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  * Open: probe the decoder and return score
 131  *****************************************************************************/
 132 static int Open( 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     /* 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         return VLC_ENOMEM;
 146
 147     /* Misc init */
 148     p_sys->b_packetizer = false;
 149     p_sys->i_state = STATE_NOSYNC;
 150     aout_DateSet( &p_sys->end_date, 0 );
 151     p_sys->bytestream = block_BytestreamInit();
 152     p_sys->b_discontinuity = false;
 153
 154     /* Set output properties */
 155     p_dec->fmt_out.i_cat = AUDIO_ES;
 156     p_dec->fmt_out.i_codec = VLC_FOURCC('m','p','g','a');
 157     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 158
 159     /* Set callback */
 160     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 161         DecodeBlock;
 162     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 163         DecodeBlock;
 164
 165     /* Start with the minimum size for a free bitrate frame */
 166     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 167
 168     return VLC_SUCCESS;
 169 }
 170
 171 static int OpenDecoder( vlc_object_t *p_this )
 172 {
 173     /* HACK: Don't use this codec if we don't have an mpga audio filter */
 174     if( !module_exists( "mpgatofixed32" ) )
 175         return VLC_EGENERIC;
 176
 177     return Open( p_this );
 178 }
 179
 180 static int OpenPacketizer( vlc_object_t *p_this )
 181 {
 182     decoder_t *p_dec = (decoder_t*)p_this;
 183
 184     int i_ret = Open( p_this );
 185
 186     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = true;
 187
 188     return i_ret;
 189 }
 190
 191 /****************************************************************************
 192  * DecodeBlock: the whole thing
 193  ****************************************************************************
 194  * This function is called just after the thread is launched.
 195  ****************************************************************************/
 196 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 197 {
 198     decoder_sys_t *p_sys = p_dec->p_sys;
 199     uint8_t p_header[MAD_BUFFER_GUARD];
 200     uint32_t i_header;
 201     uint8_t *p_buf;
 202     void *p_out_buffer;
 203
 204     if( !pp_block || !*pp_block ) return NULL;
 205
 206     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 207     {
 208         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 209         {
 210             p_sys->i_state = STATE_NOSYNC;
 211             block_BytestreamEmpty( &p_sys->bytestream );
 212         }
 213         aout_DateSet( &p_sys->end_date, 0 );
 214         block_Release( *pp_block );
 215         p_sys->b_discontinuity = true;
 216         return NULL;
 217     }
 218
 219     if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 220     {
 221         /* We've just started the stream, wait for the first PTS. */
 222         msg_Dbg( p_dec, "waiting for PTS" );
 223         block_Release( *pp_block );
 224         return NULL;
 225     }
 226
 227     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 228
 229     while( 1 )
 230     {
 231         switch( p_sys->i_state )
 232         {
 233
 234         case STATE_NOSYNC:
 235             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 236                    == VLC_SUCCESS )
 237             {
 238                 /* Look for sync word - should be 0xffe */
 239                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 240                 {
 241                     p_sys->i_state = STATE_SYNC;
 242                     break;
 243                 }
 244                 block_SkipByte( &p_sys->bytestream );
 245             }
 246             if( p_sys->i_state != STATE_SYNC )
 247             {
 248                 block_BytestreamFlush( &p_sys->bytestream );
 249
 250                 /* Need more data */
 251                 return NULL;
 252             }
 253
 254         case STATE_SYNC:
 255             /* New frame, set the Presentation Time Stamp */
 256             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 257             if( p_sys->i_pts != 0 &&
 258                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 259             {
 260                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 261             }
 262             p_sys->i_state = STATE_HEADER;
 263
 264         case STATE_HEADER:
 265             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 266             if( block_PeekBytes( &p_sys->bytestream, p_header,
 267                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 268             {
 269                 /* Need more data */
 270                 return NULL;
 271             }
 272
 273             /* Build frame header */
 274             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 275                        |p_header[3];
 276
 277             /* Check if frame is valid and get frame info */
 278             p_sys->i_frame_size = SyncInfo( i_header,
 279                                             &p_sys->i_channels,
 280                                             &p_sys->i_channels_conf,
 281                                             &p_sys->i_rate,
 282                                             &p_sys->i_bit_rate,
 283                                             &p_sys->i_frame_length,
 284                                             &p_sys->i_max_frame_size,
 285                                             &p_sys->i_layer );
 286
 287             if( p_sys->i_frame_size == -1 )
 288             {
 289                 msg_Dbg( p_dec, "emulated startcode" );
 290                 block_SkipByte( &p_sys->bytestream );
 291                 p_sys->i_state = STATE_NOSYNC;
 292                 p_sys->b_discontinuity = true;
 293                 break;
 294             }
 295
 296             if( p_sys->i_bit_rate == 0 )
 297             {
 298                 /* Free bitrate, but 99% emulated startcode :( */
