How to Auto stop speech recognition if user stop speaking

问题

I am working on Bot app and here I have 2 features

• Speech to Text
• Text to Speech

Both are working as expected but I want to detect that when user stop speaking at that time I want to stop detection and send that data to server.

Is there any way to get that user is not speaking ?

I am using below code for speech detection :

// Starts an AVAudio Session
    NSError *error;
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&error];
    [audioSession setActive:YES withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:&error];

    // Starts a recognition process, in the block it logs the input or stops the audio
    // process if there's an error.
    recognitionRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
    AVAudioInputNode *inputNode = audioEngine.inputNode;
    recognitionRequest.shouldReportPartialResults = YES;
    recognitionTask = [speechRecognizer recognitionTaskWithRequest:recognitionRequest resultHandler:^(SFSpeechRecognitionResult * _Nullable result, NSError * _Nullable error) {
        BOOL isFinal = NO;
        if (result) {
            // Whatever you say in the microphone after pressing the button should be being logged
            // in the console.
            NSLog(@"RESULT:%@",result.bestTranscription.formattedString);
            self.inputToolbar.contentView.textView.text = result.bestTranscription.formattedString;
            self.inputToolbar.contentView.rightBarButtonItem.enabled = YES;
            isFinal = !result.isFinal;
        }
        if (error) {
            if (audioEngine != NULL) {
                [audioEngine stop];
                [inputNode removeTapOnBus:0];
                recognitionRequest = nil;
                recognitionTask = nil;
            }
        }
    }];

    // Sets the recording format
    AVAudioFormat *recordingFormat = [inputNode outputFormatForBus:0]; //[[AVAudioFormat alloc] initStandardFormatWithSampleRate:44100 channels:1];
    [inputNode installTapOnBus:0 bufferSize:1024 format:recordingFormat block:^(AVAudioPCMBuffer * _Nonnull buffer, AVAudioTime * _Nonnull when) {
        [recognitionRequest appendAudioPCMBuffer:buffer];
    }];

    // Starts the audio engine, i.e. it starts listening.
    [audioEngine prepare];
    [audioEngine startAndReturnError:&error];
    NSLog(@"Say Something, I'm listening");

Let me know if any one required more detail on this.

Thanks in Advance.

回答1:

try using this:

AVAudioRecorder *recorder;
NSTimer *levelTimer;
double lowPassResults;

-(void)configureRecorder{
    // AVAudioSession already set in your code, so no need for these 2 lines.
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
    [[AVAudioSession sharedInstance] setActive:YES error:nil];

    NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];

    NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                          [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                          [NSNumber numberWithInt: 1],                         AVNumberOfChannelsKey,
                          [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                          nil];

    NSError *error;

    lowPassResults = 0;

    recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];

    if (recorder) {
        [recorder prepareToRecord];
        recorder.meteringEnabled = YES;
        [recorder record];
        levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.05 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];
    } else
        NSLog(@"%@", [error description]);
    }
}


- (void)levelTimerCallback:(NSTimer *)timer {
    [recorder updateMeters];

    const double ALPHA = 0.05;
    double peakPowerForChannel = pow(10, (0.05 * [recorder peakPowerForChannel:0]));
    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;  

    NSLog(@"lowPassResults: %f",lowPassResults);

    // Use here a threshold value to stablish if there is silence or speech
    if (lowPassResults < 0.1) {
        NSLog(@"Silence");
    } else if(lowPassResults > 0.5){
        NSLog(@"Speech");
    }
}

Reference: http://codedrago.com/q/200783/ios-objective-c-speech-recognition-how-to-detect-speech-start-on-ios-speech-api

来源：https://stackoverflow.com/questions/46337097/how-to-auto-stop-speech-recognition-if-user-stop-speaking