include/vlc_aout.h

   1 /*****************************************************************************
   2  * vlc_aout.h : audio output interface
   3  *****************************************************************************
   4  * Copyright (C) 2002-2011 VLC authors and VideoLAN
   5  *
   6  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU Lesser General Public License as published by
  10  * the Free Software Foundation; either version 2.1 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public License
  19  * along with this program; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  21  *****************************************************************************/
  22
  23 #ifndef VLC_AOUT_H
  24 #define VLC_AOUT_H 1
  25
  26 #include <assert.h>
  27 #include <vlc_list.h>
  28
  29 /**
  30  * \defgroup audio_output Audio output
  31  * \ingroup output
  32  * @{
  33  * \file
  34  * Audio output modules interface
  35  */
  36
  37 /* Buffers which arrive in advance of more than AOUT_MAX_ADVANCE_TIME
  38  * will be considered as bogus and be trashed */
  39 #define AOUT_MAX_ADVANCE_TIME           (AOUT_MAX_PREPARE_TIME + VLC_TICK_FROM_SEC(1))
  40
  41 /* Buffers which arrive in advance of more than AOUT_MAX_PREPARE_TIME
  42  * will cause the calling thread to sleep */
  43 #define AOUT_MAX_PREPARE_TIME           VLC_TICK_FROM_SEC(2)
  44
  45 /* Buffers which arrive after pts - AOUT_MIN_PREPARE_TIME will be trashed
  46  * to avoid too heavy resampling */
  47 #define AOUT_MIN_PREPARE_TIME           AOUT_MAX_PTS_ADVANCE
  48
  49 /* Tolerance values from EBU Recommendation 37 */
  50 /** Maximum advance of actual audio playback time to coded PTS,
  51  * above which downsampling will be performed */
  52 #define AOUT_MAX_PTS_ADVANCE            VLC_TICK_FROM_MS(40)
  53
  54 /** Maximum delay of actual audio playback time from coded PTS,
  55  * above which upsampling will be performed */
  56 #define AOUT_MAX_PTS_DELAY              VLC_TICK_FROM_MS(60)
  57
  58 /* Max acceptable resampling (in %) */
  59 #define AOUT_MAX_RESAMPLING             10
  60
  61 #include "vlc_es.h"
  62
  63 #define AOUT_FMTS_IDENTICAL( p_first, p_second ) (                          \
  64     ((p_first)->i_format == (p_second)->i_format)                           \
  65       && AOUT_FMTS_SIMILAR(p_first, p_second) )
  66
  67 /* Check if i_rate == i_rate and i_channels == i_channels */
  68 #define AOUT_FMTS_SIMILAR( p_first, p_second ) (                            \
  69     ((p_first)->i_rate == (p_second)->i_rate)                               \
  70       && ((p_first)->channel_type == (p_second)->channel_type)            \
  71       && ((p_first)->i_physical_channels == (p_second)->i_physical_channels)\
  72       && ((p_first)->i_chan_mode == (p_second)->i_chan_mode) )
  73
  74 #define AOUT_FMT_LINEAR( p_format ) \
  75     (aout_BitsPerSample((p_format)->i_format) != 0)
  76
  77 #define VLC_CODEC_SPDIFL VLC_FOURCC('s','p','d','i')
  78 #define VLC_CODEC_SPDIFB VLC_FOURCC('s','p','d','b')
  79
  80 #define AOUT_FMT_SPDIF( p_format ) \
  81     ( ((p_format)->i_format == VLC_CODEC_SPDIFL)       \
  82        || ((p_format)->i_format == VLC_CODEC_SPDIFB)   \
  83        || ((p_format)->i_format == VLC_CODEC_A52)      \
  84        || ((p_format)->i_format == VLC_CODEC_DTS) )
  85
  86 #define AOUT_FMT_HDMI( p_format )                   \
  87     ( (p_format)->i_format == VLC_CODEC_EAC3        \
  88     ||(p_format)->i_format == VLC_CODEC_DTSHD       \
  89     ||(p_format)->i_format == VLC_CODEC_TRUEHD      \
  90     ||(p_format)->i_format == VLC_CODEC_MLP         \
  91     )
  92
  93 /* Values used for the audio-channels object variable */
  94 #define AOUT_VAR_CHAN_UNSET         0 /* must be zero */
  95 #define AOUT_VAR_CHAN_STEREO        1
  96 #define AOUT_VAR_CHAN_RSTEREO       2
  97 #define AOUT_VAR_CHAN_LEFT          3
  98 #define AOUT_VAR_CHAN_RIGHT         4
  99 #define AOUT_VAR_CHAN_DOLBYS        5
 100 #define AOUT_VAR_CHAN_HEADPHONES    6
 101 #define AOUT_VAR_CHAN_MONO          7
 102
 103 /*****************************************************************************
