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 VideoLAN
   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@netcourrier.com>
  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., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  25  *****************************************************************************/
  26
  27 /*****************************************************************************
  28  * Preamble
  29  *****************************************************************************/
  30 #include <vlc/vlc.h>
  31 #include <vlc/decoder.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 parser") );
 107     set_category( CAT_INPUT );
 108     set_subcategory( SUBCAT_INPUT_ACODEC );
 109 #if defined(SYS_DARWIN) || 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     /* Allocate the memory needed to store the decoder's structure */
 136     if( ( p_dec->p_sys = p_sys =
 137           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 138     {
 139         msg_Err( p_dec, "out of memory" );
 140         return VLC_EGENERIC;
 141     }
 142
 143     /* Misc init */
 144     p_sys->b_packetizer = VLC_FALSE;
 145     p_sys->i_state = STATE_NOSYNC;
 146     aout_DateSet( &p_sys->end_date, 0 );
 147     p_sys->bytestream = block_BytestreamInit( p_dec );
 148
 149     /* Set output properties */
 150     p_dec->fmt_out.i_cat = AUDIO_ES;
 151     p_dec->fmt_out.i_codec = VLC_FOURCC('m','p','g','a');
 152     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 153
 154     /* Set callback */
 155     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 156         DecodeBlock;
 157     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 158         DecodeBlock;
 159
 160     /* Start with the minimum size for a free bitrate frame */
 161     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 162
 163     return VLC_SUCCESS;
 164 }
 165
 166 static int OpenPacketizer( vlc_object_t *p_this )
 167 {
 168     decoder_t *p_dec = (decoder_t*)p_this;
 169
 170     int i_ret = OpenDecoder( p_this );
 171
 172     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = VLC_TRUE;
 173
 174     return i_ret;
 175 }
 176
 177 /****************************************************************************
 178  * DecodeBlock: the whole thing
 179  ****************************************************************************
 180  * This function is called just after the thread is launched.
 181  ****************************************************************************/
 182 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 183 {
 184     decoder_sys_t *p_sys = p_dec->p_sys;
 185     uint8_t p_header[MAD_BUFFER_GUARD];
 186     uint32_t i_header;
 187     uint8_t *p_buf;
 188     void *p_out_buffer;
 189
 190     if( !pp_block || !*pp_block ) return NULL;
 191
 192     if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 193     {
 194         /* We've just started the stream, wait for the first PTS. */
 195         block_Release( *pp_block );
 196         return NULL;
 197     }
 198
 199     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 200     {
 201         p_sys->i_state = STATE_NOSYNC;
 202     }
 203
 204     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 205
 206     while( 1 )
 207     {
 208         switch( p_sys->i_state )
 209         {
 210
 211         case STATE_NOSYNC:
 212             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 213                    == VLC_SUCCESS )
 214             {
 215                 /* Look for sync word - should be 0xffe */
 216                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 217                 {
 218                     p_sys->i_state = STATE_SYNC;
 219                     break;
 220                 }
 221                 block_SkipByte( &p_sys->bytestream );
 222             }
 223             if( p_sys->i_state != STATE_SYNC )
 224             {
 225                 block_BytestreamFlush( &p_sys->bytestream );
 226
 227                 /* Need more data */
 228                 return NULL;
 229             }
 230
 231         case STATE_SYNC:
 232             /* New frame, set the Presentation Time Stamp */
 233             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 234             if( p_sys->i_pts != 0 &&
 235                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 236             {
 237                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 238             }
 239             p_sys->i_state = STATE_HEADER;
 240
 241         case STATE_HEADER:
 242             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 243             if( block_PeekBytes( &p_sys->bytestream, p_header,
 244                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 245             {
 246                 /* Need more data */
 247                 return NULL;
 248             }
 249
 250             /* Build frame header */
 251             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 252                        |p_header[3];
 253
 254             /* Check if frame is valid and get frame info */
 255             p_sys->i_frame_size = SyncInfo( i_header,
 256                                             &p_sys->i_channels,
 257                                             &p_sys->i_channels_conf,
 258                                             &p_sys->i_rate,
 259                                             &p_sys->i_bit_rate,
 260                                             &p_sys->i_frame_length,
 261                                             &p_sys->i_max_frame_size,
 262                                             &p_sys->i_layer );
 263
 264             if( p_sys->i_frame_size == -1 )
 265             {
 266                 msg_Dbg( p_dec, "emulated startcode" );
 267                 block_SkipByte( &p_sys->bytestream );
 268                 p_sys->i_state = STATE_NOSYNC;
 269                 break;
 270             }
 271
 272             if( p_sys->i_bit_rate == 0 )
