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1da177e4 LT |
1 | /* |
2 | * Mu-Law conversion Plug-In Interface | |
3 | * Copyright (c) 1999 by Jaroslav Kysela <perex@suse.cz> | |
4 | * Uros Bizjak <uros@kss-loka.si> | |
5 | * | |
6 | * Based on reference implementation by Sun Microsystems, Inc. | |
7 | * | |
8 | * This library is free software; you can redistribute it and/or modify | |
9 | * it under the terms of the GNU Library General Public License as | |
10 | * published by the Free Software Foundation; either version 2 of | |
11 | * the License, or (at your option) any later version. | |
12 | * | |
13 | * This program is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | * GNU Library General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU Library General Public | |
19 | * License along with this library; if not, write to the Free Software | |
20 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
21 | * | |
22 | */ | |
23 | ||
24 | #include <sound/driver.h> | |
25 | #include <linux/time.h> | |
26 | #include <sound/core.h> | |
27 | #include <sound/pcm.h> | |
28 | #include "pcm_plugin.h" | |
29 | ||
30 | #define SIGN_BIT (0x80) /* Sign bit for a u-law byte. */ | |
31 | #define QUANT_MASK (0xf) /* Quantization field mask. */ | |
32 | #define NSEGS (8) /* Number of u-law segments. */ | |
33 | #define SEG_SHIFT (4) /* Left shift for segment number. */ | |
34 | #define SEG_MASK (0x70) /* Segment field mask. */ | |
35 | ||
36 | static inline int val_seg(int val) | |
37 | { | |
38 | int r = 0; | |
39 | val >>= 7; | |
40 | if (val & 0xf0) { | |
41 | val >>= 4; | |
42 | r += 4; | |
43 | } | |
44 | if (val & 0x0c) { | |
45 | val >>= 2; | |
46 | r += 2; | |
47 | } | |
48 | if (val & 0x02) | |
49 | r += 1; | |
50 | return r; | |
51 | } | |
52 | ||
53 | #define BIAS (0x84) /* Bias for linear code. */ | |
54 | ||
55 | /* | |
56 | * linear2ulaw() - Convert a linear PCM value to u-law | |
57 | * | |
58 | * In order to simplify the encoding process, the original linear magnitude | |
59 | * is biased by adding 33 which shifts the encoding range from (0 - 8158) to | |
60 | * (33 - 8191). The result can be seen in the following encoding table: | |
61 | * | |
62 | * Biased Linear Input Code Compressed Code | |
63 | * ------------------------ --------------- | |
64 | * 00000001wxyza 000wxyz | |
65 | * 0000001wxyzab 001wxyz | |
66 | * 000001wxyzabc 010wxyz | |
67 | * 00001wxyzabcd 011wxyz | |
68 | * 0001wxyzabcde 100wxyz | |
69 | * 001wxyzabcdef 101wxyz | |
70 | * 01wxyzabcdefg 110wxyz | |
71 | * 1wxyzabcdefgh 111wxyz | |
72 | * | |
73 | * Each biased linear code has a leading 1 which identifies the segment | |
74 | * number. The value of the segment number is equal to 7 minus the number | |
75 | * of leading 0's. The quantization interval is directly available as the | |
76 | * four bits wxyz. * The trailing bits (a - h) are ignored. | |
77 | * | |
78 | * Ordinarily the complement of the resulting code word is used for | |
79 | * transmission, and so the code word is complemented before it is returned. | |
80 | * | |
81 | * For further information see John C. Bellamy's Digital Telephony, 1982, | |
82 | * John Wiley & Sons, pps 98-111 and 472-476. | |
83 | */ | |
84 | static unsigned char linear2ulaw(int pcm_val) /* 2's complement (16-bit range) */ | |
85 | { | |
86 | int mask; | |
87 | int seg; | |
88 | unsigned char uval; | |
89 | ||
90 | /* Get the sign and the magnitude of the value. */ | |
91 | if (pcm_val < 0) { | |
92 | pcm_val = BIAS - pcm_val; | |
93 | mask = 0x7F; | |
94 | } else { | |
95 | pcm_val += BIAS; | |
96 | mask = 0xFF; | |
97 | } | |
98 | if (pcm_val > 0x7FFF) | |
99 | pcm_val = 0x7FFF; | |
100 | ||
101 | /* Convert the scaled magnitude to segment number. */ | |
102 | seg = val_seg(pcm_val); | |
103 | ||
104 | /* | |
105 | * Combine the sign, segment, quantization bits; | |
