libavcodec/lpc.c - manifest_repos/ffmpeg - Git at Google

 /*
  * LPC utility code
  * Copyright (c) 2006  Justin Ruggles <justin.ruggles@gmail.com>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 #include "libavutil/common.h"
 #include "libavutil/lls.h"

 #define LPC_USE_DOUBLE
 #include "lpc.h"
 #include "libavutil/avassert.h"


 /**
  * Apply Welch window function to audio block
  */
 static void lpc_apply_welch_window_c(const int32_t *data, int len,
                                      double *w_data)
 {
     int i, n2;
     double w;
     double c;

     n2 = (len >> 1);
     c = 2.0 / (len - 1.0);

     if (len & 1) {
         for(i=0; i<n2; i++) {
             w = c - i - 1.0;
             w = 1.0 - (w * w);
             w_data[i] = data[i] * w;
             w_data[len-1-i] = data[len-1-i] * w;
         }
         return;
     }

     w_data+=n2;
       data+=n2;
     for(i=0; i<n2; i++) {
         w = c - n2 + i;
         w = 1.0 - (w * w);
         w_data[-i-1] = data[-i-1] * w;
         w_data[+i  ] = data[+i  ] * w;
     }
 }

 /**
  * Calculate autocorrelation data from audio samples
  * A Welch window function is applied before calculation.
  */
 static void lpc_compute_autocorr_c(const double *data, int len, int lag,
                                    double *autoc)
 {
     int i, j;

     for(j=0; j<lag; j+=2){
         double sum0 = 1.0, sum1 = 1.0;
         for(i=j; i<len; i++){
             sum0 += data[i] * data[i-j];
             sum1 += data[i] * data[i-j-1];
         }
         autoc[j  ] = sum0;
         autoc[j+1] = sum1;
     }

     if(j==lag){
         double sum = 1.0;
         for(i=j-1; i<len; i+=2){
             sum += data[i  ] * data[i-j  ]
                  + data[i+1] * data[i-j+1];
         }
         autoc[j] = sum;
     }
 }

 /**
  * Quantize LPC coefficients
  */
 static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
                                int32_t *lpc_out, int *shift, int min_shift,
                                int max_shift, int zero_shift)
 {
     int i;
     double cmax, error;
     int32_t qmax;
     int sh;

     /* define maximum levels */
     qmax = (1 << (precision - 1)) - 1;

     /* find maximum coefficient value */
     cmax = 0.0;
     for(i=0; i<order; i++) {
         cmax= FFMAX(cmax, fabs(lpc_in[i]));
     }

     /* if maximum value quantizes to zero, return all zeros */
     if(cmax * (1 << max_shift) < 1.0) {
         *shift = zero_shift;
         memset(lpc_out, 0, sizeof(int32_t) * order);
         return;
     }

     /* calculate level shift which scales max coeff to available bits */
     sh = max_shift;
     while((cmax * (1 << sh) > qmax) && (sh > min_shift)) {
         sh--;
     }

     /* since negative shift values are unsupported in decoder, scale down
        coefficients instead */
     if(sh == 0 && cmax > qmax) {
         double scale = ((double)qmax) / cmax;
         for(i=0; i<order; i++) {
             lpc_in[i] *= scale;
         }
     }

     /* output quantized coefficients and level shift */
     error=0;
     for(i=0; i<order; i++) {
         error -= lpc_in[i] * (1 << sh);
         lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
         error -= lpc_out[i];
     }
     *shift = sh;
 }

 static int estimate_best_order(double *ref, int min_order, int max_order)
 {
     int i, est;

     est = min_order;
     for(i=max_order-1; i>=min_order-1; i--) {
         if(ref[i] > 0.10) {
             est = i+1;
             break;
         }
     }
     return est;
 }

 int ff_lpc_calc_ref_coefs(LPCContext *s,
                           const int32_t *samples, int order, double *ref)
 {
     double autoc[MAX_LPC_ORDER + 1];

     s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples);
     s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc);
     compute_ref_coefs(autoc, order, ref, NULL);

     return order;
 }

 double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
                                int order, double *ref)
 {
     int i;
     double signal = 0.0f, avg_err = 0.0f;
     double autoc[MAX_LPC_ORDER+1] = {0}, error[MAX_LPC_ORDER+1] = {0};
     const double a = 0.5f, b = 1.0f - a;

