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isdn_audio.c

/* $Id: isdn_audio.c,v 1.1.2.2 2004/01/12 22:37:18 keil Exp $
 *
 * Linux ISDN subsystem, audio conversion and compression (linklevel).
 *
 * Copyright 1994-1999 by Fritz Elfert (fritz@isdn4linux.de)
 * DTMF code (c) 1996 by Christian Mock (cm@kukuruz.ping.at)
 * Silence detection (c) 1998 by Armin Schindler (mac@gismo.telekom.de)
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 */

#include <linux/isdn.h>
#include "isdn_audio.h"
#include "isdn_common.h"

char *isdn_audio_revision = "$Revision: 1.1.2.2 $";

/*
 * Misc. lookup-tables.
 */

/* ulaw -> signed 16-bit */
static short isdn_audio_ulaw_to_s16[] =
{
      0x8284, 0x8684, 0x8a84, 0x8e84, 0x9284, 0x9684, 0x9a84, 0x9e84,
      0xa284, 0xa684, 0xaa84, 0xae84, 0xb284, 0xb684, 0xba84, 0xbe84,
      0xc184, 0xc384, 0xc584, 0xc784, 0xc984, 0xcb84, 0xcd84, 0xcf84,
      0xd184, 0xd384, 0xd584, 0xd784, 0xd984, 0xdb84, 0xdd84, 0xdf84,
      0xe104, 0xe204, 0xe304, 0xe404, 0xe504, 0xe604, 0xe704, 0xe804,
      0xe904, 0xea04, 0xeb04, 0xec04, 0xed04, 0xee04, 0xef04, 0xf004,
      0xf0c4, 0xf144, 0xf1c4, 0xf244, 0xf2c4, 0xf344, 0xf3c4, 0xf444,
      0xf4c4, 0xf544, 0xf5c4, 0xf644, 0xf6c4, 0xf744, 0xf7c4, 0xf844,
      0xf8a4, 0xf8e4, 0xf924, 0xf964, 0xf9a4, 0xf9e4, 0xfa24, 0xfa64,
      0xfaa4, 0xfae4, 0xfb24, 0xfb64, 0xfba4, 0xfbe4, 0xfc24, 0xfc64,
      0xfc94, 0xfcb4, 0xfcd4, 0xfcf4, 0xfd14, 0xfd34, 0xfd54, 0xfd74,
      0xfd94, 0xfdb4, 0xfdd4, 0xfdf4, 0xfe14, 0xfe34, 0xfe54, 0xfe74,
      0xfe8c, 0xfe9c, 0xfeac, 0xfebc, 0xfecc, 0xfedc, 0xfeec, 0xfefc,
      0xff0c, 0xff1c, 0xff2c, 0xff3c, 0xff4c, 0xff5c, 0xff6c, 0xff7c,
      0xff88, 0xff90, 0xff98, 0xffa0, 0xffa8, 0xffb0, 0xffb8, 0xffc0,
      0xffc8, 0xffd0, 0xffd8, 0xffe0, 0xffe8, 0xfff0, 0xfff8, 0x0000,
      0x7d7c, 0x797c, 0x757c, 0x717c, 0x6d7c, 0x697c, 0x657c, 0x617c,
      0x5d7c, 0x597c, 0x557c, 0x517c, 0x4d7c, 0x497c, 0x457c, 0x417c,
      0x3e7c, 0x3c7c, 0x3a7c, 0x387c, 0x367c, 0x347c, 0x327c, 0x307c,
      0x2e7c, 0x2c7c, 0x2a7c, 0x287c, 0x267c, 0x247c, 0x227c, 0x207c,
      0x1efc, 0x1dfc, 0x1cfc, 0x1bfc, 0x1afc, 0x19fc, 0x18fc, 0x17fc,
      0x16fc, 0x15fc, 0x14fc, 0x13fc, 0x12fc, 0x11fc, 0x10fc, 0x0ffc,
      0x0f3c, 0x0ebc, 0x0e3c, 0x0dbc, 0x0d3c, 0x0cbc, 0x0c3c, 0x0bbc,
      0x0b3c, 0x0abc, 0x0a3c, 0x09bc, 0x093c, 0x08bc, 0x083c, 0x07bc,
      0x075c, 0x071c, 0x06dc, 0x069c, 0x065c, 0x061c, 0x05dc, 0x059c,
      0x055c, 0x051c, 0x04dc, 0x049c, 0x045c, 0x041c, 0x03dc, 0x039c,
      0x036c, 0x034c, 0x032c, 0x030c, 0x02ec, 0x02cc, 0x02ac, 0x028c,
      0x026c, 0x024c, 0x022c, 0x020c, 0x01ec, 0x01cc, 0x01ac, 0x018c,
      0x0174, 0x0164, 0x0154, 0x0144, 0x0134, 0x0124, 0x0114, 0x0104,
      0x00f4, 0x00e4, 0x00d4, 0x00c4, 0x00b4, 0x00a4, 0x0094, 0x0084,
      0x0078, 0x0070, 0x0068, 0x0060, 0x0058, 0x0050, 0x0048, 0x0040,
      0x0038, 0x0030, 0x0028, 0x0020, 0x0018, 0x0010, 0x0008, 0x0000
};

