bash variable changes in loop with ffmpeg

Question

I wrote a skript to quickly create short preview clips from vides I recorded on timestamps that I found worth checking out later for cutting. My file with the timestamps is

Answer 1

ffmpeg reads from standard input, consuming data from $1 that was intended for the read command at the top of the loop. Redirect its standard input from /dev/null:

while IFS="#" read file timestamps; do
  filename="$file.MP4"
  for time in $timestamps; do
    ffmpeg -ss 00:${time}.0 -i "orig/${filename}" \
           -c copy -t 10 "preview/${file}_${time}.MP4" < /dev/null
  done
done < "$1"

echo does not read from standard input, which is why your modification made it appear to be working correctly.