 104  * Main audio output structures
 105  *****************************************************************************/
 106
 107 /* Size of a frame for S/PDIF output. */
 108 #define AOUT_SPDIF_SIZE 6144
 109
 110 /* Number of samples in an A/52 frame. */
 111 #define A52_FRAME_NB 1536
 112
 113 /* FIXME to remove once aout.h is cleaned a bit more */
 114 #include <vlc_block.h>
 115
 116 struct vlc_audio_output_events {
 117     void (*timing_report)(audio_output_t *, vlc_tick_t system_now, vlc_tick_t pts);
 118     void (*volume_report)(audio_output_t *, float);
 119     void (*mute_report)(audio_output_t *, bool);
 120     void (*policy_report)(audio_output_t *, bool);
 121     void (*device_report)(audio_output_t *, const char *);
 122     void (*hotplug_report)(audio_output_t *, const char *, const char *);
 123     void (*restart_request)(audio_output_t *, unsigned);
 124     int (*gain_request)(audio_output_t *, float);
 125 };
 126
 127 /** Audio output object
 128  *
 129  * The audio output object is the abstraction for rendering decoded
 130  * (or pass-through) audio samples. In addition to playing samples,
 131  * the abstraction exposes controls for pause/resume, flush/drain,
 132  * changing the volume or mut flag, and listing and changing output device.
 133  *
 134  * An audio output can be in one of three different states:
 135  * stopped, playing or paused.
 136  * The audio output is always created in stopped state and is always destroyed
 137  * in that state also. It is moved from stopped to playing state by start(),
 138  * and from playing or paused states back to stopped state by stop().
 139  **/
 140 struct audio_output
 141 {
 142     struct vlc_object_t obj;
 143
 144     void *sys; /**< Private data for callbacks */
 145
 146     int (*start)(audio_output_t *, audio_sample_format_t *fmt);
 147     /**< Starts a new stream (mandatory, cannot be NULL).
 148       *
 149       * This callback changes the audio output from stopped to playing state
 150       * (if succesful). After the callback returns, time_get(), play(),
 151       * pause(), flush() and eventually stop() callbacks may be called.
 152       *
 153       * \param fmt input stream sample format upon entry,
 154       *            output stream sample format upon return [IN/OUT]
 155       * \return VLC_SUCCESS on success, non-zero on failure
 156       *
 157       * \note This callback can only be called while the audio output is in
 158       * stopped state. There can be only one stream per audio output at a time.
 159       *
 160       * \note This callbacks needs not be reentrant.
 161       */
 162
 163     void (*stop)(audio_output_t *);
 164     /**< Stops the existing stream (mandatory, cannot be NULL).
 165       *
 166       * This callback terminates the current audio stream,
 167       * and returns the audio output to stopped state.
 168       *
 169       * \note This callback needs not be reentrant.
 170       */
 171
 172     int (*time_get)(audio_output_t *, vlc_tick_t *delay);
 173     /**< Estimates playback buffer latency (mandatory, cannot be NULL).
 174       *
 175       * This callback computes an estimation of the delay until the current
 176       * tail of the audio output buffer would be rendered. This is essential
 177       * for (lip) synchronization and long term drift between the audio output
 178       * clock and the media upstream clock (if any).
 179       *
 180       * If the audio output clock is exactly synchronized with the system
 181       * monotonic clock (i.e. vlc_tick_now()), then aout_TimeGetDefault() can
 182       * implement this callback. In that case, drain must be implemented (since
 183       * the default implementation uses the delay to wait for the end of the
 184       * stream).
 185       *
 186       * This callback is called before the first play() in order to get the
 187       * initial delay (the hw latency). Most modules won't be able to know this
 188       * latency before the first play. In that case, they should return -1 and
 189       * handle the first play() date, cf. play() documentation.
