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
53 /* copy from CCITT G.711 specifications */
54 unsigned char u2a[128] = { /* u- to A-law conversions */
55 1, 1, 2, 2, 3, 3, 4, 4,
56 5, 5, 6, 6, 7, 7, 8, 8,
57 9, 10, 11, 12, 13, 14, 15, 16,
58 17, 18, 19, 20, 21, 22, 23, 24,
59 25, 27, 29, 31, 33, 34, 35, 36,
60 37, 38, 39, 40, 41, 42, 43, 44,
61 46, 48, 49, 50, 51, 52, 53, 54,
62 55, 56, 57, 58, 59, 60, 61, 62,
63 64, 65, 66, 67, 68, 69, 70, 71,
64 72, 73, 74, 75, 76, 77, 78, 79,
65 /* corrected:
66 81, 82, 83, 84, 85, 86, 87, 88,
67 should be: */
68 80, 82, 83, 84, 85, 86, 87, 88,
69 89, 90, 91, 92, 93, 94, 95, 96,
70 97, 98, 99, 100, 101, 102, 103, 104,
71 105, 106, 107, 108, 109, 110, 111, 112,
72 113, 114, 115, 116, 117, 118, 119, 120,
73 121, 122, 123, 124, 125, 126, 127, 128};
74
75 unsigned char a2u[128] = { /* A- to u-law conversions */
76 1, 3, 5, 7, 9, 11, 13, 15,
77 16, 17, 18, 19, 20, 21, 22, 23,
78 24, 25, 26, 27, 28, 29, 30, 31,
79 32, 32, 33, 33, 34, 34, 35, 35,
80 36, 37, 38, 39, 40, 41, 42, 43,
81 44, 45, 46, 47, 48, 48, 49, 49,
82 50, 51, 52, 53, 54, 55, 56, 57,
83 58, 59, 60, 61, 62, 63, 64, 64,
84 65, 66, 67, 68, 69, 70, 71, 72,
85 /* corrected:
86 73, 74, 75, 76, 77, 78, 79, 79,
87 should be: */
88 73, 74, 75, 76, 77, 78, 79, 80,
89
90 80, 81, 82, 83, 84, 85, 86, 87,
91 88, 89, 90, 91, 92, 93, 94, 95,
92 96, 97, 98, 99, 100, 101, 102, 103,
93 104, 105, 106, 107, 108, 109, 110, 111,
94 112, 113, 114, 115, 116, 117, 118, 119,
95 120, 121, 122, 123, 124, 125, 126, 127};
96
97 static int
search(int val,int * table,int size)98 search(
99 int val, //changed from "short" *drago*
100 int * table,
101 int size) //changed from "short" *drago*
102 {
103 int i; //changed from "short" *drago*
104
105 for (i = 0; i < size; i++) {
106 if (val <= *table++)
107 return (i);
108 }
109 return (size);
110 }
111
112 /*
113 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
114 *
115 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
116 *
117 * Linear Input Code Compressed Code
118 * ------------------------ ---------------
119 * 0000000wxyza 000wxyz
120 * 0000001wxyza 001wxyz
121 * 000001wxyzab 010wxyz
122 * 00001wxyzabc 011wxyz
123 * 0001wxyzabcd 100wxyz
124 * 001wxyzabcde 101wxyz
125 * 01wxyzabcdef 110wxyz
126 * 1wxyzabcdefg 111wxyz
127 *
128 * For further information see John C. Bellamy's Digital Telephony, 1982,
129 * John Wiley & Sons, pps 98-111 and 472-476.