106 | * and complement the code word. | |
107 | */ | |
108 | uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF); | |
109 | return uval ^ mask; | |
110 | } | |
111 | ||
112 | /* | |
113 | * ulaw2linear() - Convert a u-law value to 16-bit linear PCM | |
114 | * | |
115 | * First, a biased linear code is derived from the code word. An unbiased | |
116 | * output can then be obtained by subtracting 33 from the biased code. | |
117 | * | |
118 | * Note that this function expects to be passed the complement of the | |
119 | * original code word. This is in keeping with ISDN conventions. | |
120 | */ | |
121 | static int ulaw2linear(unsigned char u_val) | |
122 | { | |
123 | int t; | |
124 | ||
125 | /* Complement to obtain normal u-law value. */ | |
126 | u_val = ~u_val; | |
127 | ||
128 | /* | |
129 | * Extract and bias the quantization bits. Then | |
130 | * shift up by the segment number and subtract out the bias. | |
131 | */ | |
132 | t = ((u_val & QUANT_MASK) << 3) + BIAS; | |
133 | t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT; | |
134 | ||
135 | return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS)); | |
136 | } | |
137 | ||
138 | /* | |
139 | * Basic Mu-Law plugin | |
140 | */ | |
141 | ||
6ac77bc1 TI |
142 | typedef void (*mulaw_f)(struct snd_pcm_plugin *plugin, |
143 | const struct snd_pcm_plugin_channel *src_channels, | |
144 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
145 | snd_pcm_uframes_t frames); |
146 | ||
6ac77bc1 | 147 | struct mulaw_priv { |
1da177e4 LT |
148 | mulaw_f func; |
149 | int conv; | |
6ac77bc1 | 150 | }; |
1da177e4 | 151 | |
6ac77bc1 TI |
152 | static void mulaw_decode(struct snd_pcm_plugin *plugin, |
153 | const struct snd_pcm_plugin_channel *src_channels, | |
154 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
155 | snd_pcm_uframes_t frames) |
156 | { | |
157 | #define PUT_S16_LABELS | |
158 | #include "plugin_ops.h" | |
159 | #undef PUT_S16_LABELS | |
6ac77bc1 | 160 | struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
161 | void *put = put_s16_labels[data->conv]; |
162 | int channel; | |
163 | int nchannels = plugin->src_format.channels; | |
164 | for (channel = 0; channel < nchannels; ++channel) { | |
165 | char *src; | |
166 | char *dst; | |
167 | int src_step, dst_step; | |
168 | snd_pcm_uframes_t frames1; | |
169 | if (!src_channels[channel].enabled) { | |
170 | if (dst_channels[channel].wanted) | |
171 | snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format); | |
172 | dst_channels[channel].enabled = 0; | |
173 | continue; | |
174 | } | |
175 | dst_channels[channel].enabled = 1; | |
176 | src = src_channels[channel].area.addr + src_channels[channel].area.first / 8; | |
177 | dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8; | |
178 | src_step = src_channels[channel].area.step / 8; | |
179 | dst_step = dst_channels[channel].area.step / 8; | |
180 | frames1 = frames; | |
181 | while (frames1-- > 0) { | |
182 | signed short sample = ulaw2linear(*src); | |
183 | goto *put; | |
184 | #define PUT_S16_END after | |
185 | #include "plugin_ops.h" | |
186 | #undef PUT_S16_END | |
187 | after: | |
188 | src += src_step; | |
189 | dst += dst_step; | |
190 | } | |
191 | } | |
192 | } | |
193 | ||
6ac77bc1 TI |
194 | static void mulaw_encode(struct snd_pcm_plugin *plugin, |
195 | const struct snd_pcm_plugin_channel *src_channels, | |
196 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
197 | snd_pcm_uframes_t frames) |
198 | { | |
199 | #define GET_S16_LABELS | |
200 | #include "plugin_ops.h" | |
201 | #undef GET_S16_LABELS | |
6ac77bc1 | 202 | struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
203 | void *get = get_s16_labels[data->conv]; |
204 | int channel; | |
205 | int nchannels = plugin->src_format.channels; | |
206 | signed short sample = 0; | |
207 | for (channel = 0; channel < nchannels; ++channel) { | |
