src/audio_output/dec.c

   1 /*****************************************************************************
   2  * dec.c : audio output API towards decoders
   3  *****************************************************************************
   4  * Copyright (C) 2002-2007 VLC authors and VideoLAN
   5  * $Id$
   6  *
   7  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU Lesser General Public License as published by
  11  * the Free Software Foundation; either version 2.1 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public License
  20  * along with this program; if not, write to the Free Software Foundation,
  21  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 /*****************************************************************************
  25  * Preamble
  26  *****************************************************************************/
  27 #ifdef HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #include <assert.h>
  32
  33 #include <vlc_common.h>
  34 #include <vlc_aout.h>
  35 #include <vlc_input.h>
  36
  37 #include "aout_internal.h"
  38 #include "libvlc.h"
  39
  40 /**
  41  * Creates an audio output
  42  */
  43 int aout_DecNew( audio_output_t *p_aout,
  44                  const audio_sample_format_t *p_format,
  45                  const audio_replay_gain_t *p_replay_gain,
  46                  const aout_request_vout_t *p_request_vout )
  47 {
  48     /* Sanitize audio format */
  49     if( p_format->i_channels != aout_FormatNbChannels( p_format ) )
  50     {
  51         msg_Err( p_aout, "incompatible audio channels count with layout mask" );
  52         return -1;
  53     }
  54
  55     if( p_format->i_rate > 352800 )
  56     {
  57         msg_Err( p_aout, "excessive audio sample frequency (%u)",
  58                  p_format->i_rate );
  59         return -1;
  60     }
  61     if( p_format->i_rate < 4000 )
  62     {
  63         msg_Err( p_aout, "too low audio sample frequency (%u)",
  64                  p_format->i_rate );
  65         return -1;
  66     }
  67
  68     var_Create (p_aout, "stereo-mode",
  69                 VLC_VAR_INTEGER | VLC_VAR_HASCHOICE | VLC_VAR_DOINHERIT);
  70     vlc_value_t txt;
  71     txt.psz_string = _("Stereo audio mode");
  72     var_Change (p_aout, "stereo-mode", VLC_VAR_SETTEXT, &txt, NULL);
  73
  74     aout_owner_t *owner = aout_owner(p_aout);
  75
  76     /* TODO: reduce lock scope depending on decoder's real need */
  77     aout_OutputLock (p_aout);
  78
  79     /* Create the audio output stream */
  80     owner->volume = aout_volume_New (p_aout, p_replay_gain);
  81
  82     atomic_store (&owner->restart, 0);
  83     owner->input_format = *p_format;
  84     owner->mixer_format = owner->input_format;
  85     owner->request_vout = *p_request_vout;
  86
  87     if (aout_OutputNew (p_aout, &owner->mixer_format))
  88         goto error;
  89     aout_volume_SetFormat (owner->volume, owner->mixer_format.i_format);
  90
  91     /* Create the audio filtering "input" pipeline */
  92     owner->filters = aout_FiltersNew (p_aout, p_format, &owner->mixer_format,
  93                                       &owner->request_vout);
  94     if (owner->filters == NULL)
  95     {
  96         aout_OutputDelete (p_aout);
  97 error:
  98         aout_volume_Delete (owner->volume);
  99         aout_OutputUnlock (p_aout);
 100         var_Destroy (p_aout, "stereo-mode");
 101         return -1;
 102     }
 103
 104     owner->sync.end = VLC_TS_INVALID;
 105     owner->sync.resamp_type = AOUT_RESAMPLING_NONE;
 106     owner->sync.discontinuity = true;
 107     aout_OutputUnlock (p_aout);
 108
 109     atomic_init (&owner->buffers_lost, 0);
 110     return 0;
 111 }
 112
 113 /**
 114  * Stops all plugins involved in the audio output.
