NVIDIA Optical Flow SDK - Support for 1x1 motion vectors

Gaming and Visualization Technologies Video Processing & Optical Flow
1

The NVOFA Application Note pdf (distributed with SDK) mentions that it is possible to generate flow vectors for 1x1 and 2x2 grid sizes as of NVOF SDK 1.1.

Support has been added across all sample applications to generate
flow vectors for 1x1 and 2x2 grid sizes using CUDA and compute
kernels for CUDA and DirectX 11 interfaces respectively.

However, NV_OF_OUTPUT_VECTOR_GRID_SIZE and NV_OF_HINT_VECTOR_GRID_SIZE found in nvOpticalFlowCommon.h only seem to enlist grid sizes of 4x4 and 8x8. The call to nvOpticalFlow->GetNextMinGridSize(gridSize, hwGridSize) returns 4 as well, despite using the 1.1 SDK and driver version 436.30 on RTX 2070 Super. This is running AppOfCuda from the samples contained within the SDK.

How do I run Optical Flow in a way that generates flow vectors of size 1x1?

2

Hi.
NVOF API generates flow of 4x4 sizes only. The sample application(s) convert them to 2x2 or 1x1 flow depending on the command line parameter using nearest neighbor upscaling.
e.g.
AppOFCuda.exe --input=ip_nv12_1920x1080.yuv --output=out_of_cuda_sample_1x1 --preset=slow --visualFlow=true --gridSize=1

AppOFD3D11.exe --input=ip_nv12_1920x1080.yuv --output=out_of_dx_sample_1x1 --preset=slow --visualFlow=true --gridSize=1

We will update the documentation to include these details in the future SDK release.

Thanks.