/* alaw -> signed 16-bit */
static short isdn_audio_alaw_to_s16[] =
{
      0x13fc, 0xec04, 0x0144, 0xfebc, 0x517c, 0xae84, 0x051c, 0xfae4,
      0x0a3c, 0xf5c4, 0x0048, 0xffb8, 0x287c, 0xd784, 0x028c, 0xfd74,
      0x1bfc, 0xe404, 0x01cc, 0xfe34, 0x717c, 0x8e84, 0x071c, 0xf8e4,
      0x0e3c, 0xf1c4, 0x00c4, 0xff3c, 0x387c, 0xc784, 0x039c, 0xfc64,
      0x0ffc, 0xf004, 0x0104, 0xfefc, 0x417c, 0xbe84, 0x041c, 0xfbe4,
      0x083c, 0xf7c4, 0x0008, 0xfff8, 0x207c, 0xdf84, 0x020c, 0xfdf4,
      0x17fc, 0xe804, 0x018c, 0xfe74, 0x617c, 0x9e84, 0x061c, 0xf9e4,
      0x0c3c, 0xf3c4, 0x0084, 0xff7c, 0x307c, 0xcf84, 0x030c, 0xfcf4,
      0x15fc, 0xea04, 0x0164, 0xfe9c, 0x597c, 0xa684, 0x059c, 0xfa64,
      0x0b3c, 0xf4c4, 0x0068, 0xff98, 0x2c7c, 0xd384, 0x02cc, 0xfd34,
      0x1dfc, 0xe204, 0x01ec, 0xfe14, 0x797c, 0x8684, 0x07bc, 0xf844,
      0x0f3c, 0xf0c4, 0x00e4, 0xff1c, 0x3c7c, 0xc384, 0x03dc, 0xfc24,
      0x11fc, 0xee04, 0x0124, 0xfedc, 0x497c, 0xb684, 0x049c, 0xfb64,
      0x093c, 0xf6c4, 0x0028, 0xffd8, 0x247c, 0xdb84, 0x024c, 0xfdb4,
      0x19fc, 0xe604, 0x01ac, 0xfe54, 0x697c, 0x9684, 0x069c, 0xf964,
      0x0d3c, 0xf2c4, 0x00a4, 0xff5c, 0x347c, 0xcb84, 0x034c, 0xfcb4,
      0x12fc, 0xed04, 0x0134, 0xfecc, 0x4d7c, 0xb284, 0x04dc, 0xfb24,
      0x09bc, 0xf644, 0x0038, 0xffc8, 0x267c, 0xd984, 0x026c, 0xfd94,
      0x1afc, 0xe504, 0x01ac, 0xfe54, 0x6d7c, 0x9284, 0x06dc, 0xf924,
      0x0dbc, 0xf244, 0x00b4, 0xff4c, 0x367c, 0xc984, 0x036c, 0xfc94,
      0x0f3c, 0xf0c4, 0x00f4, 0xff0c, 0x3e7c, 0xc184, 0x03dc, 0xfc24,
      0x07bc, 0xf844, 0x0008, 0xfff8, 0x1efc, 0xe104, 0x01ec, 0xfe14,
      0x16fc, 0xe904, 0x0174, 0xfe8c, 0x5d7c, 0xa284, 0x05dc, 0xfa24,
      0x0bbc, 0xf444, 0x0078, 0xff88, 0x2e7c, 0xd184, 0x02ec, 0xfd14,
      0x14fc, 0xeb04, 0x0154, 0xfeac, 0x557c, 0xaa84, 0x055c, 0xfaa4,
      0x0abc, 0xf544, 0x0058, 0xffa8, 0x2a7c, 0xd584, 0x02ac, 0xfd54,
      0x1cfc, 0xe304, 0x01cc, 0xfe34, 0x757c, 0x8a84, 0x075c, 0xf8a4,
      0x0ebc, 0xf144, 0x00d4, 0xff2c, 0x3a7c, 0xc584, 0x039c, 0xfc64,
      0x10fc, 0xef04, 0x0114, 0xfeec, 0x457c, 0xba84, 0x045c, 0xfba4,
      0x08bc, 0xf744, 0x0018, 0xffe8, 0x227c, 0xdd84, 0x022c, 0xfdd4,
      0x18fc, 0xe704, 0x018c, 0xfe74, 0x657c, 0x9a84, 0x065c, 0xf9a4,
      0x0cbc, 0xf344, 0x0094, 0xff6c, 0x327c, 0xcd84, 0x032c, 0xfcd4
};

