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 the VideoLAN team
   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@videolan.org>
  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., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  25  *****************************************************************************/
  26
  27 /*****************************************************************************
  28  * Preamble
  29  *****************************************************************************/
  30 #include <vlc/vlc.h>
  31 #include <vlc_codec.h>
  32 #include <vlc_aout.h>
  33
  34 #include <vlc_block_helper.h>
  35
  36 /*****************************************************************************
  37  * decoder_sys_t : decoder descriptor
  38  *****************************************************************************/
  39 struct decoder_sys_t
  40 {
  41     /* Module mode */
  42     vlc_bool_t b_packetizer;
  43
  44     /*
  45      * Input properties
  46      */
  47     int        i_state;
  48
  49     block_bytestream_t bytestream;
  50
  51     /*
  52      * Common properties
  53      */
  54     audio_date_t          end_date;
  55     unsigned int          i_current_layer;
  56
  57     mtime_t i_pts;
  58
  59     int i_frame_size, i_free_frame_size;
  60     unsigned int i_channels_conf, i_channels;
  61     unsigned int i_rate, i_max_frame_size, i_frame_length;
  62     unsigned int i_layer, i_bit_rate;
  63
  64     vlc_bool_t   b_discontinuity;
  65 };
  66
  67 enum {
  68
  69     STATE_NOSYNC,
  70     STATE_SYNC,
  71     STATE_HEADER,
  72     STATE_NEXT_SYNC,
  73     STATE_GET_DATA,
  74     STATE_SEND_DATA
  75 };
  76
  77 /* This isn't the place to put mad-specific stuff. However, it makes the
  78  * mad plug-in's life much easier if we put 8 extra bytes at the end of the
  79  * buffer, because that way it doesn't have to copy the aout_buffer_t to a
  80  * bigger buffer. This has no implication on other plug-ins, and we only
  81  * lose 8 bytes per frame. --Meuuh */
  82 #define MAD_BUFFER_GUARD 8
  83 #define MPGA_HEADER_SIZE 4
  84
  85 /****************************************************************************
  86  * Local prototypes
  87  ****************************************************************************/
  88 static int  OpenDecoder   ( vlc_object_t * );
  89 static int  OpenPacketizer( vlc_object_t * );
  90 static void CloseDecoder  ( vlc_object_t * );
  91 static void *DecodeBlock  ( decoder_t *, block_t ** );
  92
  93 static uint8_t       *GetOutBuffer ( decoder_t *, void ** );
  94 static aout_buffer_t *GetAoutBuffer( decoder_t * );
  95 static block_t       *GetSoutBuffer( decoder_t * );
  96
  97 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
  98                      unsigned int * pi_channels_conf,
  99                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 100                      unsigned int * pi_frame_length,
 101                      unsigned int * pi_max_frame_size,
 102                      unsigned int * pi_layer );
 103
 104 /*****************************************************************************
 105  * Module descriptor
 106  *****************************************************************************/
 107 vlc_module_begin();
 108     set_description( _("MPEG audio layer I/II/III decoder") );
 109     set_category( CAT_INPUT );
 110     set_subcategory( SUBCAT_INPUT_ACODEC );
 111 #if defined(UNDER_CE)
 112    set_capability( "decoder", 5 );
 113 #else
 114     set_capability( "decoder", 100 );
 115 #endif
 116     set_callbacks( OpenDecoder, CloseDecoder );
 117
 118     add_submodule();
 119     set_description( _("MPEG audio layer I/II/III packetizer") );
 120     set_capability( "packetizer", 10 );
 121     set_callbacks( OpenPacketizer, CloseDecoder );
 122 vlc_module_end();
 123
 124 /*****************************************************************************
 125  * OpenDecoder: probe the decoder and return score
 126  *****************************************************************************/
 127 static int OpenDecoder( vlc_object_t *p_this )
 128 {
 129     decoder_t *p_dec = (decoder_t*)p_this;
 130     decoder_sys_t *p_sys;
 131
 132     if( p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','a') )
 133     {
 134         return VLC_EGENERIC;
 135     }
 136
 137     /* HACK: Don't use this codec if we don't have an mpga audio filter */
 138     if( p_dec->i_object_type == VLC_OBJECT_DECODER &&
 139         !config_FindModule( p_this, "mpgatofixed32" ) )
 140     {
 141         return VLC_EGENERIC;
 142     }
 143
 144     /* Allocate the memory needed to store the decoder's structure */
 145     if( ( p_dec->p_sys = p_sys =
 146           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 147     {
 148         msg_Err( p_dec, "out of memory" );
 149         return VLC_EGENERIC;
 150     }
 151
 152     /* Misc init */
 153     p_sys->b_packetizer = VLC_FALSE;
 154     p_sys->i_state = STATE_NOSYNC;
 155     aout_DateSet( &p_sys->end_date, 0 );
 156     p_sys->bytestream = block_BytestreamInit( p_dec );
 157     p_sys->b_discontinuity = VLC_FALSE;
 158
 159     /* Set output properties */
 160     p_dec->fmt_out.i_cat = AUDIO_ES;
 161     p_dec->fmt_out.i_codec = VLC_FOURCC('m','p','g','a');
 162     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 163
 164     /* Set callback */
