For very recent versions of ffmpeg (roughly from the end of year 2013)
The following will create a video slideshow (using video codec libx264 or webm) from all the png images in the current directory. The command accepts image names numbered and ordered in series (img001.jpg, img002.jpg, img003.jpg) as well as random bunch of images.
(each image will have a duration of 5 seconds)
ffmpeg -r 1/5 -pattern_type glob -i '*.png' -c:v libx264 out.mp4 # x264 video
ffmpeg -r 1/5 -pattern_type glob -i '*.png' out.webm # WebM video
For older versions of ffmpeg
This will create a video slideshow (using video codec libx264 or webm) from series of png images, named img001.png, img002.png, img003.png, …
(each image will have a duration of 5 seconds)
ffmpeg -f image2 -r 1/5 -i img%03d.png -vcodec libx264 out.mp4 # x264 video
ffmpeg -f image2 -r 1/5 -i img%03d.png out.webm # WebM video
You may have to slightly modify the following commands if you have a very recent version of ffmpeg
This will create a slideshow in which each image has a duration of 15 seconds:
ffmpeg -f image2 -r 1/15 -i img%03d.png out.webm
If you want to create a video out of just one image, this will do (output video duration is set to 30 seconds):
ffmpeg -loop 1 -f image2 -i img.png -t 30 out.webm
If you don't have images numbered and ordered in series (img001.jpg, img002.jpg, img003.jpg) but rather random bunch of images, you might try this:
cat *.jpg | ffmpeg -f image2pipe -r 1 -vcodec mjpeg -i - out.webm
or for png images:
cat *.png | ffmpeg -f image2pipe -r 1 -vcodec png -i - out.webm
That will read all the jpg/png images in the current directory and write them, one by one, using the pipe, to the ffmpeg's input, which will produce the video out of it.
Important: All images in a series need to be of the same size (x and y dimensions) and format.
Explanation: By telling FFmpeg to set the input file's FPS option (frames per second) to some very low value, we made FFmpeg duplicate frames at the output and thus we achieved to display each image for some time on screen. You have seen, that you can set any fraction as framerate. 140 beats per minute would be -r 140/60.
Source: The FFmpeg wiki
For creating images from a video use
ffmpeg -i video.mp4 img%03d.png
This will create images named img001.png, img002.png, img003.png, …
