On this page:

As part of a personal project I’ve been toying with I wanted to be able to generate images using a naming convention where the image name would describe the frame order. For example: frame-1.png, frame-2.png, … frame-100.png.

The directory the frame images were stored in were, themselves, named according to an ordered convention as well. The entire structure would look like:

+ gen-1
    - frame-1.png
    - frame-2.png
    - frame-3.png
+ gen-50
    - frame-1.png
    - frame-2.png
    - frame-3.png
+ gen-100
    - frame-1.png
    - frame-2.png
    - frame-3.png

This structure would serve as the input to a tool that will create 3 videos: gen-1.mp4, gen-50.mp4, and gen-100.mp4 each of which are 3 frames long (in reality the videos are longer but it just means more frame files).

I’m not the command line guru so this is the approach I took to figure this out:

Generate a Video From a Directory of Images

I started by trying to find a command, using ffmpeg, that would create a video for the directory gen-1 with the following properties:

Feature Desired
FPS 30
Format mp4
Resolution 1280x1280
ffmpeg -framerate 30 -f image2 -s 1280x1280 -i gen-1/frame-%d.png -vcodec libx264 -pix_fmt yuv420p -y gen-1.mp4
Argument Value Outcome
-framerate 30 Sets the framerate to 30
-f image2 The input format is images
-s 1280x1280 The frame size of the input images
-i gen-1/frame-%d.png The input frame images
-vcodec libx264 Encodes using the x264 video format (mp4)
-pix_fmt yuv420p Without this the video wouldn’t load in Quicktime
-y none Overwrites output files
gen-1.mp4 none The name of the output file

List all the Directories

find gen-* -type d

This command will identify the three directories following the convention described above.

% find gen-* -type d 

Tie Them Together

Now that I can produce the video - but need the directory names - and I can produce a list of directory names, I want to tie them together.

find gen-* -type d | xargs -I {} echo {} 

I used xargs to pipe the output of find into the input of xargs and then kick off the child process - in this example simply echoing the inputs.

So let’s stitch them together

find gen-* -type d | xargs -I {} ffmpeg -framerate 30 -f image2 -s 1280x1280 -i {}/frame-%d.png -vcodec libx264 -pix_fmt yuv420p -y {}.mp4

And the output is a video that does exactly what I had hoped.