 165     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 166         DecodeBlock;
 167     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 168         DecodeBlock;
 169
 170     /* Start with the minimum size for a free bitrate frame */
 171     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 172
 173     return VLC_SUCCESS;
 174 }
 175
 176 static int OpenPacketizer( vlc_object_t *p_this )
 177 {
 178     decoder_t *p_dec = (decoder_t*)p_this;
 179
 180     int i_ret = OpenDecoder( p_this );
 181
 182     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = VLC_TRUE;
 183
 184     return i_ret;
 185 }
 186
 187 /****************************************************************************
 188  * DecodeBlock: the whole thing
 189  ****************************************************************************
 190  * This function is called just after the thread is launched.
 191  ****************************************************************************/
 192 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 193 {
 194     decoder_sys_t *p_sys = p_dec->p_sys;
 195     uint8_t p_header[MAD_BUFFER_GUARD];
 196     uint32_t i_header;
 197     uint8_t *p_buf;
 198     void *p_out_buffer;
 199
 200     if( !pp_block || !*pp_block ) return NULL;
 201
 202     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 203     {
 204         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 205         {
 206             p_sys->i_state = STATE_NOSYNC;
 207             block_BytestreamFlush( &p_sys->bytestream );
 208         }
 209 //        aout_DateSet( &p_sys->end_date, 0 );
 210         block_Release( *pp_block );
 211         p_sys->b_discontinuity = VLC_TRUE;
 212         return NULL;
 213     }
 214
 215     if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 216     {
 217         /* We've just started the stream, wait for the first PTS. */
 218         msg_Dbg( p_dec, "waiting for PTS" );
 219         block_Release( *pp_block );
 220         return NULL;
 221     }
 222
 223     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 224
 225     while( 1 )
 226     {
 227         switch( p_sys->i_state )
 228         {
 229
 230         case STATE_NOSYNC:
 231             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 232                    == VLC_SUCCESS )
 233             {
 234                 /* Look for sync word - should be 0xffe */
 235                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 236                 {
 237                     p_sys->i_state = STATE_SYNC;
 238                     break;
 239                 }
 240                 block_SkipByte( &p_sys->bytestream );
 241             }
 242             if( p_sys->i_state != STATE_SYNC )
 243             {
 244                 block_BytestreamFlush( &p_sys->bytestream );
 245
 246                 /* Need more data */
 247                 return NULL;
 248             }
 249
 250         case STATE_SYNC:
 251             /* New frame, set the Presentation Time Stamp */
 252             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 253             if( p_sys->i_pts != 0 &&
 254                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 255             {
 256                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 257             }
 258             p_sys->i_state = STATE_HEADER;
 259
 260         case STATE_HEADER:
 261             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 262             if( block_PeekBytes( &p_sys->bytestream, p_header,
 263                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 264             {
 265                 /* Need more data */
 266                 return NULL;
 267             }
 268
 269             /* Build frame header */
 270             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 271                        |p_header[3];
 272
 273             /* Check if frame is valid and get frame info */
 274             p_sys->i_frame_size = SyncInfo( i_header,
 275                                             &p_sys->i_channels,
 276                                             &p_sys->i_channels_conf,
 277                                             &p_sys->i_rate,
 278                                             &p_sys->i_bit_rate,
 279                                             &p_sys->i_frame_length,
 280                                             &p_sys->i_max_frame_size,
 281                                             &p_sys->i_layer );
 282
 283             if( p_sys->i_frame_size == -1 )
 284             {
 285                 msg_Dbg( p_dec, "emulated startcode" );
 286                 block_SkipByte( &p_sys->bytestream );
 287                 p_sys->i_state = STATE_NOSYNC;
 288                 p_sys->b_discontinuity = VLC_TRUE;
 289                 break;
 290             }
 291
 292             if( p_sys->i_bit_rate == 0 )
 293             {
 294                 /* Free birate, but 99% emulated startcode :( */
 295                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 296                 {
 297                     msg_Dbg( p_dec, "free bitrate mode");
 298                 }
 299                 p_sys->i_frame_size = p_sys->i_free_frame_size;
 300             }
 301
 302             p_sys->i_state = STATE_NEXT_SYNC;
 303
 304         case STATE_NEXT_SYNC:
 305             /* TODO: If p_block == NULL, flush the buffer without checking the
 306              * next sync word */
 307
