/******************************************************************************
 *                                                                            *
 * Copyright (c) 1999-2003 Wimba S.A., All Rights Reserved.                   *
 *                                                                            *
 * COPYRIGHT:                                                                 *
 *      This software is the property of Wimba S.A.                           *
 *      This software is redistributed under the Xiph.org variant of          *
 *      the BSD license.                                                      *
 *      Redistribution and use in source and binary forms, with or without    *
 *      modification, are permitted provided that the following conditions    *
 *      are met:                                                              *
 *      - Redistributions of source code must retain the above copyright      *
 *      notice, this list of conditions and the following disclaimer.         *
 *      - Redistributions in binary form must reproduce the above copyright   *
 *      notice, this list of conditions and the following disclaimer in the   *
 *      documentation and/or other materials provided with the distribution.  *
 *      - Neither the name of Wimba, the Xiph.org Foundation nor the names of *
 *      its contributors may be used to endorse or promote products derived   *
 *      from this software without specific prior written permission.         *
 *                                                                            *
 * WARRANTIES:                                                                *
 *      This software is made available by the authors in the hope            *
 *      that it will be useful, but without any warranty.                     *
 *      Wimba S.A. is not liable for any consequence related to the           *
 *      use of the provided software.                                         *
 *                                                                            *
 * Class: Lsp.java                                                            *
 *                                                                            *
 * Author: James LAWRENCE                                                     *
 * Modified by: Marc GIMPEL                                                   *
 * Based on code by: Jean-Marc VALIN                                          *
 *                                                                            *
 * Date: March 2003                                                           *
 *                                                                            *
 ******************************************************************************/

/* $Id: Lsp.java,v 1.2 2004/10/21 16:21:57 mgimpel Exp $ */

/* 
Original copyright
  FILE........: AKSLSPD.C
  TYPE........: Turbo C
  COMPANY.....: Voicetronix
  AUTHOR......: David Rowe
  DATE CREATED: 24/2/93

Modified by Jean-Marc Valin

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:
   
   - Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
   
   - Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
   
   - Neither the name of the Xiph.org Foundation nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
   
   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package org.xiph.speex;

/**
 * Line Spectral Pair
 * 
 * @author Jim Lawrence, helloNetwork.com
 * @author Marc Gimpel, Wimba S.A. (mgimpel@horizonwimba.com)
 * @version $Revision: 1.2 $
 */
public class Lsp
{
  private float[] pw;
  
  /**
   * Constructor
   */
  public Lsp()
  {
    pw  = new float[42];
  }

  /*-------------------------------------------------------------------------*\

    FUNCTION....: cheb_poly_eva()

    AUTHOR......: David Rowe
    DATE CREATED: 24/2/93

      This function evaluates a series of Chebyshev polynomials

  \*-------------------------------------------------------------------------*/

  /**
   * This function evaluates a series of Chebyshev polynomials.
   * @param coef - coefficients of the polynomial to be evaluated.
   * @param x    - the point where polynomial is to be evaluated.
   * @param m    - order of the polynomial.
   * @return the value of the polynomial at point x.
   */
  public static final float cheb_poly_eva(final float[] coef,
                                          float x,
                                          final int m)
  {
    int i;
    float sum;
    float[] T;
    int m2 = m >> 1;
    /* Allocate memory for Chebyshev series formulation */
    T = new float[m2+1];
    /* Initialise values */
    T[0] = 1;
    T[1] = x;
    /* Evaluate Chebyshev series formulation using iterative approach  */
    /* Evaluate polynomial and return value also free memory space */
    sum = coef[m2] + coef[m2-1]*x;
    x *= 2;
    for (i=2; i<=m2; i++)
    {
      T[i] = x*T[i-1] - T[i-2];
      sum += coef[m2-i] * T[i];
    }
    return sum;
  }

  /*-------------------------------------------------------------------------*\

    FUNCTION....: lpc_to_lsp()

    AUTHOR......: David Rowe
    DATE CREATED: 24/2/93

      This function converts LPC coefficients to LSP
      coefficients.

  \*-------------------------------------------------------------------------*/

  /**
   * This function converts LPC coefficients to LSP coefficients.
   * @param a      - LPC coefficients.
   * @param lpcrdr - order of LPC coefficients (10).
   * @param freq   - LSP frequencies in the x domain.
   * @param nb     - number of sub-intervals (4).
   * @param delta  - grid spacing interval (0.02).
   * @return the number of roots (the LSP coefs are returned in the array).
   */
  public static int lpc2lsp (final float[] a,
                             final int lpcrdr,
                             final float[] freq,
                             final int nb,
                             final float delta)
  {
    float psuml, psumr, psumm, temp_xr, xl, xr, xm=0;
    float temp_psumr;
    int i, j, m, flag, k;
    float[] Q;     // ptrs for memory allocation
    float[] P;
    int px;        // ptrs of respective P'(z) & Q'(z)
    int qx;
    int p;
    int q;
    float[] pt;    // ptr used for cheb_poly_eval() whether P' or Q'
    int roots = 0; // DR 8/2/94: number of roots found
    flag = 1;      // program is searching for a root when, 1 else has found one
    m = lpcrdr/2;  // order of P'(z) & Q'(z) polynomials

    /* Allocate memory space for polynomials */
    Q = new float[m+1];
    P = new float[m+1];

