[fix](trx-wefax): revert slant correction and silent-drop verifier

Per-line cross-correlation slant tracking (d487711) shifted every line by up to \u00b16 samples with a 0.01 deadband, so image-content and shot-noise variance dominated the drift estimate and garbled the output. The unverified-reception verifier (76f9953) then silently dropped the entire capture at line 40 when correlation never settled. Together they made valid transmissions look like decoder failures.

Revert both: fixed-period extraction restored, carrier-loss watchdog ungated, transition_to_receiving no longer takes a verified flag. Phasing timeout fallback and variance-based auto-start kept. This returns the decoder to fldigi-equivalent behaviour.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

Cargo.lock

@@ -3178,6 +3178,7 @@ version = "0.1.0"
 dependencies = [
  "actix-web",
  "actix-ws",
+ "base64",
  "brotli 7.0.0",
  "bytes",
  "dirs",
@@ -3261,6 +3262,7 @@ dependencies = [
 name = "trx-server"
 version = "0.1.0"
 dependencies = [
+ "base64",
  "bytes",
  "chrono",
  "clap",

src/decoders/trx-wefax/src/config.rs

@@ -19,9 +19,6 @@ pub struct WefaxConfig {
     pub output_dir: Option<String>,
     /// Whether to emit line-by-line progress events.
     pub emit_progress: bool,
-    /// Whether to continuously track and correct sample-clock drift
-    /// (line-to-line cross-correlation) to remove image slant.
-    pub slant_correction: bool,
 }
 
 impl Default for WefaxConfig {
@@ -33,7 +30,6 @@ impl Default for WefaxConfig {
             deviation_hz: 400.0,
             output_dir: None,
             emit_progress: true,
-            slant_correction: true,
         }
     }
 }

src/decoders/trx-wefax/src/decoder.rs

@@ -43,26 +43,11 @@ const LINE_CORR_NOISE_THRESHOLD: f32 = 0.2;
 /// fldigi's line-to-line correlation check for automatic stop.
 const LINE_CORR_NOISE_LINES: u32 = 30;
 
-/// Pearson correlation above which adjacent lines are considered good
-/// evidence of real image content. Used to verify unverified auto-starts.
-const LINE_CORR_IMAGE_THRESHOLD: f32 = 0.5;
-
-/// Number of consecutive well-correlated lines that verify an unverified
-/// reception (i.e. an auto-start from variance detection). Low enough to
-/// engage quickly on real imagery.
-const VERIFY_HIGH_CORR_STREAK: u32 = 5;
-
-/// Maximum number of scan lines the verifier waits for before giving up on
-/// an unverified reception. Roughly 20 s at 120 LPM. If no high-correlation
-/// streak appears by then, the buffered content is dropped and we return
-/// to Idle without saving anything.
-const VERIFY_TIMEOUT_LINES: u32 = 40;
-
 /// Maximum number of scan-line-equivalent sample windows to wait for phasing
-/// lock before falling through to Receiving (unverified). Typical WEFAX
-/// phasing lasts ~30 s; if the phasing detector hasn't converged by then
-/// we give up on alignment and let the correlation verifier decide whether
-/// the content that follows is a real image. At 120 LPM this is ~30 s.
+/// lock before falling through to Receiving. Typical WEFAX phasing lasts
+/// ~30 s; if the phasing detector hasn't converged by then we give up on
+/// alignment and let the carrier-loss watchdog decide whether the content
+/// that follows is real imagery. At 120 LPM this is ~30 s.
 const PHASING_TIMEOUT_LINES: u32 = 60;
 
 /// WEFAX decoder output event.
@@ -117,18 +102,10 @@ pub struct WefaxDecoder {
     /// `LINE_CORR_NOISE_LINES` the decoder auto-finalizes the in-progress
     /// image (carrier dropped / tx ended without an APT stop tone).
     low_corr_lines: u32,
-    /// `true` once the current reception has been confirmed to contain real
-    /// image content. Set immediately for phasing-driven entries (the APT
-    /// start tone + phasing pulses already proved the signal); set later
-    /// by the correlation verifier for variance-driven auto-starts.
-    verified: bool,
-    /// Rolling count of consecutive well-correlated lines, used to confirm
-    /// an unverified reception.
-    high_corr_streak: u32,
     /// Number of luminance samples processed while in `State::Phasing`.
     /// When this exceeds the equivalent of `PHASING_TIMEOUT_LINES` lines,
-    /// the decoder falls through to Receiving (unverified) so a noisy or
-    /// partial phasing signal doesn't wedge the state machine.
+    /// the decoder falls through to Receiving so a noisy or partial
+    /// phasing signal doesn't wedge the state machine.
     phasing_samples: u64,
     /// Current rig dial frequency in Hz (for image filenames).
     freq_hz: u64,
@@ -157,8 +134,6 @@ impl WefaxDecoder {
             signal_detect_count: 0,
             signal_detect_buf: Vec::with_capacity(INTERNAL_RATE as usize / 2),
             low_corr_lines: 0,
-            verified: false,
-            high_corr_streak: 0,
             phasing_samples: 0,
             freq_hz: 0,
             mode: String::new(),
@@ -267,7 +242,7 @@ impl WefaxDecoder {
                                     .as_millis() as i64,
                             );
                             self.signal_detect_buf.clear();
-                            events.push(self.transition_to_receiving(ioc, lpm, 0, false));
+                            events.push(self.transition_to_receiving(ioc, lpm, 0));
                             break;
                         }
 
