modules/audio_output/oss.c

   1 /*****************************************************************************
   2  * oss.c : OSS /dev/dsp module for vlc
   3  *****************************************************************************
   4  * Copyright (C) 2000-2002 the VideoLAN team
   5  * $Id$
   6  *
   7  * Authors: Michel Kaempf <maxx@via.ecp.fr>
   8  *          Sam Hocevar <sam@zoy.org>
   9  *          Christophe Massiot <massiot@via.ecp.fr>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  24  *****************************************************************************/
  25
  26 /*****************************************************************************
  27  * Preamble
  28  *****************************************************************************/
  29
  30 #ifdef HAVE_CONFIG_H
  31 # include "config.h"
  32 #endif
  33
  34 #include <fcntl.h>                                       /* open(), O_WRONLY */
  35 #include <sys/ioctl.h>                                            /* ioctl() */
  36 #include <unistd.h>                                      /* write(), close() */
  37
  38 #include <vlc_common.h>
  39 #include <vlc_plugin.h>
  40 #include <vlc_fs.h>
  41
  42 #include <vlc_aout.h>
  43
  44 /* SNDCTL_DSP_RESET, SNDCTL_DSP_SETFMT, SNDCTL_DSP_STEREO, SNDCTL_DSP_SPEED,
  45  * SNDCTL_DSP_GETOSPACE */
  46 #ifdef HAVE_SOUNDCARD_H
  47 #   include <soundcard.h>
  48 #elif defined( HAVE_SYS_SOUNDCARD_H )
  49 #   include <sys/soundcard.h>
  50 #endif
  51
  52 /* Patches for ignorant OSS versions */
  53 #ifndef AFMT_AC3
  54 #   define AFMT_AC3     0x00000400        /* Dolby Digital AC3 */
  55 #endif
  56
  57 #ifndef AFMT_S16_NE
  58 #   ifdef WORDS_BIGENDIAN
  59 #       define AFMT_S16_NE AFMT_S16_BE
  60 #   else
  61 #       define AFMT_S16_NE AFMT_S16_LE
  62 #   endif
  63 #endif
  64
  65 /*****************************************************************************
  66  * aout_sys_t: OSS audio output method descriptor
  67  *****************************************************************************
  68  * This structure is part of the audio output thread descriptor.
  69  * It describes the DSP specific properties of an audio device.
  70  *****************************************************************************/
  71 struct aout_sys_t
  72 {
  73     int i_fd;
  74     int b_workaround_buggy_driver;
  75     int i_fragstotal;
  76     mtime_t max_buffer_duration;
  77 };
  78
  79 /* This must be a power of 2. */
  80 #define FRAME_SIZE 1024
  81 #define FRAME_COUNT 32
  82
  83 /*****************************************************************************
  84  * Local prototypes
  85  *****************************************************************************/
  86 static int  Open         ( vlc_object_t * );
  87 static void Close        ( vlc_object_t * );
  88
  89 static void Play         ( aout_instance_t * );
  90 static void* OSSThread   ( vlc_object_t * );
  91
  92 static mtime_t BufferDuration( aout_instance_t * p_aout );
  93
  94 /*****************************************************************************
  95  * Module descriptor
  96  *****************************************************************************/
  97 #define BUGGY_TEXT N_("Try to work around buggy OSS drivers")
  98 #define BUGGY_LONGTEXT N_( \
  99     "Some buggy OSS drivers just don't like when their internal buffers " \
 100     "are completely filled (the sound gets heavily hashed). If you have one " \
 101     "of these drivers, then you need to enable this option." )
 102
 103 vlc_module_begin ()
 104     set_shortname( "OSS" )
 105     set_description( N_("UNIX OSS audio output") )
 106
 107     set_category( CAT_AUDIO )
 108     set_subcategory( SUBCAT_AUDIO_AOUT )
 109     add_loadfile( "oss-audio-device", "/dev/dsp",
 110                   N_("OSS DSP device"), NULL, false )
 111         add_deprecated_alias( "dspdev" )   /* deprecated since 0.9.3 */
 112     add_bool( "oss-buggy", false, NULL, BUGGY_TEXT, BUGGY_LONGTEXT, true )
 113
 114     set_capability( "audio output", 100 )
 115     add_shortcut( "oss" )
 116     set_callbacks( Open, Close )
 117 vlc_module_end ()
 118
 119 /*****************************************************************************
 120  * Probe: probe the audio device for available formats and channels
 121  *****************************************************************************/
 122 static void Probe( aout_instance_t * p_aout )
 123 {
 124     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 125     vlc_value_t val, text;
 126     int i_format, i_nb_channels;
 127
 128     var_Create( p_aout, "audio-device", VLC_VAR_INTEGER | VLC_VAR_HASCHOICE );
 129     text.psz_string = _("Audio Device");
 130     var_Change( p_aout, "audio-device", VLC_VAR_SETTEXT, &text, NULL );
 131
 132     /* Test for multi-channel. */
 133 #ifdef SNDCTL_DSP_GETCHANNELMASK
 134     if ( aout_FormatNbChannels( &p_aout->output.output ) > 2 )
 135     {
 136         /* Check that the device supports this. */
 137
 138         int i_chanmask;
 139
 140         /* Reset all. */
