1 /* This source code is a product of Sun Microsystems, Inc. and is provided
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21 * Sun Microsystems, Inc.
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24 */
25
26 /*
27 * g723_24.c
28 *
29 * Description:
30 *
31 * g723_24_encoder(), g723_24_decoder()
32 *
33 * These routines comprise an implementation of the CCITT G.723 24 Kbps
34 * ADPCM coding algorithm. Essentially, this implementation is identical to
35 * the bit level description except for a few deviations which take advantage
36 * of workstation attributes, such as hardware 2's complement arithmetic.
37 *
38 */
39 #include "sox_i.h"
40 #include "g711.h"
41 #include "g72x.h"
42
43 /*
44 * Maps G.723_24 code word to reconstructed scale factor normalized log
45 * magnitude values.
46 */
47 static const short _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
48
49 /* Maps G.723_24 code word to log of scale factor multiplier. */
50 static const short _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
51
52 /*
53 * Maps G.723_24 code words to a set of values whose long and short
54 * term averages are computed and then compared to give an indication
55 * how stationary (steady state) the signal is.
56 */
57 static const short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
58
59 static const short qtab_723_24[3] = {8, 218, 331};
60
61 /*
62 * g723_24_encoder()
63 *
64 * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
65 * Returns -1 if invalid input coding value.
66 */
g723_24_encoder(int sl,int in_coding,struct g72x_state * state_ptr)67 int g723_24_encoder(int sl, int in_coding, struct g72x_state *state_ptr)
68 {
69 short sei, sezi, se, sez; /* ACCUM */
70 short d; /* SUBTA */
71 short y; /* MIX */
72 short sr; /* ADDB */
73 short dqsez; /* ADDC */
74 short dq, i;
75
76 switch (in_coding) { /* linearize input sample to 14-bit PCM */
77 case AUDIO_ENCODING_ALAW:
78 sl = sox_alaw2linear16(sl) >> 2;
79 break;
80 case AUDIO_ENCODING_ULAW:
81 sl = sox_ulaw2linear16(sl) >> 2;
82 break;
83 case AUDIO_ENCODING_LINEAR:
84 sl >>= 2; /* sl of 14-bit dynamic range */
85 break;
86 default:
87 return (-1);
88 }
89
90 sezi = predictor_zero(state_ptr);
91 sez = sezi >> 1;
92 sei = sezi + predictor_pole(state_ptr);
93 se = sei >> 1; /* se = estimated signal */
94
95 d = sl - se; /* d = estimation diff. */
96
97 /* quantize prediction difference d */
98 y = step_size(state_ptr); /* quantizer step size */
99 i = quantize(d, y, qtab_723_24, 3); /* i = ADPCM code */
100 dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
101
102 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
103
104 dqsez = sr + sez - se; /* pole prediction diff. */
105
106 update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
107
108 return (i);
109 }
110
111 /*
112 * g723_24_decoder()
113 *
114 * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
115 * the resulting 16-bit linear PCM, A-law or u-law sample value.
116 * -1 is returned if the output coding is unknown.
117 */
g723_24_decoder(int i,int out_coding,struct g72x_state * state_ptr)118 int g723_24_decoder(int i, int out_coding, struct g72x_state *state_ptr)
119 {
120 short sezi, sei, sez, se; /* ACCUM */
121 short y; /* MIX */
122 short sr; /* ADDB */
123 short dq;
124 short dqsez;
125
126 i &= 0x07; /* mask to get proper bits */
127 sezi = predictor_zero(state_ptr);
128 sez = sezi >> 1;
129 sei = sezi + predictor_pole(state_ptr);
130 se = sei >> 1; /* se = estimated signal */
131
132 y = step_size(state_ptr); /* adaptive quantizer step size */
133 dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
134
135 sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
136
137 dqsez = sr - se + sez; /* pole prediction diff. */
138
139 update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
140
141 switch (out_coding) {
142 case AUDIO_ENCODING_ALAW:
143 return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24));
144 case AUDIO_ENCODING_ULAW:
145 return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24));
146 case AUDIO_ENCODING_LINEAR:
147 return (sr << 2); /* sr was of 14-bit dynamic range */
148 default:
149 return (-1);
150 }
151 }
152