'''
  Sometimes it is useful to know the total number of video frames before starting to iterate.
  This is not possible using the default video reader in Sk-video.
  The snippet below shows how to do this using the FFMPEG reader instead.
'''

if osp.exists(video_path):
    vid_reader = skvideo.io.FFmpegReader(video_path) # NOTE: not the standard skvideo.io.vreader
else:
    raise IOError('Path to video not found: \n%s' % video_path)

# Knowing number of frames from FFMPEG metadata w/o without iterating over all frames
(numframe, _, _, _) = vid_reader.getShape() # numFrame x H x W x channels
videogen = vid_reader.nextFrame() # generator for iterating over all video frames