/* alaw -> ulaw */
static char isdn_audio_alaw_to_ulaw[] =
{
      0xab, 0x2b, 0xe3, 0x63, 0x8b, 0x0b, 0xc9, 0x49,
      0xba, 0x3a, 0xf6, 0x76, 0x9b, 0x1b, 0xd7, 0x57,
      0xa3, 0x23, 0xdd, 0x5d, 0x83, 0x03, 0xc1, 0x41,
      0xb2, 0x32, 0xeb, 0x6b, 0x93, 0x13, 0xcf, 0x4f,
      0xaf, 0x2f, 0xe7, 0x67, 0x8f, 0x0f, 0xcd, 0x4d,
      0xbe, 0x3e, 0xfe, 0x7e, 0x9f, 0x1f, 0xdb, 0x5b,
      0xa7, 0x27, 0xdf, 0x5f, 0x87, 0x07, 0xc5, 0x45,
      0xb6, 0x36, 0xef, 0x6f, 0x97, 0x17, 0xd3, 0x53,
      0xa9, 0x29, 0xe1, 0x61, 0x89, 0x09, 0xc7, 0x47,
      0xb8, 0x38, 0xf2, 0x72, 0x99, 0x19, 0xd5, 0x55,
      0xa1, 0x21, 0xdc, 0x5c, 0x81, 0x01, 0xbf, 0x3f,
      0xb0, 0x30, 0xe9, 0x69, 0x91, 0x11, 0xce, 0x4e,
      0xad, 0x2d, 0xe5, 0x65, 0x8d, 0x0d, 0xcb, 0x4b,
      0xbc, 0x3c, 0xfa, 0x7a, 0x9d, 0x1d, 0xd9, 0x59,
      0xa5, 0x25, 0xde, 0x5e, 0x85, 0x05, 0xc3, 0x43,
      0xb4, 0x34, 0xed, 0x6d, 0x95, 0x15, 0xd1, 0x51,
      0xac, 0x2c, 0xe4, 0x64, 0x8c, 0x0c, 0xca, 0x4a,
      0xbb, 0x3b, 0xf8, 0x78, 0x9c, 0x1c, 0xd8, 0x58,
      0xa4, 0x24, 0xde, 0x5e, 0x84, 0x04, 0xc2, 0x42,
      0xb3, 0x33, 0xec, 0x6c, 0x94, 0x14, 0xd0, 0x50,
      0xb0, 0x30, 0xe8, 0x68, 0x90, 0x10, 0xce, 0x4e,
      0xbf, 0x3f, 0xfe, 0x7e, 0xa0, 0x20, 0xdc, 0x5c,
      0xa8, 0x28, 0xe0, 0x60, 0x88, 0x08, 0xc6, 0x46,
      0xb7, 0x37, 0xf0, 0x70, 0x98, 0x18, 0xd4, 0x54,
      0xaa, 0x2a, 0xe2, 0x62, 0x8a, 0x0a, 0xc8, 0x48,
      0xb9, 0x39, 0xf4, 0x74, 0x9a, 0x1a, 0xd6, 0x56,
      0xa2, 0x22, 0xdd, 0x5d, 0x82, 0x02, 0xc0, 0x40,
      0xb1, 0x31, 0xea, 0x6a, 0x92, 0x12, 0xcf, 0x4f,
      0xae, 0x2e, 0xe6, 0x66, 0x8e, 0x0e, 0xcc, 0x4c,
      0xbd, 0x3d, 0xfc, 0x7c, 0x9e, 0x1e, 0xda, 0x5a,
      0xa6, 0x26, 0xdf, 0x5f, 0x86, 0x06, 0xc4, 0x44,
      0xb5, 0x35, 0xee, 0x6e, 0x96, 0x16, 0xd2, 0x52
};