 115  */
 116 void aout_DecDelete (audio_output_t *aout)
 117 {
 118     aout_owner_t *owner = aout_owner (aout);
 119
 120     aout_OutputLock (aout);
 121     if (owner->mixer_format.i_format)
 122     {
 123         aout_FiltersDelete (aout, owner->filters);
 124         aout_OutputDelete (aout);
 125     }
 126     aout_volume_Delete (owner->volume);
 127     aout_OutputUnlock (aout);
 128     var_Destroy (aout, "stereo-mode");
 129 }
 130
 131 static int aout_CheckReady (audio_output_t *aout)
 132 {
 133     aout_owner_t *owner = aout_owner (aout);
 134
 135     int restart = atomic_exchange (&owner->restart, 0);
 136     if (unlikely(restart))
 137     {
 138         if (owner->mixer_format.i_format)
 139             aout_FiltersDelete (aout, owner->filters);
 140
 141         if (restart & AOUT_RESTART_OUTPUT)
 142         {   /* Reinitializes the output */
 143             msg_Dbg (aout, "restarting output...");
 144             if (owner->mixer_format.i_format)
 145                 aout_OutputDelete (aout);
 146             owner->mixer_format = owner->input_format;
 147             if (aout_OutputNew (aout, &owner->mixer_format))
 148                 owner->mixer_format.i_format = 0;
 149             aout_volume_SetFormat (owner->volume,
 150                                    owner->mixer_format.i_format);
 151         }
 152
 153         msg_Dbg (aout, "restarting filters...");
 154         owner->sync.end = VLC_TS_INVALID;
 155         owner->sync.resamp_type = AOUT_RESAMPLING_NONE;
 156
 157         if (owner->mixer_format.i_format)
 158         {
 159             owner->filters = aout_FiltersNew (aout, &owner->input_format,
 160                                               &owner->mixer_format,
 161                                               &owner->request_vout);
 162             if (owner->filters == NULL)
 163             {
 164                 aout_OutputDelete (aout);
 165                 owner->mixer_format.i_format = 0;
 166             }
 167         }
 168         /* TODO: This would be a good time to call clean up any video output
 169          * left over by an audio visualization:
 170         input_resource_TerminatVout(MAGIC HERE); */
 171     }
 172     return (owner->mixer_format.i_format) ? 0 : -1;
 173 }
 174
 175 /**
 176  * Marks the audio output for restart, to update any parameter of the output
 177  * plug-in (e.g. output device or channel mapping).
 178  */
 179 void aout_RequestRestart (audio_output_t *aout, unsigned mode)
 180 {
 181     aout_owner_t *owner = aout_owner (aout);
 182     atomic_fetch_or (&owner->restart, mode);
 183     msg_Dbg (aout, "restart requested (%u)", mode);
 184 }
 185
 186 /*
 187  * Buffer management
 188  */
 189
 190 static void aout_StopResampling (audio_output_t *aout)
 191 {
 192     aout_owner_t *owner = aout_owner (aout);
 193
 194     owner->sync.resamp_type = AOUT_RESAMPLING_NONE;
 195     aout_FiltersAdjustResampling (owner->filters, 0);
 196 }
 197
 198 static void aout_DecSilence (audio_output_t *aout, mtime_t length, mtime_t pts)
 199 {
 200     aout_owner_t *owner = aout_owner (aout);
 201     const audio_sample_format_t *fmt = &owner->mixer_format;
 202     size_t frames = (fmt->i_rate * length) / CLOCK_FREQ;
 203     block_t *block;
 204
 205     if (AOUT_FMT_SPDIF(fmt))
 206         block = block_Alloc (4 * frames);
 207     else
 208         block = block_Alloc (frames * fmt->i_bytes_per_frame);
 209     if (unlikely(block == NULL))
 210         return; /* uho! */
 211
 212     msg_Dbg (aout, "inserting %zu zeroes", frames);
 213     memset (block->p_buffer, 0, block->i_buffer);
 214     block->i_nb_samples = frames;
 215     block->i_pts = pts;
 216     block->i_dts = pts;
 217     block->i_length = length;
 218     aout_OutputPlay (aout, block);
 219 }
 220
 221 static void aout_DecSynchronize (audio_output_t *aout, mtime_t dec_pts,
 222                                  int input_rate)
 223 {
 224     aout_owner_t *owner = aout_owner (aout);
 225     mtime_t drift;
 226
 227     /**
 228      * Depending on the drift between the actual and intended playback times,
 229      * the audio core may ignore the drift, trigger upsampling or downsampling,
 230      * insert silence or even discard samples.
 231      * Future VLC versions may instead adjust the input rate.
 232      *
 233      * The audio output plugin is responsible for estimating its actual
 234      * playback time, or rather the estimated time when the next sample will
 235      * be played. (The actual playback time is always the current time, that is
 236      * to say mdate(). It is not an useful statistic.)
