apps/codecs/libspeex/lpc.h

   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