src/pcm/pcm_mulaw.c

   1 /**
   2  * \file pcm/pcm_mulaw.c
   3  * \ingroup PCM_Plugins
   4  * \brief PCM Mu-Law Conversion Plugin Interface
   5  * \author Abramo Bagnara <abramo@alsa-project.org>
   6  * \date 2000-2001
   7  */
   8 /*
   9  *  PCM - Mu-Law conversion
  10  *  Copyright (c) 2000 by Abramo Bagnara <abramo@alsa-project.org>
  11  *
  12  *
  13  *   This library is free software; you can redistribute it and/or modify
  14  *   it under the terms of the GNU Lesser General Public License as
  15  *   published by the Free Software Foundation; either version 2.1 of
  16  *   the License, or (at your option) any later version.
  17  *
  18  *   This program is distributed in the hope that it will be useful,
  19  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  *   GNU Lesser General Public License for more details.
  22  *
  23  *   You should have received a copy of the GNU Lesser General Public
  24  *   License along with this library; if not, write to the Free Software
  25  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  26  *
  27  */
  28
  29 #include <byteswap.h>
  30 #include "pcm_local.h"
  31 #include "pcm_plugin.h"
  32
  33 #include "plugin_ops.h"
  34
  35 #ifndef PIC
  36 /* entry for static linking */
  37 const char *_snd_module_pcm_mulaw = "";
  38 #endif
  39
  40 #ifndef DOC_HIDDEN
  41
  42 typedef void (*mulaw_f)(const snd_pcm_channel_area_t *src_areas,
  43                         snd_pcm_uframes_t src_offset,
  44                         const snd_pcm_channel_area_t *dst_areas,
  45                         snd_pcm_uframes_t dst_offset,
  46                         unsigned int channels, snd_pcm_uframes_t frames,
  47                         unsigned int getputidx);
  48
  49 typedef struct {
  50         /* This field need to be the first */
  51         snd_pcm_plugin_t plug;
  52         unsigned int getput_idx;
  53         mulaw_f func;
  54         snd_pcm_format_t sformat;
  55 } snd_pcm_mulaw_t;
  56
  57 #endif
  58
  59 static inline int val_seg(int val)
  60 {
  61         int r = 0;
  62         val >>= 7;
  63         if (val & 0xf0) {
  64                 val >>= 4;
  65                 r += 4;
  66         }
  67         if (val & 0x0c) {
  68                 val >>= 2;
  69                 r += 2;
  70         }
  71         if (val & 0x02)
  72                 r += 1;
  73         return r;
  74 }
  75
  76 /*
  77  * s16_to_ulaw() - Convert a linear PCM value to u-law
  78  *
  79  * In order to simplify the encoding process, the original linear magnitude
  80  * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
  81  * (33 - 8191). The result can be seen in the following encoding table:
  82  *
  83  *      Biased Linear Input Code        Compressed Code
  84  *      ------------------------        ---------------
  85  *      00000001wxyza                   000wxyz
  86  *      0000001wxyzab                   001wxyz
  87  *      000001wxyzabc                   010wxyz
  88  *      00001wxyzabcd                   011wxyz
  89  *      0001wxyzabcde                   100wxyz
  90  *      001wxyzabcdef                   101wxyz
  91  *      01wxyzabcdefg                   110wxyz
  92  *      1wxyzabcdefgh                   111wxyz
  93  *
  94  * Each biased linear code has a leading 1 which identifies the segment
  95  * number. The value of the segment number is equal to 7 minus the number
  96  * of leading 0's. The quantization interval is directly available as the
  97  * four bits wxyz.  * The trailing bits (a - h) are ignored.
  98  *
  99  * Ordinarily the complement of the resulting code word is used for
 100  * transmission, and so the code word is complemented before it is returned.
 101  *
 102  * For further information see John C. Bellamy's Digital Telephony, 1982,
 103  * John Wiley & Sons, pps 98-111 and 472-476.
