modules/audio_coding/codecs/cng/webrtc_cng.cc - src/webrtc - Git at Google

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "webrtc/modules/audio_coding/codecs/cng/webrtc_cng.h"

 #include <algorithm>

 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 #include "webrtc/rtc_base/safe_conversions.h"

 namespace webrtc {

 namespace {

 const size_t kCngMaxOutsizeOrder = 640;

 // TODO(ossu): Rename the left-over WebRtcCng according to style guide.
 void WebRtcCng_K2a16(int16_t* k, int useOrder, int16_t* a);

 const int32_t WebRtcCng_kDbov[94] = {
   1081109975, 858756178, 682134279, 541838517, 430397633, 341876992,
   271562548,  215709799, 171344384, 136103682, 108110997, 85875618,
   68213428,   54183852,  43039763,  34187699,  27156255,  21570980,
   17134438,   13610368,  10811100,  8587562,   6821343,   5418385,
   4303976,    3418770,   2715625,   2157098,   1713444,   1361037,
   1081110,    858756,    682134,    541839,    430398,    341877,
   271563,     215710,    171344,    136104,    108111,    85876,
   68213,      54184,     43040,     34188,     27156,     21571,
   17134,      13610,     10811,     8588,      6821,      5418,
   4304,       3419,      2716,      2157,      1713,      1361,
   1081,       859,       682,       542,       430,       342,
   272,        216,       171,       136,       108,       86,
   68,         54,        43,        34,        27,        22,
   17,         14,        11,        9,         7,         5,
   4,          3,         3,         2,         2,         1,
   1,          1,         1,         1
 };

 const int16_t WebRtcCng_kCorrWindow[WEBRTC_CNG_MAX_LPC_ORDER] = {
   32702, 32636, 32570, 32505, 32439, 32374,
   32309, 32244, 32179, 32114, 32049, 31985
 };

 }  // namespace

 ComfortNoiseDecoder::ComfortNoiseDecoder() {
   /* Needed to get the right function pointers in SPLIB. */
   WebRtcSpl_Init();
   Reset();
 }

 void ComfortNoiseDecoder::Reset() {
   dec_seed_ = 7777;  /* For debugging only. */
   dec_target_energy_ = 0;
   dec_used_energy_ = 0;
   for (auto& c : dec_target_reflCoefs_)
     c = 0;
   for (auto& c : dec_used_reflCoefs_)
     c = 0;
   for (auto& c : dec_filtstate_)
     c = 0;
   for (auto& c : dec_filtstateLow_)
     c = 0;
   dec_order_ = 5;
   dec_target_scale_factor_ = 0;
   dec_used_scale_factor_ = 0;
 }

 void ComfortNoiseDecoder::UpdateSid(rtc::ArrayView<const uint8_t> sid) {
   int16_t refCs[WEBRTC_CNG_MAX_LPC_ORDER];
   int32_t targetEnergy;
   size_t length = sid.size();
   /* Throw away reflection coefficients of higher order than we can handle. */
   if (length > (WEBRTC_CNG_MAX_LPC_ORDER + 1))
     length = WEBRTC_CNG_MAX_LPC_ORDER + 1;

   dec_order_ = static_cast<uint16_t>(length - 1);

   uint8_t sid0 = std::min<uint8_t>(sid[0], 93);
   targetEnergy = WebRtcCng_kDbov[sid0];
   /* Take down target energy to 75%. */
   targetEnergy = targetEnergy >> 1;
   targetEnergy += targetEnergy >> 2;

   dec_target_energy_ = targetEnergy;

   /* Reconstruct coeffs with tweak for WebRtc implementation of RFC3389. */
   if (dec_order_ == WEBRTC_CNG_MAX_LPC_ORDER) {
     for (size_t i = 0; i < (dec_order_); i++) {
       refCs[i] = sid[i + 1] << 8; /* Q7 to Q15*/
       dec_target_reflCoefs_[i] = refCs[i];
     }
   } else {
     for (size_t i = 0; i < (dec_order_); i++) {
       refCs[i] = (sid[i + 1] - 127) << 8; /* Q7 to Q15. */
       dec_target_reflCoefs_[i] = refCs[i];
     }
   }

   for (size_t i = (dec_order_); i < WEBRTC_CNG_MAX_LPC_ORDER; i++) {
     refCs[i] = 0;
     dec_target_reflCoefs_[i] = refCs[i];
   }
 }