     /* Apply windowing */
     for (i = 0; i <= len / 2; i++) {
         double weight = a - b*cos((2*M_PI*i)/(len - 1));
         s->windowed_samples[i] = weight*samples[i];
         s->windowed_samples[len-1-i] = weight*samples[len-1-i];
     }

     s->lpc_compute_autocorr(s->windowed_samples, len, order, autoc);
     signal = autoc[0];
     compute_ref_coefs(autoc, order, ref, error);
     for (i = 0; i < order; i++)
         avg_err = (avg_err + error[i])/2.0f;
     return signal/avg_err;
 }

 /**
  * Calculate LPC coefficients for multiple orders
  *
  * @param lpc_type LPC method for determining coefficients,
  *                 see #FFLPCType for details
  */
 int ff_lpc_calc_coefs(LPCContext *s,
                       const int32_t *samples, int blocksize, int min_order,
                       int max_order, int precision,
                       int32_t coefs[][MAX_LPC_ORDER], int *shift,
                       enum FFLPCType lpc_type, int lpc_passes,
                       int omethod, int min_shift, int max_shift, int zero_shift)
 {
     double autoc[MAX_LPC_ORDER+1];
     double ref[MAX_LPC_ORDER] = { 0 };
     double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
     int i, j, pass = 0;
     int opt_order;

     av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
            lpc_type > FF_LPC_TYPE_FIXED);
     av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY || lpc_type == FF_LPC_TYPE_LEVINSON);

     /* reinit LPC context if parameters have changed */
     if (blocksize != s->blocksize || max_order != s->max_order ||
         lpc_type  != s->lpc_type) {
         ff_lpc_end(s);
         ff_lpc_init(s, blocksize, max_order, lpc_type);
     }

     if(lpc_passes <= 0)
         lpc_passes = 2;

     if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) {
         s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);

         s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);

         compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);

         for(i=0; i<max_order; i++)
             ref[i] = fabs(lpc[i][i]);

         pass++;
     }

     if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
         LLSModel *m = s->lls_models;
         LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]);
         double av_uninit(weight);
         memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var));

         for(j=0; j<max_order; j++)
             m[0].coeff[max_order-1][j] = -lpc[max_order-1][j];

         for(; pass<lpc_passes; pass++){
             avpriv_init_lls(&m[pass&1], max_order);

             weight=0;
             for(i=max_order; i<blocksize; i++){
                 for(j=0; j<=max_order; j++)
                     var[j]= samples[i-j];

                 if(pass){
                     double eval, inv, rinv;
                     eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
                     eval= (512>>pass) + fabs(eval - var[0]);
                     inv = 1/eval;
                     rinv = sqrt(inv);
                     for(j=0; j<=max_order; j++)
                         var[j] *= rinv;
                     weight += inv;
                 }else
                     weight++;

                 m[pass&1].update_lls(&m[pass&1], var);
             }
             avpriv_solve_lls(&m[pass&1], 0.001, 0);
         }

         for(i=0; i<max_order; i++){
             for(j=0; j<max_order; j++)
                 lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
             ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
         }
         for(i=max_order-1; i>0; i--)
             ref[i] = ref[i-1] - ref[i];
     }

     opt_order = max_order;

     if(omethod == ORDER_METHOD_EST) {
         opt_order = estimate_best_order(ref, min_order, max_order);
         i = opt_order-1;
         quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
                            min_shift, max_shift, zero_shift);
     } else {
         for(i=min_order-1; i<max_order; i++) {
             quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
                                min_shift, max_shift, zero_shift);
         }
     }

     return opt_order;
 }

 av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
                         enum FFLPCType lpc_type)
 {
     s->blocksize = blocksize;
     s->max_order = max_order;
     s->lpc_type  = lpc_type;

     s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) *
                                     sizeof(*s->windowed_samples));
     if (!s->windowed_buffer)
         return AVERROR(ENOMEM);
     s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4);

     s->lpc_apply_welch_window = lpc_apply_welch_window_c;
     s->lpc_compute_autocorr   = lpc_compute_autocorr_c;

     if (ARCH_X86)
         ff_lpc_init_x86(s);

     return 0;
 }

 av_cold void ff_lpc_end(LPCContext *s)
 {
     av_freep(&s->windowed_buffer);
 }
	/*
	* LPC utility code
	* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#include "libavutil/common.h"
	#include "libavutil/lls.h"

