portable shell script to compress videos with ffmpeg

compress_video

#!/bin/sh

print_usage() {
    echo "usage: compress_video <input_file>"
    echo "supported formats: mp4, webm, mkv, mov, avi, flv"
}

get_extension() {
    f="${1##*/}"
    case "$f" in
    .*) get_extension "${f#.}" && return 0 ;;
    esac
    case "$f" in
    .*.*) echo "${f#.}" ;;
    *.*) echo "${f#*.}" ;;
    *) return 0 ;;
    esac
}

get_filepath_without_extension() {
    ext=$(get_extension "$1")
    echo "${1%."$ext"}"
}

if [ $# -ne 1 ]; then
    echo "ERROR: input file is required"
    print_usage
    exit 1
fi

input_file="$1"
if [ ! -f "$input_file" ]; then
    echo "ERROR: input file '$input_file' does not exist"
    exit 1
fi

input_file_ext="$(get_extension "$input_file")"
output_file="$(get_filepath_without_extension "$input_file")_compressed.$input_file_ext"

# Default to libx264 and aac for unknown formats
vcodec="libx264"
acodec="aac"
format_opt=""

case $input_file_ext in
mp4)
    vcodec="libx264"
    acodec="aac"
    ;;
mov)
    vcodec="libx264"
    acodec="aac"
    format_opt="-f mov"
    ;;
webm)
    vcodec="libvpx-vp9"
    acodec="libopus"
    ;;
mkv)
    vcodec="libx265"
    acodec="libopus"
    ;;
avi|flv)
    vcodec="libx264"
    acodec="aac"
    format_opt="-f mp4"
    output_file="$(get_filepath_without_extension "$input_file")_compressed.mp4"
    ;;
*)
    echo "WARNING: unsupported video format - trying with default codecs"
    ;;
esac


echo "compressing video. this could take a while..."
if ffmpeg -i "$input_file" -c:v $vcodec -crf 23 -preset medium -c:a $acodec $format_opt "$output_file"; then
    echo "compression completed successfully"
    echo "output file: $output_file"
else
    echo "ERROR: compression failed"
    exit 1
fi