 bool ComfortNoiseDecoder::Generate(rtc::ArrayView<int16_t> out_data,
                                    bool new_period) {
   int16_t excitation[kCngMaxOutsizeOrder];
   int16_t low[kCngMaxOutsizeOrder];
   int16_t lpPoly[WEBRTC_CNG_MAX_LPC_ORDER + 1];
   int16_t ReflBetaStd = 26214;  /* 0.8 in q15. */
   int16_t ReflBetaCompStd = 6553;  /* 0.2 in q15. */
   int16_t ReflBetaNewP = 19661;  /* 0.6 in q15. */
   int16_t ReflBetaCompNewP = 13107;  /* 0.4 in q15. */
   int16_t Beta, BetaC;  /* These are in Q15. */
   int32_t targetEnergy;
   int16_t En;
   int16_t temp16;
   const size_t num_samples = out_data.size();

   if (num_samples > kCngMaxOutsizeOrder) {
     return false;
   }

   if (new_period) {
     dec_used_scale_factor_ = dec_target_scale_factor_;
     Beta = ReflBetaNewP;
     BetaC = ReflBetaCompNewP;
   } else {
     Beta = ReflBetaStd;
     BetaC = ReflBetaCompStd;
   }

   /* Calculate new scale factor in Q13 */
   dec_used_scale_factor_ =
       rtc::checked_cast<int16_t>(
           WEBRTC_SPL_MUL_16_16_RSFT(dec_used_scale_factor_, Beta >> 2, 13) +
           WEBRTC_SPL_MUL_16_16_RSFT(dec_target_scale_factor_, BetaC >> 2, 13));

   dec_used_energy_  = dec_used_energy_ >> 1;
   dec_used_energy_ += dec_target_energy_ >> 1;

   /* Do the same for the reflection coeffs, albeit in Q15. */
   for (size_t i = 0; i < WEBRTC_CNG_MAX_LPC_ORDER; i++) {
     dec_used_reflCoefs_[i] = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
         dec_used_reflCoefs_[i], Beta, 15);
     dec_used_reflCoefs_[i] += (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
         dec_target_reflCoefs_[i], BetaC, 15);
   }

   /* Compute the polynomial coefficients. */
   WebRtcCng_K2a16(dec_used_reflCoefs_, WEBRTC_CNG_MAX_LPC_ORDER, lpPoly);


   targetEnergy = dec_used_energy_;

   /* Calculate scaling factor based on filter energy. */
   En = 8192;  /* 1.0 in Q13. */
   for (size_t i = 0; i < (WEBRTC_CNG_MAX_LPC_ORDER); i++) {
     /* Floating point value for reference.
        E *= 1.0 - (dec_used_reflCoefs_[i] / 32768.0) *
        (dec_used_reflCoefs_[i] / 32768.0);
      */

     /* Same in fixed point. */
     /* K(i).^2 in Q15. */
     temp16 = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
         dec_used_reflCoefs_[i], dec_used_reflCoefs_[i], 15);
     /* 1 - K(i).^2 in Q15. */
     temp16 = 0x7fff - temp16;
     En = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(En, temp16, 15);
   }

   /* float scaling= sqrt(E * dec_target_energy_ / (1 << 24)); */

   /* Calculate sqrt(En * target_energy / excitation energy) */
   targetEnergy = WebRtcSpl_Sqrt(dec_used_energy_);

   En = (int16_t) WebRtcSpl_Sqrt(En) << 6;
   En = (En * 3) >> 1;  /* 1.5 estimates sqrt(2). */
   dec_used_scale_factor_ = (int16_t)((En * targetEnergy) >> 12);

   /* Generate excitation. */
   /* Excitation energy per sample is 2.^24 - Q13 N(0,1). */
   for (size_t i = 0; i < num_samples; i++) {
     excitation[i] = WebRtcSpl_RandN(&dec_seed_) >> 1;
   }

   /* Scale to correct energy. */
   WebRtcSpl_ScaleVector(excitation, excitation, dec_used_scale_factor_,
                         num_samples, 13);

