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_file( "oss-audio-device", "/dev/dsp", aout_FindAndRestart,
 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_InheritInteger( p_aout, "spdif" ) )
 250                 var_Set( p_aout, "audio-device", val );
 251         }
 252         else if( var_InheritInteger( 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 (%i)", val.i_int );
 357         close( p_sys->i_fd );
 358         free( p_sys );
 359         return VLC_EGENERIC;
 360     }
 361
 362     var_SetBool( p_aout, "intf-change", true );
 363
 364     /* Reset the DSP device */
 365     if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 )
 366     {
 367         msg_Err( p_aout, "cannot reset OSS audio device" );
 368         close( p_sys->i_fd );
 369         free( p_sys );
 370         return VLC_EGENERIC;
 371     }
 372
 373     /* Set the output format */
 374     if ( AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
 375     {
 376         int i_format = AFMT_AC3;
 377
 378         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0
 379              || i_format != AFMT_AC3 )
 380         {
 381             msg_Err( p_aout, "cannot reset OSS audio device" );
 382             close( p_sys->i_fd );
 383             free( p_sys );
 384             return VLC_EGENERIC;
 385         }
 386
 387         p_aout->output.output.i_format = VLC_CODEC_SPDIFL;
 388         p_aout->output.i_nb_samples = A52_FRAME_NB;
 389         p_aout->output.output.i_bytes_per_frame = AOUT_SPDIF_SIZE;
 390         p_aout->output.output.i_frame_length = A52_FRAME_NB;
 391
 392         aout_VolumeNoneInit( p_aout );
 393     }
 394
 395     if ( !AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
 396     {
 397         unsigned int i_format = AFMT_S16_NE;
 398         unsigned int i_frame_size, i_fragments;
 399         unsigned int i_rate;
 400         unsigned int i_nb_channels;
 401         audio_buf_info audio_buf;
 402
 403         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
 404         {
 405             msg_Err( p_aout, "cannot set audio output format" );
 406             close( p_sys->i_fd );
 407             free( p_sys );
 408             return VLC_EGENERIC;
 409         }
 410
 411         switch ( i_format )
 412         {
 413         case AFMT_U8:
 414             p_aout->output.output.i_format = VLC_CODEC_U8;
 415             break;
 416         case AFMT_S8:
 417             p_aout->output.output.i_format = VLC_CODEC_S8;
 418             break;
 419         case AFMT_U16_LE:
 420             p_aout->output.output.i_format = VLC_CODEC_U16L;
 421             break;
 422         case AFMT_S16_LE:
 423             p_aout->output.output.i_format = VLC_CODEC_S16L;
 424             break;
 425         case AFMT_U16_BE:
 426             p_aout->output.output.i_format = VLC_CODEC_U16B;
 427             break;
 428         case AFMT_S16_BE:
 429             p_aout->output.output.i_format = VLC_CODEC_S16B;
 430             break;
 431         default:
 432             msg_Err( p_aout, "OSS fell back to an unknown format (%d)",
 433                      i_format );
 434             close( p_sys->i_fd );
 435             free( p_sys );
 436             return VLC_EGENERIC;
 437         }
 438
 439         i_nb_channels = aout_FormatNbChannels( &p_aout->output.output );
 440
 441         /* Set the number of channels */
 442         if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) < 0 ||
 443             i_nb_channels != aout_FormatNbChannels( &p_aout->output.output ) )
 444         {
 445             msg_Err( p_aout, "cannot set number of audio channels (%s)",
 446                      aout_FormatPrintChannels( &p_aout->output.output) );
 447             close( p_sys->i_fd );
 448             free( p_sys );
 449             return VLC_EGENERIC;
 450         }
 451
 452         /* Set the output rate */
 453         i_rate = p_aout->output.output.i_rate;
 454         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SPEED, &i_rate ) < 0 )
