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1da177e4 LT |
1 | /* |
2 | * Mu-Law conversion Plug-In Interface | |
c1017a4c | 3 | * Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz> |
1da177e4 LT |
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 | ||
1da177e4 LT |
24 | #include <linux/time.h> |
25 | #include <sound/core.h> | |
26 | #include <sound/pcm.h> | |
27 | #include "pcm_plugin.h" | |
28 | ||
29 | #define SIGN_BIT (0x80) /* Sign bit for a u-law byte. */ | |
30 | #define QUANT_MASK (0xf) /* Quantization field mask. */ | |
31 | #define NSEGS (8) /* Number of u-law segments. */ | |
32 | #define SEG_SHIFT (4) /* Left shift for segment number. */ | |
33 | #define SEG_MASK (0x70) /* Segment field mask. */ | |
34 | ||
35 | static inline int val_seg(int val) | |
36 | { | |
37 | int r = 0; | |
38 | val >>= 7; | |
39 | if (val & 0xf0) { | |
40 | val >>= 4; | |
41 | r += 4; | |
42 | } | |
43 | if (val & 0x0c) { | |
44 | val >>= 2; | |
45 | r += 2; | |
46 | } | |
47 | if (val & 0x02) | |
48 | r += 1; | |
49 | return r; | |
50 | } | |
51 | ||
52 | #define BIAS (0x84) /* Bias for linear code. */ | |
53 | ||
54 | /* | |
55 | * linear2ulaw() - Convert a linear PCM value to u-law | |
56 | * | |
57 | * In order to simplify the encoding process, the original linear magnitude | |
58 | * is biased by adding 33 which shifts the encoding range from (0 - 8158) to | |
59 | * (33 - 8191). The result can be seen in the following encoding table: | |
60 | * | |
61 | * Biased Linear Input Code Compressed Code | |
62 | * ------------------------ --------------- | |
63 | * 00000001wxyza 000wxyz | |
64 | * 0000001wxyzab 001wxyz | |
65 | * 000001wxyzabc 010wxyz | |
66 | * 00001wxyzabcd 011wxyz | |
67 | * 0001wxyzabcde 100wxyz | |
68 | * 001wxyzabcdef 101wxyz | |
69 | * 01wxyzabcdefg 110wxyz | |
70 | * 1wxyzabcdefgh 111wxyz | |
71 | * | |
72 | * Each biased linear code has a leading 1 which identifies the segment | |
73 | * number. The value of the segment number is equal to 7 minus the number | |
74 | * of leading 0's. The quantization interval is directly available as the | |
75 | * four bits wxyz. * The trailing bits (a - h) are ignored. | |
76 | * | |
77 | * Ordinarily the complement of the resulting code word is used for | |
78 | * transmission, and so the code word is complemented before it is returned. | |
79 | * | |
80 | * For further information see John C. Bellamy's Digital Telephony, 1982, | |
81 | * John Wiley & Sons, pps 98-111 and 472-476. | |
82 | */ | |
83 | static unsigned char linear2ulaw(int pcm_val) /* 2's complement (16-bit range) */ | |
84 | { | |
85 | int mask; | |
86 | int seg; | |
87 | unsigned char uval; | |
88 | ||
89 | /* Get the sign and the magnitude of the value. */ | |
90 | if (pcm_val < 0) { | |
91 | pcm_val = BIAS - pcm_val; | |
92 | mask = 0x7F; | |
93 | } else { | |
94 | pcm_val += BIAS; | |
95 | mask = 0xFF; | |
96 | } | |
97 | if (pcm_val > 0x7FFF) | |
98 | pcm_val = 0x7FFF; | |
99 | ||
100 | /* Convert the scaled magnitude to segment number. */ | |
101 | seg = val_seg(pcm_val); | |
102 | ||
103 | /* | |
104 | * Combine the sign, segment, quantization bits; | |
105 | * and complement the code word. | |
106 | */ | |
107 | uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF); | |
108 | return uval ^ mask; | |
109 | } | |
110 | ||
111 | /* | |
112 | * ulaw2linear() - Convert a u-law value to 16-bit linear PCM | |
113 | * | |
114 | * First, a biased linear code is derived from the code word. An unbiased | |
115 | * output can then be obtained by subtracting 33 from the biased code. | |
116 | * | |
117 | * Note that this function expects to be passed the complement of the | |
118 | * original code word. This is in keeping with ISDN conventions. | |
119 | */ | |
120 | static int ulaw2linear(unsigned char u_val) | |
121 | { | |
122 | int t; | |
123 | ||
124 | /* Complement to obtain normal u-law value. */ | |
125 | u_val = ~u_val; | |
126 | ||
127 | /* | |
128 | * Extract and bias the quantization bits. Then | |
129 | * shift up by the segment number and subtract out the bias. | |
130 | */ | |
131 | t = ((u_val & QUANT_MASK) << 3) + BIAS; | |
132 | t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT; | |
133 | ||
134 | return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS)); | |
