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1 office 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 #include "g711.h"
28  
29 /*
30 * g711.c
31 *
32 * u-law, A-law and linear PCM conversions.
33 */
34 #define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
35 #define QUANT_MASK (0xf) /* Quantization field mask. */
36 #define NSEGS (8) /* Number of A-law segments. */
37 #define SEG_SHIFT (4) /* Left shift for segment number. */
38 #define SEG_MASK (0x70) /* Segment field mask. */
39  
40 static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF,
41 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};
42  
43 /* copy from CCITT G.711 specifications */
44 unsigned char _u2a[128] = { /* u- to A-law conversions */
45 1, 1, 2, 2, 3, 3, 4, 4,
46 5, 5, 6, 6, 7, 7, 8, 8,
47 9, 10, 11, 12, 13, 14, 15, 16,
48 17, 18, 19, 20, 21, 22, 23, 24,
49 25, 27, 29, 31, 33, 34, 35, 36,
50 37, 38, 39, 40, 41, 42, 43, 44,
51 46, 48, 49, 50, 51, 52, 53, 54,
52 55, 56, 57, 58, 59, 60, 61, 62,
53 64, 65, 66, 67, 68, 69, 70, 71,
54 72, 73, 74, 75, 76, 77, 78, 79,
55 81, 82, 83, 84, 85, 86, 87, 88,
56 89, 90, 91, 92, 93, 94, 95, 96,
57 97, 98, 99, 100, 101, 102, 103, 104,
58 105, 106, 107, 108, 109, 110, 111, 112,
59 113, 114, 115, 116, 117, 118, 119, 120,
60 121, 122, 123, 124, 125, 126, 127, 128};
61  
62 unsigned char _a2u[128] = { /* A- to u-law conversions */
63 1, 3, 5, 7, 9, 11, 13, 15,
64 16, 17, 18, 19, 20, 21, 22, 23,
65 24, 25, 26, 27, 28, 29, 30, 31,
66 32, 32, 33, 33, 34, 34, 35, 35,
67 36, 37, 38, 39, 40, 41, 42, 43,
68 44, 45, 46, 47, 48, 48, 49, 49,
69 50, 51, 52, 53, 54, 55, 56, 57,
70 58, 59, 60, 61, 62, 63, 64, 64,
71 65, 66, 67, 68, 69, 70, 71, 72,
72 73, 74, 75, 76, 77, 78, 79, 79,
73 80, 81, 82, 83, 84, 85, 86, 87,
74 88, 89, 90, 91, 92, 93, 94, 95,
75 96, 97, 98, 99, 100, 101, 102, 103,
76 104, 105, 106, 107, 108, 109, 110, 111,
77 112, 113, 114, 115, 116, 117, 118, 119,
78 120, 121, 122, 123, 124, 125, 126, 127};
79  
80 static int
81 search(
82 int val,
83 short *table,
84 int size)
85 {
86 int i;
87  
88 for (i = 0; i < size; i++) {
89 if (val <= *table++)
90 return (i);
91 }
92 return (size);
93 }
94  
95 /*
96 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
97 *
98 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
99 *
100 * Linear Input Code Compressed Code
101 * ------------------------ ---------------
102 * 0000000wxyza 000wxyz
103 * 0000001wxyza 001wxyz
104 * 000001wxyzab 010wxyz
105 * 00001wxyzabc 011wxyz
106 * 0001wxyzabcd 100wxyz
107 * 001wxyzabcde 101wxyz
108 * 01wxyzabcdef 110wxyz
109 * 1wxyzabcdefg 111wxyz
110 *
111 * For further information see John C. Bellamy's Digital Telephony, 1982,
112 * John Wiley & Sons, pps 98-111 and 472-476.