 455         {
 456             msg_Err( p_aout, "cannot set audio output rate (%i)",
 457                              p_aout->output.output.i_rate );
 458             close( p_sys->i_fd );
 459             free( p_sys );
 460             return VLC_EGENERIC;
 461         }
 462
 463         if( i_rate != p_aout->output.output.i_rate )
 464         {
 465             p_aout->output.output.i_rate = i_rate;
 466         }
 467
 468         /* Set the fragment size */
 469         aout_FormatPrepare( &p_aout->output.output );
 470
 471         /* i_fragment = xxxxyyyy where: xxxx        is fragtotal
 472          *                              1 << yyyy   is fragsize */
 473         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;
 474         i_fragments = 4;
 475         while( i_fragments < 12 && (1U << i_fragments) < i_frame_size )
 476         {
 477             ++i_fragments;
 478         }
 479         i_fragments |= FRAME_COUNT << 16;
 480         if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFRAGMENT, &i_fragments ) < 0 )
 481         {
 482             msg_Warn( p_aout, "cannot set fragment size (%.8x)", i_fragments );
 483         }
 484
 485         if( ioctl( p_sys->i_fd, SNDCTL_DSP_GETOSPACE, &audio_buf ) < 0 )
 486         {
 487             msg_Err( p_aout, "cannot get fragment size" );
 488             close( p_sys->i_fd );
 489             free( p_sys );
 490             return VLC_EGENERIC;
 491         }
 492         else
 493         {
 494             /* Number of fragments actually allocated */
 495             p_aout->output.p_sys->i_fragstotal = audio_buf.fragstotal;
 496
 497             /* Maximum duration the soundcard's buffer can hold */
 498             p_aout->output.p_sys->max_buffer_duration =
 499                 (mtime_t)audio_buf.fragstotal * audio_buf.fragsize * 1000000
 500                 / p_aout->output.output.i_bytes_per_frame
 501                 / p_aout->output.output.i_rate
 502                 * p_aout->output.output.i_frame_length;
 503
 504             p_aout->output.i_nb_samples = audio_buf.fragsize /
 505                 p_aout->output.output.i_bytes_per_frame;
 506         }
 507
 508         aout_VolumeSoftInit( p_aout );
 509     }
 510
 511     p_aout->output.p_sys->b_workaround_buggy_driver =
 512         var_InheritInteger( p_aout, "oss-buggy" );
 513
 514     /* Create OSS thread and wait for its readiness. */
 515     if( vlc_thread_create( p_aout, "aout", OSSThread,
 516                            VLC_THREAD_PRIORITY_OUTPUT ) )
 517     {
 518         msg_Err( p_aout, "cannot create OSS thread (%m)" );
 519         close( p_sys->i_fd );
 520         free( p_sys );
 521         return VLC_ENOMEM;
 522     }
 523
 524     return VLC_SUCCESS;
 525 }
 526
 527 /*****************************************************************************
 528  * Play: nothing to do
 529  *****************************************************************************/
 530 static void Play( aout_instance_t *p_aout )
 531 {
 532     VLC_UNUSED(p_aout);
 533 }
 534
 535 /*****************************************************************************
 536  * Close: close the DSP audio device
 537  *****************************************************************************/
 538 static void Close( vlc_object_t * p_this )
 539 {
 540     aout_instance_t *p_aout = (aout_instance_t *)p_this;
 541     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 542
 543     vlc_object_kill( p_aout );
 544     vlc_thread_join( p_aout );
 545     p_aout->b_die = false;
 546
 547     ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL );
 548     close( p_sys->i_fd );
 549
 550     free( p_sys );
 551 }
 552
 553 /*****************************************************************************
 554  * BufferDuration: buffer status query
 555  *****************************************************************************
 556  * This function returns the duration in microseconds of the current buffer.