 104  */
 105
 106 static unsigned char s16_to_ulaw(int pcm_val)   /* 2's complement (16-bit range) */
 107 {
 108         int mask;
 109         int seg;
 110         unsigned char uval;
 111
 112         if (pcm_val < 0) {
 113                 pcm_val = 0x84 - pcm_val;
 114                 mask = 0x7f;
 115         } else {
 116                 pcm_val += 0x84;
 117                 mask = 0xff;
 118         }
 119         if (pcm_val > 0x7fff)
 120                 pcm_val = 0x7fff;
 121
 122         /* Convert the scaled magnitude to segment number. */
 123         seg = val_seg(pcm_val);
 124
 125         /*
 126          * Combine the sign, segment, quantization bits;
 127          * and complement the code word.
 128          */
 129         uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0x0f);
 130         return uval ^ mask;
 131 }
 132
 133 /*
 134  * ulaw_to_s16() - Convert a u-law value to 16-bit linear PCM
 135  *
 136  * First, a biased linear code is derived from the code word. An unbiased
 137  * output can then be obtained by subtracting 33 from the biased code.
 138  *
 139  * Note that this function expects to be passed the complement of the
 140  * original code word. This is in keeping with ISDN conventions.
 141  */
 142 static int ulaw_to_s16(unsigned char u_val)
 143 {
 144         int t;
 145
 146         /* Complement to obtain normal u-law value. */
 147         u_val = ~u_val;
 148
 149         /*
 150          * Extract and bias the quantization bits. Then
 151          * shift up by the segment number and subtract out the bias.
 152          */
 153         t = ((u_val & 0x0f) << 3) + 0x84;
 154         t <<= (u_val & 0x70) >> 4;
 155
 156         return ((u_val & 0x80) ? (0x84 - t) : (t - 0x84));
 157 }
 158
 159 #ifndef DOC_HIDDEN
 160
 161 void snd_pcm_mulaw_decode(const snd_pcm_channel_area_t *dst_areas,
 162                           snd_pcm_uframes_t dst_offset,
 163                           const snd_pcm_channel_area_t *src_areas,
 164                           snd_pcm_uframes_t src_offset,
 165                           unsigned int channels, snd_pcm_uframes_t frames,
 166                           unsigned int putidx)
 167 {
 168 #define PUT16_LABELS
 169 #include "plugin_ops.h"
 170 #undef PUT16_LABELS
 171         void *put = put16_labels[putidx];
 172         unsigned int channel;
 173         for (channel = 0; channel < channels; ++channel) {
 174                 const unsigned char *src;
 175                 char *dst;
 176                 int src_step, dst_step;
 177                 snd_pcm_uframes_t frames1;
 178                 const snd_pcm_channel_area_t *src_area = &src_areas[channel];
 179                 const snd_pcm_channel_area_t *dst_area = &dst_areas[channel];
 180                 src = snd_pcm_channel_area_addr(src_area, src_offset);
 181                 dst = snd_pcm_channel_area_addr(dst_area, dst_offset);
 182                 src_step = snd_pcm_channel_area_step(src_area);
 183                 dst_step = snd_pcm_channel_area_step(dst_area);
 184                 frames1 = frames;
 185                 while (frames1-- > 0) {
 186                         int16_t sample = ulaw_to_s16(*src);
 187                         goto *put;
 188 #define PUT16_END after
 189 #include "plugin_ops.h"
 190 #undef PUT16_END
 191                 after:
 192                         src += src_step;
 193                         dst += dst_step;
 194                 }
 195         }
 196 }
 197
 198 void snd_pcm_mulaw_encode(const snd_pcm_channel_area_t *dst_areas,
 199                           snd_pcm_uframes_t dst_offset,
 200                           const snd_pcm_channel_area_t *src_areas,
 201                           snd_pcm_uframes_t src_offset,
 202                           unsigned int channels, snd_pcm_uframes_t frames,
 203                           unsigned int getidx)
 204 {
 205 #define GET16_LABELS
 206 #include "plugin_ops.h"
 207 #undef GET16_LABELS
 208         void *get = get16_labels[getidx];
 209         unsigned int channel;
 210         int16_t sample = 0;
 211         for (channel = 0; channel < channels; ++channel) {
