libavcodec/lsp.c

   1 /*
   2  * LSP routines for ACELP-based codecs
   3  *
   4  * Copyright (c) 2008 Vladimir Voroshilov
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <inttypes.h>
  24
  25 #include "avcodec.h"
  26 #define FRAC_BITS 14
  27 #include "mathops.h"
  28 #include "lsp.h"
  29 #include "acelp_math.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_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order)
  50 {
  51     int i;
  52
  53     /* Convert LSF to LSP, lsp=cos(lsf) */
  54     for(i=0; i<lp_order; i++)
  55         // 20861 = 2.0 / PI in (0.15)
  56         lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14)
  57 }
  58
  59 /**
  60  * \brief decodes polynomial coefficients from LSP
  61  * \param f [out] decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff)
  62  * \param lsp LSP coefficients (-0x8000 <= (0.15) <= 0x7fff)
  63  */
  64 static void lsp2poly(int* f, const int16_t* lsp, int lp_half_order)
  65 {
  66     int i, j;
  67
  68     f[0] = 0x400000;          // 1.0 in (3.22)
  69     f[1] = -lsp[0] << 8;      // *2 and (0.15) -> (3.22)
  70
  71     for(i=2; i<=lp_half_order; i++)
  72     {
  73         f[i] = f[i-2];
  74         for(j=i; j>1; j--)
  75             f[j] -= MULL(f[j-1], lsp[2*i-2]) - f[j-2]; // (3.22) * (0.15) * 2 -> (3.22)
  76
  77         f[1] -= lsp[2*i-2] << 8;
  78     }
  79 }
  80
  81 void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
  82 {
  83     int i;
  84     int f1[lp_half_order+1]; // (3.22)
  85     int f2[lp_half_order+1]; // (3.22)
  86
  87     lsp2poly(f1, lsp  , lp_half_order);
  88     lsp2poly(f2, lsp+1, lp_half_order);
  89
  90     /* 3.2.6 of G.729, Equations 25 and  26*/
  91     lp[0] = 4096;
  92     for(i=1; i<lp_half_order+1; i++)
  93     {
  94         int ff1 = f1[i] + f1[i-1]; // (3.22)
  95         int ff2 = f2[i] - f2[i-1]; // (3.22)
  96
  97         ff1 += 1 << 10; // for rounding
  98         lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
  99         lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
 100     }
 101 }
 102
 103 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)
 104 {
 105     int16_t lsp_1st[lp_order]; // (0.15)
 106     int i;
 107
 108     /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
 109     for(i=0; i<lp_order; i++)
 110 #ifdef G729_BITEXACT
 111         lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1);
 112 #else
 113         lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
 114 #endif
 115
 116     ff_acelp_lsp2lpc(lp_1st, lsp_1st, lp_order >> 1);
 117
 118     /* LSP values for second subframe (3.2.5 of G.729)*/
 119     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
 120 }