优化vad检测：如果检测区间最大值的绝对值小于1则维持原样，反之则做归一化。

Author: Ivy233

sense-voice/csrc/sense-voice-frontend.h

@@ -127,13 +127,28 @@ bool load_wav_file(const char *filename, int32_t *sampling_rate,
 
 
 template<typename T>
-bool vad_energy_zcr(const typename std::vector<T>::const_iterator& pcmf32, size_t siz, int sample_rate, T energy_threshold = 0.01, T zcr_threshold = 0.2, bool verbose = false)
+bool vad_energy_zcr(const typename std::vector<T>::const_iterator& pcmf32, size_t siz, int sample_rate,
+                    T energy_threshold = 0.01, T zcr_threshold = 0.2, bool verbose = false)
 {
     const int frame_size = 256; // 16ms at 16kHz
     const int frame_shift = 128; // 50% overlap
-    
+
     if (siz < frame_size) return false;
 
+    // 1. 计算输入信号的绝对最大值进行归一化
+    T max_val = 0.0f;
+    for (size_t i = 0; i < siz; ++i) {
+        T val = std::abs(*(pcmf32 + i));
+        if (val > max_val) {
+            max_val = val;
+        }
+    }
+    // 防止除以零
+    if (max_val < 1) {
+        max_val = 1;
+    }
+    T scale = 1.0f / max_val;
+
     int num_frames = (siz - frame_size) / frame_shift + 1;
     std::vector<T> energies(num_frames);
     std::vector<T> zcrs(num_frames);
@@ -142,17 +157,14 @@ bool vad_energy_zcr(const typename std::vector<T>::const_iterator& pcmf32, size_
     for (int f = 0; f < num_frames; f++) {
         T energy = 0.0f;
         int zcr = 0;
-        
         int frame_start = f * frame_shift;
-        
         // Calculate energy
         for (int i = 0; i < frame_size; i++) {
-            T sample = pcmf32[frame_start + i];
+            T sample = pcmf32[frame_start + i] * scale;
             energy += sample * sample;
         }
         energy /= frame_size;
         energies[f] = energy;
-        
         // Calculate zero-crossing rate
         for (int i = 1; i < frame_size; i++) {
             if ((pcmf32[frame_start + i - 1] * pcmf32[frame_start + i]) < 0)
@@ -172,7 +184,7 @@ bool vad_energy_zcr(const typename std::vector<T>::const_iterator& pcmf32, size_
     avg_zcr /= num_frames;
 
     if (verbose) {
-        fprintf(stderr, "%s: avg_energy: %f, avg_zcr: %f, energy_threshold: %f, zcr_threshold: %f\n", 
+        fprintf(stderr, "%s: avg_energy: %f, avg_zcr: %f, energy_threshold: %f, zcr_threshold: %f\n",
                 __func__, avg_energy, avg_zcr, energy_threshold, zcr_threshold);
     }