/* ulaw -> alaw */
static char isdn_audio_ulaw_to_alaw[] =
{
      0xab, 0x55, 0xd5, 0x15, 0x95, 0x75, 0xf5, 0x35,
      0xb5, 0x45, 0xc5, 0x05, 0x85, 0x65, 0xe5, 0x25,
      0xa5, 0x5d, 0xdd, 0x1d, 0x9d, 0x7d, 0xfd, 0x3d,
      0xbd, 0x4d, 0xcd, 0x0d, 0x8d, 0x6d, 0xed, 0x2d,
      0xad, 0x51, 0xd1, 0x11, 0x91, 0x71, 0xf1, 0x31,
      0xb1, 0x41, 0xc1, 0x01, 0x81, 0x61, 0xe1, 0x21,
      0x59, 0xd9, 0x19, 0x99, 0x79, 0xf9, 0x39, 0xb9,
      0x49, 0xc9, 0x09, 0x89, 0x69, 0xe9, 0x29, 0xa9,
      0xd7, 0x17, 0x97, 0x77, 0xf7, 0x37, 0xb7, 0x47,
      0xc7, 0x07, 0x87, 0x67, 0xe7, 0x27, 0xa7, 0xdf,
      0x9f, 0x7f, 0xff, 0x3f, 0xbf, 0x4f, 0xcf, 0x0f,
      0x8f, 0x6f, 0xef, 0x2f, 0x53, 0x13, 0x73, 0x33,
      0xb3, 0x43, 0xc3, 0x03, 0x83, 0x63, 0xe3, 0x23,
      0xa3, 0x5b, 0xdb, 0x1b, 0x9b, 0x7b, 0xfb, 0x3b,
      0xbb, 0xbb, 0x4b, 0x4b, 0xcb, 0xcb, 0x0b, 0x0b,
      0x8b, 0x8b, 0x6b, 0x6b, 0xeb, 0xeb, 0x2b, 0x2b,
      0xab, 0x54, 0xd4, 0x14, 0x94, 0x74, 0xf4, 0x34,
      0xb4, 0x44, 0xc4, 0x04, 0x84, 0x64, 0xe4, 0x24,
      0xa4, 0x5c, 0xdc, 0x1c, 0x9c, 0x7c, 0xfc, 0x3c,
      0xbc, 0x4c, 0xcc, 0x0c, 0x8c, 0x6c, 0xec, 0x2c,
      0xac, 0x50, 0xd0, 0x10, 0x90, 0x70, 0xf0, 0x30,
      0xb0, 0x40, 0xc0, 0x00, 0x80, 0x60, 0xe0, 0x20,
      0x58, 0xd8, 0x18, 0x98, 0x78, 0xf8, 0x38, 0xb8,
      0x48, 0xc8, 0x08, 0x88, 0x68, 0xe8, 0x28, 0xa8,
      0xd6, 0x16, 0x96, 0x76, 0xf6, 0x36, 0xb6, 0x46,
      0xc6, 0x06, 0x86, 0x66, 0xe6, 0x26, 0xa6, 0xde,
      0x9e, 0x7e, 0xfe, 0x3e, 0xbe, 0x4e, 0xce, 0x0e,
      0x8e, 0x6e, 0xee, 0x2e, 0x52, 0x12, 0x72, 0x32,
      0xb2, 0x42, 0xc2, 0x02, 0x82, 0x62, 0xe2, 0x22,
      0xa2, 0x5a, 0xda, 0x1a, 0x9a, 0x7a, 0xfa, 0x3a,
      0xba, 0xba, 0x4a, 0x4a, 0xca, 0xca, 0x0a, 0x0a,
      0x8a, 0x8a, 0x6a, 0x6a, 0xea, 0xea, 0x2a, 0x2a
};

