--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.6pre17/src/oki_adpcm.c	Fri Jun 25 15:50:58 2010 +0200
@@ -0,0 +1,387 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * oki_adpcm.c - Conversion routines between linear 16 bit PCM data and
+ *               OKI (Dialogic) ADPCM format. Supports with the 32kbps
+ *               and 24kbps variants used by Dialogic.
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2001, 2004 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * The actual OKI ADPCM encode and decode method is derived from freely
+ * available code, whose exact origins seem uncertain.
+ *
+ * $Id: oki_adpcm.c,v 1.32 2009/02/10 13:06:46 steveu Exp $
+ */
+
+/*! \file */
+
+#if defined(HAVE_CONFIG_H)
+#include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <string.h>
+
+#include "spandsp/telephony.h"
+#include "spandsp/oki_adpcm.h"
+#include "spandsp/private/oki_adpcm.h"
+
+/* Routines to convert 12 bit linear samples to the Oki ADPCM coding format,
+   widely used in CTI, because Dialogic use it. */
+
+/* OKI ADPCM step variation table */
+static const int16_t step_size[49] =
+{
+       16,    17,    19,    21,    23,    25,    28,    31,
+       34,    37,    41,    45,    50,    55,    60,    66,
+       73,    80,    88,    97,   107,   118,   130,   143,
+      157,   173,   190,   209,   230,   253,   279,   307,
+      337,   371,   408,   449,   494,   544,   598,   658,
+      724,   796,   876,   963,  1060,  1166,  1282,  1411,
+     1552
+};
+
+static const int16_t step_adjustment[8] =
+{
+    -1, -1, -1, -1, 2, 4, 6, 8
+};
+
+/* Band limiting filter, to allow sample rate conversion to and
+   from 6k samples/second. */
+static const float cutoff_coeffs[] =
+{
+    -3.648392e-4f,
+     5.062391e-4f,
+     1.206247e-3f,
+     1.804452e-3f,
+     1.691750e-3f,
+     4.083405e-4f,
+    -1.931085e-3f,
+    -4.452107e-3f,
+    -5.794821e-3f,
+    -4.778489e-3f,
+    -1.161266e-3f,
+     3.928504e-3f,
+     8.259786e-3f,
+     9.500425e-3f,
+     6.512800e-3f,
+     2.227856e-4f,
+    -6.531275e-3f,
+    -1.026843e-2f,
+    -8.718062e-3f,
+    -2.280487e-3f,
+     5.817733e-3f,
+     1.096777e-2f,
+     9.634404e-3f,
+     1.569301e-3f,
+    -9.522632e-3f,
+    -1.748273e-2f,
+    -1.684408e-2f,
+    -6.100054e-3f,
+     1.071206e-2f,
+     2.525209e-2f,
+     2.871779e-2f,
+     1.664411e-2f,
+    -7.706268e-3f,
+    -3.331083e-2f,
+    -4.521249e-2f,
+    -3.085962e-2f,
+     1.373653e-2f,
+     8.089593e-2f,
+     1.529060e-1f,
+     2.080487e-1f,
+     2.286834e-1f,
+     2.080487e-1f,
+     1.529060e-1f,
+     8.089593e-2f,
+     1.373653e-2f,
+    -3.085962e-2f,
+    -4.521249e-2f,
+    -3.331083e-2f,
+    -7.706268e-3f,
+     1.664411e-2f,
+     2.871779e-2f,
+     2.525209e-2f,
+     1.071206e-2f,
+    -6.100054e-3f,
+    -1.684408e-2f,
+    -1.748273e-2f,
+    -9.522632e-3f,
+     1.569301e-3f,
+     9.634404e-3f,
+     1.096777e-2f,
+     5.817733e-3f,
+    -2.280487e-3f,
+    -8.718062e-3f,
+    -1.026843e-2f,
+    -6.531275e-3f,
+     2.227856e-4f,
+     6.512800e-3f,
+     9.500425e-3f,
+     8.259786e-3f,
+     3.928504e-3f,
+    -1.161266e-3f,
+    -4.778489e-3f,
+    -5.794821e-3f,
+    -4.452107e-3f,
+    -1.931085e-3f,
+     4.083405e-4f,
+     1.691750e-3f,
+     1.804452e-3f,
+     1.206247e-3f,
+     5.062391e-4f,
+    -3.648392e-4f
+};
+
+static int16_t decode(oki_adpcm_state_t *s, uint8_t adpcm)
+{
+    int16_t e;
+    int16_t ss;
+    int16_t linear;
+
+    /* Doing the next part as follows:
+     *
+     * x = adpcm & 0x07;
+     * e = (step_size[s->step_index]*(x + x + 1)) >> 3;
+     * 
+     * Seems an obvious improvement on a modern machine, but remember
+     * the truncation errors do not come out the same. It would
+     * not, therefore, be an exact match for what this code is doing.
+     *
+     * Just what a Dialogic card does, I do not know!
