CUDA进行视频解码的时候 最后的解码结果CUdeviceptr类型的 怎么转换成Mat类型呢？

void cudaPostProcessFrame(CUdeviceptr *ppDecodedFrame, size_t nDecodedPitch,
CUdeviceptr *ppTextureData, size_t nTexturePitch,
CUmodule cuModNV12toARGB,
CUfunction fpCudaKernel, CUstream streamID)

GPUMat nv12GpuMat = cuda::GpuMat(m_oVideoDecodeCreateInfo.ulTargetHeight * 3 / 2, m_oVideoDecodeCreateInfo.ulTargetWidth, CV_8UC1, (void*)dMappedFrame, pitch);
cv::Mat mainYUuvImage;
nv12GpuMat.download(mainYUuvImage);