1 /* Copyright (C) 2002 Jean-Marc Valin */ 2 /** 3 @file lpc.h 4 @brief Functions for LPC (Linear Prediction Coefficients) analysis 5 */ 6 /* 7 Redistribution and use in source and binary forms, with or without 8 modification, are permitted provided that the following conditions 9 are met: 10 11 - Redistributions of source code must retain the above copyright 12 notice, this list of conditions and the following disclaimer. 13 14 - Redistributions in binary form must reproduce the above copyright 15 notice, this list of conditions and the following disclaimer in the 16 documentation and/or other materials provided with the distribution. 17 18 - Neither the name of the Xiph.org Foundation nor the names of its 19 contributors may be used to endorse or promote products derived from 20 this software without specific prior written permission. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 25 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR 26 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 27 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 28 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 29 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 30 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 31 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 32 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 */ 34 35 #ifndef LPC_H 36 #define LPC_H 37 38 #include "arch.h" 39 40 void _spx_autocorr( 41 const spx_word16_t * x, /* in: [0...n-1] samples x */ 42 spx_word16_t *ac, /* out: [0...lag-1] ac values */ 43 int lag, int n); 44 45 spx_word32_t /* returns minimum mean square error */ 46 _spx_lpc( 47 spx_coef_t * lpc, /* [0...p-1] LPC coefficients */ 48 const spx_word16_t * ac, /* in: [0...p] autocorrelation values */ 49 int p 50 ); 51 52 53 #endif 54