FFmpeg take screenshots from videos with variable duration

Question

I have bunch of videos which are rather long, so I take screenshots of 10th second (-ss 00:00:10). Sometimes videos are very short, like 5 seconds, and -ss 00:00:10 fails.

I don't have an option to compute video size as don't have an option to download them whole (videos are hosted on S3 and used as streams through CloudFront).

Maybe there are some built-in options that I overlooked?

What I really don't want to do is shorten -ss option gradually on fails so it would be the last resort.

Answer 1

One liner:

ffprobe -show_entries format=filename,duration -of default=noprint_wrappers=1:nokey=1 /path/to/input/file -loglevel 0 | awk 'BEGIN {RS="";FS="\n"}{system("ffmpeg -ss "$2/2" -i "$1" -vframes 1 out.png") }'

meaning:

use ffprobe to get the file duration in seconds then pipe to awk and execute the frame extraction ffmpeg command using a seek time equal to duration/2