135 | } | |
136 | ||
137 | /* | |
138 | * Basic Mu-Law plugin | |
139 | */ | |
140 | ||
6ac77bc1 TI |
141 | typedef void (*mulaw_f)(struct snd_pcm_plugin *plugin, |
142 | const struct snd_pcm_plugin_channel *src_channels, | |
143 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
144 | snd_pcm_uframes_t frames); |
145 | ||
6ac77bc1 | 146 | struct mulaw_priv { |
1da177e4 | 147 | mulaw_f func; |
9390ec85 TI |
148 | int cvt_endian; /* need endian conversion? */ |
149 | unsigned int native_ofs; /* byte offset in native format */ | |
150 | unsigned int copy_ofs; /* byte offset in s16 format */ | |
151 | unsigned int native_bytes; /* byte size of the native format */ | |
152 | unsigned int copy_bytes; /* bytes to copy per conversion */ | |
153 | u16 flip; /* MSB flip for signedness, done after endian conversion */ | |
6ac77bc1 | 154 | }; |
1da177e4 | 155 | |
9390ec85 TI |
156 | static inline void cvt_s16_to_native(struct mulaw_priv *data, |
157 | unsigned char *dst, u16 sample) | |
158 | { | |
159 | sample ^= data->flip; | |
160 | if (data->cvt_endian) | |
161 | sample = swab16(sample); | |
162 | if (data->native_bytes > data->copy_bytes) | |
163 | memset(dst, 0, data->native_bytes); | |
164 | memcpy(dst + data->native_ofs, (char *)&sample + data->copy_ofs, | |
165 | data->copy_bytes); | |
166 | } | |
167 | ||
6ac77bc1 TI |
168 | static void mulaw_decode(struct snd_pcm_plugin *plugin, |
169 | const struct snd_pcm_plugin_channel *src_channels, | |
170 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
171 | snd_pcm_uframes_t frames) |
172 | { | |
6ac77bc1 | 173 | struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
174 | int channel; |
175 | int nchannels = plugin->src_format.channels; | |
176 | for (channel = 0; channel < nchannels; ++channel) { | |
177 | char *src; | |
178 | char *dst; | |
179 | int src_step, dst_step; | |
180 | snd_pcm_uframes_t frames1; | |
181 | if (!src_channels[channel].enabled) { | |
182 | if (dst_channels[channel].wanted) | |
183 | snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format); | |
184 | dst_channels[channel].enabled = 0; | |
185 | continue; | |
186 | } | |
187 | dst_channels[channel].enabled = 1; | |
188 | src = src_channels[channel].area.addr + src_channels[channel].area.first / 8; | |
189 | dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8; | |
190 | src_step = src_channels[channel].area.step / 8; | |
191 | dst_step = dst_channels[channel].area.step / 8; | |
192 | frames1 = frames; | |
193 | while (frames1-- > 0) { | |
194 | signed short sample = ulaw2linear(*src); | |
9390ec85 | 195 | cvt_s16_to_native(data, dst, sample); |
1da177e4 LT |
196 | src += src_step; |
197 | dst += dst_step; | |
198 | } | |
199 | } | |
200 | } | |
201 | ||
9390ec85 TI |
202 | static inline signed short cvt_native_to_s16(struct mulaw_priv *data, |
203 | unsigned char *src) | |
204 | { | |
205 | u16 sample = 0; | |
206 | memcpy((char *)&sample + data->copy_ofs, src + data->native_ofs, | |
207 | data->copy_bytes); | |
208 | if (data->cvt_endian) | |
209 | sample = swab16(sample); | |
210 | sample ^= data->flip; | |
211 | return (signed short)sample; | |
212 | } | |
213 | ||
6ac77bc1 TI |
214 | static void mulaw_encode(struct snd_pcm_plugin *plugin, |
215 | const struct snd_pcm_plugin_channel *src_channels, | |
216 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
217 | snd_pcm_uframes_t frames) |
218 | { | |
6ac77bc1 | 219 | struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
220 | int channel; |
221 | int nchannels = plugin->src_format.channels; | |
1da177e4 LT |
222 | for (channel = 0; channel < nchannels; ++channel) { |
223 | char *src; | |
224 | char *dst; | |
225 | int src_step, dst_step; | |
226 | snd_pcm_uframes_t frames1; | |
227 | if (!src_channels[channel].enabled) { | |
228 | if (dst_channels[channel].wanted) | |
229 | snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format); | |
230 | dst_channels[channel].enabled = 0; | |
231 | continue; | |
232 | } | |
233 | dst_channels[channel].enabled = 1; | |
234 | src = src_channels[channel].area.addr + src_channels[channel].area.first / 8; | |
235 | dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8; | |
236 | src_step = src_channels[channel].area.step / 8; | |