113 */
114 unsigned char
115 linear2alaw(
116 int pcm_val) /* 2's complement (16-bit range) */
117 {
118 int mask;
119 int seg;
120 unsigned char aval;
121 if (pcm_val >= 0) {
122 mask = 0xD5; /* sign (7th) bit = 1 */
123 } else {
124 mask = 0x55; /* sign bit = 0 */
125 pcm_val = -pcm_val - 8;
126 }
127  
128 /* Convert the scaled magnitude to segment number. */
129 seg = search(pcm_val, seg_end, 8);
130  
131 /* Combine the sign, segment, and quantization bits. */
132  
133 if (seg >= 8) /* out of range, return maximum value. */
134 return (0x7F ^ mask);
135 else {
136 aval = seg << SEG_SHIFT;
137 if (seg < 2)
138 aval |= (pcm_val >> 4) & QUANT_MASK;
139 else
140 aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
141 return (aval ^ mask);
142 }
143 }
144  
145 /*
146 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
147 *
148 */
149 int
150 alaw2linear(
151 unsigned char a_val)
152 {
153 int t;
154 int seg;
155 /*printf(" vrednost a_val %X ", a_val);*/
156 a_val ^= 0x55;
157  
158 t = (a_val & QUANT_MASK) << 4;
159 seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
160 switch (seg) {
161 case 0:
162 t += 8;
163 break;
164 case 1:
165 t += 0x108;
166 break;
167 default:
168 t += 0x108;
169 t <<= seg - 1;
170 }
171 /*printf("izracunan int %d in njegov hex %X \n", t,t);*/
172 return ((a_val & SIGN_BIT) ? t : -t);
173 }
174  
175 #define BIAS (0x84) /* Bias for linear code. */
176  
177 /*
178 * linear2ulaw() - Convert a linear PCM value to u-law
179 *
180 * In order to simplify the encoding process, the original linear magnitude
181 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
182 * (33 - 8191). The result can be seen in the following encoding table:
183 *
184 * Biased Linear Input Code Compressed Code
185 * ------------------------ ---------------
186 * 00000001wxyza 000wxyz
187 * 0000001wxyzab 001wxyz
188 * 000001wxyzabc 010wxyz
189 * 00001wxyzabcd 011wxyz
190 * 0001wxyzabcde 100wxyz
191 * 001wxyzabcdef 101wxyz
192 * 01wxyzabcdefg 110wxyz
193 * 1wxyzabcdefgh 111wxyz
194 *
195 * Each biased linear code has a leading 1 which identifies the segment
196 * number. The value of the segment number is equal to 7 minus the number
197 * of leading 0's. The quantization interval is directly available as the
198 * four bits wxyz. * The trailing bits (a - h) are ignored.
199 *
200 * Ordinarily the complement of the resulting code word is used for
201 * transmission, and so the code word is complemented before it is returned.
202 *
203 * For further information see John C. Bellamy's Digital Telephony, 1982,
204 * John Wiley & Sons, pps 98-111 and 472-476.
205 */
206 unsigned char
207 linear2ulaw(
208 int pcm_val) /* 2's complement (16-bit range) */
209 {
210 int mask;
211 int seg;
212 unsigned char uval;
213  
214 /* Get the sign and the magnitude of the value. */
215 if (pcm_val < 0) {
216 pcm_val = BIAS - pcm_val;
217 mask = 0x7F;
218 } else {
219 pcm_val += BIAS;
220 mask = 0xFF;
221 }
222  
223 /* Convert the scaled magnitude to segment number. */
224 seg = search(pcm_val, seg_end, 8);
225  
226 /*
227 * Combine the sign, segment, quantization bits;
228 * and complement the code word.
229 */
230 if (seg >= 8) /* out of range, return maximum value. */
231 return (0x7F ^ mask);
232 else {
233 uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
234 return (uval ^ mask);
235 }
236  
237 }
238  
239 /*
240 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
241 *
242 * First, a biased linear code is derived from the code word. An unbiased
243 * output can then be obtained by subtracting 33 from the biased code.
244 *
245 * Note that this function expects to be passed the complement of the
246 * original code word. This is in keeping with ISDN conventions.
247 */
248 int
249 ulaw2linear(
250 unsigned char u_val)
251 {
252 int t;
253  
254 /* Complement to obtain normal u-law value. */
255 u_val = ~u_val;
256  
257 /*
258 * Extract and bias the quantization bits. Then
259 * shift up by the segment number and subtract out the bias.
260 */
261 t = ((u_val & QUANT_MASK) << 3) + BIAS;
262 t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
263  
264 return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
265 }
266  
267 /* A-law to u-law conversion */
268 /* unsigned char
269 * alaw2ulaw(
270 * unsigned char aval)
271 * {
272 * aval &= 0xff;
273 * return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
274 * (0x7F ^ _a2u[aval ^ 0x55]));
275 * }
276 */
277  
278 /* u-law to A-law conversion */
279 /* unsigned char
280 * ulaw2alaw(
281 * unsigned char uval)
282 * {
283 * uval &= 0xff;
284 * return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
285 * (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
286 * }
287 */
288  
289 /*
290 * Editor modelines - http://www.wireshark.org/tools/modelines.html
291 *
292 * Local variables:
293 * c-basic-offset: 8
294 * tab-width: 8
295 * indent-tabs-mode: t
296 * End:
297 *
298 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
299 * :indentSize=8:tabSize=8:noTabs=false:
300 */