   /* |lpPoly| - Coefficients in Q12.
    * |excitation| - Speech samples.
    * |nst->dec_filtstate| - State preservation.
    * |out_data| - Filtered speech samples. */
   WebRtcSpl_FilterAR(lpPoly, WEBRTC_CNG_MAX_LPC_ORDER + 1, excitation,
                      num_samples, dec_filtstate_, WEBRTC_CNG_MAX_LPC_ORDER,
                      dec_filtstateLow_, WEBRTC_CNG_MAX_LPC_ORDER,
                      out_data.data(), low, num_samples);

   return true;
 }

 ComfortNoiseEncoder::ComfortNoiseEncoder(int fs, int interval, int quality)
     : enc_nrOfCoefs_(quality),
       enc_sampfreq_(fs),
       enc_interval_(interval),
       enc_msSinceSid_(0),
       enc_Energy_(0),
       enc_reflCoefs_{0},
       enc_corrVector_{0},
       enc_seed_(7777)  /* For debugging only. */ {
   RTC_CHECK_GT(quality, 0);
   RTC_CHECK_LE(quality, WEBRTC_CNG_MAX_LPC_ORDER);
   /* Needed to get the right function pointers in SPLIB. */
   WebRtcSpl_Init();
 }

 void ComfortNoiseEncoder::Reset(int fs, int interval, int quality) {
   RTC_CHECK_GT(quality, 0);
   RTC_CHECK_LE(quality, WEBRTC_CNG_MAX_LPC_ORDER);
   enc_nrOfCoefs_ = quality;
   enc_sampfreq_ = fs;
   enc_interval_ = interval;
   enc_msSinceSid_ = 0;
   enc_Energy_ = 0;
   for (auto& c : enc_reflCoefs_)
     c = 0;
   for (auto& c : enc_corrVector_)
     c = 0;
   enc_seed_ = 7777;  /* For debugging only. */
 }

 size_t ComfortNoiseEncoder::Encode(rtc::ArrayView<const int16_t> speech,
                                    bool force_sid,
                                    rtc::Buffer* output) {
   int16_t arCoefs[WEBRTC_CNG_MAX_LPC_ORDER + 1];
   int32_t corrVector[WEBRTC_CNG_MAX_LPC_ORDER + 1];
   int16_t refCs[WEBRTC_CNG_MAX_LPC_ORDER + 1];
   int16_t hanningW[kCngMaxOutsizeOrder];
   int16_t ReflBeta = 19661;     /* 0.6 in q15. */
   int16_t ReflBetaComp = 13107; /* 0.4 in q15. */
   int32_t outEnergy;
   int outShifts;
   size_t i;
   int stab;
   int acorrScale;
   size_t index;
   size_t ind, factor;
   int32_t* bptr;
   int32_t blo, bhi;
   int16_t negate;
   const int16_t* aptr;
   int16_t speechBuf[kCngMaxOutsizeOrder];

   const size_t num_samples = speech.size();
   RTC_CHECK_LE(num_samples, kCngMaxOutsizeOrder);

   for (i = 0; i < num_samples; i++) {
     speechBuf[i] = speech[i];
   }

   factor = num_samples;

   /* Calculate energy and a coefficients. */
   outEnergy = WebRtcSpl_Energy(speechBuf, num_samples, &outShifts);
   while (outShifts > 0) {
     /* We can only do 5 shifts without destroying accuracy in
      * division factor. */
     if (outShifts > 5) {
       outEnergy <<= (outShifts - 5);
       outShifts = 5;
     } else {
       factor /= 2;
       outShifts--;
     }
   }
   outEnergy = WebRtcSpl_DivW32W16(outEnergy, (int16_t)factor);

   if (outEnergy > 1) {
     /* Create Hanning Window. */
     WebRtcSpl_GetHanningWindow(hanningW, num_samples / 2);
     for (i = 0; i < (num_samples / 2); i++)
       hanningW[num_samples - i - 1] = hanningW[i];

     WebRtcSpl_ElementwiseVectorMult(speechBuf, hanningW, speechBuf, num_samples,
                                     14);

     WebRtcSpl_AutoCorrelation(speechBuf, num_samples, enc_nrOfCoefs_,
                               corrVector, &acorrScale);

     if (*corrVector == 0)
       *corrVector = WEBRTC_SPL_WORD16_MAX;

     /* Adds the bandwidth expansion. */
     aptr = WebRtcCng_kCorrWindow;
     bptr = corrVector;

     /* (zzz) lpc16_1 = 17+1+820+2+2 = 842 (ordo2=700). */
     for (ind = 0; ind < enc_nrOfCoefs_; ind++) {
       /* The below code multiplies the 16 b corrWindow values (Q15) with
        * the 32 b corrvector (Q0) and shifts the result down 15 steps. */
       negate = *bptr < 0;
       if (negate)
         *bptr = -*bptr;

       blo = (int32_t) * aptr * (*bptr & 0xffff);
       bhi = ((blo >> 16) & 0xffff)
           + ((int32_t)(*aptr++) * ((*bptr >> 16) & 0xffff));
       blo = (blo & 0xffff) | ((bhi & 0xffff) << 16);