 212                 const char *src;
 213                 char *dst;
 214                 int src_step, dst_step;
 215                 snd_pcm_uframes_t frames1;
 216                 const snd_pcm_channel_area_t *src_area = &src_areas[channel];
 217                 const snd_pcm_channel_area_t *dst_area = &dst_areas[channel];
 218                 src = snd_pcm_channel_area_addr(src_area, src_offset);
 219                 dst = snd_pcm_channel_area_addr(dst_area, dst_offset);
 220                 src_step = snd_pcm_channel_area_step(src_area);
 221                 dst_step = snd_pcm_channel_area_step(dst_area);
 222                 frames1 = frames;
 223                 while (frames1-- > 0) {
 224                         goto *get;
 225 #define GET16_END after
 226 #include "plugin_ops.h"
 227 #undef GET16_END
 228                 after:
 229                         *dst = s16_to_ulaw(sample);
 230                         src += src_step;
 231                         dst += dst_step;
 232                 }
 233         }
 234 }
 235
 236 #endif /* DOC_HIDDEN */
 237
 238 static int snd_pcm_mulaw_hw_refine_cprepare(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
 239 {
 240         snd_pcm_mulaw_t *mulaw = pcm->private_data;
 241         int err;
 242         snd_pcm_access_mask_t access_mask = { SND_PCM_ACCBIT_SHM };
 243         err = _snd_pcm_hw_param_set_mask(params, SND_PCM_HW_PARAM_ACCESS,
 244                                          &access_mask);
 245         if (err < 0)
 246                 return err;
 247         if (mulaw->sformat == SND_PCM_FORMAT_MU_LAW) {
 248                 snd_pcm_format_mask_t format_mask= { SND_PCM_FMTBIT_LINEAR };
 249                 err = _snd_pcm_hw_param_set_mask(params, SND_PCM_HW_PARAM_FORMAT,
 250                                                  &format_mask);
 251         } else {
 252                 err = _snd_pcm_hw_params_set_format(params,
 253                                                    SND_PCM_FORMAT_MU_LAW);
 254         }
 255         err = _snd_pcm_hw_params_set_subformat(params, SND_PCM_SUBFORMAT_STD);
 256         if (err < 0)
 257                 return err;
 258         params->info &= ~(SND_PCM_INFO_MMAP | SND_PCM_INFO_MMAP_VALID);
 259         return 0;
 260 }
 261
 262 static int snd_pcm_mulaw_hw_refine_sprepare(snd_pcm_t *pcm, snd_pcm_hw_params_t *sparams)
 263 {
 264         snd_pcm_mulaw_t *mulaw = pcm->private_data;
 265         snd_pcm_access_mask_t saccess_mask = { SND_PCM_ACCBIT_MMAP };
 266         _snd_pcm_hw_params_any(sparams);
 267         _snd_pcm_hw_param_set_mask(sparams, SND_PCM_HW_PARAM_ACCESS,
 268                                    &saccess_mask);
 269         _snd_pcm_hw_params_set_format(sparams, mulaw->sformat);
 270         _snd_pcm_hw_params_set_subformat(sparams, SND_PCM_SUBFORMAT_STD);
 271         return 0;
 272 }
 273
 274 static int snd_pcm_mulaw_hw_refine_schange(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_hw_params_t *params,
 275                                             snd_pcm_hw_params_t *sparams)
 276 {
 277         int err;
 278         unsigned int links = (SND_PCM_HW_PARBIT_CHANNELS |
 279                               SND_PCM_HW_PARBIT_RATE |
 280                               SND_PCM_HW_PARBIT_PERIOD_SIZE |
 281                               SND_PCM_HW_PARBIT_BUFFER_SIZE |
 282                               SND_PCM_HW_PARBIT_PERIODS |
 283                               SND_PCM_HW_PARBIT_PERIOD_TIME |
 284                               SND_PCM_HW_PARBIT_BUFFER_TIME |
 285                               SND_PCM_HW_PARBIT_TICK_TIME);
 286         err = _snd_pcm_hw_params_refine(sparams, links, params);
 287         if (err < 0)
 288                 return err;
 289         return 0;
 290 }
 291
 292 static int snd_pcm_mulaw_hw_refine_cchange(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_hw_params_t *params,
 293                                             snd_pcm_hw_params_t *sparams)
 294 {
 295         int err;
 296         unsigned int links = (SND_PCM_HW_PARBIT_CHANNELS |
 297                               SND_PCM_HW_PARBIT_RATE |
