git.sesse.net Git - vlc/blob - modules/codec/mpeg_audio.c

   1 /*****************************************************************************
   2  * mpeg_audio.c: parse MPEG audio sync info and packetize the stream
   3  *****************************************************************************
   4  * Copyright (C) 2001-2003 VideoLAN
   5  * $Id$
   6  *
   7  * Authors: Laurent Aimar <fenrir@via.ecp.fr>
   8  *          Eric Petit <titer@videolan.org>
   9  *          Christophe Massiot <massiot@via.ecp.fr>
  10  *          Gildas Bazin <gbazin@netcourrier.com>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  25  *****************************************************************************/
  26
  27 /*****************************************************************************
  28  * Preamble
  29  *****************************************************************************/
  30 #include <vlc/vlc.h>
  31 #include <vlc/input.h>          /* for input infos */
  32 #include <vlc/decoder.h>
  33 #include <vlc/aout.h>
  34
  35 #include "vlc_block_helper.h"
  36
  37 /*****************************************************************************
  38  * decoder_sys_t : decoder descriptor
  39  *****************************************************************************/
  40 struct decoder_sys_t
  41 {
  42     /* Module mode */
  43     vlc_bool_t b_packetizer;
  44
  45     /*
  46      * Input properties
  47      */
  48     int        i_state;
  49
  50     block_bytestream_t bytestream;
  51
  52     /*
  53      * Common properties
  54      */
  55     audio_date_t          end_date;
  56     unsigned int          i_current_layer;
  57
  58     mtime_t i_pts;
  59
  60     int i_frame_size, i_free_frame_size;
  61     unsigned int i_channels_conf, i_channels;
  62     unsigned int i_rate, i_max_frame_size, i_frame_length;
  63     unsigned int i_layer, i_bit_rate;
  64 };
  65
  66 enum {
  67
  68     STATE_NOSYNC,
  69     STATE_SYNC,
  70     STATE_HEADER,
  71     STATE_NEXT_SYNC,
  72     STATE_GET_DATA,
  73     STATE_SEND_DATA
  74 };
  75
  76 /* This isn't the place to put mad-specific stuff. However, it makes the
  77  * mad plug-in's life much easier if we put 8 extra bytes at the end of the
  78  * buffer, because that way it doesn't have to copy the aout_buffer_t to a
  79  * bigger buffer. This has no implication on other plug-ins, and we only
  80  * lose 8 bytes per frame. --Meuuh */
  81 #define MAD_BUFFER_GUARD 8
  82 #define MPGA_HEADER_SIZE 4
  83
  84 /****************************************************************************
  85  * Local prototypes
  86  ****************************************************************************/
  87 static int  OpenDecoder   ( vlc_object_t * );
  88 static int  OpenPacketizer( vlc_object_t * );
  89 static void CloseDecoder  ( vlc_object_t * );
  90 static void *DecodeBlock  ( decoder_t *, block_t ** );
  91
  92 static uint8_t       *GetOutBuffer ( decoder_t *, void ** );
  93 static aout_buffer_t *GetAoutBuffer( decoder_t * );
  94 static block_t       *GetSoutBuffer( decoder_t * );
  95
  96 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
  97                      unsigned int * pi_channels_conf,
  98                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
  99                      unsigned int * pi_frame_length,
 100                      unsigned int * pi_max_frame_size,
 101                      unsigned int * pi_layer );
 102
 103 /*****************************************************************************
 104  * Module descriptor
 105  *****************************************************************************/
 106 vlc_module_begin();
 107     set_description( _("MPEG audio layer I/II/III parser") );
 108 #if defined(SYS_DARWIN)
 109     set_capability( "decoder", 5 );
 110 #else
 111     set_capability( "decoder", 100 );
 112 #endif
 113     set_callbacks( OpenDecoder, CloseDecoder );
 114
 115     add_submodule();
 116     set_description( _("MPEG audio layer I/II/III packetizer") );
 117     set_capability( "packetizer", 10 );
 118     set_callbacks( OpenPacketizer, CloseDecoder );
 119 vlc_module_end();
 120
 121 /*****************************************************************************
 122  * OpenDecoder: probe the decoder and return score
 123  *****************************************************************************/
 124 static int OpenDecoder( vlc_object_t *p_this )
 125 {
 126     decoder_t *p_dec = (decoder_t*)p_this;
 127     decoder_sys_t *p_sys;
 128
 129     if( p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','a') )
 130     {
 131         return VLC_EGENERIC;
 132     }
 133
 134     /* Allocate the memory needed to store the decoder's structure */
 135     if( ( p_dec->p_sys = p_sys =
 136           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 137     {
 138         msg_Err( p_dec, "out of memory" );
 139         return VLC_EGENERIC;
 140     }
 141
 142     /* Misc init */
 143     p_sys->b_packetizer = VLC_FALSE;
 144     p_sys->i_state = STATE_NOSYNC;
 145     aout_DateSet( &p_sys->end_date, 0 );
 146     p_sys->bytestream = block_BytestreamInit( p_dec );
 147
 148     /* Set output properties */
 149     p_dec->fmt_out.i_cat = AUDIO_ES;
