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