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
8 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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 * 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 #include "xa_g72x.h"
52
53 #ifdef NOT_USED___WHY
54 static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
55 #endif
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 extern int g72x_predictor_zero();
76 extern int g72x_predictor_pole();
77 extern int g72x_step_size();
78 extern int g72x_reconstruct();
79 extern int g72x_update();
80
81
82 /*
83 * g721_decoder()
84 *
85 * Description:
86 *
87 * Decodes a 4-bit code of G.721 encoded data of i and
88 * returns the resulting linear PCM, A-law or u-law value.
89 * return -1 for unknown out_coding value.
90 */
g721_decoder(i,out_coding,state_ptr)91 int g721_decoder(i,out_coding,state_ptr)
92 int i;
93 int out_coding;
94 struct g72x_state *state_ptr;
95 {
96 short sezi, sei, sez, se; /* ACCUM */
97 short y; /* MIX */
98 short sr; /* ADDB */
99 short dq;
100 short dqsez;
101
102 i &= 0x0f; /* mask to get proper bits */
103 sezi = g72x_predictor_zero(state_ptr);
104 sez = sezi >> 1;
105 sei = sezi + g72x_predictor_pole(state_ptr);
106 se = sei >> 1; /* se = estimated signal */
107
108 y = g72x_step_size(state_ptr); /* dynamic quantizer step size */
109
110 dq = g72x_reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
111
112 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */
113
114 dqsez = sr - se + sez; /* pole prediction diff. */
115
116 g72x_update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
117
118 return (sr << 2); /* sr was 14-bit dynamic range */
119 }
120