Video handling

Read frames from a video file

The following command retrieves every 10th frame (-n) from the input video, will process a maximum of 100 frames (-m) and will process frames starting from 1000 (-f) and display the frames (example video):

wai-annotations convert \
  from-video-file-od \
    -i "./video/dashcam01.mp4" \
    -n 10 \
    -m 100 \
    -f 1000 \
  image-viewer-od

Read frames from a webcam

A webcam can also be used for obtaining frames, as the following example demonstrates (uses webcam with ID 0):

wai-annotations convert \
  from-webcam-od \
    -i 0 \
    -n 10 \
    -m 100 \
    -f 100 
  image-viewer-od

Generate a MJPEG video file of dissimilar frames

Videos contain a lot of frames and outputting or processing all of them is not a viable option in most cases. For that purpose, the skip-similar-frames plugin can be used for dropping frames that are too similar. The -t/--change-threshold parameter determines how sensitive to change the plugin is (ratio of pixels that are different between images). The subset of frames is written to a MJPEG video file with 1 frame/sec:

wai-annotations convert \
  from-video-file-od \
    -i "./video/some_video.mp4" \
  skip-similar-frames \
    --change-threshold 0.03 \ 
    --verbose \
  to-video-file-od \
    -f 1 \
    -o ./out.mjpeg