       *bptr = (((bhi >> 16) & 0x7fff) << 17) | ((uint32_t) blo >> 15);
       if (negate)
         *bptr = -*bptr;
       bptr++;
     }
     /* End of bandwidth expansion. */

     stab = WebRtcSpl_LevinsonDurbin(corrVector, arCoefs, refCs,
                                     enc_nrOfCoefs_);

     if (!stab) {
       /* Disregard from this frame */
       return 0;
     }

   } else {
     for (i = 0; i < enc_nrOfCoefs_; i++)
       refCs[i] = 0;
   }

   if (force_sid) {
     /* Read instantaneous values instead of averaged. */
     for (i = 0; i < enc_nrOfCoefs_; i++)
       enc_reflCoefs_[i] = refCs[i];
     enc_Energy_ = outEnergy;
   } else {
     /* Average history with new values. */
     for (i = 0; i < enc_nrOfCoefs_; i++) {
       enc_reflCoefs_[i] = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
           enc_reflCoefs_[i], ReflBeta, 15);
       enc_reflCoefs_[i] +=
           (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(refCs[i], ReflBetaComp, 15);
     }
     enc_Energy_ =
         (outEnergy >> 2) + (enc_Energy_ >> 1) + (enc_Energy_ >> 2);
   }

   if (enc_Energy_ < 1) {
     enc_Energy_ = 1;
   }

   if ((enc_msSinceSid_ > (enc_interval_ - 1)) || force_sid) {
     /* Search for best dbov value. */
     index = 0;
     for (i = 1; i < 93; i++) {
       /* Always round downwards. */
       if ((enc_Energy_ - WebRtcCng_kDbov[i]) > 0) {
         index = i;
         break;
       }
     }
     if ((i == 93) && (index == 0))
       index = 94;

     const size_t output_coefs = enc_nrOfCoefs_ + 1;
     output->AppendData(output_coefs, [&] (rtc::ArrayView<uint8_t> output) {
         output[0] = (uint8_t)index;

         /* Quantize coefficients with tweak for WebRtc implementation of
          * RFC3389. */
         if (enc_nrOfCoefs_ == WEBRTC_CNG_MAX_LPC_ORDER) {
           for (i = 0; i < enc_nrOfCoefs_; i++) {
             /* Q15 to Q7 with rounding. */
             output[i + 1] = ((enc_reflCoefs_[i] + 128) >> 8);
           }
         } else {
           for (i = 0; i < enc_nrOfCoefs_; i++) {
             /* Q15 to Q7 with rounding. */
             output[i + 1] = (127 + ((enc_reflCoefs_[i] + 128) >> 8));
           }
         }

         return output_coefs;
       });

     enc_msSinceSid_ =
         static_cast<int16_t>((1000 * num_samples) / enc_sampfreq_);
     return output_coefs;
   } else {
     enc_msSinceSid_ +=
         static_cast<int16_t>((1000 * num_samples) / enc_sampfreq_);
     return 0;
   }
 }

 namespace {
 /* Values in |k| are Q15, and |a| Q12. */
 void WebRtcCng_K2a16(int16_t* k, int useOrder, int16_t* a) {
   int16_t any[WEBRTC_SPL_MAX_LPC_ORDER + 1];
   int16_t* aptr;
   int16_t* aptr2;
   int16_t* anyptr;
   const int16_t* kptr;
   int m, i;

   kptr = k;
   *a = 4096; /* i.e., (Word16_MAX >> 3) + 1 */
   *any = *a;
   a[1] = (*k + 4) >> 3;
   for (m = 1; m < useOrder; m++) {
     kptr++;
     aptr = a;
     aptr++;
     aptr2 = &a[m];
     anyptr = any;
     anyptr++;

     any[m + 1] = (*kptr + 4) >> 3;
     for (i = 0; i < m; i++) {
       *anyptr++ =
           (*aptr++) +
           (int16_t)((((int32_t)(*aptr2--) * (int32_t)*kptr) + 16384) >> 15);
     }

     aptr = a;
     anyptr = any;
     for (i = 0; i < (m + 2); i++) {
       *aptr++ = *anyptr++;
     }
   }
 }