@@ -297,12 +272,12 @@ impl WefaxDecoder {
 
                 if let Some(ref mut phasing) = self.phasing {
                     if let Some(offset) = phasing.process(&luminance) {
-                        events.push(self.transition_to_receiving(ioc, lpm, offset, true));
+                        events.push(self.transition_to_receiving(ioc, lpm, offset));
                     } else {
                         // Phasing timeout: if alignment doesn't converge in
                         // ~PHASING_TIMEOUT_LINES lines, fall through to
-                        // Receiving (unverified) and let the correlation
-                        // verifier decide.
+                        // Receiving and let the carrier-loss watchdog decide
+                        // whether the content that follows is real imagery.
                         self.phasing_samples += luminance.len() as u64;
                         let spl = WefaxConfig::samples_per_line(lpm, INTERNAL_RATE) as u64;
                         if self.phasing_samples >= spl * PHASING_TIMEOUT_LINES as u64 {
@@ -310,7 +285,7 @@ impl WefaxDecoder {
                                 ioc,
                                 lpm, "WEFAX: phasing timeout — falling through to receiving"
                             );
-                            events.push(self.transition_to_receiving(ioc, lpm, 0, false));
+                            events.push(self.transition_to_receiving(ioc, lpm, 0));
                         }
                     }
                 }
@@ -327,66 +302,36 @@ impl WefaxDecoder {
 
                 // Feed luminance to line slicer.
                 let mut carrier_lost = false;
-                let mut verify_failed = false;
                 if let Some(ref mut slicer) = self.slicer {
                     let new_lines = slicer.process(&luminance);
                     for line in new_lines {
                         if let Some(ref mut image) = self.image {
-                            // Line-to-line Pearson correlation classifies the
-                            // new line as image-like, noise-like, or flat.
-                            // fldigi-style: real imagery has highly correlated
-                            // adjacent lines; pure noise does not.
+                            // Carrier-loss watchdog: real imagery has highly
+                            // correlated adjacent lines; pure noise does not.
+                            // After LINE_CORR_NOISE_LINES consecutive low-
+                            // correlation lines we finalize (fldigi-style
+                            // automatic stop).
                             if let Some(r) = image.correlation_with_last(&line) {
-                                if r >= LINE_CORR_IMAGE_THRESHOLD {
-                                    self.high_corr_streak += 1;
-                                    self.low_corr_lines = 0;
-                                    if !self.verified
-                                        && self.high_corr_streak >= VERIFY_HIGH_CORR_STREAK
-                                    {
-                                        self.verified = true;
-                                        debug!(
-                                            lines = image.line_count(),
-                                            "WEFAX: reception verified from line correlation"
-                                        );
-                                    }
-                                } else if r < LINE_CORR_NOISE_THRESHOLD {
+                                if r < LINE_CORR_NOISE_THRESHOLD {
                                     self.low_corr_lines += 1;
-                                    self.high_corr_streak = 0;
                                     trace!(
                                         r = format!("{:.3}", r),
                                         count = self.low_corr_lines,
                                         "WEFAX low line-correlation"
                                     );
                                 } else {
-                                    // Middle zone — reset high streak, hold
-                                    // low-corr counter.
-                                    self.high_corr_streak = 0;
+                                    self.low_corr_lines = 0;
                                 }
                             }
                             // Flat lines (correlation == None) don't advance
-                            // either counter — solid bands in real imagery
-                            // shouldn't be scored as noise OR as evidence.
+                            // the counter but also don't reset it — an image
+                            // with a solid band surrounded by noise still
+                            // trips the watchdog once the noise resumes.
 
                             image.push_line(line);
                             let count = image.line_count();
 
-                            // Unverified timeout: if we got here from a
-                            // variance auto-start and line correlation never
-                            // took hold, the "signal" wasn't real WEFAX.
-                            // Abandon without saving.
-                            if !self.verified && count >= VERIFY_TIMEOUT_LINES {
-                                debug!(
-                                    lines = count,
-                                    "WEFAX: failed to verify image content — abandoning"
-                                );
-                                verify_failed = true;
-                                break;
-                            }
-
-                            // Carrier-loss watchdog — only active once the
-                            // reception has been verified (otherwise it
-                            // double-counts with the verify timeout).
-                            if self.verified && self.low_corr_lines >= LINE_CORR_NOISE_LINES {
+                            if self.low_corr_lines >= LINE_CORR_NOISE_LINES {
                                 debug!(
                                     lines = count,
                                     "WEFAX: line correlation lost — auto-finalizing image"
@@ -418,15 +363,6 @@ impl WefaxDecoder {
                     }
                 }
 
