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
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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.
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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 * g721.c
29 *
30 * Description:
31 *
32 * g721_encoder (), g721_decoder ()
33 *
34 * These routines comprise an implementation of the CCITT G.721 ADPCM
35 * coding algorithm. Essentially, this implementation is identical to
36 * the bit level description except for a few deviations which
37 * take advantage of work station attributes, such as hardware 2's
38 * complement arithmetic and large memory. Specifically, certain time
39 * consuming operations such as multiplications are replaced
40 * with lookup tables and software 2's complement operations are
41 * replaced with hardware 2's complement.
42 *
43 * The deviation from the bit level specification (lookup tables)
44 * preserves the bit level performance specifications.
45 *
46 * As outlined in the G.721 Recommendation, the algorithm is broken
47 * down into modules. Each section of code below is preceded by
48 * the name of the module which it is implementing.
49 *
50 */
51
52 #include "g72x.h"
53 #include "g72x_priv.h"
54
55 static short qtab_721 [7] = { -124, 80, 178, 246, 300, 349, 400 } ;
56 /*
57 * Maps G.721 code word to reconstructed scale factor normalized log
58 * magnitude values.
59 */
60 static short _dqlntab [16] = { -2048, 4, 135, 213, 273, 323, 373, 425,
61 425, 373, 323, 273, 213, 135, 4, -2048 } ;
62
63 /* Maps G.721 code word to log of scale factor multiplier. */
64 static short _witab [16] = { -12, 18, 41, 64, 112, 198, 355, 1122,
65 1122, 355, 198, 112, 64, 41, 18, -12 } ;
66 /*
67 * Maps G.721 code words to a set of values whose long and short
68 * term averages are computed and then compared to give an indication
69 * how stationary (steady state) the signal is.
70 */
71 static short _fitab [16] = { 0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
72 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0 } ;
73
74 /*
75 * g721_encoder ()
76 *
77 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
78 * the resulting code. -1 is returned for unknown input coding value.
79 */
80 int
g721_encoder(int sl,G72x_STATE * state_ptr)81 g721_encoder (
82 int sl,
83 G72x_STATE *state_ptr)
84 {
85 short sezi, se, sez ; /* ACCUM */
86 short d ; /* SUBTA */
87 short sr ; /* ADDB */
88 short y ; /* MIX */
89 short dqsez ; /* ADDC */
90 short dq, i ;
91
92 /* linearize input sample to 14-bit PCM */
93 sl >>= 2 ; /* 14-bit dynamic range */
94
95 sezi = predictor_zero (state_ptr) ;
96 sez = sezi >> 1 ;
97 se = (sezi + predictor_pole (state_ptr)) >> 1 ; /* estimated signal */
98
99 d = sl - se ; /* estimation difference */
100
101 /* quantize the prediction difference */
102 y = step_size (state_ptr) ; /* quantizer step size */
103 i = quantize (d, y, qtab_721, 7) ; /* i = ADPCM code */
104
105 dq = reconstruct (i & 8, _dqlntab [i], y) ; /* quantized est diff */
106
107 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq ; /* reconst. signal */
108
109 dqsez = sr + sez - se ; /* pole prediction diff. */
110
111 update (4, y, arith_shift_left (_witab [i], 5), _fitab [i], dq, sr, dqsez, state_ptr) ;
112
113 return i ;
114 }
115
116 /*
117 * g721_decoder ()
118 *
119 * Description:
120 *
121 * Decodes a 4-bit code of G.721 encoded data of i and
122 * returns the resulting linear PCM, A-law or u-law value.
123 * return -1 for unknown out_coding value.
124 */
125 int
g721_decoder(int i,G72x_STATE * state_ptr)126 g721_decoder (
127 int i,
128 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 &= 0x0f ; /* 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) ; /* dynamic quantizer step size */
143
144 dq = reconstruct (i & 0x08, _dqlntab [i], y) ; /* quantized diff. */
145
146 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq ; /* reconst. signal */
147
148 dqsez = sr - se + sez ; /* pole prediction diff. */
149
150 update (4, y, arith_shift_left (_witab [i], 5), _fitab [i], dq, sr, dqsez, state_ptr) ;
151
152 /* sr was 14-bit dynamic range */
153 return arith_shift_left (sr, 2) ;
154 }
155
156