Stereo Recordings in FreePBX

By default, call recordings in FreePBX are captured in mono WAV format. However, modern AI-driven conversational intelligence and quality Assurance (QA) platforms typically require dual-channel (stereo) audio in lightweight formats like MP3 to accurately distinguish speakers and reduce transfer bandwidth.

With a custom post-processing script and a few minor adjustments to your global Asterisk variables, you can automatically convert FreePBX recordings to stereo MP3s without imposing significant CPU overhead on your PBX server.

NOTE: The configuration and script detailed below have been tested and verified on FreePBX 17 running on Debian 12.

Edit your globals_custom.conf file as follows:

SS=$

MONITOR_REC_OPTION = bD

MIXMON_FORMAT = raw

MIXMON_POST=/usr/local/bin/mix-stereo.sh ${SS}{CALLFILENAME}.${SS}{MON_FMT}

Create /usr/local/bin/mix-stereo.sh

#!/usr/bin/env bash

set -e

# Validate input

if [ -z "${1:-}" ]; then

    echo "Error: No input file argument provided." >&2

    exit 1

fi

IN_FILE="$1"

OUT_FILE="${IN_FILE%.raw}.mp3"

TODAY=$(date "+%Y-%m-%d")

DIR="/var/spool/asterisk/monitor/$(date "+%Y/%m/%d")"

# Encode to MP3 and update DB

if lame -r -s 8 --bitwidth 16 --signed --little-endian "$DIR/$IN_FILE" "$DIR/$OUT_FILE"; then

    MYSQL_PWD="**********" mysql -u freepbxuser -s -N -D asteriskcdrdb -e \

        "UPDATE cdr SET recordingfile='${OUT_FILE}' WHERE recordingfile='${IN_FILE}' AND calldate >= '${TODAY} 00:00:00'"

    rm -f "$DIR/$IN_FILE"

else

    echo "LAME encoding failed for $IN_FILE" >&2

    exit 1

fi

To wrap up, execute:

$sudo chmod +x /usr/local/bin/mix-stereo.sh

$sudo chown asterisk /usr/local/bin/mix-stereo.sh

$ asterisk -rvvvvc

asterisk*CLI> dialplan reload