130 */
linear2alaw(int pcm_val)131 int linear2alaw(int pcm_val) /* 2's complement (16-bit range) */
132 //changed from "short" *drago*
133 {
134 int mask; //changed from "short" *drago*
135 int seg; //changed from "short" *drago*
136 int aval;
137
138 pcm_val = pcm_val >> 3;
139
140 if (pcm_val >= 0) {
141 mask = 0xD5; /* sign (7th) bit = 1 */
142 } else {
143 mask = 0x55; /* sign bit = 0 */
144 pcm_val = -pcm_val - 1;
145 }
146
147 /* Convert the scaled magnitude to segment number. */
148 seg = search(pcm_val, seg_aend, 8);
149
150 /* Combine the sign, segment, and quantization bits. */
151
152 if (seg >= 8) /* out of range, return maximum value. */
153 return (0x7F ^ mask);
154 else {
155 aval = seg << SEG_SHIFT;
156 if (seg < 2)
157 aval |= (pcm_val >> 1) & QUANT_MASK;
158 else
159 aval |= (pcm_val >> seg) & QUANT_MASK;
160 return (aval ^ mask);
161 }
162 }
163
164 /*
165 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
166 *
167 */
alaw2linear(int a_val)168 int alaw2linear(int a_val)
169 {
170 int t; //changed from "short" *drago*
171 int seg; //changed from "short" *drago*
172
173 a_val ^= 0x55;
174
175 t = (a_val & QUANT_MASK) << 4;
176 seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
177 switch (seg) {
178 case 0:
179 t += 8;
180 break;
181 case 1:
182 t += 0x108;
183 break;
184 default:
185 t += 0x108;
186 t <<= seg - 1;
187 }
188 return ((a_val & SIGN_BIT) ? t : -t);
189 }
190
191 #define BIAS (0x84) /* Bias for linear code. */
192 #define CLIP 8159
193
194 /*
195 * linear2ulaw() - Convert a linear PCM value to u-law
196 *
197 * In order to simplify the encoding process, the original linear magnitude
198 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
199 * (33 - 8191). The result can be seen in the following encoding table:
200 *
201 * Biased Linear Input Code Compressed Code
202 * ------------------------ ---------------
203 * 00000001wxyza 000wxyz
204 * 0000001wxyzab 001wxyz
205 * 000001wxyzabc 010wxyz
206 * 00001wxyzabcd 011wxyz
207 * 0001wxyzabcde 100wxyz
208 * 001wxyzabcdef 101wxyz
209 * 01wxyzabcdefg 110wxyz
210 * 1wxyzabcdefgh 111wxyz
211 *
212 * Each biased linear code has a leading 1 which identifies the segment
213 * number. The value of the segment number is equal to 7 minus the number
214 * of leading 0's. The quantization interval is directly available as the
215 * four bits wxyz. * The trailing bits (a - h) are ignored.
216 *
217 * Ordinarily the complement of the resulting code word is used for
218 * transmission, and so the code word is complemented before it is returned.
219 *
220 * For further information see John C. Bellamy's Digital Telephony, 1982,
221 * John Wiley & Sons, pps 98-111 and 472-476.
222 */
223 /*
224 * Original code has been changed to give results symmetric to 0. Before,
225 * negative values would have a small bias towards zero.
226 * Also, use bit scan operators, if available.
227 */
linear2ulaw(int pcm_val)228 int linear2ulaw( int pcm_val) /* 2's complement (16-bit range) */
229 {
230 int mask;
231 int seg;
232 int uval;
233
234 /* Get the sign and the magnitude of the value. */
235 if (pcm_val < 0) {
236 pcm_val = -pcm_val;
237 mask = 0x7F;
238 } else {
239 mask = 0xFF;
240 }
241
242 if ( pcm_val >= (7904<<2) ) { /* Clipped range + last interval */
243 return (0x7F ^ mask);
244 }
245
246 /* Convert the scaled magnitude to segment number. */
247 #if defined(GCC_HAS_CLZ)
248 seg = 24 - __builtin_clz(pcm_val+131);
249 #elif defined(VC_HAS_BSR)
250 _BitScanReverse(&seg, (pcm_val+131));
251 seg -= 8;
252 #else
253 seg = 0;
254 if( (pcm_val+131) >= 0x100<<3 ) seg = 4;
255 while( (pcm_val+131) >= 0x100<<seg ) seg++;
256 #endif
257
258 /*
259 * Combine the sign, segment, quantization bits;
260 * and complement the code word.
261 */
262 uval = (seg << 4) | (( (pcm_val+131) >> (seg + 3)) & 0xF);
263 return (uval ^ mask);
264
265 }
266
267 /*
268 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
269 *
270 * First, a biased linear code is derived from the code word. An unbiased
271 * output can then be obtained by subtracting 33 from the biased code.
272 *
273 * Note that this function expects to be passed the complement of the
274 * original code word. This is in keeping with ISDN conventions.
275 */
ulaw2linear(int u_val)276 int ulaw2linear( int u_val)
277 {
278 int t;
279
280 /* Complement to obtain normal u-law value. */
281 u_val = ~u_val;
282
283 /*
284 * Extract and bias the quantization bits. Then
285 * shift up by the segment number and subtract out the bias.
286 */
287 t = ((u_val & QUANT_MASK) << 3) + BIAS;
288 t <<= (u_val & SEG_MASK) >> SEG_SHIFT;
289
290 return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
291 }
292
293 /* A-law to u-law conversion */
alaw2ulaw(int aval)294 int alaw2ulaw (int aval)
295 {
296 aval &= 0xff;
297 return ((aval & 0x80) ? (0xFF ^ a2u[aval ^ 0xD5]) :
298 (0x7F ^ a2u[aval ^ 0x55]));
299 }
300
301 /* u-law to A-law conversion */
ulaw2alaw(int uval)302 int ulaw2alaw (int uval)
303 {
304 uval &= 0xff;
305 return ((uval & 0x80) ? (0xD5 ^ (u2a[0xFF ^ uval] - 1)) :
306 (0x55 ^ (u2a[0x7F ^ uval] - 1)));
307 }
308
309
310