 141         i_format = AFMT_S16_NE;
 142         if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 ||
 143             ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
 144         {
 145             msg_Err( p_aout, "cannot reset OSS audio device" );
 146             var_Destroy( p_aout, "audio-device" );
 147             return;
 148         }
 149
 150         if ( ioctl( p_sys->i_fd, SNDCTL_DSP_GETCHANNELMASK,
 151                     &i_chanmask ) == 0 )
 152         {
 153             if ( !(i_chanmask & DSP_BIND_FRONT) )
 154             {
 155                 msg_Err( p_aout, "no front channels! (%x)",
 156                          i_chanmask );
 157                 return;
 158             }
 159
 160             if ( (i_chanmask & (DSP_BIND_SURR | DSP_BIND_CENTER_LFE))
 161                   && (p_aout->output.output.i_physical_channels ==
 162                        (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 163                          | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT
 164                          | AOUT_CHAN_LFE)) )
 165             {
 166                 val.i_int = AOUT_VAR_5_1;
 167                 text.psz_string = (char*) "5.1";
 168                 var_Change( p_aout, "audio-device",
 169                             VLC_VAR_ADDCHOICE, &val, &text );
 170             }
 171
 172             if ( (i_chanmask & DSP_BIND_SURR)
 173                   && (p_aout->output.output.i_physical_channels &
 174                        (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 175                          | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT)) )
 176             {
 177                 val.i_int = AOUT_VAR_2F2R;
 178                 text.psz_string = _("2 Front 2 Rear");
 179                 var_Change( p_aout, "audio-device",
 180                             VLC_VAR_ADDCHOICE, &val, &text );
 181             }
 182         }
 183     }
 184 #endif
 185
 186     /* Reset all. */
 187     i_format = AFMT_S16_NE;
 188     if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 ||
 189         ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
 190     {
 191         msg_Err( p_aout, "cannot reset OSS audio device" );
 192         var_Destroy( p_aout, "audio-device" );
 193         return;
 194     }
 195
 196     /* Test for stereo. */
 197     i_nb_channels = 2;
 198     if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) >= 0
 199          && i_nb_channels == 2 )
 200     {
 201         val.i_int = AOUT_VAR_STEREO;
 202         text.psz_string = _("Stereo");
 203         var_Change( p_aout, "audio-device", VLC_VAR_ADDCHOICE, &val, &text );
 204     }
 205
 206     /* Reset all. */
 207     i_format = AFMT_S16_NE;
 208     if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 ||
 209         ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
 210     {
 211         msg_Err( p_aout, "cannot reset OSS audio device" );
 212         var_Destroy( p_aout, "audio-device" );
 213         return;
 214     }
 215
 216     /* Test for mono. */
 217     i_nb_channels = 1;
 218     if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) >= 0
 219          && i_nb_channels == 1 )
 220     {
 221         val.i_int = AOUT_VAR_MONO;
 222         text.psz_string = _("Mono");
 223         var_Change( p_aout, "audio-device", VLC_VAR_ADDCHOICE, &val, &text );
 224         if ( p_aout->output.output.i_physical_channels == AOUT_CHAN_CENTER )
 225         {
 226             var_Set( p_aout, "audio-device", val );
 227         }
 228     }
 229
 230     if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 )
 231     {
 232         msg_Err( p_aout, "cannot reset OSS audio device" );
 233         var_Destroy( p_aout, "audio-device" );
 234         return;
 235     }
 236
 237     /* Test for spdif. */
 238     if ( AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
 239     {
 240         i_format = AFMT_AC3;
 241
 242         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) >= 0
 243              && i_format == AFMT_AC3 )
 244         {
 245             val.i_int = AOUT_VAR_SPDIF;
 246             text.psz_string = _("A/52 over S/PDIF");
 247             var_Change( p_aout, "audio-device",
 248                         VLC_VAR_ADDCHOICE, &val, &text );
 249             if( var_InheritBool( p_aout, "spdif" ) )
 250                 var_Set( p_aout, "audio-device", val );
 251         }
 252         else if( var_InheritBool( p_aout, "spdif" ) )
 253         {
 254             msg_Warn( p_aout, "S/PDIF not supported by card" );
 255         }
 256     }
 257
 258     var_AddCallback( p_aout, "audio-device", aout_ChannelsRestart,
 259                      NULL );
 260 }
 261
 262 /*****************************************************************************
 263  * Open: open the audio device (the digital sound processor)
 264  *****************************************************************************
 265  * This function opens the DSP as a usual non-blocking write-only file, and
 266  * modifies the p_aout->p_sys->i_fd with the file's descriptor.
