From 0bb70e7966bd6fcf676eb2e686bafed23cdba7e0 Mon Sep 17 00:00:00 2001
From: Chris Frankland-Wright <christopherjfrankland@googlemail.com>
Date: Tue, 24 Jun 2025 21:39:53 +0100
Subject: [PATCH] improved probe

---
 ltc_probe.py | 64 +++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 18 deletions(-)

diff --git a/ltc_probe.py b/ltc_probe.py
index 4b63d37..93c3c88 100644
--- a/ltc_probe.py
+++ b/ltc_probe.py
@@ -2,8 +2,8 @@
 
 """
 ltc_probe.py
-Probes audio input to detect LTC-like signal characteristics.
-Reports zero crossings and estimated frequency.
+Improved LTC-like signal probe — detects pulse duration patterns
+consistent with bi-phase mark code used in SMPTE LTC.
 """
 
 import numpy as np
@@ -12,32 +12,60 @@ import sounddevice as sd
 DURATION = 1.0  # seconds
 SAMPLERATE = 48000
 CHANNELS = 1
-EXPECTED_FREQ = 2000  # Approx LTC edge rate at 25fps
+MIN_EDGES = 1000  # sanity threshold
 
-def count_zero_crossings(signal):
-    signal = signal.flatten()
-    signs = np.sign(signal)
-    return np.count_nonzero(np.diff(signs))
+def detect_rising_edges(signal):
+    # signal: flattened 1D numpy array
+    above_zero = signal > 0
+    edges = np.where(np.logical_and(~above_zero[:-1], above_zero[1:]))[0]
+    return edges
 
-def verdict(freq):
-    if freq < 100:
-        return "❌ No signal detected (flatline or silence)"
-    elif 1800 <= freq <= 2200:
-        return f"✅ LTC-like signal detected (freq: {freq:.1f} Hz)"
+def analyze_pulse_durations(edges, samplerate):
+    durations = np.diff(edges) / samplerate  # in seconds
+    if len(durations) == 0:
+        return None
+
+    short_pulse_threshold = np.median(durations) * 1.5
+    short = durations[durations <= short_pulse_threshold]
+    long = durations[durations > short_pulse_threshold]
+
+    return {
+        "count": len(durations),
+        "avg_width_ms": np.mean(durations) * 1000,
+        "short_pulses": len(short),
+        "long_pulses": len(long),
+        "short_pct": (len(short) / len(durations)) * 100,
+        "long_pct": (len(long) / len(durations)) * 100
+    }
+
+def verdict(pulse_data):
+    if pulse_data is None or pulse_data["count"] < MIN_EDGES:
+        return "❌ No signal or not enough pulses"
+    elif 30 < pulse_data["short_pct"] < 70:
+        return f"✅ LTC-like bi-phase signal detected ({pulse_data['count']} pulses)"
     else:
-        return f"⚠️ Unstable or non-LTC signal (freq: {freq:.1f} Hz)"
+        return f"⚠️ Inconsistent signal — may be non-LTC or noisy"
 
 def main():
     print("🔍 Capturing 1 second of audio for LTC probing...")
     audio = sd.rec(int(DURATION * SAMPLERATE), samplerate=SAMPLERATE, channels=CHANNELS, dtype='float32')
     sd.wait()
 
-    crossings = count_zero_crossings(audio)
-    estimated_freq = crossings / DURATION
+    signal = audio.flatten()
+    edges = detect_rising_edges(signal)
+    pulse_data = analyze_pulse_durations(edges, SAMPLERATE)
 
-    print(f"Zero crossings: {crossings}")
-    print(f"Estimated frequency: {estimated_freq:.1f} Hz")
-    print(verdict(estimated_freq))
+    print(f"\n📊 Pulse Analysis:")
+    if pulse_data:
+        print(f"  Total pulses:      {pulse_data['count']}")
+        print(f"  Avg pulse width:   {pulse_data['avg_width_ms']:.2f} ms")
+        print(f"  Short pulses:      {pulse_data['short_pulses']} ({pulse_data['short_pct']:.1f}%)")
+        print(f"  Long pulses:       {pulse_data['long_pulses']} ({pulse_data['long_pct']:.1f}%)")
+    else:
+        print("  Not enough data to analyze.")
+
+    print("\n🧭 Verdict:")
+    print(" ", verdict(pulse_data))
 
 if __name__ == "__main__":
     main()