+     */
+
+    ss = step_size[s->step_index];
+    e = ss >> 3;
+    if (adpcm & 0x01)
+        e += (ss >> 2);
+    /*endif*/
+    if (adpcm & 0x02)
+        e += (ss >> 1);
+    /*endif*/
+    if (adpcm & 0x04)
+        e += ss;
+    /*endif*/
+    if (adpcm & 0x08)
+        e = -e;
+    /*endif*/
+    linear = s->last + e;
+
+    /* Saturate the values to +/- 2^11 (supposed to be 12 bits) */
+    if (linear > 2047)
+        linear = 2047;
+    else if (linear < -2048)
+        linear = -2048;
+    /*endif*/
+
+    s->last = linear;
+    s->step_index += step_adjustment[adpcm & 0x07];
+    if (s->step_index < 0)
+        s->step_index = 0;
+    else if (s->step_index > 48)
+        s->step_index = 48;
+    /*endif*/
+    /* Note: the result here is a 12 bit value */
+    return linear;
+}
+/*- End of function --------------------------------------------------------*/
+
+static uint8_t encode(oki_adpcm_state_t *s, int16_t linear)
+{
+    int16_t e;
+    int16_t ss;
+    uint8_t adpcm;
+
+    ss = step_size[s->step_index];
+    e = (linear >> 4) - s->last;
+    adpcm = (uint8_t) 0x00;
+    if (e < 0)
+    {
+        adpcm = (uint8_t) 0x08;
+        e = -e;
+    }
+    /*endif*/
+    if (e >= ss)
+    {
+        adpcm |= (uint8_t) 0x04;
+        e -= ss;
+    }
+    /*endif*/
+    if (e >= (ss >> 1))
+    {
+        adpcm |= (uint8_t) 0x02;
+        e -= ss;
+    }
+    /*endif*/
+    if (e >= (ss >> 2))
+        adpcm |= (uint8_t) 0x01;
+    /*endif*/
+
+    /* Use the decoder to set the estimate of the last sample. */
+    /* It also will adjust the step_index for us. */
+    s->last = decode(s, adpcm);
+    return adpcm;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(oki_adpcm_state_t *) oki_adpcm_init(oki_adpcm_state_t *s, int bit_rate)
+{
+    if (bit_rate != 32000  &&  bit_rate != 24000)
+        return NULL;
+    if (s == NULL)
+    {
+        if ((s = (oki_adpcm_state_t *) malloc(sizeof(*s))) == NULL)
+            return  NULL;
+    }
+    memset(s, 0, sizeof(*s));
+    s->bit_rate = bit_rate;
+    
+    return  s;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) oki_adpcm_release(oki_adpcm_state_t *s)
+{
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) oki_adpcm_free(oki_adpcm_state_t *s)
+{
+    free(s);
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) oki_adpcm_decode(oki_adpcm_state_t *s,
+                                   int16_t amp[],
+                                   const uint8_t oki_data[],
+                                   int oki_bytes)
+{
+    int i;
+    int x;
+    int l;
+    int n;
+    int samples;
+    float z;
+
+#if (_MSC_VER >= 1400) 
+    __analysis_assume(s->phase >= 0  &&  s->phase <= 4);
+#endif
+    samples = 0;
+    if (s->bit_rate == 32000)
+    {
+        for (i = 0;  i < oki_bytes;  i++)
+        {
+            amp[samples++] = decode(s, (oki_data[i] >> 4) & 0xF) << 4;
+            amp[samples++] = decode(s, oki_data[i] & 0xF) << 4;
+        }
+        /*endwhile*/
+    }
+    else
+    {
+        n = 0;
+        for (i = 0;  i < oki_bytes;  )
+        {
+            /* 6k to 8k sample/second conversion */
+            if (s->phase)
+            {
+                s->history[s->ptr++] =
+                    decode(s, (n++ & 1)  ?  (oki_data[i++] & 0xF)  :  ((oki_data[i] >> 4) & 0xF)) << 4;
+                s->ptr &= (32 - 1);
+            }
+            /*endif*/
+            z = 0.0f;
+            for (l = 80 - 3 + s->phase, x = s->ptr - 1;  l >= 0;  l -= 4, x--)
+                z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
+            amp[samples++] = (int16_t) (z*4.0f);
+            if (++s->phase > 3)
+                s->phase = 0;
+            /*endif*/
+        }
+        /*endfor*/
+    }
+    /*endif*/
+    return  samples;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) oki_adpcm_encode(oki_adpcm_state_t *s,
+                                   uint8_t oki_data[],
+                                   const int16_t amp[],
+                                   int len)
+{
+    int x;
+    int l;
+    int n;
+    int bytes;
+    float z;
+
+    bytes = 0;
+    if (s->bit_rate == 32000)
+    {
+        for (n = 0;  n < len;  n++)
+        {
+            s->oki_byte = (s->oki_byte << 4) | encode(s, amp[n]);
+            if ((s->mark++ & 1))
+                oki_data[bytes++] = s->oki_byte;
+            /*endif*/
+        }
+        /*endfor*/
+    }
+    else
+    {
+        n = 0;
+        for (;;)
+        {
+            /* 8k to 6k sample/second conversion */
+            if (s->phase > 2)
+            {
+                s->history[s->ptr++] = amp[n];
+                s->ptr &= (32 - 1);
+                s->phase = 0;
+                if (++n >= len)
+                    break;
+                /*endif*/
+            }
+            /*endif*/
+            s->history[s->ptr++] = amp[n];
+            s->ptr &= (32 - 1);
+            z = 0.0f;
+            for (l = 80 - s->phase, x = s->ptr - 1;  l >= 0;  l -= 3, x--)
+                z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
+            /*endfor*/
+            s->oki_byte = (s->oki_byte << 4) | encode(s, (int16_t) (z*3.0f));
+            if ((s->mark++ & 1))
+                oki_data[bytes++] = s->oki_byte;
+            /*endif*/
+            s->phase++;
+            if (++n >= len)
+                break;
+            /*endif*/
+        }
+        /*endfor*/
+    }
+    /*endif*/
+    return  bytes;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/