 267  *****************************************************************************/
 268 static int Open( vlc_object_t *p_this )
 269 {
 270     aout_instance_t * p_aout = (aout_instance_t *)p_this;
 271     struct aout_sys_t * p_sys;
 272     char * psz_device;
 273     vlc_value_t val;
 274
 275     /* Allocate structure */
 276     p_aout->output.p_sys = p_sys = malloc( sizeof( aout_sys_t ) );
 277     if( p_sys == NULL )
 278         return VLC_ENOMEM;
 279
 280     /* Get device name */
 281     if( (psz_device = var_InheritString( p_aout, "oss-audio-device" )) == NULL )
 282     {
 283         msg_Err( p_aout, "no audio device specified (maybe /dev/dsp?)" );
 284         free( p_sys );
 285         return VLC_EGENERIC;
 286     }
 287
 288     /* Open the sound device in non-blocking mode, because ALSA's OSS
 289      * emulation and some broken OSS drivers would make a blocking call
 290      * wait forever until the device is available. Since this breaks the
 291      * OSS spec, we immediately put it back to blocking mode if the
 292      * operation was successful. */
 293     p_sys->i_fd = vlc_open( psz_device, O_WRONLY | O_NDELAY );
 294     if( p_sys->i_fd < 0 )
 295     {
 296         msg_Err( p_aout, "cannot open audio device (%s)", psz_device );
 297         free( psz_device );
 298         free( p_sys );
 299         return VLC_EGENERIC;
 300     }
 301
 302     /* if the opening was ok, put the device back in blocking mode */
 303     fcntl( p_sys->i_fd, F_SETFL,
 304             fcntl( p_sys->i_fd, F_GETFL ) &~ FNDELAY );
 305
 306     free( psz_device );
 307
 308     p_aout->output.pf_play = Play;
 309
 310     if ( var_Type( p_aout, "audio-device" ) == 0 )
 311     {
 312         Probe( p_aout );
 313     }
 314
 315     if ( var_Get( p_aout, "audio-device", &val ) < 0 )
 316     {
 317         /* Probe() has failed. */
 318         close( p_sys->i_fd );
 319         free( p_sys );
 320         return VLC_EGENERIC;
 321     }
 322
 323     if ( val.i_int == AOUT_VAR_SPDIF )
 324     {
 325         p_aout->output.output.i_format = VLC_CODEC_SPDIFL;
 326     }
 327     else if ( val.i_int == AOUT_VAR_5_1 )
 328     {
 329         p_aout->output.output.i_format = VLC_CODEC_S16N;
 330         p_aout->output.output.i_physical_channels
 331             = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 332                | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT
 333                | AOUT_CHAN_LFE;
 334     }
 335     else if ( val.i_int == AOUT_VAR_2F2R )
 336     {
 337         p_aout->output.output.i_format = VLC_CODEC_S16N;
 338         p_aout->output.output.i_physical_channels
 339             = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 340                | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT;
 341     }
 342     else if ( val.i_int == AOUT_VAR_STEREO )
 343     {
 344         p_aout->output.output.i_format = VLC_CODEC_S16N;
 345         p_aout->output.output.i_physical_channels
 346             = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 347     }
 348     else if ( val.i_int == AOUT_VAR_MONO )
 349     {
 350         p_aout->output.output.i_format = VLC_CODEC_S16N;
 351         p_aout->output.output.i_physical_channels = AOUT_CHAN_CENTER;
 352     }
 353     else
 354     {
 355         /* This should not happen ! */
 356         msg_Err( p_aout, "internal: can't find audio-device (%"PRId64")",
 357                  val.i_int );
 358         close( p_sys->i_fd );
 359         free( p_sys );
 360         return VLC_EGENERIC;
 361     }
 362
 363     var_SetBool( p_aout, "intf-change", true );
 364
 365     /* Reset the DSP device */
 366     if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 )
