[Squeezebox] Add balance controls

Sascha_ · July 4, 2021, 9:48am

Hi there,

I had just discovered that my squeezebox player (SqueezeAmp with squeezelite-esp32) shows balance control in the players audio settings (-25: full on right, 0 full on both, 25 full on left channel):

This enables the following use case for me (and maybe others):
I have one player located in the garden. One speaker is in the winter garden, one outside. Having this setting available to openhab would enable me to minimize sound emission to the needed location(s) and thus decreasing energy consumption and impact to my neighbors

Looking at the code, the change to add this to the binding seems pretty straight forward:

However, this seems to be a custom setting offered by my player as the CLI does not offer any balance setting:

github.com

elParaguayo/LMS-CLI-Documentation/blob/master/LMS-CLI.md

# Introduction

The Squeezebox Server provides a command-line interface to the players via TCP/IP. After starting the server, commands and queries may be sent by connecting to a specific TCP/IP port. The server will reply echoing the request (for commands) or by returning the requested data (for queries). By default, the Squeezebox Server will listen for connections on TCP/IP port 9090\. This format is designed for ease of integration into AMX, Crestron and other automation systems.

The end of line separator is line feed (<LF> ASCII decimal 10, hexadecimal 0x0A). The server accepts LF, CR or 0x00 (or any combination thereof) as end of line, and replies with whatever was used for the command. For strings, Squeezebox Server uses the UTF-8 character-set encoding.

To use the command line interface interactively, use the telnet command from your system's command prompt: _telnet localhost 9090_ and when it connects, you can start typing commands. Beware that the server expects parameters to be encoded using percent-style escaping (see below); " and \ are not supported as in shell-like environments.

For debugging purposes, CLI formatted commands can be sent using standard in and out. This support is only available on Unix platforms (MacOS X included), and must be enabled by launching the server with the "--stdio" command line option.

* * *

#### Changes starting from Squeezebox Server 7.6

*   Added tag 'M' for [songinfo](#0.1_songinfo) to return track musicmagic_mixable value.
*   Added tag 'c' for [songinfo](#0.1_songinfo) to return the track's coverid value, used for artwork URLs. If you were using the track's ID directly in artwork URLs, you should switch to using the coverid value.
*   Added ["pragma"](#0.1_pragma) command for changing SQLite behavior.
*   Added artist_id tagged parameter to [artists](#0.1_artists).
*   Added album_id tagged parameter to [albums](#0.1_albums).
*   Added sort order 'albumtrack' for [titles](#0.1_titles) to return the tracks in the order album-title, track-number.

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Is there anyone that can point me into the right direction?
Should I go for the http binding to change the setting?

Best,
Sascha

Sascha_ · February 26, 2022, 1:09pm

Being faced with this task again and being unsuccessful with the http binding, maybe @maniac103 or @mhilbush could point me in the right direction. I’m really willing to add this to the binding

Cheers,
Sascha

maniac103 · February 26, 2022, 1:54pm

If balance control is not part of the Server CLI API, I don’t think it is possible/meaningful to support this.
Is there any evidence of squeezelite-esp32 even supporting external control of this value, and how does the http binding relate to this?

mhilbush · February 26, 2022, 2:00pm

Exactly. And I don’t see anything the CLI API that lets you control the balance.

Sascha_ · February 27, 2022, 11:09am

Thank you both for your fast replies - you both helped me a lot to understand.

Indeed, the slimproto does not contain balance controls: SlimProto TCP protocol - SqueezeboxWiki

I’ve found the original thread where the feature has been discussed in this thread: Balance - Squeezebox : Community : Forums

They’ve used a simple yet effective approach in my opinion:

So, knowing that there is a gainL and gainR in slimproto, shall we add a balance option in audio? I think that could be easy, just a -N…N cursor then I would apply a scale down factor on gainL or gainR depending on that cursor (0 => no change, N => factor=0 on gainL, -N => factor=0 on gainR)

So, my next question is: How to add gain control to the binding?

EDIT: I’ve tried to control the balance using the http binding to POST a form using the balance data field and failed greatly

mhilbush · February 27, 2022, 3:10pm

I don’t see anything in the CLI docs that let you control L & R gain.

Sascha_ · March 2, 2022, 7:37pm

So to allow others to control balance too, here’s the DSL code for controlling it:

val String url	= "http://music:9000/material/settings/player/audio.html"
val String type	= "application/x-www-form-urlencoded"
val int timeout = 5000	// ms
val values = "pref_balance=-25&saveSettings=1"

val result = sendHttpPostRequest (url, type, values, timeout)

You need to replace the url to point to your LMS server. I don’t know if the URL is only valid if using the material theme so use with that piece aware.

I’ll mark this thread solved but I would be eager to know, if the implementation of this in the binding would be easy or difficult, thanks

mhilbush · March 2, 2022, 7:54pm

The binding uses the command line interface (CLI) for all interactions with the LMS. So, no, the above call directly into the user interface doesn’t fit into the model of how the binding works.