[feat](trx-rs): expose WFM stereo denoise toggle

Add a server-side toggle for the multiband stereo denoiser so it can be
enabled or disabled at runtime without restarting the server.

Backend (trx-backend-soapysdr):
- Add `denoise_enabled: bool` to `WfmStereoDecoder`; gate multiband
  blend behind it (falls back to uniform single-band blend when off)
- Add `set_denoise_enabled()` method on `WfmStereoDecoder`
- Propagate `wfm_denoise: bool` through `ChannelDsp`, `SdrPipeline`,
  and `SoapySdrRig`; add `set_wfm_denoise()` at each layer
- Include `wfm_denoise` in `filter_state()` so it flows into snapshots

Protocol / core (trx-core, trx-protocol, trx-server):
- Add `SetWfmDenoise(bool)` to `RigCommand` and `ClientCommand`
- Add default `set_wfm_denoise()` trait method to `RigCat`
- Handle `SetWfmDenoise` in `rig_task.rs` and update `RigFilterState`
- Add `wfm_denoise: bool` (default `true`) to `RigFilterState`

Frontend (trx-frontend-http):
- Add `POST /toggle_wfm_denoise` endpoint
- Add "Denoise On/Off" button next to the stereo/mono audio picker
- Sync button state from SSE filter snapshot (`update.filter.wfm_denoise`)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js

@@ -1252,6 +1252,12 @@ function render(update) {
     if (wfmDeemphasisEl && typeof update.filter.wfm_deemphasis_us === "number") {
       wfmDeemphasisEl.value = String(update.filter.wfm_deemphasis_us);
     }
+    if (wfmDenoiseBtn && typeof update.filter.wfm_denoise === "boolean") {
+      const on = update.filter.wfm_denoise;
+      wfmDenoiseBtn.textContent = on ? "On" : "Off";
+      wfmDenoiseBtn.style.borderColor = on ? "" : "var(--accent-warn, #f0a500)";
+      wfmDenoiseBtn.style.color = on ? "" : "var(--accent-warn, #f0a500)";
+    }
   }
   if (update.status && update.status.freq && typeof update.status.freq.hz === "number") {
     applyLocalTunedFrequency(update.status.freq.hz, true);
@@ -2546,6 +2552,7 @@ const audioRow = document.getElementById("audio-row");
 const wfmControlsCol = document.getElementById("wfm-controls-col");
 const wfmDeemphasisEl = document.getElementById("wfm-deemphasis");
 const wfmAudioModeEl = document.getElementById("wfm-audio-mode");
+const wfmDenoiseBtn = document.getElementById("wfm-denoise-btn");
 
 // Hide audio row if audio is not configured on the server
 fetch("/audio", { method: "GET" }).then((r) => {
@@ -2587,6 +2594,11 @@ if (wfmDeemphasisEl) {
     postPath(`/set_wfm_deemphasis?us=${encodeURIComponent(wfmDeemphasisEl.value)}`).catch(() => {});
   });
 }
+if (wfmDenoiseBtn) {
+  wfmDenoiseBtn.addEventListener("click", () => {
+    postPath("/toggle_wfm_denoise").catch(() => {});
+  });
+}
 
 function updateWfmControls() {
   if (!wfmControlsCol) return;

src/trx-client/trx-frontend/trx-frontend-http/assets/web/index.html

@@ -165,6 +165,9 @@
                       <option value="mono">Mono</option>
                     </select>
                   </label>
+                  <label class="wfm-control">Denoise
+                    <button id="wfm-denoise-btn" type="button" class="status-input toggle-btn toggle-on">On</button>
+                  </label>
                 </div>
                 <div class="label"><span>WFM</span></div>
               </div>

src/trx-client/trx-frontend/trx-frontend-http/src/api.rs

@@ -486,6 +486,21 @@ pub async fn set_wfm_deemphasis(
     send_command(&rig_tx, RigCommand::SetWfmDeemphasis(query.us)).await
 }
 