 367     {
 368         msg_Err( p_aout, "cannot reset OSS audio device" );
 369         close( p_sys->i_fd );
 370         free( p_sys );
 371         return VLC_EGENERIC;
 372     }
 373
 374     /* Set the output format */
 375     if ( AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
 376     {
 377         int i_format = AFMT_AC3;
 378
 379         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0
 380              || i_format != AFMT_AC3 )
 381         {
 382             msg_Err( p_aout, "cannot reset OSS audio device" );
 383             close( p_sys->i_fd );
 384             free( p_sys );
 385             return VLC_EGENERIC;
 386         }
 387
 388         p_aout->output.output.i_format = VLC_CODEC_SPDIFL;
 389         p_aout->output.i_nb_samples = A52_FRAME_NB;
 390         p_aout->output.output.i_bytes_per_frame = AOUT_SPDIF_SIZE;
 391         p_aout->output.output.i_frame_length = A52_FRAME_NB;
 392
 393         aout_VolumeNoneInit( p_aout );
 394     }
 395
 396     if ( !AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
 397     {
 398         unsigned int i_format = AFMT_S16_NE;
 399         unsigned int i_frame_size, i_fragments;
 400         unsigned int i_rate;
 401         unsigned int i_nb_channels;
 402         audio_buf_info audio_buf;
 403
 404         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
 405         {
 406             msg_Err( p_aout, "cannot set audio output format" );
 407             close( p_sys->i_fd );
 408             free( p_sys );
 409             return VLC_EGENERIC;
 410         }
 411
 412         switch ( i_format )
 413         {
 414         case AFMT_U8:
 415             p_aout->output.output.i_format = VLC_CODEC_U8;
 416             break;
 417         case AFMT_S8:
 418             p_aout->output.output.i_format = VLC_CODEC_S8;
 419             break;
 420         case AFMT_U16_LE:
 421             p_aout->output.output.i_format = VLC_CODEC_U16L;
 422             break;
 423         case AFMT_S16_LE:
 424             p_aout->output.output.i_format = VLC_CODEC_S16L;
 425             break;
 426         case AFMT_U16_BE:
 427             p_aout->output.output.i_format = VLC_CODEC_U16B;
 428             break;
 429         case AFMT_S16_BE:
 430             p_aout->output.output.i_format = VLC_CODEC_S16B;
 431             break;
 432         default:
 433             msg_Err( p_aout, "OSS fell back to an unknown format (%d)",
 434                      i_format );
 435             close( p_sys->i_fd );
 436             free( p_sys );
 437             return VLC_EGENERIC;
 438         }
 439
 440         i_nb_channels = aout_FormatNbChannels( &p_aout->output.output );
 441
 442         /* Set the number of channels */
 443         if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) < 0 ||
 444             i_nb_channels != aout_FormatNbChannels( &p_aout->output.output ) )
 445         {
 446             msg_Err( p_aout, "cannot set number of audio channels (%s)",
 447                      aout_FormatPrintChannels( &p_aout->output.output) );
 448             close( p_sys->i_fd );
 449             free( p_sys );
 450             return VLC_EGENERIC;
 451         }
 452
 453         /* Set the output rate */
 454         i_rate = p_aout->output.output.i_rate;
 455         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SPEED, &i_rate ) < 0 )
 456         {
 457             msg_Err( p_aout, "cannot set audio output rate (%i)",
 458                              p_aout->output.output.i_rate );
 459             close( p_sys->i_fd );
 460             free( p_sys );
 461             return VLC_EGENERIC;
 462         }
 463
 464         if( i_rate != p_aout->output.output.i_rate )
 465         {