-                if verify_failed {
-                    // Drop buffered content without saving — this was a
-                    // false auto-start (tone, noise burst, etc.).
-                    self.image = None;
-                    self.reception_start_ms = None;
-                    self.transition_to_idle();
-                    return events;
-                }
-
                 if carrier_lost {
                     events.extend(self.finalize_image(ioc, lpm));
                     self.transition_to_idle();
@@ -465,8 +401,6 @@ impl WefaxDecoder {
         self.signal_detect_count = 0;
         self.signal_detect_buf.clear();
         self.low_corr_lines = 0;
-        self.verified = false;
-        self.high_corr_streak = 0;
         self.phasing_samples = 0;
         events
     }
@@ -522,30 +456,13 @@ impl WefaxDecoder {
         self.state_event("Phasing", ioc, lpm)
     }
 
-    fn transition_to_receiving(
-        &mut self,
-        ioc: u16,
-        lpm: u16,
-        phase_offset: usize,
-        verified: bool,
-    ) -> WefaxEvent {
-        debug!(
-            ioc,
-            lpm, phase_offset, verified, "WEFAX: entering receiving"
-        );
+    fn transition_to_receiving(&mut self, ioc: u16, lpm: u16, phase_offset: usize) -> WefaxEvent {
+        debug!(ioc, lpm, phase_offset, "WEFAX: entering receiving");
         let ppl = WefaxConfig::pixels_per_line(ioc) as usize;
-        self.slicer = Some(LineSlicer::with_slant(
-            lpm,
-            ioc,
-            INTERNAL_RATE,
-            phase_offset,
-            self.config.slant_correction,
-        ));
+        self.slicer = Some(LineSlicer::new(lpm, ioc, INTERNAL_RATE, phase_offset));
         self.image = Some(ImageAssembler::new(ppl));
         self.tone_detector.reset();
         self.low_corr_lines = 0;
-        self.verified = verified;
-        self.high_corr_streak = 0;
         self.state = State::Receiving { ioc, lpm };
         self.state_event("Receiving", ioc, lpm)
     }
@@ -559,8 +476,6 @@ impl WefaxDecoder {
         self.signal_detect_count = 0;
         self.signal_detect_buf.clear();
         self.low_corr_lines = 0;
-        self.verified = false;
-        self.high_corr_streak = 0;
         self.phasing_samples = 0;
     }
 
@@ -574,12 +489,23 @@ impl WefaxDecoder {
 
             let ppl = WefaxConfig::pixels_per_line(ioc);
             let mut path_str = None;
+            let mut png_data = None;
 
             // Save PNG if output directory is configured.
             if let Some(ref dir) = self.config.output_dir {
                 let output_path = PathBuf::from(dir);
                 match image.save_png(&output_path, self.freq_hz, &self.mode) {
                     Ok(p) => {
+                        // Read back the PNG bytes for remote client transfer.
+                        match std::fs::read(&p) {
+                            Ok(bytes) => {
+                                png_data =
+                                    Some(base64::engine::general_purpose::STANDARD.encode(&bytes));
+                            }
+                            Err(e) => {
+                                eprintln!("WEFAX: failed to read PNG for transfer: {}", e);
+                            }
+                        }
                         path_str = Some(p.to_string_lossy().into_owned());
                     }
                     Err(e) => {
@@ -597,6 +523,7 @@ impl WefaxDecoder {
                 ioc,
                 pixels_per_line: ppl,
                 path: path_str,
+                png_data,
                 complete: true,
             }));
         }

src/decoders/trx-wefax/src/line_slicer.rs

@@ -7,21 +7,9 @@
 //! Once the phasing detector has established a line-start phase offset,
 //! the line slicer accumulates demodulated luminance samples and extracts
 //! complete image lines at the configured LPM rate.
-//!
-//! When `slant_correction` is enabled, the slicer tracks line-to-line
-//! drift via cross-correlation with the previous line and nudges the
-//! extraction cursor by ±`MAX_DRIFT_SAMPLES` per line. This compensates
-//! for the small mismatch between the transmitter's and receiver's
-//! sample clocks that would otherwise skew the assembled image.
 
 use crate::config::WefaxConfig;
 
