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 #ifdef HAVE_CONFIG_H
  31 # include "config.h"
  32 #endif
  33
  34 #include <vlc_common.h>
  35 #include <vlc_plugin.h>
  36 #include <vlc_codec.h>
  37 #include <vlc_aout.h>
  38
  39 #include <vlc_block_helper.h>
  40
  41 /*****************************************************************************
  42  * decoder_sys_t : decoder descriptor
  43  *****************************************************************************/
  44 struct decoder_sys_t
  45 {
  46     /* Module mode */
  47     bool b_packetizer;
  48
  49     /*
  50      * Input properties
  51      */
  52     int        i_state;
  53
  54     block_bytestream_t bytestream;
  55
  56     /*
  57      * Common properties
  58      */
  59     audio_date_t          end_date;
  60     unsigned int          i_current_layer;
  61
  62     mtime_t i_pts;
  63
  64     int i_frame_size, i_free_frame_size;
  65     unsigned int i_channels_conf, i_channels;
  66     unsigned int i_rate, i_max_frame_size, i_frame_length;
  67     unsigned int i_layer, i_bit_rate;
  68
  69     bool   b_discontinuity;
  70 };
  71
  72 enum {
  73
  74     STATE_NOSYNC,
  75     STATE_SYNC,
  76     STATE_HEADER,
  77     STATE_NEXT_SYNC,
  78     STATE_GET_DATA,
  79     STATE_SEND_DATA
  80 };
  81
  82 /* This isn't the place to put mad-specific stuff. However, it makes the
  83  * mad plug-in's life much easier if we put 8 extra bytes at the end of the
  84  * buffer, because that way it doesn't have to copy the aout_buffer_t to a
  85  * bigger buffer. This has no implication on other plug-ins, and we only
  86  * lose 8 bytes per frame. --Meuuh */
  87 #define MAD_BUFFER_GUARD 8
  88 #define MPGA_HEADER_SIZE 4
  89
  90 /****************************************************************************
  91  * Local prototypes
  92  ****************************************************************************/
  93 static int  OpenDecoder   ( vlc_object_t * );
  94 static int  OpenPacketizer( vlc_object_t * );
  95 static void CloseDecoder  ( vlc_object_t * );
  96 static void *DecodeBlock  ( decoder_t *, block_t ** );
  97
  98 static uint8_t       *GetOutBuffer ( decoder_t *, void ** );
  99 static aout_buffer_t *GetAoutBuffer( decoder_t * );
 100 static block_t       *GetSoutBuffer( decoder_t * );
 101
 102 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 103                      unsigned int * pi_channels_conf,
 104                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 105                      unsigned int * pi_frame_length,
 106                      unsigned int * pi_max_frame_size,
 107                      unsigned int * pi_layer );
 108
 109 /*****************************************************************************
 110  * Module descriptor
 111  *****************************************************************************/
 112 vlc_module_begin ()
 113     set_description( N_("MPEG audio layer I/II/III decoder") )
 114     set_category( CAT_INPUT )
 115     set_subcategory( SUBCAT_INPUT_ACODEC )
 116 #if defined(UNDER_CE)
 117    set_capability( "decoder", 5 )
 118 #else
 119     set_capability( "decoder", 100 )
 120 #endif
 121     set_callbacks( OpenDecoder, CloseDecoder )
 122
 123     add_submodule ()
 124     set_description( N_("MPEG audio layer I/II/III packetizer") )
 125     set_capability( "packetizer", 10 )
 126     set_callbacks( OpenPacketizer, CloseDecoder )
 127 vlc_module_end ()
 128
 129 /*****************************************************************************
 130  * OpenDecoder: probe the decoder and return score
 131  *****************************************************************************/
 132 static int OpenDecoder( vlc_object_t *p_this )
 133 {
 134     decoder_t *p_dec = (decoder_t*)p_this;
 135     decoder_sys_t *p_sys;
 136
 137     if( p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','a') )
 138     {
 139         return VLC_EGENERIC;
 140     }
 141
 142     /* HACK: Don't use this codec if we don't have an mpga audio filter */
 143     if( p_dec->i_object_type == VLC_OBJECT_DECODER &&
 144         !module_exists( "mpgatofixed32" ) )
 145     {
 146         return VLC_EGENERIC;
 147     }
 148
 149     /* Allocate the memory needed to store the decoder's structure */
 150     if( ( p_dec->p_sys = p_sys =
 151           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 152         return VLC_ENOMEM;
 153
 154     /* Misc init */
 155     p_sys->b_packetizer = false;
 156     p_sys->i_state = STATE_NOSYNC;
 157     aout_DateSet( &p_sys->end_date, 0 );
 158     p_sys->bytestream = block_BytestreamInit();
 159     p_sys->b_discontinuity = false;
 160
 161     /* Set output properties */
 162     p_dec->fmt_out.i_cat = AUDIO_ES;
 163     p_dec->fmt_out.i_codec = VLC_FOURCC('m','p','g','a');
 164     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 165
 166     /* Set callback */
 167     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 168         DecodeBlock;
 169     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 170         DecodeBlock;
 171
 172     /* Start with the minimum size for a free bitrate frame */
 173     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 174
 175     return VLC_SUCCESS;
 176 }
 177
 178 static int OpenPacketizer( vlc_object_t *p_this )
