Splits a video file in a set of image files. Default image format is
jpeg which has good speed and compression. Use format = "png" for
losless images.
av_video_images(video, destdir = tempfile(), format = "jpg", fps = NULL)an input video
directory where to save the png files
image format such as png or jpeg, must be available from av_encoders()
sample rate of images. Use NULL to get all images.
For large input videos you can set fps to sample only a limited number
of images per second. This also works with fractions, for example fps = 0.2
will output one image for every 5 sec of video.