/***************************************************************A.1 aec.h***************************************************************/#ifndef _AEC_H	/* include only once *//* aec.h * Acoustic Echo Cancellation NLMS-pw algorithm * Author: Andre Adrian, DFS Deutsche Flugsicherung * <Andre.Adrian@dfs.de> * * Version 1.1 *//* dB Values */const float M3dB = 0.71f;const float M6dB = 0.50f; /* dB values for 16bit PCM */const float M10dB_PCM = 10362.0f;   const float M20dB_PCM = 3277.0f;const float M25dB_PCM = 1843.0f;const float M30dB_PCM = 1026.0f;const float M35dB_PCM = 583.0f;const float M40dB_PCM = 328.0f;   const float M45dB_PCM = 184.0f;const float M50dB_PCM = 104.0f;const float M55dB_PCM = 58.0f;const float M60dB_PCM = 33.0f;const float MAXPCM = 32767.0f;/* Design constants (Change to fine tune the algorithms *//* For Normalized Least Means Square - Pre-whitening */#define NLMS_LEN  (80*8)      	  /* NLMS filter length in taps */const float PreWhiteTransferFreq = 4000.0f;/* for Geigel Double Talk Detector */const float GeigelThreshold = M6dB;const int Thold = 30*8;       	      	  /* DTD hangover in taps */const float UpdateThreshold = M50dB_PCM;/* for Non Linear Processor */const float NLPAttenuation = M6dB;/* Below this line there are no more design constants *//* Exponential Smoothing or IIR Infinite Impulse Response Filter */class IIR {  float lowpassf;public:  IIR() {    lowpassf = 0.0f;  }  float highpass(float in) {    const float ALPHADC = 0.01f;  /* controls Transfer Frequence */    lowpassf += ALPHADC*(in - lowpassf);    return in - lowpassf;  }};#define POL   	6     	/* -6dB attenuation per octave per Pol */class IIR6 {  float lowpassf[2*POL+1];  float highpassf[2*POL+1];public:  IIR6();  float highpass(float in) {    const float AlphaHp = (float)0.075;  /* controls Transfer Frequence */    const float Gain6   = 1.45f;  /* gain to undo filter attenuation */    /* Highpass = Signal - Lowpass. Lowpass = Exponential Smoothing */    highpassf[0] = in;    int i;    for (i = 0; i < 2*POL; ++i) {      lowpassf[i+1] += AlphaHp*(highpassf[i] - lowpassf[i+1]);      highpassf[i+1] = highpassf[i] - lowpassf[i+1];    }    return Gain6*highpassf[2*POL];     }  float lowpass(float in);};  /* Recursive single pole FIR Finite Impule response filter */class FIR1 {  float a0, a1, b1;  float last_in, last_out;  public:  FIR1();  float highpass(float in)  {    float out = a0 * in + a1 * last_in + b1 * last_out;    last_in = in;    last_out = out;    return out;  }};#define NLMS_EXT  (10*8)    // Extention in taps to optimize mem copies#define DTD_LEN 16          // block size in taps to optimize DTD calculationclass AEC {  // Time domain Filters  IIR dc0, dc1;       	  // DC-level running average (IIR highpass)  IIR6 hp0;              // 300Hz cut-off Highpass  FIR1 Fx, Fe;       	  // pre-whitening Filter for x, e      // Geigel DTD (Double Talk Detector)  float max_max_x;                // max(|x[0]|, .. |x[L-1]|)  int hangover;  float max_x[NLMS_LEN/DTD_LEN];  // optimize: less calculations for max()  int dtdCnt;                       int dtdNdx;    // NLMS-pw  float x[NLMS_LEN+NLMS_EXT]; 	  // tap delayed loudspeaker signal  float xf[NLMS_LEN+NLMS_EXT];    // pre-whitening tap delayed signal  float w[NLMS_LEN];	      	  // tap weights  int j;      	      	      	  // optimize: less memory copies  int lastupdate;     	      	  // optimize: iterative dotp(x,x)  float dotp_xf_xf;               // optimize: iterative dotp(x,x)  public:  AEC();  int dtd(float d, float x);  float nlms_pw(float mic, float spk, int update);  /* Acoustic Echo Cancellation and Suppression of one sample * in   s0: microphone signal with echo * in   s1: loudspeaker signal * return:  echo cancelled microphone signal */  int AEC::doAEC(int d, int x);};#define _AEC_H#endif