Unify recorder CPU demod fallback path

internal/recorder/cpu_audio.go

@@ -0,0 +1,25 @@
+package recorder
+
+import (
+	"math"
+
+	"sdr-visual-suite/internal/demod"
+	"sdr-visual-suite/internal/dsp"
+)
+
+func demodAudioCPU(d demod.Demodulator, iq []complex64, sampleRate int, offset float64, bw float64) ([]float32, int) {
+	shifted := dsp.FreqShift(iq, sampleRate, offset)
+	cutoff := bw / 2
+	if cutoff < 200 {
+		cutoff = 200
+	}
+	taps := dsp.LowpassFIR(cutoff, sampleRate, 101)
+	filtered := dsp.ApplyFIR(shifted, taps)
+	decim := int(math.Round(float64(sampleRate) / float64(d.OutputSampleRate())))
+	if decim < 1 {
+		decim = 1
+	}
+	dec := dsp.Decimate(filtered, decim)
+	inputRate := sampleRate / decim
+	return d.Demod(dec, inputRate), inputRate
+}

internal/recorder/demod.go

@@ -3,13 +3,11 @@ package recorder
 import (
 	"errors"
 	"log"
-	"math"
 	"path/filepath"
 
 	"sdr-visual-suite/internal/classifier"
 	"sdr-visual-suite/internal/demod"
 	"sdr-visual-suite/internal/detector"
-	"sdr-visual-suite/internal/dsp"
 )
 
 func (m *Manager) demodAndWrite(dir string, ev detector.Event, iq []complex64, files map[string]any) error {
@@ -44,20 +42,7 @@ func (m *Manager) demodAndWrite(dir string, ev detector.Event, iq []complex64, f
 		} else {
 			log.Printf("gpudemod: CPU demod fallback used for event %d (%s)", ev.ID, name)
 		}
-		shifted := dsp.FreqShift(iq, m.sampleRate, offset)
-		cutoff := bw / 2
-		if cutoff < 200 {
-			cutoff = 200
-		}
-		taps := dsp.LowpassFIR(cutoff, m.sampleRate, 101)
-		filtered := dsp.ApplyFIR(shifted, taps)
-		decim := int(math.Round(float64(m.sampleRate) / float64(d.OutputSampleRate())))
-		if decim < 1 {
-			decim = 1
-		}
-		dec := dsp.Decimate(filtered, decim)
-		inputRate = m.sampleRate / decim
-		audio = d.Demod(dec, inputRate)
+		audio, inputRate = demodAudioCPU(d, iq, m.sampleRate, offset, bw)
 	}
 	wav := filepath.Join(dir, "audio.wav")
 	if err := writeWAV(wav, audio, inputRate, d.Channels()); err != nil {

internal/recorder/demod_live.go

@@ -4,11 +4,9 @@ import (
 	"bytes"
 	"errors"
 	"log"
-	"math"
 	"time"
 
 	"sdr-visual-suite/internal/demod"
-	"sdr-visual-suite/internal/dsp"
 )
 
 // DemodLive demodulates a recent window and returns WAV bytes.
@@ -61,20 +59,7 @@ func (m *Manager) DemodLive(centerHz float64, bw float64, mode string, seconds i
 		} else {
 			log.Printf("gpudemod: CPU live demod fallback used (%s)", name)
 		}
-		shifted := dsp.FreqShift(segment, m.sampleRate, offset)
-		cutoff := bw / 2
-		if cutoff < 200 {
-			cutoff = 200
-		}
-		taps := dsp.LowpassFIR(cutoff, m.sampleRate, 101)
-		filtered := dsp.ApplyFIR(shifted, taps)
-		decim := int(math.Round(float64(m.sampleRate) / float64(d.OutputSampleRate())))
-		if decim < 1 {
-			decim = 1
-		}
-		dec := dsp.Decimate(filtered, decim)
-		inputRate = m.sampleRate / decim
-		audio = d.Demod(dec, inputRate)
+		audio, inputRate = demodAudioCPU(d, segment, m.sampleRate, offset, bw)
 	}
 	buf := &bytes.Buffer{}
 	if err := writeWAVTo(buf, audio, inputRate, d.Channels()); err != nil {