 190       *
 191       * \param delay pointer to the delay until the next sample to be written
 192       *              to the playback buffer is rendered [OUT]
 193       * \return 0 on success, non-zero on failure or lack of data
 194       *
 195       * \note This callback cannot be called in stopped state.
 196       */
 197
 198     void (*play)(audio_output_t *, block_t *block, vlc_tick_t date);
 199     /**< Queues a block of samples for playback (mandatory, cannot be NULL).
 200       *
 201       * The first play() date (after a flush()/start()) will be most likely in
 202       * the future. Modules that don't know the hw latency before a first play
 203       * (when they return -1 from the first time_get()) will need to handle
 204       * this. They can play a silence buffer with 'length = date - now()', or
 205       * configure their render callback to start at the given date.
 206       *
 207       * \param block block of audio samples
 208       * \param date intended system time to render the first sample
 209       *
 210       * \note This callback cannot be called in stopped state.
 211       */
 212
 213     void (*pause)( audio_output_t *, bool pause, vlc_tick_t date);
 214     /**< Pauses or resumes playback (mandatory, cannot be NULL).
 215       *
 216       * This callback pauses or resumes audio playback as quickly as possible.
 217       * When pausing, it is desirable to stop producing sound immediately, but
 218       * retain already queued audio samples in the buffer to play when later
 219       * when resuming.
 220       *
 221       * If pausing is impossible, then aout_PauseDefault() can provide a
 222       * fallback implementation of this callback.
 223       *
 224       * \param pause pause if true, resume from pause if false
 225       * \param date timestamp when the pause or resume was requested
 226       *
 227       * \note This callback cannot be called in stopped state.
 228       */
 229
 230     void (*flush)( audio_output_t *);
 231     /**< Flushes the playback buffers (mandatory, cannot be NULL).
 232       *
 233       * \param wait true to wait for playback of pending buffers (drain),
 234       *             false to discard pending buffers (flush)
 235       *
 236       * \note This callback cannot be called in stopped state.
 237       */
 238     void (*drain)(audio_output_t *);
 239     /**< Drain the playback buffers (can be NULL).
 240       *
 241       * If NULL, the caller will wait for the delay returned by time_get before
 242       * calling stop().
 243       */
 244
 245     int (*volume_set)(audio_output_t *, float volume);
 246     /**< Changes playback volume (optional, may be NULL).
 247       *
 248       * \param volume requested volume (0. = mute, 1. = nominal)
 249       *
 250       * \note The volume is always a positive number.
 251       *
 252       * \warning A stream may or may not have been started when called.
 253       * \warning This callback may be called concurrently with
 254       * time_get(), play(), pause() or flush().
 255       * It will however be protected against concurrent calls to
 256       * start(), stop(), volume_set(), mute_set() or device_select().
 257       */
 258
 259     int (*mute_set)(audio_output_t *, bool mute);
 260     /**< Changes muting (optinal, may be NULL).
 261       *
 262       * \param mute true to mute, false to unmute
 263       * \warning The same constraints apply as with volume_set().
 264       */
 265
 266     int (*device_select)(audio_output_t *, const char *id);
 267     /**< Selects an audio output device (optional, may be NULL).
 268       *
 269       * \param id nul-terminated device unique identifier.
 270       * \return 0 on success, non-zero on failure.
 271       *
 272       * \warning The same constraints apply as with volume_set().
