Rooted devices can bring back volume control for Cast speaker groups
Sonos filed two lawsuits against Google in January 2020, saying the company stole its multi-room speaker technology and infringed on 100 patents. The United States International Trade Commission ruled earlier this month that Google had indeed infringed on Sonos patents, and with Google (so far) unwilling to pay for a patent license, the ability to control Cast speakers with the volume buttons on Android phones and tablets was removed. However, it seems like there’s a way to get the functionality back — as long as your Android device is rooted, anyway.
Esper published a blog post written by Mishaal Rahman on Friday, which details how Google changed the volume button behavior in Android. The first change that Google made to unsuccessfully avoid patent infringement was committed to AOSP (the Android Open Source Project) in late July, which blocked volume key presses from being sent to the media session (the app playing audio or video) if a Cast device was being used.
Google later changed volume controls again in Android 12 Release 26, which was pushed to Google phones as part of the January 2022 security patch (which Pixel 6 owners are still waiting for). The volume keys can once again control single Cast speakers, but controlling groups of speakers is still blocked. The flag “config_volumeAdjustmentForRemoteGroupSessions” is what controls this behavior — Google has it switched off on its Pixel phones, but it’s enabled by default in AOSP, and presumably companies that license Sonos patents (or aren’t infringing on them in the first place) can leave it on.
The good news is that it’s not too difficult to override this flag, as long as you have a rooted device. Google is using a Runtime Resource Overlay (RRO) on Pixel devices to change the value of the volume adjustment flag, so creating an RRO with a higher priority with the flag set to true should fix it. If Google hadn’t patched the non-root method for creating Overlays, root wouldn’t even be necessary. A Magisk module that changes the flag is available at the link below.