相关疑难解决方法(0)

我正在实施一个软件来从网络摄像头获取视频.我在Apple Dev中看过MyRecorder示例,它运行正常.

我尝试使用以下代码添加一个按钮从视频拍摄快照:

- (IBAction)addFrame:(id)sender
{
    CVImageBufferRef imageBuffer;
    @synchronized (self) {
        imageBuffer = CVBufferRetain(mCurrentImageBuffer);
    }
    if (imageBuffer) { 
    [ bla bla bla ]     
    }
}

但是mCurrentImageBuffer总是空的.如何从我的网络摄像头获取当前帧并放入mCurrentImageBuffer？

我试过用

(void)captureOutput:(QTCaptureOutput *)captureOutput 
                    didOutputVideoFrame:(CVImageBufferRef)videoFrame 
                    withSampleBuffer:(QTSampleBuffer *)sampleBuffer 
                    fromConnection:(QTCaptureConnection *)connection
{
    CVImageBufferRef imageBufferToRelease;

    CVBufferRetain(videoFrame);

    @synchronized (self) {
        imageBufferToRelease = mCurrentImageBuffer;
        mCurrentImageBuffer = videoFrame;
    }
    CVBufferRelease(imageBufferToRelease);  
} 

但它永远不会被召唤.我怎样才能决定何时调用captureOutput委托方法？任何的想法？

谢谢,安德烈