 }  // namespace

 }  // namespace webrtc
	/*
	* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "webrtc/modules/audio_coding/codecs/cng/webrtc_cng.h"

	#include <algorithm>

	#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
	#include "webrtc/rtc_base/safe_conversions.h"

	namespace webrtc {

	namespace {

	const size_t kCngMaxOutsizeOrder = 640;

	// TODO(ossu): Rename the left-over WebRtcCng according to style guide.
	void WebRtcCng_K2a16(int16_t* k, int useOrder, int16_t* a);

	const int32_t WebRtcCng_kDbov[94] = {
	1081109975, 858756178, 682134279, 541838517, 430397633, 341876992,
	271562548, 215709799, 171344384, 136103682, 108110997, 85875618,
	68213428, 54183852, 43039763, 34187699, 27156255, 21570980,
	17134438, 13610368, 10811100, 8587562, 6821343, 5418385,
	4303976, 3418770, 2715625, 2157098, 1713444, 1361037,
	1081110, 858756, 682134, 541839, 430398, 341877,
	271563, 215710, 171344, 136104, 108111, 85876,
	68213, 54184, 43040, 34188, 27156, 21571,
	17134, 13610, 10811, 8588, 6821, 5418,
	4304, 3419, 2716, 2157, 1713, 1361,
	1081, 859, 682, 542, 430, 342,
	272, 216, 171, 136, 108, 86,
	68, 54, 43, 34, 27, 22,
	17, 14, 11, 9, 7, 5,
	4, 3, 3, 2, 2, 1,
	1, 1, 1, 1
	};

	const int16_t WebRtcCng_kCorrWindow[WEBRTC_CNG_MAX_LPC_ORDER] = {
	32702, 32636, 32570, 32505, 32439, 32374,
	32309, 32244, 32179, 32114, 32049, 31985
	};

	} // namespace

	ComfortNoiseDecoder::ComfortNoiseDecoder() {
	/* Needed to get the right function pointers in SPLIB. */
	WebRtcSpl_Init();
	Reset();
	}

	void ComfortNoiseDecoder::Reset() {
	dec_seed_ = 7777; /* For debugging only. */
	dec_target_energy_ = 0;
	dec_used_energy_ = 0;
	for (auto& c : dec_target_reflCoefs_)
	c = 0;
	for (auto& c : dec_used_reflCoefs_)
	c = 0;
	for (auto& c : dec_filtstate_)
	c = 0;
	for (auto& c : dec_filtstateLow_)
	c = 0;
	dec_order_ = 5;
	dec_target_scale_factor_ = 0;
	dec_used_scale_factor_ = 0;
	}

	void ComfortNoiseDecoder::UpdateSid(rtc::ArrayView<const uint8_t> sid) {
	int16_t refCs[WEBRTC_CNG_MAX_LPC_ORDER];
	int32_t targetEnergy;
	size_t length = sid.size();
	/* Throw away reflection coefficients of higher order than we can handle. */
	if (length > (WEBRTC_CNG_MAX_LPC_ORDER + 1))
	length = WEBRTC_CNG_MAX_LPC_ORDER + 1;

	dec_order_ = static_cast<uint16_t>(length - 1);

	uint8_t sid0 = std::min<uint8_t>(sid[0], 93);
	targetEnergy = WebRtcCng_kDbov[sid0];
	/* Take down target energy to 75%. */
	targetEnergy = targetEnergy >> 1;
	targetEnergy += targetEnergy >> 2;

	dec_target_energy_ = targetEnergy;

	/* Reconstruct coeffs with tweak for WebRtc implementation of RFC3389. */
	if (dec_order_ == WEBRTC_CNG_MAX_LPC_ORDER) {
	for (size_t i = 0; i < (dec_order_); i++) {
	refCs[i] = sid[i + 1] << 8; /* Q7 to Q15*/
	dec_target_reflCoefs_[i] = refCs[i];
	}
	} else {
	for (size_t i = 0; i < (dec_order_); i++) {
	refCs[i] = (sid[i + 1] - 127) << 8; /* Q7 to Q15. */
	dec_target_reflCoefs_[i] = refCs[i];
	}
	}

	for (size_t i = (dec_order_); i < WEBRTC_CNG_MAX_LPC_ORDER; i++) {
	refCs[i] = 0;
	dec_target_reflCoefs_[i] = refCs[i];
	}
	}

