How to convert cv::Mat to NvBufSurface without memcpy

Robotics & Edge Computing Jetson Systems Jetson AGX Orin
1

Hi,
jetpack: 5.1.2
I read some topics about cv::Mat to NvBufSurface, but all of those need memcpy which is unacceptable for me. Because I don’t want any cpu cost in this process.
So my question is: 1. If it possible convert cv::Mat to NvBufSurface without memcpy?
2. Does NvBufSurface2Raw use memcpy or some cpu copy method actually?
Thanks!
BR/Tim

3

Hi,

1. Please check below for a comment:

2. Based on the description, it should include a copy step.
https://docs.nvidia.com/jetson/archives/r35.2.1/ApiReference/group__ds__aaa.html#ga001206f7623c36d0dadbdc39906162c7

Thanks.

4

Hi AastaLLL
This comment’s answer actually is about NvBufSurface to Mat.
So it seems no way to optimise those memcpy in jetpack, right?
BR/Tim

5

Hi,
You are correct that converting cv::Mat to NvBufSurface requires memory copy. It is not required if you allocate NvBufSurface first, and then map to cv::Mat.

NvBufSurface2Raw() uses the function similar to memcpy() to copy data from NvBufSurface to a CPU buffer.

6

Hi DaneLLL,
Thanks for your reply!
I tried NvBufSurface2Raw, and it seems had better cpu loading performance than memcpy. Is it use DMA?
Thanks!
BR/Tim

7

Hi,
It is done with private function and may have better or identical performance when comparing to memcpy().