mp3merge

## Merge multiple MP3 files into one MP3
if ! test $# -ne 0
then
  echo "usage: $0 merged.mp3 file1.mp3 file2.mp3 ..."
  exit 1
fi

# Tested with files produced by ripit.  Install lame first for 
# mp3 support, then ripit will read and encode the tracks from 
# the CD.  Take caution that the names used by ripit will have 
# correct alphabetical name sorting.
# ripit -o `pwd` && eject

# update id3 tags with
# id3v2

#Environment and temp files
set -o errexit
tmp_mp1=$(mktemp).mp3
tmp_mp2=$(mktemp).mp3
trap '
rm -f $tmp_mp1
rm -f $tmp_mp2
set +o xtrace
set +o errexit
' EXIT
set -o xtrace

final_mp3=$1
shift 1

# merge all mp3 files to tmp_mp1
mpgtx -j -o $tmp_mp1 "$@"

#  merge alternatives
#
#  mp3merge Messes up the ic3 tags, result file is slightly larger
#mp3merge out.mp3 "$@"
#
#  find Handles large number of files but the result file is slightly larger
#find mp3directory -name "*.mp3" -print0|xargs -0 cat >> merged.mp3


## Corrects the headler length so many players show correct scrolling
ffmpeg -i $tmp_mp1 -acodec copy $tmp_mp2
rm $tmp_mp1

## Recalc the variable bit rate
# -allways required to avoid an error exit value (non variable bit rate mp3)
vbrfix -allways -ri1 -ri2 -lameinfo $tmp_mp2 $tmp_mp1

# if the mp3 is non-variable bit rate a destination file is not written
test -f $tmp_mp1 && mv $tmp_mp1 $tmp_mp2

#tmp_mp2 is the latest file in both cases
mv $tmp_mp2 "$final_mp3"

echo Finished : $final_mp3