sound/core/oss/mulaw.c

   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
  26 #ifdef CONFIG_SND_PCM_OSS_PLUGINS
  27
  28 #include <linux/time.h>
  29 #include <sound/core.h>
  30 #include <sound/pcm.h>
  31 #include "pcm_plugin.h"
  32
  33 #define SIGN_BIT        (0x80)          /* Sign bit for a u-law byte. */
  34 #define QUANT_MASK      (0xf)           /* Quantization field mask. */
  35 #define NSEGS           (8)             /* Number of u-law segments. */
  36 #define SEG_SHIFT       (4)             /* Left shift for segment number. */
  37 #define SEG_MASK        (0x70)          /* Segment field mask. */
  38
  39 static inline int val_seg(int val)
  40 {
  41         int r = 0;
  42         val >>= 7;
  43         if (val & 0xf0) {
  44                 val >>= 4;
  45                 r += 4;
  46         }
  47         if (val & 0x0c) {
  48                 val >>= 2;
  49                 r += 2;
  50         }
  51         if (val & 0x02)
  52                 r += 1;
  53         return r;
  54 }
  55
  56 #define BIAS            (0x84)          /* Bias for linear code. */
  57
  58 /*
  59  * linear2ulaw() - Convert a linear PCM value to u-law
  60  *
  61  * In order to simplify the encoding process, the original linear magnitude
  62  * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
  63  * (33 - 8191). The result can be seen in the following encoding table:
  64  *
  65  *      Biased Linear Input Code        Compressed Code
  66  *      ------------------------        ---------------
  67  *      00000001wxyza                   000wxyz
  68  *      0000001wxyzab                   001wxyz
  69  *      000001wxyzabc                   010wxyz
  70  *      00001wxyzabcd                   011wxyz
  71  *      0001wxyzabcde                   100wxyz
  72  *      001wxyzabcdef                   101wxyz
  73  *      01wxyzabcdefg                   110wxyz
  74  *      1wxyzabcdefgh                   111wxyz
  75  *
  76  * Each biased linear code has a leading 1 which identifies the segment
  77  * number. The value of the segment number is equal to 7 minus the number
  78  * of leading 0's. The quantization interval is directly available as the
  79  * four bits wxyz.  * The trailing bits (a - h) are ignored.
  80  *
  81  * Ordinarily the complement of the resulting code word is used for
  82  * transmission, and so the code word is complemented before it is returned.
  83  *
  84  * For further information see John C. Bellamy's Digital Telephony, 1982,
  85  * John Wiley & Sons, pps 98-111 and 472-476.
  86  */
  87 static unsigned char linear2ulaw(int pcm_val)   /* 2's complement (16-bit range) */
  88 {
  89         int mask;
  90         int seg;
  91         unsigned char uval;
  92
  93         /* Get the sign and the magnitude of the value. */
  94         if (pcm_val < 0) {
  95                 pcm_val = BIAS - pcm_val;
  96                 mask = 0x7F;
  97         } else {
  98                 pcm_val += BIAS;
  99                 mask = 0xFF;
 100         }
 101         if (pcm_val > 0x7FFF)
 102                 pcm_val = 0x7FFF;
 103
 104         /* Convert the scaled magnitude to segment number. */
 105         seg = val_seg(pcm_val);
 106
 107         /*
 108          * Combine the sign, segment, quantization bits;
 109          * and complement the code word.
 110          */
 111         uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
 112         return uval ^ mask;
 113 }
 114
 115 /*
 116  * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
 117  *
 118  * First, a biased linear code is derived from the code word. An unbiased
 119  * output can then be obtained by subtracting 33 from the biased code.
 120  *
 121  * Note that this function expects to be passed the complement of the
 122  * original code word. This is in keeping with ISDN conventions.
