--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/cnst_vad.h	Tue May 07 00:56:10 2024 +0000
@@ -0,0 +1,105 @@
+/*
+********************************************************************************
+**-------------------------------------------------------------------------**
+**                                                                         **
+**     GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001       **
+**                               R99   Version 3.3.0                       **
+**                               REL-4 Version 4.1.0                       **
+**                                                                         **
+**-------------------------------------------------------------------------**
+********************************************************************************
+*
+*      File             : cnst_vad.h
+*      Purpose          : Constants and definitions for VAD
+*
+********************************************************************************
+*/
+#ifndef cnst_vad_h
+#define cnst_vad_h "$Id $"
+
+#define FRAME_LEN 160    /* Length (samples) of the input frame          */
+#define COMPLEN 9        /* Number of sub-bands used by VAD              */
+#define INV_COMPLEN 3641 /* 1.0/COMPLEN*2^15                             */
+#define LOOKAHEAD 40     /* length of the lookahead used by speech coder */
+
+#define UNITY 512        /* Scaling used with SNR calculation            */
+#define UNIRSHFT 6       /* = log2(MAX_16/UNITY)                         */
+
+#define TONE_THR (Word16)(0.65*MAX_16) /* Threshold for tone detection   */
+
+/* Constants for background spectrum update */
+#define ALPHA_UP1   (Word16)((1.0 - 0.95)*MAX_16)  /* Normal update, upwards:   */
+#define ALPHA_DOWN1 (Word16)((1.0 - 0.936)*MAX_16) /* Normal update, downwards  */
+#define ALPHA_UP2   (Word16)((1.0 - 0.985)*MAX_16) /* Forced update, upwards    */
+#define ALPHA_DOWN2 (Word16)((1.0 - 0.943)*MAX_16) /* Forced update, downwards  */
+#define ALPHA3      (Word16)((1.0 - 0.95)*MAX_16)  /* Update downwards          */
+#define ALPHA4      (Word16)((1.0 - 0.9)*MAX_16)   /* For stationary estimation */
+#define ALPHA5      (Word16)((1.0 - 0.5)*MAX_16)   /* For stationary estimation */
+
+/* Constants for VAD threshold */
+#define VAD_THR_HIGH 1260 /* Highest threshold                 */
+#define VAD_THR_LOW  720  /* Lowest threshold                  */
+#define VAD_P1 0          /* Noise level for highest threshold */
+#define VAD_P2 6300       /* Noise level for lowest threshold  */
+#define VAD_SLOPE (Word16)(MAX_16*(float)(VAD_THR_LOW-VAD_THR_HIGH)/(float)(VAD_P2-VAD_P1))
+
+/* Parameters for background spectrum recovery function */
+#define STAT_COUNT 20         /* threshold of stationary detection counter         */
+#define STAT_COUNT_BY_2 10    /* threshold of stationary detection counter         */
+#define CAD_MIN_STAT_COUNT 5  /* threshold of stationary detection counter         */
+
+#define STAT_THR_LEVEL 184    /* Threshold level for stationarity detection        */
+#define STAT_THR 1000         /* Threshold for stationarity detection              */
+
+/* Limits for background noise estimate */
+#define NOISE_MIN 40          /* minimum */
+#define NOISE_MAX 16000       /* maximum */
+#define NOISE_INIT 150        /* initial */
+
+/* Constants for VAD hangover addition */
+#define HANG_NOISE_THR 100
+#define BURST_LEN_HIGH_NOISE 4
+#define HANG_LEN_HIGH_NOISE 7
+#define BURST_LEN_LOW_NOISE 5
+#define HANG_LEN_LOW_NOISE 4
+
+/* Thresholds for signal power */
+#define VAD_POW_LOW (Word32)15000     /* If input power is lower,                    */
+                                      /*     VAD is set to 0                         */
+#define POW_PITCH_THR (Word32)343040  /* If input power is lower, pitch              */
+                                      /*     detection is ignored                    */
+
+#define POW_COMPLEX_THR (Word32)15000 /* If input power is lower, complex            */
+                                      /* flags  value for previous frame  is un-set  */
+ 
+
+/* Constants for the filter bank */
+#define LEVEL_SHIFT 0      /* scaling                                  */
+#define COEFF3   13363     /* coefficient for the 3rd order filter     */
+#define COEFF5_1 21955     /* 1st coefficient the for 5th order filter */
+#define COEFF5_2 6390      /* 2nd coefficient the for 5th order filter */
+
+/* Constants for pitch detection */
+#define LTHRESH 4
+#define NTHRESH 4
+
+/* Constants for complex signal VAD  */
+#define CVAD_THRESH_ADAPT_HIGH  (Word16)(0.6 * MAX_16) /* threshold for adapt stopping high    */
+#define CVAD_THRESH_ADAPT_LOW  (Word16)(0.5 * MAX_16)  /* threshold for adapt stopping low     */
+#define CVAD_THRESH_IN_NOISE  (Word16)(0.65 * MAX_16)  /* threshold going into speech on
+                                                          a short term basis                   */
+
+#define CVAD_THRESH_HANG  (Word16)(0.70 * MAX_16)      /* threshold                            */
+#define CVAD_HANG_LIMIT  (Word16)(100)                 /* 2 second estimation time             */
+#define CVAD_HANG_LENGTH  (Word16)(250)                /* 5 second hangover                    */
+
+#define CVAD_LOWPOW_RESET (Word16) (0.40 * MAX_16)     /* init in low power segment            */
+#define CVAD_MIN_CORR (Word16) (0.40 * MAX_16)         /* lowest adaptation value              */
+
+#define CVAD_BURST 20                                  /* speech burst length for speech reset */
+#define CVAD_ADAPT_SLOW (Word16)(( 1.0 - 0.98) * MAX_16)        /* threshold for slow adaption */
+#define CVAD_ADAPT_FAST (Word16)((1.0 - 0.92) * MAX_16)         /* threshold for fast adaption */
+#define CVAD_ADAPT_REALLY_FAST (Word16)((1.0 - 0.80) * MAX_16)  /* threshold for really fast
+                                                                   adaption                    */
+
+#endif