 150     p_dec->fmt_out.i_codec = VLC_FOURCC('m','p','g','a');
 151
 152     /* Set callback */
 153     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 154         DecodeBlock;
 155     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 156         DecodeBlock;
 157
 158     /* Start with the minimum size for a free bitrate frame */
 159     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 160
 161     return VLC_SUCCESS;
 162 }
 163
 164 static int OpenPacketizer( vlc_object_t *p_this )
 165 {
 166     decoder_t *p_dec = (decoder_t*)p_this;
 167
 168     int i_ret = OpenDecoder( p_this );
 169
 170     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = VLC_TRUE;
 171
 172     return i_ret;
 173 }
 174
 175 /****************************************************************************
 176  * DecodeBlock: the whole thing
 177  ****************************************************************************
 178  * This function is called just after the thread is launched.
 179  ****************************************************************************/
 180 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 181 {
 182     decoder_sys_t *p_sys = p_dec->p_sys;
 183     uint8_t p_header[MAD_BUFFER_GUARD];
 184     uint32_t i_header;
 185     uint8_t *p_buf;
 186     void *p_out_buffer;
 187
 188     if( !pp_block || !*pp_block ) return NULL;
 189
 190     if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 191     {
 192         /* We've just started the stream, wait for the first PTS. */
 193         block_Release( *pp_block );
 194         return NULL;
 195     }
 196
 197     if( (*pp_block)->i_flags&BLOCK_FLAG_DISCONTINUITY )
 198     {
 199         p_sys->i_state = STATE_NOSYNC;
 200     }
 201
 202     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 203
 204     while( 1 )
 205     {
 206         switch( p_sys->i_state )
 207         {
 208
 209         case STATE_NOSYNC:
 210             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 211                    == VLC_SUCCESS )
 212             {
 213                 /* Look for sync word - should be 0xffe */
 214                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 215                 {
 216                     p_sys->i_state = STATE_SYNC;
 217                     break;
 218                 }
 219                 block_SkipByte( &p_sys->bytestream );
 220             }
 221             if( p_sys->i_state != STATE_SYNC )
 222             {
 223                 block_BytestreamFlush( &p_sys->bytestream );
 224
 225                 /* Need more data */
 226                 return NULL;
 227             }
 228
 229         case STATE_SYNC:
 230             /* New frame, set the Presentation Time Stamp */
 231             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 232             if( p_sys->i_pts != 0 &&
 233                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 234             {
 235                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 236             }
 237             p_sys->i_state = STATE_HEADER;
 238
 239         case STATE_HEADER:
 240             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 241             if( block_PeekBytes( &p_sys->bytestream, p_header,
 242                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 243             {
 244                 /* Need more data */
 245                 return NULL;
 246             }
 247
 248             /* Build frame header */
 249             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 250                        |p_header[3];
 251
 252             /* Check if frame is valid and get frame info */
 253             p_sys->i_frame_size = SyncInfo( i_header,
 254                                             &p_sys->i_channels,
 255                                             &p_sys->i_channels_conf,
 256                                             &p_sys->i_rate,
 257                                             &p_sys->i_bit_rate,
 258                                             &p_sys->i_frame_length,
 259                                             &p_sys->i_max_frame_size,
 260                                             &p_sys->i_layer );
 261
 262             if( p_sys->i_frame_size == -1 )
 263             {
 264                 msg_Dbg( p_dec, "emulated startcode" );
 265                 block_SkipByte( &p_sys->bytestream );
 266                 p_sys->i_state = STATE_NOSYNC;
 267                 break;
 268             }
 269
 270             if( p_sys->i_bit_rate == 0 )
 271             {
 272                 /* Free birate, but 99% emulated startcode :( */
 273                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 274                 {
 275                     msg_Dbg( p_dec, "free bitrate mode");
 276                 }
 277                 p_sys->i_frame_size = p_sys->i_free_frame_size;
 278             }
 279
 280             p_sys->i_state = STATE_NEXT_SYNC;
 281
 282         case STATE_NEXT_SYNC:
 283             /* TODO: If p_block == NULL, flush the buffer without checking the
 284              * next sync word */
 285
 286             /* Check if next expected frame contains the sync word */
 287             if( block_PeekOffsetBytes( &p_sys->bytestream,
