This blog post will explain how to use FFMPEG to merge a collection of images into a video. A sequence of png files will be used as input. The -c:v h264 will copy the mp4 codec to the output mp4 file. The -r 23.98 flag will encode the series of images into a video using the specified framerate.

ffmpeg -i img/%04d.png -c:v h264 -r 23.98 out.mp4