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( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 200     {
 201         /* We've just started the stream, wait for the first PTS. */
 202         msg_Dbg( p_dec, "waiting for PTS" );
 203         block_Release( *pp_block );
 204         return NULL;
 205     }
 206
 207     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 208     {
 209         p_sys->i_state = STATE_NOSYNC;
 210     }
 211
 212     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 213
 214     while( 1 )
 215     {
 216         switch( p_sys->i_state )
 217         {
 218
 219         case STATE_NOSYNC:
 220             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 221                    == VLC_SUCCESS )
 222             {
 223                 /* Look for sync word - should be 0xffe */
 224                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 225                 {
 226                     p_sys->i_state = STATE_SYNC;
 227                     break;
 228                 }
 229                 block_SkipByte( &p_sys->bytestream );
 230             }
 231             if( p_sys->i_state != STATE_SYNC )
 232             {
 233                 block_BytestreamFlush( &p_sys->bytestream );
 234
 235                 /* Need more data */
 236                 return NULL;
 237             }
 238
 239         case STATE_SYNC:
 240             /* New frame, set the Presentation Time Stamp */
 241             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 242             if( p_sys->i_pts != 0 &&
 243                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 244             {
 245                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 246             }
 247             p_sys->i_state = STATE_HEADER;
 248
 249         case STATE_HEADER:
 250             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 251             if( block_PeekBytes( &p_sys->bytestream, p_header,
 252                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 253             {
 254                 /* Need more data */
 255                 return NULL;
 256             }
 257
 258             /* Build frame header */
 259             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 260                        |p_header[3];
 261
 262             /* Check if frame is valid and get frame info */
 263             p_sys->i_frame_size = SyncInfo( i_header,
 264                                             &p_sys->i_channels,
 265                                             &p_sys->i_channels_conf,
 266                                             &p_sys->i_rate,
 267                                             &p_sys->i_bit_rate,
 268                                             &p_sys->i_frame_length,
 269                                             &p_sys->i_max_frame_size,
 270                                             &p_sys->i_layer );
 271
 272             if( p_sys->i_frame_size == -1 )
 273             {
 274                 msg_Dbg( p_dec, "emulated startcode" );
 275                 block_SkipByte( &p_sys->bytestream );
 276                 p_sys->i_state = STATE_NOSYNC;
 277                 break;
 278             }
 279
 280             if( p_sys->i_bit_rate == 0 )
 281             {
 282                 /* Free birate, but 99% emulated startcode :( */
 283                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 284                 {
 285                     msg_Dbg( p_dec, "free bitrate mode");
 286                 }
 287                 p_sys->i_frame_size = p_sys->i_free_frame_size;
 288             }
 289
 290             p_sys->i_state = STATE_NEXT_SYNC;
 291
 292         case STATE_NEXT_SYNC:
 293             /* TODO: If p_block == NULL, flush the buffer without checking the
 294              * next sync word */
 295
 296             /* Check if next expected frame contains the sync word */
 297             if( block_PeekOffsetBytes( &p_sys->bytestream,
 298                                        p_sys->i_frame_size, p_header,
 299                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 300             {
 301                 /* Need more data */
 302                 return NULL;
 303             }
 304
 305             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 306             {
 307                 /* Startcode is fine, let's try the header as an extra check */
 308                 int i_next_frame_size;
 309                 unsigned int i_next_channels, i_next_channels_conf;
 310                 unsigned int i_next_rate, i_next_bit_rate;
 311                 unsigned int i_next_frame_length, i_next_max_frame_size;
 312                 unsigned int i_next_layer;
 313
 314                 /* Build frame header */
 315                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 316                            |p_header[3];
 317
 318                 i_next_frame_size = SyncInfo( i_header,
 319                                               &i_next_channels,
 320                                               &i_next_channels_conf,
 321                                               &i_next_rate,
 322                                               &i_next_bit_rate,
 323                                               &i_next_frame_length,
 324                                               &i_next_max_frame_size,
 325                                               &i_next_layer );
 326
 327                 /* Free bitrate only */
 328                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 329                 {
 330                     if( (unsigned int)p_sys->i_frame_size >
 331                         p_sys->i_max_frame_size )
 332                     {
 333                         msg_Dbg( p_dec, "frame too big %d > %d "
 334                                  "(emulated startcode ?)", p_sys->i_frame_size,
 335                                  p_sys->i_max_frame_size );
 336                         block_SkipByte( &p_sys->bytestream );
 337                         p_sys->i_state = STATE_NOSYNC;
 338                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 339                         break;
 340                     }
 341
 342                     p_sys->i_frame_size++;
 343                     break;
 344                 }
 345
 346                 if( i_next_frame_size == -1 )
 347                 {