+#[post("/toggle_wfm_denoise")]
+pub async fn toggle_wfm_denoise(
+    state: web::Data<watch::Receiver<RigState>>,
+    rig_tx: web::Data<mpsc::Sender<RigRequest>>,
+) -> Result<HttpResponse, Error> {
+    let enabled = state
+        .get_ref()
+        .borrow()
+        .filter
+        .as_ref()
+        .map(|f| f.wfm_denoise)
+        .unwrap_or(true);
+    send_command(&rig_tx, RigCommand::SetWfmDenoise(!enabled)).await
+}
+
 #[post("/toggle_aprs_decode")]
 pub async fn toggle_aprs_decode(
     state: web::Data<watch::Receiver<RigState>>,
@@ -698,6 +713,7 @@ pub fn configure(cfg: &mut web::ServiceConfig) {
         .service(set_bandwidth)
         .service(set_fir_taps)
         .service(set_wfm_deemphasis)
+        .service(toggle_wfm_denoise)
         .service(toggle_aprs_decode)
         .service(toggle_cw_decode)
         .service(set_cw_auto)

src/trx-core/src/rig/command.rs

@@ -34,5 +34,6 @@ pub enum RigCommand {
     SetBandwidth(u32),
     SetFirTaps(u32),
     SetWfmDeemphasis(u32),
+    SetWfmDenoise(bool),
     GetSpectrum,
 }

src/trx-core/src/rig/controller/handlers.rs

@@ -517,6 +517,7 @@ pub fn command_from_rig_command(cmd: RigCommand) -> Box<dyn RigCommandHandler> {
         | RigCommand::SetBandwidth(_)
         | RigCommand::SetFirTaps(_)
         | RigCommand::SetWfmDeemphasis(_)
+        | RigCommand::SetWfmDenoise(_)
         | RigCommand::GetSpectrum => Box::new(GetSnapshotCommand),
     }
 }

src/trx-core/src/rig/mod.rs

@@ -165,6 +165,16 @@ pub trait RigCat: Rig + Send {
         )))
     }
 
+    fn set_wfm_denoise<'a>(
+        &'a mut self,
+        _enabled: bool,
+    ) -> Pin<Box<dyn Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(std::future::ready(Err(
+            Box::new(response::RigError::not_supported("set_wfm_denoise"))
+                as Box<dyn std::error::Error + Send + Sync>,
+        )))
+    }
+
     /// Return the current filter state if this backend supports filter controls.
     fn filter_state(&self) -> Option<state::RigFilterState> {
         None

src/trx-core/src/rig/state.rs

@@ -271,12 +271,18 @@ pub struct RigFilterState {
     pub cw_center_hz: u32,
     #[serde(default = "default_wfm_deemphasis_us")]
     pub wfm_deemphasis_us: u32,
+    #[serde(default = "default_wfm_denoise")]
+    pub wfm_denoise: bool,
 }
 
 fn default_wfm_deemphasis_us() -> u32 {
     75
 }
 
+fn default_wfm_denoise() -> bool {
+    true
+}
+
 /// Spectrum data from SDR backends (FFT magnitude over the full capture bandwidth).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SpectrumData {

src/trx-protocol/src/codec.rs

@@ -298,6 +298,7 @@ mod tests {
                 fir_taps: 64,
                 cw_center_hz: 700,
                 wfm_deemphasis_us: 75,
+                wfm_denoise: true,
             }),
             ..minimal_snapshot()
         })
@@ -334,6 +335,7 @@ mod tests {
                 fir_taps: 128,
                 cw_center_hz: 700,
                 wfm_deemphasis_us: 50,
+                wfm_denoise: true,
             }),
             ..minimal_snapshot()
         };

