default: command not found

Question

Im new with linux so when when im facing this problem my first choice is to search it on google, but in these couple days still got no results. when im run this script on new instalation it will return "default: command not found". if im running this script on his machine it will run fine and playing all the videos with scrolling text.

here's the code:

#!/bin/bash

source /etc/atv.conf
export DISPLAY=:0

sleep 5

default $default &

while true; do

  sleep 1
  now=$(date +"%T")

  while read line
  do
    set -- "$line"
    IFS="#";
    declare -a array=($*)

    if [ ${array[0]} == $now ]; then
      duration=${array[1]}
      filename=${array[2]}
      filetype=${array[3]}

      default $filetype $filename $duration &

    fi
  done < $playlist

done

This script is to run video file with exist playlist using mplayer on ubuntu dekstop 12.04 LTS

What does the default at "default $default &" line refer to? for the $default is on the file.conf

$default=screen

for atv.conf

#ATV CONFIGURATION

#host
host=/home/atv

#media
media=CGK

#ATV Server
server=192.168.50.37

#Aeromedia Server
aeromedia=192.168.50.16

#Program matv_tv,matv,tv
program=matv_tv

#default tv|screen
default=screen

#if screen
default_file=$host/$media/tvp/22_Screen_Saver.mpg

#chn TV Channel
chn=38

#hw audio hardware 0,1,2,...
hw=2

#Media Folder
playlist=/home/atv/$media/$media.playlist
media_tvp=$host/$media/tvp
media_sb=$host/$media/sb
media_tvc=$host/$media/tvc
media_ds=$host/$media/ds
media_default=$host/default_screen

#TVC
res_tvc=1024x768
geo_tvc=0+0

#TVP
res_tvp=1024x598
geo_tvp=0+0

#Scrolling Banner
res_sb=1024x140
geo_sb=0+630

#TV
res_tv=1024x768
geo_tv=0+0

#Running Text
txt_geo=590
txt_size=26