 179 {
 180     decoder_t *p_dec = (decoder_t*)p_this;
 181
 182     int i_ret = OpenDecoder( p_this );
 183
 184     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = true;
 185
 186     return i_ret;
 187 }
 188
 189 /****************************************************************************
 190  * DecodeBlock: the whole thing
 191  ****************************************************************************
 192  * This function is called just after the thread is launched.
 193  ****************************************************************************/
 194 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 195 {
 196     decoder_sys_t *p_sys = p_dec->p_sys;
 197     uint8_t p_header[MAD_BUFFER_GUARD];
 198     uint32_t i_header;
 199     uint8_t *p_buf;
 200     void *p_out_buffer;
 201
 202     if( !pp_block || !*pp_block ) return NULL;
 203
 204     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 205     {
 206         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 207         {
 208             p_sys->i_state = STATE_NOSYNC;
 209             block_BytestreamFlush( &p_sys->bytestream );
 210         }
 211         aout_DateSet( &p_sys->end_date, 0 );
 212         block_Release( *pp_block );
 213         p_sys->b_discontinuity = true;
 214         return NULL;
 215     }
 216
 217     if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 218     {
 219         /* We've just started the stream, wait for the first PTS. */
 220         msg_Dbg( p_dec, "waiting for PTS" );
 221         block_Release( *pp_block );
 222         return NULL;
 223     }
 224
 225     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 226
 227     while( 1 )
 228     {
 229         switch( p_sys->i_state )
 230         {
 231
 232         case STATE_NOSYNC:
 233             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 234                    == VLC_SUCCESS )
 235             {
 236                 /* Look for sync word - should be 0xffe */
 237                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 238                 {
 239                     p_sys->i_state = STATE_SYNC;
 240                     break;
 241                 }
 242                 block_SkipByte( &p_sys->bytestream );
 243             }
 244             if( p_sys->i_state != STATE_SYNC )
 245             {
 246                 block_BytestreamFlush( &p_sys->bytestream );
 247
 248                 /* Need more data */
 249                 return NULL;
 250             }
 251
 252         case STATE_SYNC:
 253             /* New frame, set the Presentation Time Stamp */
 254             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 255             if( p_sys->i_pts != 0 &&
 256                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 257             {
 258                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 259             }
 260             p_sys->i_state = STATE_HEADER;
 261
 262         case STATE_HEADER:
 263             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 264             if( block_PeekBytes( &p_sys->bytestream, p_header,
 265                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 266             {
 267                 /* Need more data */
 268                 return NULL;
 269             }
 270
 271             /* Build frame header */
 272             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 273                        |p_header[3];
 274
 275             /* Check if frame is valid and get frame info */
 276             p_sys->i_frame_size = SyncInfo( i_header,
 277                                             &p_sys->i_channels,
 278                                             &p_sys->i_channels_conf,
 279                                             &p_sys->i_rate,
 280                                             &p_sys->i_bit_rate,
 281                                             &p_sys->i_frame_length,
 282                                             &p_sys->i_max_frame_size,
 283                                             &p_sys->i_layer );
 284
 285             if( p_sys->i_frame_size == -1 )
 286             {
 287                 msg_Dbg( p_dec, "emulated startcode" );
 288                 block_SkipByte( &p_sys->bytestream );
 289                 p_sys->i_state = STATE_NOSYNC;
 290                 p_sys->b_discontinuity = true;
 291                 break;
 292             }
 293
 294             if( p_sys->i_bit_rate == 0 )
 295             {
 296                 /* Free bitrate, but 99% emulated startcode :( */
 297                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 298                 {
 299                     msg_Dbg( p_dec, "free bitrate mode");
 300                 }
 301                 /* The -1 below is to account for the frame padding */
 302                 p_sys->i_frame_size = p_sys->i_free_frame_size - 1;
 303             }
 304
 305             p_sys->i_state = STATE_NEXT_SYNC;
 306
 307         case STATE_NEXT_SYNC:
 308             /* TODO: If p_block == NULL, flush the buffer without checking the
 309              * next sync word */
 310
 311             /* Check if next expected frame contains the sync word */
 312             if( block_PeekOffsetBytes( &p_sys->bytestream,