 308             /* Check if next expected frame contains the sync word */
 309             if( block_PeekOffsetBytes( &p_sys->bytestream,
 310                                        p_sys->i_frame_size, p_header,
 311                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 312             {
 313                 /* Need more data */
 314                 return NULL;
 315             }
 316
 317             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 318             {
 319                 /* Startcode is fine, let's try the header as an extra check */
 320                 int i_next_frame_size;
 321                 unsigned int i_next_channels, i_next_channels_conf;
 322                 unsigned int i_next_rate, i_next_bit_rate;
 323                 unsigned int i_next_frame_length, i_next_max_frame_size;
 324                 unsigned int i_next_layer;
 325
 326                 /* Build frame header */
 327                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 328                            |p_header[3];
 329
 330                 i_next_frame_size = SyncInfo( i_header,
 331                                               &i_next_channels,
 332                                               &i_next_channels_conf,
 333                                               &i_next_rate,
 334                                               &i_next_bit_rate,
 335                                               &i_next_frame_length,
 336                                               &i_next_max_frame_size,
 337                                               &i_next_layer );
 338
 339                 /* Free bitrate only */
 340                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 341                 {
 342                     if( (unsigned int)p_sys->i_frame_size >
 343                         p_sys->i_max_frame_size )
 344                     {
 345                         msg_Dbg( p_dec, "frame too big %d > %d "
 346                                  "(emulated startcode ?)", p_sys->i_frame_size,
 347                                  p_sys->i_max_frame_size );
 348                         block_SkipByte( &p_sys->bytestream );
 349                         p_sys->i_state = STATE_NOSYNC;
 350                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 351                         break;
 352                     }
 353
 354                     p_sys->i_frame_size++;
 355                     break;
 356                 }
 357
 358                 if( i_next_frame_size == -1 )
 359                 {
 360                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 361                     block_SkipByte( &p_sys->bytestream );
 362                     p_sys->i_state = STATE_NOSYNC;
 363                     p_sys->b_discontinuity = VLC_TRUE;
 364                     break;
 365                 }
 366
 367                 /* Check info is in sync with previous one */
 368                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 369                     i_next_rate != p_sys->i_rate ||
 370                     i_next_layer != p_sys->i_layer ||
 371                     i_next_frame_length != p_sys->i_frame_length )
 372                 {
 373                     /* Free bitrate only */
 374                     if( p_sys->i_bit_rate == 0 )
 375                     {
 376                         p_sys->i_frame_size++;
 377                         break;
 378                     }
 379
 380                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 381                              "(emulated startcode ?)" );
 382                     block_SkipByte( &p_sys->bytestream );
 383                     p_sys->i_state = STATE_NOSYNC;
 384                     break;
 385                 }
 386
 387                 /* Free bitrate only */
 388                 if( p_sys->i_bit_rate == 0 )
 389                 {
 390                     if( i_next_bit_rate != 0 )
 391                     {
 392                         p_sys->i_frame_size++;
 393                         break;
 394                     }
 395                 }
 396
 397             }
 398             else
 399             {
 400                 /* Free bitrate only */
 401                 if( p_sys->i_bit_rate == 0 )
 402                 {
 403                     if( (unsigned int)p_sys->i_frame_size >
 404                         p_sys->i_max_frame_size )
 405                     {
 406                         msg_Dbg( p_dec, "frame too big %d > %d "
 407                                  "(emulated startcode ?)", p_sys->i_frame_size,
 408                                  p_sys->i_max_frame_size );
 409                         block_SkipByte( &p_sys->bytestream );
 410                         p_sys->i_state = STATE_NOSYNC;
 411                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 412                         break;
 413                     }
 414
 415                     p_sys->i_frame_size++;
 416                     break;
 417                 }
 418
 419                 msg_Dbg( p_dec, "emulated startcode "
 420                          "(no startcode on following frame)" );
 421                 p_sys->i_state = STATE_NOSYNC;
 422                 block_SkipByte( &p_sys->bytestream );
 423                 break;
 424             }
 425
 426             p_sys->i_state = STATE_SEND_DATA;
 427             break;
 428
 429         case STATE_GET_DATA:
 430             /* Make sure we have enough data.
