#!/bin/bash

# this script is written by Peter Plessas
# and was published through http://plessas.mur.at
# It is released under the GNU/GPL license
# and requires sox
#
# This is version 20161211

# usage:
# mg_overlay infile outfile outdur_sec

# create a temporary work directory in the directory of the output file
mkdir -p /tmp/overlayTmpDir

# splice input file into segments of outdur_sec length and store into temporary directory
sox "$1" /tmp/overlayTmpDir/output.wav trim 0 $3 : newfile : restart

# mix splices together and normalize
sox -m "/tmp/overlayTmpDir/output*.wav" "$2" norm

# remove temporary directory
rm -r /tmp/overlayTmpDir

# TODO
# make this work without tmp dir and use sox's stdin function.
# due to the creation/deletion of overlayTmpDir only one invocation of this script can be active
# howto create a unique directory name?
# check for correct number and type of arguments, if files and directories are writeable and if awk and sox(i) are installed
# suppress SoX warnings