From 8726882993df25c713ee51c2674492366ff84cfe Mon Sep 17 00:00:00 2001 From: Vladimir Voroshilov Date: Sat, 26 Apr 2008 11:52:33 +0000 Subject: Fixed-point LSP and LPC decoding routines for ACELP-based codecs Originally committed as revision 12978 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/lsp.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 libavcodec/lsp.c (limited to 'libavcodec/lsp.c') diff --git a/libavcodec/lsp.c b/libavcodec/lsp.c new file mode 100644 index 0000000000..9a09f8d485 --- /dev/null +++ b/libavcodec/lsp.c @@ -0,0 +1,120 @@ +/* + * LSP routines for ACELP-based codecs + * + * Copyright (c) 2008 Vladimir Voroshilov + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include + +#include "avcodec.h" +#define FRAC_BITS 14 +#include "mathops.h" +#include "lsp.h" +#include "acelp_math.h" + +void ff_acelp_reorder_lsf(int16_t* lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max) +{ + int i, j; + + /* sort lsfq in ascending order. float bubble agorithm, + O(n) if data already sorted, O(n^2) - otherwise */ + for(i=0; i<9; i++) + for(j=i; j>=0 && lsfq[j] > lsfq[j+1]; j--) + FFSWAP(int16_t, lsfq[j], lsfq[j+1]); + + for(i=0;i<10; i++) + { + lsfq[i] = FFMAX(lsfq[i], lsfq_min); + lsfq_min = lsfq[i] + lsfq_min_distance; + } + lsfq[9] = FFMIN(lsfq[9], lsfq_max);//Is warning required ? +} + +void ff_acelp_lsf2lsp(int16_t *lsp, const int16_t *lsf) +{ + int i; + + /* Convert LSF to LSP, lsp=cos(lsf) */ + for(i=0;i<10; i++) + // 20861 = 2.0 / PI in (0.15) + lsp[i] = ff_cos(lsf[i] * 20861 >> 15); // divide by PI and (0,13) -> (0,14) +} + +/** + * \brief decodes polynomial coefficients from LSP + * \param f [out] decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff) + * \param lsp LSP coefficients (-0x8000 <= (0.15) <= 0x7fff) + */ +static void lsp2poly(int* f, const int16_t* lsp) +{ + int i, j; + + f[0] = 0x400000; // 1.0 in (3.22) + f[1] = -lsp[0] << 8; // *2 and (0.15) -> (3.22) + + for(i=2; i<=5; i++) + { + f[i] = f[i-2]; + for(j=i; j>1; j--) + f[j] -= MULL(f[j-1], lsp[2*i-2]) - f[j-2]; // (3.22) * (0.15) * 2 -> (3.22) + + f[1] -= lsp[2*i-2] << 8; + } +} + +void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp) +{ + int i; + int f1[6]; // (3.22) + int f2[6]; // (3.22) + + lsp2poly(f1, lsp ); + lsp2poly(f2, lsp+1); + + /* 3.2.6 of G.729, Equations 25 and 26*/ + lp[0] = 4096; + for(i=1; i<6; i++) + { + int ff1 = f1[i] + f1[i-1]; // (3.22) + int ff2 = f2[i] - f2[i-1]; // (3.22) + + ff1 += 1 << 10; // for rounding + lp[i] = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12) + lp[11-i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12) + } +} + +void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd, const int16_t* lsp_prev) +{ + int16_t lsp_1st[10]; // (0.15) + int i; + + /* LSP values for first subframe (3.2.5 of G.729, Equation 24)*/ + for(i=0;i<10;i++) +#ifdef G729_BITEXACT + lsp_1st[i] = (lsp_2nd[i] >> 1) + (lsp_prev[i] >> 1); +#else + lsp_1st[i] = (lsp_2nd[i] + lsp_prev[i]) >> 1; +#endif + + ff_acelp_lsp2lpc(lp_1st, lsp_1st); + + /* LSP values for second subframe (3.2.5 of G.729)*/ + ff_acelp_lsp2lpc(lp_2nd, lsp_2nd); +} -- cgit v1.2.3