 299                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 300                 {
 301                     msg_Dbg( p_dec, "free bitrate mode");
 302                 }
 303                 /* The -1 below is to account for the frame padding */
 304                 p_sys->i_frame_size = p_sys->i_free_frame_size - 1;
 305             }
 306
 307             p_sys->i_state = STATE_NEXT_SYNC;
 308
 309         case STATE_NEXT_SYNC:
 310             /* TODO: If p_block == NULL, flush the buffer without checking the
 311              * next sync word */
 312
 313             /* Check if next expected frame contains the sync word */
 314             if( block_PeekOffsetBytes( &p_sys->bytestream,
 315                                        p_sys->i_frame_size, p_header,
 316                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 317             {
 318                 /* Need more data */
 319                 return NULL;
 320             }
 321
 322             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 323             {
 324                 /* Startcode is fine, let's try the header as an extra check */
 325                 int i_next_frame_size;
 326                 unsigned int i_next_channels, i_next_channels_conf;
 327                 unsigned int i_next_rate, i_next_bit_rate;
 328                 unsigned int i_next_frame_length, i_next_max_frame_size;
 329                 unsigned int i_next_layer;
 330
 331                 /* Build frame header */
 332                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 333                            |p_header[3];
 334
 335                 i_next_frame_size = SyncInfo( i_header,
 336                                               &i_next_channels,
 337                                               &i_next_channels_conf,
 338                                               &i_next_rate,
 339                                               &i_next_bit_rate,
 340                                               &i_next_frame_length,
 341                                               &i_next_max_frame_size,
 342                                               &i_next_layer );
 343
 344                 /* Free bitrate only */
 345                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 346                 {
 347                     if( (unsigned int)p_sys->i_frame_size >
 348                         p_sys->i_max_frame_size )
 349                     {
 350                         msg_Dbg( p_dec, "frame too big %d > %d "
 351                                  "(emulated startcode ?)", p_sys->i_frame_size,
 352                                  p_sys->i_max_frame_size );
 353                         block_SkipByte( &p_sys->bytestream );
 354                         p_sys->i_state = STATE_NOSYNC;
 355                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 356                         break;
 357                     }
 358
 359                     p_sys->i_frame_size++;
 360                     break;
 361                 }
 362
 363                 if( i_next_frame_size == -1 )
 364                 {
 365                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 366                     block_SkipByte( &p_sys->bytestream );
 367                     p_sys->i_state = STATE_NOSYNC;
 368                     p_sys->b_discontinuity = true;
 369                     break;
 370                 }
 371
 372                 /* Check info is in sync with previous one */
 373                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 374                     i_next_rate != p_sys->i_rate ||
 375                     i_next_layer != p_sys->i_layer ||
 376                     i_next_frame_length != p_sys->i_frame_length )
 377                 {
 378                     /* Free bitrate only */
 379                     if( p_sys->i_bit_rate == 0 )
 380                     {
 381                         p_sys->i_frame_size++;
 382                         break;
 383                     }
 384
 385                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 386                              "(emulated startcode ?)" );
 387                     block_SkipByte( &p_sys->bytestream );
 388                     p_sys->i_state = STATE_NOSYNC;
 389                     break;
 390                 }
 391
 392                 /* Free bitrate only */
 393                 if( p_sys->i_bit_rate == 0 )
 394                 {
 395                     if( i_next_bit_rate != 0 )
 396                     {
 397                         p_sys->i_frame_size++;
 398                         break;
 399                     }
 400                 }
 401
 402             }
 403             else
 404             {
 405                 /* Free bitrate only */
 406                 if( p_sys->i_bit_rate == 0 )
 407                 {
 408                     if( (unsigned int)p_sys->i_frame_size >
 409                         p_sys->i_max_frame_size )
 410                     {
 411                         msg_Dbg( p_dec, "frame too big %d > %d "
 412                                  "(emulated startcode ?)", p_sys->i_frame_size,
 413                                  p_sys->i_max_frame_size );
 414                         block_SkipByte( &p_sys->bytestream );
 415                         p_sys->i_state = STATE_NOSYNC;
 416                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 417                         break;
 418                     }
 419
 420                     p_sys->i_frame_size++;
 421                     break;
 422                 }
 423
 424                 msg_Dbg( p_dec, "emulated startcode "
 425                          "(no startcode on following frame)" );
 426                 p_sys->i_state = STATE_NOSYNC;
 427                 block_SkipByte( &p_sys->bytestream );
 428                 break;
 429             }
 430
 431             p_sys->i_state = STATE_SEND_DATA;
 432             break;
 433
 434         case STATE_GET_DATA:
 435             /* Make sure we have enough data.
