iOS 8上的AVCaptureVideoDataOutput不会在指定的调度队列上发布样本缓冲区

当使用AVCaptureVideoDataOutput并使用调度队列(setSampleBufferDelegate：queuE)定义样本缓冲区委托时,我们在iOS 8上遇到AVFoundation不会在指定的调度队列上发布样本缓冲区,而是始终使用“com.apple.avfoundation.videodataoutput” .bufferqueue”.

这在iOS7上按预期工作.

还有其他人经历过这个吗？

一个明显的解决方法是在回调中手动调用dispatch_sync以将处理同步到自定义调度队列,但奇怪的是,这会导致死锁……

产生此问题的示例代码：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view,typically from a nib.

    AVCaptureSession *session = [[AVCaptureSession alloc] init];
    session.sessionPreset = AVCaptureSessionPresetMedium;

    AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
    captureVideoPreviewLayer.frame = self.view.bounds;
    [self.view.layer addSublayer:captureVideoPreviewLayer];

    [session addInput:[AVCaptureDeviceInput deviceInputWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] error:nil]];

    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];

    queue = dispatch_queue_create("our.dispatch.queue",DISPATCH_QUEUE_seriaL);

    [output setSampleBufferDelegate:self queue:queue];

    [session addOutput:output];

    [session startRunning];
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    NSLog(@"Running on queue %@,queue that was set is %@,this is %s",dispatch_get_current_queue(),[captureOutput performSELEctor:@SELEctor(sampleBufferCallBACkQueuE)],queue == dispatch_get_current_queue() ? "our queue" : "not our queue!!!");
}