Input/Output Formats


Flowty uses the OpenCV VideoCapture API to load videos. It defaults to the FFmpeg backend.

Flowty is built to support reading from:

  • H263
  • H264
  • VP9
  • JPEG

For any of the video formats you can simply provide /path/to/video.ext as the src argument. To use a folder of sequentially numbered JPEGs as input you have to provide an image filename template such as /path/to/video_dir/frame_%06d.jpg (like specified in the VideoCapture constructor docs).


Currently only one output format is supported: splitting flow into u, v pairs, quantising them and storing them as JPEGs. The dest argument must be a python format template with two interpolations: {axis} and {index}.

  • {axis} will be replaced with u or v depending upon the direction of the flow field being written.
  • {index} will be replaced by the flow frame index being written, typically you’ll want to add some format specifiers to this to 0 pad it, e.g. {index:06d}.

An example template dest string is /data/flow/{axis}/frame_{index:06d}.jpg.