almost there, i can smell it (input_dsp.rs)

src/audio_receiver/input_dsp.rs

@@ -3,6 +3,8 @@ use std::io::Write;
 
 use cpal::{FromSample, Sample, SampleRate};
 
+use tracing::{debug, trace, warn};
+
 use rustfft::{num_complex::Complex, FftPlanner};
 
 use super::ForeignTwoStateCarrier;
@@ -25,14 +27,14 @@ pub fn take_input_pcm<T>(
     }));
 
     let mut fft_planner = FftPlanner::<f64>::new();
-    let fft_machine = fft_planner.plan_fft_forward(fft_size);
 
     // Zero-pad for a better freq resolution. 8192 fft should be fast enough
     let mut window_offset = 0;
-    let mut prev_phase = f64::NAN;
+    let mut prev_phase = f64::MAX;
 
     // window must not extend beyond pcm_buffer
-    while !carrier.acquired && window_offset + pcm_buffer.len() < fft_size {
+    while !carrier.acquired && window_offset + fft_size < pcm_buffer.len() {
+        trace!("carrier acq: trying, window offset {window_offset}");
         let pcm_buffer_contiguous = pcm_buffer.make_contiguous();
         let mut fft_frame: Vec<Complex<f64>> = if fft_size < 8192 {
             let mut frm = 
@@ -45,26 +47,56 @@ pub fn take_input_pcm<T>(
             pcm_buffer_contiguous[window_offset..(fft_size+window_offset)]
                 .to_vec()
         };
-
+        let fft_machine = fft_planner.plan_fft_forward(fft_frame.len());
         fft_machine.process(&mut fft_frame);
+
         let clock_freq_index = 
             (fft_size as f64 * carrier.clock_hz / sample_rate.0 as f64)
             .round() as usize;
 
         if let Some(bin) = fft_frame.get(clock_freq_index) {
-            if bin.re + bin.im < 0.000000001 { break; } // too small to use.
+            // if too small to use. threshold is arbitrary and needs tuning
-                                                        // arbitrary number; 
+            let threshold = 0.000000001;
-                                                        // tune as needed
+            if bin.re + bin.im < threshold { 
+                trace!(
+                    "carrier acq: nothing ({}) below cutoff threshold {}. stop",
+                    bin.re + bin.im,
+                    threshold,
+                );
+                break;
+            } 
+
             let phase = f64::atan2(bin.im, bin.re);
+            let ampl = bin.norm();
 
             // if the phase just passed 0, increasing:
-            if phase > 0.0 && phase - prev_phase > 0.0 {
+            if phase > 0.0 && prev_phase < 0.0 {
                 carrier.acquired = true;
+                debug!("carrier acq: success!");
+                debug!(
+                    "carrier acq: drift {} matching {} ampl {}, nearest bin {}",
+                    phase,
+                    window_offset,
+                    ampl,
+                    sample_rate.0 as usize * clock_freq_index / fft_size,
+                );
             } else {
                 window_offset += 1;
+                if window_offset > fft_size {
+                    trace!("carrier acq: can't find what i smell. stop");
+                    break;
+                }
+                trace!(
+                    "carrier acq: carrier ampl {} but phase {}, spinning...",
+                    ampl,
+                    phase,                    
+                );
             }
             prev_phase = phase;
-        } else { break; }
+        } else { 
+            warn!("carrier acq: window overran FFT frame! report this!");
+            break; 
+        }
     }
 
     while carrier.acquired && pcm_buffer.len() >= fft_size {

src/main.rs

@@ -1,3 +1,4 @@
+// Do not be complaining for these things while I develop
 #![cfg_attr(
     debug_assertions,
     allow(dead_code, unused_imports, unused_variables)