Video Processing in R

This is a short demonstration on how to manipulate a video with image magick in R -

In this example you can reverse play one video. What this snippet of code will do is to read in the video as a sequence of frame by frame images in the format of a list - after, we will reverse the images in this list and export the video with its original frame rate. The end product will be a reverse played video! :) Note that the code below is ready to loop over a folder containing several videos !

There are also some little tricks to maintain the usage of ram low so that R doesn't crash

reverse_videos <- function(importpath, exportpath, thefps = 30){

### this function will generate a reverse played version of a video

### import path is the folder where the original videos are found;

### export path is where you want to export the videos.

### if not declared the thefps will default at 30.

if (!require('magick')) install.packages('magick'); library('magick')

## list videos in import folder

vpaths <- list.files(importpath, pattern = "mp4", full.names = TRUE)

## extract the names

vnames <- basename(vpaths)

for(v in seq_along(vpaths)){

gc() ## clean up the ram before starting a new video

vidz <- image_read_video(vpaths[v], fps = thefps) ## read up the video

image_write_video(rev(vidz), paste0(exportpath, "/", vnames[v]), framerate = thefps) ### write the rev video

rm(vidz) ## remove the video to free up space

}

}

That should do! You can also download this function from here