Feature: Stereo Balance Presets

[turbidWaters]

@ebaauw Thanks a million tons for this plug-in!!!

Would it be possible to add a feature to include 2 or 3 balance presents for a stereo pair?

Why I need this: I have two different listening positions in my living room.

I know this can be tricky given the fact that stereo pairs can be created and separated dynamically, plus it may require complicated changes in the config.json, and I see that you are (rightly) averse to changes/additions to the config.json. So, I am making this request hoping youll be able to come up with something sometime! and solve this annoying process, to have to change the balance every time I shift listening position, in the sonos app. Perhaps a siri command or scene would be stereo nirvana!

[ebaauw]

I've been wanting to support Balance for a long time, see #7, but it's quite challenging:

1. There isn't a Balance endpoint on the zoneplayers. Instead they seem to expose three Volume "channels", Master, RF and LF. The Sonos app adjusts the RF and/or LF channel volume when changing the Balance. A balance of 0% (middle) sets both channels to 100%; a balance of -100% (left) sets the right channel to 0%; and a balance of 100% (right) sets the left channel to 0%.;
2. I still haven't been able to figure out how to determine if a zone supports Balance. All zones seem to report the three Volume channels, irrespective of whether they support Balance. It's not just supported for stereo pairs, but also for the Connect. Counter-intuitively, it's not supported for the Playbar.

Ad 1) In line with the Sonos app, I've exposed Balance in the Speaker service as a percentage from -100% to 100%, in steps of 5%. As this is a custom characteristic, neither Apple's Home app nor Siri support this. However, you should be able to include this in a HomeKit scene using Eve, and then recall the scene from Siri.

Ad 2) I added logic to see if a zone is has slave zoneplayers. Afaik this is only the case for stereo pairs and home theatre setups. I already whitelisted the home theatre players (like PlayBase and PlayBar), so I won't expose Balance for home theatre setups. Also, I added a whitelist for zoneplayers that natively support stereo channels, like the Sonos Connect.

[ebaauw]

In v0.3.14.

[turbidWaters]

@ebaauw, thank you for the patient response and for pointing me in the right direction. Apologies for not writing in earlier.

I haven't tried any other home app except the one from apple. Will give it a try and report back.

And thanks for this great plugin!