 466             p_aout->output.output.i_rate = i_rate;
 467         }
 468
 469         /* Set the fragment size */
 470         aout_FormatPrepare( &p_aout->output.output );
 471
 472         /* i_fragment = xxxxyyyy where: xxxx        is fragtotal
 473          *                              1 << yyyy   is fragsize */
 474         i_frame_size = ((uint64_t)p_aout->output.output.i_bytes_per_frame * p_aout->output.output.i_rate * 65536) / (48000 * 2 * 2) / FRAME_COUNT;
 475         i_fragments = 4;
 476         while( i_fragments < 12 && (1U << i_fragments) < i_frame_size )
 477         {
 478             ++i_fragments;
 479         }
 480         i_fragments |= FRAME_COUNT << 16;
 481         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFRAGMENT, &i_fragments ) < 0 )
 482         {
 483             msg_Warn( p_aout, "cannot set fragment size (%.8x)", i_fragments );
 484         }
 485
 486         if( ioctl( p_sys->i_fd, SNDCTL_DSP_GETOSPACE, &audio_buf ) < 0 )
 487         {
 488             msg_Err( p_aout, "cannot get fragment size" );
 489             close( p_sys->i_fd );
 490             free( p_sys );
 491             return VLC_EGENERIC;
 492         }
 493         else
 494         {
 495             /* Number of fragments actually allocated */
 496             p_aout->output.p_sys->i_fragstotal = audio_buf.fragstotal;
 497
 498             /* Maximum duration the soundcard's buffer can hold */
 499             p_aout->output.p_sys->max_buffer_duration =
 500                 (mtime_t)audio_buf.fragstotal * audio_buf.fragsize * 1000000
 501                 / p_aout->output.output.i_bytes_per_frame
 502                 / p_aout->output.output.i_rate
 503                 * p_aout->output.output.i_frame_length;
 504
 505             p_aout->output.i_nb_samples = audio_buf.fragsize /
 506                 p_aout->output.output.i_bytes_per_frame;
 507         }
 508
 509         aout_VolumeSoftInit( p_aout );
 510     }
 511
 512     p_aout->output.p_sys->b_workaround_buggy_driver =
 513         var_InheritBool( p_aout, "oss-buggy" );
 514
 515     /* Create OSS thread and wait for its readiness. */
 516     if( vlc_thread_create( p_aout, "aout", OSSThread,
 517                            VLC_THREAD_PRIORITY_OUTPUT ) )
 518     {
 519         msg_Err( p_aout, "cannot create OSS thread (%m)" );
 520         close( p_sys->i_fd );
 521         free( p_sys );
 522         return VLC_ENOMEM;
 523     }
 524
 525     return VLC_SUCCESS;
 526 }
 527
 528 /*****************************************************************************
 529  * Play: nothing to do
 530  *****************************************************************************/
 531 static void Play( aout_instance_t *p_aout )
 532 {
 533     VLC_UNUSED(p_aout);
 534 }
 535
 536 /*****************************************************************************
 537  * Close: close the DSP audio device
 538  *****************************************************************************/
 539 static void Close( vlc_object_t * p_this )
 540 {
 541     aout_instance_t *p_aout = (aout_instance_t *)p_this;
 542     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 543
 544     vlc_object_kill( p_aout );
 545     vlc_thread_join( p_aout );
 546     p_aout->b_die = false;
 547
 548     ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL );
 549     close( p_sys->i_fd );
 550
 551     free( p_sys );
 552 }
 553
 554 /*****************************************************************************
 555  * BufferDuration: buffer status query
 556  *****************************************************************************
 557  * This function returns the duration in microseconds of the current buffer.
