ios使用AVCaptureVideoDataOutput实现连续拍照消除快门声音

最近碰到需求，要拍照时候没有声音，用AVCaptureStillImageOutput拍照会有快门声，查了网上的使用了反向声音的方式，但是因为要连拍会导致有些时候声音不同步，还是会有漏网的快门声，最后研究了一下使用了AVCaptureVideoDataOutput来对图像进行输出，没有了快门声音，代码如下：

//初始化
- (void)initAVCaptureSession{

    AVCaptureSession *session = [[AVCaptureSession alloc] init];

    NSError *error;

    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    //更改这个设置的时候必须先锁定设备，修改完后再解锁，否则崩溃
    [device lockForConfiguration:nil];
    //设置闪光灯为自动
    if ([device isFlashModeSupported:AVCaptureFlashModeOff]) {
        [device setFlashMode:AVCaptureFlashModeOff];
    };

    [device unlockForConfiguration];

    self.videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:device error:&error];
    if (error) {
        NSLog(@"%@",error);
    }

    // Create a VideoDataOutput and add it to the session
    self.imageOutput = [[AVCaptureVideoDataOutput alloc] init];
    [self.session addOutput:self.imageOutput];

    // Configure your output.
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
    [self.imageOutput setSampleBufferDelegate:self queue:queue];

    // Specify the pixel format
    self.imageOutput.videoSettings = [NSDictionary dictionaryWithObject:
     [NSNumber numberWithInt:kCVPixelFormatType_32BGRA]
                                forKey:(id)kCVPixelBufferPixelFormatTypeKey];




     // Start the session running to start the flow of data
     [session startRunning];

     // Assign session to an ivar.
     [self setSession:session];

    if ([self.session canAddInput:self.videoInput]) {
        [self.session addInput:self.videoInput];
    }

    if ([self.session canAddOutput:self.imageOutput]) {
        [self.session addOutput:self.imageOutput];
    }


    AVCaptureDevicePosition desiredPosition = AVCaptureDevicePositionFront;

    for (AVCaptureDevice *d in [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]) {
        if ([d position] == desiredPosition) {
            [self.previewLayer.session beginConfiguration];
            AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:d error:nil];
            for (AVCaptureInput *oldInput in self.previewLayer.session.inputs) {
                [[self.previewLayer session] removeInput:oldInput];
            }
            [self.previewLayer.session addInput:input];
            [self.previewLayer.session commitConfiguration];
            break;
        }
    }

}

//避免前置摄像头反转
- (AVCaptureVideoOrientation)avOrientationForDeviceOrientation:(UIDeviceOrientation)deviceOrientation
{
    AVCaptureVideoOrientation result = (AVCaptureVideoOrientation)deviceOrientation;
    if ( deviceOrientation == UIDeviceOrientationLandscapeLeft )
        result = AVCaptureVideoOrientationLandscapeRight;
    else if ( deviceOrientation == UIDeviceOrientationLandscapeRight )
        result = AVCaptureVideoOrientationLandscapeLeft;
    return result;
}

//使用前置摄像头
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

//照片获取，以及其他处理
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection
{

    if(sampleBuffer == NULL)
    {
        return ;
    }


        // Create a UIImage from the sample buffer data
        UIImage *oldImage = [self imageFromSampleBuffer:sampleBuffer];
        NSData *newData = UIImageJPEGRepresentation(oldImage, 0.3);

        [dataArray addObject:newData];

        NSString *imageName = [NSString stringWithFormat:@"%@.jpg",[self getCurrentTimeInterval]];        //保存图片本地
        NSString *savedImagePath = [LOCATION_IMAGES_PATH stringByAppendingPathComponent:imageName];

        //        NSLog(@"%@",savedImagePath);

        [newData writeToFile:savedImagePath atomically:NO];
}

// Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0);

    // Get the number of bytes per row for the pixel buffer
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

    // Get the number of bytes per row for the pixel buffer
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    // Get the pixel buffer width and height
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);

    // Create a device-dependent RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
                                                 bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Free up the context and color space
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    UIImage *image = [UIImage imageWithCGImage:quartzImage];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return (image);
}