#! /bin/sh

rate=16000

usage() {
    printf 'usage: %s [-r <rate>] src [dest]\n\nDefault rate: %d.\n' \
        "$(basename "$0")" \
        "$rate" \
        >&2 \
        ;
}

if [ "$1" = "-r" ]; then
    if [ "$#" -lt 2 ]; then
        usage
        exit 2
    fi

    rate=$2
    shift 2
fi

if [ "$#" -lt 1 ] || [ "$#" -gt 2 ]; then
    usage
    exit 2
fi

src=$1
dest=${2:-}
if [ -z "$dest" ]; then
    dest=${src%.*}.wav
fi

ffmpeg -hide_banner -i "$src" -ar "$rate" "$dest"