 298                               SND_PCM_HW_PARBIT_PERIOD_SIZE |
 299                               SND_PCM_HW_PARBIT_BUFFER_SIZE |
 300                               SND_PCM_HW_PARBIT_PERIODS |
 301                               SND_PCM_HW_PARBIT_PERIOD_TIME |
 302                               SND_PCM_HW_PARBIT_BUFFER_TIME |
 303                               SND_PCM_HW_PARBIT_TICK_TIME);
 304         err = _snd_pcm_hw_params_refine(params, links, sparams);
 305         if (err < 0)
 306                 return err;
 307         return 0;
 308 }
 309
 310 static int snd_pcm_mulaw_hw_refine(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
 311 {
 312         return snd_pcm_hw_refine_slave(pcm, params,
 313                                        snd_pcm_mulaw_hw_refine_cprepare,
 314                                        snd_pcm_mulaw_hw_refine_cchange,
 315                                        snd_pcm_mulaw_hw_refine_sprepare,
 316                                        snd_pcm_mulaw_hw_refine_schange,
 317                                        snd_pcm_generic_hw_refine);
 318 }
 319
 320 static int snd_pcm_mulaw_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)
 321 {
 322         snd_pcm_mulaw_t *mulaw = pcm->private_data;
 323         snd_pcm_format_t format;
 324         int err = snd_pcm_hw_params_slave(pcm, params,
 325                                           snd_pcm_mulaw_hw_refine_cchange,
 326                                           snd_pcm_mulaw_hw_refine_sprepare,
 327                                           snd_pcm_mulaw_hw_refine_schange,
 328                                           snd_pcm_generic_hw_params);
 329         if (err < 0)
 330                 return err;
 331
 332         err = INTERNAL(snd_pcm_hw_params_get_format)(params, &format);
 333         if (err < 0)
 334                 return err;
 335
 336         if (pcm->stream == SND_PCM_STREAM_PLAYBACK) {
 337                 if (mulaw->sformat == SND_PCM_FORMAT_MU_LAW) {
 338                         mulaw->getput_idx = snd_pcm_linear_get_index(format, SND_PCM_FORMAT_S16);
 339                         mulaw->func = snd_pcm_mulaw_encode;
 340                 } else {
 341                         mulaw->getput_idx = snd_pcm_linear_put_index(SND_PCM_FORMAT_S16, mulaw->sformat);
 342                         mulaw->func = snd_pcm_mulaw_decode;
 343                 }
 344         } else {
 345                 if (mulaw->sformat == SND_PCM_FORMAT_MU_LAW) {
 346                         mulaw->getput_idx = snd_pcm_linear_put_index(SND_PCM_FORMAT_S16, format);
 347                         mulaw->func = snd_pcm_mulaw_decode;
 348                 } else {
 349                         mulaw->getput_idx = snd_pcm_linear_get_index(mulaw->sformat, SND_PCM_FORMAT_S16);
 350                         mulaw->func = snd_pcm_mulaw_encode;
 351                 }
 352         }
 353         return 0;
 354 }
 355
 356 static snd_pcm_uframes_t
 357 snd_pcm_mulaw_write_areas(snd_pcm_t *pcm,
 358                           const snd_pcm_channel_area_t *areas,
 359                           snd_pcm_uframes_t offset,
 360                           snd_pcm_uframes_t size,
 361                           const snd_pcm_channel_area_t *slave_areas,
 362                           snd_pcm_uframes_t slave_offset,
 363                           snd_pcm_uframes_t *slave_sizep)
 364 {
 365         snd_pcm_mulaw_t *mulaw = pcm->private_data;
 366         if (size > *slave_sizep)
 367                 size = *slave_sizep;
 368         mulaw->func(slave_areas, slave_offset,
 369                     areas, offset,
 370                     pcm->channels, size,
 371                     mulaw->getput_idx);
 372         *slave_sizep = size;
 373         return size;
 374 }
 375
 376 static snd_pcm_uframes_t
 377 snd_pcm_mulaw_read_areas(snd_pcm_t *pcm,
 378                          const snd_pcm_channel_area_t *areas,
 379                          snd_pcm_uframes_t offset,
 380                          snd_pcm_uframes_t size,
 381                          const snd_pcm_channel_area_t *slave_areas,
 382                          snd_pcm_uframes_t slave_offset,
