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libavcodec/lsp.c

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00001 /*
00002  * LSP routines for ACELP-based codecs
00003  *
00004  * Copyright (c) 2007 Reynaldo H. Verdejo Pinochet (QCELP decoder)
00005  * Copyright (c) 2008 Vladimir Voroshilov
00006  *
00007  * This file is part of FFmpeg.
00008  *
00009  * FFmpeg is free software; you can redistribute it and/or
00010  * modify it under the terms of the GNU Lesser General Public
00011  * License as published by the Free Software Foundation; either
00012  * version 2.1 of the License, or (at your option) any later version.
00013  *
00014  * FFmpeg is distributed in the hope that it will be useful,
00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00017  * Lesser General Public License for more details.
00018  *
00019  * You should have received a copy of the GNU Lesser General Public
00020  * License along with FFmpeg; if not, write to the Free Software
00021  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00022  */
00023 
00024 #include <inttypes.h>
00025 
00026 #include "avcodec.h"
00027 #define FRAC_BITS 14
00028 #include "mathops.h"
00029 #include "lsp.h"
00030 #include "celp_math.h"
00031 
00032 void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max, int lp_order)
00033 {
00034     int i, j;
00035 
00036     /* sort lsfq in ascending order. float bubble agorithm,
00037        O(n) if data already sorted, O(n^2) - otherwise */
00038     for(i=0; i<lp_order-1; i++)
00039         for(j=i; j>=0 && lsfq[j] > lsfq[j+1]; j--)
00040             FFSWAP(int16_t, lsfq[j], lsfq[j+1]);
00041 
00042     for(i=0; i<lp_order; i++)
00043     {
00044         lsfq[i] = FFMAX(lsfq[i], lsfq_min);
00045         lsfq_min = lsfq[i] + lsfq_min_distance;
00046     }
00047     lsfq[lp_order-1] = FFMIN(lsfq[lp_order-1], lsfq_max);//Is warning required ?
00048 }
00049 
00050 void ff_set_min_dist_lsf(float *lsf, double min_spacing, int size)
00051 {
00052     int i;
00053     float prev = 0.0;
00054     for (i = 0; i < size; i++)
00055         prev = lsf[i] = FFMAX(lsf[i], prev + min_spacing);
00056 }
00057 
00058 void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf, int lp_order)
00059 {
00060     int i;
00061 
00062     /* Convert LSF to LSP, lsp=cos(lsf) */
00063     for(i=0; i<lp_order; i++)
00064         // 20861 = 2.0 / PI in (0.15)
00065         lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14)
00066 }
00067 
00073 static void lsp2poly(int* f, const int16_t* lsp, int lp_half_order)
00074 {
00075     int i, j;
00076 
00077     f[0] = 0x400000;          // 1.0 in (3.22)
00078     f[1] = -lsp[0] << 8;      // *2 and (0.15) -> (3.22)
00079 
00080     for(i=2; i<=lp_half_order; i++)
00081     {
00082         f[i] = f[i-2];
00083         for(j=i; j>1; j--)
00084             f[j] -= MULL(f[j-1], lsp[2*i-2], FRAC_BITS) - f[j-2];
00085 
00086         f[1] -= lsp[2*i-2] << 8;
00087     }
00088 }
00089 
00090 void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
00091 {
00092     int i;
00093     int f1[lp_half_order+1]; // (3.22)
00094     int f2[lp_half_order+1]; // (3.22)
00095 
00096     lsp2poly(f1, lsp  , lp_half_order);
00097     lsp2poly(f2, lsp+1, lp_half_order);
00098 
00099     /* 3.2.6 of G.729, Equations 25 and  26*/
00100     lp[0] = 4096;
00101     for(i=1; i<lp_half_order+1; i++)
00102     {
00103         int ff1 = f1[i] + f1[i-1]; // (3.22)
00104         int ff2 = f2[i] - f2[i-1]; // (3.22)
00105 
00106         ff1 += 1 << 10; // for rounding
00107         lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
00108         lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
00109     }
00110 }
00111 
00112 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)
00113 {
00114     int16_t lsp_1st[lp_order]; // (0.15)
00115     int i;
00116 
00117     /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
00118     for(i=0; i<lp_order; i++)
00119 #ifdef G729_BITEXACT
00120         lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1);
00121 #else
00122         lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
00123 #endif
00124 
00125     ff_acelp_lsp2lpc(lp_1st, lsp_1st, lp_order >> 1);
00126 
00127     /* LSP values for second subframe (3.2.5 of G.729)*/
00128     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
00129 }
00130 
00131 void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order)
00132 {
00133     int i, j;
00134 
00135     f[0] = 1.0;
00136     f[1] = -2 * lsp[0];
00137     lsp -= 2;
00138     for(i=2; i<=lp_half_order; i++)
00139     {
00140         double val = -2 * lsp[2*i];
00141         f[i] = val * f[i-1] + 2*f[i-2];
00142         for(j=i-1; j>1; j--)
00143             f[j] += f[j-1] * val + f[j-2];
00144         f[1] += val;
00145     }
00146 }
00147 
00148 void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order)
00149 {
00150     double pa[MAX_LP_HALF_ORDER+1], qa[MAX_LP_HALF_ORDER+1];
00151     float *lpc2 = lpc + (lp_half_order << 1) - 1;
00152 
00153     assert(lp_half_order <= MAX_LP_HALF_ORDER);
00154 
00155     ff_lsp2polyf(lsp,     pa, lp_half_order);
00156     ff_lsp2polyf(lsp + 1, qa, lp_half_order);
00157 
00158     while (lp_half_order--) {
00159         double paf = pa[lp_half_order+1] + pa[lp_half_order];
00160         double qaf = qa[lp_half_order+1] - qa[lp_half_order];
00161 
00162         lpc [ lp_half_order] = 0.5*(paf+qaf);
00163         lpc2[-lp_half_order] = 0.5*(paf-qaf);
00164     }
00165 }
00166 
00167 void ff_sort_nearly_sorted_floats(float *vals, int len)
00168 {
00169     int i,j;
00170 
00171     for (i = 0; i < len - 1; i++)
00172         for (j = i; j >= 0 && vals[j] > vals[j+1]; j--)
00173             FFSWAP(float, vals[j], vals[j+1]);
00174 }

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