1 |
3 |
xianfeng |
/*
|
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 <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 |
|
|
|
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,
|
145 |
|
|
snd_pcm_uframes_t frames);
|
146 |
|
|
|
147 |
|
|
struct mulaw_priv {
|
148 |
|
|
mulaw_f func;
|
149 |
|
|
int cvt_endian; /* need endian conversion? */
|
150 |
|
|
unsigned int native_ofs; /* byte offset in native format */
|
151 |
|
|
unsigned int copy_ofs; /* byte offset in s16 format */
|
152 |
|
|
unsigned int native_bytes; /* byte size of the native format */
|
153 |
|
|
unsigned int copy_bytes; /* bytes to copy per conversion */
|
154 |
|
|
u16 flip; /* MSB flip for signedness, done after endian conversion */
|
155 |
|
|
};
|
156 |
|
|
|
157 |
|
|
static inline void cvt_s16_to_native(struct mulaw_priv *data,
|
158 |
|
|
unsigned char *dst, u16 sample)
|
159 |
|
|
{
|
160 |
|
|
sample ^= data->flip;
|
161 |
|
|
if (data->cvt_endian)
|
162 |
|
|
sample = swab16(sample);
|
163 |
|
|
if (data->native_bytes > data->copy_bytes)
|
164 |
|
|
memset(dst, 0, data->native_bytes);
|
165 |
|
|
memcpy(dst + data->native_ofs, (char *)&sample + data->copy_ofs,
|
166 |
|
|
data->copy_bytes);
|
167 |
|
|
}
|
168 |
|
|
|
169 |
|
|
static void mulaw_decode(struct snd_pcm_plugin *plugin,
|
170 |
|
|
const struct snd_pcm_plugin_channel *src_channels,
|
171 |
|
|
struct snd_pcm_plugin_channel *dst_channels,
|
172 |
|
|
snd_pcm_uframes_t frames)
|
173 |
|
|
{
|
174 |
|
|
struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;
|
175 |
|
|
int channel;
|
176 |
|
|
int nchannels = plugin->src_format.channels;
|
177 |
|
|
for (channel = 0; channel < nchannels; ++channel) {
|
178 |
|
|
char *src;
|
179 |
|
|
char *dst;
|
180 |
|
|
int src_step, dst_step;
|
181 |
|
|
snd_pcm_uframes_t frames1;
|
182 |
|
|
if (!src_channels[channel].enabled) {
|
183 |
|
|
if (dst_channels[channel].wanted)
|
184 |
|
|
snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
|
185 |
|
|
dst_channels[channel].enabled = 0;
|
186 |
|
|
continue;
|
187 |
|
|
}
|
188 |
|
|
dst_channels[channel].enabled = 1;
|
189 |
|
|
src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
|
190 |
|
|
dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
|
191 |
|
|
src_step = src_channels[channel].area.step / 8;
|
192 |
|
|
dst_step = dst_channels[channel].area.step / 8;
|
193 |
|
|
frames1 = frames;
|
194 |
|
|
while (frames1-- > 0) {
|
195 |
|
|
signed short sample = ulaw2linear(*src);
|
196 |
|
|
cvt_s16_to_native(data, dst, sample);
|
197 |
|
|
src += src_step;
|
198 |
|
|
dst += dst_step;
|
199 |
|
|
}
|
200 |
|
|
}
|
201 |
|
|
}
|
202 |
|
|
|
203 |
|
|
static inline signed short cvt_native_to_s16(struct mulaw_priv *data,
|
204 |
|
|
unsigned char *src)
|
205 |
|
|
{
|
206 |
|
|
u16 sample = 0;
|
207 |
|
|
memcpy((char *)&sample + data->copy_ofs, src + data->native_ofs,
|
208 |
|
|
data->copy_bytes);
|
209 |
|
|
if (data->cvt_endian)
|
210 |
|
|
sample = swab16(sample);
|
211 |
|
|
sample ^= data->flip;
|
212 |
|
|
return (signed short)sample;
|
213 |
|
|
}
|
214 |
|
|
|
215 |
|
|
static void mulaw_encode(struct snd_pcm_plugin *plugin,
|
216 |
|
|
const struct snd_pcm_plugin_channel *src_channels,
|
217 |
|
|
struct snd_pcm_plugin_channel *dst_channels,