#define NCOEFF            8     /* number of frequencies to be analyzed       */
#define DTMF_TRESH     4000     /* above this is dtmf                         */
#define SILENCE_TRESH   200     /* below this is silence                      */
#define AMP_BITS          9     /* bits per sample, reduced to avoid overflow */
#define LOGRP             0
#define HIGRP             1

/* For DTMF recognition:
 * 2 * cos(2 * PI * k / N) precalculated for all k
 */
static int cos2pik[NCOEFF] =
{
      55813, 53604, 51193, 48591, 38114, 33057, 25889, 18332
};

static char dtmf_matrix[4][4] =
{
      {'1', '2', '3', 'A'},
      {'4', '5', '6', 'B'},
      {'7', '8', '9', 'C'},
      {'*', '0', '#', 'D'}
};

static inline void
isdn_audio_tlookup(const u_char *table, u_char *buff, unsigned long n)
{
#ifdef __i386__
      unsigned long d0, d1, d2, d3;
      __asm__ __volatile__(
            "cld\n"
            "1:\tlodsb\n\t"
            "xlatb\n\t"
            "stosb\n\t"
            "loop 1b\n\t"
      :     "=&b"(d0), "=&c"(d1), "=&D"(d2), "=&S"(d3)
      :     "0"((long) table), "1"(n), "2"((long) buff), "3"((long) buff)
      :     "memory", "ax");
#else
      while (n--)
            *buff = table[*(unsigned char *)buff], buff++;
#endif
}

void
isdn_audio_ulaw2alaw(unsigned char *buff, unsigned long len)
{
      isdn_audio_tlookup(isdn_audio_ulaw_to_alaw, buff, len);
}

void
isdn_audio_alaw2ulaw(unsigned char *buff, unsigned long len)
{
      isdn_audio_tlookup(isdn_audio_alaw_to_ulaw, buff, len);
}

/*
 * linear <-> adpcm conversion stuff
 * Most parts from the mgetty-package.
 * (C) by Gert Doering and Klaus Weidner
 * Used by permission of Gert Doering
 */


#define ZEROTRAP                /* turn on the trap as per the MIL-STD */
#undef ZEROTRAP
#define BIAS 0x84               /* define the add-in bias for 16 bit samples */
#define CLIP 32635

static unsigned char
isdn_audio_linear2ulaw(int sample)
{
      static int 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
      };
      int sign,
       exponent,
       mantissa;
      unsigned char ulawbyte;

      /* Get the sample into sign-magnitude. */
      sign = (sample >> 8) & 0x80;  /* set aside the sign  */
      if (sign != 0)
            sample = -sample; /* get magnitude       */
      if (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
      /* optional CCITT trap */
      if (ulawbyte == 0)
            ulawbyte = 0x02;
#endif
      return (ulawbyte);
}


static int Mx[3][8] =
{
      {0x3800, 0x5600, 0, 0, 0, 0, 0, 0},
      {0x399a, 0x3a9f, 0x4d14, 0x6607, 0, 0, 0, 0},
      {0x3556, 0x3556, 0x399A, 0x3A9F, 0x4200, 0x4D14, 0x6607, 0x6607},
};

static int bitmask[9] =
{
      0, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff
};

static int
isdn_audio_get_bits(adpcm_state * s, unsigned char **in, int *len)
{
      while (s->nleft < s->nbits) {
            int d = *((*in)++);
            (*len)--;
            s->word = (s->word << 8) | d;
            s->nleft += 8;
      }
      s->nleft -= s->nbits;
      return (s->word >> s->nleft) & bitmask[s->nbits];
}

