I'm trying to apply reverb by convolving with an impulse response in SoX. The following shell script does exactly what I want:
#!/usr/bin/env bash
#
# Convolve audio file with and impulse response (IR)
#
# Usage:
#
# applyReverb.sh <ir.wav> <audio.wav> <output.wav>
# IR duration (needed for zero-padding to prevent SoX from cutting
# the resulting audio after applying the FIR filter
IR_DUR=`soxi -D $1`
# read IR from wav, resample it if necessary, make sure is mono
# and save it as plain text (.dat format in SoX). Also reduces gain
# to prevent clipping later
sox --norm=-10 -c 1 $1 -r 44100 filter.dat
# extract the coeffients (second column, skipping the first 2 lines)
awk 'NR<3{next}{print $2}' filter.dat > filter.txt
# apply reverb using SoX's fir effect (need front zero-padding to for
# the extra samples due to the convolution
sox "|sox $2 -p pad $IR_DUR 0" --norm $3 fir filter.txt
The Question
How can I do this without the temporary files (filter.*)? I know the answer lies within the pipes, but I can't get it to work.
After some trial and error, I found what I was looking for. In case anyone out there is interested, this is my solution:
sox --norm=-10 -c 1 $1 -r 44100 -t dat - | awk 'NR<3{next}{print $2;}' | sox "|sox $2 -p pad $d $d" --norm $3 fir -