how to use page-locked memory, the CudaMem class

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Hello guys,

I'm quite new in Cuda programming as well. For me it's still quite unclear how to use the CudaMem class. for example how I can do following using page_locked or even zero_copy memory:

Mat srcCpu3ChImg;
Mat outCpu4ChImg;

GpuMat srcGpu3ChImg;
GpuMat outGpu4ChImg;

// load srcCpu3ChImg

srcGpu3ChImg.upload(srcCpu3ChImg);
cv::gpu::cvtColor(srcGpu3ChImg, outGpu4ChImg, CV_BGR2BGRA);
outGpu4ChImg.download(outCpu4ChImg);

thank you a lot in advance cheers greg