 431              * (Not useful if we went through NEXT_SYNC) */
 432             if( block_WaitBytes( &p_sys->bytestream,
 433                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 434             {
 435                 /* Need more data */
 436                 return NULL;
 437             }
 438             p_sys->i_state = STATE_SEND_DATA;
 439
 440         case STATE_SEND_DATA:
 441             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 442             {
 443                 //p_dec->b_error = VLC_TRUE;
 444                 return NULL;
 445             }
 446
 447             /* Free bitrate only */
 448             if( p_sys->i_bit_rate == 0 )
 449             {
 450                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 451             }
 452
 453             /* Copy the whole frame into the buffer. When we reach this point
 454              * we already know we have enough data available. */
 455             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 456
 457             /* Get beginning of next frame for libmad */
 458             if( !p_sys->b_packetizer )
 459             {
 460                 memcpy( p_buf + p_sys->i_frame_size,
 461                         p_header, MAD_BUFFER_GUARD );
 462             }
 463
 464             p_sys->i_state = STATE_NOSYNC;
 465
 466             /* Make sure we don't reuse the same pts twice */
 467             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 468                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 469
 470             /* So p_block doesn't get re-added several times */
 471             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 472
 473             return p_out_buffer;
 474         }
 475     }
 476
 477     return NULL;
 478 }
 479
 480 /*****************************************************************************
 481  * GetOutBuffer:
 482  *****************************************************************************/
 483 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 484 {
 485     decoder_sys_t *p_sys = p_dec->p_sys;
 486     uint8_t *p_buf;
 487
 488     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 489     {
 490         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 491                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 492
 493         aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 494         aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 495     }
 496
 497     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 498     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 499     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 500     p_dec->fmt_out.audio.i_bytes_per_frame =
 501         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 502
 503     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 504     p_dec->fmt_out.audio.i_physical_channels =
 505         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 506
 507     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 508
 509     if( p_sys->b_packetizer )
 510     {
 511         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 512         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 513         *pp_out_buffer = p_sout_buffer;
 514     }
 515     else
 516     {
 517         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 518         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 519         *pp_out_buffer = p_aout_buffer;
 520     }
 521
 522     return p_buf;
 523 }
 524
 525 /*****************************************************************************
 526  * GetAoutBuffer:
 527  *****************************************************************************/
 528 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 529 {
 530     decoder_sys_t *p_sys = p_dec->p_sys;
 531     aout_buffer_t *p_buf;
 532
 533     p_buf = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_frame_length );
 534     if( p_buf == NULL ) return NULL;
 535
 536     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 537     p_buf->end_date =
 538         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 539     p_buf->b_discontinuity = p_sys->b_discontinuity;
 540     p_sys->b_discontinuity = VLC_FALSE;
 541
 542     /* Hack for libmad filter */
 543     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 544
 545     return p_buf;
 546 }
 547
 548 /*****************************************************************************
 549  * GetSoutBuffer:
 550  *****************************************************************************/
 551 static block_t *GetSoutBuffer( decoder_t *p_dec )
 552 {
 553     decoder_sys_t *p_sys = p_dec->p_sys;
 554     block_t *p_block;
 555
 556     p_block = block_New( p_dec, p_sys->i_frame_size );
 557     if( p_block == NULL ) return NULL;
 558
 559     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 560
 561     p_block->i_length =
 562         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) -
 563             p_block->i_pts;
 564
 565     return p_block;
 566 }
 567