 273             {
 274                 /* Free birate, but 99% emulated startcode :( */
 275                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 276                 {
 277                     msg_Dbg( p_dec, "free bitrate mode");
 278                 }
 279                 p_sys->i_frame_size = p_sys->i_free_frame_size;
 280             }
 281
 282             p_sys->i_state = STATE_NEXT_SYNC;
 283
 284         case STATE_NEXT_SYNC:
 285             /* TODO: If p_block == NULL, flush the buffer without checking the
 286              * next sync word */
 287
 288             /* Check if next expected frame contains the sync word */
 289             if( block_PeekOffsetBytes( &p_sys->bytestream,
 290                                        p_sys->i_frame_size, p_header,
 291                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 292             {
 293                 /* Need more data */
 294                 return NULL;
 295             }
 296
 297             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 298             {
 299                 /* Startcode is fine, let's try the header as an extra check */
 300                 int i_next_frame_size;
 301                 unsigned int i_next_channels, i_next_channels_conf;
 302                 unsigned int i_next_rate, i_next_bit_rate;
 303                 unsigned int i_next_frame_length, i_next_max_frame_size;
 304                 unsigned int i_next_layer;
 305
 306                 /* Build frame header */
 307                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 308                            |p_header[3];
 309
 310                 i_next_frame_size = SyncInfo( i_header,
 311                                               &i_next_channels,
 312                                               &i_next_channels_conf,
 313                                               &i_next_rate,
 314                                               &i_next_bit_rate,
 315                                               &i_next_frame_length,
 316                                               &i_next_max_frame_size,
 317                                               &i_next_layer );
 318
 319                 /* Free bitrate only */
 320                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 321                 {
 322                     if( (unsigned int)p_sys->i_frame_size >
 323                         p_sys->i_max_frame_size )
 324                     {
 325                         msg_Dbg( p_dec, "frame too big %d > %d "
 326                                  "(emulated startcode ?)", p_sys->i_frame_size,
 327                                  p_sys->i_max_frame_size );
 328                         block_SkipByte( &p_sys->bytestream );
 329                         p_sys->i_state = STATE_NOSYNC;
 330                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 331                         break;
 332                     }
 333
 334                     p_sys->i_frame_size++;
 335                     break;
 336                 }
 337
 338                 if( i_next_frame_size == -1 )
 339                 {
 340                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 341                     block_SkipByte( &p_sys->bytestream );
 342                     p_sys->i_state = STATE_NOSYNC;
 343                     break;
 344                 }
 345
 346                 /* Check info is in sync with previous one */
 347                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 348                     i_next_rate != p_sys->i_rate ||
 349                     i_next_layer != p_sys->i_layer ||
 350                     i_next_frame_length != p_sys->i_frame_length )
 351                 {
 352                     /* Free bitrate only */
 353                     if( p_sys->i_bit_rate == 0 )
 354                     {
 355                         p_sys->i_frame_size++;
 356                         break;
 357                     }
 358
 359                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 360                              "(emulated startcode ?)" );
 361                     block_SkipByte( &p_sys->bytestream );
 362                     p_sys->i_state = STATE_NOSYNC;
 363                     break;
 364                 }
 365
 366                 /* Free bitrate only */
 367                 if( p_sys->i_bit_rate == 0 )
 368                 {
 369                     if( i_next_bit_rate != 0 )
 370                     {
 371                         p_sys->i_frame_size++;
 372                         break;
 373                     }
 374                 }
 375
 376             }
 377             else
 378             {
 379                 /* Free bitrate only */
 380                 if( p_sys->i_bit_rate == 0 )
 381                 {
 382                     if( (unsigned int)p_sys->i_frame_size >
 383                         p_sys->i_max_frame_size )
 384                     {
 385                         msg_Dbg( p_dec, "frame too big %d > %d "
 386                                  "(emulated startcode ?)", p_sys->i_frame_size,
 387                                  p_sys->i_max_frame_size );
 388                         block_SkipByte( &p_sys->bytestream );
 389                         p_sys->i_state = STATE_NOSYNC;
 390                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 391                         break;
 392                     }
 393
 394                     p_sys->i_frame_size++;
 395                     break;
 396                 }
 397
 398                 msg_Dbg( p_dec, "emulated startcode "
 399                          "(no startcode on following frame)" );
 400                 p_sys->i_state = STATE_NOSYNC;
 401                 block_SkipByte( &p_sys->bytestream );
 402                 break;
 403             }
 404
 405             p_sys->i_state = STATE_SEND_DATA;
 406             break;
 407
 408         case STATE_GET_DATA:
 409             /* Make sure we have enough data.
