feat: add audio demodulation and FFT processing, enhance audio input handling and visualization

2025-12-12 00:47:09 +08:00
parent 8507029499
commit ec9d9a389e
9 changed files with 566 additions and 16 deletions
--- a/android/app/src/main/cpp/audio_demod.cpp
+++ b/android/app/src/main/cpp/audio_demod.cpp
@@ -0,0 +1,106 @@
+#include "audio_demod.h"
+#include "demod.h"
+#include <android/log.h>
+#include <cmath>
+#include <cstring>
+
+#define LOG_TAG "AudioDemod"
+#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
+
+#define FINE_CLKT_HI 1.90
+#define FINE_CLKT_LO 0.32
+#define SAMPLE_RATE 48000
+#define BAUD_RATE 1200
+
+static double watch_ctr = 0.0;
+static double atb_ctr = 0.0;
+static double clkt = (double)SAMPLE_RATE / BAUD_RATE;
+static int last_value = 0;
+static int preamble_count = 0;
+static int pocbit = 0;
+static bool preamble_detected = false;
+static int crossing_count = 0;
+static int nSamples = 0;
+
+static const int AUDIO_THRESHOLD = 128;
+
+void resetAudioDemod() {
+    watch_ctr = 0.0;
+    atb_ctr = 0.0;
+    clkt = (double)SAMPLE_RATE / BAUD_RATE;
+    last_value = 0;
+    preamble_count = 0;
+    pocbit = 0;
+    preamble_detected = false;
+    crossing_count = 0;
+    nSamples = 0;
+    LOGD("Audio demodulator reset");
+}
+
+void processAudioSamples(int16_t *samples, int size) {
+    for (int i = 0; i < size; i++) {
+        int audio_value = (samples[i] + 32768) / 256;
+        
+        if (audio_value < 0) audio_value = 0;
+        if (audio_value > 255) audio_value = 255;
+        
+        int current_bit = (audio_value > AUDIO_THRESHOLD) ? 1 : 0;
+        
+        if (current_bit != last_value) {
+            crossing_count++;
+            
+            if ((nSamples > 28) && (nSamples < 44)) {
+                preamble_count++;
+                
+                if (preamble_count > 50 && !preamble_detected) {
+                    preamble_detected = true;
+                    pocbit = 0;
+                    LOGD("Preamble detected! crossings=%d samples=%d", preamble_count, nSamples);
+                }
+            }
+            
+            nSamples = 0;
+        }
+        
+        nSamples++;
+        last_value = current_bit;
+        
+        watch_ctr += 1.0;
+        
+        if (watch_ctr - atb_ctr < 1.0) {
+            int bit = current_bit;
+            
+            if (preamble_detected) {
+                processBasebandSample(bit);
+                pocbit++;
+                
+                if (pocbit > 1250) {
+                    LOGD("POCSAG timeout - no sync after 1250 bits");
+                    preamble_detected = false;
+                    preamble_count = 0;
+                    pocbit = 0;
+                }
+            }
+            
+            if (crossing_count > 0) {
+                double offset = watch_ctr - atb_ctr;
+                
+                if (offset > FINE_CLKT_HI) {
+                    clkt -= 0.01;
+                    if (clkt < (SAMPLE_RATE / BAUD_RATE) * 0.95) {
+                        clkt = (SAMPLE_RATE / BAUD_RATE) * 0.95;
+                    }
+                } else if (offset < FINE_CLKT_LO) {
+                    clkt += 0.01;
+                    if (clkt > (SAMPLE_RATE / BAUD_RATE) * 1.05) {
+                        clkt = (SAMPLE_RATE / BAUD_RATE) * 1.05;
+                    }
+                }
+                
+                crossing_count = 0;
+            }
+            
+            atb_ctr += clkt;
+        }
+    }
+}