Question

有问题的问题是使用AVFoundation来设置一个输出显示在AVCaptureVideoPreviewLayer中的相机，并将其作为像素缓冲区处理。为了通过- processSampleBuffer:方法处理像素缓冲区，必须以正确的方向提供，这取决于设备方向。

据我所知，这可以通过在-captureOutput:didOutputSampleBuffer:fromConnection:中访问原始像素值，或通过设置videoOrientation来旋转样本缓冲区委托方法中给定的像素缓冲区来完成相应AVCaptureConnection上的属性，确保像素缓冲区以所需方向提供。设置概述如下：

- (void)setupCamera
{
    AVCaptureSession *session = [AVCaptureSession new];
    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:nil];
    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

    [session addInput:deviceInput];

    dispatch_queue_t videoOutputQueue = dispatch_queue_create("com.MyApp.videoQueue", DISPATCH_QUEUE_SERIAL);
    dispatch_set_target_queue(videoOutputQueue, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0));

    AVCaptureVideoDataOutput *videoOutput = [AVCaptureVideoDataOutput new];
    videoOutput.alwaysDiscardsLateVideoFrames = YES;
    [videoOutput setSampleBufferDelegate:self queue:videoOutputQueue];
    [session addOutput:videoOutput];

    // more setup
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection
{
    connection.videoOrientation = [self getCurrentOrientation]; // setting this to a new value causes the preview layer to freeze momentarily
    [self processSampleBuffer:sampleBuffer]; // some arbitrary image processing method
}

就像素缓冲区的方向而言，这可以正常工作，但是，只要将设备旋转到新的方向，给connection.videoOrientation一个新值，预览图层就会冻结几分之一秒。阻止委托方法的线程（例如通过添加睡眠）不会冻结预览层，因此不是问题。对解决方案的任何帮助都非常感谢！

设置AVCaptureConnection视频方向时滞后

0 个答案: