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100 lines
2.6 KiB
100 lines
2.6 KiB
/* |
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* LPC utility functions |
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* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#ifndef AVCODEC_LPC_FUNCTIONS_H |
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#define AVCODEC_LPC_FUNCTIONS_H |
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#include "libavutil/avassert.h" |
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#ifndef LPC_USE_FIXED |
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#define LPC_USE_FIXED 0 |
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#endif |
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#if LPC_USE_FIXED |
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typedef int LPC_TYPE; |
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typedef unsigned LPC_TYPE_U; |
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#else |
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#ifndef LPC_SRA_R |
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#define LPC_SRA_R(x, y) (x) |
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#define LPC_MUL26(x, y) ((x) * (y)) |
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#define LPC_FIXR(x) ((float)(x)) |
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#endif |
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#ifdef LPC_USE_DOUBLE |
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typedef double LPC_TYPE; |
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typedef double LPC_TYPE_U; |
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#else |
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typedef float LPC_TYPE; |
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typedef float LPC_TYPE_U; |
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#endif |
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#endif // USE_FIXED |
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/** |
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* Levinson-Durbin recursion. |
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* Produce LPC coefficients from autocorrelation data. |
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*/ |
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static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, |
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LPC_TYPE *lpc, int lpc_stride, int fail, |
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int normalize) |
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{ |
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LPC_TYPE err = 0; |
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LPC_TYPE *lpc_last = lpc; |
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av_assert2(normalize || !fail); |
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if (normalize) |
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err = *autoc++; |
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if (fail && (autoc[max_order - 1] == 0 || err <= 0)) |
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return -1; |
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for(int i = 0; i < max_order; i++) { |
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LPC_TYPE r = LPC_SRA_R(-autoc[i], 5); |
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if (normalize) { |
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for(int j = 0; j < i; j++) |
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r -= lpc_last[j] * autoc[i-j-1]; |
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if (err) |
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r /= err; |
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err *= LPC_FIXR(1.0) - (r * r); |
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} |
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lpc[i] = r; |
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for(int j = 0; j < (i + 1) >> 1; j++) { |
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LPC_TYPE f = lpc_last[ j]; |
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LPC_TYPE b = lpc_last[i-1-j]; |
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lpc[ j] = f + (LPC_TYPE_U)LPC_MUL26(r, b); |
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lpc[i-1-j] = b + (LPC_TYPE_U)LPC_MUL26(r, f); |
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} |
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if (fail && err < 0) |
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return -1; |
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lpc_last = lpc; |
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lpc += lpc_stride; |
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} |
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return 0; |
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} |
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#endif /* AVCODEC_LPC_FUNCTIONS_H */
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