static void
isdn_audio_put_bits(int data, int nbits, adpcm_state * s,
                unsigned char **out, int *len)
{
      s->word = (s->word << nbits) | (data & bitmask[nbits]);
      s->nleft += nbits;
      while (s->nleft >= 8) {
            int d = (s->word >> (s->nleft - 8));
            *(out[0]++) = d & 255;
            (*len)++;
            s->nleft -= 8;
      }
}

adpcm_state *
isdn_audio_adpcm_init(adpcm_state * s, int nbits)
{
      if (!s)
            s = kmalloc(sizeof(adpcm_state), GFP_ATOMIC);
      if (s) {
            s->a = 0;
            s->d = 5;
            s->word = 0;
            s->nleft = 0;
            s->nbits = nbits;
      }
      return s;
}

dtmf_state *
isdn_audio_dtmf_init(dtmf_state * s)
{
      if (!s)
            s = kmalloc(sizeof(dtmf_state), GFP_ATOMIC);
      if (s) {
            s->idx = 0;
            s->last = ' ';
      }
      return s;
}

/*
 * Decompression of adpcm data to a/u-law
 *
 */

int
isdn_audio_adpcm2xlaw(adpcm_state * s, int fmt, unsigned char *in,
                  unsigned char *out, int len)
{
      int a = s->a;
      int d = s->d;
      int nbits = s->nbits;
      int olen = 0;

      while (len) {
            int e = isdn_audio_get_bits(s, &in, &len);
            int sign;

            if (nbits == 4 && e == 0)
                  d = 4;
            sign = (e >> (nbits - 1)) ? -1 : 1;
            e &= bitmask[nbits - 1];
            a += sign * ((e << 1) + 1) * d >> 1;
            if (d & 1)
                  a++;
            if (fmt)
                  *out++ = isdn_audio_ulaw_to_alaw[
                               isdn_audio_linear2ulaw(a << 2)];
            else
                  *out++ = isdn_audio_linear2ulaw(a << 2);
            olen++;
            d = (d * Mx[nbits - 2][e] + 0x2000) >> 14;
            if (d < 5)
                  d = 5;
      }
      s->a = a;
      s->d = d;
      return olen;
}

int
isdn_audio_xlaw2adpcm(adpcm_state * s, int fmt, unsigned char *in,
                  unsigned char *out, int len)
{
      int a = s->a;
      int d = s->d;
      int nbits = s->nbits;
      int olen = 0;

      while (len--) {
            int e = 0,
             nmax = 1 << (nbits - 1);
            int sign,
             delta;

            if (fmt)
                  delta = (isdn_audio_alaw_to_s16[*in++] >> 2) - a;
            else
                  delta = (isdn_audio_ulaw_to_s16[*in++] >> 2) - a;
            if (delta < 0) {
                  e = nmax;
                  delta = -delta;
            }
            while (--nmax && delta > d) {
                  delta -= d;
                  e++;
            }
            if (nbits == 4 && ((e & 0x0f) == 0))
                  e = 8;
            isdn_audio_put_bits(e, nbits, s, &out, &olen);
            sign = (e >> (nbits - 1)) ? -1 : 1;
            e &= bitmask[nbits - 1];

            a += sign * ((e << 1) + 1) * d >> 1;
            if (d & 1)
                  a++;
            d = (d * Mx[nbits - 2][e] + 0x2000) >> 14;
            if (d < 5)
                  d = 5;
      }
      s->a = a;
      s->d = d;
      return olen;
}