 237      *
 238      * Most audio output plugins can estimate the delay until playback of
 239      * the next sample to be written to the buffer, or equally the time until
 240      * all samples in the buffer will have been played. Then:
 241      *    pts = mdate() + delay
 242      */
 243     if (aout_OutputTimeGet (aout, &drift) != 0)
 244         return; /* nothing can be done if timing is unknown */
 245     drift += mdate () - dec_pts;
 246
 247     /* Late audio output.
 248      * This can happen due to insufficient caching, scheduling jitter
 249      * or bug in the decoder. Ideally, the output would seek backward. But that
 250      * is not portable, not supported by some hardware and often unsafe/buggy
 251      * where supported. The other alternative is to flush the buffers
 252      * completely. */
 253     if (drift > (owner->sync.discontinuity ? 0
 254                   : +3 * input_rate * AOUT_MAX_PTS_DELAY / INPUT_RATE_DEFAULT))
 255     {
 256         if (!owner->sync.discontinuity)
 257             msg_Warn (aout, "playback way too late (%"PRId64"): "
 258                       "flushing buffers", drift);
 259         else
 260             msg_Dbg (aout, "playback too late (%"PRId64"): "
 261                      "flushing buffers", drift);
 262         aout_OutputFlush (aout, false);
 263
 264         aout_StopResampling (aout);
 265         owner->sync.end = VLC_TS_INVALID;
 266         owner->sync.discontinuity = true;
 267
 268         /* Now the output might be too early... Recheck. */
 269         if (aout_OutputTimeGet (aout, &drift) != 0)
 270             return; /* nothing can be done if timing is unknown */
 271         drift += mdate () - dec_pts;
 272     }
 273
 274     /* Early audio output.
 275      * This is rare except at startup when the buffers are still empty. */
 276     if (drift < (owner->sync.discontinuity ? 0
 277                 : -3 * input_rate * AOUT_MAX_PTS_ADVANCE / INPUT_RATE_DEFAULT))
 278     {
 279         if (!owner->sync.discontinuity)
 280             msg_Warn (aout, "playback way too early (%"PRId64"): "
 281                       "playing silence", drift);
 282         aout_DecSilence (aout, -drift, dec_pts);
 283
 284         aout_StopResampling (aout);
 285         owner->sync.discontinuity = true;
 286         drift = 0;
 287     }
 288
 289     /* Resampling */
 290     if (drift > +AOUT_MAX_PTS_DELAY
 291      && owner->sync.resamp_type != AOUT_RESAMPLING_UP)
 292     {
 293         msg_Warn (aout, "playback too late (%"PRId64"): up-sampling",
 294                   drift);
 295         owner->sync.resamp_type = AOUT_RESAMPLING_UP;
 296         owner->sync.resamp_start_drift = +drift;
 297     }
 298     if (drift < -AOUT_MAX_PTS_ADVANCE
 299      && owner->sync.resamp_type != AOUT_RESAMPLING_DOWN)
 300     {
 301         msg_Warn (aout, "playback too early (%"PRId64"): down-sampling",
 302                   drift);
 303         owner->sync.resamp_type = AOUT_RESAMPLING_DOWN;
 304         owner->sync.resamp_start_drift = -drift;
 305     }
 306
 307     if (owner->sync.resamp_type == AOUT_RESAMPLING_NONE)
 308         return; /* Everything is fine. Nothing to do. */
 309
 310     if (llabs (drift) > 2 * owner->sync.resamp_start_drift)
 311     {   /* If the drift is ever increasing, then something is seriously wrong.