 410              * (Not useful if we went through NEXT_SYNC) */
 411             if( block_WaitBytes( &p_sys->bytestream,
 412                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 413             {
 414                 /* Need more data */
 415                 return NULL;
 416             }
 417             p_sys->i_state = STATE_SEND_DATA;
 418
 419         case STATE_SEND_DATA:
 420             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 421             {
 422                 //p_dec->b_error = VLC_TRUE;
 423                 return NULL;
 424             }
 425
 426             /* Free bitrate only */
 427             if( p_sys->i_bit_rate == 0 )
 428             {
 429                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 430             }
 431
 432             /* Copy the whole frame into the buffer. When we reach this point
 433              * we already know we have enough data available. */
 434             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 435
 436             /* Get beginning of next frame for libmad */
 437             if( !p_sys->b_packetizer )
 438             {
 439                 memcpy( p_buf + p_sys->i_frame_size,
 440                         p_header, MAD_BUFFER_GUARD );
 441             }
 442
 443             p_sys->i_state = STATE_NOSYNC;
 444
 445             /* Make sure we don't reuse the same pts twice */
 446             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 447                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 448
 449             /* So p_block doesn't get re-added several times */
 450             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 451
 452             return p_out_buffer;
 453         }
 454     }
 455
 456     return NULL;
 457 }
 458
 459 /*****************************************************************************
 460  * GetOutBuffer:
 461  *****************************************************************************/
 462 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 463 {
 464     decoder_sys_t *p_sys = p_dec->p_sys;
 465     uint8_t *p_buf;
 466
 467     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 468     {
 469         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 470                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 471
 472         aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 473         aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 474     }
 475
 476     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 477     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 478     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 479     p_dec->fmt_out.audio.i_bytes_per_frame =
 480         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 481
 482     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 483     p_dec->fmt_out.audio.i_physical_channels =
 484         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 485
 486     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 487
 488     if( p_sys->b_packetizer )
 489     {
 490         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 491         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 492         *pp_out_buffer = p_sout_buffer;
 493     }
 494     else
 495     {
 496         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 497         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 498         *pp_out_buffer = p_aout_buffer;
 499     }
 500
 501     return p_buf;
 502 }
 503
 504 /*****************************************************************************
 505  * GetAoutBuffer:
 506  *****************************************************************************/
 507 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 508 {
 509     decoder_sys_t *p_sys = p_dec->p_sys;
 510     aout_buffer_t *p_buf;
 511
 512     p_buf = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_frame_length );
 513     if( p_buf == NULL ) return NULL;
 514
 515     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 516     p_buf->end_date =
 517         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 518
 519     /* Hack for libmad filter */
 520     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 521
 522     return p_buf;
 523 }
 524
 525 /*****************************************************************************
 526  * GetSoutBuffer:
 527  *****************************************************************************/
 528 static block_t *GetSoutBuffer( decoder_t *p_dec )
 529 {
 530     decoder_sys_t *p_sys = p_dec->p_sys;
 531     block_t *p_block;
 532
 533     p_block = block_New( p_dec, p_sys->i_frame_size );
 534     if( p_block == NULL ) return NULL;
 535
 536     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 537
 538     p_block->i_length =
 539         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) -
 540             p_block->i_pts;
 541
 542     return p_block;
 543 }
 544
 545 /*****************************************************************************
