Generate and concatenate videos from images with ffmpeg in single command

Question

My goal is to generate a video from images. Let's say I have 2 images 1.png and 2.png .

I can do

ffmpeg -loop 1 1.png -t 3 1.mp4

ffmpeg -loop 1 2.png -t 5 2.mp4

to create a 3 second video from the first image and 5 second video from the second image.

Then, I merge the two videos using

ffmpeg -i 1.mp4 -I 2.mp4 -filter_complex "concat" final.mp4 

to create my final 8 second video.

This process seems extremely inefficient, and I feel I do not have to use all this processing power+disk reading/writing to create 2 intermediary video files when I only want the one final video.

Is there a way to execute this entire process in one ffmpeg command (efficiently)?

Answer 1

The most versatile way is to use the concat filter .

Perhaps an easy way out assuming that all the durations are nice numbers (eg, integer seconds like you have in your example), then you can acctually use concat muxer and repeat files to occupy the desired time span.

Using your example,

concat.txt (in the same directory as the images)

ffconcat version 1.0
# repeated 3 times for 3 seconds
file capture_1.jpg
file capture_1.jpg
file capture_1.jpg
# repeated 5 times for 5 seconds
file capture_2.jpg
file capture_2.jpg
file capture_2.jpg
file capture_2.jpg
file capture_2.jpg

FFmpeg command with input rate of 1 frame/second:

ffmpeg -f concat -safe 0 -r 1 -i concat.txt 

Obviously, this will get pretty ugly quickly but it does work.

If you are to script generating the concat file, you might as well go the filter route imo.

Answer 2

If your images are smoothly and continuously numbered ie (1.png, 2.png, 3.png) not (1.png 02.png 4.png) then run

ffmpeg -i %d.png -vf "setpts='eq(N\,0)*0+eq(N\,1)*3+eq(N\,2)*8',tpad=stop_mode=clone:stop_duration=2" out.mp4

In setpts, each image is assigned a timestamp that sets when it starts showing, so the image timestamp is equal to the cumulative duration of all earlier images. The tpad sets the duration of the final image. Add -r X just before out.mp4 to set a fps of X.