• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • File List
  • Globals

libavcodec/lsp.c

Go to the documentation of this file.
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 
00068 void ff_acelp_lsf2lspd(double *lsp, const float *lsf, int lp_order)
00069 {
00070     int i;
00071 
00072     for(i = 0; i < lp_order; i++)
00073         lsp[i] = cos(2.0 * M_PI * lsf[i]);
00074 }
00075 
00081 static void lsp2poly(int* f, const int16_t* lsp, int lp_half_order)
00082 {
00083     int i, j;
00084 
00085     f[0] = 0x400000;          // 1.0 in (3.22)
00086     f[1] = -lsp[0] << 8;      // *2 and (0.15) -> (3.22)
00087 
00088     for(i=2; i<=lp_half_order; i++)
00089     {
00090         f[i] = f[i-2];
00091         for(j=i; j>1; j--)
00092             f[j] -= MULL(f[j-1], lsp[2*i-2], FRAC_BITS) - f[j-2];
00093 
00094         f[1] -= lsp[2*i-2] << 8;
00095     }
00096 }
00097 
00098 void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
00099 {
00100     int i;
00101     int f1[MAX_LP_HALF_ORDER+1]; // (3.22)
00102     int f2[MAX_LP_HALF_ORDER+1]; // (3.22)
00103 
00104     lsp2poly(f1, lsp  , lp_half_order);
00105     lsp2poly(f2, lsp+1, lp_half_order);
00106 
00107     /* 3.2.6 of G.729, Equations 25 and  26*/
00108     lp[0] = 4096;
00109     for(i=1; i<lp_half_order+1; i++)
00110     {
00111         int ff1 = f1[i] + f1[i-1]; // (3.22)
00112         int ff2 = f2[i] - f2[i-1]; // (3.22)
00113 
00114         ff1 += 1 << 10; // for rounding
00115         lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
00116         lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
00117     }
00118 }
00119 
00120 void ff_amrwb_lsp2lpc(const double *lsp, float *lp, int lp_order)
00121 {
00122     int lp_half_order = lp_order >> 1;
00123     double buf[MAX_LP_HALF_ORDER + 1];
00124     double pa[MAX_LP_HALF_ORDER + 1];
00125     double *qa = buf + 1;
00126     int i,j;
00127 
00128     qa[-1] = 0.0;
00129 
00130     ff_lsp2polyf(lsp    , pa, lp_half_order    );
00131     ff_lsp2polyf(lsp + 1, qa, lp_half_order - 1);
00132 
00133     for (i = 1, j = lp_order - 1; i < lp_half_order; i++, j--) {
00134         double paf =  pa[i]            * (1 + lsp[lp_order - 1]);
00135         double qaf = (qa[i] - qa[i-2]) * (1 - lsp[lp_order - 1]);
00136         lp[i-1]  = (paf + qaf) * 0.5;
00137         lp[j-1]  = (paf - qaf) * 0.5;
00138     }
00139 
00140     lp[lp_half_order - 1] = (1.0 + lsp[lp_order - 1]) *
00141         pa[lp_half_order] * 0.5;
00142 
00143     lp[lp_order - 1] = lsp[lp_order - 1];
00144 }
00145 
00146 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)
00147 {
00148     int16_t lsp_1st[MAX_LP_ORDER]; // (0.15)
00149     int i;
00150 
00151     /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/
00152     for(i=0; i<lp_order; i++)
00153 #ifdef G729_BITEXACT
00154         lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1);
00155 #else
00156         lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1;
00157 #endif
00158 
00159     ff_acelp_lsp2lpc(lp_1st, lsp_1st, lp_order >> 1);
00160 
00161     /* LSP values for second subframe (3.2.5 of G.729)*/
00162     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
00163 }
00164 
00165 void ff_lsp2polyf(const double *lsp, double *f, int lp_half_order)
00166 {
00167     int i, j;
00168 
00169     f[0] = 1.0;
00170     f[1] = -2 * lsp[0];
00171     lsp -= 2;
00172     for(i=2; i<=lp_half_order; i++)
00173     {
00174         double val = -2 * lsp[2*i];
00175         f[i] = val * f[i-1] + 2*f[i-2];
00176         for(j=i-1; j>1; j--)
00177             f[j] += f[j-1] * val + f[j-2];
00178         f[1] += val;
00179     }
00180 }
00181 
00182 void ff_acelp_lspd2lpc(const double *lsp, float *lpc, int lp_half_order)
00183 {
00184     double pa[MAX_LP_HALF_ORDER+1], qa[MAX_LP_HALF_ORDER+1];
00185     float *lpc2 = lpc + (lp_half_order << 1) - 1;
00186 
00187     assert(lp_half_order <= MAX_LP_HALF_ORDER);
00188 
00189     ff_lsp2polyf(lsp,     pa, lp_half_order);
00190     ff_lsp2polyf(lsp + 1, qa, lp_half_order);
00191 
00192     while (lp_half_order--) {
00193         double paf = pa[lp_half_order+1] + pa[lp_half_order];
00194         double qaf = qa[lp_half_order+1] - qa[lp_half_order];
00195 
00196         lpc [ lp_half_order] = 0.5*(paf+qaf);
00197         lpc2[-lp_half_order] = 0.5*(paf-qaf);
00198     }
00199 }
00200 
00201 void ff_sort_nearly_sorted_floats(float *vals, int len)
00202 {
00203     int i,j;
00204 
00205     for (i = 0; i < len - 1; i++)
00206         for (j = i; j >= 0 && vals[j] > vals[j+1]; j--)
00207             FFSWAP(float, vals[j], vals[j+1]);
00208 }
Generated on Fri Feb 1 2013 14:34:38 for FFmpeg by doxygen 1.7.1