 557  *****************************************************************************/
 558 static mtime_t BufferDuration( aout_instance_t * p_aout )
 559 {
 560     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 561     audio_buf_info audio_buf;
 562     int i_bytes;
 563
 564     /* Fill the audio_buf_info structure:
 565      * - fragstotal: total number of fragments allocated
 566      * - fragsize: size of a fragment in bytes
 567      * - bytes: available space in bytes (includes partially used fragments)
 568      * Note! 'bytes' could be more than fragments*fragsize */
 569     ioctl( p_sys->i_fd, SNDCTL_DSP_GETOSPACE, &audio_buf );
 570
 571     /* calculate number of available fragments (not partially used ones) */
 572     i_bytes = (audio_buf.fragstotal * audio_buf.fragsize) - audio_buf.bytes;
 573
 574     /* Return the fragment duration */
 575     return (mtime_t)i_bytes * 1000000
 576             / p_aout->output.output.i_bytes_per_frame
 577             / p_aout->output.output.i_rate
 578             * p_aout->output.output.i_frame_length;
 579 }
 580
 581 /*****************************************************************************
 582  * OSSThread: asynchronous thread used to DMA the data to the device
 583  *****************************************************************************/
 584 static void* OSSThread( vlc_object_t *p_this )
 585 {
 586     aout_instance_t * p_aout = (aout_instance_t*)p_this;
 587     struct aout_sys_t * p_sys = p_aout->output.p_sys;
 588     mtime_t next_date = 0;
 589     int canc = vlc_savecancel ();
 590
 591     while ( vlc_object_alive (p_aout) )
 592     {
 593         aout_buffer_t * p_buffer = NULL;
 594         int i_tmp, i_size;
 595         uint8_t * p_bytes;
 596
 597         if ( p_aout->output.output.i_format != VLC_CODEC_SPDIFL )
 598         {
 599             mtime_t buffered = BufferDuration( p_aout );
 600
 601             if( p_aout->output.p_sys->b_workaround_buggy_driver )
 602             {
 603 #define i_fragstotal p_aout->output.p_sys->i_fragstotal
 604                 /* Wait a bit - we don't want our buffer to be full */
 605                 if( buffered > (p_aout->output.p_sys->max_buffer_duration
 606                                 / i_fragstotal * (i_fragstotal - 1)) )
 607                 {
 608                     msleep((p_aout->output.p_sys->max_buffer_duration
 609                                 / i_fragstotal ));
 610                     buffered = BufferDuration( p_aout );
 611                 }
 612 #undef i_fragstotal
 613             }
 614
 615             /* Next buffer will be played at mdate() + buffered */
 616             p_buffer = aout_OutputNextBuffer( p_aout, mdate() + buffered,
 617                                               false );
 618
 619             if( p_buffer == NULL &&
 620                 buffered > ( p_aout->output.p_sys->max_buffer_duration
 621                              / p_aout->output.p_sys->i_fragstotal ) )
 622             {
 623                 /* If we have at least a fragment full, then we can wait a
 624                  * little and retry to get a new audio buffer instead of
 625                  * playing a blank sample */
 626                 msleep( ( p_aout->output.p_sys->max_buffer_duration
 627                           / p_aout->output.p_sys->i_fragstotal / 2 ) );
 628                 continue;
 629             }
 630         }
 631         else
 632         {
 633             /* emu10k1 driver does not report Buffer Duration correctly in
 634              * passthrough mode so we have to cheat */
 635             if( !next_date )
 636             {
 637                 next_date = mdate();
 638             }
 639             else
 640             {
 641                 mtime_t delay = next_date - mdate();
 642                 if( delay > AOUT_PTS_TOLERANCE )
 643                 {
 644                     msleep( delay / 2 );
 645                 }
 646             }
 647
 648             while( vlc_object_alive (p_aout) && ! ( p_buffer =
 649                 aout_OutputNextBuffer( p_aout, next_date, true ) ) )
 650             {
 651                 msleep( VLC_HARD_MIN_SLEEP );
 652                 next_date = mdate();
 653             }
 654         }
 655
 656         if ( p_buffer != NULL )
 657         {
 658             p_bytes = p_buffer->p_buffer;
 659             i_size = p_buffer->i_buffer;
 660             /* This is theoretical ... we'll see next iteration whether
 661              * we're drifting */
 662             next_date += p_buffer->i_length;
 663         }
 664         else
 665         {
 666             i_size = FRAME_SIZE / p_aout->output.output.i_frame_length
 667                       * p_aout->output.output.i_bytes_per_frame;
 668             p_bytes = malloc( i_size );
 669             memset( p_bytes, 0, i_size );
 670             next_date = 0;
 671         }
 672
 673         i_tmp = write( p_sys->i_fd, p_bytes, i_size );
 674
 675         if( i_tmp < 0 )
 676         {
 677             msg_Err( p_aout, "write failed (%m)" );
 678         }
 679
 680         if ( p_buffer != NULL )
 681         {
 682             aout_BufferFree( p_buffer );
 683         }
 684         else
 685         {
 686             free( p_bytes );
 687         }
 688     }
 689
 690     vlc_restorecancel (canc);
 691     return NULL;
 692 }