scripts/crossfade.sh

   1 #!/bin/bash
   2 #
   3 # crossfade.sh
   4 #
   5 # Creates two new files that when played together have a crossfade
   6 # of $1 seconds.  This means that $1/2 of the crossfade is in
   7 # the 1st file and $1/2 in the second file.  Can be used to
   8 # make audio CD's with a 0 second pregap between songs to
   9 # have one song flow into the next; yet still be able to skip
  10 # around the CD with minimal loss of song.
  11 #
  12 # Filenames are specified as $2 and $3.
  13 #
  14 # $4 is optional and specifies if a fadeout should be performed on
  15 # first file.  Can be yes/no/auto.
  16 # $5 is optional and specifies if a fadein should be performed on
  17 # second file. Can be yes/no/auto
  18 #
  19 # Example: $0 10 infile1.wav infile2.wav auto auto
  20 #
  21 # By default, the script attempts to guess if the audio files
  22 # already have a fadein/out on them or if they just have really
  23 # low volumes that won't cause clipping when mixxing.  If this
  24 # is not detected then the script will perform a fade in/out to
  25 # prevent clipping.
  26 #
  27 # The user may specify "yes" or "no" to force the fade in/out
  28 # to occur.  They can also specify "auto" which is the default.
  29 #
  30 # Crossfaded file $2 is prepended with cfo_ and $3 is prepended
  31 # with cfi_.
  32 #
  33 # Original script from Kester Clegg.  Mods by Chris Bagwell to show
  34 # more examples of sox features.
  35 #
  36
  37 SOX=../src/sox
  38
  39 if [ "$3" == "" ]; then
  40     echo "Usage: $0 crossfade_seconds first_file second_file [ fadeout ] [ fadein ]"
  41     echo
  42     echo "If a fadeout or fadein is not desired then specify \"no\" for that option.  \"yes\" will force a fade and \"auto\" will try to detect if a fade should occur."
  43     echo
  44     echo "Example: $0 10 infile1.wav infile2.wav auto auto"
  45     exit 1
  46 fi
  47
  48 fade_length=$1
  49 first_file=$2
  50 second_file=$3
  51
  52 fade_first="auto"
  53 if [ "$4" != "" ]; then
  54     fade_first=$4
  55 fi
  56
  57 fade_second="auto"
  58 if [ "$5" != "" ]; then
  59     fade_second=$5
  60 fi
  61
  62 fade_first_opts=
  63 if [ "$fade_first" != "no" ]; then
  64     fade_first_opts="fade t 0 0:0:$fade_length 0:0:$fade_length"
  65 fi
  66
  67 fade_second_opts=
  68 if [ "$fade_second" != "no" ]; then
  69     fade_second_opts="fade t 0:0:$fade_length"
  70 fi
  71
  72 echo "crossfade and concatenate files"
  73 echo
  74 echo  "Finding length of $first_file..."
  75 first_length=`$SOX "$first_file" 2>&1 -n stat | grep Length | cut -d : -f 2 | cut -f 1`
  76 echo "Length is $first_length seconds"
  77
  78 trim_length=`echo "$first_length - $fade_length" | bc`
  79 crossfade_split_length=`echo "scale=2; $fade_length / 2.0" | bc`
  80
  81 # Get crossfade section from first file and optionally do the fade out
  82 echo "Obtaining $fade_length seconds of fade out portion from $first_file..."
  83 $SOX "$first_file" -s -b 16 fadeout1.wav trim $trim_length $fade_first_opts
  84
  85 # When user specifies "auto" try to guess if a fadeout is needed.
  86 # "RMS amplitude" from the stat effect is effectively an average
  87 # value of samples for the whole fade length file.  If it seems
  88 # quite then assume a fadeout has already been done.  An RMS value
  89 # of 0.1 was just obtained from trail and error.
  90 if [ "$fade_first" == "auto" ]; then
  91     RMS=`$SOX fadeout1.wav 2>&1 -n stat | grep RMS | grep amplitude | cut -d : -f 2 | cut -f 1`
  92     should_fade=`echo "$RMS > 0.1" | bc`
  93     if [ $should_fade == 0 ]; then
  94         echo "Auto mode decided not to fadeout with RMS of $RMS"
  95         fade_first_opts=""
  96     else
  97         echo "Auto mode will fadeout"
  98     fi
  99 fi
 100
 101 $SOX fadeout1.wav fadeout2.wav $fade_first_opts
 102
 103 # Get the crossfade section from the second file and optionally do the fade in
 104 echo "Obtaining $fade_length seconds of fade in portion from $second_file..."
 105 $SOX "$second_file" -s -b 16 fadein1.wav trim 0 $fade_length
 106
 107 # For auto, do similar thing as for fadeout.
 108 if [ "$fade_second" == "auto" ]; then
 109     RMS=`$SOX fadein1.wav 2>&1 -n stat | grep RMS | grep amplitude | cut -d : -f 2 | cut -f 1`
 110     should_fade=`echo "$RMS > 0.1" | bc`
 111     if [ $should_fade == 0 ]; then
 112         echo "Auto mode decided not to fadein with RMS of $RMS"
 113         fade_second_opts=""
 114     else
 115         echo "Auto mode will fadein"
 116     fi
 117 fi
 118
 119 $SOX fadein1.wav fadein2.wav $fade_second_opts
 120
 121 # Mix the crossfade files together at full volume
 122 echo "Crossfading..."
 123 $SOX -m -v 1.0 fadeout2.wav -v 1.0 fadein2.wav crossfade.wav
 124
 125 echo "Spliting crossfade into $crossfade_split_length lengths"
 126 $SOX crossfade.wav crossfade1.wav trim 0 $crossfade_split_length
 127 $SOX crossfade.wav crossfade2.wav trim $crossfade_split_length
 128
 129 echo "Trimming off crossfade sections from original files..."
 130
 131 $SOX "$first_file" -s -b 16 song1.wav trim 0 $trim_length
 132 $SOX "$second_file" -s -b 16 song2.wav trim $fade_length
 133
 134 echo "Creating crossfade files"
 135 $SOX song1.wav crossfade1.wav "cfo_${first_file}.wav"
 136 $SOX crossfade2.wav song2.wav "cfi_${second_file}.wav"
 137
 138 echo -e "Removing temporary files...\n"
 139 rm fadeout1.wav fadeout2.wav fadein1.wav fadein2.wav crossfade.wav crossfade1.wav crossfade2.wav song1.wav song2.wav
 140 mins=`echo "$trim_length / 60" | bc`
 141 secs=`echo "$trim_length % 60" | bc`
 142 echo "The crossfade occurs at around $mins mins $secs secs in $first_file"
 143