 568 /*****************************************************************************
 569  * CloseDecoder: clean up the decoder
 570  *****************************************************************************/
 571 static void CloseDecoder( vlc_object_t *p_this )
 572 {
 573     decoder_t *p_dec = (decoder_t *)p_this;
 574     decoder_sys_t *p_sys = p_dec->p_sys;
 575
 576     block_BytestreamRelease( &p_sys->bytestream );
 577
 578     free( p_sys );
 579 }
 580
 581 /*****************************************************************************
 582  * SyncInfo: parse MPEG audio sync info
 583  *****************************************************************************/
 584 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 585                      unsigned int * pi_channels_conf,
 586                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 587                      unsigned int * pi_frame_length,
 588                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 589 {
 590     static const int ppi_bitrate[2][3][16] =
 591     {
 592         {
 593             /* v1 l1 */
 594             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 595               416, 448, 0},
 596             /* v1 l2 */
 597             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 598               320, 384, 0},
 599             /* v1 l3 */
 600             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 601               256, 320, 0}
 602         },
 603
 604         {
 605             /* v2 l1 */
 606             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 607               224, 256, 0},
 608             /* v2 l2 */
 609             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 610               144, 160, 0},
 611             /* v2 l3 */
 612             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 613               144, 160, 0}
 614         }
 615     };
 616
 617     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 618     {
 619         { 44100, 48000, 32000, 0 },
 620         { 22050, 24000, 16000, 0 }
 621     };
 622
 623     int i_version, i_mode, i_emphasis;
 624     vlc_bool_t b_padding, b_mpeg_2_5, b_crc;
 625     int i_frame_size = 0;
 626     int i_bitrate_index, i_samplerate_index;
 627     int i_max_bit_rate;
 628
 629     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 630     i_version   = 1 - ((i_header & 0x80000) >> 19);
 631     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 632     b_crc = !((i_header >> 16) & 0x01);
 633     i_bitrate_index = (i_header & 0xf000) >> 12;
 634     i_samplerate_index = (i_header & 0xc00) >> 10;
 635     b_padding   = (i_header & 0x200) >> 9;
 636     /* Extension */
 637     i_mode      = (i_header & 0xc0) >> 6;
 638     /* Modeext, copyright & original */
 639     i_emphasis  = i_header & 0x3;
 640
 641     if( *pi_layer != 4 &&
 642         i_bitrate_index < 0x0f &&
 643         i_samplerate_index != 0x03 &&
 644         i_emphasis != 0x02 )
 645     {
 646         switch ( i_mode )
 647         {
 648         case 0: /* stereo */
 649         case 1: /* joint stereo */
 650             *pi_channels = 2;
 651             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 652             break;
 653         case 2: /* dual-mono */
 654             *pi_channels = 2;
 655             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 656                                 | AOUT_CHAN_DUALMONO;
 657             break;
 658         case 3: /* mono */
 659             *pi_channels = 1;
 660             *pi_channels_conf = AOUT_CHAN_CENTER;
 661             break;
 662         }
 663         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 664         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 665         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 666
 667         if ( b_mpeg_2_5 )
 668         {
 669             *pi_sample_rate >>= 1;
 670         }
 671
 672         switch( *pi_layer )
 673         {
 674         case 1:
 675             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 676                            b_padding ) * 4;
 677             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 678                                  *pi_sample_rate + 1 ) * 4;
 679             *pi_frame_length = 384;
 680             break;
 681
 682         case 2:
 683             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 684             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 685             *pi_frame_length = 1152;
 686             break;
 687
 688         case 3:
 689             i_frame_size = ( i_version ? 72000 : 144000 ) *
 690                            *pi_bit_rate / *pi_sample_rate + b_padding;
 691             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 692                                  i_max_bit_rate / *pi_sample_rate + 1;
 693             *pi_frame_length = i_version ? 576 : 1152;
 694             break;
 695
 696         default:
 697             break;
 698         }
 699     }
 700     else
 701     {
 702         return -1;
 703     }
 704
 705     return i_frame_size;
 706 }