-/// Maximum per-line drift (in samples at the internal rate) searched for
-/// when slant correction is enabled. At 120 LPM / 11025 Hz there are
-/// ~5512 samples per line, so ±6 samples is ~0.1% drift per line — more
-/// than enough for any real-world sample-clock mismatch.
-const MAX_DRIFT_SAMPLES: usize = 6;
-
 /// Line slicer for WEFAX image assembly.
 pub struct LineSlicer {
     /// Samples per line at the internal sample rate.
@@ -30,34 +18,14 @@ pub struct LineSlicer {
     pixels_per_line: usize,
     /// Phase offset in samples from the phasing detector.
     phase_offset: usize,
-    /// Accumulated luminance samples. While `slant_correction` is on,
-    /// the buffer anchor is the *start of the previous line* (so the
-    /// first `samples_per_line` samples are the reference for drift
-    /// tracking). Without slant correction the anchor is simply the
-    /// start of the next line to extract.
+    /// Accumulated luminance samples.
     buffer: Vec<f32>,
     /// Whether we have aligned to the phase offset yet.
     aligned: bool,
-    /// Whether a reference (previous) line is held at the buffer anchor.
-    has_reference: bool,
-    /// Enable line-to-line drift tracking.
-    slant_correction: bool,
-    /// Cumulative drift applied so far (samples). Diagnostic.
-    pub(crate) total_drift: i64,
 }
 
 impl LineSlicer {
     pub fn new(lpm: u16, ioc: u16, sample_rate: u32, phase_offset: usize) -> Self {
-        Self::with_slant(lpm, ioc, sample_rate, phase_offset, true)
-    }
-
-    pub fn with_slant(
-        lpm: u16,
-        ioc: u16,
-        sample_rate: u32,
-        phase_offset: usize,
-        slant_correction: bool,
-    ) -> Self {
         let samples_per_line = WefaxConfig::samples_per_line(lpm, sample_rate);
         let pixels_per_line = WefaxConfig::pixels_per_line(ioc) as usize;
 
@@ -65,11 +33,8 @@ impl LineSlicer {
             samples_per_line,
             pixels_per_line,
             phase_offset,
-            buffer: Vec::with_capacity(samples_per_line * 3),
+            buffer: Vec::with_capacity(samples_per_line * 2),
             aligned: false,
-            has_reference: false,
-            slant_correction,
-            total_drift: 0,
         }
     }
 
@@ -90,56 +55,16 @@ impl LineSlicer {
             self.aligned = true;
         }
 
-        let spl = self.samples_per_line;
-
-        if !self.slant_correction {
-            // Simple fixed-period extraction.
-            let mut offset = 0;
-            while offset + spl <= self.buffer.len() {
-                let line_samples = &self.buffer[offset..offset + spl];
-                let pixels = self.resample_line(line_samples);
-                lines.push(pixels);
-                offset += spl;
-            }
-            if offset > 0 {
-                self.buffer.drain(..offset);
-            }
-            return lines;
-        }
-
-        // Slant-corrected extraction.
-        let max_shift = MAX_DRIFT_SAMPLES;
-
-        // Bootstrap: the very first line has no previous reference.
-        // Extract it naively and keep it in the buffer as the reference.
-        if !self.has_reference {
-            if self.buffer.len() < spl {
-                return lines;
-            }
-            let first = self.buffer[0..spl].to_vec();
-            let pixels = self.resample_line(&first);
+        // Extract complete lines (single drain at the end to avoid O(n²)).
+        let mut offset = 0;
+        while offset + self.samples_per_line <= self.buffer.len() {
+            let line_samples = &self.buffer[offset..offset + self.samples_per_line];
+            let pixels = self.resample_line(line_samples);
             lines.push(pixels);
-            self.has_reference = true;
-            // Do NOT drain: the first `spl` samples remain as the
-            // reference for the next line's drift search.
+            offset += self.samples_per_line;
         }
-
-        // Subsequent lines: for each iteration, buffer[0..spl] is the
-        // reference line, and we search for the best starting position
-        // of the NEXT line in the range [spl - max_shift, spl + max_shift].
-        while self.buffer.len() >= 2 * spl + max_shift {
-            let prev = &self.buffer[0..spl];
-            let (best_d, _best_r) = search_best_shift(prev, &self.buffer, spl, max_shift);
-
-            let start = (spl as i32 + best_d) as usize;
-            let next_line = self.buffer[start..start + spl].to_vec();
-            let pixels = self.resample_line(&next_line);
-            lines.push(pixels);
-
-            // Advance the anchor to the start of the line we just
-            // emitted — it becomes the reference for the next iteration.
-            self.buffer.drain(..start);
-            self.total_drift += best_d as i64;
+        if offset > 0 {
+            self.buffer.drain(..offset);
         }
 
         lines
@@ -149,16 +74,9 @@ impl LineSlicer {
         self.pixels_per_line
     }
 
-    /// Samples per line at the internal rate (for diagnostics).
-    pub fn samples_per_line(&self) -> usize {
-        self.samples_per_line
-    }
-
     pub fn reset(&mut self) {
         self.buffer.clear();
         self.aligned = false;
-        self.has_reference = false;
-        self.total_drift = 0;
     }
 
     /// Resample a line's worth of luminance samples to the target pixel count
@@ -189,82 +107,6 @@ impl LineSlicer {
     }
 }
 