 273       */
 274
 275     struct {
 276         bool headphones; /**< Default to false, set it to true if the current
 277                               sink is using headphones */
 278     } current_sink_info;
 279     /**< Current sink informations set by the module from the start() function */
 280
 281     const struct vlc_audio_output_events *events;
 282 };
 283
 284 typedef enum
 285 {
 286     AOUT_CHANIDX_DISABLE = -1,
 287     AOUT_CHANIDX_LEFT,
 288     AOUT_CHANIDX_RIGHT,
 289     AOUT_CHANIDX_MIDDLELEFT,
 290     AOUT_CHANIDX_MIDDLERIGHT,
 291     AOUT_CHANIDX_REARLEFT,
 292     AOUT_CHANIDX_REARRIGHT,
 293     AOUT_CHANIDX_REARCENTER,
 294     AOUT_CHANIDX_CENTER,
 295     AOUT_CHANIDX_LFE,
 296     AOUT_CHANIDX_MAX
 297 } vlc_chan_order_idx_t;
 298
 299 static_assert(AOUT_CHANIDX_MAX == AOUT_CHAN_MAX, "channel count mismatch");
 300
 301 #define AOUT_CHAN_REMAP_INIT { \
 302     AOUT_CHANIDX_LEFT,  \
 303     AOUT_CHANIDX_RIGHT, \
 304     AOUT_CHANIDX_MIDDLELEFT, \
 305     AOUT_CHANIDX_MIDDLERIGHT, \
 306     AOUT_CHANIDX_REARLEFT, \
 307     AOUT_CHANIDX_REARRIGHT, \
 308     AOUT_CHANIDX_REARCENTER, \
 309     AOUT_CHANIDX_CENTER, \
 310     AOUT_CHANIDX_LFE, \
 311 }
 312
 313 /**
 314  * It describes the audio channel order VLC expect.
 315  */
 316 static const uint32_t pi_vlc_chan_order_wg4[] =
 317 {
 318     AOUT_CHAN_LEFT, AOUT_CHAN_RIGHT,
 319     AOUT_CHAN_MIDDLELEFT, AOUT_CHAN_MIDDLERIGHT,
 320     AOUT_CHAN_REARLEFT, AOUT_CHAN_REARRIGHT, AOUT_CHAN_REARCENTER,
 321     AOUT_CHAN_CENTER, AOUT_CHAN_LFE, 0
 322 };
 323
 324 #define AOUT_RESTART_FILTERS        0x1
 325 #define AOUT_RESTART_OUTPUT         (AOUT_RESTART_FILTERS|0x2)
 326 #define AOUT_RESTART_STEREOMODE     (AOUT_RESTART_OUTPUT|0x4)
 327
 328 /*****************************************************************************
 329  * Prototypes
 330  *****************************************************************************/
 331
 332 /**
 333  * This function computes the reordering needed to go from pi_chan_order_in to
 334  * pi_chan_order_out.
 335  * If pi_chan_order_in or pi_chan_order_out is NULL, it will assume that vlc
 336  * internal (WG4) order is requested.
 337  */
 338 VLC_API unsigned aout_CheckChannelReorder( const uint32_t *, const uint32_t *,
 339                                            uint32_t mask, uint8_t *table );
 340 VLC_API void aout_ChannelReorder(void *, size_t, uint8_t, const uint8_t *, vlc_fourcc_t);
 341
 342 VLC_API void aout_Interleave(void *dst, const void *const *planes,
 343                              unsigned samples, unsigned channels,
 344                              vlc_fourcc_t fourcc);
 345 VLC_API void aout_Deinterleave(void *dst, const void *src, unsigned samples,
 346                              unsigned channels, vlc_fourcc_t fourcc);
 347
 348 /**
 349  * This function will compute the extraction parameter into pi_selection to go
 350  * from i_channels with their type given by pi_order_src[] into the order
 351  * describe by pi_order_dst.
 352  * It will also set :
 353  * - *pi_channels as the number of channels that will be extracted which is
 354  * lower (in case of non understood channels type) or equal to i_channels.
 355  * - the layout of the channels (*pi_layout).
 356  *
 357  * It will return true if channel extraction is really needed, in which case
 358  * aout_ChannelExtract must be used
 359  *
 360  * XXX It must be used when the source may have channel type not understood
 361  * by VLC. In this case the channel type pi_order_src[] must be set to 0.
 362  * XXX It must also be used if multiple channels have the same type.
 363  */
 364 VLC_API bool aout_CheckChannelExtraction( int *pi_selection, uint32_t *pi_layout, int *pi_channels, const uint32_t pi_order_dst[AOUT_CHAN_MAX], const uint32_t *pi_order_src, int i_channels );
 365
 366 /**
 367  * Do the actual channels extraction using the parameters created by
 368  * aout_CheckChannelExtraction.
 369  *
 370  * XXX this function does not work in place (p_dst and p_src must not overlap).
 371  * XXX Only 8, 16, 32, 64 bits per sample are supported.
