25mb.sh

#!/bin/bash
if [ "$#" -ne 1 ];
then
    echo "Usage:"
    echo "    25mb /path/to/video.mp4"
    exit 1
fi

video="$1"
filename=$(basename -- "$video")
filename="${filename%.*}"

# magic
kb=$(python -c "import math; print(math.floor(191700/math.ceil($(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$video"))));")

ffmpeg -y -i "$video" -c:v libx264 -b:v "${kb}k" -pass 1 -f mp4 /dev/null
ffmpeg -i "$video" -c:v libx264 -b:v "${kb}k" -pass 2 "${filename}_new.mp4"
printf "\n\nsaved to %s_new.mp4" "$filename"