GPU based optical flow extraction in OpenCV

Features:

• OpenCV wrapper for Real-Time optical flow extraction on GPU
• Automatic directory handling using Qt
• Allows saving of optical flow to disk, ** either with clipping large displacements ** or by adaptively scaling the displacements to the radiometric resolution of the output image

Dependencies

• [OpenCV 2.4] (http://opencv.org/downloads.html)
• [Qt 5.4] (https://www.qt.io/qt5-4/)
• [cmake] (https://cmake.org/)

Installation

1. mkdir -p build
2. cd build
3. cmake ..
4. make
5. sudo make install

Configuration:

You should adjust the input and output directories by editing the variables vid_path, out_path and out_path_jpeg in compute_flow.cpp. Note that these folders have to exist before executing.

Usage:

./brox_flow [OPTION]...

Available options:

• start_video: start with video number in vid_path directory structure [1]
• gpuID: use this GPU ID [0]
• type: use this flow method Brox = 0, TVL1 = 1 [1]
• skip: the number of frames that are skipped between flow calcuation [1]

Additional features in compute_flow.cpp:

• float MIN_SZ = 256: defines the smallest side of the frame for optical flow computation
• float OUT_SZ = 256: defines the smallest side of the frame for saving as .jpeg
• bool clipFlow = true;: defines whether to clip the optical flow larger than [-20 20] pixels and maps the interval [-20 20] to [0 255] in grayscale image space. If no clipping is performed the mapping to the image space is achieved by finding the frame-wise minimum and maximum displacement and mapping to [0 255] via an adaptive scaling, where the scale factors are saved as a binary file to out_path.

Example:

./brox_flow gpuID=0 type=1