 123  */
 124 static int ulaw2linear(unsigned char u_val)
 125 {
 126         int t;
 127
 128         /* Complement to obtain normal u-law value. */
 129         u_val = ~u_val;
 130
 131         /*
 132          * Extract and bias the quantization bits. Then
 133          * shift up by the segment number and subtract out the bias.
 134          */
 135         t = ((u_val & QUANT_MASK) << 3) + BIAS;
 136         t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
 137
 138         return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
 139 }
 140
 141 /*
 142  *  Basic Mu-Law plugin
 143  */
 144
 145 typedef void (*mulaw_f)(struct snd_pcm_plugin *plugin,
 146                         const struct snd_pcm_plugin_channel *src_channels,
 147                         struct snd_pcm_plugin_channel *dst_channels,
 148                         snd_pcm_uframes_t frames);
 149
 150 struct mulaw_priv {
 151         mulaw_f func;
 152         int conv;
 153 };
 154
 155 static void mulaw_decode(struct snd_pcm_plugin *plugin,
 156                         const struct snd_pcm_plugin_channel *src_channels,
 157                         struct snd_pcm_plugin_channel *dst_channels,
 158                         snd_pcm_uframes_t frames)
 159 {
 160 #define PUT_S16_LABELS
 161 #include "plugin_ops.h"
 162 #undef PUT_S16_LABELS
 163         struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;
 164         void *put = put_s16_labels[data->conv];
 165         int channel;
 166         int nchannels = plugin->src_format.channels;
 167         for (channel = 0; channel < nchannels; ++channel) {
 168                 char *src;
 169                 char *dst;
 170                 int src_step, dst_step;
 171                 snd_pcm_uframes_t frames1;
 172                 if (!src_channels[channel].enabled) {
 173                         if (dst_channels[channel].wanted)
 174                                 snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
 175                         dst_channels[channel].enabled = 0;
 176                         continue;
 177                 }
 178                 dst_channels[channel].enabled = 1;
 179                 src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
 180                 dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
 181                 src_step = src_channels[channel].area.step / 8;
 182                 dst_step = dst_channels[channel].area.step / 8;
 183                 frames1 = frames;
 184                 while (frames1-- > 0) {
 185                         signed short sample = ulaw2linear(*src);
 186                         goto *put;
 187 #define PUT_S16_END after
 188 #include "plugin_ops.h"
 189 #undef PUT_S16_END
 190                 after:
 191                         src += src_step;
 192                         dst += dst_step;
 193                 }
 194         }
 195 }
 196
 197 static void mulaw_encode(struct snd_pcm_plugin *plugin,
 198                         const struct snd_pcm_plugin_channel *src_channels,
 199                         struct snd_pcm_plugin_channel *dst_channels,
 200                         snd_pcm_uframes_t frames)
 201 {
 202 #define GET_S16_LABELS
 203 #include "plugin_ops.h"
 204 #undef GET_S16_LABELS
 205         struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;
 206         void *get = get_s16_labels[data->conv];
 207         int channel;
 208         int nchannels = plugin->src_format.channels;
 209         signed short sample = 0;
 210         for (channel = 0; channel < nchannels; ++channel) {
 211                 char *src;
 212                 char *dst;
 213                 int src_step, dst_step;
 214                 snd_pcm_uframes_t frames1;
 215                 if (!src_channels[channel].enabled) {
 216                         if (dst_channels[channel].wanted)
 217                                 snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
 218                         dst_channels[channel].enabled = 0;
 219                         continue;
 220                 }
 221                 dst_channels[channel].enabled = 1;
 222                 src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
 223                 dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
 224                 src_step = src_channels[channel].area.step / 8;
 225                 dst_step = dst_channels[channel].area.step / 8;