 288                                        p_sys->i_frame_size, p_header,
 289                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 290             {
 291                 /* Need more data */
 292                 return NULL;
 293             }
 294
 295             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 296             {
 297                 /* Startcode is fine, let's try the header as an extra check */
 298                 int i_next_frame_size;
 299                 unsigned int i_next_channels, i_next_channels_conf;
 300                 unsigned int i_next_rate, i_next_bit_rate;
 301                 unsigned int i_next_frame_length, i_next_max_frame_size;
 302                 unsigned int i_next_layer;
 303
 304                 /* Build frame header */
 305                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 306                            |p_header[3];
 307
 308                 i_next_frame_size = SyncInfo( i_header,
 309                                               &i_next_channels,
 310                                               &i_next_channels_conf,
 311                                               &i_next_rate,
 312                                               &i_next_bit_rate,
 313                                               &i_next_frame_length,
 314                                               &i_next_max_frame_size,
 315                                               &i_next_layer );
 316
 317                 /* Free bitrate only */
 318                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 319                 {
 320                     if( (unsigned int)p_sys->i_frame_size >
 321                         p_sys->i_max_frame_size )
 322                     {
 323                         msg_Dbg( p_dec, "frame too big %d > %d "
 324                                  "(emulated startcode ?)", p_sys->i_frame_size,
 325                                  p_sys->i_max_frame_size );
 326                         block_SkipByte( &p_sys->bytestream );
 327                         p_sys->i_state = STATE_NOSYNC;
 328                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 329                         break;
 330                     }
 331
 332                     p_sys->i_frame_size++;
 333                     break;
 334                 }
 335
 336                 if( i_next_frame_size == -1 )
 337                 {
 338                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 339                     block_SkipByte( &p_sys->bytestream );
 340                     p_sys->i_state = STATE_NOSYNC;
 341                     break;
 342                 }
 343
 344                 /* Check info is in sync with previous one */
 345                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 346                     i_next_rate != p_sys->i_rate ||
 347                     i_next_layer != p_sys->i_layer ||
 348                     i_next_frame_length != p_sys->i_frame_length )
 349                 {
 350                     /* Free bitrate only */
 351                     if( p_sys->i_bit_rate == 0 )
 352                     {
 353                         p_sys->i_frame_size++;
 354                         break;
 355                     }
 356
 357                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 358                              "(emulated startcode ?)" );
 359                     block_SkipByte( &p_sys->bytestream );
 360                     p_sys->i_state = STATE_NOSYNC;
 361                     break;
 362                 }
 363
 364                 /* Free bitrate only */
 365                 if( p_sys->i_bit_rate == 0 )
 366                 {
 367                     if( i_next_bit_rate != 0 )
 368                     {
 369                         p_sys->i_frame_size++;
 370                         break;
 371                     }
 372                 }
 373
 374             }
 375             else
 376             {
 377                 /* Free bitrate only */
 378                 if( p_sys->i_bit_rate == 0 )
 379                 {
 380                     if( (unsigned int)p_sys->i_frame_size >
 381                         p_sys->i_max_frame_size )
 382                     {
 383                         msg_Dbg( p_dec, "frame too big %d > %d "
 384                                  "(emulated startcode ?)", p_sys->i_frame_size,
 385                                  p_sys->i_max_frame_size );
 386                         block_SkipByte( &p_sys->bytestream );
 387                         p_sys->i_state = STATE_NOSYNC;
 388                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 389                         break;
 390                     }
 391
 392                     p_sys->i_frame_size++;
 393                     break;
 394                 }
 395
 396                 msg_Dbg( p_dec, "emulated startcode "
 397                          "(no startcode on following frame)" );
 398                 p_sys->i_state = STATE_NOSYNC;
 399                 block_SkipByte( &p_sys->bytestream );
 400                 break;
 401             }
 402
 403             p_sys->i_state = STATE_SEND_DATA;
 404             break;
 405
 406         case STATE_GET_DATA:
 407             /* Make sure we have enough data.