src/trx-protocol/src/mapping.rs

@@ -51,6 +51,7 @@ pub fn client_command_to_rig(cmd: ClientCommand) -> RigCommand {
         ClientCommand::SetWfmDeemphasis { deemphasis_us } => {
             RigCommand::SetWfmDeemphasis(deemphasis_us)
         }
+        ClientCommand::SetWfmDenoise { enabled } => RigCommand::SetWfmDenoise(enabled),
         ClientCommand::GetSpectrum => RigCommand::GetSpectrum,
     }
 }
@@ -95,6 +96,7 @@ pub fn rig_command_to_client(cmd: RigCommand) -> ClientCommand {
         RigCommand::SetWfmDeemphasis(deemphasis_us) => {
             ClientCommand::SetWfmDeemphasis { deemphasis_us }
         }
+        RigCommand::SetWfmDenoise(enabled) => ClientCommand::SetWfmDenoise { enabled },
         RigCommand::GetSpectrum => ClientCommand::GetSpectrum,
     }
 }

src/trx-protocol/src/types.rs

@@ -39,6 +39,7 @@ pub enum ClientCommand {
     SetBandwidth { bandwidth_hz: u32 },
     SetFirTaps { taps: u32 },
     SetWfmDeemphasis { deemphasis_us: u32 },
+    SetWfmDenoise { enabled: bool },
     GetSpectrum,
 }
 

src/trx-server/src/rig_task.rs

@@ -462,6 +462,16 @@ async fn process_command(
             let _ = ctx.state_tx.send(ctx.state.clone());
             return snapshot_from(ctx.state);
         }
+        RigCommand::SetWfmDenoise(enabled) => {
+            if let Err(e) = ctx.rig.set_wfm_denoise(enabled).await {
+                return Err(RigError::communication(format!("set_wfm_denoise: {e}")));
+            }
+            if let Some(f) = ctx.state.filter.as_mut() {
+                f.wfm_denoise = enabled;
+            }
+            let _ = ctx.state_tx.send(ctx.state.clone());
+            return snapshot_from(ctx.state);
+        }
         RigCommand::SetCenterFreq(freq) => {
             if let Err(e) = ctx.rig.set_center_freq(freq).await {
                 return Err(RigError::communication(format!("set_center_freq: {e}")));

src/trx-server/trx-backend/trx-backend-soapysdr/src/demod.rs

@@ -370,6 +370,8 @@ pub struct WfmStereoDecoder {
     deemph_r: Deemphasis,
     /// Multiband stereo blending applied at audio rate to the L-R diff channel.
     diff_denoise: MultibandStereoBlend,
+    /// Whether multiband stereo denoising is active.
+    denoise_enabled: bool,
     /// Previous filtered sum/diff composite samples used for linear interpolation.
     prev_sum: f32,
     /// Unblended L-R diff at the previous composite sample, for interpolation.
@@ -391,6 +393,7 @@ impl WfmStereoDecoder {
         audio_rate: u32,
         output_channels: usize,
         deemphasis_us: u32,
+        denoise_enabled: bool,
     ) -> Self {
         let composite_rate_f = composite_rate.max(1) as f32;
         let output_phase_inc = audio_rate.max(1) as f64 / composite_rate.max(1) as f64;
@@ -419,6 +422,7 @@ impl WfmStereoDecoder {
             deemph_l: Deemphasis::new(audio_rate.max(1) as f32, deemphasis_us),
             deemph_r: Deemphasis::new(audio_rate.max(1) as f32, deemphasis_us),
             diff_denoise: MultibandStereoBlend::new(audio_rate.max(1) as f32),
+            denoise_enabled,
             prev_sum: 0.0,
             prev_diff: 0.0,
             prev_blend: 0.0,
@@ -491,11 +495,15 @@ impl WfmStereoDecoder {
 