/*
 * Goertzel algorithm.
 * See http://ptolemy.eecs.berkeley.edu/~pino/Ptolemy/papers/96/dtmf_ict/
 * for more info.
 * Result is stored into an sk_buff and queued up for later
 * evaluation.
 */
static void
isdn_audio_goertzel(int *sample, modem_info * info)
{
      int sk,
       sk1,
       sk2;
      int k,
       n;
      struct sk_buff *skb;
      int *result;

      skb = dev_alloc_skb(sizeof(int) * NCOEFF);
      if (!skb) {
            printk(KERN_WARNING
              "isdn_audio: Could not alloc DTMF result for ttyI%d\n",
                   info->line);
            return;
      }
      result = (int *) skb_put(skb, sizeof(int) * NCOEFF);
      for (k = 0; k < NCOEFF; k++) {
            sk = sk1 = sk2 = 0;
            for (n = 0; n < DTMF_NPOINTS; n++) {
                  sk = sample[n] + ((cos2pik[k] * sk1) >> 15) - sk2;
                  sk2 = sk1;
                  sk1 = sk;
            }
            /* Avoid overflows */
            sk >>= 1;
            sk2 >>= 1;
            /* compute |X(k)|**2 */
            /* report overflows. This should not happen. */
            /* Comment this out if desired */
            if (sk < -32768 || sk > 32767)
                  printk(KERN_DEBUG
                         "isdn_audio: dtmf goertzel overflow, sk=%d\n", sk);
            if (sk2 < -32768 || sk2 > 32767)
                  printk(KERN_DEBUG
                         "isdn_audio: dtmf goertzel overflow, sk2=%d\n", sk2);
            result[k] =
                ((sk * sk) >> AMP_BITS) -
                ((((cos2pik[k] * sk) >> 15) * sk2) >> AMP_BITS) +
                ((sk2 * sk2) >> AMP_BITS);
      }
      skb_queue_tail(&info->dtmf_queue, skb);
      isdn_timer_ctrl(ISDN_TIMER_MODEMREAD, 1);
}

void
isdn_audio_eval_dtmf(modem_info * info)
{
      struct sk_buff *skb;
      int *result;
      dtmf_state *s;
      int silence;
      int i;
      int di;
      int ch;
      int grp[2];
      char what;
      char *p;
      int thresh;

      while ((skb = skb_dequeue(&info->dtmf_queue))) {
            result = (int *) skb->data;
            s = info->dtmf_state;
            grp[LOGRP] = grp[HIGRP] = -1;
            silence = 0;
            thresh = 0;
            for (i = 0; i < NCOEFF; i++) {
                  if (result[i] > DTMF_TRESH) {
                        if (result[i] > thresh)
                              thresh = result[i];
                  }
                  else if (result[i] < SILENCE_TRESH)
                        silence++;
            }
            if (silence == NCOEFF)
                  what = ' ';
            else {
                  if (thresh > 0)   {
                        thresh = thresh >> 4;  /* touchtones must match within 12 dB */
                        for (i = 0; i < NCOEFF; i++) {
                              if (result[i] < thresh)
                                    continue;  /* ignore */
                              /* good level found. This is allowed only one time per group */
                              if (i < NCOEFF / 2) {
                                    /* lowgroup*/
                                    if (grp[LOGRP] >= 0) {
                                          // Bad. Another tone found. */
                                          grp[LOGRP] = -1;
                                          break;
                                    }
                                    else
                                          grp[LOGRP] = i;
                              }
                              else { /* higroup */
                                    if (grp[HIGRP] >= 0) { // Bad. Another tone found. */
                                          grp[HIGRP] = -1;
                                          break;
                                    }
                                    else
                                          grp[HIGRP] = i - NCOEFF/2;
                              }
                        }
                        if ((grp[LOGRP] >= 0) && (grp[HIGRP] >= 0)) {
                              what = dtmf_matrix[grp[LOGRP]][grp[HIGRP]];
                              if (s->last != ' ' && s->last != '.')
                                    s->last = what;   /* min. 1 non-DTMF between DTMF */
                        } else
                              what = '.';
                  }
                  else
                        what = '.';
            }
            if ((what != s->last) && (what != ' ') && (what != '.')) {
                  printk(KERN_DEBUG "dtmf: tt='%c'\n", what);
                  p = skb->data;
                  *p++ = 0x10;
                  *p = what;
                  skb_trim(skb, 2);
                  ISDN_AUDIO_SKB_DLECOUNT(skb) = 0;
                  ISDN_AUDIO_SKB_LOCK(skb) = 0;
                  di = info->isdn_driver;
                  ch = info->isdn_channel;
                  __skb_queue_tail(&dev->drv[di]->rpqueue[ch], skb);
                  dev->drv[di]->rcvcount[ch] += 2;
                  /* Schedule dequeuing */
                  if ((dev->modempoll) && (info->rcvsched))
                        isdn_timer_ctrl(ISDN_TIMER_MODEMREAD, 1);
                  wake_up_interruptible(&dev->drv[di]->rcv_waitq[ch]);
            } else
                  kfree_skb(skb);
            s->last = what;
      }
}