 372  */
 373 VLC_API void aout_ChannelExtract( void *p_dst, int i_dst_channels, const void *p_src, int i_src_channels, int i_sample_count, const int *pi_selection, int i_bits_per_sample );
 374
 375 /* */
 376 static inline unsigned aout_FormatNbChannels(const audio_sample_format_t *fmt)
 377 {
 378     return vlc_popcount(fmt->i_physical_channels);
 379 }
 380
 381 VLC_API unsigned int aout_BitsPerSample( vlc_fourcc_t i_format ) VLC_USED;
 382 VLC_API void aout_FormatPrepare( audio_sample_format_t * p_format );
 383 VLC_API void aout_FormatPrint(vlc_object_t *, const char *,
 384                               const audio_sample_format_t *);
 385 #define aout_FormatPrint(o, t, f) aout_FormatPrint(VLC_OBJECT(o), t, f)
 386 VLC_API const char * aout_FormatPrintChannels( const audio_sample_format_t * ) VLC_USED;
 387
 388 #define AOUT_VOLUME_DEFAULT             256
 389 #define AOUT_VOLUME_MAX                 512
 390
 391 VLC_API float aout_VolumeGet (audio_output_t *);
 392 VLC_API int aout_VolumeSet (audio_output_t *, float);
 393 VLC_API int aout_VolumeUpdate (audio_output_t *, int, float *);
 394 VLC_API int aout_MuteGet (audio_output_t *);
 395 VLC_API int aout_MuteSet (audio_output_t *, bool);
 396 VLC_API char *aout_DeviceGet (audio_output_t *);
 397 VLC_API int aout_DeviceSet (audio_output_t *, const char *);
 398 VLC_API int aout_DevicesList (audio_output_t *, char ***, char ***);
 399
 400 /**
 401  * Report change of configured audio volume to the core and UI.
 402  */
 403 static inline void aout_VolumeReport(audio_output_t *aout, float volume)
 404 {
 405     aout->events->volume_report(aout, volume);
 406 }
 407
 408 /**
 409  * Report change of muted flag to the core and UI.
 410  */
 411 static inline void aout_MuteReport(audio_output_t *aout, bool mute)
 412 {
 413     aout->events->mute_report(aout, mute);
 414 }
 415
 416 /**
 417  * Report audio policy status.
 418  * \param cork true to request a cork, false to undo any pending cork.
 419  */
 420 static inline void aout_PolicyReport(audio_output_t *aout, bool cork)
 421 {
 422     aout->events->policy_report(aout, cork);
 423 }
 424
 425 /**
 426  * Report change of output device.
 427  */
 428 static inline void aout_DeviceReport(audio_output_t *aout, const char *id)
 429 {
 430     aout->events->device_report(aout, id);
 431 }
 432
 433 /**
 434  * Report a device hot-plug event.
 435  * @param id device ID
 436  * @param name human-readable device name (NULL for hot unplug)
 437  */
 438 static inline void aout_HotplugReport(audio_output_t *aout,
 439                                       const char *id, const char *name)
 440 {
 441     aout->events->hotplug_report(aout, id, name);
 442 }
 443
 444 /**
 445  * Request a change of software audio amplification.
 446  * \param gain linear amplitude gain (must be positive)
 447  * \warning Values in excess 1.0 may cause overflow and distorsion.
 448  */
 449 static inline int aout_GainRequest(audio_output_t *aout, float gain)
 450 {
 451     return aout->events->gain_request(aout, gain);
 452 }
 453
 454 static inline void aout_RestartRequest(audio_output_t *aout, unsigned mode)
 455 {
 456     aout->events->restart_request(aout, mode);
 457 }
 458
 459 /**
 460  * Default implementation for audio_output_t.time_get
 461  */
 462 static inline int aout_TimeGetDefault(audio_output_t *aout,
 463                                       vlc_tick_t *restrict delay)
 464 {
 465     (void) aout; (void) delay;
 466     return -1;
 467 }
 468
 469 /**
 470  * Default implementation for audio_output_t.pause
 471  *
 472  * \warning This default callback implementation is suboptimal as it will
 473  * discard some audio samples.
 474  * Do not use this unless there are really no possible better alternatives.
