#!/bin/bash## crossfade.sh## Creates two new files that when played together have a crossfade# of $1 seconds.  This means that $1/2 of the crossfade is in# the 1st file and $1/2 in the second file.  Can be used to# make audio CD's with a 0 second pregap between songs to# have one song flow into the next; yet still be able to skip# around the CD with minimal loss of song.## Filenames are specified as $2 and $3.## $4 is optional and specifies if a fadeout should be performed on# first file.  Can be yes/no/auto.# $5 is optional and specifies if a fadein should be performed on# second file. Can be yes/no/auto## Example: $0 10 infile1.wav infile2.wav auto auto## By default, the script attempts to guess if the audio files# already have a fadein/out on them or if they just have really# low volumes that won't cause clipping when mixxing.  If this# is not detected then the script will perform a fade in/out to# prevent clipping.## The user may specify "yes" or "no" to force the fade in/out# to occur.  They can also specify "auto" which is the default.## Crossfaded file $2 is prepended with cfo_ and $3 is prepended# with cfi_.## Original script from Kester Clegg.  Mods by Chris Bagwell to show# more examples of sox features.# SOX=../src/sox if [ "$3" == "" ]; then    echo "Usage: $0 crossfade_seconds first_file second_file [ fadeout ] [ fadein ]"    echo    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."    echo    echo "Example: $0 10 infile1.wav infile2.wav auto auto"    exit 1fi fade_length=$1first_file=$2second_file=$3 fade_first="auto"if [ "$4" != "" ]; then    fade_first=$4fi fade_second="auto"if [ "$5" != "" ]; then    fade_second=$5fi fade_first_opts=if [ "$fade_first" != "no" ]; then    fade_first_opts="fade t 0 0:0:$fade_length 0:0:$fade_length"fi fade_second_opts=if [ "$fade_second" != "no" ]; then    fade_second_opts="fade t 0:0:$fade_length"fi echo "crossfade and concatenate files"echoecho  "Finding length of $first_file..."first_length=`$SOX --info -D "$first_file"`echo "Length is $first_length seconds" trim_length=`echo "$first_length - $fade_length" | bc`crossfade_split_length=`echo "scale=2; $fade_length / 2.0" | bc` # Get crossfade section from first file and optionally do the fade outecho "Obtaining $fade_length seconds of fade out portion from $first_file..."$SOX "$first_file" -e signed-integer -b 16 fadeout1.wav trim $trim_length $fade_first_opts # When user specifies "auto" try to guess if a fadeout is needed.# "RMS amplitude" from the stat effect is effectively an average# value of samples for the whole fade length file.  If it seems# quiet then assume a fadeout has already been done.  An RMS value# of 0.1 was just obtained from trial and error.if [ "$fade_first" == "auto" ]; then    RMS=`$SOX fadeout1.wav 2>&1 -n stat | grep RMS | grep amplitude | cut -d : -f 2 | cut -f 1`    should_fade=`echo "$RMS > 0.1" | bc`    if [ $should_fade == 0 ]; then        echo "Auto mode decided not to fadeout with RMS of $RMS"        fade_first_opts=""    else        echo "Auto mode will fadeout"    fifi $SOX fadeout1.wav fadeout2.wav $fade_first_opts # Get the crossfade section from the second file and optionally do the fade inecho "Obtaining $fade_length seconds of fade in portion from $second_file..."$SOX "$second_file" -e signed-integer -b 16 fadein1.wav trim 0 $fade_length # For auto, do similar thing as for fadeout.if [ "$fade_second" == "auto" ]; then    RMS=`$SOX fadein1.wav 2>&1 -n stat | grep RMS | grep amplitude | cut -d : -f 2 | cut -f 1`    should_fade=`echo "$RMS > 0.1" | bc`    if [ $should_fade == 0 ]; then        echo "Auto mode decided not to fadein with RMS of $RMS"        fade_second_opts=""    else        echo "Auto mode will fadein"    fifi $SOX fadein1.wav fadein2.wav $fade_second_opts # Mix the crossfade files together at full volumeecho "Crossfading..."$SOX -m -v 1.0 fadeout2.wav -v 1.0 fadein2.wav crossfade.wav echo "Spliting crossfade into $crossfade_split_length lengths"$SOX crossfade.wav crossfade1.wav trim 0 $crossfade_split_length$SOX crossfade.wav crossfade2.wav trim $crossfade_split_length echo "Trimming off crossfade sections from original files..." $SOX "$first_file" -e signed-integer -b 16 song1.wav trim 0 $trim_length$SOX "$second_file" -e signed-integer -b 16 song2.wav trim $fade_length echo "Creating crossfade files"$SOX song1.wav crossfade1.wav "cfo_${first_file}.wav"$SOX crossfade2.wav song2.wav "cfi_${second_file}.wav" echo -e "Removing temporary files...\n" rm fadeout1.wav fadeout2.wav fadein1.wav fadein2.wav crossfade.wav crossfade1.wav crossfade2.wav song1.wav song2.wavmins=`echo "$trim_length / 60" | bc`secs=`echo "$trim_length % 60" | bc`echo "The crossfade occurs at around $mins mins $secs secs in $first_file"