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 Libav.
   8  *
   9  * Libav 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  * Libav 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 Libav; 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
  31 void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max, int lp_order)
  32 {
  33     int i, j;
  34
  35     /* sort lsfq in ascending order. float bubble agorithm,
  36        O(n) if data already sorted, O(n^2) - otherwise */
  37     for(i=0; i<lp_order-1; i++)
  38         for(j=i; j>=0 && lsfq[j] > lsfq[j+1]; j--)
  39             FFSWAP(int16_t, lsfq[j], lsfq[j+1]);
  40
  41     for(i=0; i<lp_order; i++)
  42     {
  43         lsfq[i] = FFMAX(lsfq[i], lsfq_min);
  44         lsfq_min = lsfq[i] + lsfq_min_distance;
  45     }
  46     lsfq[lp_order-1] = FFMIN(lsfq[lp_order-1], lsfq_max);//Is warning required ?
  47 }
  48
  49 void ff_set_min_dist_lsf(float *lsf, double min_spacing, int size)
  50 {
  51     int i;
  52     float prev = 0.0;
  53     for (i = 0; i < size; i++)
  54         prev = lsf[i] = FFMAX(lsf[i], prev + min_spacing);
  55 }
  56
  57
  58 /* Cosine table: base_cos[i] = (1 << 15) * cos(i * PI / 64) */
  59 static const int16_t tab_cos[65] =
  60 {
  61   32767,  32738,  32617,  32421,  32145,  31793,  31364,  30860,
  62   30280,  29629,  28905,  28113,  27252,  26326,  25336,  24285,
  63   23176,  22011,  20793,  19525,  18210,  16851,  15451,  14014,
  64   12543,  11043,   9515,   7965,   6395,   4810,   3214,   1609,
  65       1,  -1607,  -3211,  -4808,  -6393,  -7962,  -9513, -11040,
  66  -12541, -14012, -15449, -16848, -18207, -19523, -20791, -22009,
  67  -23174, -24283, -25334, -26324, -27250, -28111, -28904, -29627,
  68  -30279, -30858, -31363, -31792, -32144, -32419, -32616, -32736, -32768,
  69 };
  70
  71 static int16_t ff_cos(uint16_t arg)
  72 {
  73     uint8_t offset= arg;
  74     uint8_t ind = arg >> 8;
  75
  76     assert(arg <= 0x3fff);
  77
  78     return tab_cos[ind] + (offset * (tab_cos[ind+1] - tab_cos[ind]) >> 8);
  79 }
  80
  81 void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order)
  82 {
  83     int i;
  84
  85     /* Convert LSF to LSP, lsp=cos(lsf) */
  86     for(i=0; i<lp_order; i++)
  87         // 20861 = 2.0 / PI in (0.15)
  88         lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14)
  89 }
  90
  91 void ff_acelp_lsf2lspd(double *lsp, const float *lsf, int lp_order)
  92 {
  93     int i;
  94
  95     for(i = 0; i < lp_order; i++)
  96         lsp[i] = cos(2.0 * M_PI * lsf[i]);
  97 }
  98
  99 /**
 100  * @brief decodes polynomial coefficients from LSP
 101  * @param[out] f decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff)
 102  * @param lsp LSP coefficients (-0x8000 <= (0.15) <= 0x7fff)
 103  */
 104 static void lsp2poly(int* f, const int16_t* lsp, int lp_half_order)
 105 {
 106     int i, j;
 107
 108     f[0] = 0x400000;          // 1.0 in (3.22)
 109     f[1] = -lsp[0] << 8;      // *2 and (0.15) -> (3.22)
 110
 111     for(i=2; i<=lp_half_order; i++)
 112     {
 113         f[i] = f[i-2];
 114         for(j=i; j>1; j--)
 115             f[j] -= MULL(f[j-1], lsp[2*i-2], FRAC_BITS) - f[j-2];
 116
 117         f[1] -= lsp[2*i-2] << 8;
 118     }
 119 }
 120
 121 void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
 122 {
 123     int i;