 558  *****************************************************************************/
 559 static mtime_t BufferDuration( aout_instance_t * p_aout )
 560 {
 561     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 562     audio_buf_info audio_buf;
 563     int i_bytes;
 564
 565     /* Fill the audio_buf_info structure:
 566      * - fragstotal: total number of fragments allocated
 567      * - fragsize: size of a fragment in bytes
 568      * - bytes: available space in bytes (includes partially used fragments)
 569      * Note! 'bytes' could be more than fragments*fragsize */
 570     ioctl( p_sys->i_fd, SNDCTL_DSP_GETOSPACE, &audio_buf );
 571
 572     /* calculate number of available fragments (not partially used ones) */
 573     i_bytes = (audio_buf.fragstotal * audio_buf.fragsize) - audio_buf.bytes;
 574
 575     /* Return the fragment duration */
 576     return (mtime_t)i_bytes * 1000000
 577             / p_aout->output.output.i_bytes_per_frame
 578             / p_aout->output.output.i_rate
 579             * p_aout->output.output.i_frame_length;
 580 }
 581
 582 /*****************************************************************************
 583  * OSSThread: asynchronous thread used to DMA the data to the device
 584  *****************************************************************************/
 585 static void* OSSThread( vlc_object_t *p_this )
 586 {
 587     aout_instance_t * p_aout = (aout_instance_t*)p_this;
 588     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 589     mtime_t next_date = 0;
 590     int canc = vlc_savecancel ();
 591
 592     while ( vlc_object_alive (p_aout) )
 593     {
 594         aout_buffer_t * p_buffer = NULL;
 595         int i_tmp, i_size;
 596         uint8_t * p_bytes;
 597
 598         if ( p_aout->output.output.i_format != VLC_CODEC_SPDIFL )
 599         {
 600             mtime_t buffered = BufferDuration( p_aout );
 601
 602             if( p_aout->output.p_sys->b_workaround_buggy_driver )
 603             {
 604 #define i_fragstotal p_aout->output.p_sys->i_fragstotal
 605                 /* Wait a bit - we don't want our buffer to be full */
 606                 if( buffered > (p_aout->output.p_sys->max_buffer_duration
 607                                 / i_fragstotal * (i_fragstotal - 1)) )
 608                 {
 609                     msleep((p_aout->output.p_sys->max_buffer_duration
 610                                 / i_fragstotal ));
 611                     buffered = BufferDuration( p_aout );
 612                 }
 613 #undef i_fragstotal
 614             }
 615
 616             /* Next buffer will be played at mdate() + buffered */
 617             p_buffer = aout_OutputNextBuffer( p_aout, mdate() + buffered,
 618                                               false );
 619
 620             if( p_buffer == NULL &&
 621                 buffered > ( p_aout->output.p_sys->max_buffer_duration
 622                              / p_aout->output.p_sys->i_fragstotal ) )
 623             {
 624                 /* If we have at least a fragment full, then we can wait a
 625                  * little and retry to get a new audio buffer instead of
 626                  * playing a blank sample */
 627                 msleep( ( p_aout->output.p_sys->max_buffer_duration
 628                           / p_aout->output.p_sys->i_fragstotal / 2 ) );
 629                 continue;
 630             }
 631         }
 632         else
 633         {
 634             /* emu10k1 driver does not report Buffer Duration correctly in
 635              * passthrough mode so we have to cheat */
 636             if( !next_date )
 637             {
 638                 next_date = mdate();
 639             }
 640             else
 641             {
 642                 mtime_t delay = next_date - mdate();
 643                 if( delay > AOUT_PTS_TOLERANCE )
 644                 {
 645                     msleep( delay / 2 );
 646                 }
 647             }
 648
 649             while( vlc_object_alive (p_aout) && ! ( p_buffer =
 650                 aout_OutputNextBuffer( p_aout, next_date, true ) ) )
 651             {
 652                 msleep( VLC_HARD_MIN_SLEEP );
 653                 next_date = mdate();
 654             }
 655         }
 656
 657         if ( p_buffer != NULL )
 658         {
 659             p_bytes = p_buffer->p_buffer;
 660             i_size = p_buffer->i_buffer;
 661             /* This is theoretical ... we'll see next iteration whether
 662              * we're drifting */
 663             next_date += p_buffer->i_length;
 664         }
 665         else
 666         {
 667             i_size = FRAME_SIZE / p_aout->output.output.i_frame_length
 668                       * p_aout->output.output.i_bytes_per_frame;
 669             p_bytes = malloc( i_size );
 670             memset( p_bytes, 0, i_size );
 671             next_date = 0;
 672         }
 673
 674         i_tmp = write( p_sys->i_fd, p_bytes, i_size );
 675
 676         if( i_tmp < 0 )
 677         {
 678             msg_Err( p_aout, "write failed (%m)" );
 679         }
 680
 681         if ( p_buffer != NULL )
 682         {
 683             aout_BufferFree( p_buffer );
 684         }
 685         else
 686         {
 687             free( p_bytes );
 688         }
 689     }
 690
 691     vlc_restorecancel (canc);
 692     return NULL;
 693 }