 408              * (Not useful if we went through NEXT_SYNC) */
 409             if( block_WaitBytes( &p_sys->bytestream,
 410                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 411             {
 412                 /* Need more data */
 413                 return NULL;
 414             }
 415             p_sys->i_state = STATE_SEND_DATA;
 416
 417         case STATE_SEND_DATA:
 418             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 419             {
 420                 //p_dec->b_error = VLC_TRUE;
 421                 return NULL;
 422             }
 423
 424             /* Free bitrate only */
 425             if( p_sys->i_bit_rate == 0 )
 426             {
 427                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 428             }
 429
 430             /* Copy the whole frame into the buffer. When we reach this point
 431              * we already know we have enough data available. */
 432             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 433
 434             /* Get beginning of next frame for libmad */
 435             if( !p_sys->b_packetizer )
 436             {
 437                 memcpy( p_buf + p_sys->i_frame_size,
 438                         p_header, MAD_BUFFER_GUARD );
 439             }
 440
 441             p_sys->i_state = STATE_NOSYNC;
 442
 443             /* Make sure we don't reuse the same pts twice */
 444             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 445                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 446
 447             /* So p_block doesn't get re-added several times */
 448             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 449
 450             return p_out_buffer;
 451         }
 452     }
 453
 454     return NULL;
 455 }
 456
 457 /*****************************************************************************
 458  * GetOutBuffer:
 459  *****************************************************************************/
 460 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 461 {
 462     decoder_sys_t *p_sys = p_dec->p_sys;
 463     uint8_t *p_buf;
 464
 465     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 466     {
 467 #define TITLE_MAX 30
 468         input_info_category_t *p_cat;
 469         char psz_streamid[TITLE_MAX];
 470         int i_es_id = p_dec->fmt_out.i_id;
 471         input_thread_t * p_input = vlc_object_find( p_dec, VLC_OBJECT_INPUT, FIND_PARENT );
 472
 473         if( p_input )
 474         {
 475             snprintf(psz_streamid, TITLE_MAX, "%s%04x", _("Stream "), i_es_id);
 476             p_cat = input_InfoCategory( p_input, psz_streamid );
 477
 478 #if 1
 479             /* We should be finding this stream, but we aren't. */
 480             input_AddInfo( p_cat, _("Type"), "%s", _("audio") );
 481             input_AddInfo( p_cat, _("Description"), "%s", _("MPEG audio") );
 482 #endif
 483
 484             input_AddInfo( p_cat, _("Sample Rate"), "%d", p_sys->i_rate );
 485             input_AddInfo( p_cat, _("Bit Rate"), "%d", p_sys->i_bit_rate );
 486             input_AddInfo( p_cat, _("Channel(s)"), "%d", p_sys->i_channels );
 487
 488             msg_Info( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 489                       p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 490
 491             aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 492             aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 493
 494             vlc_object_release( p_input );
 495         }
 496     }
 497
 498     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 499     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 500     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 501     p_dec->fmt_out.audio.i_bytes_per_frame =
 502         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 503
 504     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 505     p_dec->fmt_out.audio.i_physical_channels =
 506         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 507
 508     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate;
 509
 510     if( p_sys->b_packetizer )
 511     {
 512         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 513         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 514         *pp_out_buffer = p_sout_buffer;
 515     }
 516     else
 517     {
 518         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 519         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 520         *pp_out_buffer = p_aout_buffer;
 521     }
 522
 523     return p_buf;
 524 }
 525
 526 /*****************************************************************************
 527  * GetAoutBuffer:
 528  *****************************************************************************/
 529 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 530 {
 531     decoder_sys_t *p_sys = p_dec->p_sys;
 532     aout_buffer_t *p_buf;
 533
 534     p_buf = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_frame_length );
 535     if( p_buf == NULL ) return NULL;
 536
 537     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 538     p_buf->end_date =
 539         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 540
 541     /* Hack for libmad filter */
 542     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 543
 544     return p_buf;
 545 }
 546
 547 /*****************************************************************************
 548  * GetSoutBuffer:
 549  *****************************************************************************/
 550 static block_t *GetSoutBuffer( decoder_t *p_dec )