 124     int f1[MAX_LP_HALF_ORDER+1]; // (3.22)
 125     int f2[MAX_LP_HALF_ORDER+1]; // (3.22)
 126
 127     lsp2poly(f1, lsp  , lp_half_order);
 128     lsp2poly(f2, lsp+1, lp_half_order);
 129
 130     /* 3.2.6 of G.729, Equations 25 and  26*/
 131     lp[0] = 4096;
 132     for(i=1; i<lp_half_order+1; i++)
 133     {
 134         int ff1 = f1[i] + f1[i-1]; // (3.22)
 135         int ff2 = f2[i] - f2[i-1]; // (3.22)
 136
 137         ff1 += 1 << 10; // for rounding
 138         lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 139         lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 140     }
 141 }
 142
 143 void ff_amrwb_lsp2lpc(const double *lsp, float *lp, int lp_order)
 144 {
 145     int lp_half_order = lp_order >> 1;
 146     double buf[MAX_LP_HALF_ORDER + 1];
 147     double pa[MAX_LP_HALF_ORDER + 1];
 148     double *qa = buf + 1;
 149     int i,j;
 150
 151     qa[-1] = 0.0;
 152
 153     ff_lsp2polyf(lsp    , pa, lp_half_order    );
 154     ff_lsp2polyf(lsp + 1, qa, lp_half_order - 1);
 155
 156     for (i = 1, j = lp_order - 1; i < lp_half_order; i++, j--) {
 157         double paf =  pa[i]            * (1 + lsp[lp_order - 1]);
 158         double qaf = (qa[i] - qa[i-2]) * (1 - lsp[lp_order - 1]);
 159         lp[i-1]  = (paf + qaf) * 0.5;
 160         lp[j-1]  = (paf - qaf) * 0.5;
 161     }
 162
 163     lp[lp_half_order - 1] = (1.0 + lsp[lp_order - 1]) *
 164         pa[lp_half_order] * 0.5;
 165
 166     lp[lp_order - 1] = lsp[lp_order - 1];
 167 }
 168
 169 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)
 170 {
 171     int16_t lsp_1st[MAX_LP_ORDER]; // (0.15)
 172     int i;
 173
 174     /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
 175     for(i=0; i<lp_order; i++)
 176         lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
 177
 178     ff_acelp_lsp2lpc(lp_1st, lsp_1st, lp_order >> 1);
 179
 180     /* LSP values for second subframe (3.2.5 of G.729)*/
 181     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
 182 }
 183
 184 void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order)
 185 {
 186     int i, j;
 187
 188     f[0] = 1.0;
 189     f[1] = -2 * lsp[0];
 190     lsp -= 2;
 191     for(i=2; i<=lp_half_order; i++)
 192     {
 193         double val = -2 * lsp[2*i];
 194         f[i] = val * f[i-1] + 2*f[i-2];
 195         for(j=i-1; j>1; j--)
 196             f[j] += f[j-1] * val + f[j-2];
 197         f[1] += val;
 198     }
 199 }
 200
 201 void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order)
 202 {
 203     double pa[MAX_LP_HALF_ORDER+1], qa[MAX_LP_HALF_ORDER+1];
 204     float *lpc2 = lpc + (lp_half_order << 1) - 1;
 205
 206     assert(lp_half_order <= MAX_LP_HALF_ORDER);
 207
 208     ff_lsp2polyf(lsp,     pa, lp_half_order);
 209     ff_lsp2polyf(lsp + 1, qa, lp_half_order);
 210
 211     while (lp_half_order--) {
 212         double paf = pa[lp_half_order+1] + pa[lp_half_order];
 213         double qaf = qa[lp_half_order+1] - qa[lp_half_order];
 214
 215         lpc [ lp_half_order] = 0.5*(paf+qaf);
 216         lpc2[-lp_half_order] = 0.5*(paf-qaf);
 217     }
 218 }
 219
 220 void ff_sort_nearly_sorted_floats(float *vals, int len)
 221 {
 222     int i,j;
 223
 224     for (i = 0; i < len - 1; i++)
 225         for (j = i; j >= 0 && vals[j] > vals[j+1]; j--)
 226             FFSWAP(float, vals[j], vals[j+1]);
 227 }