|
218 |
|
|
snd_pcm_uframes_t frames)
|
219 |
|
|
{
|
220 |
|
|
struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;
|
221 |
|
|
int channel;
|
222 |
|
|
int nchannels = plugin->src_format.channels;
|
223 |
|
|
for (channel = 0; channel < nchannels; ++channel) {
|
224 |
|
|
char *src;
|
225 |
|
|
char *dst;
|
226 |
|
|
int src_step, dst_step;
|
227 |
|
|
snd_pcm_uframes_t frames1;
|
228 |
|
|
if (!src_channels[channel].enabled) {
|
229 |
|
|
if (dst_channels[channel].wanted)
|
230 |
|
|
snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
|
231 |
|
|
dst_channels[channel].enabled = 0;
|
232 |
|
|
continue;
|
233 |
|
|
}
|
234 |
|
|
dst_channels[channel].enabled = 1;
|
235 |
|
|
src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
|
236 |
|
|
dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
|
237 |
|
|
src_step = src_channels[channel].area.step / 8;
|
238 |
|
|
dst_step = dst_channels[channel].area.step / 8;
|
239 |
|
|
frames1 = frames;
|
240 |
|
|
while (frames1-- > 0) {
|
241 |
|
|
signed short sample = cvt_native_to_s16(data, src);
|
242 |
|
|
*dst = linear2ulaw(sample);
|
243 |
|
|
src += src_step;
|
244 |
|
|
dst += dst_step;
|
245 |
|
|
}
|
246 |
|
|
}
|
247 |
|
|
}
|
248 |
|
|
|
249 |
|
|
static snd_pcm_sframes_t mulaw_transfer(struct snd_pcm_plugin *plugin,
|
250 |
|
|
const struct snd_pcm_plugin_channel *src_channels,
|
251 |
|
|
struct snd_pcm_plugin_channel *dst_channels,
|
252 |
|
|
snd_pcm_uframes_t frames)
|
253 |
|
|
{
|
254 |
|
|
struct mulaw_priv *data;
|
255 |
|
|
|
256 |
|
|
snd_assert(plugin != NULL && src_channels != NULL && dst_channels != NULL, 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 |
|
|
snd_assert(src_channels[channel].area.first % 8 == 0 &&
|
264 |
|
|
src_channels[channel].area.step % 8 == 0,
|
265 |
|
|
return -ENXIO);
|
266 |
|
|
snd_assert(dst_channels[channel].area.first % 8 == 0 &&
|
267 |
|
|
dst_channels[channel].area.step % 8 == 0,
|
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, int 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 |
|
|
snd_assert(r_plugin != NULL, return -ENXIO);
|
310 |
|
|
*r_plugin = NULL;
|
311 |
|
|
|
312 |
|
|
snd_assert(src_format->rate == dst_format->rate, return -ENXIO);
|
313 |
|
|
snd_assert(src_format->channels == dst_format->channels, return -ENXIO);
|
314 |
|
|
|
315 |
|
|
if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) {
|
316 |
|
|
format = src_format;
|
317 |
|
|
func = mulaw_encode;
|
318 |
|
|
}
|
319 |
|
|
else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) {
|
320 |
|
|
format = dst_format;
|
321 |
|
|
func = mulaw_decode;
|
322 |
|
|
}
|
323 |
|
|
else {
|
324 |
|
|
snd_BUG();
|
325 |
|
|
return -EINVAL;
|
326 |
|
|
}
|
327 |
|
|
snd_assert(snd_pcm_format_linear(format->format) != 0, return -ENXIO);
|
328 |
|
|
|
329 |
|
|
err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion",
|
330 |
|
|
src_format, dst_format,
|
331 |
|
|
sizeof(struct mulaw_priv), &plugin);
|
332 |
|
|
if (err < 0)
|
333 |
|
|
return err;
|
334 |
|
|
data = (struct mulaw_priv *)plugin->extra_data;
|
335 |
|
|
data->func = func;
|
336 |
|
|
init_data(data, format->format);
|
337 |
|
|
plugin->transfer = mulaw_transfer;
|
338 |
|
|
*r_plugin = plugin;
|
339 |
|
|
return 0;
|
340 |
|
|
}
|