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 * g711.c
29 *
30 * u-law, A-law and linear PCM conversions.
31 */
32
33 /*
34 * December 30, 1994:
35 * Functions linear2alaw, linear2ulaw have been updated to correctly
36 * convert unquantized 16 bit values.
37 * Tables for direct u- to A-law and A- to u-law conversions have been
38 * corrected.
39 * Borge Lindberg, Center for PersonKommunikation, Aalborg University.
40 * bli@cpk.auc.dk
41 *
42 */
43
44 #define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
45 #define QUANT_MASK (0xf) /* Quantization field mask. */
46 #define NSEGS (8) /* Number of A-law segments. */
47 #define SEG_SHIFT (4) /* Left shift for segment number. */
48 #define SEG_MASK (0x70) /* Segment field mask. */
49
50 static int seg_aend[8] = {0x1F, 0x3F, 0x7F, 0xFF,
51 0x1FF, 0x3FF, 0x7FF, 0xFFF};
52 static int seg_uend[8] = {0x3F, 0x7F, 0xFF, 0x1FF,
53 0x3FF, 0x7FF, 0xFFF, 0x1FFF};
54
55 /* copy from CCITT G.711 specifications */
56 unsigned char u2a[128] = { /* u- to A-law conversions */
57 1, 1, 2, 2, 3, 3, 4, 4,
58 5, 5, 6, 6, 7, 7, 8, 8,
59 9, 10, 11, 12, 13, 14, 15, 16,
60 17, 18, 19, 20, 21, 22, 23, 24,
61 25, 27, 29, 31, 33, 34, 35, 36,
62 37, 38, 39, 40, 41, 42, 43, 44,
63 46, 48, 49, 50, 51, 52, 53, 54,
64 55, 56, 57, 58, 59, 60, 61, 62,
65 64, 65, 66, 67, 68, 69, 70, 71,
66 72, 73, 74, 75, 76, 77, 78, 79,
67 /* corrected:
68 81, 82, 83, 84, 85, 86, 87, 88,
69 should be: */
70 80, 82, 83, 84, 85, 86, 87, 88,
71 89, 90, 91, 92, 93, 94, 95, 96,
72 97, 98, 99, 100, 101, 102, 103, 104,
73 105, 106, 107, 108, 109, 110, 111, 112,
74 113, 114, 115, 116, 117, 118, 119, 120,
75 121, 122, 123, 124, 125, 126, 127, 128};
76
77 unsigned char a2u[128] = { /* A- to u-law conversions */
78 1, 3, 5, 7, 9, 11, 13, 15,
79 16, 17, 18, 19, 20, 21, 22, 23,
80 24, 25, 26, 27, 28, 29, 30, 31,
81 32, 32, 33, 33, 34, 34, 35, 35,
82 36, 37, 38, 39, 40, 41, 42, 43,
83 44, 45, 46, 47, 48, 48, 49, 49,
84 50, 51, 52, 53, 54, 55, 56, 57,
85 58, 59, 60, 61, 62, 63, 64, 64,
86 65, 66, 67, 68, 69, 70, 71, 72,
87 /* corrected:
88 73, 74, 75, 76, 77, 78, 79, 79,
89 should be: */
90 73, 74, 75, 76, 77, 78, 79, 80,
91
92 80, 81, 82, 83, 84, 85, 86, 87,
93 88, 89, 90, 91, 92, 93, 94, 95,
94 96, 97, 98, 99, 100, 101, 102, 103,
95 104, 105, 106, 107, 108, 109, 110, 111,
96 112, 113, 114, 115, 116, 117, 118, 119,
97 120, 121, 122, 123, 124, 125, 126, 127};
98
99 static int
search(int val,int * table,int size)100 search(
101 int val, /* changed from "short" *drago* */
102 int * table,
103 int size) /* changed from "short" *drago* */
104 {
105 int i; /* changed from "short" *drago* */
106
107 for (i = 0; i < size; i++) {
108 if (val <= *table++)
109 return (i);
110 }
111 return (size);
112 }
113
114 /*
115 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
116 *
117 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
118 *
119 * Linear Input Code Compressed Code
120 * ------------------------ ---------------
121 * 0000000wxyza 000wxyz
122 * 0000001wxyza 001wxyz
123 * 000001wxyzab 010wxyz
124 * 00001wxyzabc 011wxyz
125 * 0001wxyzabcd 100wxyz
126 * 001wxyzabcde 101wxyz
127 * 01wxyzabcdef 110wxyz
128 * 1wxyzabcdefg 111wxyz
129 *
130 * For further information see John C. Bellamy's Digital Telephony, 1982,
131 * John Wiley & Sons, pps 98-111 and 472-476.