 383                          snd_pcm_uframes_t *slave_sizep)
 384 {
 385         snd_pcm_mulaw_t *mulaw = pcm->private_data;
 386         if (size > *slave_sizep)
 387                 size = *slave_sizep;
 388         mulaw->func(areas, offset,
 389                     slave_areas, slave_offset,
 390                     pcm->channels, size,
 391                     mulaw->getput_idx);
 392         *slave_sizep = size;
 393         return size;
 394 }
 395
 396 static void snd_pcm_mulaw_dump(snd_pcm_t *pcm, snd_output_t *out)
 397 {
 398         snd_pcm_mulaw_t *mulaw = pcm->private_data;
 399         snd_output_printf(out, "Mu-Law conversion PCM (%s)\n",
 400                 snd_pcm_format_name(mulaw->sformat));
 401         if (pcm->setup) {
 402                 snd_output_printf(out, "Its setup is:\n");
 403                 snd_pcm_dump_setup(pcm, out);
 404         }
 405         snd_output_printf(out, "Slave: ");
 406         snd_pcm_dump(mulaw->plug.gen.slave, out);
 407 }
 408
 409 static const snd_pcm_ops_t snd_pcm_mulaw_ops = {
 410         .close = snd_pcm_generic_close,
 411         .info = snd_pcm_generic_info,
 412         .hw_refine = snd_pcm_mulaw_hw_refine,
 413         .hw_params = snd_pcm_mulaw_hw_params,
 414         .hw_free = snd_pcm_generic_hw_free,
 415         .sw_params = snd_pcm_generic_sw_params,
 416         .channel_info = snd_pcm_generic_channel_info,
 417         .dump = snd_pcm_mulaw_dump,
 418         .nonblock = snd_pcm_generic_nonblock,
 419         .async = snd_pcm_generic_async,
 420         .mmap = snd_pcm_generic_mmap,
 421         .munmap = snd_pcm_generic_munmap,
 422 };
 423
 424 /**
 425  * \brief Creates a new Mu-Law conversion PCM
 426  * \param pcmp Returns created PCM handle
 427  * \param name Name of PCM
 428  * \param sformat Slave (destination) format
 429  * \param slave Slave PCM handle
 430  * \param close_slave When set, the slave PCM handle is closed with copy PCM
 431  * \retval zero on success otherwise a negative error code
 432  * \warning Using of this function might be dangerous in the sense
 433  *          of compatibility reasons. The prototype might be freely
 434  *          changed in future.
 435  */
 436 int snd_pcm_mulaw_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sformat, snd_pcm_t *slave, int close_slave)
 437 {
 438         snd_pcm_t *pcm;
 439         snd_pcm_mulaw_t *mulaw;
 440         int err;
 441         assert(pcmp && slave);
 442         if (snd_pcm_format_linear(sformat) != 1 &&
 443             sformat != SND_PCM_FORMAT_MU_LAW)
 444                 return -EINVAL;
 445         mulaw = calloc(1, sizeof(snd_pcm_mulaw_t));
 446         if (!mulaw) {
 447                 return -ENOMEM;
 448         }
 449         snd_pcm_plugin_init(&mulaw->plug);
 450         mulaw->sformat = sformat;
 451         mulaw->plug.read = snd_pcm_mulaw_read_areas;
 452         mulaw->plug.write = snd_pcm_mulaw_write_areas;
 453         mulaw->plug.undo_read = snd_pcm_plugin_undo_read_generic;
 454         mulaw->plug.undo_write = snd_pcm_plugin_undo_write_generic;
 455         mulaw->plug.gen.slave = slave;
 456         mulaw->plug.gen.close_slave = close_slave;
 457
 458         err = snd_pcm_new(&pcm, SND_PCM_TYPE_MULAW, name, slave->stream, slave->mode);
 459         if (err < 0) {
 460                 free(mulaw);
 461                 return err;
 462         }
 463         pcm->ops = &snd_pcm_mulaw_ops;
 464         pcm->fast_ops = &snd_pcm_plugin_fast_ops;
 465         pcm->private_data = mulaw;
 466         pcm->poll_fd = slave->poll_fd;
 467         pcm->poll_events = slave->poll_events;
 468         pcm->monotonic = slave->monotonic;
 469         snd_pcm_set_hw_ptr(pcm, &mulaw->plug.hw_ptr, -1, 0);
 470         snd_pcm_set_appl_ptr(pcm, &mulaw->plug.appl_ptr, -1, 0);
 471         *pcmp = pcm;
 472
 473         return 0;
 474 }
 475
 476 /*! \page pcm_plugins
 477
 478 \section pcm_plugins_mulaw Plugin: Mu-Law
 479
 480 This plugin converts Mu-Law samples to linear or linear to Mu-Law samples
 481 from master Mu-Law conversion PCM to given slave PCM. The channel count,
 482 format and rate must match for both of them.
