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.
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 #include "g72x.h"
41
42 /*
43 * Maps G.723_24 code word to reconstructed scale factor normalized log
44 * magnitude values.
45 */
46 static short _dqlntab[8] = { -2048, 135, 273, 373, 373, 273, 135, -2048 };
47
48 /* Maps G.723_24 code word to log of scale factor multiplier. */
49 static short _witab[8] = { -128, 960, 4384, 18624, 18624, 4384, 960, -128 };
50
51 /*
52 * Maps G.723_24 code words to a set of values whose long and short
53 * term averages are computed and then compared to give an indication
54 * how stationary (steady state) the signal is.
55 */
56 static short _fitab[8] = { 0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0 };
57
58 static short qtab_723_24[3] = { 8, 218, 331 };
59
60 /*
61 * g723_24_encoder()
62 *
63 * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
64 * Returns -1 if invalid input coding value.
65 */
g723_24_encoder(int sl,int in_coding,struct g72x_state * state_ptr)66 int g723_24_encoder(int sl, int in_coding, struct g72x_state* state_ptr)
67 {
68 short sei, sezi, se, sez; /* ACCUM */
69 short d; /* SUBTA */
70 short y; /* MIX */
71 short sr; /* ADDB */
72 short dqsez; /* ADDC */
73 short dq, i;
74
75 switch (in_coding) { /* linearize input sample to 14-bit PCM */
76 case AUDIO_ENCODING_ALAW:
77 sl = alaw2linear(sl) >> 2;
78 break;
79 case AUDIO_ENCODING_ULAW:
80 sl = ulaw2linear(sl) >> 2;
81 break;
82 case AUDIO_ENCODING_LINEAR:
83 sl >>= 2; /* sl of 14-bit dynamic range */
84 break;
85 default:
86 return (-1);
87 }
88
89 sezi = predictor_zero(state_ptr);
90 sez = sezi >> 1;
91 sei = sezi + predictor_pole(state_ptr);
92 se = sei >> 1; /* se = estimated signal */
93
94 d = sl - se; /* d = estimation diff. */
95
96 /* quantize prediction difference d */
97 y = step_size(state_ptr); /* quantizer step size */
98 i = quantize(d, y, qtab_723_24, 3); /* i = ADPCM code */
99 dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
100
101 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
102
103 dqsez = sr + sez - se; /* pole prediction diff. */
104
105 update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
106
107 return (i);
108 }
109
110 /*
111 * g723_24_decoder()
112 *
113 * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
114 * the resulting 16-bit linear PCM, A-law or u-law sample value.
115 * -1 is returned if the output coding is unknown.
116 */
g723_24_decoder(int i,int out_coding,struct g72x_state * state_ptr)117 int g723_24_decoder(int i, int out_coding, struct g72x_state* state_ptr)
118 {
119 short sezi, sei, sez, se; /* ACCUM */
120 short y; /* MIX */
121 short sr; /* ADDB */
122 short dq;
123 short dqsez;
124
125 i &= 0x07; /* mask to get proper bits */
126 sezi = predictor_zero(state_ptr);
127 sez = sezi >> 1;
128 sei = sezi + predictor_pole(state_ptr);
129 se = sei >> 1; /* se = estimated signal */
130
131 y = step_size(state_ptr); /* adaptive quantizer step size */
132 dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
133
134 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
135
136 dqsez = sr - se + sez; /* pole prediction diff. */
137
138 update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
139
140 switch (out_coding) {
141 case AUDIO_ENCODING_ALAW:
142 return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24));
143 case AUDIO_ENCODING_ULAW:
144 return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24));
145 case AUDIO_ENCODING_LINEAR:
146 return (sr << 2); /* sr was of 14-bit dynamic range */
147 default:
148 return (-1);
149 }
150 }
151