132 */
linear2alaw(int pcm_val)133 int linear2alaw(int pcm_val) /* 2's complement (16-bit range) */
134 /* changed from "short" *drago* */
135 {
136 int mask; /* changed from "short" *drago* */
137 int seg; /* changed from "short" *drago* */
138 int aval;
139
140 pcm_val = pcm_val >> 3;
141
142 if (pcm_val >= 0) {
143 mask = 0xD5; /* sign (7th) bit = 1 */
144 } else {
145 mask = 0x55; /* sign bit = 0 */
146 pcm_val = -pcm_val - 1;
147 }
148
149 /* Convert the scaled magnitude to segment number. */
150 seg = search(pcm_val, seg_aend, 8);
151
152 /* Combine the sign, segment, and quantization bits. */
153
154 if (seg >= 8) /* out of range, return maximum value. */
155 return (0x7F ^ mask);
156 else {
157 aval = seg << SEG_SHIFT;
158 if (seg < 2)
159 aval |= (pcm_val >> 1) & QUANT_MASK;
160 else
161 aval |= (pcm_val >> seg) & QUANT_MASK;
162 return (aval ^ mask);
163 }
164 }
165
166 /*
167 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
168 *
169 */
alaw2linear(int a_val)170 int alaw2linear(int a_val)
171 {
172 int t; /* changed from "short" *drago* */
173 int seg; /* changed from "short" *drago* */
174
175 a_val ^= 0x55;
176
177 t = (a_val & QUANT_MASK) << 4;
178 seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
179 switch (seg) {
180 case 0:
181 t += 8;
182 break;
183 case 1:
184 t += 0x108;
185 break;
186 default:
187 t += 0x108;
188 t <<= seg - 1;
189 }
190 return ((a_val & SIGN_BIT) ? t : -t);
191 }
192
193 #define BIAS (0x84) /* Bias for linear code. */
194 #define CLIP 8159
195
196 /*
197 * linear2ulaw() - Convert a linear PCM value to u-law
198 *
199 * In order to simplify the encoding process, the original linear magnitude
200 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
201 * (33 - 8191). The result can be seen in the following encoding table:
202 *
203 * Biased Linear Input Code Compressed Code
204 * ------------------------ ---------------
205 * 00000001wxyza 000wxyz
206 * 0000001wxyzab 001wxyz
207 * 000001wxyzabc 010wxyz
208 * 00001wxyzabcd 011wxyz
209 * 0001wxyzabcde 100wxyz
210 * 001wxyzabcdef 101wxyz
211 * 01wxyzabcdefg 110wxyz
212 * 1wxyzabcdefgh 111wxyz
213 *
214 * Each biased linear code has a leading 1 which identifies the segment
215 * number. The value of the segment number is equal to 7 minus the number
216 * of leading 0's. The quantization interval is directly available as the
217 * four bits wxyz. * The trailing bits (a - h) are ignored.
218 *
219 * Ordinarily the complement of the resulting code word is used for
220 * transmission, and so the code word is complemented before it is returned.
221 *
222 * For further information see John C. Bellamy's Digital Telephony, 1982,
223 * John Wiley & Sons, pps 98-111 and 472-476.
224 */
linear2ulaw(int pcm_val)225 int linear2ulaw( int pcm_val) /* 2's complement (16-bit range) */
226 {
227 int mask;
228 int seg;
229 int uval;
230
231 /* Get the sign and the magnitude of the value. */
232 pcm_val = pcm_val >> 2;
233 if (pcm_val < 0) {
234 pcm_val = -pcm_val;
235 mask = 0x7F;
236 } else {
237 mask = 0xFF;
238 }
239 if ( pcm_val > CLIP ) pcm_val = CLIP; /* clip the magnitude */
240 pcm_val += (BIAS >> 2);
241
242 /* Convert the scaled magnitude to segment number. */
243 seg = search(pcm_val, seg_uend, 8);
244
245 /*
246 * Combine the sign, segment, quantization bits;
247 * and complement the code word.
248 */
249 if (seg >= 8) /* out of range, return maximum value. */
250 return (0x7F ^ mask);
251 else {
252 uval = (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
253 return (uval ^ mask);
254 }
255
256 }
257
258 /*
259 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
260 *
261 * First, a biased linear code is derived from the code word. An unbiased
262 * output can then be obtained by subtracting 33 from the biased code.
263 *
264 * Note that this function expects to be passed the complement of the
265 * original code word. This is in keeping with ISDN conventions.
266 */
ulaw2linear(int u_val)267 int ulaw2linear( int u_val)
268 {
269 int t;
270
271 /* Complement to obtain normal u-law value. */
272 u_val = ~u_val;
273
274 /*
275 * Extract and bias the quantization bits. Then
276 * shift up by the segment number and subtract out the bias.
277 */
278 t = ((u_val & QUANT_MASK) << 3) + BIAS;
279 t <<= (u_val & SEG_MASK) >> SEG_SHIFT;
280
281 return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
282 }
283
284 #if 0
285
286 /* A-law to u-law conversion */
287 static int alaw2ulaw (int aval)
288 {
289 aval &= 0xff;
290 return ((aval & 0x80) ? (0xFF ^ a2u[aval ^ 0xD5]) :
291 (0x7F ^ a2u[aval ^ 0x55]));
292 }
293
294 /* u-law to A-law conversion */
295 static int ulaw2alaw (int uval)
296 {
297 uval &= 0xff;
298 return ((uval & 0x80) ? (0xD5 ^ (u2a[0xFF ^ uval] - 1)) :
299 (0x55 ^ (u2a[0x7F ^ uval] - 1)));
300 }
301
302 #endif
303
304