 483
 484 \code
 485 pcm.name {
 486         type mulaw              # Mu-Law conversion PCM
 487         slave STR               # Slave name
 488         # or
 489         slave {                 # Slave definition
 490                 pcm STR         # Slave PCM name
 491                 # or
 492                 pcm { }         # Slave PCM definition
 493                 format STR      # Slave format
 494         }
 495 }
 496 \endcode
 497
 498 \subsection pcm_plugins_mulaw_funcref Function reference
 499
 500 <UL>
 501   <LI>snd_pcm_mulaw_open()
 502   <LI>_snd_pcm_mulaw_open()
 503 </UL>
 504
 505 */
 506
 507 /**
 508  * \brief Creates a new Mu-Law conversion PCM
 509  * \param pcmp Returns created PCM handle
 510  * \param name Name of PCM
 511  * \param root Root configuration node
 512  * \param conf Configuration node with copy PCM description
 513  * \param stream Stream type
 514  * \param mode Stream mode
 515  * \retval zero on success otherwise a negative error code
 516  * \warning Using of this function might be dangerous in the sense
 517  *          of compatibility reasons. The prototype might be freely
 518  *          changed in future.
 519  */
 520 int _snd_pcm_mulaw_open(snd_pcm_t **pcmp, const char *name,
 521                         snd_config_t *root, snd_config_t *conf,
 522                         snd_pcm_stream_t stream, int mode)
 523 {
 524         snd_config_iterator_t i, next;
 525         int err;
 526         snd_pcm_t *spcm;
 527         snd_config_t *slave = NULL, *sconf;
 528         snd_pcm_format_t sformat;
 529         snd_config_for_each(i, next, conf) {
 530                 snd_config_t *n = snd_config_iterator_entry(i);
 531                 const char *id;
 532                 if (snd_config_get_id(n, &id) < 0)
 533                         continue;
 534                 if (snd_pcm_conf_generic_id(id))
 535                         continue;
 536                 if (strcmp(id, "slave") == 0) {
 537                         slave = n;
 538                         continue;
 539                 }
 540                 SNDERR("Unknown field %s", id);
 541                 return -EINVAL;
 542         }
 543         if (!slave) {
 544                 SNDERR("slave is not defined");
 545                 return -EINVAL;
 546         }
 547         err = snd_pcm_slave_conf(root, slave, &sconf, 1,
 548                                  SND_PCM_HW_PARAM_FORMAT, SCONF_MANDATORY, &sformat);
 549         if (err < 0)
 550                 return err;
 551         if (snd_pcm_format_linear(sformat) != 1 &&
 552             sformat != SND_PCM_FORMAT_MU_LAW) {
 553                 snd_config_delete(sconf);
 554                 SNDERR("invalid slave format");
 555                 return -EINVAL;
 556         }
 557         err = snd_pcm_open_slave(&spcm, root, sconf, stream, mode, conf);
 558         snd_config_delete(sconf);
 559         if (err < 0)
 560                 return err;
 561         err = snd_pcm_mulaw_open(pcmp, name, sformat, spcm, 1);
 562         if (err < 0)
 563                 snd_pcm_close(spcm);
 564         return err;
 565 }
 566 #ifndef DOC_HIDDEN
 567 SND_DLSYM_BUILD_VERSION(_snd_pcm_mulaw_open, SND_PCM_DLSYM_VERSION);
 568 #endif