libavcodec/lsp.c

   1 /*
   2  * LSP routines for ACELP-based codecs
   3  *
   4  * Copyright (c) 2007 Reynaldo H. Verdejo Pinochet (QCELP decoder)
   5  * Copyright (c) 2008 Vladimir Voroshilov
   6  *
   7  * This file is part of FFmpeg.
   8  *
   9  * FFmpeg is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * FFmpeg is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with FFmpeg; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #include <inttypes.h>
  25
  26 #include "avcodec.h"
  27 #define FRAC_BITS 14
  28 #include "mathops.h"
  29 #include "lsp.h"
  30 #include "celp_math.h"
  31
  32 void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max, int lp_order)
  33 {
  34     int i, j;
  35
  36     /* sort lsfq in ascending order. float bubble agorithm,
  37        O(n) if data already sorted, O(n^2) - otherwise */
  38     for(i=0; i<lp_order-1; i++)
  39         for(j=i; j>=0 && lsfq[j] > lsfq[j+1]; j--)
  40             FFSWAP(int16_t, lsfq[j], lsfq[j+1]);
  41
  42     for(i=0; i<lp_order; i++)
  43     {
  44         lsfq[i] = FFMAX(lsfq[i], lsfq_min);
  45         lsfq_min = lsfq[i] + lsfq_min_distance;
  46     }
  47     lsfq[lp_order-1] = FFMIN(lsfq[lp_order-1], lsfq_max);//Is warning required ?
  48 }
  49
  50 void ff_set_min_dist_lsf(float *lsf, double min_spacing, int size)
  51 {
  52     int i;
  53     float prev = 0.0;
  54     for (i = 0; i < size; i++)
  55         prev = lsf[i] = FFMAX(lsf[i], prev + min_spacing);
  56 }
  57
  58 void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order)
  59 {
  60     int i;
  61
  62     /* Convert LSF to LSP, lsp=cos(lsf) */
  63     for(i=0; i<lp_order; i++)
  64         // 20861 = 2.0 / PI in (0.15)
  65         lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14)
  66 }
  67
  68 /**
  69  * \brief decodes polynomial coefficients from LSP
  70  * \param f [out] decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff)
  71  * \param lsp LSP coefficients (-0x8000 <= (0.15) <= 0x7fff)
  72  */
  73 static void lsp2poly(int* f, const int16_t* lsp, int lp_half_order)
  74 {
  75     int i, j;
  76
  77     f[0] = 0x400000;          // 1.0 in (3.22)
  78     f[1] = -lsp[0] << 8;      // *2 and (0.15) -> (3.22)
  79
  80     for(i=2; i<=lp_half_order; i++)
  81     {
  82         f[i] = f[i-2];
  83         for(j=i; j>1; j--)
  84             f[j] -= MULL(f[j-1], lsp[2*i-2], FRAC_BITS) - f[j-2];
  85
  86         f[1] -= lsp[2*i-2] << 8;
  87     }
  88 }
  89
  90 void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
  91 {
  92     int i;
  93     int f1[lp_half_order+1]; // (3.22)
  94     int f2[lp_half_order+1]; // (3.22)
  95
  96     lsp2poly(f1, lsp  , lp_half_order);
  97     lsp2poly(f2, lsp+1, lp_half_order);
  98
  99     /* 3.2.6 of G.729, Equations 25 and  26*/
 100     lp[0] = 4096;
 101     for(i=1; i<lp_half_order+1; i++)
 102     {
 103         int ff1 = f1[i] + f1[i-1]; // (3.22)
 104         int ff2 = f2[i] - f2[i-1]; // (3.22)
 105
 106         ff1 += 1 << 10; // for rounding
 107         lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 108         lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 109     }
 110 }
 111
 112 void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd, const int16_t* lsp_prev, int lp_order)
 113 {
 114     int16_t lsp_1st[lp_order]; // (0.15)
 115     int i;
 116
 117     /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
 118     for(i=0; i<lp_order; i++)
 119 #ifdef G729_BITEXACT
 120         lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1);
 121 #else
 122         lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
 123 #endif
 124
 125     ff_acelp_lsp2lpc(lp_1st, lsp_1st, lp_order >> 1);
 126
 127     /* LSP values for second subframe (3.2.5 of G.729)*/
 128     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
 129 }
 130
 131 /**
 132  * Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients
 133  * needed for LSP to LPC conversion.
 134  * We only need to calculate the 6 first elements of the polynomial.
 135  *
 136  * @param lsp line spectral pairs in cosine domain
 137  * @param f [out] polynomial input/output as a vector
 138  *
 139  * TIA/EIA/IS-733 2.4.3.3.5-1/2
 140  */
 141 static void lsp2polyf(const double *lsp, double *f, int lp_half_order)
 142 {
 143     int i, j;
 144
 145     f[0] = 1.0;
 146     f[1] = -2 * lsp[0];
 147     lsp -= 2;
 148     for(i=2; i<=lp_half_order; i++)
 149     {
 150         double val = -2 * lsp[2*i];
 151         f[i] = val * f[i-1] + 2*f[i-2];
 152         for(j=i-1; j>1; j--)
 153             f[j] += f[j-1] * val + f[j-2];
 154         f[1] += val;
 155     }
 156 }
 157
 158 void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order)
 159 {
 160     double pa[MAX_LP_HALF_ORDER+1], qa[MAX_LP_HALF_ORDER+1];
 161     float *lpc2 = lpc + (lp_half_order << 1) - 1;
 162
 163     assert(lp_half_order <= MAX_LP_HALF_ORDER);
 164
 165     lsp2polyf(lsp,     pa, lp_half_order);
 166     lsp2polyf(lsp + 1, qa, lp_half_order);
 167
 168     while (lp_half_order--) {
 169         double paf = pa[lp_half_order+1] + pa[lp_half_order];
 170         double qaf = qa[lp_half_order+1] - qa[lp_half_order];
 171
 172         lpc [ lp_half_order] = 0.5*(paf+qaf);
 173         lpc2[-lp_half_order] = 0.5*(paf-qaf);
 174     }
 175 }