text: /*
   * %W% %E%
   *
   * Copyright (c) 1996 Sun Microsystems, Inc. All Rights Reserved.
   *
   * This software is the confidential and proprietary information of Sun
   * Microsystems, Inc. ("Confidential Information").  You shall not
   * disclose such Confidential Information and shall use it only in
   * accordance with the terms of the license agreement you entered into
   * with Sun.
   *
   * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
   * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
   * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
   * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
   * THIS SOFTWARE OR ITS DERIVATIVES.
   *
   */
  
  /*
   * g723_24.c
   *
   * Description:
   *
   * g723_24_encoder(), g723_24_decoder()
   *
   * These routines comprise an implementation of the CCITT G.723 24 Kbps
   * ADPCM coding algorithm.  Essentially, this implementation is identical to
   * the bit level description except for a few deviations which take advantage
   * of workstation attributes, such as hardware 2's complement arithmetic.
   *
   */
  #include "g72x.h"
  
  #if USE_HIGHLEVEL_FILE_API != FALSE
  
  /*
   * Maps G.723_24 code word to reconstructed scale factor normalized log
   * magnitude values.
   */
  static const short  _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
  
  /* Maps G.723_24 code word to log of scale factor multiplier. */
  static const short  _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
  
  /*
   * Maps G.723_24 code words to a set of values whose long and short
   * term averages are computed and then compared to give an indication
   * how stationary (steady state) the signal is.
   */
  static const short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
  
  static const short qtab_723_24[3] = {8, 218, 331};
  
  #if 0
  /*
   * g723_24_encoder()
   *
   * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
   * Returns -1 if invalid input coding value.
   */
  int
  g723_24_encoder(
      int     sl,
      int     in_coding,
      struct g72x_state *state_ptr)
  {
      short       sei, sezi, se, sez; /* ACCUM */
      short       d;          /* SUBTA */
      short       y;          /* MIX */
      short       sr;         /* ADDB */
      short       dqsez;          /* ADDC */
      short       dq, i;
  
      switch (in_coding) {    /* linearize input sample to 14-bit PCM */
      case AUDIO_ENCODING_ALAW:
          sl = alaw2linear(sl) >> 2;
          break;
      case AUDIO_ENCODING_ULAW:
          sl = ulaw2linear(sl) >> 2;
          break;
      case AUDIO_ENCODING_LINEAR:
          sl >>= 2;       /* sl of 14-bit dynamic range */
          break;
      default:
          return (-1);
      }
  
      sezi = predictor_zero(state_ptr);
      sez = sezi >> 1;
      sei = sezi + predictor_pole(state_ptr);
      se = sei >> 1;          /* se = estimated signal */
  
      d = sl - se;            /* d = estimation diff. */
  
      /* quantize prediction difference d */
      y = step_size(state_ptr);   /* quantizer step size */
      i = quantize(d, y, qtab_723_24, 3); /* i = ADPCM code */
      dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
  
      sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
  
      dqsez = sr + sez - se;      /* pole prediction diff. */
  
      update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
  
      return (i);
  }
  #endif
  
  /*
   * g723_24_decoder()
   *
   * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
   * the resulting 16-bit linear PCM, A-law or u-law sample value.
   * -1 is returned if the output coding is unknown.
   */
  int
  g723_24_decoder(
      int     i,
      int     out_coding,
      struct g72x_state *state_ptr)
  {
      short       sezi, sei, sez, se; /* ACCUM */
      short       y;          /* MIX */
      short       sr;         /* ADDB */
      short       dq;
      short       dqsez;
  
      i &= 0x07;          /* mask to get proper bits */
      sezi = predictor_zero(state_ptr);
      sez = sezi >> 1;
      sei = sezi + predictor_pole(state_ptr);
      se = sei >> 1;          /* se = estimated signal */
  
      y = step_size(state_ptr);   /* adaptive quantizer step size */
      dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
  
      sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
  
      dqsez = sr - se + sez;          /* pole prediction diff. */
  
      update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
  
      switch (out_coding) {
      case AUDIO_ENCODING_ALAW:
          return (tandem_adjust_alaw(sr, se, y, i, 4, (short *)qtab_723_24));
      case AUDIO_ENCODING_ULAW:
          return (tandem_adjust_ulaw(sr, se, y, i, 4, (short *)qtab_723_24));
      case AUDIO_ENCODING_LINEAR:
          return (sr << 2);   /* sr was of 14-bit dynamic range */
      default:
          return (-1);
      }
  }
  #endif
  