 226                 frames1 = frames;
 227                 while (frames1-- > 0) {
 228                         goto *get;
 229 #define GET_S16_END after
 230 #include "plugin_ops.h"
 231 #undef GET_S16_END
 232                 after:
 233                         *dst = linear2ulaw(sample);
 234                         src += src_step;
 235                         dst += dst_step;
 236                 }
 237         }
 238 }
 239
 240 static snd_pcm_sframes_t mulaw_transfer(struct snd_pcm_plugin *plugin,
 241                               const struct snd_pcm_plugin_channel *src_channels,
 242                               struct snd_pcm_plugin_channel *dst_channels,
 243                               snd_pcm_uframes_t frames)
 244 {
 245         struct mulaw_priv *data;
 246
 247         snd_assert(plugin != NULL && src_channels != NULL && dst_channels != NULL, return -ENXIO);
 248         if (frames == 0)
 249                 return 0;
 250 #ifdef CONFIG_SND_DEBUG
 251         {
 252                 unsigned int channel;
 253                 for (channel = 0; channel < plugin->src_format.channels; channel++) {
 254                         snd_assert(src_channels[channel].area.first % 8 == 0 &&
 255                                    src_channels[channel].area.step % 8 == 0,
 256                                    return -ENXIO);
 257                         snd_assert(dst_channels[channel].area.first % 8 == 0 &&
 258                                    dst_channels[channel].area.step % 8 == 0,
 259                                    return -ENXIO);
 260                 }
 261         }
 262 #endif
 263         data = (struct mulaw_priv *)plugin->extra_data;
 264         data->func(plugin, src_channels, dst_channels, frames);
 265         return frames;
 266 }
 267
 268 static int getput_index(int format)
 269 {
 270         int sign, width, endian;
 271         sign = !snd_pcm_format_signed(format);
 272         width = snd_pcm_format_width(format) / 8 - 1;
 273         if (width < 0 || width > 3) {
 274                 snd_printk(KERN_ERR "snd-pcm-oss: invalid format %d\n", format);
 275                 width = 0;
 276         }
 277 #ifdef SNDRV_LITTLE_ENDIAN
 278         endian = snd_pcm_format_big_endian(format);
 279 #else
 280         endian = snd_pcm_format_little_endian(format);
 281 #endif
 282         if (endian < 0)
 283                 endian = 0;
 284         return width * 4 + endian * 2 + sign;
 285 }
 286
 287 int snd_pcm_plugin_build_mulaw(struct snd_pcm_substream *plug,
 288                                struct snd_pcm_plugin_format *src_format,
 289                                struct snd_pcm_plugin_format *dst_format,
 290                                struct snd_pcm_plugin **r_plugin)
 291 {
 292         int err;
 293         struct mulaw_priv *data;
 294         struct snd_pcm_plugin *plugin;
 295         struct snd_pcm_plugin_format *format;
 296         mulaw_f func;
 297
 298         snd_assert(r_plugin != NULL, return -ENXIO);
 299         *r_plugin = NULL;
 300
 301         snd_assert(src_format->rate == dst_format->rate, return -ENXIO);
 302         snd_assert(src_format->channels == dst_format->channels, return -ENXIO);
 303
 304         if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) {
 305                 format = src_format;
 306                 func = mulaw_encode;
 307         }
 308         else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) {
 309                 format = dst_format;
 310                 func = mulaw_decode;
 311         }
 312         else {
 313                 snd_BUG();
 314                 return -EINVAL;
 315         }
 316         snd_assert(snd_pcm_format_linear(format->format) != 0, return -ENXIO);
 317
 318         err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion",
 319                                    src_format, dst_format,
 320                                    sizeof(struct mulaw_priv), &plugin);
 321         if (err < 0)
 322                 return err;
 323         data = (struct mulaw_priv *)plugin->extra_data;
 324         data->func = func;
 325         data->conv = getput_index(format->format);
 326         snd_assert(data->conv >= 0 && data->conv < 4*2*2, return -EINVAL);
 327         plugin->transfer = mulaw_transfer;
 328         *r_plugin = plugin;
 329         return 0;
 330 }
 331
 332 #endif