	#define LPC_USE_DOUBLE
	#include "lpc.h"
	#include "libavutil/avassert.h"


	/**
	* Apply Welch window function to audio block
	*/
	static void lpc_apply_welch_window_c(const int32_t *data, int len,
	double *w_data)
	{
	int i, n2;
	double w;
	double c;

	n2 = (len >> 1);
	c = 2.0 / (len - 1.0);

	if (len & 1) {
	for(i=0; i<n2; i++) {
	w = c - i - 1.0;
	w = 1.0 - (w * w);
	w_data[i] = data[i] * w;
	w_data[len-1-i] = data[len-1-i] * w;
	}
	return;
	}

	w_data+=n2;
	data+=n2;
	for(i=0; i<n2; i++) {
	w = c - n2 + i;
	w = 1.0 - (w * w);
	w_data[-i-1] = data[-i-1] * w;
	w_data[+i ] = data[+i ] * w;
	}
	}

	/**
	* Calculate autocorrelation data from audio samples
	* A Welch window function is applied before calculation.
	*/
	static void lpc_compute_autocorr_c(const double *data, int len, int lag,
	double *autoc)
	{
	int i, j;

	for(j=0; j<lag; j+=2){
	double sum0 = 1.0, sum1 = 1.0;
	for(i=j; i<len; i++){
	sum0 += data[i] * data[i-j];
	sum1 += data[i] * data[i-j-1];
	}
	autoc[j ] = sum0;
	autoc[j+1] = sum1;
	}

	if(j==lag){
	double sum = 1.0;
	for(i=j-1; i<len; i+=2){
	sum += data[i ] * data[i-j ]
	+ data[i+1] * data[i-j+1];
	}
	autoc[j] = sum;
	}
	}

	/**
	* Quantize LPC coefficients
	*/
	static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
	int32_t lpc_out, int shift, int min_shift,
	int max_shift, int zero_shift)
	{
	int i;
	double cmax, error;
	int32_t qmax;
	int sh;

	/* define maximum levels */
	qmax = (1 << (precision - 1)) - 1;

	/* find maximum coefficient value */
	cmax = 0.0;
	for(i=0; i<order; i++) {
	cmax= FFMAX(cmax, fabs(lpc_in[i]));
	}

	/* if maximum value quantizes to zero, return all zeros */
	if(cmax * (1 << max_shift) < 1.0) {
	*shift = zero_shift;
	memset(lpc_out, 0, sizeof(int32_t) * order);
	return;
	}

	/* calculate level shift which scales max coeff to available bits */
	sh = max_shift;
	while((cmax * (1 << sh) > qmax) && (sh > min_shift)) {
	sh--;
	}

	/* since negative shift values are unsupported in decoder, scale down
	coefficients instead */
	if(sh == 0 && cmax > qmax) {
	double scale = ((double)qmax) / cmax;
	for(i=0; i<order; i++) {
	lpc_in[i] *= scale;
	}
	}

	/* output quantized coefficients and level shift */
	error=0;
	for(i=0; i<order; i++) {
	error -= lpc_in[i] * (1 << sh);
	lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
	error -= lpc_out[i];
	}
	*shift = sh;
	}

	static int estimate_best_order(double *ref, int min_order, int max_order)
	{
	int i, est;

	est = min_order;
	for(i=max_order-1; i>=min_order-1; i--) {
	if(ref[i] > 0.10) {
	est = i+1;
	break;
	}
	}
	return est;
	}

	int ff_lpc_calc_ref_coefs(LPCContext *s,
	const int32_t samples, int order, double ref)
	{
	double autoc[MAX_LPC_ORDER + 1];

	s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples);
	s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc);
	compute_ref_coefs(autoc, order, ref, NULL);

	return order;
	}

	double ff_lpc_calc_ref_coefs_f(LPCContext s, const float samples, int len,
	int order, double *ref)
	{
	int i;
	double signal = 0.0f, avg_err = 0.0f;
	double autoc[MAX_LPC_ORDER+1] = {0}, error[MAX_LPC_ORDER+1] = {0};
	const double a = 0.5f, b = 1.0f - a;