-/// Search for the drift `d ∈ [-max_shift, +max_shift]` that maximises
-/// the Pearson correlation between `reference` and
-/// `buffer[spl+d .. spl+d+spl]`.
-///
-/// Returns `(best_d, best_r)`. A correlation-peak deadband prefers
-/// `d = 0` when the peak is only marginally better than at zero, which
-/// keeps tracking stable on quiet lines.
-fn search_best_shift(
-    reference: &[f32],
-    buffer: &[f32],
-    spl: usize,
-    max_shift: usize,
-) -> (i32, f32) {
-    debug_assert!(buffer.len() >= 2 * spl + max_shift);
-    debug_assert_eq!(reference.len(), spl);
-
-    // Pre-compute reference mean + variance.
-    let n = spl as f32;
-    let mean_r = reference.iter().sum::<f32>() / n;
-    let mut var_r = 0.0f32;
-    for &v in reference {
-        let d = v - mean_r;
-        var_r += d * d;
-    }
-
-    // Guard against a flat reference line — drift tracking is useless.
-    const MIN_VAR: f32 = 32.0;
-    if var_r < MIN_VAR {
-        return (0, 0.0);
-    }
-
-    let ms = max_shift as i32;
-    let mut best_d = 0i32;
-    let mut best_r = f32::NEG_INFINITY;
-    let mut r_at_zero = 0.0f32;
-
-    for d in -ms..=ms {
-        let start = (spl as i32 + d) as usize;
-        let candidate = &buffer[start..start + spl];
-
-        let mean_c = candidate.iter().sum::<f32>() / n;
-        let mut var_c = 0.0f32;
-        let mut cov = 0.0f32;
-        for (i, &v) in candidate.iter().enumerate() {
-            let dr = reference[i] - mean_r;
-            let dc = v - mean_c;
-            cov += dr * dc;
-            var_c += dc * dc;
-        }
-
-        let r = if var_c < MIN_VAR {
-            // Skip flat candidate slices.
-            f32::NEG_INFINITY
-        } else {
-            cov / (var_r.sqrt() * var_c.sqrt())
-        };
-
-        if d == 0 {
-            r_at_zero = r;
-        }
-        if r > best_r {
-            best_r = r;
-            best_d = d;
-        }
-    }
-
-    // Deadband: if the peak is only marginally better than `d = 0`,
-    // stick with zero. This avoids per-line jitter when drift is small.
-    const DEADBAND: f32 = 0.01;
-    if r_at_zero.is_finite() && best_r - r_at_zero < DEADBAND {
-        return (0, r_at_zero);
-    }
-
-    (best_d, best_r)
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -277,8 +119,7 @@ mod tests {
         let spl = WefaxConfig::samples_per_line(lpm, sr);
         let ppl = WefaxConfig::pixels_per_line(ioc) as usize;
 
-        // Slant correction off for deterministic line count.
-        let mut slicer = LineSlicer::with_slant(lpm, ioc, sr, 0, false);
+        let mut slicer = LineSlicer::new(lpm, ioc, sr, 0);
         // Feed exactly 3 lines worth of white.
         let samples = vec![1.0f32; spl * 3];
         let lines = slicer.process(&samples);
@@ -295,7 +136,7 @@ mod tests {
         let sr = 11025;
         let spl = WefaxConfig::samples_per_line(lpm, sr);
 
