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_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order)
  51 {
  52     int i;
  53
  54     /* Convert LSF to LSP, lsp=cos(lsf) */
  55     for(i=0; i<lp_order; i++)
  56         // 20861 = 2.0 / PI in (0.15)
  57         lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14)
  58 }
  59
  60 /**
  61  * \brief decodes polynomial coefficients from LSP
  62  * \param f [out] decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff)
  63  * \param lsp LSP coefficients (-0x8000 <= (0.15) <= 0x7fff)
  64  */
  65 static void lsp2poly(int* f, const int16_t* lsp, int lp_half_order)
  66 {
  67     int i, j;
  68
  69     f[0] = 0x400000;          // 1.0 in (3.22)
  70     f[1] = -lsp[0] << 8;      // *2 and (0.15) -> (3.22)
  71
  72     for(i=2; i<=lp_half_order; i++)
  73     {
  74         f[i] = f[i-2];
  75         for(j=i; j>1; j--)
  76             f[j] -= MULL(f[j-1], lsp[2*i-2], FRAC_BITS) - f[j-2];
  77
  78         f[1] -= lsp[2*i-2] << 8;
  79     }
  80 }
  81
  82 void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
  83 {
  84     int i;
  85     int f1[lp_half_order+1]; // (3.22)
  86     int f2[lp_half_order+1]; // (3.22)
  87
  88     lsp2poly(f1, lsp  , lp_half_order);
  89     lsp2poly(f2, lsp+1, lp_half_order);
  90
  91     /* 3.2.6 of G.729, Equations 25 and  26*/
  92     lp[0] = 4096;
  93     for(i=1; i<lp_half_order+1; i++)
  94     {
  95         int ff1 = f1[i] + f1[i-1]; // (3.22)
  96         int ff2 = f2[i] - f2[i-1]; // (3.22)
  97
  98         ff1 += 1 << 10; // for rounding
  99         lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 100         lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 101     }
 102 }
 103
 104 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)
 105 {
 106     int16_t lsp_1st[lp_order]; // (0.15)
 107     int i;
 108
 109     /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
 110     for(i=0; i<lp_order; i++)
 111 #ifdef G729_BITEXACT
 112         lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1);
 113 #else
 114         lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
 115 #endif
 116
 117     ff_acelp_lsp2lpc(lp_1st, lsp_1st, lp_order >> 1);
 118
 119     /* LSP values for second subframe (3.2.5 of G.729)*/
 120     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
 121 }
 122
 123 /**
 124  * Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients
 125  * needed for LSP to LPC conversion.
 126  * We only need to calculate the 6 first elements of the polynomial.
 127  *
 128  * @param lsp line spectral pairs in cosine domain
 129  * @param f [out] polynomial input/output as a vector
 130  *
 131  * TIA/EIA/IS-733 2.4.3.3.5-1/2
 132  */
 133 static void lsp2polyf(const double *lsp, double *f, int lp_half_order)
 134 {
 135     int i, j;
 136
 137     f[0] = 1.0;
 138     f[1] = -2 * lsp[0];
 139     lsp -= 2;
 140     for(i=2; i<=lp_half_order; i++)
 141     {
 142         double val = -2 * lsp[2*i];
 143         f[i] = val * f[i-1] + 2*f[i-2];
 144         for(j=i-1; j>1; j--)
 145             f[j] += f[j-1] * val + f[j-2];
 146         f[1] += val;
 147     }
 148 }
 149
 150 void ff_acelp_lspd2lpc(const double *lsp, float *lpc)
 151 {
 152     double pa[6], qa[6];
 153     int   i;
 154
 155     lsp2polyf(lsp,     pa, 5);
 156     lsp2polyf(lsp + 1, qa, 5);
 157
 158     for (i=4; i>=0; i--)
 159     {
 160         double paf = pa[i+1] + pa[i];
 161         double qaf = qa[i+1] - qa[i];
 162
 163         lpc[i  ] = 0.5*(paf+qaf);
 164         lpc[9-i] = 0.5*(paf-qaf);
 165     }
 166 }