	bool ComfortNoiseDecoder::Generate(rtc::ArrayView<int16_t> out_data,
	bool new_period) {
	int16_t excitation[kCngMaxOutsizeOrder];
	int16_t low[kCngMaxOutsizeOrder];
	int16_t lpPoly[WEBRTC_CNG_MAX_LPC_ORDER + 1];
	int16_t ReflBetaStd = 26214; /* 0.8 in q15. */
	int16_t ReflBetaCompStd = 6553; /* 0.2 in q15. */
	int16_t ReflBetaNewP = 19661; /* 0.6 in q15. */
	int16_t ReflBetaCompNewP = 13107; /* 0.4 in q15. */
	int16_t Beta, BetaC; /* These are in Q15. */
	int32_t targetEnergy;
	int16_t En;
	int16_t temp16;
	const size_t num_samples = out_data.size();

	if (num_samples > kCngMaxOutsizeOrder) {
	return false;
	}

	if (new_period) {
	dec_used_scale_factor_ = dec_target_scale_factor_;
	Beta = ReflBetaNewP;
	BetaC = ReflBetaCompNewP;
	} else {
	Beta = ReflBetaStd;
	BetaC = ReflBetaCompStd;
	}

	/* Calculate new scale factor in Q13 */
	dec_used_scale_factor_ =
	rtc::checked_cast<int16_t>(
	WEBRTC_SPL_MUL_16_16_RSFT(dec_used_scale_factor_, Beta >> 2, 13) +
	WEBRTC_SPL_MUL_16_16_RSFT(dec_target_scale_factor_, BetaC >> 2, 13));

	dec_used_energy_ = dec_used_energy_ >> 1;
	dec_used_energy_ += dec_target_energy_ >> 1;

	/* Do the same for the reflection coeffs, albeit in Q15. */
	for (size_t i = 0; i < WEBRTC_CNG_MAX_LPC_ORDER; i++) {
	dec_used_reflCoefs_[i] = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
	dec_used_reflCoefs_[i], Beta, 15);
	dec_used_reflCoefs_[i] += (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
	dec_target_reflCoefs_[i], BetaC, 15);
	}

	/* Compute the polynomial coefficients. */
	WebRtcCng_K2a16(dec_used_reflCoefs_, WEBRTC_CNG_MAX_LPC_ORDER, lpPoly);


	targetEnergy = dec_used_energy_;

	/* Calculate scaling factor based on filter energy. */
	En = 8192; /* 1.0 in Q13. */
	for (size_t i = 0; i < (WEBRTC_CNG_MAX_LPC_ORDER); i++) {
	/* Floating point value for reference.
	E = 1.0 - (dec_used_reflCoefs_[i] / 32768.0)
	(dec_used_reflCoefs_[i] / 32768.0);
	*/

	/* Same in fixed point. */
	/* K(i).^2 in Q15. */
	temp16 = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
	dec_used_reflCoefs_[i], dec_used_reflCoefs_[i], 15);
	/* 1 - K(i).^2 in Q15. */
	temp16 = 0x7fff - temp16;
	En = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(En, temp16, 15);
	}

	/* float scaling= sqrt(E * dec_target_energy_ / (1 << 24)); */

	/* Calculate sqrt(En * target_energy / excitation energy) */
	targetEnergy = WebRtcSpl_Sqrt(dec_used_energy_);

	En = (int16_t) WebRtcSpl_Sqrt(En) << 6;
	En = (En * 3) >> 1; /* 1.5 estimates sqrt(2). */
	dec_used_scale_factor_ = (int16_t)((En * targetEnergy) >> 12);

	/* Generate excitation. */
	/* Excitation energy per sample is 2.^24 - Q13 N(0,1). */
	for (size_t i = 0; i < num_samples; i++) {
	excitation[i] = WebRtcSpl_RandN(&dec_seed_) >> 1;
	}

	/* Scale to correct energy. */
	WebRtcSpl_ScaleVector(excitation, excitation, dec_used_scale_factor_,
	num_samples, 13);