-        let mut slicer = LineSlicer::with_slant(lpm, ioc, sr, 0, false);
+        let mut slicer = LineSlicer::new(lpm, ioc, sr, 0);
         // Feed a linear ramp from 0.0 to 1.0.
         let samples: Vec<f32> = (0..spl).map(|i| i as f32 / spl as f32).collect();
         let lines = slicer.process(&samples);
@@ -304,92 +145,4 @@ mod tests {
         assert!(lines[0][0] < 5);
         assert!(lines[0].last().copied().unwrap_or(0) > 250);
     }
-
-    /// Synthesise a noisy-ish gradient line that repeats with a small
-    /// per-line offset, simulating a sample-clock mismatch. The slant
-    /// tracker should follow the drift.
-    #[test]
-    fn slant_tracker_follows_drift() {
-        let lpm = 120;
-        let ioc = 576;
-        let sr = 11025;
-        let spl = WefaxConfig::samples_per_line(lpm, sr);
-
-        // Build a signal where each real line is `spl + 3` samples long
-        // (i.e. transmitter clock is slower than expected → positive drift
-        // of +3 samples per line). The content needs high-frequency
-        // structure for a few-sample shift to be detectable against the
-        // deadband.
-        let true_line_len = spl + 3;
-        let mut signal: Vec<f32> = Vec::new();
-        let base: Vec<f32> = (0..true_line_len)
-            .map(|i| {
-                // Pseudo-random-but-repeatable content with a narrow
-                // bright stripe — sharp features make sub-line shifts
-                // easy to localise.
-                let x = ((i as u32).wrapping_mul(2654435761)) >> 16;
-                let noise = (x & 0xff) as f32 / 255.0;
-                let stripe = if i == true_line_len / 3 { 1.0 } else { 0.0 };
-                0.3 + 0.4 * noise + stripe
-            })
-            .collect();
-        // 20 lines, each identical.
-        for _ in 0..20 {
-            signal.extend_from_slice(&base);
-        }
-
-        let mut slicer = LineSlicer::with_slant(lpm, ioc, sr, 0, true);
-        let lines = slicer.process(&signal);
-
-        // Expect ~ (20*true_line_len - spl) / (spl+drift) lines with
-        // drift absorbing the extra 2 samples per line.
-        assert!(
-            lines.len() >= 15,
-            "slant-corrected slicer produced only {} lines",
-            lines.len()
-        );
-        // Should have tracked positive drift.
-        assert!(
-            slicer.total_drift > 0,
-            "expected positive drift, got {}",
-            slicer.total_drift
-        );
-        // Roughly +3 per line (after the first bootstrap line); allow wide tolerance.
-        let per_line = slicer.total_drift as f32 / (lines.len() - 1) as f32;
-        assert!(
-            per_line > 1.5 && per_line < 4.0,
-            "per-line drift {:.2} out of range (total {}, lines {})",
-            per_line,
-            slicer.total_drift,
-            lines.len()
-        );
-    }
-
-    #[test]
-    fn slant_tracker_deadband_on_no_drift() {
-        let lpm = 120;
-        let ioc = 576;
-        let sr = 11025;
-        let spl = WefaxConfig::samples_per_line(lpm, sr);
-
-        // Perfectly aligned lines → drift should stay at zero.
-        let line: Vec<f32> = (0..spl)
-            .map(|i| {
-                let t = i as f32 / spl as f32;
-                0.5 + 0.4 * (t * 9.0 * std::f32::consts::PI).sin()
-            })
-            .collect();
-        let mut signal = Vec::new();
-        for _ in 0..10 {
-            signal.extend_from_slice(&line);
-        }
-
-        let mut slicer = LineSlicer::with_slant(lpm, ioc, sr, 0, true);
-        let _ = slicer.process(&signal);
-        // Deadband should keep drift at 0.
-        assert_eq!(
-            slicer.total_drift, 0,
-            "no drift expected for identical lines"
-        );
-    }
 }

src/trx-client/trx-frontend/trx-frontend-http/Cargo.toml

@@ -16,6 +16,7 @@ tokio = { workspace = true, features = ["full"] }
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
 tracing = { workspace = true }
+base64 = "0.22"
 actix-web = "4.4"
 actix-ws = "0.3"
 tokio-stream = { version = "0.1", features = ["sync"] }

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

@@ -4485,7 +4485,16 @@ function _initMapWhenReady() {
     if (loadingEl) loadingEl.classList.add("is-hidden");
     window.trx.map.initAprsMap();
     window.trx.map.sizeAprsMapToViewport();
-    if (window.trx.map.aprsMap) setTimeout(() => window.trx.map.aprsMap.invalidateSize(), 50);
+    // The map panel was just made visible (display:none → ""); the browser
+    // may not have laid it out yet, so getBoundingClientRect() can return
+    // stale/zero dimensions.  Double-rAF ensures a full layout pass has
+    // completed before we re-measure and tell Leaflet about its real size.
+    requestAnimationFrame(() => {
+      requestAnimationFrame(() => {
+        window.trx.map.sizeAprsMapToViewport();
+        if (window.trx.map.aprsMap) window.trx.map.aprsMap.invalidateSize();
+      });
+    });
     return;
   }
   // Not ready yet — show overlay and poll until both are available.
@@ -7006,9 +7015,18 @@ function stopSpectrumStreaming() {
 
 // ── /meter (fast signal-strength) streaming ─────────────────────────────────
 // Dedicated SSE channel pushed at ~30 Hz by trx-server; bypasses /events so
-// meter frames are never gated by full-RigState diffing. Synchronous DOM
-// write per frame — no rAF coalescing, per user requirement that it "feel
-// instant" on the frontend.
+// meter frames are never gated by full-RigState diffing.
+//
+// Client-side asymmetric EMA smoothing (GQRX-style ballistics):
+//   attack τ ≈ 400 ms  — rises in ~12 frames at 30 Hz
+//   decay  τ ≈ 1.0 s   — falls in ~30 frames, readable
+// DOM updates are coalesced via requestAnimationFrame so the bar
+// animates at display refresh rate, not SSE rate.
+const METER_ATTACK_ALPHA = 0.08; // per-frame at ~30 Hz ≈ 400 ms τ
+const METER_DECAY_ALPHA  = 0.03; // per-frame at ~30 Hz ≈ 1.0 s τ
+let meterSmoothedDbm = null;
+let meterRafPending = false;
+
 function scheduleMeterReconnect() {
   if (meterReconnectTimer !== null) return;
   meterReconnectTimer = setTimeout(() => {
@@ -7019,6 +7037,24 @@ function scheduleMeterReconnect() {
 