    /* determine P'(z)'s and Q'(z)'s coefficients where
    P'(z) = P(z)/(1 + z^(-1)) and Q'(z) = Q(z)/(1-z^(-1)) */

    px = 0;                      /* initialise ptrs       */
    qx = 0;
    p = px;
    q = qx;
    P[px++] = 1.0f;
    Q[qx++] = 1.0f;
    for (i=1; i<=m; i++){
      P[px++] = a[i]+a[lpcrdr+1-i]-P[p++];
      Q[qx++] = a[i]-a[lpcrdr+1-i]+Q[q++];
    }
    px = 0;
    qx = 0;
    for (i=0; i<m; i++){
      P[px] = 2*P[px];
      Q[qx] = 2*Q[qx];
      px++;
      qx++;
    }
    px = 0; /* re-initialise ptrs */
    qx = 0;

    /* Search for a zero in P'(z) polynomial first and then alternate to Q'(z).
    Keep alternating between the two polynomials as each zero is found  */

    xr = 0;    /* initialise xr to zero */
    xl = 1.0f; /* start at point xl = 1 */

    for (j=0; j<lpcrdr; j++){
      if (j%2 != 0) /* determines whether P' or Q' is eval. */
        pt = Q;
      else
        pt = P;

      psuml = cheb_poly_eva(pt, xl, lpcrdr); /* evals poly. at xl */
      flag = 1;
      while ((flag == 1) && (xr >= -1.0)) {
        float dd;
        /* Modified by JMV to provide smaller steps around x=+-1 */
        dd=(float)(delta*(1-.9*xl*xl));
        if (Math.abs(psuml)<.2)
          dd *= .5;

        xr = xl - dd;                          /* interval spacing */
        psumr = cheb_poly_eva(pt, xr, lpcrdr); /* poly(xl-delta_x) */
        temp_psumr = psumr;
        temp_xr = xr;

        /* if no sign change increment xr and re-evaluate poly(xr). Repeat til
        sign change.
        if a sign change has occurred the interval is bisected and then
        checked again for a sign change which determines in which
        interval the zero lies in.
        If there is no sign change between poly(xm) and poly(xl) set interval
        between xm and xr else set interval between xl and xr and repeat till
        root is located within the specified limits */

        if ((psumr*psuml)<0.0) {
          roots++;

          psumm = psuml;
          for (k=0; k<=nb; k++){
            xm = (xl+xr)/2; /* bisect the interval */
            psumm = cheb_poly_eva(pt, xm, lpcrdr);
            if (psumm*psuml>0.) {
              psuml = psumm;
              xl = xm;
            }
            else {
              psumr = psumm;
              xr = xm;
            }
          }

          /* once zero is found, reset initial interval to xr */
          freq[j] = xm;
          xl = xm;
          flag = 0; /* reset flag for next search */
        }
        else {
          psuml = temp_psumr;
          xl = temp_xr;
        }
      }
    }
    return roots;
  }

  /**
   * Line Spectral Pair to Linear Prediction Coefficients
   * @param freq
   * @param ak
   * @param lpcrdr
   */
  public void lsp2lpc(final float[] freq,
                      final float[] ak,
                      final int lpcrdr)
  {
    int i, j;
    float xout1, xout2, xin1, xin2;
    int n1, n2 ,n3, n4=0;
    int m = lpcrdr/2;

    for (i=0; i < 4*m+2; i++) {
      pw[i] = 0.0f;
    }

    xin1 = 1.0f;
    xin2 = 1.0f;

    /* reconstruct P(z) and Q(z) by  cascading second order
    polynomials in form 1 - 2xz(-1) +z(-2), where x is the
    LSP coefficient */
    for (j=0; j<=lpcrdr; j++) {
      int i2=0;
      
      for (i=0; i<m; i++, i2+=2) {
        n1 = i*4;
        n2 = n1 + 1;
        n3 = n2 + 1;
        n4 = n3 + 1;
        xout1 = xin1 - 2*(freq[i2]) * pw[n1] + pw[n2];
        xout2 = xin2 - 2*(freq[i2+1]) * pw[n3] + pw[n4];
        pw[n2] = pw[n1];
        pw[n4] = pw[n3];
        pw[n1] = xin1;
        pw[n3] = xin2;
        xin1 = xout1;
        xin2 = xout2;
      }
      xout1    = xin1 + pw[n4+1];
      xout2    = xin2 - pw[n4+2];
      ak[j]    = (xout1 + xout2)*0.5f;
      pw[n4+1] = xin1;
      pw[n4+2] = xin2;
      xin1     = 0.0f;
      xin2     = 0.0f;
    } 
  }

  /**
   * Makes sure the LSPs are stable.
   * @param lsp
   * @param len
   * @param margin
   */
  public static void enforce_margin(final float[] lsp,
                                    final int len,
                                    final float margin)
  {
    int i;
    
    if (lsp[0]<margin)
      lsp[0]=margin;
    
    if (lsp[len-1]>(float)Math.PI-margin)
      lsp[len-1]=(float)Math.PI-margin;
    
    for (i=1;i<len-1;i++)
    {
      if (lsp[i]<lsp[i-1]+margin)
        lsp[i]=lsp[i-1]+margin;

      if (lsp[i]>lsp[i+1]-margin)
        lsp[i]= .5f * (lsp[i] + lsp[i+1]-margin);
    }
  }
}