如何在iOS Speech API上检测语音启动

Question

我有一个在XCode/Objective C中开发的iOS应用程序.它使用iOS Speech API处理连续语音识别.它正在工作,但我想在语音开始时将麦克风图标变为红色,我还想检测语音何时结束.

我实现了接口SFSpeechRecognitionTaskDelegate,它给出了回调onDetectedSpeechStart和speechRecognitionTask:didHypothesizeTranscription:但是这些不会发生,直到第一个单词的结尾被处理,而不是在语音的最开始.

我想检测一下演讲的开头(或任何噪音).我认为应该可以从installTapOnBus:来自AVAudioPCMBuffer,但我不知道如何检测这是否是静音与可能是语音的噪音.

此外,当人们停止说话时,语音API不会给出事件,即静音检测,它只是记录,直到它超时.我通过检查最后一次事件之间的时间来检测静音,但不确定它们是否是更好的方法.

代码在这里,

    NSError * outError;
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory: AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker error:&outError];
    [audioSession setMode: AVAudioSessionModeMeasurement error:&outError];
    [audioSession setActive: true withOptions: AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:&outError];

    SFSpeechAudioBufferRecognitionRequest* speechRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];

    if (speechRequest == nil) {
        NSLog(@"Unable to create SFSpeechAudioBufferRecognitionRequest.");
        return;
    }

    audioEngine = [[AVAudioEngine alloc] init];
    AVAudioInputNode* inputNode = [audioEngine inputNode];

    speechRequest.shouldReportPartialResults = true;

    // iOS speech does not detect end of speech, so must track silence.
    lastSpeechDetected = -1;

    speechTask = [speechRecognizer recognitionTaskWithRequest: speechRequest delegate: self];

    [inputNode installTapOnBus:0 bufferSize: 4096 format: [inputNode outputFormatForBus:0] block:^(AVAudioPCMBuffer* buffer, AVAudioTime* when) {
        long millis = [[NSDate date] timeIntervalSince1970] * 1000;
        if (lastSpeechDetected != -1 && ((millis - lastSpeechDetected) > 1000)) {
            lastSpeechDetected = -1;
            [speechTask finish];
            return;
        }
        [speechRequest appendAudioPCMBuffer: buffer];
    }];

    [audioEngine prepare];
    [audioEngine startAndReturnError: &outError];

Answer 1

这是我们最终得到的有效代码。

关键是安装TapOnBus()，然后是检测音量的魔术代码，

浮动体积 = fabsf(*buffer.floatChannelData[0]);

-(void) doActualRecording {
    NSLog(@"doActualRecording");

    @try {
    //if (!recording) {
        if (audioEngine != NULL) {
            [audioEngine stop];
            [speechTask cancel];
            AVAudioInputNode* inputNode = [audioEngine inputNode];
            [inputNode removeTapOnBus: 0];
        }

        recording = YES;
        micButton.selected = YES;

        //NSLog(@"Starting recording...   SFSpeechRecognizer Available? %d", [speechRecognizer isAvailable]);
        NSError * outError;
        //NSLog(@"AUDIO SESSION CATEGORY0: %@", [[AVAudioSession sharedInstance] category]);
        AVAudioSession* audioSession = [AVAudioSession sharedInstance];
        [audioSession setCategory: AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker error:&outError];
        [audioSession setMode: AVAudioSessionModeMeasurement error:&outError];
        [audioSession setActive: true withOptions: AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:&outError];

        SFSpeechAudioBufferRecognitionRequest* speechRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
        //NSLog(@"AUDIO SESSION CATEGORY1: %@", [[AVAudioSession sharedInstance] category]);
        if (speechRequest == nil) {
            NSLog(@"Unable to create SFSpeechAudioBufferRecognitionRequest.");
            return;
        }

        speechDetectionSamples = 0;

        // This some how fixes a crash on iPhone 7
        // Seems like a bug in iOS ARC/lack of gc
        AVAudioEngine* temp = audioEngine;
        audioEngine = [[AVAudioEngine alloc] init];
        AVAudioInputNode* inputNode = [audioEngine inputNode];

        speechRequest.shouldReportPartialResults = true;

        // iOS speech does not detect end of speech, so must track silence.
        lastSpeechDetected = -1;

        speechTask = [speechRecognizer recognitionTaskWithRequest: speechRequest delegate: self];

        [inputNode installTapOnBus:0 bufferSize: 4096 format: [inputNode outputFormatForBus:0] block:^(AVAudioPCMBuffer* buffer, AVAudioTime* when) {
            @try {
                long long millis = [[NSDate date] timeIntervalSince1970] * 1000;
                if (lastSpeechDetected != -1 && ((millis - lastSpeechDetected) > 1000)) {
                    lastSpeechDetected = -1;
                    [speechTask finish];
                    return;
                }
                [speechRequest appendAudioPCMBuffer: buffer];

                //Calculate volume level
                if ([buffer floatChannelData] != nil) {
                    float volume = fabsf(*buffer.floatChannelData[0]);

                    if (volume >= speechDetectionThreshold) {
                        speechDetectionSamples++;

                        if (speechDetectionSamples >= speechDetectionSamplesNeeded) {

                            //Need to change mic button image in main thread
                            [[NSOperationQueue mainQueue] addOperationWithBlock:^ {

                                [micButton setImage: [UIImage imageNamed: @"micRecording"] forState: UIControlStateSelected];

                            }];
                        }
                    } else {
                        speechDetectionSamples = 0;
                    }
                }
            }
            @catch (NSException * e) {
                NSLog(@"Exception: %@", e);
            }
        }];

        [audioEngine prepare];
        [audioEngine startAndReturnError: &outError];
        NSLog(@"Error %@", outError);
    //}
    }
    @catch (NSException * e) {
        NSLog(@"Exception: %@", e);
    }
}