author | Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com> |
Fri, 16 Apr 2010 15:15:52 +0300 | |
changeset 8 | 4a7fac7dd34a |
permissions | -rw-r--r-- |
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/* |
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* This routine converts from linear to ulaw |
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* 29 September 1989 |
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* |
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* Craig Reese: IDA/Supercomputing Research Center |
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* Joe Campbell: Department of Defense |
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* |
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* References: |
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* 1) CCITT Recommendation G.711 (very difficult to follow) |
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* 2) "A New Digital Technique for Implementation of Any |
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* Continuous PCM Companding Law," Villeret, Michel, |
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* et al. 1973 IEEE Int. Conf. on Communications, Vol 1, |
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* 1973, pg. 11.12-11.17 |
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* 3) MIL-STD-188-113,"Interoperability and Performance Standards |
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* for Analog-to_Digital Conversion Techniques," |
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* 17 February 1987 |
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* |
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* Input: Signed 16 bit linear sample |
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* Output: 8 bit ulaw sample |
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*/ |
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|
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#ifdef HAVE_CONFIG_H |
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#include "config.h" |
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#endif |
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#include <glib.h> |
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|
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#undef ZEROTRAP /* turn on the trap as per the MIL-STD */ |
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#define BIAS 0x84 /* define the add-in bias for 16 bit samples */ |
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#define CLIP 32635 |
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|
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void |
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mulaw_encode (gint16 * in, guint8 * out, gint numsamples) |
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{ |
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static gint16 exp_lut[256] = { 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, |
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, |
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, |
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, |
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, |
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, |
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, |
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, |
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7 |
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}; |
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gint16 sign, exponent, mantissa, i; |
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gint16 sample; |
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guint8 ulawbyte; |
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|
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for (i = 0; i < numsamples; i++) { |
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sample = in[i]; |
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/** get the sample into sign-magnitude **/ |
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sign = (sample >> 8) & 0x80; /* set aside the sign */ |
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if (sign != 0) { |
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sample = -sample; /* get magnitude */ |
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} |
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/* sample can be zero because we can overflow in the inversion, |
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* checking against the unsigned version solves this */ |
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if (((guint16) sample) > CLIP) |
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sample = CLIP; /* clip the magnitude */ |
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|
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/** convert from 16 bit linear to ulaw **/ |
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sample = sample + BIAS; |
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exponent = exp_lut[(sample >> 7) & 0xFF]; |
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mantissa = (sample >> (exponent + 3)) & 0x0F; |
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ulawbyte = ~(sign | (exponent << 4) | mantissa); |
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#ifdef ZEROTRAP |
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if (ulawbyte == 0) |
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ulawbyte = 0x02; /* optional CCITT trap */ |
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#endif |
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out[i] = ulawbyte; |
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} |
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} |
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|
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/* |
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* This routine converts from ulaw to 16 bit linear |
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* 29 September 1989 |
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* |
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* Craig Reese: IDA/Supercomputing Research Center |
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* |
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* References: |
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* 1) CCITT Recommendation G.711 (very difficult to follow) |
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* 2) MIL-STD-188-113,"Interoperability and Performance Standards |
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* for Analog-to_Digital Conversion Techniques," |
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* 17 February 1987 |
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* |
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* Input: 8 bit ulaw sample |
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* Output: signed 16 bit linear sample |
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*/ |
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|
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void |
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98 |
mulaw_decode (guint8 * in, gint16 * out, gint numsamples) |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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99 |
{ |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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100 |
static gint16 exp_lut[8] = { 0, 132, 396, 924, 1980, 4092, 8316, 16764 }; |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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101 |
gint16 sign, exponent, mantissa; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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102 |
guint8 ulawbyte; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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103 |
gint16 linear, i; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
diff
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104 |
|
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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105 |
for (i = 0; i < numsamples; i++) { |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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106 |
ulawbyte = in[i]; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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107 |
ulawbyte = ~ulawbyte; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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108 |
sign = (ulawbyte & 0x80); |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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109 |
exponent = (ulawbyte >> 4) & 0x07; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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|
110 |
mantissa = ulawbyte & 0x0F; |
4a7fac7dd34a
Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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|
111 |
linear = exp_lut[exponent] + (mantissa << (exponent + 3)); |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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112 |
if (sign != 0) |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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113 |
linear = -linear; |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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114 |
out[i] = linear; |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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115 |
} |
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Revision: 201011
Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
parents:
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116 |
} |