| /* |
| * LPC utility functions |
| * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> |
| * |
| * 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 |
| */ |
| |
| #ifndef AVCODEC_LPC_FUNCTIONS_H |
| #define AVCODEC_LPC_FUNCTIONS_H |
| |
| #include "libavutil/avassert.h" |
| |
| #ifndef LPC_USE_FIXED |
| #define LPC_USE_FIXED 0 |
| #endif |
| |
| #if LPC_USE_FIXED |
| typedef int LPC_TYPE; |
| typedef unsigned LPC_TYPE_U; |
| #else |
| #ifndef LPC_SRA_R |
| #define LPC_SRA_R(x, y) (x) |
| #define LPC_MUL26(x, y) ((x) * (y)) |
| #define LPC_FIXR(x) ((float)(x)) |
| #endif |
| |
| #ifdef LPC_USE_DOUBLE |
| typedef double LPC_TYPE; |
| typedef double LPC_TYPE_U; |
| #else |
| typedef float LPC_TYPE; |
| typedef float LPC_TYPE_U; |
| #endif |
| #endif // USE_FIXED |
| |
| /** |
| * Levinson-Durbin recursion. |
| * Produce LPC coefficients from autocorrelation data. |
| */ |
| static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, |
| LPC_TYPE *lpc, int lpc_stride, int fail, |
| int normalize) |
| { |
| LPC_TYPE err = 0; |
| LPC_TYPE *lpc_last = lpc; |
| |
| av_assert2(normalize || !fail); |
| |
| if (normalize) |
| err = *autoc++; |
| |
| if (fail && (autoc[max_order - 1] == 0 || err <= 0)) |
| return -1; |
| |
| for(int i = 0; i < max_order; i++) { |
| LPC_TYPE r = LPC_SRA_R(-autoc[i], 5); |
| |
| if (normalize) { |
| for(int j = 0; j < i; j++) |
| r -= lpc_last[j] * autoc[i-j-1]; |
| |
| if (err) |
| r /= err; |
| err *= LPC_FIXR(1.0) - (r * r); |
| } |
| |
| lpc[i] = r; |
| |
| for(int j = 0; j < (i + 1) >> 1; j++) { |
| LPC_TYPE f = lpc_last[ j]; |
| LPC_TYPE b = lpc_last[i-1-j]; |
| lpc[ j] = f + (LPC_TYPE_U)LPC_MUL26(r, b); |
| lpc[i-1-j] = b + (LPC_TYPE_U)LPC_MUL26(r, f); |
| } |
| |
| if (fail && err < 0) |
| return -1; |
| |
| lpc_last = lpc; |
| lpc += lpc_stride; |
| } |
| |
| return 0; |
| } |
| |
| #endif /* AVCODEC_LPC_FUNCTIONS_H */ |