/*
 * Decode DTMF tones, queue result in separate sk_buf for
 * later examination.
 * Parameters:
 *   s    = pointer to state-struct.
 *   buf  = input audio data
 *   len  = size of audio data.
 *   fmt  = audio data format (0 = ulaw, 1 = alaw)
 */
void
isdn_audio_calc_dtmf(modem_info * info, unsigned char *buf, int len, int fmt)
{
      dtmf_state *s = info->dtmf_state;
      int i;
      int c;

      while (len) {
            c = DTMF_NPOINTS - s->idx;
            if (c > len)
                  c = len;
            if (c <= 0)
                  break;
            for (i = 0; i < c; i++) {
                  if (fmt)
                        s->buf[s->idx++] =
                            isdn_audio_alaw_to_s16[*buf++] >> (15 - AMP_BITS);
                  else
                        s->buf[s->idx++] =
                            isdn_audio_ulaw_to_s16[*buf++] >> (15 - AMP_BITS);
            }
            if (s->idx == DTMF_NPOINTS) {
                  isdn_audio_goertzel(s->buf, info);
                  s->idx = 0;
            }
            len -= c;
      }
}

silence_state *
isdn_audio_silence_init(silence_state * s)
{
      if (!s)
            s = kmalloc(sizeof(silence_state), GFP_ATOMIC);
      if (s) {
            s->idx = 0;
            s->state = 0;
      }
      return s;
}

void
isdn_audio_calc_silence(modem_info * info, unsigned char *buf, int len, int fmt)
{
      silence_state *s = info->silence_state;
      int i;
      signed char c;

      if (!info->emu.vpar[1]) return;

      for (i = 0; i < len; i++) {
            if (fmt)
                c = isdn_audio_alaw_to_ulaw[*buf++];
                  else
                c = *buf++;

            if (c > 0) c -= 128;
            c = abs(c);

            if (c > (info->emu.vpar[1] * 4)) { 
                  s->idx = 0;
                  s->state = 1; 
            } else {
                  if (s->idx < 210000) s->idx++; 
            }
      }
}

void
isdn_audio_put_dle_code(modem_info * info, u_char code)
{
      struct sk_buff *skb;
      int di;
      int ch;
      char *p;

      skb = dev_alloc_skb(2);
      if (!skb) {
            printk(KERN_WARNING
              "isdn_audio: Could not alloc skb for ttyI%d\n",
                   info->line);
            return;
      }
      p = (char *) skb_put(skb, 2);
      p[0] = 0x10;
      p[1] = code;
      ISDN_AUDIO_SKB_DLECOUNT(skb) = 0;
      ISDN_AUDIO_SKB_LOCK(skb) = 0;
      di = info->isdn_driver;
      ch = info->isdn_channel;
      __skb_queue_tail(&dev->drv[di]->rpqueue[ch], skb);
      dev->drv[di]->rcvcount[ch] += 2;
      /* Schedule dequeuing */
      if ((dev->modempoll) && (info->rcvsched))
            isdn_timer_ctrl(ISDN_TIMER_MODEMREAD, 1);
      wake_up_interruptible(&dev->drv[di]->rcv_waitq[ch]);
}

void
isdn_audio_eval_silence(modem_info * info)
{
      silence_state *s = info->silence_state;
      char what;

      what = ' ';

      if (s->idx > (info->emu.vpar[2] * 800)) { 
            s->idx = 0;
            if (!s->state) {  /* silence from beginning of rec */ 
                  what = 's';
            } else {
                  what = 'q';
            }
      }
            if ((what == 's') || (what == 'q')) {
                  printk(KERN_DEBUG "ttyI%d: %s\n", info->line,
                        (what=='s') ? "silence":"quiet");
                  isdn_audio_put_dle_code(info, what);
            } 
}

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