1 /*
2 * This source code is a product of Sun Microsystems, Inc. and is provided
3 * for unrestricted use. Users may copy or modify this source code without
4 * charge.
5 *
6 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
7 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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9 *
10 * Sun source code is provided with no support and without any obligation on
11 * the part of Sun Microsystems, Inc. to assist in its use, correction,
12 * modification or enhancement.
13 *
14 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
15 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
16 * OR ANY PART THEREOF.
17 *
18 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
19 * or profits or other special, indirect and consequential damages, even if
20 * Sun has been advised of the possibility of such damages.
21 *
22 * Sun Microsystems, Inc.
23 * 2550 Garcia Avenue
24 * Mountain View, California 94043
25 */
26
27 /*
28 * g723_24.c
29 *
30 * Description:
31 *
32 * g723_24_encoder (), g723_24_decoder ()
33 *
34 * These routines comprise an implementation of the CCITT G.723 24 Kbps
35 * ADPCM coding algorithm. Essentially, this implementation is identical to
36 * the bit level description except for a few deviations which take advantage
37 * of workstation attributes, such as hardware 2's complement arithmetic.
38 *
39 */
40
41 #include "g72x.h"
42 #include "g72x_priv.h"
43
44 /*
45 * Maps G.723_24 code word to reconstructed scale factor normalized log
46 * magnitude values.
47 */
48 static short _dqlntab [8] = { -2048, 135, 273, 373, 373, 273, 135, -2048 } ;
49
50 /* Maps G.723_24 code word to log of scale factor multiplier. */
51 static short _witab [8] = { -128, 960, 4384, 18624, 18624, 4384, 960, -128 } ;
52
53 /*
54 * Maps G.723_24 code words to a set of values whose long and short
55 * term averages are computed and then compared to give an indication
56 * how stationary (steady state) the signal is.
57 */
58 static short _fitab [8] = { 0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0 } ;
59
60 static short qtab_723_24 [3] = { 8, 218, 331 } ;
61
62 /*
63 * g723_24_encoder ()
64 *
65 * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
66 * Returns -1 if invalid input coding value.
67 */
68 int
g723_24_encoder(int sl,G72x_STATE * state_ptr)69 g723_24_encoder (
70 int sl,
71 G72x_STATE *state_ptr)
72 {
73 short sei, sezi, se, sez ; /* ACCUM */
74 short d ; /* SUBTA */
75 short y ; /* MIX */
76 short sr ; /* ADDB */
77 short dqsez ; /* ADDC */
78 short dq, i ;
79
80 /* linearize input sample to 14-bit PCM */
81 sl >>= 2 ; /* sl of 14-bit dynamic range */
82
83 sezi = predictor_zero (state_ptr) ;
84 sez = sezi >> 1 ;
85 sei = sezi + predictor_pole (state_ptr) ;
86 se = sei >> 1 ; /* se = estimated signal */
87
88 d = sl - se ; /* d = estimation diff. */
89
90 /* quantize prediction difference d */
91 y = step_size (state_ptr) ; /* quantizer step size */
92 i = quantize (d, y, qtab_723_24, 3) ; /* i = ADPCM code */
93 dq = reconstruct (i & 4, _dqlntab [i], y) ; /* quantized diff. */
94
95 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq ; /* reconstructed signal */
96
97 dqsez = sr + sez - se ; /* pole prediction diff. */
98
99 update (3, y, _witab [i], _fitab [i], dq, sr, dqsez, state_ptr) ;
100
101 return i ;
102 }
103
104 /*
105 * g723_24_decoder ()
106 *
107 * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
108 * the resulting 16-bit linear PCM, A-law or u-law sample value.
109 * -1 is returned if the output coding is unknown.
110 */
111 int
g723_24_decoder(int i,G72x_STATE * state_ptr)112 g723_24_decoder (
113 int i,
114 G72x_STATE *state_ptr)
115 {
116 short sezi, sei, sez, se ; /* ACCUM */
117 short y ; /* MIX */
118 short sr ; /* ADDB */
119 short dq ;
120 short dqsez ;
121
122 i &= 0x07 ; /* mask to get proper bits */
123 sezi = predictor_zero (state_ptr) ;
124 sez = sezi >> 1 ;
125 sei = sezi + predictor_pole (state_ptr) ;
126 se = sei >> 1 ; /* se = estimated signal */
127
128 y = step_size (state_ptr) ; /* adaptive quantizer step size */
129 dq = reconstruct (i & 0x04, _dqlntab [i], y) ; /* unquantize pred diff */
130
131 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq) ; /* reconst. signal */
132
133 dqsez = sr - se + sez ; /* pole prediction diff. */
134
135 update (3, y, _witab [i], _fitab [i], dq, sr, dqsez, state_ptr) ;
136
137 return arith_shift_left (sr, 2) ; /* sr was of 14-bit dynamic range */
138 }
139
140