Closes the cold-boot + hot-swap gap A+B left open. When the real
sink's Format-param listener fires with a rate that doesn't match
the filter's currently-running rate, the daemon now rebuilds the
filter atomically and rebinds the slow AGC controller to the new
measurement ring + FilterControl.
What triggers a rebuild
- Cold-boot against an ALSA sink. `audio.rate` isn't in the
props dict, so the registry-capture path falls back to 48 kHz
and creates the filter at that rate. Tens of ms later the
Format listener fires with the real rate (say 96 kHz). If
different from the filter's current rate, post
`PwCommand::RebuildFilter`.
- Hot-swap. User runs `wpctl set-default <other-sink>` and the
new sink has a different native rate. `adopt_new_real_sink`
swaps the Format listener; the next param event from the new
node's negotiated Format triggers the same rebuild path.
What the rebuild does
- Snapshots `FilterInit` from the active profile under the
daemon lock, then drops the lock before touching PipeWire.
- Drops the old `Filter` (RAII tears down the two pw_streams
+ their listeners), then calls `Filter::create` at the new
rate. ~50–100 ms audio gap on the processed path during the
swap.
- Updates `daemon.filter_control` + `daemon.filter_sample_rate`
under the lock.
- `AgcController::rebind(new_consumer, new_control, new_rate)`
swaps the AGC's view atomically and rebuilds its `ebur128`
instance at the new rate.
- Runs `reevaluate_all` so any explicit links anchored at the
old filter's now-gone ports get re-pinned to the new
processed-sink ports on the next drain tick.
Plumbing
- New `PwCommand::RebuildFilter { sample_rate }`.
- `RoutingState` gains `bus_filter: Option<Filter>` (filter
ownership moves from `runtime::run`'s local into routing
state so the registry thread can swap it) and
`agc_controller: Option<Rc<RefCell<AgcController>>>` so the
rebuild can call `rebind` on the slow loop.
- `RoutingState::install_filter_rebuild_handles` is called once
from `runtime` after `start_routing` + `AgcController::new`.
- `PwContext::routing_state()` accessor exposes the
`Rc<RefCell<RoutingState>>` so runtime can install the
handles without threading them through `start_routing`'s
signature.
- The Format listener computes `need_rebuild = filter_sample_rate
!= Some(new_rate)` under the daemon lock, then sends the
`RebuildFilter` command on `daemon.pw_command_tx` if needed.
What doesn't change
- Steady-state: when the daemon boots and the rate hasn't
moved, no rebuild fires. The no-rebuild path is the common
case for users whose hardware is 48 kHz native; nothing about
their setup gets touched.
- Layer A taps: orthogonal to the bus path. The rebuild doesn't
touch `managed_streams`; existing taps keep their links.
Verified
- 191 tests still pass; clippy clean.
- Cold-boot against the dev Mbox (48 kHz native): filter
creates at 48 k, Format listener fires ~22 ms later
detecting 48 k → `need_rebuild = false` → no rebuild posted.
Status reports `processed.sample_rate = 48000`. The
no-rebuild path is the one most users will hit.
- Live rebuild against a non-48 kHz sink: not exercised in
this commit (I can't reliably fabricate a non-48 kHz null
sink via `pw-cli load-module` in the shell — same limitation
8d hit). The user's 96 kHz motherboard, once they activate
its card profile and set it as default, is the next test
target.
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