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
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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_40.c
29 *
30 * Description:
31 *
32 * g723_40_encoder (), g723_40_decoder ()
33 *
34 * These routines comprise an implementation of the CCITT G.723 40Kbps
35 * ADPCM coding algorithm. Essentially, this implementation is identical to
36 * the bit level description except for a few deviations which
37 * take advantage of workstation attributes, such as hardware 2's
38 * complement arithmetic.
39 *
40 * The deviation from the bit level specification (lookup tables),
41 * preserves the bit level performance specifications.
42 *
43 * As outlined in the G.723 Recommendation, the algorithm is broken
44 * down into modules. Each section of code below is preceded by
45 * the name of the module which it is implementing.
46 *
47 */
48
49 #include "g72x.h"
50 #include "g72x_priv.h"
51
52 /*
53 * Maps G.723_40 code word to ructeconstructed scale factor normalized log
54 * magnitude values.
55 */
56 static short _dqlntab [32] = { -2048, -66, 28, 104, 169, 224, 274, 318,
57 358, 395, 429, 459, 488, 514, 539, 566,
58 566, 539, 514, 488, 459, 429, 395, 358,
59 318, 274, 224, 169, 104, 28, -66, -2048 } ;
60
61 /* Maps G.723_40 code word to log of scale factor multiplier. */
62 static short _witab [32] = { 448, 448, 768, 1248, 1280, 1312, 1856, 3200,
63 4512, 5728, 7008, 8960, 11456, 14080, 16928, 22272,
64 22272, 16928, 14080, 11456, 8960, 7008, 5728, 4512,
65 3200, 1856, 1312, 1280, 1248, 768, 448, 448 } ;
66
67 /*
68 * Maps G.723_40 code words to a set of values whose long and short
69 * term averages are computed and then compared to give an indication
70 * how stationary (steady state) the signal is.
71 */
72 static short _fitab [32] = { 0, 0, 0, 0, 0, 0x200, 0x200, 0x200,
73 0x200, 0x200, 0x400, 0x600, 0x800, 0xA00, 0xC00, 0xC00,
74 0xC00, 0xC00, 0xA00, 0x800, 0x600, 0x400, 0x200, 0x200,
75 0x200, 0x200, 0x200, 0, 0, 0, 0, 0 } ;
76
77 static short qtab_723_40 [15] = { -122, -16, 68, 139, 198, 250, 298, 339,
78 378, 413, 445, 475, 502, 528, 553 } ;
79
80 /*
81 * g723_40_encoder ()
82 *
83 * Encodes a 16-bit linear PCM, A-law or u-law input sample and retuens
84 * the resulting 5-bit CCITT G.723 40Kbps code.
85 * Returns -1 if the input coding value is invalid.
86 */
g723_40_encoder(int sl,G72x_STATE * state_ptr)87 int g723_40_encoder (int sl, G72x_STATE *state_ptr)
88 {
89 short sei, sezi, se, sez ; /* ACCUM */
90 short d ; /* SUBTA */
91 short y ; /* MIX */
92 short sr ; /* ADDB */
93 short dqsez ; /* ADDC */
94 short dq, i ;
95
96 /* linearize input sample to 14-bit PCM */
97 sl >>= 2 ; /* sl of 14-bit dynamic range */
98
99 sezi = predictor_zero (state_ptr) ;
100 sez = sezi >> 1 ;
101 sei = sezi + predictor_pole (state_ptr) ;
102 se = sei >> 1 ; /* se = estimated signal */
103
104 d = sl - se ; /* d = estimation difference */
105
106 /* quantize prediction difference */
107 y = step_size (state_ptr) ; /* adaptive quantizer step size */
108 i = quantize (d, y, qtab_723_40, 15) ; /* i = ADPCM code */
109
110 dq = reconstruct (i & 0x10, _dqlntab [i], y) ; /* quantized diff */
111
112 sr = (dq < 0) ? se - (dq & 0x7FFF) : se + dq ; /* reconstructed signal */
113
114 dqsez = sr + sez - se ; /* dqsez = pole prediction diff. */
115
116 update (5, y, _witab [i], _fitab [i], dq, sr, dqsez, state_ptr) ;
117
118 return i ;
119 }
120
121 /*
122 * g723_40_decoder ()
123 *
124 * Decodes a 5-bit CCITT G.723 40Kbps code and returns
125 * the resulting 16-bit linear PCM, A-law or u-law sample value.
126 * -1 is returned if the output coding is unknown.
127 */
g723_40_decoder(int i,G72x_STATE * state_ptr)128 int g723_40_decoder (int i, G72x_STATE *state_ptr)
129 {
130 short sezi, sei, sez, se ; /* ACCUM */
131 short y ; /* MIX */
132 short sr ; /* ADDB */
133 short dq ;
134 short dqsez ;
135
136 i &= 0x1f ; /* mask to get proper bits */
137 sezi = predictor_zero (state_ptr) ;
138 sez = sezi >> 1 ;
139 sei = sezi + predictor_pole (state_ptr) ;
140 se = sei >> 1 ; /* se = estimated signal */
141
142 y = step_size (state_ptr) ; /* adaptive quantizer step size */
143 dq = reconstruct (i & 0x10, _dqlntab [i], y) ; /* estimation diff. */
144
145 sr = (dq < 0) ? (se - (dq & 0x7FFF)) : (se + dq) ; /* reconst. signal */
146
147 dqsez = sr - se + sez ; /* pole prediction diff. */
148
149 update (5, y, _witab [i], _fitab [i], dq, sr, dqsez, state_ptr) ;
150
151 return arith_shift_left (sr, 2) ; /* sr was of 14-bit dynamic range */
152 }
153
154