sjg/trx-rs
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

[fix](trx-wefax): fallback phasing detection for mid-transmission tune-in

Browse Source 
When tuning into a WEFAX station after the APT start tone has already
passed, the decoder stayed in Idle forever. Add an idle_phasing detector
that continuously runs phasing detection on demodulated luminance while
in Idle state, allowing the decoder to lock onto ongoing transmissions
without requiring the 300/675 Hz start tone.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>
This commit is contained in:
Stan Grams
2026-04-03 22:30:43 +02:00
parent ce5b55386c
commit 0a8e004a62
1 changed files with 34 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/decoders/trx-wefax/src/decoder.rs
+34 -1
View File
@@ -55,6 +55,9 @@ pub struct WefaxDecoder {
demodulator: FmDiscriminator,
tone_detector: ToneDetector,
phasing: Option<PhasingDetector>,
/// Fallback phasing detector that runs in Idle state to catch ongoing
/// transmissions when the APT start tone was missed.
idle_phasing: Option<PhasingDetector>,
slicer: Option<LineSlicer>,
image: Option<ImageAssembler>,
/// Total sample counter for timestamps.
@@ -65,6 +68,7 @@ pub struct WefaxDecoder {
impl WefaxDecoder {
pub fn new(input_sample_rate: u32, config: WefaxConfig) -> Self {
let default_lpm = config.lpm.unwrap_or(120);
Self {
resampler: Resampler::new(input_sample_rate),
demodulator: FmDiscriminator::new(
@@ -73,6 +77,7 @@ impl WefaxDecoder {
config.deviation_hz,
),
tone_detector: ToneDetector::new(INTERNAL_RATE),
idle_phasing: Some(PhasingDetector::new(default_lpm, INTERNAL_RATE)),
config,
state: State::Idle,
phasing: None,
@@ -102,22 +107,46 @@ impl WefaxDecoder {
// Step 4: Process based on current state.
match self.state.clone() {
State::Idle => {
// Look for start tone.
// Look for APT start tone first.
let mut got_start = false;
for result in &tone_results {
if let Some(tone) = result.tone {
match tone {
AptTone::Start576 => {
self.idle_phasing = None;
self.transition_to_start_detected(576);
got_start = true;
break;
}
AptTone::Start288 => {
self.idle_phasing = None;
self.transition_to_start_detected(288);
got_start = true;
break;
}
AptTone::Stop => {} // Ignore stop in idle.
}
}
}
// Fallback: try phasing detection on luminance to catch
// ongoing transmissions where the start tone was missed.
if !got_start {
if let Some(ref mut idle_ph) = self.idle_phasing {
if let Some(offset) = idle_ph.process(&luminance) {
let ioc = self.config.ioc.unwrap_or(576);
let lpm = self.config.lpm.unwrap_or(120);
self.reception_start_ms = Some(
std::time::SystemTime::now()
.duration_since(std::time::UNIX_EPOCH)
.unwrap_or_default()
.as_millis() as i64,
);
self.idle_phasing = None;
self.transition_to_receiving(ioc, lpm, offset);
}
}
}
}
State::StartDetected { ioc } => {
@@ -205,11 +234,13 @@ impl WefaxDecoder {
/// Reset the decoder, discarding any in-progress image.
pub fn reset(&mut self) {
let default_lpm = self.config.lpm.unwrap_or(120);
self.state = State::Idle;
self.resampler.reset();
self.demodulator.reset();
self.tone_detector.reset();
self.phasing = None;
self.idle_phasing = Some(PhasingDetector::new(default_lpm, INTERNAL_RATE));
self.slicer = None;
self.image = None;
self.sample_count = 0;
@@ -252,11 +283,13 @@ impl WefaxDecoder {
}
fn transition_to_idle(&mut self) {
let default_lpm = self.config.lpm.unwrap_or(120);
self.state = State::Idle;
self.phasing = None;
self.slicer = None;
// image is kept until finalize_image is called or next reception starts.
self.tone_detector.reset();
self.idle_phasing = Some(PhasingDetector::new(default_lpm, INTERNAL_RATE));
}
fn finalize_image(&mut self, ioc: u16, lpm: u16) -> Vec<WefaxEvent> {