.audioEngine.inputNode outputFormatForBus: 0];

[self.audioEngine prepare];