scans one mp3 per directory and prints files with low bitrate

find-low-bitrate.sh

#!/bin/bash

scanfile ()
{
    FILE="${1//[$'\n']}"   # drop newline from argument
    BITRATE=$(/usr/bin/mediainfo "$FILE" --Output=JSON | jq '.media.track[0].OverallBitRate')
    BITRATE="${BITRATE//[$'\"']}"   # remove "
    if [[ $BITRATE -lt "130000" ]]; then
        echo $BITRATE "    " $FILE
    fi
}

scan ()
{
    export -f scanfile
    find "$1" -name '*.mp3' -type f -maxdepth 1 | head -1 | xargs -0 -P4 -I {} bash -c 'scanfile "$@"' _ {}
}

export -f scan scanfile

find . -type d -print0 | xargs -0 -P4 -I {} bash -c 'scan "$@"' _ {}