$ cat /usr/local/bin/a.sh
#!/bin/bash

cd /mnt/data/events/9 || exit 1

tmp="convert.mp4"

find -type f -iname '*-video.mp4' | while read filename; do
        echo "$filename: converting..."

        nice -n 3 ffmpeg -i $filename -vcodec h264 -threads 1 -b:v 3M -y $tmp >convert.tmp 2>&1

        if [ $? != 0 ]; then
                echo "$filename: failed to convert"
                continue
        fi

        echo "$filename: successfully converted"
done

$ /usr/local/bin/a.sh
./2021-04-27/23905/23905-video.mp4: converting...
./2021-04-27/23905/23905-video.mp4: successfully converted
1/24041-video.mp4: converting...
1/24041-video.mp4: failed to convert
./2021-04-27/24045/24045-video.mp4: converting...
./2021-04-27/24045/24045-video.mp4: successfully converted
21-04-27/24296/24296-video.mp4: converting...
21-04-27/24296/24296-video.mp4: failed to convert
./2021-04-27/23709/23709-video.mp4: converting...
./2021-04-27/23709/23709-video.mp4: successfully converted
273-video.mp4: converting...
273-video.mp4: failed to convert
./2021-04-27/24179/24179-video.mp4: converting...
^C

---

$ cat /usr/local/bin/c.sh
#!/bin/bash

cd /mnt/data/events/9 || exit 1

tmp="convert.mp4"

dummy()
{
        return
}

find -type f -iname '*-video.mp4' | while read filename; do
        echo "$filename: converting..."

        dummy

        if [ $? != 0 ]; then
                echo "$filename: failed to convert"
                continue
        fi

        echo "$filename: successfully converted"
done

$ /usr/local/bin/c.sh
./2021-04-27/23905/23905-video.mp4: converting...
./2021-04-27/23905/23905-video.mp4: successfully converted
./2021-04-27/23754/23754-video.mp4: converting...
./2021-04-27/23754/23754-video.mp4: successfully converted
./2021-04-27/23988/23988-video.mp4: converting...
./2021-04-27/23988/23988-video.mp4: successfully converted
./2021-04-27/23989/23989-video.mp4: converting...
./2021-04-27/23989/23989-video.mp4: successfully converted
./2021-04-27/24081/24081-video.mp4: converting...
./2021-04-27/24081/24081-video.mp4: successfully converted
./2021-04-27/24189/24189-video.mp4: converting...
./2021-04-27/24189/24189-video.mp4: successfully converted
./2021-04-27/24327/24327-video.mp4: converting...
./2021-04-27/24327/24327-video.mp4: successfully converted
./2021-04-27/23593/23593-video.mp4: converting...
./2021-04-27/23593/23593-video.mp4: successfully converted
./2021-04-27/24244/24244-video.mp4: converting...
./2021-04-27/24244/24244-video.mp4: successfully converted
./2021-04-27/23584/23584-video.mp4: converting...
./2021-04-27/23584/23584-video.mp4: successfully converted
./2021-04-27/23963/23963-video.mp4: converting...