	/* \|lpPoly\| - Coefficients in Q12.
	* \|excitation\| - Speech samples.
	* \|nst->dec_filtstate\| - State preservation.
	* \|out_data\| - Filtered speech samples. */
	WebRtcSpl_FilterAR(lpPoly, WEBRTC_CNG_MAX_LPC_ORDER + 1, excitation,
	num_samples, dec_filtstate_, WEBRTC_CNG_MAX_LPC_ORDER,
	dec_filtstateLow_, WEBRTC_CNG_MAX_LPC_ORDER,
	out_data.data(), low, num_samples);

	return true;
	}

	ComfortNoiseEncoder::ComfortNoiseEncoder(int fs, int interval, int quality)
	: enc_nrOfCoefs_(quality),
	enc_sampfreq_(fs),
	enc_interval_(interval),
	enc_msSinceSid_(0),
	enc_Energy_(0),
	enc_reflCoefs_{0},
	enc_corrVector_{0},
	enc_seed_(7777) /* For debugging only. */ {
	RTC_CHECK_GT(quality, 0);
	RTC_CHECK_LE(quality, WEBRTC_CNG_MAX_LPC_ORDER);
	/* Needed to get the right function pointers in SPLIB. */
	WebRtcSpl_Init();
	}

	void ComfortNoiseEncoder::Reset(int fs, int interval, int quality) {
	RTC_CHECK_GT(quality, 0);
	RTC_CHECK_LE(quality, WEBRTC_CNG_MAX_LPC_ORDER);
	enc_nrOfCoefs_ = quality;
	enc_sampfreq_ = fs;
	enc_interval_ = interval;
	enc_msSinceSid_ = 0;
	enc_Energy_ = 0;
	for (auto& c : enc_reflCoefs_)
	c = 0;
	for (auto& c : enc_corrVector_)
	c = 0;
	enc_seed_ = 7777; /* For debugging only. */
	}

	size_t ComfortNoiseEncoder::Encode(rtc::ArrayView<const int16_t> speech,
	bool force_sid,
	rtc::Buffer* output) {
	int16_t arCoefs[WEBRTC_CNG_MAX_LPC_ORDER + 1];
	int32_t corrVector[WEBRTC_CNG_MAX_LPC_ORDER + 1];
	int16_t refCs[WEBRTC_CNG_MAX_LPC_ORDER + 1];
	int16_t hanningW[kCngMaxOutsizeOrder];
	int16_t ReflBeta = 19661; /* 0.6 in q15. */
	int16_t ReflBetaComp = 13107; /* 0.4 in q15. */
	int32_t outEnergy;
	int outShifts;
	size_t i;
	int stab;
	int acorrScale;
	size_t index;
	size_t ind, factor;
	int32_t* bptr;
	int32_t blo, bhi;
	int16_t negate;
	const int16_t* aptr;
	int16_t speechBuf[kCngMaxOutsizeOrder];

	const size_t num_samples = speech.size();
	RTC_CHECK_LE(num_samples, kCngMaxOutsizeOrder);

	for (i = 0; i < num_samples; i++) {
	speechBuf[i] = speech[i];
	}

	factor = num_samples;

	/* Calculate energy and a coefficients. */
	outEnergy = WebRtcSpl_Energy(speechBuf, num_samples, &outShifts);
	while (outShifts > 0) {
	/* We can only do 5 shifts without destroying accuracy in
	* division factor. */
	if (outShifts > 5) {
	outEnergy <<= (outShifts - 5);
	outShifts = 5;
	} else {
	factor /= 2;
	outShifts--;
	}
	}
	outEnergy = WebRtcSpl_DivW32W16(outEnergy, (int16_t)factor);

	if (outEnergy > 1) {
	/* Create Hanning Window. */
	WebRtcSpl_GetHanningWindow(hanningW, num_samples / 2);
	for (i = 0; i < (num_samples / 2); i++)
	hanningW[num_samples - i - 1] = hanningW[i];

	WebRtcSpl_ElementwiseVectorMult(speechBuf, hanningW, speechBuf, num_samples,
	14);

	WebRtcSpl_AutoCorrelation(speechBuf, num_samples, enc_nrOfCoefs_,
	corrVector, &acorrScale);

	if (*corrVector == 0)
	*corrVector = WEBRTC_SPL_WORD16_MAX;

	/* Adds the bandwidth expansion. */
	aptr = WebRtcCng_kCorrWindow;
	bptr = corrVector;

	/* (zzz) lpc16_1 = 17+1+820+2+2 = 842 (ordo2=700). */
	for (ind = 0; ind < enc_nrOfCoefs_; ind++) {
	/* The below code multiplies the 16 b corrWindow values (Q15) with
	* the 32 b corrvector (Q0) and shifts the result down 15 steps. */
	negate = *bptr < 0;
	if (negate)
	bptr = -bptr;

	blo = (int32_t) * aptr * (*bptr & 0xffff);
	bhi = ((blo >> 16) & 0xffff)
	+ ((int32_t)(aptr++) ((*bptr >> 16) & 0xffff));
	blo = (blo & 0xffff) \| ((bhi & 0xffff) << 16);

