/*

 * This routine converts from linear to ulaw

 * 29 September 1989

 *

 * Craig Reese: IDA/Supercomputing Research Center

 * Joe Campbell: Department of Defense

 *

 * References:

 * 1) CCITT Recommendation G.711  (very difficult to follow)

 * 2) "A New Digital Technique for Implementation of Any 

 *     Continuous PCM Companding Law," Villeret, Michel,

 *     et al. 1973 IEEE Int. Conf. on Communications, Vol 1,

 *     1973, pg. 11.12-11.17

 * 3) MIL-STD-188-113,"Interoperability and Performance Standards

 *     for Analog-to_Digital Conversion Techniques,"

 *     17 February 1987

 *

 * Input: Signed 16 bit linear sample

 * Output: 8 bit ulaw sample

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <glib.h>

#undef ZEROTRAP                 /* turn on the trap as per the MIL-STD */

#define BIAS 0x84               /* define the add-in bias for 16 bit samples */

#define CLIP 32635

void

mulaw_encode (gint16 * in, guint8 * out, gint numsamples)

{

  static gint16 exp_lut[256] = { 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,

    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,

    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,

    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,

    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,

    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,

    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,

    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,

    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7

  };

  gint16 sign, exponent, mantissa, i;

  gint16 sample;

  guint8 ulawbyte;

  for (i = 0; i < numsamples; i++) {

    sample = in[i];

      /** get the sample into sign-magnitude **/

    sign = (sample >> 8) & 0x80;        /* set aside the sign */

    if (sign != 0) {

      sample = -sample;         /* get magnitude */

    }

    /* sample can be zero because we can overflow in the inversion,

     * checking against the unsigned version solves this */

    if (((guint16) sample) > CLIP)

      sample = CLIP;            /* clip the magnitude */

      /** convert from 16 bit linear to ulaw **/

    sample = sample + BIAS;

    exponent = exp_lut[(sample >> 7) & 0xFF];

    mantissa = (sample >> (exponent + 3)) & 0x0F;

    ulawbyte = ~(sign | (exponent << 4) | mantissa);

#ifdef ZEROTRAP

    if (ulawbyte == 0)

      ulawbyte = 0x02;          /* optional CCITT trap */

#endif

    out[i] = ulawbyte;

  }

}

/*

 * This routine converts from ulaw to 16 bit linear

 * 29 September 1989

 *

 * Craig Reese: IDA/Supercomputing Research Center

 *

 * References:

 * 1) CCITT Recommendation G.711  (very difficult to follow)

 * 2) MIL-STD-188-113,"Interoperability and Performance Standards

 *     for Analog-to_Digital Conversion Techniques,"

 *     17 February 1987

 *

 * Input: 8 bit ulaw sample

 * Output: signed 16 bit linear sample

 */

void

mulaw_decode (guint8 * in, gint16 * out, gint numsamples)

{

  static gint16 exp_lut[8] = { 0, 132, 396, 924, 1980, 4092, 8316, 16764 };

  gint16 sign, exponent, mantissa;

  guint8 ulawbyte;

  gint16 linear, i;

  for (i = 0; i < numsamples; i++) {

    ulawbyte = in[i];

    ulawbyte = ~ulawbyte;

    sign = (ulawbyte & 0x80);

    exponent = (ulawbyte >> 4) & 0x07;

    mantissa = ulawbyte & 0x0F;

    linear = exp_lut[exponent] + (mantissa << (exponent + 3));

    if (sign != 0)

      linear = -linear;

    out[i] = linear;

  }

}