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[/] [or1k_soc_on_altera_embedded_dev_kit/] [trunk/] [linux-2.6/] [linux-2.6.24/] [sound/] [core/] [oss/] [mulaw.c] - Blame information for rev 3

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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.
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 *
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 *   This library is free software; you can redistribute it and/or modify
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 *   it under the terms of the GNU Library General Public License as
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 *   published by the Free Software Foundation; either version 2 of
11
 *   the License, or (at your option) any later version.
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 *
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 *   This program is distributed in the hope that it will be useful,
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 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
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 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 *   GNU Library General Public License for more details.
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 *
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 *   You should have received a copy of the GNU Library General Public
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 *   License along with this library; if not, write to the Free Software
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 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
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 *
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 */
23
 
24
#include <sound/driver.h>
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#include <linux/time.h>
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#include <sound/core.h>
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#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. */
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#define SEG_MASK        (0x70)          /* Segment field mask. */
35
 
36
static inline int val_seg(int val)
37
{
38
        int r = 0;
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        val >>= 7;
40
        if (val & 0xf0) {
41
                val >>= 4;
42
                r += 4;
43
        }
44
        if (val & 0x0c) {
45
                val >>= 2;
46
                r += 2;
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        }
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
 *
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 *      Biased Linear Input Code        Compressed Code
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 *      ------------------------        ---------------
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 *      00000001wxyza                   000wxyz
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 *      0000001wxyzab                   001wxyz
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 *      000001wxyzabc                   010wxyz
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 *      00001wxyzabcd                   011wxyz
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 *      0001wxyzabcde                   100wxyz
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 *      001wxyzabcdef                   101wxyz
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 *      01wxyzabcdefg                   110wxyz
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 *      1wxyzabcdefgh                   111wxyz
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 *
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
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 * 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
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 *
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
}

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