	*bptr = (((bhi >> 16) & 0x7fff) << 17) \| ((uint32_t) blo >> 15);
	if (negate)
	bptr = -bptr;
	bptr++;
	}
	/* End of bandwidth expansion. */

	stab = WebRtcSpl_LevinsonDurbin(corrVector, arCoefs, refCs,
	enc_nrOfCoefs_);

	if (!stab) {
	/* Disregard from this frame */
	return 0;
	}

	} else {
	for (i = 0; i < enc_nrOfCoefs_; i++)
	refCs[i] = 0;
	}

	if (force_sid) {
	/* Read instantaneous values instead of averaged. */
	for (i = 0; i < enc_nrOfCoefs_; i++)
	enc_reflCoefs_[i] = refCs[i];
	enc_Energy_ = outEnergy;
	} else {
	/* Average history with new values. */
	for (i = 0; i < enc_nrOfCoefs_; i++) {
	enc_reflCoefs_[i] = (int16_t) WEBRTC_SPL_MUL_16_16_RSFT(
	enc_reflCoefs_[i], ReflBeta, 15);
	enc_reflCoefs_[i] +=
	(int16_t) WEBRTC_SPL_MUL_16_16_RSFT(refCs[i], ReflBetaComp, 15);
	}
	enc_Energy_ =
	(outEnergy >> 2) + (enc_Energy_ >> 1) + (enc_Energy_ >> 2);
	}

	if (enc_Energy_ < 1) {
	enc_Energy_ = 1;
	}

	if ((enc_msSinceSid_ > (enc_interval_ - 1)) \|\| force_sid) {
	/* Search for best dbov value. */
	index = 0;
	for (i = 1; i < 93; i++) {
	/* Always round downwards. */
	if ((enc_Energy_ - WebRtcCng_kDbov[i]) > 0) {
	index = i;
	break;
	}
	}
	if ((i == 93) && (index == 0))
	index = 94;

	const size_t output_coefs = enc_nrOfCoefs_ + 1;
	output->AppendData(output_coefs, [&] (rtc::ArrayView<uint8_t> output) {
	output[0] = (uint8_t)index;

	/* Quantize coefficients with tweak for WebRtc implementation of
	* RFC3389. */
	if (enc_nrOfCoefs_ == WEBRTC_CNG_MAX_LPC_ORDER) {
	for (i = 0; i < enc_nrOfCoefs_; i++) {
	/* Q15 to Q7 with rounding. */
	output[i + 1] = ((enc_reflCoefs_[i] + 128) >> 8);
	}
	} else {
	for (i = 0; i < enc_nrOfCoefs_; i++) {
	/* Q15 to Q7 with rounding. */
	output[i + 1] = (127 + ((enc_reflCoefs_[i] + 128) >> 8));
	}
	}

	return output_coefs;
	});

	enc_msSinceSid_ =
	static_cast<int16_t>((1000 * num_samples) / enc_sampfreq_);
	return output_coefs;
	} else {
	enc_msSinceSid_ +=
	static_cast<int16_t>((1000 * num_samples) / enc_sampfreq_);
	return 0;
	}
	}

	namespace {
	/* Values in \|k\| are Q15, and \|a\| Q12. */
	void WebRtcCng_K2a16(int16_t* k, int useOrder, int16_t* a) {
	int16_t any[WEBRTC_SPL_MAX_LPC_ORDER + 1];
	int16_t* aptr;
	int16_t* aptr2;
	int16_t* anyptr;
	const int16_t* kptr;
	int m, i;

	kptr = k;
	a = 4096; / i.e., (Word16_MAX >> 3) + 1 */
	any = a;
	a[1] = (*k + 4) >> 3;
	for (m = 1; m < useOrder; m++) {
	kptr++;
	aptr = a;
	aptr++;
	aptr2 = &a[m];
	anyptr = any;
	anyptr++;

	any[m + 1] = (*kptr + 4) >> 3;
	for (i = 0; i < m; i++) {
	*anyptr++ =
	(*aptr++) +
	(int16_t)((((int32_t)(aptr2--) (int32_t)*kptr) + 16384) >> 15);
	}

	aptr = a;
	anyptr = any;
	for (i = 0; i < (m + 2); i++) {
	aptr++ = anyptr++;
	}
	}
	}

	} // namespace

	} // namespace webrtc