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1 | /* |
2 | * Mu-Law conversion Plug-In Interface |
3 | * Copyright (c) 1999 by Jaroslav Kysela <perex@perex.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 <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 | |
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, |
144 | snd_pcm_uframes_t frames); |
145 | |
146 | struct mulaw_priv { |
147 | mulaw_f func; |
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 */ |
154 | }; |
155 | |
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 | |
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, |
171 | snd_pcm_uframes_t frames) |
172 | { |
173 | struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; |
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); |
195 | cvt_s16_to_native(data, dst, sample); |
196 | src += src_step; |
197 | dst += dst_step; |
198 | } |
199 | } |
200 | } |
201 | |
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 | |
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, |
217 | snd_pcm_uframes_t frames) |
218 | { |
219 | struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; |
220 | int channel; |
221 | int nchannels = plugin->src_format.channels; |
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) { |
240 | signed short sample = cvt_native_to_s16(data, src); |
241 | *dst = linear2ulaw(sample); |
242 | src += src_step; |
243 | dst += dst_step; |
244 | } |
245 | } |
246 | } |
247 | |
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, |
251 | snd_pcm_uframes_t frames) |
252 | { |
253 | struct mulaw_priv *data; |
254 | |
255 | if (snd_BUG_ON(!plugin || !src_channels || !dst_channels)) |
256 | return -ENXIO; |
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++) { |
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; |
269 | } |
270 | } |
271 | #endif |
272 | data = (struct mulaw_priv *)plugin->extra_data; |
273 | data->func(plugin, src_channels, dst_channels, frames); |
274 | return frames; |
275 | } |
276 | |
277 | static void init_data(struct mulaw_priv *data, snd_pcm_format_t format) |
278 | { |
279 | #ifdef SNDRV_LITTLE_ENDIAN |
280 | data->cvt_endian = snd_pcm_format_big_endian(format) > 0; |
281 | #else |
282 | data->cvt_endian = snd_pcm_format_little_endian(format) > 0; |
283 | #endif |
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 | } |
296 | } |
297 | |
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) |
302 | { |
303 | int err; |
304 | struct mulaw_priv *data; |
305 | struct snd_pcm_plugin *plugin; |
306 | struct snd_pcm_plugin_format *format; |
307 | mulaw_f func; |
308 | |
309 | if (snd_BUG_ON(!r_plugin)) |
310 | return -ENXIO; |
311 | *r_plugin = NULL; |
312 | |
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; |
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 | } |
330 | if (snd_BUG_ON(!snd_pcm_format_linear(format->format))) |
331 | return -ENXIO; |
332 | |
333 | err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion", |
334 | src_format, dst_format, |
335 | sizeof(struct mulaw_priv), &plugin); |
336 | if (err < 0) |
337 | return err; |
338 | data = (struct mulaw_priv *)plugin->extra_data; |
339 | data->func = func; |
340 | init_data(data, format->format); |
341 | plugin->transfer = mulaw_transfer; |
342 | *r_plugin = plugin; |
343 | return 0; |
344 | } |
345 |
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