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[feat](trx-rds): add early-late timing correction

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Co-authored-by: Codex <codex@openai.com>
Signed-off-by: Stan Grams <sjg@haxx.space>
This commit is contained in:
Stan Grams
2026-02-28 12:32:23 +01:00
parent 017b7be8a8
commit a94fcd75af
1 changed files with 32 additions and 0 deletions
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src/decoders/trx-rds/src/lib.rs
+32
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@@ -15,6 +15,9 @@ const PHASE_CANDIDATES: usize = 8;
const BIPHASE_CLOCK_WINDOW: usize = 128;
const RDS_BASEBAND_LP_HZ: f32 = 2_400.0;
const PS_VOTE_COMMIT_SCORE: u8 = 3;
const TIMING_PHASE_GAIN: f32 = 0.08;
const TIMING_RATE_GAIN: f32 = 0.0008;
const TIMING_RATE_SPAN: f32 = 0.03;
const OFFSET_A: u16 = 0x0FC;
const OFFSET_B: u16 = 0x198;
@@ -63,10 +66,15 @@ enum ExpectBlock {
#[derive(Debug, Clone)]
struct Candidate {
clock_phase: f32,
nominal_clock_inc: f32,
clock_inc: f32,
sym_i_acc: f32,
sym_q_acc: f32,
sym_count: u16,
early_energy_acc: f32,
early_energy_count: u16,
late_energy_acc: f32,
late_energy_count: u16,
prev_psk_symbol: Option<(f32, f32)>,
clock_history: [f32; BIPHASE_CLOCK_WINDOW],
clock: usize,
@@ -94,10 +102,15 @@ impl Candidate {
fn new(sample_rate: f32, phase_offset: f32) -> Self {
Self {
clock_phase: phase_offset,
nominal_clock_inc: RDS_PSK_SYMBOL_RATE / sample_rate.max(1.0),
clock_inc: RDS_PSK_SYMBOL_RATE / sample_rate.max(1.0),
sym_i_acc: 0.0,
sym_q_acc: 0.0,
sym_count: 0,
early_energy_acc: 0.0,
early_energy_count: 0,
late_energy_acc: 0.0,
late_energy_count: 0,
prev_psk_symbol: None,
clock_history: [0.0; BIPHASE_CLOCK_WINDOW],
clock: 0,
@@ -126,6 +139,14 @@ impl Candidate {
self.sym_i_acc += i;
self.sym_q_acc += q;
self.sym_count = self.sym_count.saturating_add(1);
let energy = (i * i + q * q).sqrt();
if self.clock_phase < 0.5 {
self.early_energy_acc += energy;
self.early_energy_count = self.early_energy_count.saturating_add(1);
} else {
self.late_energy_acc += energy;
self.late_energy_count = self.late_energy_count.saturating_add(1);
}
self.clock_phase += self.clock_inc;
if self.clock_phase < 1.0 {
return None;
@@ -137,6 +158,17 @@ impl Candidate {
self.sym_i_acc = 0.0;
self.sym_q_acc = 0.0;
self.sym_count = 0;
let early_avg = self.early_energy_acc / f32::from(self.early_energy_count.max(1));
let late_avg = self.late_energy_acc / f32::from(self.late_energy_count.max(1));
self.early_energy_acc = 0.0;
self.early_energy_count = 0;
self.late_energy_acc = 0.0;
self.late_energy_count = 0;
let timing_err = (late_avg - early_avg) / (late_avg + early_avg + 1e-6);
self.clock_phase = (self.clock_phase - timing_err * TIMING_PHASE_GAIN).clamp(0.0, 0.999);
let min_inc = self.nominal_clock_inc * (1.0 - TIMING_RATE_SPAN);
let max_inc = self.nominal_clock_inc * (1.0 + TIMING_RATE_SPAN);
self.clock_inc = (self.clock_inc - timing_err * TIMING_RATE_GAIN).clamp(min_inc, max_inc);
let update = if let Some((prev_i, prev_q)) = self.prev_psk_symbol {
let biphase_i = (symbol.0 - prev_i) * 0.5;