Bash Multimedia to Audio Conversions

#!/bin/bash
TRANSCODER=avconv
function __transcode_audio() {
    if test -f $2 -a -r $2 -a -w ${2%/*}
    then
        INPUT_FILE_PATH=$2
        BASE_FILENAME=${INPUT_FILE_PATH%.*}
        $TRANSCODER -i $INPUT_FILE_PATH -b:a 192K -vn $BASE_FILENAME.$1
        return $?
    else
        echo "Input/output error: File not readable or directory not writeable";
        return 74   # as defined in /usr/include/sysexits.h, EX_IOERR
    fi
}

function mkmp3() { __transcode_audio mp3 $1 ; return $? ; }
function mkogg() { __transcode_audio ogg $1 ; return $? ; }
function mkwav() { __transcode_audio wav $1 ; return $? ; }