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我开始明白了这一点。 AVAudioRecorder会话被激活，我得到麦克风水平读数几秒钟。然后异步视频代码完成，摄像机视图显示，我停止获取读数。好像视频正在杀死音频会话。

奇怪的是，该代码适用于iOS 7，并且无法在iOS 6上运行。任何想法如何解决这个问题。这是对iOS 6的限制吗？

我通过麦克风获得声级，当我在设置录音机对象的代码上放置断点时，我只能得到它们。如果我在那个时间没有暂停的情况下运行几秒钟就无法获得等级。这段代码在viewDidLoad中，我可以将断点放在前3行中的一行：

_recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];
[_recorder prepareToRecord];
_recorder.meteringEnabled = YES;

    _levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.03 target: self selector: @selector(levelTimerCallback) userInfo: nil repeats: YES];

我在levelTimerCallback方法中得到了我的关卡。

此代码进入viewDidAppear：

    NSError *error;

if (_recorder) {
    [_recorder record];
} else
    NSLog(@"Error: %@", [error description]);

编辑：

levelTimerCallback代码：

    [_recorder updateMeters];

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

NSLog(@"Average input: %f Peak input: %f", [_recorder averagePowerForChannel:0], [_recorder peakPowerForChannel:0]);

异步代码在记录器代码上方运行：

            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            [[[self captureManager] session] startRunning];
        });

相机代码：

    if ([self captureManager] == nil) {
    AVCamCaptureManager *manager = [[AVCamCaptureManager alloc] init];
    [self setCaptureManager:manager];

    [[self captureManager] setDelegate:self];

    if ([[self captureManager] setupSession]) {
        // Create video preview layer and add it to the UI
        AVCaptureVideoPreviewLayer *newCaptureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:[[self captureManager] session]];
        UIView *view = [self videoPreviewView];
        CALayer *viewLayer = [view layer];
        [viewLayer setMasksToBounds:YES];

        CGRect bounds = [view bounds];
        [newCaptureVideoPreviewLayer setFrame:bounds];

        if ([[newCaptureVideoPreviewLayer connection] isVideoOrientationSupported]) {
            [[newCaptureVideoPreviewLayer connection] setVideoOrientation:AVCaptureVideoOrientationPortrait];
        }

        [newCaptureVideoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

        [viewLayer insertSublayer:newCaptureVideoPreviewLayer below:[[viewLayer sublayers] objectAtIndex:0]];

        [self setCaptureVideoPreviewLayer:newCaptureVideoPreviewLayer];

        // Start the session. This is done asychronously since -startRunning doesn't return until the session is running.
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            [[[self captureManager] session] startRunning];
        });


        [self addObserver:self forKeyPath:@"captureManager.videoInput.device.focusMode" options:NSKeyValueObservingOptionNew context:AVCamFocusModeObserverContext];

        // Add a single tap gesture to focus on the point tapped, then lock focus
        UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapToAutoFocus:)];
        [singleTap setDelegate:self];
        [singleTap setNumberOfTapsRequired:1];
        [view addGestureRecognizer:singleTap];

        // Add a double tap gesture to reset the focus mode to continuous auto focus
        UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapToContinouslyAutoFocus:)];
        [doubleTap setDelegate:self];
        [doubleTap setNumberOfTapsRequired:2];
        [singleTap requireGestureRecognizerToFail:doubleTap];
        [view addGestureRecognizer:doubleTap];
    }
}

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];

AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setActive: YES error: nil];

[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryRecord error: nil];

NSError *error;
_recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];

Answer 1

我认为您应该在_levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.03 target: self selector: @selector(levelTimerCallback) userInfo: nil repeats: YES];结束时致电viewDidAppear，并将其取消并在viewDidDisappear中使其无效。当viewDidLoad中有其他代码时，从viewDidAppear开始计时器没有意义。您可能还想使用主线程而不是[[[self captureManager] session] startRunning];的后台线程进行检查。

iOS - 代码仅在插入断点时有效

1 个答案: