modules/access/alsa.c

   1 /*****************************************************************************
   2  * alsa.c : Alsa input module for vlc
   3  *****************************************************************************
   4  * Copyright (C) 2002-2011 the VideoLAN team
   5  * $Id$
   6  *
   7  * Authors: Benjamin Pracht <bigben at videolan dot org>
   8  *          Richard Hosking <richard at hovis dot net>
   9  *          Antoine Cellerier <dionoea at videolan d.t org>
  10  *          Dennis Lou <dlou99 at yahoo dot com>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  25  *****************************************************************************/
  26
  27 /*
  28  * ALSA support based on parts of
  29  * http://www.equalarea.com/paul/alsa-audio.html
  30  * and hints taken from alsa-utils (aplay/arecord)
  31  * http://www.alsa-project.org
  32  */
  33
  34 /*****************************************************************************
  35  * Preamble
  36  *****************************************************************************/
  37
  38 #ifdef HAVE_CONFIG_H
  39 # include "config.h"
  40 #endif
  41
  42 #include <vlc_common.h>
  43 #include <vlc_plugin.h>
  44 #include <vlc_access.h>
  45 #include <vlc_demux.h>
  46 #include <vlc_input.h>
  47 #include <vlc_fourcc.h>
  48 #include <vlc_aout.h>
  49
  50 #include <unistd.h>
  51 #include <sys/ioctl.h>
  52 #include <sys/mman.h>
  53
  54 #include <sys/soundcard.h>
  55
  56 #define ALSA_PCM_NEW_HW_PARAMS_API
  57 #define ALSA_PCM_NEW_SW_PARAMS_API
  58 #include <alsa/asoundlib.h>
  59
  60 #include <poll.h>
  61
  62 /*****************************************************************************
  63  * Module descriptior
  64  *****************************************************************************/
  65
  66 static int  DemuxOpen ( vlc_object_t * );
  67 static void DemuxClose( vlc_object_t * );
  68
  69 #define STEREO_TEXT N_( "Stereo" )
  70 #define STEREO_LONGTEXT N_( \
  71     "Capture the audio stream in stereo." )
  72
  73 #define FORMAT_TEXT N_( "Capture format (default s16l)" )
  74 #define FORMAT_LONGTEXT N_( \
  75     "Capture format of audio stream." )
  76
  77 #define SAMPLERATE_TEXT N_( "Samplerate" )
  78 #define SAMPLERATE_LONGTEXT N_( \
  79     "Samplerate of the captured audio stream, in Hz (eg: 11025, 22050, 44100, 48000)" )
  80
  81 #define HELP_TEXT N_( \
  82     "Use alsa:// to open the default audio input. If multiple audio " \
  83     "inputs are available, they will be listed in the vlc debug output. " \
  84     "To select hw:0,1 , use alsa://hw:0,1 ." )
  85
  86 #define ALSA_DEFAULT "hw"
  87 #define CFG_PREFIX "alsa-"
  88
  89 static const char *const ppsz_fourcc[] = {
  90     "u8", "s8", "gsm", "u16l", "s16l", "u16b", "s16b",
  91     "u24l", "s24l", "u24b", "s24b", "u32l", "s32l",
  92     "u32b", "s32b", "f32l", "f32b", "f64l", "f64b"
  93 };
  94 static const char *const ppsz_fourcc_text[] = {
  95     N_("PCM U8"), N_("PCM S8"), N_("GSM Audio"),
  96     N_("PCM U16 LE"), N_("PCM S16 LE"),
  97     N_("PCM U16 BE"), N_("PCM S16 BE"),
  98     N_("PCM U24 LE"), N_("PCM S24 LE"),
  99     N_("PCM U24 BE"), N_("PCM S24 BE"),
 100     N_("PCM U32 LE"), N_("PCM S32 LE"),
 101     N_("PCM U32 BE"), N_("PCM S32 BE"),
 102     N_("PCM F32 LE"), N_("PCM F32 BE"),
 103     N_("PCM F64 LE"), N_("PCM F64 BE")
 104 };
 105
 106 vlc_module_begin()
 107     set_shortname( N_("ALSA") )
 108     set_description( N_("ALSA audio capture input") )
 109     set_category( CAT_INPUT )
 110     set_subcategory( SUBCAT_INPUT_ACCESS )
 111     set_help( HELP_TEXT )
 112
 113     add_shortcut( "alsa" )
 114     set_capability( "access_demux", 10 )
 115     set_callbacks( DemuxOpen, DemuxClose )
 116
 117     add_bool( CFG_PREFIX "stereo", true, STEREO_TEXT, STEREO_LONGTEXT,
 118                 true )
 119     add_string( CFG_PREFIX "format", "s16l", FORMAT_TEXT,
 120                 FORMAT_LONGTEXT, true )
 121         change_string_list( ppsz_fourcc, ppsz_fourcc_text, 0 )
 122     add_integer( CFG_PREFIX "samplerate", 48000, SAMPLERATE_TEXT,
 123                 SAMPLERATE_LONGTEXT, true )
 124 vlc_module_end()
 125
 126 /*****************************************************************************
 127  * Access: local prototypes
 128  *****************************************************************************/
 129
 130 static int DemuxControl( demux_t *, int, va_list );
 131
 132 static int Demux( demux_t * );
 133
 134 static block_t* GrabAudio( demux_t *p_demux );
 135
 136 static int OpenAudioDev( demux_t *, const char * );
 137 static bool ProbeAudioDevAlsa( demux_t *, const char * );
 138 static char *ListAvailableDevices( demux_t *, bool b_probe );
 139
 140 struct demux_sys_t
 141 {
 142     /* Audio */
 143     unsigned int i_sample_rate;
 144     bool b_stereo;
 145     vlc_fourcc_t i_format;
 146     size_t i_max_frame_size;
 147     block_t *p_block;
 148     es_out_id_t *p_es;
 149
 150     /* ALSA Audio */
 151     snd_pcm_t *p_alsa_pcm;
 152     size_t i_alsa_frame_size;
 153     int i_alsa_chunk_size;
 154
 155     int64_t i_next_demux_date; /* Used to handle alsa:// as input-slave properly */
 156 };
 157
 158 static int FindMainDevice( demux_t *p_demux, const char *psz_device )
 159 {
 160     if( psz_device )
 161     {
 162         msg_Dbg( p_demux, "opening device '%s'", psz_device );
 163         if( ProbeAudioDevAlsa( p_demux, psz_device ) )
 164         {
 165             msg_Dbg( p_demux, "'%s' is an audio device", psz_device );
 166             OpenAudioDev( p_demux, psz_device );
 167         }
 168     }
 169     else if( ProbeAudioDevAlsa( p_demux, ALSA_DEFAULT ) )
 170     {
 171         msg_Dbg( p_demux, "'%s' is an audio device", ALSA_DEFAULT );
 172         OpenAudioDev( p_demux, ALSA_DEFAULT );
 173     }
 174     else if( ( psz_device = ListAvailableDevices( p_demux, true ) ) )
 175     {
 176         msg_Dbg( p_demux, "'%s' is an audio device", psz_device );
 177         OpenAudioDev( p_demux, psz_device );
 178         free( (char *)psz_device );
 179     }
 180
 181     if( p_demux->p_sys->p_alsa_pcm == NULL )
 182         return VLC_EGENERIC;
 183     return VLC_SUCCESS;
 184 }
 185
 186 static char *ListAvailableDevices( demux_t *p_demux, bool b_probe )
 187 {
 188     snd_ctl_card_info_t *p_info = NULL;
 189     snd_ctl_card_info_alloca( &p_info );
 190
 191     snd_pcm_info_t *p_pcminfo = NULL;
 192     snd_pcm_info_alloca( &p_pcminfo );
 193
 194     if( !b_probe )
 195         msg_Dbg( p_demux, "Available alsa capture devices:" );
 196     int i_card = -1;
 197     while( !snd_card_next( &i_card ) && i_card >= 0 )
 198     {
 199         char psz_devname[10];
 200         snprintf( psz_devname, 10, "hw:%d", i_card );
 201
 202         snd_ctl_t *p_ctl = NULL;
 203         if( snd_ctl_open( &p_ctl, psz_devname, 0 ) < 0 ) continue;
 204
 205         snd_ctl_card_info( p_ctl, p_info );
 206         if( !b_probe )
 207             msg_Dbg( p_demux, "  %s (%s)",
 208                      snd_ctl_card_info_get_id( p_info ),
 209                      snd_ctl_card_info_get_name( p_info ) );
 210
 211         int i_dev = -1;
 212         while( !snd_ctl_pcm_next_device( p_ctl, &i_dev ) && i_dev >= 0 )
 213         {
 214             snd_pcm_info_set_device( p_pcminfo, i_dev );
 215             snd_pcm_info_set_subdevice( p_pcminfo, 0 );
 216             snd_pcm_info_set_stream( p_pcminfo, SND_PCM_STREAM_CAPTURE );
 217             if( snd_ctl_pcm_info( p_ctl, p_pcminfo ) < 0 ) continue;
 218
 219             if( !b_probe )
 220                 msg_Dbg( p_demux, "    hw:%d,%d : %s (%s)", i_card, i_dev,
 221                          snd_pcm_info_get_id( p_pcminfo ),
 222                          snd_pcm_info_get_name( p_pcminfo ) );
 223             else
 224             {
 225                 char *psz_device;
 226                 if( asprintf( &psz_device, "hw:%d,%d", i_card, i_dev ) > 0 )
 227                 {
 228                     if( ProbeAudioDevAlsa( p_demux, psz_device ) )
 229                     {
 230                         snd_ctl_close( p_ctl );
 231                         return psz_device;
 232                     }
 233                     else
 234                         free( psz_device );
 235                 }
 236             }
 237         }
 238
 239         snd_ctl_close( p_ctl );
 240     }
 241     return NULL;
 242 }
 243
 244 /*****************************************************************************
 245  * DemuxOpen: opens alsa device, access_demux callback
 246  *****************************************************************************
 247  *
 248  * url: <alsa device>::::
 249  *
 250  *****************************************************************************/
 251 static int DemuxOpen( vlc_object_t *p_this )
 252 {
 253     demux_t     *p_demux = (demux_t*)p_this;
 254     demux_sys_t *p_sys;
 255
 256     /* Only when selected */
 257     if( *p_demux->psz_access == '\0' ) return VLC_EGENERIC;
 258
 259     /* Set up p_demux */
 260     p_demux->pf_control = DemuxControl;
 261     p_demux->pf_demux = Demux;
 262     p_demux->info.i_update = 0;
 263     p_demux->info.i_title = 0;
 264     p_demux->info.i_seekpoint = 0;
 265
 266     p_demux->p_sys = p_sys = calloc( 1, sizeof( demux_sys_t ) );
 267     if( p_sys == NULL ) return VLC_ENOMEM;
 268
 269     p_sys->i_sample_rate = var_InheritInteger( p_demux, CFG_PREFIX "samplerate" );
 270     p_sys->b_stereo = var_InheritBool( p_demux, CFG_PREFIX "stereo" );
 271     p_sys->p_es = NULL;
 272     p_sys->p_block = NULL;
 273     p_sys->i_next_demux_date = -1;
 274
 275     char *psz_format = var_InheritString( p_demux, CFG_PREFIX "format" );
 276     p_sys->i_format = vlc_fourcc_GetCodecFromString( AUDIO_ES, psz_format );
 277     free( psz_format );
 278
 279     const char *psz_device = NULL;
 280     if( p_demux->psz_location && *p_demux->psz_location )
 281         psz_device = p_demux->psz_location;
 282     else
 283         ListAvailableDevices( p_demux, false );
 284
 285     if( FindMainDevice( p_demux, psz_device ) != VLC_SUCCESS )
 286     {
 287         if( p_demux->psz_location && *p_demux->psz_location )
 288             ListAvailableDevices( p_demux, false );
 289         DemuxClose( p_this );
 290         return VLC_EGENERIC;
 291     }
 292
 293     return VLC_SUCCESS;
 294 }
 295
 296 /*****************************************************************************
 297  * Close: close device, free resources
 298  *****************************************************************************/
 299 static void DemuxClose( vlc_object_t *p_this )
 300 {
 301     demux_t     *p_demux = (demux_t *)p_this;
 302     demux_sys_t *p_sys   = p_demux->p_sys;
 303
 304     if( p_sys->p_alsa_pcm )
 305     {
 306         snd_pcm_close( p_sys->p_alsa_pcm );
 307     }
 308
 309     if( p_sys->p_block ) block_Release( p_sys->p_block );
 310
 311     free( p_sys );
 312 }
 313
 314 /*****************************************************************************
 315  * DemuxControl:
 316  *****************************************************************************/
 317 static int DemuxControl( demux_t *p_demux, int i_query, va_list args )
 318 {
 319     demux_sys_t *p_sys = p_demux->p_sys;
 320
 321     switch( i_query )
 322     {
 323         /* Special for access_demux */
 324         case DEMUX_CAN_PAUSE:
 325         case DEMUX_CAN_SEEK:
 326         case DEMUX_SET_PAUSE_STATE:
 327         case DEMUX_CAN_CONTROL_PACE:
 328             *va_arg( args, bool * ) = false;
 329             return VLC_SUCCESS;
 330
 331         case DEMUX_GET_PTS_DELAY:
 332             *va_arg( args, int64_t * ) =
 333                 INT64_C(1000) * var_InheritInteger( p_demux, "live-caching" );
 334             return VLC_SUCCESS;
 335
 336         case DEMUX_GET_TIME:
 337             *va_arg( args, int64_t * ) = mdate();
 338             return VLC_SUCCESS;
 339
 340         case DEMUX_SET_NEXT_DEMUX_TIME:
 341             p_sys->i_next_demux_date = va_arg( args, int64_t );
 342             return VLC_SUCCESS;
 343
 344         /* TODO implement others */
 345         default:
 346             return VLC_EGENERIC;
 347     }
 348
 349     return VLC_EGENERIC;
 350 }
 351
 352 /*****************************************************************************
 353  * Demux: Processes the audio frame
 354  *****************************************************************************/
 355 static int Demux( demux_t *p_demux )
 356 {
 357     demux_sys_t *p_sys = p_demux->p_sys;
 358
 359     block_t *p_block = NULL;
 360
 361     do
 362     {
 363         p_block = GrabAudio( p_demux );
 364         if( p_block )
 365         {
 366             es_out_Control( p_demux->out, ES_OUT_SET_PCR, p_block->i_pts );
 367             es_out_Send( p_demux->out, p_sys->p_es, p_block );
 368             p_block = NULL;
 369         }
 370
 371     } while( p_block && p_sys->i_next_demux_date > 0 &&
 372              p_block->i_pts < p_sys->i_next_demux_date );
 373
 374     if( p_block )
 375         es_out_Send( p_demux->out, p_sys->p_es, p_block );
 376
 377     return 1;
 378 }
 379
 380 /*****************************************************************************
 381  * GrabAudio: Grab an audio frame
 382  *****************************************************************************/
 383 static block_t* GrabAudio( demux_t *p_demux )
 384 {
 385     demux_sys_t *p_sys = p_demux->p_sys;
 386     int i_read, i_correct;
 387     block_t *p_block;
 388
 389     if( p_sys->p_block ) p_block = p_sys->p_block;
 390     else p_block = block_New( p_demux, p_sys->i_max_frame_size );
 391
 392     if( !p_block )
 393     {
 394         msg_Warn( p_demux, "cannot get block" );
 395         return NULL;
 396     }
 397
 398     p_sys->p_block = p_block;
 399
 400     /* ALSA */
 401     i_read = snd_pcm_readi( p_sys->p_alsa_pcm, p_block->p_buffer,
 402                             p_sys->i_alsa_chunk_size );
 403     if( i_read == -EAGAIN )
 404     {
 405         snd_pcm_wait( p_sys->p_alsa_pcm, 10 ); /* See poll() comment in oss.c */
 406         return NULL;
 407     }
 408
 409     if( i_read < 0 )
 410         i_read = snd_pcm_recover( p_sys->p_alsa_pcm, i_read, 0 );
 411
 412     if( i_read <= 0 )
 413     {
 414         switch( i_read )
 415         {
 416             case 0: /* state recovered or no data */
 417                 return NULL;
 418             case -EAGAIN:
 419                 snd_pcm_wait( p_sys->p_alsa_pcm, 10 ); /* See poll() comment in oss.c */
 420                 return NULL;
 421             default:
 422                 msg_Err( p_demux, "Failed to read alsa frame (%s)",
 423                          snd_strerror( i_read ) );
 424                 return NULL;
 425         }
 426     }
 427
 428     /* convert from frames to bytes */
 429     i_read *= p_sys->i_alsa_frame_size;
 430
 431     p_block->i_buffer = i_read;
 432     p_sys->p_block = 0;
 433
 434     /* Correct the date because of kernel buffering */
 435     i_correct = i_read;
 436     /* ALSA */
 437     int i_err;
 438     snd_pcm_sframes_t delay = 0;
 439     if( ( i_err = snd_pcm_delay( p_sys->p_alsa_pcm, &delay ) ) >= 0 )
 440     {
 441         size_t i_correction_delta = delay * p_sys->i_alsa_frame_size;
 442         /* Test for overrun */
 443         if( i_correction_delta > p_sys->i_max_frame_size )
 444         {
 445             msg_Warn( p_demux, "ALSA read overrun (%zu > %zu)",
 446                       i_correction_delta, p_sys->i_max_frame_size );
 447             i_correction_delta = p_sys->i_max_frame_size;
 448             snd_pcm_prepare( p_sys->p_alsa_pcm );
 449         }
 450         i_correct += i_correction_delta;
 451     }
 452     else
 453     {
 454         /* delay failed so reset */
 455         msg_Warn( p_demux, "ALSA snd_pcm_delay failed (%s)", snd_strerror( i_err ) );
 456         snd_pcm_prepare( p_sys->p_alsa_pcm );
 457     }
 458
 459     /* Timestamp */
 460     p_block->i_pts = p_block->i_dts =
 461         mdate() - INT64_C(1000000) * (mtime_t)i_correct /
 462         2 / ( p_sys->b_stereo ? 2 : 1) / p_sys->i_sample_rate;
 463
 464     return p_block;
 465 }
 466
 467 static snd_pcm_format_t GetAlsaPCMFormat( demux_t *p_demux, const vlc_fourcc_t i_format )
 468 {
 469     demux_sys_t *p_sys = p_demux->p_sys;
 470
 471     switch( i_format )
 472     {
 473         case VLC_CODEC_U8: return SND_PCM_FORMAT_U8;
 474         case VLC_CODEC_S8: return SND_PCM_FORMAT_S8;
 475
 476         case VLC_CODEC_GSM: return SND_PCM_FORMAT_GSM;
 477
 478         case VLC_CODEC_U16L: return SND_PCM_FORMAT_U16_LE;
 479         case VLC_CODEC_S16L: return SND_PCM_FORMAT_S16_LE;
 480         case VLC_CODEC_U16B: return SND_PCM_FORMAT_U16_BE;
 481         case VLC_CODEC_S16B: return SND_PCM_FORMAT_S16_BE;
 482
 483         case VLC_CODEC_U24L: return SND_PCM_FORMAT_U24_3LE;
 484         case VLC_CODEC_S24L: return SND_PCM_FORMAT_S24_3LE;
 485         case VLC_CODEC_U24B: return SND_PCM_FORMAT_U24_3BE;
 486         case VLC_CODEC_S24B: return SND_PCM_FORMAT_S24_3BE;
 487
 488         case VLC_CODEC_U32L: return SND_PCM_FORMAT_U32_LE;
 489         case VLC_CODEC_U32B: return SND_PCM_FORMAT_U32_BE;
 490         case VLC_CODEC_S32L: return SND_PCM_FORMAT_S32_LE;
 491         case VLC_CODEC_S32B: return SND_PCM_FORMAT_S32_BE;
 492         case VLC_CODEC_F32L: return SND_PCM_FORMAT_FLOAT_LE;
 493         case VLC_CODEC_F32B: return SND_PCM_FORMAT_FLOAT_BE;
 494
 495         case VLC_CODEC_F64L: return SND_PCM_FORMAT_FLOAT64_LE;
 496         case VLC_CODEC_F64B: return SND_PCM_FORMAT_FLOAT64_BE;
 497
 498         default:
 499             msg_Err( p_demux, "ALSA: unsupported sample format '%s' falling back to 's16l'",
 500                               (const char *)&i_format );
 501             p_sys->i_format = VLC_CODEC_S16L;
 502     }
 503
 504     return SND_PCM_FORMAT_S16_LE;
 505 }
 506
 507 /*****************************************************************************
 508  * OpenAudioDev: open and set up the audio device and probe for capabilities
 509  *****************************************************************************/
 510 static int OpenAudioDevAlsa( demux_t *p_demux, const char *psz_device )
 511 {
 512     demux_sys_t *p_sys = p_demux->p_sys;
 513     p_sys->p_alsa_pcm = NULL;
 514     snd_pcm_hw_params_t *p_hw_params = NULL;
 515     snd_pcm_format_t i_alsa_pcm_format;
 516     snd_pcm_uframes_t buffer_size;
 517     snd_pcm_uframes_t chunk_size;
 518
 519     /* ALSA */
 520     int i_err;
 521
 522     if( ( i_err = snd_pcm_open( &p_sys->p_alsa_pcm, psz_device,
 523         SND_PCM_STREAM_CAPTURE, SND_PCM_NONBLOCK ) ) < 0)
 524     {
 525         msg_Err( p_demux, "Cannot open ALSA audio device %s (%s)",
 526                  psz_device, snd_strerror( i_err ) );
 527         goto adev_fail;
 528     }
 529
 530     if( ( i_err = snd_pcm_nonblock( p_sys->p_alsa_pcm, 1 ) ) < 0)
 531     {
 532         msg_Err( p_demux, "Cannot set ALSA nonblock (%s)",
 533                  snd_strerror( i_err ) );
 534         goto adev_fail;
 535     }
 536
 537     /* Begin setting hardware parameters */
 538
 539     if( ( i_err = snd_pcm_hw_params_malloc( &p_hw_params ) ) < 0 )
 540     {
 541         msg_Err( p_demux,
 542                  "ALSA: cannot allocate hardware parameter structure (%s)",
 543                  snd_strerror( i_err ) );
 544         goto adev_fail;
 545     }
 546
 547     if( ( i_err = snd_pcm_hw_params_any( p_sys->p_alsa_pcm, p_hw_params ) ) < 0 )
 548     {
 549         msg_Err( p_demux,
 550                 "ALSA: cannot initialize hardware parameter structure (%s)",
 551                  snd_strerror( i_err ) );
 552         goto adev_fail;
 553     }
 554
 555     /* Set Interleaved access */
 556     if( ( i_err = snd_pcm_hw_params_set_access( p_sys->p_alsa_pcm, p_hw_params,
 557                                         SND_PCM_ACCESS_RW_INTERLEAVED ) ) < 0 )
 558     {
 559         msg_Err( p_demux, "ALSA: cannot set access type (%s)",
 560                  snd_strerror( i_err ) );
 561         goto adev_fail;
 562     }
 563
 564     /* Set capture format, default is signed 16 bit little endian */
 565     i_alsa_pcm_format = GetAlsaPCMFormat( p_demux, p_sys->i_format );
 566     if( ( i_err = snd_pcm_hw_params_set_format( p_sys->p_alsa_pcm, p_hw_params,
 567                                                 i_alsa_pcm_format ) ) < 0 )
 568     {
 569         msg_Err( p_demux, "ALSA: cannot set sample format (%s)",
 570                  snd_strerror( i_err ) );
 571         goto adev_fail;
 572     }
 573
 574     /* Set sample rate */
 575     i_err = snd_pcm_hw_params_set_rate_near( p_sys->p_alsa_pcm, p_hw_params,
 576                                              &p_sys->i_sample_rate, NULL );
 577     if( i_err < 0 )
 578     {
 579         msg_Err( p_demux, "ALSA: cannot set sample rate (%s)",
 580                  snd_strerror( i_err ) );
 581         goto adev_fail;
 582     }
 583
 584     /* Set channels */
 585     unsigned int channels = p_sys->b_stereo ? 2 : 1;
 586     if( ( i_err = snd_pcm_hw_params_set_channels( p_sys->p_alsa_pcm, p_hw_params,
 587                                                   channels ) ) < 0 )
 588     {
 589         channels = ( channels==1 ) ? 2 : 1;
 590         msg_Warn( p_demux, "ALSA: cannot set channel count (%s). "
 591                   "Trying with channels=%d",
 592                   snd_strerror( i_err ),
 593                   channels );
 594         if( ( i_err = snd_pcm_hw_params_set_channels( p_sys->p_alsa_pcm, p_hw_params,
 595                                                       channels ) ) < 0 )
 596         {
 597             msg_Err( p_demux, "ALSA: cannot set channel count (%s)",
 598                      snd_strerror( i_err ) );
 599             goto adev_fail;
 600         }
 601         p_sys->b_stereo = ( channels == 2 );
 602     }
 603
 604     /* Set metrics for buffer calculations later */
 605     unsigned int buffer_time;
 606     if( ( i_err = snd_pcm_hw_params_get_buffer_time_max(p_hw_params, &buffer_time, 0) ) < 0 )
 607     {
 608         msg_Err( p_demux, "ALSA: cannot get buffer time max (%s)",
 609                  snd_strerror( i_err ) );
 610         goto adev_fail;
 611     }
 612     if( buffer_time > 500000 ) buffer_time = 500000;
 613
 614     /* Set period time */
 615     unsigned int period_time = buffer_time / 4;
 616     i_err = snd_pcm_hw_params_set_period_time_near( p_sys->p_alsa_pcm, p_hw_params,
 617                                                     &period_time, 0 );
 618     if( i_err < 0 )
 619     {
 620         msg_Err( p_demux, "ALSA: cannot set period time (%s)",
 621                  snd_strerror( i_err ) );
 622         goto adev_fail;
 623     }
 624
 625     /* Set buffer time */
 626     i_err = snd_pcm_hw_params_set_buffer_time_near( p_sys->p_alsa_pcm, p_hw_params,
 627                                                     &buffer_time, 0 );
 628     if( i_err < 0 )
 629     {
 630         msg_Err( p_demux, "ALSA: cannot set buffer time (%s)",
 631                  snd_strerror( i_err ) );
 632         goto adev_fail;
 633     }
 634
 635     /* Apply new hardware parameters */
 636     if( ( i_err = snd_pcm_hw_params( p_sys->p_alsa_pcm, p_hw_params ) ) < 0 )
 637     {
 638         msg_Err( p_demux, "ALSA: cannot set hw parameters (%s)",
 639                  snd_strerror( i_err ) );
 640         goto adev_fail;
 641     }
 642
 643     /* Get various buffer metrics */
 644     snd_pcm_hw_params_get_period_size( p_hw_params, &chunk_size, 0 );
 645     snd_pcm_hw_params_get_buffer_size( p_hw_params, &buffer_size );
 646     if( chunk_size == buffer_size )
 647     {
 648         msg_Err( p_demux,
 649                  "ALSA: period cannot equal buffer size (%lu == %lu)",
 650                  chunk_size, buffer_size);
 651         goto adev_fail;
 652     }
 653
 654     int bits_per_sample = snd_pcm_format_physical_width(i_alsa_pcm_format);
 655     int bits_per_frame = bits_per_sample * channels;
 656
 657     p_sys->i_alsa_chunk_size = chunk_size;
 658     p_sys->i_alsa_frame_size = bits_per_frame / 8;
 659     p_sys->i_max_frame_size = chunk_size * bits_per_frame / 8;
 660
 661     snd_pcm_hw_params_free( p_hw_params );
 662     p_hw_params = NULL;
 663
 664     /* Prep device */
 665     if( ( i_err = snd_pcm_prepare( p_sys->p_alsa_pcm ) ) < 0 )
 666     {
 667         msg_Err( p_demux,
 668                  "ALSA: cannot prepare audio interface for use (%s)",
 669                  snd_strerror( i_err ) );
 670         goto adev_fail;
 671     }
 672
 673     snd_pcm_start( p_sys->p_alsa_pcm );
 674
 675     return VLC_SUCCESS;
 676
 677  adev_fail:
 678
 679     if( p_hw_params ) snd_pcm_hw_params_free( p_hw_params );
 680     if( p_sys->p_alsa_pcm ) snd_pcm_close( p_sys->p_alsa_pcm );
 681     p_sys->p_alsa_pcm = NULL;
 682
 683     return VLC_EGENERIC;
 684 }
 685
 686 static int OpenAudioDev( demux_t *p_demux, const char *psz_device )
 687 {
 688     demux_sys_t *p_sys = p_demux->p_sys;
 689     if( OpenAudioDevAlsa( p_demux, psz_device ) != VLC_SUCCESS )
 690         return VLC_EGENERIC;
 691
 692     msg_Dbg( p_demux, "opened adev=`%s' %s %dHz codec '%s'",
 693              psz_device, p_sys->b_stereo ? "stereo" : "mono",
 694              p_sys->i_sample_rate,
 695              vlc_fourcc_GetDescription( AUDIO_ES, p_sys->i_format ) );
 696
 697     es_format_t fmt;
 698     es_format_Init( &fmt, AUDIO_ES, p_sys->i_format );
 699
 700     fmt.audio.i_channels = p_sys->b_stereo ? 2 : 1;
 701     fmt.audio.i_rate = p_sys->i_sample_rate;
 702     fmt.audio.i_bitspersample = aout_BitsPerSample( p_sys->i_format );
 703     fmt.audio.i_blockalign = fmt.audio.i_channels * fmt.audio.i_bitspersample / 8;
 704     fmt.i_bitrate = fmt.audio.i_channels * fmt.audio.i_rate * fmt.audio.i_bitspersample;
 705
 706     msg_Dbg( p_demux, "new audio es %d channels %dHz",
 707              fmt.audio.i_channels, fmt.audio.i_rate );
 708
 709     p_sys->p_es = es_out_Add( p_demux->out, &fmt );
 710
 711     return VLC_SUCCESS;
 712 }
 713
 714 /*****************************************************************************
 715  * ProbeAudioDevAlsa: probe audio for capabilities
 716  *****************************************************************************/
 717 static bool ProbeAudioDevAlsa( demux_t *p_demux, const char *psz_device )
 718 {
 719     int i_err;
 720     snd_pcm_t *p_alsa_pcm;
 721
 722     if( ( i_err = snd_pcm_open( &p_alsa_pcm, psz_device, SND_PCM_STREAM_CAPTURE, SND_PCM_NONBLOCK ) ) < 0 )
 723     {
 724         msg_Err( p_demux, "cannot open device %s for ALSA audio (%s)", psz_device, snd_strerror( i_err ) );
 725         return false;
 726     }
 727
 728     snd_pcm_close( p_alsa_pcm );
 729
 730     return true;
 731 }