[feat](trx-rs): show live wfm stereo detect state

Co-authored-by: Codex <codex@openai.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

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

@@ -1265,6 +1265,12 @@ function render(update) {
       wfmDenoiseBtn.style.borderColor = on ? "" : "var(--accent-warn, #f0a500)";
       wfmDenoiseBtn.style.color = on ? "" : "var(--accent-warn, #f0a500)";
     }
+    if (wfmStFlagEl && typeof update.filter.wfm_stereo_detected === "boolean") {
+      const detected = update.filter.wfm_stereo_detected;
+      wfmStFlagEl.textContent = detected ? "ST" : "MO";
+      wfmStFlagEl.classList.toggle("wfm-st-flag-stereo", detected);
+      wfmStFlagEl.classList.toggle("wfm-st-flag-mono", !detected);
+    }
   }
   if (update.status && update.status.freq && typeof update.status.freq.hz === "number") {
     applyLocalTunedFrequency(update.status.freq.hz, true);
@@ -2559,6 +2565,7 @@ 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 wfmStFlagEl = document.getElementById("wfm-st-flag");
 const wfmDenoiseBtn = document.getElementById("wfm-denoise-btn");
 
 // Hide audio row if audio is not configured on the server

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 wfm-st-flag-wrap" aria-label="Stereo pilot status">
+                    <span id="wfm-st-flag" class="wfm-st-flag wfm-st-flag-mono">MO</span>
+                  </label>
                   <label class="wfm-control">Denoise
                     <button id="wfm-denoise-btn" type="button" class="status-input toggle-btn toggle-on">On</button>
                   </label>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/style.css

@@ -192,6 +192,34 @@ input.status-input, select.status-input { width: 100%; padding: 0.45rem 0.5rem;
   line-height: 1.2;
   box-sizing: border-box;
 }
+.wfm-st-flag-wrap {
+  min-width: 0;
+}
+.wfm-st-flag {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-width: 2.35rem;
+  padding: 0.45rem 0.5rem;
+  box-sizing: border-box;
+  border: 1px solid var(--border-light);
+  border-radius: 6px;
+  font-size: 0.9rem;
+  font-weight: 800;
+  line-height: 1.2;
+  letter-spacing: 0.04em;
+  background: var(--input-bg);
+}
+.wfm-st-flag-stereo {
+  color: #ff5c5c;
+  border-color: color-mix(in srgb, #ff5c5c 65%, var(--border-light));
+  background: color-mix(in srgb, #ff5c5c 14%, var(--input-bg));
+}
+.wfm-st-flag-mono {
+  color: var(--text-muted);
+  border-color: var(--border-light);
+  background: color-mix(in srgb, var(--input-bg) 92%, var(--panel-2));
+}
 .controls-col-center::after {
   content: "";
   display: block;

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

@@ -275,6 +275,8 @@ pub struct RigFilterState {
     pub wfm_stereo: bool,
     #[serde(default = "default_wfm_denoise")]
     pub wfm_denoise: bool,
+    #[serde(default)]
+    pub wfm_stereo_detected: bool,
 }
 
 fn default_wfm_deemphasis_us() -> u32 {

src/trx-protocol/src/codec.rs

@@ -300,6 +300,7 @@ mod tests {
                 wfm_deemphasis_us: 75,
                 wfm_stereo: true,
                 wfm_denoise: true,
+                wfm_stereo_detected: false,
             }),
             ..minimal_snapshot()
         })
@@ -338,6 +339,7 @@ mod tests {
                 wfm_deemphasis_us: 50,
                 wfm_stereo: true,
                 wfm_denoise: true,
+                wfm_stereo_detected: true,
             }),
             ..minimal_snapshot()
         };
@@ -347,6 +349,7 @@ mod tests {
         assert_eq!(f.bandwidth_hz, 12000);
         assert_eq!(f.fir_taps, 128);
         assert_eq!(f.wfm_deemphasis_us, 50);
+        assert!(f.wfm_stereo_detected);
     }
 
     fn minimal_snapshot() -> trx_core::rig::state::RigSnapshot {

src/trx-server/src/rig_task.rs

@@ -663,6 +663,7 @@ async fn refresh_state_with_retry(
 /// Read current state from the rig via CAT.
 async fn refresh_state_from_cat(rig: &mut Box<dyn RigCat>, state: &mut RigState) -> DynResult<()> {
     let (freq, mode, vfo) = rig.get_status().await?;
+    state.filter = rig.filter_state();
     state.control.enabled = Some(true);
     state.apply_freq(freq);
     state.apply_mode(mode);