237 | dst_step = dst_channels[channel].area.step / 8; | |
238 | frames1 = frames; | |
239 | while (frames1-- > 0) { | |
9390ec85 | 240 | signed short sample = cvt_native_to_s16(data, src); |
1da177e4 LT |
241 | *dst = linear2ulaw(sample); |
242 | src += src_step; | |
243 | dst += dst_step; | |
244 | } | |
245 | } | |
246 | } | |
247 | ||
6ac77bc1 TI |
248 | static snd_pcm_sframes_t mulaw_transfer(struct snd_pcm_plugin *plugin, |
249 | const struct snd_pcm_plugin_channel *src_channels, | |
250 | struct snd_pcm_plugin_channel *dst_channels, | |
1da177e4 LT |
251 | snd_pcm_uframes_t frames) |
252 | { | |
6ac77bc1 | 253 | struct mulaw_priv *data; |
1da177e4 | 254 | |
7eaa943c TI |
255 | if (snd_BUG_ON(!plugin || !src_channels || !dst_channels)) |
256 | return -ENXIO; | |
1da177e4 LT |
257 | if (frames == 0) |
258 | return 0; | |
259 | #ifdef CONFIG_SND_DEBUG | |
260 | { | |
261 | unsigned int channel; | |
262 | for (channel = 0; channel < plugin->src_format.channels; channel++) { | |
7eaa943c TI |
263 | if (snd_BUG_ON(src_channels[channel].area.first % 8 || |
264 | src_channels[channel].area.step % 8)) | |
265 | return -ENXIO; | |
266 | if (snd_BUG_ON(dst_channels[channel].area.first % 8 || | |
267 | dst_channels[channel].area.step % 8)) | |
268 | return -ENXIO; | |
1da177e4 LT |
269 | } |
270 | } | |
271 | #endif | |
6ac77bc1 | 272 | data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 LT |
273 | data->func(plugin, src_channels, dst_channels, frames); |
274 | return frames; | |
275 | } | |
276 | ||
fea952e5 | 277 | static void init_data(struct mulaw_priv *data, snd_pcm_format_t format) |
0534ab42 | 278 | { |
0534ab42 | 279 | #ifdef SNDRV_LITTLE_ENDIAN |
9390ec85 | 280 | data->cvt_endian = snd_pcm_format_big_endian(format) > 0; |
0534ab42 | 281 | #else |
9390ec85 | 282 | data->cvt_endian = snd_pcm_format_little_endian(format) > 0; |
0534ab42 | 283 | #endif |
9390ec85 TI |
284 | if (!snd_pcm_format_signed(format)) |
285 | data->flip = 0x8000; | |
286 | data->native_bytes = snd_pcm_format_physical_width(format) / 8; | |
287 | data->copy_bytes = data->native_bytes < 2 ? 1 : 2; | |
288 | if (snd_pcm_format_little_endian(format)) { | |
289 | data->native_ofs = data->native_bytes - data->copy_bytes; | |
290 | data->copy_ofs = 2 - data->copy_bytes; | |
291 | } else { | |
292 | /* S24 in 4bytes need an 1 byte offset */ | |
293 | data->native_ofs = data->native_bytes - | |
294 | snd_pcm_format_width(format) / 8; | |
295 | } | |
0534ab42 TI |
296 | } |
297 | ||
6ac77bc1 TI |
298 | int snd_pcm_plugin_build_mulaw(struct snd_pcm_substream *plug, |
299 | struct snd_pcm_plugin_format *src_format, | |
300 | struct snd_pcm_plugin_format *dst_format, | |
301 | struct snd_pcm_plugin **r_plugin) | |
1da177e4 LT |
302 | { |
303 | int err; | |
6ac77bc1 TI |
304 | struct mulaw_priv *data; |
305 | struct snd_pcm_plugin *plugin; | |
306 | struct snd_pcm_plugin_format *format; | |
1da177e4 LT |
307 | mulaw_f func; |
308 | ||
7eaa943c TI |
309 | if (snd_BUG_ON(!r_plugin)) |
310 | return -ENXIO; | |
1da177e4 LT |
311 | *r_plugin = NULL; |
312 | ||
7eaa943c TI |
313 | if (snd_BUG_ON(src_format->rate != dst_format->rate)) |
314 | return -ENXIO; | |
315 | if (snd_BUG_ON(src_format->channels != dst_format->channels)) | |
316 | return -ENXIO; | |
1da177e4 LT |
317 | |
318 | if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) { | |
319 | format = src_format; | |
320 | func = mulaw_encode; | |
321 | } | |
322 | else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) { | |
323 | format = dst_format; | |
324 | func = mulaw_decode; | |
325 | } | |
326 | else { | |
327 | snd_BUG(); | |
328 | return -EINVAL; | |
329 | } | |
7eaa943c TI |
330 | if (snd_BUG_ON(!snd_pcm_format_linear(format->format))) |
331 | return -ENXIO; | |
1da177e4 LT |
332 | |
333 | err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion", | |
334 | src_format, dst_format, | |
6ac77bc1 | 335 | sizeof(struct mulaw_priv), &plugin); |
1da177e4 LT |
336 | if (err < 0) |
337 | return err; | |
6ac77bc1 | 338 | data = (struct mulaw_priv *)plugin->extra_data; |
1da177e4 | 339 | data->func = func; |
9390ec85 | 340 | init_data(data, format->format); |
1da177e4 LT |
341 | plugin->transfer = mulaw_transfer; |
342 | *r_plugin = plugin; | |
343 | return 0; | |
344 | } |