             // --- Deemphasis + DC block + output ---
             if self.output_channels >= 2 {
-                // Apply multiband stereo denoising at audio rate.
+                // Apply multiband or single-band stereo blend at audio rate.
-                // Higher frequency bands of the diff are attenuated more aggressively
+                let diff_denoised = if self.denoise_enabled {
-                // when the pilot is weak, reducing stereo noise without collapsing
+                    // Multiband: attenuates high-frequency diff more aggressively
-                // the low-frequency stereo image.
+                    // when the pilot is weak, preserving the low-frequency stereo image.
-                let diff_denoised = self.diff_denoise.process(diff_i, blend_i);
+                    self.diff_denoise.process(diff_i, blend_i)
+                } else {
+                    // Single-band: uniform blend across all frequencies.
+                    diff_i * blend_i
+                };
                 let left = self.dc_l
                     .process(self.deemph_l.process((sum_i + diff_denoised) * 0.5))
                     .clamp(-1.0, 1.0);
@@ -516,6 +524,10 @@ impl WfmStereoDecoder {
         output
     }
 
+    pub fn set_denoise_enabled(&mut self, enabled: bool) {
+        self.denoise_enabled = enabled;
+    }
+
     pub fn rds_data(&self) -> Option<RdsData> {
         self.rds_decoder.snapshot()
     }

src/trx-server/trx-backend/trx-backend-soapysdr/src/dsp.rs

@@ -309,6 +309,8 @@ pub struct ChannelDsp {
     fir_taps: usize,
     /// WFM deemphasis time constant in microseconds.
     wfm_deemphasis_us: u32,
+    /// Whether multiband stereo denoising is enabled for WFM.
+    wfm_denoise: bool,
     /// Decimation factor: `sdr_sample_rate / audio_sample_rate`.
     pub decim_factor: usize,
     /// Number of PCM channels emitted in each frame.
@@ -409,6 +411,7 @@ impl ChannelDsp {
                     self.audio_sample_rate,
                     self.output_channels,
                     self.wfm_deemphasis_us,
+                    self.wfm_denoise,
                 ));
             }
         } else {
@@ -429,6 +432,7 @@ impl ChannelDsp {
         frame_duration_ms: u16,
         audio_bandwidth_hz: u32,
         wfm_deemphasis_us: u32,
+        wfm_denoise: bool,
         fir_taps: usize,
         pcm_tx: broadcast::Sender<Vec<f32>>,
     ) -> Self {
@@ -473,6 +477,7 @@ impl ChannelDsp {
             audio_bandwidth_hz,
             fir_taps: taps,
             wfm_deemphasis_us,
+            wfm_denoise,
             decim_factor,
             output_channels,
             frame_buf: Vec::with_capacity(frame_size + output_channels),
@@ -493,6 +498,7 @@ impl ChannelDsp {
                     audio_sample_rate,
                     output_channels,
                     wfm_deemphasis_us,
+                    wfm_denoise,
                 ))
             } else {
                 None
@@ -538,6 +544,13 @@ impl ChannelDsp {
         self.rebuild_filters(true);
     }
 
