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[fix](trx-server): gate near-silent audio before decode

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Apply an RMS gate to near-silent decoder input frames and zero them
before APRS/CW/FT8/WSPR processing to avoid false decodes from
unsquelched/no-signal noise.

Co-authored-by: Codex <codex@openai.com>
Signed-off-by: Stan Grams <sjg@haxx.space>
This commit is contained in:
Stan Grams
2026-03-04 22:58:02 +01:00
parent 239857d536
commit 878b50cad7
1 changed files with 30 additions and 4 deletions
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src/trx-server/src/audio.rs
+30 -4
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@@ -41,6 +41,7 @@ const VDES_HISTORY_RETENTION: Duration = Duration::from_secs(24 * 60 * 60);
const FT8_HISTORY_RETENTION: Duration = Duration::from_secs(24 * 60 * 60);
const WSPR_HISTORY_RETENTION: Duration = Duration::from_secs(24 * 60 * 60);
const FT8_SAMPLE_RATE: u32 = 12_000;
const DECODE_AUDIO_GATE_RMS: f32 = 2.5e-4;
const AUDIO_STREAM_ERROR_LOG_INTERVAL: Duration = Duration::from_secs(60);
const AUDIO_STREAM_RECOVERY_DELAY: Duration = Duration::from_secs(1);
@@ -824,7 +825,7 @@ pub async fn run_aprs_decoder(
}
// Downmix to mono if stereo
let mono = if channels > 1 {
let mut mono = if channels > 1 {
let num_frames = frame.len() / channels as usize;
let mut mono = Vec::with_capacity(num_frames);
for i in 0..num_frames {
@@ -834,6 +835,7 @@ pub async fn run_aprs_decoder(
} else {
frame
};
apply_decode_audio_gate(&mut mono);
was_active = true;
for pkt in decoder.process_samples(&mono) {
@@ -1125,7 +1127,7 @@ pub async fn run_cw_decoder(
}
// Downmix to mono if stereo
let mono = if channels > 1 {
let mut mono = if channels > 1 {
let num_frames = frame.len() / channels as usize;
let mut mono = Vec::with_capacity(num_frames);
for i in 0..num_frames {
@@ -1135,6 +1137,7 @@ pub async fn run_cw_decoder(
} else {
frame
};
apply_decode_audio_gate(&mut mono);
was_active = true;
for evt in decoder.process_samples(&mono) {
@@ -1200,6 +1203,27 @@ fn downmix_mono(frame: Vec<f32>, channels: u16) -> Vec<f32> {
mono
}
fn frame_rms(samples: &[f32]) -> f32 {
if samples.is_empty() {
return 0.0;
}
let mut sum_sq = 0.0f32;
for &sample in samples {
sum_sq += sample * sample;
}
(sum_sq / samples.len() as f32).sqrt()
}
fn apply_decode_audio_gate(samples: &mut [f32]) -> bool {
if frame_rms(samples) >= DECODE_AUDIO_GATE_RMS {
return false;
}
for sample in samples {
*sample = 0.0;
}
true
}
fn resample_to_12k(samples: &[f32], sample_rate: u32) -> Option<Vec<f32>> {
if sample_rate == FT8_SAMPLE_RATE {
return Some(samples.to_vec());
@@ -1291,7 +1315,8 @@ pub async fn run_ft8_decoder(
ft8_buf.clear();
}
let mono = downmix_mono(frame, channels);
let mut mono = downmix_mono(frame, channels);
apply_decode_audio_gate(&mut mono);
let Some(resampled) = resample_to_12k(&mono, sample_rate) else {
warn!("FT8 decoder: unsupported sample rate {}", sample_rate);
break;
@@ -1452,7 +1477,8 @@ pub async fn run_wspr_decoder(
last_slot = slot;
}
let mono = downmix_mono(frame, channels);
let mut mono = downmix_mono(frame, channels);
apply_decode_audio_gate(&mut mono);
let Some(resampled) = resample_to_12k(&mono, sample_rate) else {
warn!("WSPR decoder: unsupported sample rate {}", sample_rate);
break;