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

@@ -405,6 +405,10 @@ pub struct WfmStereoDecoder {
     diff_denoise: MultibandStereoBlend,
     /// Whether multiband stereo denoising is active.
     denoise_enabled: bool,
+    /// Smoothed pilot-derived stereo detection strength in [0, 1].
+    stereo_detect_level: f32,
+    /// Hysteretic pilot-lock result used by the UI.
+    stereo_detected: bool,
     /// FM discriminator gain normalization.
     ///
     /// `demod_fm` outputs `atan2(…)/π ≈ 2·Δf/fs` for small deviations.
@@ -471,6 +475,8 @@ impl WfmStereoDecoder {
             deemph_r: Deemphasis::new(audio_rate.max(1) as f32, deemphasis_us),
             diff_denoise: MultibandStereoBlend::new(audio_rate.max(1) as f32),
             denoise_enabled,
+            stereo_detect_level: 0.0,
+            stereo_detected: false,
             fm_gain: composite_rate_f / (2.0 * 75_000.0),
             sum_hist: [0.0; 4],
             diff_hist: [0.0; 4],
@@ -509,6 +515,19 @@ impl WfmStereoDecoder {
 
             let pilot_mag = (i * i + q * q).sqrt().max(pilot_tone.abs());
             let stereo_blend = (pilot_mag * 40.0).clamp(0.0, 1.0);
+            let detect_coeff = if stereo_blend > self.stereo_detect_level {
+                0.0008
+            } else {
+                0.0002
+            };
+            self.stereo_detect_level += detect_coeff * (stereo_blend - self.stereo_detect_level);
+            if self.stereo_detected {
+                if self.stereo_detect_level < 0.35 {
+                    self.stereo_detected = false;
+                }
+            } else if self.stereo_detect_level > 0.6 {
+                self.stereo_detected = true;
+            }
 
             // --- RDS ---
             let rds_quality = (0.35 + pilot_mag * 20.0).clamp(0.35, 1.0);
@@ -619,6 +638,10 @@ impl WfmStereoDecoder {
     pub fn reset_rds(&mut self) {
         self.rds_decoder.reset();
     }
+
+    pub fn stereo_detected(&self) -> bool {
+        self.stereo_detected
+    }
 }
 
 /// Selects the demodulation algorithm for a channel.

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

@@ -568,6 +568,13 @@ impl ChannelDsp {
         self.wfm_decoder.as_ref().and_then(WfmStereoDecoder::rds_data)
     }
 
+    pub fn wfm_stereo_detected(&self) -> bool {
+        self.wfm_decoder
+            .as_ref()
+            .map(WfmStereoDecoder::stereo_detected)
+            .unwrap_or(false)
+    }
+
     pub fn reset_rds(&mut self) {
         if let Some(decoder) = &mut self.wfm_decoder {
             decoder.reset_rds();

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

@@ -495,6 +495,12 @@ impl RigCat for SoapySdrRig {
     }
 
     fn filter_state(&self) -> Option<RigFilterState> {
+        let wfm_stereo_detected = self
+            .pipeline
+            .channel_dsps
+            .get(self.primary_channel_idx)
+            .and_then(|dsp| dsp.lock().ok().map(|d| d.wfm_stereo_detected()))
+            .unwrap_or(false);
         Some(RigFilterState {
             bandwidth_hz: self.bandwidth_hz,
             fir_taps: self.fir_taps,
@@ -502,6 +508,7 @@ impl RigCat for SoapySdrRig {
             wfm_deemphasis_us: self.wfm_deemphasis_us,
             wfm_stereo: self.wfm_stereo,
             wfm_denoise: self.wfm_denoise,
+            wfm_stereo_detected,
         })
     }