 436              * (Not useful if we went through NEXT_SYNC) */
 437             if( block_WaitBytes( &p_sys->bytestream,
 438                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 439             {
 440                 /* Need more data */
 441                 return NULL;
 442             }
 443             p_sys->i_state = STATE_SEND_DATA;
 444
 445         case STATE_SEND_DATA:
 446             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 447             {
 448                 //p_dec->b_error = true;
 449                 return NULL;
 450             }
 451
 452             /* Free bitrate only */
 453             if( p_sys->i_bit_rate == 0 )
 454             {
 455                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 456             }
 457
 458             /* Copy the whole frame into the buffer. When we reach this point
 459              * we already know we have enough data available. */
 460             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 461
 462             /* Get beginning of next frame for libmad */
 463             if( !p_sys->b_packetizer )
 464             {
 465                 memcpy( p_buf + p_sys->i_frame_size,
 466                         p_header, MAD_BUFFER_GUARD );
 467             }
 468
 469             p_sys->i_state = STATE_NOSYNC;
 470
 471             /* Make sure we don't reuse the same pts twice */
 472             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 473                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 474
 475             /* So p_block doesn't get re-added several times */
 476             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 477
 478             return p_out_buffer;
 479         }
 480     }
 481
 482     return NULL;
 483 }
 484
 485 /*****************************************************************************
 486  * GetOutBuffer:
 487  *****************************************************************************/
 488 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 489 {
 490     decoder_sys_t *p_sys = p_dec->p_sys;
 491     uint8_t *p_buf;
 492
 493     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 494     {
 495         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 496                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 497
 498         aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 499         aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 500     }
 501
 502     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 503     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 504     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 505     p_dec->fmt_out.audio.i_bytes_per_frame =
 506         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 507
 508     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 509     p_dec->fmt_out.audio.i_physical_channels =
 510         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 511
 512     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 513
 514     if( p_sys->b_packetizer )
 515     {
 516         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 517         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 518         *pp_out_buffer = p_sout_buffer;
 519     }
 520     else
 521     {
 522         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 523         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 524         *pp_out_buffer = p_aout_buffer;
 525     }
 526
 527     return p_buf;
 528 }
 529
 530 /*****************************************************************************
 531  * GetAoutBuffer:
 532  *****************************************************************************/
 533 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 534 {
 535     decoder_sys_t *p_sys = p_dec->p_sys;
 536     aout_buffer_t *p_buf;
 537
 538     p_buf = decoder_NewAudioBuffer( p_dec, p_sys->i_frame_length );
 539     if( p_buf == NULL ) return NULL;
 540
 541     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 542     p_buf->end_date =
 543         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 544     p_buf->b_discontinuity = p_sys->b_discontinuity;
 545     p_sys->b_discontinuity = false;
 546
 547     /* Hack for libmad filter */
 548     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 549
 550     return p_buf;
 551 }
 552
 553 /*****************************************************************************
 554  * GetSoutBuffer:
 555  *****************************************************************************/
 556 static block_t *GetSoutBuffer( decoder_t *p_dec )
 557 {
 558     decoder_sys_t *p_sys = p_dec->p_sys;
 559     block_t *p_block;
 560
 561     p_block = block_New( p_dec, p_sys->i_frame_size );
 562     if( p_block == NULL ) return NULL;
 563
 564     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 565
 566     p_block->i_length =
 567         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) - p_block->i_pts;
 568
 569     return p_block;
 570 }
 571
 572 /*****************************************************************************
 573  * CloseDecoder: clean up the decoder
