Setting a soundbar's volume through a TV that cannot read it

When an LG TV sends audio to a soundbar over ARC or optical, it can pass on volume-up and volume-down presses but cannot read or set the soundbar’s level. A volume slider in Home Assistant has nothing to bind to.

The workaround in the integration is to find zero the hard way: press volume-down enough times to be certain of reaching the bottom, then press volume-up the required number of times.

It only works if every press lands. On an LG SN4 soundbar, presses sent 220 to 240 ms apart were sometimes dropped. At 320 ms, 30 of 30 arrived.

It is offered as an experimental option, because the right interval will differ between soundbars and a dropped press leaves the volume wrong with no way to detect it.