 475  */
 476 static inline void aout_PauseDefault(audio_output_t *aout, bool paused,
 477                                      vlc_tick_t date)
 478 {
 479     if (paused)
 480         aout->flush(aout);
 481     (void) date;
 482 }
 483
 484 /* Audio output filters */
 485
 486 /**
 487  * Enable or disable an audio filter ("audio-filter")
 488  *
 489  * \param aout a valid audio output
 490  * \param name a valid filter name
 491  * \param add true to add the filter, false to remove it
 492  * \return 0 on success, non-zero on failure.
 493  */
 494 VLC_API int aout_EnableFilter(audio_output_t *aout, const char *name, bool add);
 495
 496 typedef struct
 497 {
 498     /**
 499      * If the remap order differs from the WG4 order, a remap audio filter will
 500      * be inserted to remap channels according to this array.
 501      */
 502     int remap[AOUT_CHANIDX_MAX];
 503     /**
 504      * If true, a filter will be inserted to add a headphones effect (like a
 505      * binauralizer audio filter).
 506      */
 507     bool headphones;
 508 } aout_filters_cfg_t;
 509
 510 #define AOUT_FILTERS_CFG_INIT (aout_filters_cfg_t) \
 511     { .remap = AOUT_CHAN_REMAP_INIT, \
 512       .headphones = false, \
 513     };
 514
 515 typedef struct aout_filters aout_filters_t;
 516
 517 VLC_API aout_filters_t *aout_FiltersNew(vlc_object_t *,
 518                                         const audio_sample_format_t *,
 519                                         const audio_sample_format_t *,
 520                                         const aout_filters_cfg_t *cfg) VLC_USED;
 521 #define aout_FiltersNew(o,inf,outf,remap) \
 522         aout_FiltersNew(VLC_OBJECT(o),inf,outf,remap)
 523 VLC_API void aout_FiltersDelete(vlc_object_t *, aout_filters_t *);
 524 #define aout_FiltersDelete(o,f) \
 525         aout_FiltersDelete(VLC_OBJECT(o),f)
 526 VLC_API bool aout_FiltersAdjustResampling(aout_filters_t *, int);
 527 VLC_API block_t *aout_FiltersPlay(aout_filters_t *, block_t *, float rate);
 528 VLC_API block_t *aout_FiltersDrain(aout_filters_t *);
 529 VLC_API void     aout_FiltersFlush(aout_filters_t *);
 530 VLC_API void     aout_FiltersChangeViewpoint(aout_filters_t *, const vlc_viewpoint_t *vp);
 531
 532 VLC_API vout_thread_t *aout_filter_GetVout(filter_t *, const video_format_t *);
 533
 534 static inline int aout_TimeGet(audio_output_t *aout, vlc_tick_t *delay)
 535 {
 536     return aout->time_get(aout, delay);
 537 }
 538
 539 /** @} */
 540
 541 /**
 542  * @defgroup audio_output__meter Audio meter API
 543  */
 544
 545 /**
 546  * Audio loudness measurement
 547  */
 548 struct vlc_audio_loudness
 549 {
 550     /** Momentary loudness (last 400 ms), in LUFS */
 551     double loudness_momentary;
 552     /** Short term loudness (last 3seconds), in LUFS */
 553     double loudness_shortterm;
 554     /** Integrated loudness (global), in LUFS */
 555     double loudness_integrated;
 556     /** Loudness range, in LU */
 557     double loudness_range;
 558     /** True Peak, in dBTP */
 559     double truepeak;
 560 };
 561
 562 /**
 563  * Audio meter callback
 564  *
 565  * Triggered from vlc_audio_meter_Process() and vlc_audio_meter_Flush().
 566  */
 567 struct vlc_audio_meter_cbs
 568 {
 569     /**
 570      * Called when new loudness measurements are available
 571      *
 572      * @param date absolute date (likely in the future) of this measurement
 573      * @param loudness pointer to the loudness measurement
 574      * @param opaque pointer set by vlc_audio_meter_AddPlugin().
 575      */
 576     void (*on_loudness)(vlc_tick_t date, const struct vlc_audio_loudness *loudness, void *data);
 577 };
 578
 579 /**
 580  * Audio meter plugin opaque structure
 581  *
 582  * This opaque structure is returned by vlc_audio_meter_AddPlugin().
 583  */
 584 typedef struct vlc_audio_meter_plugin vlc_audio_meter_plugin;
 585
 586 /**
 587  * Audio meter plugin owner structure
 588  *
 589  * Used to setup callbacks and private data
 590  *
 591  * Can be registered with vlc_audio_meter_AddPlugin().
