02b6c24a05cb27fc2927810426b3a17319d06b80
[Faustine.git] / interpretor / libsndfile-1.0.25 / src / G72x / g723_24.c
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 * 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
41 #include "g72x.h"
42 #include "g72x_priv.h"
43
44 /*
45 * Maps G.723_24 code word to reconstructed scale factor normalized log
46 * magnitude values.
47 */
48 static short _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
49
50 /* Maps G.723_24 code word to log of scale factor multiplier. */
51 static short _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
52
53 /*
54 * Maps G.723_24 code words to a set of values whose long and short
55 * term averages are computed and then compared to give an indication
56 * how stationary (steady state) the signal is.
57 */
58 static short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
59
60 static short qtab_723_24[3] = {8, 218, 331};
61
62 /*
63 * g723_24_encoder()
64 *
65 * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
66 * Returns -1 if invalid input coding value.
67 */
68 int
69 g723_24_encoder(
70 int sl,
71 G72x_STATE *state_ptr)
72 {
73 short sei, sezi, se, sez; /* ACCUM */
74 short d; /* SUBTA */
75 short y; /* MIX */
76 short sr; /* ADDB */
77 short dqsez; /* ADDC */
78 short dq, i;
79
80 /* linearize input sample to 14-bit PCM */
81 sl >>= 2; /* sl of 14-bit dynamic range */
82
83 sezi = predictor_zero(state_ptr);
84 sez = sezi >> 1;
85 sei = sezi + predictor_pole(state_ptr);
86 se = sei >> 1; /* se = estimated signal */
87
88 d = sl - se; /* d = estimation diff. */
89
90 /* quantize prediction difference d */
91 y = step_size(state_ptr); /* quantizer step size */
92 i = quantize(d, y, qtab_723_24, 3); /* i = ADPCM code */
93 dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
94
95 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
96
97 dqsez = sr + sez - se; /* pole prediction diff. */
98
99 update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
100
101 return (i);
102 }
103
104 /*
105 * g723_24_decoder()
106 *
107 * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
108 * the resulting 16-bit linear PCM, A-law or u-law sample value.
109 * -1 is returned if the output coding is unknown.
110 */
111 int
112 g723_24_decoder(
113 int i,
114 G72x_STATE *state_ptr)
115 {
116 short sezi, sei, sez, se; /* ACCUM */
117 short y; /* MIX */
118 short sr; /* ADDB */
119 short dq;
120 short dqsez;
121
122 i &= 0x07; /* mask to get proper bits */
123 sezi = predictor_zero(state_ptr);
124 sez = sezi >> 1;
125 sei = sezi + predictor_pole(state_ptr);
126 se = sei >> 1; /* se = estimated signal */
127
128 y = step_size(state_ptr); /* adaptive quantizer step size */
129 dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
130
131 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
132
133 dqsez = sr - se + sez; /* pole prediction diff. */
134
135 update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
136
137 return (sr << 2); /* sr was of 14-bit dynamic range */
138 }
139