ffmpeg - images from video at different sections and incrementally numbered

Question

I am using ffmpeg to extract still images from a video. From a given time, for a given duration using the -ss and -t parameters.

ffmpeg -ss 00:10:01 -t 2 -i /Volumes/OO_8/VideoSource.mkv -qscale:v 2 -start_number  /Users/Olivier/Pictures/ScreenCaptures/ViewsOfNature-%4d.jpeg

(I start with the timestamp/duration first so that ffmpeg starts the demux at at that point.)

However, I want to use several starting points (for example, at 00:01:12 in, extract the images for 2 seconds; at 00:11:00 minutes in, extract the images for 4 seconds; etc.) I can do this manually, replacing the timestamp and duration, and moving the output images each time, but ideally I want to input the timestamps and durations all at once, and not overwrite the output images. Is there a way to do this? Perhaps with an external file with the timestamps/durations?

I am new to this, and prefer to do it with ffmpeg only, not use bash.

Answer 1

I don't see a way to do it with ffmpeg easily. There is a segment muxer but you can't set the duration of segments.

There's nothing stopping you from doing it like this, which I believe is fairly simple. Just create a text file containing a comma-separated list of start points and durations:

$ cat split.txt
00:01:05,5
00:06:10,2
00:08:25,1

And then in Bash:

count=1
while read -r -d ',' start duration; do
  ffmpeg -ss "$start" -i input.mp4 -t "$duration" "$count-output-%04d.jpg"
  (( count++ ))
done < split.txt

This will create output files starting with a unique number (1, 2, 3, …).