abstract audio layering and panning with sox

layer_audio.sh

#!/bin/bash
#
# layer_audio.sh
# http://gist.github.com/428136
#
# take an input file, $1
# find length on input file
# snip short pieces of length $2
# layer all those pieces on top of each other
#
# USAGE = layer_audio.sh filename 150
# this will make a 2m and 30 second file.
#
#echo "this will work with mp3 files but it's much faster with .wav"
#echo "convert to wav first, then run this script"
# PUBLIC DOMAIN
# NORI
# GHTS
# RESE
# RVED

if [ "$3" == "" ]; then
    echo "Usage: layer_audio.sh filename 300 1.2 80"
    echo "layer_audio.sh filename lengthinseconds inittremspeed trm depth"
        exit 1
fi


filename=$1
snip_length=$2
tremspeed=$3
tremdepth=$4

#crossfade_duration=$4
# (| cut -d"." -f1) gets rid of the decimal value of seconds
length_seconds=`sox --info -D ${1} | cut -d"." -f1`

echo "original length=${length_seconds}"


echo "Pls enter anything:\c"
read name
echo "You entered $name."

pancount=0
tremcount=1
#tremdepth=85
number_snips=length_seconds/snip_length
let "number_snips+=1"
# generate the snippets
for ((  i = 0 ;  i <= number_snips ;  i++  ))
do


let "pancount%=5"
if [ "$pancount" == "0" ]
then
a=0.5; b=0.0;c=0.5;d=0.0;
echo $pancount means all left
#tremspeed=tremspeed/3
tremspeed=$(echo "scale=2; $tremspeed/1.2" | bc)
fi

if [ "$pancount" == "1" ]
then
echo $pancount means all right
a=0; b=0.5;c=0;d=0.5;
#tremspeed=tremspeed/2
tremspeed=$(echo "scale=2; $tremspeed/1.3" | bc)
fi

if [ "$pancount" == "2" ]
then
echo $pancount means 1/2 left
a=0.75; b=0;c=0.25;d=0.5;
#tremspeed=tremspeed/2
tremspeed=$(echo "scale=2; $tremspeed/1.25" | bc)
fi

if [ "$pancount" == "3" ]
then
echo $pancount means 1/2 right
a=0.5; b=0.25;c=0;d=0.75;
#tremspeed=tremspeed/2
tremspeed=$(echo "scale=2; $tremspeed/1.12" | bc)
fi

if [ "$pancount" == "4" ]
then
echo $pancount means centered
a=0.5; b=0;c=0;d=0.5;
#tremspeed=tremspeed/2
tremspeed=$(echo "scale=2; $tremspeed/1.1" | bc)
fi




let "counter=10000+$i"
let "pancount+=1"
let "tremcount%=9"
let "tremcount+=1"
#let "tremspeed=1/$tremcount"
echo tremspeed is $tremspeed
let "snip_start=${snip_length}*${i}"
sox $1 -c2 snip${counter:1}.wav trim $snip_start $2 mixer ${a},${b},${c},${d} tremolo $tremspeed $tremdepth 
echo "sox $1 snip${counter:1}.wav trim $snip_start $2"
done
echo "${counter:1} snippets generated"


# create dummy file
#sox $1 mix2.wav trim 0 1
sox -m snip*.wav --norm mix2.wav


new_length=`sox --info -D mix2.wav | cut -d"." -f1`

# you can change this part of the code to name the file differently.
# just change tla_ to whatever you want. 
#mv mix2.wav lyrd_${1}_${2}_${3}_${4}.wav
sox mix2.wav lyrd_${1}_${2}_${3}_${4}.mp3
#sox lyrd_${1}_${2}_${3}_${4}.wav lyrd_${1}_${2}_${3}_${4}.mp3

echo "assembled snippets"
echo "old length = ${length_seconds}, new length =${new_length}"
let "shortening_ratio=${length_seconds}/${new_length}"
echo "shortening factor = ${shortening_ratio}"

rm snip*.wav
echo "deleted snippets"


# fade in
# sox cutoff_file.wav improved_file.wav fade t 3 0 0
# fade out
# sox cutoff_file.wav improved_file.wav fade t 0 242 3
#
# so left pan of 0.5  is 1-0.5*(1-X),0,0.5(X),1-(0.5)?
#
# sox input.wav -c2 output.wav mixer l->l,l->r,r->l,r->r 
# sox input.wav -c2 unchanged.wav mixer 1,0,0,1 #unchanged