 function applyMeterSample(dbm) {
   if (typeof dbm !== "number" || !Number.isFinite(dbm)) return;
+  // Asymmetric EMA: fast attack, slow decay.
+  if (meterSmoothedDbm === null) {
+    meterSmoothedDbm = dbm;
+  } else {
+    const alpha = dbm > meterSmoothedDbm ? METER_ATTACK_ALPHA : METER_DECAY_ALPHA;
+    meterSmoothedDbm += alpha * (dbm - meterSmoothedDbm);
+  }
+  // Coalesce DOM writes to display refresh rate.
+  if (!meterRafPending) {
+    meterRafPending = true;
+    requestAnimationFrame(flushMeterDom);
+  }
+}
+
+function flushMeterDom() {
+  meterRafPending = false;
+  const dbm = meterSmoothedDbm;
+  if (dbm === null) return;
   prevRenderData.sigDbm = dbm;
   const sUnits = dbmToSUnits(dbm);
   sigLastSUnits = sUnits;
@@ -7059,6 +7095,7 @@ function stopMeterStreaming() {
     clearTimeout(meterReconnectTimer);
     meterReconnectTimer = null;
   }
+  meterSmoothedDbm = null; // reset so next rig starts fresh
 }
 
 // ── Rendering ────────────────────────────────────────────────────────────────

src/trx-client/trx-frontend/trx-frontend-http/assets/web/map-core.js

@@ -1848,10 +1848,13 @@
     initAprsMap();
     sizeAprsMapToViewport();
     if (aprsMap) {
-      setTimeout(() => {
-        aprsMap.invalidateSize();
-        aprsMap.setView([lat, lon], 13);
-      }, 50);
+      requestAnimationFrame(() => {
+        requestAnimationFrame(() => {
+          sizeAprsMapToViewport();
+          aprsMap.invalidateSize();
+          aprsMap.setView([lat, lon], 13);
+        });
+      });
     }
   };
 
@@ -1896,6 +1899,7 @@
     const center = locatorMarkerCenter(marker);
     const focusMarker = () => {
       if (!aprsMap || !marker) return;
+      sizeAprsMapToViewport();
       aprsMap.invalidateSize();
       if (center) {
         const targetZoom = Math.max(aprsMap.getZoom() || 0, 7);
@@ -1910,7 +1914,9 @@
       if (typeof marker.openPopup === "function") marker.openPopup();
     };
     focusMarker();
-    setTimeout(focusMarker, 60);
+    requestAnimationFrame(() => {
+      requestAnimationFrame(focusMarker);
+    });
     return true;
   };
 

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

@@ -1356,7 +1356,7 @@ small { color: var(--text-muted); }
 .band-tag { display: inline-block; padding: 2px 6px; border-radius: 6px; background: var(--btn-bg); color: var(--text); font-size: 0.82rem; border: 1px solid var(--border-light); margin-left: 6px; }
 .signal { display: flex; gap: 0.6rem; align-items: center; }
 .signal-bar { flex: 1 1 auto; height: 12px; border-radius: 999px; background: var(--btn-bg); border: 1px solid var(--border-light); overflow: hidden; }
-.signal-bar-fill { height: 100%; width: 0%; background: linear-gradient(90deg, var(--accent-green), var(--accent-yellow), var(--accent-red)); transition: width 150ms ease; }
+.signal-bar-fill { height: 100%; width: 0%; background: linear-gradient(90deg, var(--accent-green), var(--accent-yellow), var(--accent-red)); transition: width 300ms ease-out; }
 .signal-value { font-size: 0.95rem; color: var(--text-heading); min-width: 48px; text-align: right; }
 .meter { display: flex; gap: 0.6rem; align-items: center; }
 .meter-bar { flex: 1 1 auto; height: 12px; border-radius: 999px; background: var(--btn-bg); border: 1px solid var(--border-light); overflow: hidden; }

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

@@ -16,6 +16,7 @@ use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 
 use actix_web::{get, web, Error, HttpRequest, HttpResponse};
 use actix_ws::Message;
+use base64::Engine as _;
 use bytes::Bytes;
 use serde::Deserialize;
 use tokio::sync::broadcast;
@@ -297,7 +298,30 @@ fn record_wspr(context: &FrontendRuntimeContext, msg: WsprMessage) {
     prune_wspr_history(context, &mut history);
 }
 