208 | char *src; | |
209 | char *dst; | |
210 | int src_step, dst_step; | |
211 | snd_pcm_uframes_t frames1; | |
212 | if (!src_channels[channel].enabled) { | |
213 | if (dst_channels[channel].wanted) | |
214 | snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format); | |
215 | dst_channels[channel].enabled = 0; | |
216 | continue; | |
217 | } | |
218 | dst_channels[channel].enabled = 1; | |
219 | src = src_channels[channel].area.addr + src_channels[channel].area.first / 8; | |
220 | dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8; | |
221 | src_step = src_channels[channel].area.step / 8; | |
222 | dst_step = dst_channels[channel].area.step / 8; | |
223 | frames1 = frames; | |
224 | while (frames1-- > 0) { | |
225 | goto *get; | |
226 | #define GET_S16_END after | |
227 | #include "plugin_ops.h" | |
228 | #undef GET_S16_END | |
229 | after: | |
230 | *dst = linear2ulaw(sample); | |
231 | src += src_step; | |
232 | dst += dst_step; | |
233 | } | |
234 | } | |
235 | } | |
236 | ||
6ac77bc1 TI |
237 | static snd_pcm_sframes_t mulaw_transfer(struct snd_pcm_plugin *plugin, |
238 | const struct snd_pcm_plugin_channel *src_channels, | |
239 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
240 | snd_pcm_uframes_t frames) |
241 | { | |
6ac77bc1 | 242 | struct mulaw_priv *data; |
1da177e4 LT |
243 | |
244 | snd_assert(plugin != NULL && src_channels != NULL && dst_channels != NULL, return -ENXIO); | |
245 | if (frames == 0) | |
246 | return 0; | |
247 | #ifdef CONFIG_SND_DEBUG | |
248 | { | |
249 | unsigned int channel; | |
250 | for (channel = 0; channel < plugin->src_format.channels; channel++) { | |
251 | snd_assert(src_channels[channel].area.first % 8 == 0 && | |
252 | src_channels[channel].area.step % 8 == 0, | |
253 | return -ENXIO); | |
254 | snd_assert(dst_channels[channel].area.first % 8 == 0 && | |
255 | dst_channels[channel].area.step % 8 == 0, | |
256 | return -ENXIO); | |
257 | } | |
258 | } | |
259 | #endif | |
6ac77bc1 | 260 | data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
261 | data->func(plugin, src_channels, dst_channels, frames); |
262 | return frames; | |
263 | } | |
264 | ||
6ac77bc1 TI |
265 | int snd_pcm_plugin_build_mulaw(struct snd_pcm_substream *plug, |
266 | struct snd_pcm_plugin_format *src_format, | |
267 | struct snd_pcm_plugin_format *dst_format, | |
268 | struct snd_pcm_plugin **r_plugin) | |
1da177e4 LT |
269 | { |
270 | int err; | |
6ac77bc1 TI |
271 | struct mulaw_priv *data; |
272 | struct snd_pcm_plugin *plugin; | |
273 | struct snd_pcm_plugin_format *format; | |
1da177e4 LT |
274 | mulaw_f func; |
275 | ||
276 | snd_assert(r_plugin != NULL, return -ENXIO); | |
277 | *r_plugin = NULL; | |
278 | ||
279 | snd_assert(src_format->rate == dst_format->rate, return -ENXIO); | |
280 | snd_assert(src_format->channels == dst_format->channels, return -ENXIO); | |
281 | ||
282 | if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) { | |
283 | format = src_format; | |
284 | func = mulaw_encode; | |
285 | } | |
286 | else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) { | |
287 | format = dst_format; | |
288 | func = mulaw_decode; | |
289 | } | |
290 | else { | |
291 | snd_BUG(); | |
292 | return -EINVAL; | |
293 | } | |
294 | snd_assert(snd_pcm_format_linear(format->format) != 0, return -ENXIO); | |
295 | ||
296 | err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion", | |
297 | src_format, dst_format, | |
6ac77bc1 | 298 | sizeof(struct mulaw_priv), &plugin); |
1da177e4 LT |
299 | if (err < 0) |
300 | return err; | |
6ac77bc1 | 301 | data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
302 | data->func = func; |
303 | data->conv = getput_index(format->format); | |
304 | snd_assert(data->conv >= 0 && data->conv < 4*2*2, return -EINVAL); | |
305 | plugin->transfer = mulaw_transfer; | |
306 | *r_plugin = plugin; | |
307 | return 0; | |
308 | } |