 546  * CloseDecoder: clean up the decoder
 547  *****************************************************************************/
 548 static void CloseDecoder( vlc_object_t *p_this )
 549 {
 550     decoder_t *p_dec = (decoder_t *)p_this;
 551     decoder_sys_t *p_sys = p_dec->p_sys;
 552
 553     block_BytestreamRelease( &p_sys->bytestream );
 554
 555     free( p_sys );
 556 }
 557
 558 /*****************************************************************************
 559  * SyncInfo: parse MPEG audio sync info
 560  *****************************************************************************/
 561 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 562                      unsigned int * pi_channels_conf,
 563                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 564                      unsigned int * pi_frame_length,
 565                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 566 {
 567     static const int ppi_bitrate[2][3][16] =
 568     {
 569         {
 570             /* v1 l1 */
 571             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 572               416, 448, 0},
 573             /* v1 l2 */
 574             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 575               320, 384, 0},
 576             /* v1 l3 */
 577             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 578               256, 320, 0}
 579         },
 580
 581         {
 582             /* v2 l1 */
 583             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 584               224, 256, 0},
 585             /* v2 l2 */
 586             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 587               144, 160, 0},
 588             /* v2 l3 */
 589             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 590               144, 160, 0}
 591         }
 592     };
 593
 594     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 595     {
 596         { 44100, 48000, 32000, 0 },
 597         { 22050, 24000, 16000, 0 }
 598     };
 599
 600     int i_version, i_mode, i_emphasis;
 601     vlc_bool_t b_padding, b_mpeg_2_5, b_crc;
 602     int i_frame_size = 0;
 603     int i_bitrate_index, i_samplerate_index;
 604     int i_max_bit_rate;
 605
 606     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 607     i_version   = 1 - ((i_header & 0x80000) >> 19);
 608     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 609     b_crc = !((i_header >> 16) & 0x01);
 610     i_bitrate_index = (i_header & 0xf000) >> 12;
 611     i_samplerate_index = (i_header & 0xc00) >> 10;
 612     b_padding   = (i_header & 0x200) >> 9;
 613     /* Extension */
 614     i_mode      = (i_header & 0xc0) >> 6;
 615     /* Modeext, copyright & original */
 616     i_emphasis  = i_header & 0x3;
 617
 618     if( *pi_layer != 4 &&
 619         i_bitrate_index < 0x0f &&
 620         i_samplerate_index != 0x03 &&
 621         i_emphasis != 0x02 )
 622     {
 623         switch ( i_mode )
 624         {
 625         case 0: /* stereo */
 626         case 1: /* joint stereo */
 627             *pi_channels = 2;
 628             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 629             break;
 630         case 2: /* dual-mono */
 631             *pi_channels = 2;
 632             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 633                                 | AOUT_CHAN_DUALMONO;
 634             break;
 635         case 3: /* mono */
 636             *pi_channels = 1;
 637             *pi_channels_conf = AOUT_CHAN_CENTER;
 638             break;
 639         }
 640         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 641         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 642         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 643
 644         if ( b_mpeg_2_5 )
 645         {
 646             *pi_sample_rate >>= 1;
 647         }
 648
 649         switch( *pi_layer )
 650         {
 651         case 1:
 652             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 653                            b_padding ) * 4;
 654             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 655                                  *pi_sample_rate + 1 ) * 4;
 656             *pi_frame_length = 384;
 657             break;
 658
 659         case 2:
 660             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 661             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 662             *pi_frame_length = 1152;
 663             break;
 664
 665         case 3:
 666             i_frame_size = ( i_version ? 72000 : 144000 ) *
 667                            *pi_bit_rate / *pi_sample_rate + b_padding;
 668             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 669                                  i_max_bit_rate / *pi_sample_rate + 1;
 670             *pi_frame_length = i_version ? 576 : 1152;
 671             break;
 672
 673         default:
 674             break;
 675         }
 676     }
 677     else
 678     {
 679         return -1;
 680     }
 681
 682     return i_frame_size;
 683 }