 574  *****************************************************************************/
 575 static void CloseDecoder( vlc_object_t *p_this )
 576 {
 577     decoder_t *p_dec = (decoder_t *)p_this;
 578     decoder_sys_t *p_sys = p_dec->p_sys;
 579
 580     block_BytestreamRelease( &p_sys->bytestream );
 581
 582     free( p_sys );
 583 }
 584
 585 /*****************************************************************************
 586  * SyncInfo: parse MPEG audio sync info
 587  *****************************************************************************/
 588 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 589                      unsigned int * pi_channels_conf,
 590                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 591                      unsigned int * pi_frame_length,
 592                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 593 {
 594     static const int ppi_bitrate[2][3][16] =
 595     {
 596         {
 597             /* v1 l1 */
 598             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 599               416, 448, 0},
 600             /* v1 l2 */
 601             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 602               320, 384, 0},
 603             /* v1 l3 */
 604             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 605               256, 320, 0}
 606         },
 607
 608         {
 609             /* v2 l1 */
 610             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 611               224, 256, 0},
 612             /* v2 l2 */
 613             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 614               144, 160, 0},
 615             /* v2 l3 */
 616             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 617               144, 160, 0}
 618         }
 619     };
 620
 621     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 622     {
 623         { 44100, 48000, 32000, 0 },
 624         { 22050, 24000, 16000, 0 }
 625     };
 626
 627     int i_version, i_mode, i_emphasis;
 628     bool b_padding, b_mpeg_2_5, b_crc;
 629     int i_frame_size = 0;
 630     int i_bitrate_index, i_samplerate_index;
 631     int i_max_bit_rate;
 632
 633     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 634     i_version   = 1 - ((i_header & 0x80000) >> 19);
 635     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 636     b_crc = !((i_header >> 16) & 0x01);
 637     i_bitrate_index = (i_header & 0xf000) >> 12;
 638     i_samplerate_index = (i_header & 0xc00) >> 10;
 639     b_padding   = (i_header & 0x200) >> 9;
 640     /* Extension */
 641     i_mode      = (i_header & 0xc0) >> 6;
 642     /* Modeext, copyright & original */
 643     i_emphasis  = i_header & 0x3;
 644
 645     if( *pi_layer != 4 &&
 646         i_bitrate_index < 0x0f &&
 647         i_samplerate_index != 0x03 &&
 648         i_emphasis != 0x02 )
 649     {
 650         switch ( i_mode )
 651         {
 652         case 0: /* stereo */
 653         case 1: /* joint stereo */
 654             *pi_channels = 2;
 655             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 656             break;
 657         case 2: /* dual-mono */
 658             *pi_channels = 2;
 659             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 660                                 | AOUT_CHAN_DUALMONO;
 661             break;
 662         case 3: /* mono */
 663             *pi_channels = 1;
 664             *pi_channels_conf = AOUT_CHAN_CENTER;
 665             break;
 666         }
 667         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 668         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 669         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 670
 671         if ( b_mpeg_2_5 )
 672         {
 673             *pi_sample_rate >>= 1;
 674         }
 675
 676         switch( *pi_layer )
 677         {
 678         case 1:
 679             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 680                            b_padding ) * 4;
 681             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 682                                  *pi_sample_rate + 1 ) * 4;
 683             *pi_frame_length = 384;
 684             break;
 685
 686         case 2:
 687             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 688             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 689             *pi_frame_length = 1152;
 690             break;
 691
 692         case 3:
 693             i_frame_size = ( i_version ? 72000 : 144000 ) *
 694                            *pi_bit_rate / *pi_sample_rate + b_padding;
 695             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 696                                  i_max_bit_rate / *pi_sample_rate + 1;
 697             *pi_frame_length = i_version ? 576 : 1152;
 698             break;
 699
 700         default:
 701             break;
 702         }
 703
 704         /* Free bitrate mode can support higher bitrates */
 705         if( !*pi_bit_rate ) *pi_max_frame_size *= 2;
 706     }
 707     else
 708     {
 709         return -1;
 710     }
 711
 712     return i_frame_size;
 713 }