 313                                        p_sys->i_frame_size, p_header,
 314                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 315             {
 316                 /* Need more data */
 317                 return NULL;
 318             }
 319
 320             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 321             {
 322                 /* Startcode is fine, let's try the header as an extra check */
 323                 int i_next_frame_size;
 324                 unsigned int i_next_channels, i_next_channels_conf;
 325                 unsigned int i_next_rate, i_next_bit_rate;
 326                 unsigned int i_next_frame_length, i_next_max_frame_size;
 327                 unsigned int i_next_layer;
 328
 329                 /* Build frame header */
 330                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 331                            |p_header[3];
 332
 333                 i_next_frame_size = SyncInfo( i_header,
 334                                               &i_next_channels,
 335                                               &i_next_channels_conf,
 336                                               &i_next_rate,
 337                                               &i_next_bit_rate,
 338                                               &i_next_frame_length,
 339                                               &i_next_max_frame_size,
 340                                               &i_next_layer );
 341
 342                 /* Free bitrate only */
 343                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 344                 {
 345                     if( (unsigned int)p_sys->i_frame_size >
 346                         p_sys->i_max_frame_size )
 347                     {
 348                         msg_Dbg( p_dec, "frame too big %d > %d "
 349                                  "(emulated startcode ?)", p_sys->i_frame_size,
 350                                  p_sys->i_max_frame_size );
 351                         block_SkipByte( &p_sys->bytestream );
 352                         p_sys->i_state = STATE_NOSYNC;
 353                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 354                         break;
 355                     }
 356
 357                     p_sys->i_frame_size++;
 358                     break;
 359                 }
 360
 361                 if( i_next_frame_size == -1 )
 362                 {
 363                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 364                     block_SkipByte( &p_sys->bytestream );
 365                     p_sys->i_state = STATE_NOSYNC;
 366                     p_sys->b_discontinuity = true;
 367                     break;
 368                 }
 369
 370                 /* Check info is in sync with previous one */
 371                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 372                     i_next_rate != p_sys->i_rate ||
 373                     i_next_layer != p_sys->i_layer ||
 374                     i_next_frame_length != p_sys->i_frame_length )
 375                 {
 376                     /* Free bitrate only */
 377                     if( p_sys->i_bit_rate == 0 )
 378                     {
 379                         p_sys->i_frame_size++;
 380                         break;
 381                     }
 382
 383                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 384                              "(emulated startcode ?)" );
 385                     block_SkipByte( &p_sys->bytestream );
 386                     p_sys->i_state = STATE_NOSYNC;
 387                     break;
 388                 }
 389
 390                 /* Free bitrate only */
 391                 if( p_sys->i_bit_rate == 0 )
 392                 {
 393                     if( i_next_bit_rate != 0 )
 394                     {
 395                         p_sys->i_frame_size++;
 396                         break;
 397                     }
 398                 }
 399
 400             }
 401             else
 402             {
 403                 /* Free bitrate only */
 404                 if( p_sys->i_bit_rate == 0 )
 405                 {
 406                     if( (unsigned int)p_sys->i_frame_size >
 407                         p_sys->i_max_frame_size )
 408                     {
 409                         msg_Dbg( p_dec, "frame too big %d > %d "
 410                                  "(emulated startcode ?)", p_sys->i_frame_size,
 411                                  p_sys->i_max_frame_size );
 412                         block_SkipByte( &p_sys->bytestream );
 413                         p_sys->i_state = STATE_NOSYNC;
 414                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 415                         break;
 416                     }
 417
 418                     p_sys->i_frame_size++;
 419                     break;
 420                 }
 421
 422                 msg_Dbg( p_dec, "emulated startcode "
 423                          "(no startcode on following frame)" );
 424                 p_sys->i_state = STATE_NOSYNC;
 425                 block_SkipByte( &p_sys->bytestream );
 426                 break;
 427             }
 428
 429             p_sys->i_state = STATE_SEND_DATA;
 430             break;
 431
 432         case STATE_GET_DATA:
 433             /* Make sure we have enough data.
 434              * (Not useful if we went through NEXT_SYNC) */
 435             if( block_WaitBytes( &p_sys->bytestream,
 436                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 437             {
 438                 /* Need more data */
 439                 return NULL;
 440             }
 441             p_sys->i_state = STATE_SEND_DATA;
 442
 443         case STATE_SEND_DATA:
 444             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 445             {
 446                 //p_dec->b_error = true;
 447                 return NULL;
 448             }
 449
 450             /* Free bitrate only */
 451             if( p_sys->i_bit_rate == 0 )
 452             {
 453                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 454             }
 455
 456             /* Copy the whole frame into the buffer. When we reach this point
 457              * we already know we have enough data available. */
 458             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 459
 460             /* Get beginning of next frame for libmad */
 461             if( !p_sys->b_packetizer )
 462             {
 463                 memcpy( p_buf + p_sys->i_frame_size,
 464                         p_header, MAD_BUFFER_GUARD );
 465             }
 466
 467             p_sys->i_state = STATE_NOSYNC;
 468
 469             /* Make sure we don't reuse the same pts twice */
 470             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 471                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 472
 473             /* So p_block doesn't get re-added several times */
 474             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 475
 476             return p_out_buffer;
 477         }
 478     }
 479
 480     return NULL;
 481 }
 482
 483 /*****************************************************************************
 484  * GetOutBuffer:
 485  *****************************************************************************/
 486 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 487 {
 488     decoder_sys_t *p_sys = p_dec->p_sys;
 489     uint8_t *p_buf;
 490
 491     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 492     {
 493         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 494                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 495
 496         aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 497         aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 498     }
 499
 500     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 501     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 502     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 503     p_dec->fmt_out.audio.i_bytes_per_frame =
 504         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 505
 506     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 507     p_dec->fmt_out.audio.i_physical_channels =
 508         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 509
 510     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 511
 512     if( p_sys->b_packetizer )
 513     {
 514         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 515         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 516         *pp_out_buffer = p_sout_buffer;
 517     }
 518     else
 519     {
 520         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 521         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 522         *pp_out_buffer = p_aout_buffer;
 523     }
 524
 525     return p_buf;
 526 }
 527
 528 /*****************************************************************************
 529  * GetAoutBuffer:
 530  *****************************************************************************/
 531 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 532 {
 533     decoder_sys_t *p_sys = p_dec->p_sys;
 534     aout_buffer_t *p_buf;
 535
 536     p_buf = decoder_NewAudioBuffer( p_dec, p_sys->i_frame_length );
 537     if( p_buf == NULL ) return NULL;
 538
 539     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 540     p_buf->end_date =
 541         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 542     p_buf->b_discontinuity = p_sys->b_discontinuity;
 543     p_sys->b_discontinuity = false;
 544
 545     /* Hack for libmad filter */
 546     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 547
 548     return p_buf;
 549 }
 550
 551 /*****************************************************************************
 552  * GetSoutBuffer:
 553  *****************************************************************************/
 554 static block_t *GetSoutBuffer( decoder_t *p_dec )
 555 {
 556     decoder_sys_t *p_sys = p_dec->p_sys;
 557     block_t *p_block;
 558
 559     p_block = block_New( p_dec, p_sys->i_frame_size );
 560     if( p_block == NULL ) return NULL;
 561
 562     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 563
 564     p_block->i_length =
 565         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) - p_block->i_pts;
 566
 567     return p_block;
 568 }
 569
 570 /*****************************************************************************
 571  * CloseDecoder: clean up the decoder
