Crop Detection

3. 10. 2022

Idea1: Jump to the middle of the movie, scan just 5 seconds and be happy.

# movie duration/2 for crop detection
dur=$(ffprobe -v panic -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$1")
halfdur=$(bc <<< "$dur / 2.00")
howlong=$(bc <<< "$halfdur + 5") # seconds
# crop detection
crop="$(ffmpeg -ss "$halfdur" -to "$howlong" -i "$1" -vf cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tail -1)"
if [ -z "$crop" ]; then
    echo "Crop detection failed, exiting..."
    exit 1
fi

echo "$crop"

Idea2: Speed up (or skip frames) the film to be only 5 seconds long and detect that. After some experimentos this seems to be much slower, since it has to read lots of data.

test:

ffmpeg -t 1 -r 10000 -i huge.mxf -r 25 -an small.mp4

Will produce small.mp4 with length of 1s and 25fps (Inredibly speed-up huge.mxf), this could be used as a basis for crop detection.

video mine