-fn record_wefax(context: &FrontendRuntimeContext, msg: WefaxMessage) {
+fn record_wefax(context: &FrontendRuntimeContext, mut msg: WefaxMessage) {
+    // If the server sent PNG data, save it to the local cache so the
+    // `/images/` endpoint can serve it.
+    if let Some(ref data) = msg.png_data {
+        if let Some(ref path) = msg.path {
+            if let Some(filename) = std::path::Path::new(path).file_name() {
+                let dir = dirs::cache_dir()
+                    .unwrap_or_else(|| std::path::PathBuf::from(".cache"))
+                    .join("trx-rs")
+                    .join("wefax");
+                if std::fs::create_dir_all(&dir).is_ok() {
+                    if let Ok(bytes) = base64::engine::general_purpose::STANDARD.decode(data) {
+                        let local_path = dir.join(filename);
+                        if let Err(e) = std::fs::write(&local_path, &bytes) {
+                            tracing::warn!("WEFAX: failed to save local image: {}", e);
+                        }
+                    }
+                }
+            }
+        }
+    }
+    // Strip bulk data before storing in memory.
+    msg.png_data = None;
+
     let rig_id = msg.rig_id.clone().or_else(|| active_rig_id(context));
     let mut history = context
         .decode_history

src/trx-core/src/decode.rs

@@ -291,6 +291,10 @@ pub struct WefaxMessage {
     /// Filesystem path to saved PNG (set on completion).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub path: Option<String>,
+    /// Base64-encoded PNG data for transfer to remote clients.
+    /// Populated by the server when sending, stripped before storing in history.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub png_data: Option<String>,
     /// True when image is complete (stop tone received).
     pub complete: bool,
 }

src/trx-server/Cargo.toml

@@ -14,6 +14,7 @@ ft2 = ["trx-ftx/ft2", "trx-protocol/ft2"]
 soapysdr = ["trx-backend/soapysdr"]
 
 [dependencies]
+base64 = "0.22"
 flate2 = { workspace = true }
 tokio = { workspace = true, features = ["full"] }
 tokio-serial = { workspace = true }

src/trx-server/src/audio.rs

@@ -12,6 +12,7 @@ use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
 
+use base64::Engine as _;
 use bytes::Bytes;
 use flate2::write::GzEncoder;
 use flate2::Compression;
@@ -709,6 +710,8 @@ impl DecoderHistories {
         if msg.ts_ms.is_none() {
             msg.ts_ms = Some(current_timestamp_ms());
         }
+        // Strip bulk PNG data before storing in memory/persistence.
+        msg.png_data = None;
         let mut h = lock_or_recover(&self.wefax, "wefax_history");
         let before = h.len();
         h.push_back((Instant::now(), msg));
@@ -722,7 +725,21 @@ impl DecoderHistories {
         let before = h.len();
         Self::prune_wefax(&mut h);
         self.adjust_total_count(before, h.len());
-        h.iter().map(|(_, msg)| msg.clone()).collect()
+        h.iter()
+            .map(|(_, msg)| {
+                let mut m = msg.clone();
+                // Re-read PNG from disk so remote clients can save a local copy.
+                if m.png_data.is_none() {
+                    if let Some(ref path) = m.path {
+                        if let Ok(bytes) = std::fs::read(path) {
+                            m.png_data =
+                                Some(base64::engine::general_purpose::STANDARD.encode(&bytes));
+                        }
+                    }
+                }
+                m
+            })
+            .collect()
     }
 
     pub fn clear_wefax_history(&self) {

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

@@ -308,20 +308,22 @@ pub struct ChannelDsp {
 impl ChannelDsp {
     /// Compute asymmetric IIR coefficients for S-meter envelope tracking.
     ///
-    /// Attack: ~50 ms time constant (responsive but visually stable).
-    /// Decay:  ~300 ms time constant (slow fall for stable reading).
+    /// Attack: ~400 ms — rises over ~12 frames at 30 Hz.
+    /// Decay:  ~1.0 s  — falls over ~30 frames, readable.
     ///
-    /// Note: these alphas are applied once per decimated *block*, not per
-    /// sample, with block-rate correction (`1 − (1−α)^N`).  The 50 ms
-    /// attack gives ~3-frame settling at 30 Hz meter refresh — fast
-    /// enough to follow signal changes, smooth enough to avoid jitter.
+    /// Modelled after GQRX meter ballistics.  Deliberately slower than
+    /// the IARU analog-meter spec because a digital bar at 30 fps is
+    /// visually noisier than a physical needle with mechanical inertia.
+    ///
+    /// Note: alphas are applied once per decimated *block*, not per
+    /// sample, with block-rate correction (`1 − (1−α)^N`).
     fn smeter_alphas(channel_sample_rate: u32) -> (f32, f32) {
         if channel_sample_rate == 0 {
             return (0.3, 0.01);
         }
         let sr = channel_sample_rate as f32;
-        let attack = (1.0 - (-1.0 / (sr * 0.050)).exp()).min(1.0); // τ = 50 ms
-        let decay = (1.0 - (-1.0 / (sr * 0.300)).exp()).min(1.0); // τ = 300 ms
+        let attack = (1.0 - (-1.0 / (sr * 0.400)).exp()).min(1.0); // τ = 400 ms
+        let decay = (1.0 - (-1.0 / (sr * 1.000)).exp()).min(1.0); // τ = 1.0 s
         (attack, decay)
     }