I. LICENSE

MIT License

Copyright (c) 2023 ArcSoundGuy

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

II. PURPOSE

Control volume for a group of Sonos speakers using a TV remote with HDMI CEC.

III. DESCRIPTION

The main script named sonos-volume.sh runs on a Linux server (RHEL8) and is called whenever 
the Sonos state changes on the local network.  The script then queries the Arc speaker for 
its volume and changes the volumes of group speakers to match.  Mute is supported.  This 
method works very well but does require a Linux server of some kind (either physical or 
virtual machine) to be running in your home.

An alternative method is to use a Logitech Harmony remote.  I used the Logitech Harmony 
method for two years.  The Logitech Harmony method works somewhat but has downsides.  The 
group speakers volume can become out of sync (louder or quieter) with the Arc in some cases.  
The group speakers can fall out of the group such as after updates or power loss.  The 
Logitech Harmony often won’t respond to volume requests which is a problem others have 
reported as well.  Non-IT people in a household find Logitech issues difficult to 
troubleshoot.  Logitech Harmony is no longer available for sale.

In my configuration, I use an AppleTV remote which changes the Arc sound using HDMI CEC.  
I have an Arc in the Living Room with four additional Sonos One speakers.  I also have an 
Arc in the Bed Room with two additional Sonos One speakers.  My goal is to have the Arc 
sound coming from all speakers in each room respectively.  I do not want a surround channel.  
Sonos speakers being networked is great and hopefully Sonos will add changing the group volume 
with a TV remote as an option since customers paying many dollars desire this feature and 
Sonos competitors may soon offer a solution to lure otherwise happy Sonos customers away.

IV. VOLUME CHANGE PROCESS DIAGRAM

Remote —> TV —> Arc Speaker —> Sonos API (webhook) —> Apache sonos.cgi —> sonos-volume.sh —> Group Speakers

V. SOFTWARE PRE-REQUISITES

The Linux server needs to have the following programs installed.

1. jq - for json parsing
2. curl
3. lockfile - Comes with procmail package
4. sed
5. A web server (tested with Apache)
6. Jishi Sonos API - https://github.com/jishi/node-sonos-http-api

VI. INSTALLATION STEPS

1. Install Sonos API https://github.com/jishi/node-sonos-http-api.  Add a webhook: 
"http://localhost:/sonos.cgi" to your settings.js.  I have included the entire settings.js 
file but you only need to add the webhook line to your existing settings.js file.  This API 
uses the webhook setting to send an event to Apache whenever the Sonos state changes on the 
local network.  The webhook setting calls sonos.cgi which then calls sonos-volume.sh.  This 
API also allows volume levels to be queried and changed by the sonos-volume.sh script.  

2. Install Apache and place sonos.cgi in your webroot and enable cgi (.cgi handler and 
ExecCGI in httpd.conf).  You may need to disable SELinux.  Sonos.cgi calls sonos-volume.sh.

3. Install sonos-volume.sh in /usr/local/bin.  Be sure to set executable permissions with 
chmod a+x /usr/local/bin/sonos-volume.sh.  The script actually sets the volume for speakers 
in the group.  For testing, you can run the sonos-volume.sh script from the Linux command line 
before setting an API webhook and before installing Apache/sonos.cgi.  Be sure to change the 
bottom of the script to set your speaker names.  Also, using the Sonos smartphone app is very 
helpful to monitor group membership and speaker volumes as you test your deployment.

VII. RELATED WORK

For a similar great project, see also https://github.com/ErikAlfredsson/sonos-sync-group-volume.