 312          * Cease resampling and hope for the best. */
 313         msg_Warn (aout, "timing screwed (drift: %"PRId64" us): "
 314                   "stopping resampling", drift);
 315         aout_StopResampling (aout);
 316         return;
 317     }
 318
 319     /* Resampling has been triggered earlier. This checks if it needs to be
 320      * increased or decreased. Resampling rate changes must be kept slow for
 321      * the comfort of listeners. */
 322     int adj = (owner->sync.resamp_type == AOUT_RESAMPLING_UP) ? +2 : -2;
 323
 324     if (2 * llabs (drift) <= owner->sync.resamp_start_drift)
 325         /* If the drift has been reduced from more than half its initial
 326          * value, then it is time to switch back the resampling direction. */
 327         adj *= -1;
 328
 329     if (!aout_FiltersAdjustResampling (owner->filters, adj))
 330     {   /* Everything is back to normal: stop resampling. */
 331         owner->sync.resamp_type = AOUT_RESAMPLING_NONE;
 332         msg_Dbg (aout, "resampling stopped (drift: %"PRId64" us)", drift);
 333     }
 334 }
 335
 336 /*****************************************************************************
 337  * aout_DecPlay : filter & mix the decoded buffer
 338  *****************************************************************************/
 339 int aout_DecPlay (audio_output_t *aout, block_t *block, int input_rate)
 340 {
 341     aout_owner_t *owner = aout_owner (aout);
 342
 343     assert (input_rate >= INPUT_RATE_DEFAULT / AOUT_MAX_INPUT_RATE);
 344     assert (input_rate <= INPUT_RATE_DEFAULT * AOUT_MAX_INPUT_RATE);
 345     assert (block->i_pts >= VLC_TS_0);
 346
 347     block->i_length = CLOCK_FREQ * block->i_nb_samples
 348                                  / owner->input_format.i_rate;
 349
 350     aout_OutputLock (aout);
 351     if (unlikely(aout_CheckReady (aout)))
 352         goto drop; /* Pipeline is unrecoverably broken :-( */
 353
 354     const mtime_t now = mdate (), advance = block->i_pts - now;
 355     if (advance < -AOUT_MAX_PTS_DELAY)
 356     {   /* Late buffer can be caused by bugs in the decoder, by scheduling
 357          * latency spikes (excessive load, SIGSTOP, etc.) or if buffering is
 358          * insufficient. We assume the PTS is wrong and play the buffer anyway:
 359          * Hopefully video has encountered a similar PTS problem as audio. */
 360         msg_Warn (aout, "buffer too late (%"PRId64" us): dropped", advance);
 361         goto drop;
 362     }
 363     if (advance > AOUT_MAX_ADVANCE_TIME)
 364     {   /* Early buffers can only be caused by bugs in the decoder. */
 365         msg_Err (aout, "buffer too early (%"PRId64" us): dropped", advance);
 366         goto drop;
 367     }
 368     if (block->i_flags & BLOCK_FLAG_DISCONTINUITY)
 369         owner->sync.discontinuity = true;
 370
 371     block = aout_FiltersPlay (owner->filters, block, input_rate);
 372     if (block == NULL)
 373         goto lost;
 374
 375     /* Software volume */
 376     aout_volume_Amplify (owner->volume, block);
 377
 378     /* Drift correction */
 379     aout_DecSynchronize (aout, block->i_pts, input_rate);
 380
 381     /* Output */
 382     owner->sync.end = block->i_pts + block->i_length + 1;
 383     owner->sync.discontinuity = false;
 384     aout_OutputPlay (aout, block);
 385 out:
 386     aout_OutputUnlock (aout);
 387     return 0;
 388 drop:
 389     owner->sync.discontinuity = true;
 390     block_Release (block);
 391 lost:
 392     atomic_fetch_add(&owner->buffers_lost, 1);
 393     goto out;
 394 }
 395
 396 int aout_DecGetResetLost (audio_output_t *aout)
 397 {
 398     aout_owner_t *owner = aout_owner (aout);
 399     return atomic_exchange(&owner->buffers_lost, 0);
 400 }
 401
 402 void aout_DecChangePause (audio_output_t *aout, bool paused, mtime_t date)
 403 {
 404     aout_owner_t *owner = aout_owner (aout);
 405
 406     aout_OutputLock (aout);
 407     if (owner->sync.end != VLC_TS_INVALID)
 408     {
 409         if (paused)
 410             owner->sync.end -= date;
 411         else
 412             owner->sync.end += date;
 413     }
 414     if (owner->mixer_format.i_format)
 415         aout_OutputPause (aout, paused, date);
 416     aout_OutputUnlock (aout);
 417 }
 418
 419 void aout_DecFlush (audio_output_t *aout, bool wait)
 420 {
 421     aout_owner_t *owner = aout_owner (aout);
 422
 423     aout_OutputLock (aout);
 424     owner->sync.end = VLC_TS_INVALID;
 425     if (owner->mixer_format.i_format)
 426         aout_OutputFlush (aout, wait);
 427     aout_OutputUnlock (aout);
 428 }