 348                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 349                     block_SkipByte( &p_sys->bytestream );
 350                     p_sys->i_state = STATE_NOSYNC;
 351                     break;
 352                 }
 353
 354                 /* Check info is in sync with previous one */
 355                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 356                     i_next_rate != p_sys->i_rate ||
 357                     i_next_layer != p_sys->i_layer ||
 358                     i_next_frame_length != p_sys->i_frame_length )
 359                 {
 360                     /* Free bitrate only */
 361                     if( p_sys->i_bit_rate == 0 )
 362                     {
 363                         p_sys->i_frame_size++;
 364                         break;
 365                     }
 366
 367                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 368                              "(emulated startcode ?)" );
 369                     block_SkipByte( &p_sys->bytestream );
 370                     p_sys->i_state = STATE_NOSYNC;
 371                     break;
 372                 }
 373
 374                 /* Free bitrate only */
 375                 if( p_sys->i_bit_rate == 0 )
 376                 {
 377                     if( i_next_bit_rate != 0 )
 378                     {
 379                         p_sys->i_frame_size++;
 380                         break;
 381                     }
 382                 }
 383
 384             }
 385             else
 386             {
 387                 /* Free bitrate only */
 388                 if( p_sys->i_bit_rate == 0 )
 389                 {
 390                     if( (unsigned int)p_sys->i_frame_size >
 391                         p_sys->i_max_frame_size )
 392                     {
 393                         msg_Dbg( p_dec, "frame too big %d > %d "
 394                                  "(emulated startcode ?)", p_sys->i_frame_size,
 395                                  p_sys->i_max_frame_size );
 396                         block_SkipByte( &p_sys->bytestream );
 397                         p_sys->i_state = STATE_NOSYNC;
 398                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 399                         break;
 400                     }
 401
 402                     p_sys->i_frame_size++;
 403                     break;
 404                 }
 405
 406                 msg_Dbg( p_dec, "emulated startcode "
 407                          "(no startcode on following frame)" );
 408                 p_sys->i_state = STATE_NOSYNC;
 409                 block_SkipByte( &p_sys->bytestream );
 410                 break;
 411             }
 412
 413             p_sys->i_state = STATE_SEND_DATA;
 414             break;
 415
 416         case STATE_GET_DATA:
 417             /* Make sure we have enough data.
 418              * (Not useful if we went through NEXT_SYNC) */
 419             if( block_WaitBytes( &p_sys->bytestream,
 420                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 421             {
 422                 /* Need more data */
 423                 return NULL;
 424             }
 425             p_sys->i_state = STATE_SEND_DATA;
 426
 427         case STATE_SEND_DATA:
 428             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 429             {
 430                 //p_dec->b_error = VLC_TRUE;
 431                 return NULL;
 432             }
 433
 434             /* Free bitrate only */
 435             if( p_sys->i_bit_rate == 0 )
 436             {
 437                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 438             }
 439
 440             /* Copy the whole frame into the buffer. When we reach this point
 441              * we already know we have enough data available. */
 442             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 443
 444             /* Get beginning of next frame for libmad */
 445             if( !p_sys->b_packetizer )
 446             {
 447                 memcpy( p_buf + p_sys->i_frame_size,
 448                         p_header, MAD_BUFFER_GUARD );
 449             }
 450
 451             p_sys->i_state = STATE_NOSYNC;
 452
 453             /* Make sure we don't reuse the same pts twice */
 454             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 455                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 456
 457             /* So p_block doesn't get re-added several times */
 458             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 459
 460             return p_out_buffer;
 461         }
 462     }
 463
 464     return NULL;
 465 }
 466
 467 /*****************************************************************************
 468  * GetOutBuffer:
 469  *****************************************************************************/
 470 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 471 {
 472     decoder_sys_t *p_sys = p_dec->p_sys;
 473     uint8_t *p_buf;
 474
 475     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 476     {
 477         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 478                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 479
 480         aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 481         aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 482     }
 483
 484     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 485     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 486     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 487     p_dec->fmt_out.audio.i_bytes_per_frame =
 488         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 489
 490     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 491     p_dec->fmt_out.audio.i_physical_channels =
 492         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 493
 494     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 495
 496     if( p_sys->b_packetizer )
 497     {
 498         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 499         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 500         *pp_out_buffer = p_sout_buffer;
 501     }
 502     else
 503     {
 504         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 505         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 506         *pp_out_buffer = p_aout_buffer;
 507     }
 508
 509     return p_buf;
 510 }
 511
 512 /*****************************************************************************
 513  * GetAoutBuffer:
 514  *****************************************************************************/
 515 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 516 {
 517     decoder_sys_t *p_sys = p_dec->p_sys;
 518     aout_buffer_t *p_buf;
 519
 520     p_buf = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_frame_length );
 521     if( p_buf == NULL ) return NULL;
 522
 523     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 524     p_buf->end_date =
 525         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 526
 527     /* Hack for libmad filter */
 528     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 529
 530     return p_buf;
 531 }
 532
 533 /*****************************************************************************
 534  * GetSoutBuffer:
 535  *****************************************************************************/
 536 static block_t *GetSoutBuffer( decoder_t *p_dec )
 537 {
 538     decoder_sys_t *p_sys = p_dec->p_sys;
 539     block_t *p_block;
 540
 541     p_block = block_New( p_dec, p_sys->i_frame_size );
 542     if( p_block == NULL ) return NULL;
 543
 544     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 545
 546     p_block->i_length =
 547         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) -
 548             p_block->i_pts;
 549
 550     return p_block;
 551 }
 552
 553 /*****************************************************************************
 554  * CloseDecoder: clean up the decoder
 555  *****************************************************************************/
 556 static void CloseDecoder( vlc_object_t *p_this )
 557 {
 558     decoder_t *p_dec = (decoder_t *)p_this;
 559     decoder_sys_t *p_sys = p_dec->p_sys;
 560
 561     block_BytestreamRelease( &p_sys->bytestream );
 562
 563     free( p_sys );
 564 }
 565
 566 /*****************************************************************************
 567  * SyncInfo: parse MPEG audio sync info
 568  *****************************************************************************/
 569 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 570                      unsigned int * pi_channels_conf,
 571                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 572                      unsigned int * pi_frame_length,
 573                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 574 {
 575     static const int ppi_bitrate[2][3][16] =
 576     {
 577         {
 578             /* v1 l1 */
 579             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 580               416, 448, 0},
 581             /* v1 l2 */
 582             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 583               320, 384, 0},
 584             /* v1 l3 */
 585             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 586               256, 320, 0}
 587         },
 588
 589         {
 590             /* v2 l1 */
 591             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 592               224, 256, 0},
 593             /* v2 l2 */
 594             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 595               144, 160, 0},
 596             /* v2 l3 */
 597             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 598               144, 160, 0}
 599         }
 600     };
 601
 602     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 603     {
 604         { 44100, 48000, 32000, 0 },
 605         { 22050, 24000, 16000, 0 }
 606     };
 607
 608     int i_version, i_mode, i_emphasis;
 609     vlc_bool_t b_padding, b_mpeg_2_5, b_crc;
 610     int i_frame_size = 0;
 611     int i_bitrate_index, i_samplerate_index;
 612     int i_max_bit_rate;
 613
 614     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 615     i_version   = 1 - ((i_header & 0x80000) >> 19);
 616     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 617     b_crc = !((i_header >> 16) & 0x01);
 618     i_bitrate_index = (i_header & 0xf000) >> 12;
 619     i_samplerate_index = (i_header & 0xc00) >> 10;
 620     b_padding   = (i_header & 0x200) >> 9;
 621     /* Extension */
 622     i_mode      = (i_header & 0xc0) >> 6;
 623     /* Modeext, copyright & original */
 624     i_emphasis  = i_header & 0x3;
 625
 626     if( *pi_layer != 4 &&
 627         i_bitrate_index < 0x0f &&
 628         i_samplerate_index != 0x03 &&
 629         i_emphasis != 0x02 )
 630     {
 631         switch ( i_mode )
 632         {
 633         case 0: /* stereo */
 634         case 1: /* joint stereo */
 635             *pi_channels = 2;
 636             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 637             break;
 638         case 2: /* dual-mono */
 639             *pi_channels = 2;
 640             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 641                                 | AOUT_CHAN_DUALMONO;
 642             break;
 643         case 3: /* mono */
 644             *pi_channels = 1;
 645             *pi_channels_conf = AOUT_CHAN_CENTER;
 646             break;
 647         }
 648         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 649         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 650         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 651
 652         if ( b_mpeg_2_5 )
 653         {
 654             *pi_sample_rate >>= 1;
 655         }
 656
 657         switch( *pi_layer )
 658         {
 659         case 1:
 660             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 661                            b_padding ) * 4;
 662             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 663                                  *pi_sample_rate + 1 ) * 4;
 664             *pi_frame_length = 384;
 665             break;
 666
 667         case 2:
 668             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 669             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 670             *pi_frame_length = 1152;
 671             break;
 672
 673         case 3:
 674             i_frame_size = ( i_version ? 72000 : 144000 ) *
 675                            *pi_bit_rate / *pi_sample_rate + b_padding;
 676             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 677                                  i_max_bit_rate / *pi_sample_rate + 1;
 678             *pi_frame_length = i_version ? 576 : 1152;
 679             break;
 680
 681         default:
 682             break;
 683         }
 684     }
 685     else
 686     {
 687         return -1;
 688     }
 689
 690     return i_frame_size;
 691 }