 572  *****************************************************************************/
 573 static void CloseDecoder( vlc_object_t *p_this )
 574 {
 575     decoder_t *p_dec = (decoder_t *)p_this;
 576     decoder_sys_t *p_sys = p_dec->p_sys;
 577
 578     block_BytestreamRelease( &p_sys->bytestream );
 579
 580     free( p_sys );
 581 }
 582
 583 /*****************************************************************************
 584  * SyncInfo: parse MPEG audio sync info
 585  *****************************************************************************/
 586 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 587                      unsigned int * pi_channels_conf,
 588                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 589                      unsigned int * pi_frame_length,
 590                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 591 {
 592     static const int ppi_bitrate[2][3][16] =
 593     {
 594         {
 595             /* v1 l1 */
 596             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 597               416, 448, 0},
 598             /* v1 l2 */
 599             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 600               320, 384, 0},
 601             /* v1 l3 */
 602             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 603               256, 320, 0}
 604         },
 605
 606         {
 607             /* v2 l1 */
 608             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 609               224, 256, 0},
 610             /* v2 l2 */
 611             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 612               144, 160, 0},
 613             /* v2 l3 */
 614             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 615               144, 160, 0}
 616         }
 617     };
 618
 619     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 620     {
 621         { 44100, 48000, 32000, 0 },
 622         { 22050, 24000, 16000, 0 }
 623     };
 624
 625     int i_version, i_mode, i_emphasis;
 626     bool b_padding, b_mpeg_2_5, b_crc;
 627     int i_frame_size = 0;
 628     int i_bitrate_index, i_samplerate_index;
 629     int i_max_bit_rate;
 630
 631     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 632     i_version   = 1 - ((i_header & 0x80000) >> 19);
 633     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 634     b_crc = !((i_header >> 16) & 0x01);
 635     i_bitrate_index = (i_header & 0xf000) >> 12;
 636     i_samplerate_index = (i_header & 0xc00) >> 10;
 637     b_padding   = (i_header & 0x200) >> 9;
 638     /* Extension */
 639     i_mode      = (i_header & 0xc0) >> 6;
 640     /* Modeext, copyright & original */
 641     i_emphasis  = i_header & 0x3;
 642
 643     if( *pi_layer != 4 &&
 644         i_bitrate_index < 0x0f &&
 645         i_samplerate_index != 0x03 &&
 646         i_emphasis != 0x02 )
 647     {
 648         switch ( i_mode )
 649         {
 650         case 0: /* stereo */
 651         case 1: /* joint stereo */
 652             *pi_channels = 2;
 653             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 654             break;
 655         case 2: /* dual-mono */
 656             *pi_channels = 2;
 657             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 658                                 | AOUT_CHAN_DUALMONO;
 659             break;
 660         case 3: /* mono */
 661             *pi_channels = 1;
 662             *pi_channels_conf = AOUT_CHAN_CENTER;
 663             break;
 664         }
 665         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 666         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 667         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 668
 669         if ( b_mpeg_2_5 )
 670         {
 671             *pi_sample_rate >>= 1;
 672         }
 673
 674         switch( *pi_layer )
 675         {
 676         case 1:
 677             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 678                            b_padding ) * 4;
 679             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 680                                  *pi_sample_rate + 1 ) * 4;
 681             *pi_frame_length = 384;
 682             break;
 683
 684         case 2:
 685             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 686             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 687             *pi_frame_length = 1152;
 688             break;
 689
 690         case 3:
 691             i_frame_size = ( i_version ? 72000 : 144000 ) *
 692                            *pi_bit_rate / *pi_sample_rate + b_padding;
 693             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 694                                  i_max_bit_rate / *pi_sample_rate + 1;
 695             *pi_frame_length = i_version ? 576 : 1152;
 696             break;
 697
 698         default:
 699             break;
 700         }
 701
 702         /* Free bitrate mode can support higher bitrates */
 703         if( !*pi_bit_rate ) *pi_max_frame_size *= 2;
 704     }
 705     else
 706     {
 707         return -1;
 708     }
 709
 710     return i_frame_size;
 711 }