 551 {
 552     decoder_sys_t *p_sys = p_dec->p_sys;
 553     block_t *p_block;
 554
 555     p_block = block_New( p_dec, p_sys->i_frame_size );
 556     if( p_block == NULL ) return NULL;
 557
 558     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 559
 560     p_block->i_length =
 561         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) -
 562             p_block->i_pts;
 563
 564     return p_block;
 565 }
 566
 567 /*****************************************************************************
 568  * CloseDecoder: clean up the decoder
 569  *****************************************************************************/
 570 static void CloseDecoder( vlc_object_t *p_this )
 571 {
 572     decoder_t *p_dec = (decoder_t *)p_this;
 573     decoder_sys_t *p_sys = p_dec->p_sys;
 574
 575     block_BytestreamRelease( &p_sys->bytestream );
 576
 577     free( p_sys );
 578 }
 579
 580 /*****************************************************************************
 581  * SyncInfo: parse MPEG audio sync info
 582  *****************************************************************************/
 583 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 584                      unsigned int * pi_channels_conf,
 585                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 586                      unsigned int * pi_frame_length,
 587                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 588 {
 589     static const int ppi_bitrate[2][3][16] =
 590     {
 591         {
 592             /* v1 l1 */
 593             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 594               416, 448, 0},
 595             /* v1 l2 */
 596             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 597               320, 384, 0},
 598             /* v1 l3 */
 599             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 600               256, 320, 0}
 601         },
 602
 603         {
 604             /* v2 l1 */
 605             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 606               224, 256, 0},
 607             /* v2 l2 */
 608             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 609               144, 160, 0},
 610             /* v2 l3 */
 611             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 612               144, 160, 0}
 613         }
 614     };
 615
 616     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 617     {
 618         { 44100, 48000, 32000, 0 },
 619         { 22050, 24000, 16000, 0 }
 620     };
 621
 622     int i_version, i_mode, i_emphasis;
 623     vlc_bool_t b_padding, b_mpeg_2_5, b_crc;
 624     int i_frame_size = 0;
 625     int i_bitrate_index, i_samplerate_index;
 626     int i_max_bit_rate;
 627
 628     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 629     i_version   = 1 - ((i_header & 0x80000) >> 19);
 630     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 631     b_crc = !((i_header >> 16) & 0x01);
 632     i_bitrate_index = (i_header & 0xf000) >> 12;
 633     i_samplerate_index = (i_header & 0xc00) >> 10;
 634     b_padding   = (i_header & 0x200) >> 9;
 635     /* Extension */
 636     i_mode      = (i_header & 0xc0) >> 6;
 637     /* Modeext, copyright & original */
 638     i_emphasis  = i_header & 0x3;
 639
 640     if( *pi_layer != 4 &&
 641         i_bitrate_index < 0x0f &&
 642         i_samplerate_index != 0x03 &&
 643         i_emphasis != 0x02 )
 644     {
 645         switch ( i_mode )
 646         {
 647         case 0: /* stereo */
 648         case 1: /* joint stereo */
 649             *pi_channels = 2;
 650             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 651             break;
 652         case 2: /* dual-mono */
 653             *pi_channels = 2;
 654             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 655                                 | AOUT_CHAN_DUALMONO;
 656             break;
 657         case 3: /* mono */
 658             *pi_channels = 1;
 659             *pi_channels_conf = AOUT_CHAN_CENTER;
 660             break;
 661         }
 662         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 663         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 664         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 665
 666         if ( b_mpeg_2_5 )
 667         {
 668             *pi_sample_rate >>= 1;
 669         }
 670
 671         switch( *pi_layer )
 672         {
 673         case 1:
 674             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 675                            b_padding ) * 4;
 676             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 677                                  *pi_sample_rate + 1 ) * 4;
 678             *pi_frame_length = 384;
 679             break;
 680
 681         case 2:
 682             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 683             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 684             *pi_frame_length = 1152;
 685             break;
 686
 687         case 3:
 688             i_frame_size = ( i_version ? 72000 : 144000 ) *
 689                            *pi_bit_rate / *pi_sample_rate + b_padding;
 690             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 691                                  i_max_bit_rate / *pi_sample_rate + 1;
 692             *pi_frame_length = i_version ? 576 : 1152;
 693             break;
 694
 695         default:
 696             break;
 697         }
 698     }
 699     else
 700     {
 701         return -1;
 702     }
 703
 704     return i_frame_size;
 705 }