+    pub fn set_wfm_denoise(&mut self, enabled: bool) {
+        self.wfm_denoise = enabled;
+        if let Some(decoder) = &mut self.wfm_decoder {
+            decoder.set_denoise_enabled(enabled);
+        }
+    }
+
     pub fn rds_data(&self) -> Option<RdsData> {
         self.wfm_decoder.as_ref().and_then(WfmStereoDecoder::rds_data)
     }
@@ -676,6 +689,7 @@ impl SdrPipeline {
         output_channels: usize,
         frame_duration_ms: u16,
         wfm_deemphasis_us: u32,
+        wfm_denoise: bool,
         channels: &[(f64, RigMode, u32, usize)],
     ) -> Self {
         const IQ_BROADCAST_CAPACITY: usize = 64;
@@ -697,6 +711,7 @@ impl SdrPipeline {
                 frame_duration_ms,
                 audio_bandwidth_hz,
                 wfm_deemphasis_us,
+                wfm_denoise,
                 fir_taps,
                 pcm_tx.clone(),
             );
@@ -945,7 +960,7 @@ mod tests {
     fn channel_dsp_processes_silence() {
         let (pcm_tx, _pcm_rx) = broadcast::channel::<Vec<f32>>(8);
         let mut dsp =
-            ChannelDsp::new(0.0, &RigMode::USB, 48_000, 8_000, 1, 20, 3000, 75, 31, pcm_tx);
+            ChannelDsp::new(0.0, &RigMode::USB, 48_000, 8_000, 1, 20, 3000, 75, true, 31, pcm_tx);
         let block = vec![Complex::new(0.0_f32, 0.0_f32); 4096];
         dsp.process_block(&block);
     }
@@ -954,7 +969,7 @@ mod tests {
     fn channel_dsp_set_mode() {
         let (pcm_tx, _) = broadcast::channel::<Vec<f32>>(8);
         let mut dsp =
-            ChannelDsp::new(0.0, &RigMode::USB, 48_000, 8_000, 1, 20, 3000, 75, 31, pcm_tx);
+            ChannelDsp::new(0.0, &RigMode::USB, 48_000, 8_000, 1, 20, 3000, 75, true, 31, pcm_tx);
         assert_eq!(dsp.demodulator, Demodulator::Usb);
         dsp.set_mode(&RigMode::FM);
         assert_eq!(dsp.demodulator, Demodulator::Fm);
@@ -969,6 +984,7 @@ mod tests {
             1,
             20,
             75,
+            true,
             &[(200_000.0, RigMode::USB, 3000, 64)],
         );
         assert_eq!(pipeline.pcm_senders.len(), 1);
@@ -977,7 +993,7 @@ mod tests {
 
     #[test]
     fn pipeline_empty_channels() {
-        let pipeline = SdrPipeline::start(Box::new(MockIqSource), 1_920_000, 48_000, 1, 20, 75, &[]);
+        let pipeline = SdrPipeline::start(Box::new(MockIqSource), 1_920_000, 48_000, 1, 20, 75, true, &[]);
         assert_eq!(pipeline.pcm_senders.len(), 0);
         assert_eq!(pipeline.channel_dsps.len(), 0);
     }

src/trx-server/trx-backend/trx-backend-soapysdr/src/lib.rs

@@ -39,6 +39,8 @@ pub struct SoapySdrRig {
     retune_cmd: Arc<std::sync::Mutex<Option<f64>>>,
     /// Current WFM deemphasis setting in microseconds.
     wfm_deemphasis_us: u32,
+    /// Whether multiband WFM stereo denoising is enabled.
+    wfm_denoise: bool,
 }
 
 impl SoapySdrRig {
@@ -115,6 +117,7 @@ impl SoapySdrRig {
             audio_channels,
             frame_duration_ms,
             wfm_deemphasis_us,
+            true, // wfm_denoise: enabled by default
             channels,
         );
 
@@ -182,6 +185,7 @@ impl SoapySdrRig {
             center_hz: hardware_center_hz,
             retune_cmd,
             wfm_deemphasis_us,
+            wfm_denoise: true,
         })
     }
 
@@ -460,12 +464,26 @@ impl RigCat for SoapySdrRig {
         })
     }
 
+    fn set_wfm_denoise<'a>(
+        &'a mut self,
+        enabled: bool,
+    ) -> Pin<Box<dyn std::future::Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(async move {
+            self.wfm_denoise = enabled;
+            if let Some(dsp_arc) = self.pipeline.channel_dsps.get(self.primary_channel_idx) {
+                dsp_arc.lock().unwrap().set_wfm_denoise(enabled);
+            }
+            Ok(())
+        })
+    }
+
     fn filter_state(&self) -> Option<RigFilterState> {
         Some(RigFilterState {
             bandwidth_hz: self.bandwidth_hz,
             fir_taps: self.fir_taps,
             cw_center_hz: 700,
             wfm_deemphasis_us: self.wfm_deemphasis_us,
+            wfm_denoise: self.wfm_denoise,
         })
     }