	/* Apply windowing */
	for (i = 0; i <= len / 2; i++) {
	double weight = a - bcos((2M_PI*i)/(len - 1));
	s->windowed_samples[i] = weight*samples[i];
	s->windowed_samples[len-1-i] = weight*samples[len-1-i];
	}

	s->lpc_compute_autocorr(s->windowed_samples, len, order, autoc);
	signal = autoc[0];
	compute_ref_coefs(autoc, order, ref, error);
	for (i = 0; i < order; i++)
	avg_err = (avg_err + error[i])/2.0f;
	return signal/avg_err;
	}

	/**
	* Calculate LPC coefficients for multiple orders
	*
	* @param lpc_type LPC method for determining coefficients,
	* see #FFLPCType for details
	*/
	int ff_lpc_calc_coefs(LPCContext *s,
	const int32_t *samples, int blocksize, int min_order,
	int max_order, int precision,
	int32_t coefs[][MAX_LPC_ORDER], int *shift,
	enum FFLPCType lpc_type, int lpc_passes,
	int omethod, int min_shift, int max_shift, int zero_shift)
	{
	double autoc[MAX_LPC_ORDER+1];
	double ref[MAX_LPC_ORDER] = { 0 };
	double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
	int i, j, pass = 0;
	int opt_order;

	av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
	lpc_type > FF_LPC_TYPE_FIXED);
	av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY \|\| lpc_type == FF_LPC_TYPE_LEVINSON);

	/* reinit LPC context if parameters have changed */
	if (blocksize != s->blocksize \|\| max_order != s->max_order \|\|
	lpc_type != s->lpc_type) {
	ff_lpc_end(s);
	ff_lpc_init(s, blocksize, max_order, lpc_type);
	}

	if(lpc_passes <= 0)
	lpc_passes = 2;

	if (lpc_type == FF_LPC_TYPE_LEVINSON \|\| (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) {
	s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);

	s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);

	compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);

	for(i=0; i<max_order; i++)
	ref[i] = fabs(lpc[i][i]);

	pass++;
	}

	if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
	LLSModel *m = s->lls_models;
	LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]);
	double av_uninit(weight);
	memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)sizeof(var));

	for(j=0; j<max_order; j++)
	m[0].coeff[max_order-1][j] = -lpc[max_order-1][j];

	for(; pass<lpc_passes; pass++){
	avpriv_init_lls(&m[pass&1], max_order);

	weight=0;
	for(i=max_order; i<blocksize; i++){
	for(j=0; j<=max_order; j++)
	var[j]= samples[i-j];

	if(pass){
	double eval, inv, rinv;
	eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
	eval= (512>>pass) + fabs(eval - var[0]);
	inv = 1/eval;
	rinv = sqrt(inv);
	for(j=0; j<=max_order; j++)
	var[j] *= rinv;
	weight += inv;
	}else
	weight++;

	m[pass&1].update_lls(&m[pass&1], var);
	}
	avpriv_solve_lls(&m[pass&1], 0.001, 0);
	}

	for(i=0; i<max_order; i++){
	for(j=0; j<max_order; j++)
	lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
	ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
	}
	for(i=max_order-1; i>0; i--)
	ref[i] = ref[i-1] - ref[i];
	}

	opt_order = max_order;

	if(omethod == ORDER_METHOD_EST) {
	opt_order = estimate_best_order(ref, min_order, max_order);
	i = opt_order-1;
	quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
	min_shift, max_shift, zero_shift);
	} else {
	for(i=min_order-1; i<max_order; i++) {
	quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i],
	min_shift, max_shift, zero_shift);
	}
	}

	return opt_order;
	}

	av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
	enum FFLPCType lpc_type)
	{
	s->blocksize = blocksize;
	s->max_order = max_order;
	s->lpc_type = lpc_type;

	s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) *
	sizeof(*s->windowed_samples));
	if (!s->windowed_buffer)
	return AVERROR(ENOMEM);
	s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4);

	s->lpc_apply_welch_window = lpc_apply_welch_window_c;
	s->lpc_compute_autocorr = lpc_compute_autocorr_c;

	if (ARCH_X86)
	ff_lpc_init_x86(s);

	return 0;
	}

	av_cold void ff_lpc_end(LPCContext *s)
	{
	av_freep(&s->windowed_buffer);
	}