 592  */
 593 struct vlc_audio_meter_plugin_owner
 594 {
 595     const struct vlc_audio_meter_cbs *cbs;
 596     void *sys;
 597 };
 598
 599 /**
 600  * Audio meter structure
 601  *
 602  * Initialise with vlc_audio_meter_Init()
 603  *
 604  * @warning variables of this struct should not be used directly
 605  */
 606 struct vlc_audio_meter
 607 {
 608     vlc_mutex_t lock;
 609     vlc_object_t *parent;
 610     const audio_sample_format_t *fmt;
 611
 612     struct vlc_list plugins;
 613 };
 614
 615 /**
 616  * Initialize the audio meter structure
 617  *
 618  * @param meter allocated audio meter structure
 619  * @param parent object that will be used to create audio filters
 620  */
 621 VLC_API void
 622 vlc_audio_meter_Init(struct vlc_audio_meter *meter, vlc_object_t *parent);
 623 #define vlc_audio_meter_Init(a,b) vlc_audio_meter_Init(a, VLC_OBJECT(b))
 624
 625 /**
 626  * Free allocated resource from the audio meter structure
 627  *
 628  * @param meter allocated audio meter structure
 629  */
 630 VLC_API void
 631 vlc_audio_meter_Destroy(struct vlc_audio_meter *meter);
 632
 633 /**
 634  * Set or reset the audio format
 635  *
 636  * This will reload all plugins added with vlc_audio_meter_AddPlugin()
 637  *
 638  * @param meter audio meter structure
 639  * @param fmt NULL to unload all plugins or a valid pointer to an audio format,
 640  * must stay valid during the lifetime of the audio meter (until
 641  * vlc_audio_meter_Reset() or vlc_audio_meter_Destroy() are called)
 642  *
 643  * @return VLC_SUCCESS on success, VLC_EGENERIC if a plugin failed to load
 644  */
 645 VLC_API int
 646 vlc_audio_meter_Reset(struct vlc_audio_meter *meter, const audio_sample_format_t *fmt);
 647
 648 /**
 649  * Add an "audio meter" plugin
 650  *
 651  * The module to be loaded if meter->fmt is valid, otherwise, the module
 652  * will be loaded from a next call to vlc_audio_meter_Reset()
 653  *
 654  * @param meter audio meter structure
 655  * @param chain name of the module, can contain specific module options using
 656  * the following chain convention:"name{option1=a,option2=b}"
 657  * @param cbs pointer to a vlc_audio_meter_events structure, the
 658  * structure must stay valid during the lifetime of the plugin
 659  * @param cbs_data opaque pointer used by the callbacks
 660  * @return a valid audio meter plugin, or NULL in case of error
 661  */
 662 VLC_API vlc_audio_meter_plugin *
 663 vlc_audio_meter_AddPlugin(struct vlc_audio_meter *meter, const char *chain,
 664                           const struct vlc_audio_meter_plugin_owner *owner);
 665
 666 /**
 667  * Remove an "audio meter" plugin
 668  *
 669  * @param meter audio meter structure
 670  * @param plugin plugin returned by vlc_audio_meter_AddPlugin()
 671  */
 672 VLC_API void
 673 vlc_audio_meter_RemovePlugin(struct vlc_audio_meter *meter, vlc_audio_meter_plugin *plugin);
 674
 675 /**
 676  * Process an audio block
 677  *
 678  * vlc_audio_meter_events callbacks can be triggered from this function.
 679  *
 680  * @param meter audio meter structure
 681  * @param block pointer to a block, this block won't be released of modified
 682  * from this function
 683  * @param date absolute date (likely in the future) when this block should be rendered
 684  */
 685 VLC_API void
 686 vlc_audio_meter_Process(struct vlc_audio_meter *meter, block_t *block, vlc_tick_t date);
 687
 688 /**
 689  * Flush all "audio meter" plugins
 690  *
 691  * vlc_audio_meter_events callbacks can be triggered from this function.
 692  *
 693  * @param meter audio meter structure
 694  */
 695 VLC_API void
 696 vlc_audio_meter_Flush(struct vlc_audio_meter *meter);
 697
 698 /** @} */
 699
 700 #endif /* VLC_AOUT_H */