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 "g72x.h"
52
53 static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
54 /*
55 * Maps G.721 code word to reconstructed scale factor normalized log
56 * magnitude values.
57 */
58 static short _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
59 425, 373, 323, 273, 213, 135, 4, -2048};
60
61 /* Maps G.721 code word to log of scale factor multiplier. */
62 static short _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
63 1122, 355, 198, 112, 64, 41, 18, -12};
64 /*
65 * Maps G.721 code words to a set of values whose long and short
66 * term averages are computed and then compared to give an indication
67 * how stationary (steady state) the signal is.
68 */
69 static short _fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
70 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
71
72 /*
73 * g721_encoder()
74 *
75 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
76 * the resulting code. -1 is returned for unknown input coding value.
77 */
78 int
g721_encoder(int sl,int in_coding,struct g72x_state * state_ptr)79 g721_encoder(
80 int sl,
81 int in_coding,
82 struct g72x_state *state_ptr)
83 {
84 short sezi, se, sez; /* ACCUM */
85 short d; /* SUBTA */
86 short sr; /* ADDB */
87 short y; /* MIX */
88 short dqsez; /* ADDC */
89 short dq, i;
90
91 switch (in_coding) { /* linearize input sample to 14-bit PCM */
92 case AUDIO_ENCODING_ALAW:
93 sl = alaw2linear(sl) >> 2;
94 break;
95 case AUDIO_ENCODING_ULAW:
96 sl = ulaw2linear(sl) >> 2;
97 break;
98 case AUDIO_ENCODING_LINEAR:
99 sl >>= 2; /* 14-bit dynamic range */
100 break;
101 default:
102 return (-1);
103 }
104
105 sezi = predictor_zero(state_ptr);
106 sez = sezi >> 1;
107 se = (sezi + predictor_pole(state_ptr)) >> 1; /* estimated signal */
108
109 d = sl - se; /* estimation difference */
110
111 /* quantize the prediction difference */
112 y = step_size(state_ptr); /* quantizer step size */
113 i = quantize(d, y, qtab_721, 7); /* i = ADPCM code */
114
115 dq = reconstruct(i & 8, _dqlntab[i], y); /* quantized est diff */
116
117 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconst. signal */
118
119 dqsez = sr + sez - se; /* pole prediction diff. */
120
121 update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
122
123 return (i);
124 }
125
126 /*
127 * g721_decoder()
128 *
129 * Description:
130 *
131 * Decodes a 4-bit code of G.721 encoded data of i and
132 * returns the resulting linear PCM, A-law or u-law value.
133 * return -1 for unknown out_coding value.
134 */
135 int
g721_decoder(int i,int out_coding,struct g72x_state * state_ptr)136 g721_decoder(
137 int i,
138 int out_coding,
139 struct g72x_state *state_ptr)
140 {
141 short sezi, sei, sez, se; /* ACCUM */
142 short y; /* MIX */
143 short sr; /* ADDB */
144 short dq;
145 short dqsez;
146
147 i &= 0x0f; /* mask to get proper bits */
148 sezi = predictor_zero(state_ptr);
149 sez = sezi >> 1;
150 sei = sezi + predictor_pole(state_ptr);
151 se = sei >> 1; /* se = estimated signal */
152
153 y = step_size(state_ptr); /* dynamic quantizer step size */
154
155 dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
156
157 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */
158
159 dqsez = sr - se + sez; /* pole prediction diff. */
160
161 update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
162
163 switch (out_coding) {
164 case AUDIO_ENCODING_ALAW:
165 return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721));
166 case AUDIO_ENCODING_ULAW:
167 return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721));
168 case AUDIO_ENCODING_LINEAR:
169 return (sr << 2); /* sr was 14-bit dynamic range */
170 default:
171 return (-1);
172 }
173 }
174