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: mpeg_audio.c,v 1.25 2004/01/25 18:20:12 bigben Exp $
   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_capability( "decoder", 100 );
 108     set_callbacks( OpenDecoder, CloseDecoder );
 109
 110     add_submodule();
 111     set_description( _("MPEG audio layer I/II/III packetizer") );
 112     set_capability( "packetizer", 10 );
 113     set_callbacks( OpenPacketizer, CloseDecoder );
 114 vlc_module_end();
 115
 116 /*****************************************************************************
 117  * OpenDecoder: probe the decoder and return score
 118  *****************************************************************************/
 119 static int OpenDecoder( vlc_object_t *p_this )
 120 {
 121     decoder_t *p_dec = (decoder_t*)p_this;
 122     decoder_sys_t *p_sys;
 123
 124     if( p_dec->fmt_in.i_codec != VLC_FOURCC('m','p','g','a') )
 125     {
 126         return VLC_EGENERIC;
 127     }
 128
 129     /* Allocate the memory needed to store the decoder's structure */
 130     if( ( p_dec->p_sys = p_sys =
 131           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 132     {
 133         msg_Err( p_dec, "out of memory" );
 134         return VLC_EGENERIC;
 135     }
 136
 137     /* Misc init */
 138     p_sys->b_packetizer = VLC_FALSE;
 139     p_sys->i_state = STATE_NOSYNC;
 140     aout_DateSet( &p_sys->end_date, 0 );
 141     p_sys->bytestream = block_BytestreamInit( p_dec );
 142
 143     /* Set output properties */
 144     p_dec->fmt_out.i_cat = AUDIO_ES;
 145     p_dec->fmt_out.i_codec = VLC_FOURCC('m','p','g','a');
 146
 147     /* Set callback */
 148     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 149         DecodeBlock;
 150     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 151         DecodeBlock;
 152
 153     /* Start with the minimum size for a free bitrate frame */
 154     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 155
 156     return VLC_SUCCESS;
 157 }
 158
 159 static int OpenPacketizer( vlc_object_t *p_this )
 160 {
 161     decoder_t *p_dec = (decoder_t*)p_this;
 162
 163     int i_ret = OpenDecoder( p_this );
 164
 165     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = VLC_TRUE;
 166
 167     return i_ret;
 168 }
 169
 170 /****************************************************************************
 171  * DecodeBlock: the whole thing
 172  ****************************************************************************
 173  * This function is called just after the thread is launched.
 174  ****************************************************************************/
 175 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 176 {
 177     decoder_sys_t *p_sys = p_dec->p_sys;
 178     uint8_t p_header[MAD_BUFFER_GUARD];
 179     uint32_t i_header;
 180     uint8_t *p_buf;
 181     void *p_out_buffer;
 182
 183     if( !pp_block || !*pp_block ) return NULL;
 184
 185     if( !aout_DateGet( &p_sys->end_date ) && !(*pp_block)->i_pts )
 186     {
 187         /* We've just started the stream, wait for the first PTS. */
 188         block_Release( *pp_block );
 189         return NULL;
 190     }
 191
 192     if( (*pp_block)->b_discontinuity )
 193     {
 194         p_sys->i_state = STATE_NOSYNC;
 195     }
 196
 197     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 198
 199     while( 1 )
 200     {
 201         switch( p_sys->i_state )
 202         {
 203
 204         case STATE_NOSYNC:
 205             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 206                    == VLC_SUCCESS )
 207             {
 208                 /* Look for sync word - should be 0xffe */
 209                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 210                 {
 211                     p_sys->i_state = STATE_SYNC;
 212                     break;
 213                 }
 214                 block_SkipByte( &p_sys->bytestream );
 215             }
 216             if( p_sys->i_state != STATE_SYNC )
 217             {
 218                 block_BytestreamFlush( &p_sys->bytestream );
 219
 220                 /* Need more data */
 221                 return NULL;
 222             }
 223
 224         case STATE_SYNC:
 225             /* New frame, set the Presentation Time Stamp */
 226             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 227             if( p_sys->i_pts != 0 &&
 228                 p_sys->i_pts != aout_DateGet( &p_sys->end_date ) )
 229             {
 230                 aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 231             }
 232             p_sys->i_state = STATE_HEADER;
 233
 234         case STATE_HEADER:
 235             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 236             if( block_PeekBytes( &p_sys->bytestream, p_header,
 237                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 238             {
 239                 /* Need more data */
 240                 return NULL;
 241             }
 242
 243             /* Build frame header */
 244             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 245                        |p_header[3];
 246
 247             /* Check if frame is valid and get frame info */
 248             p_sys->i_frame_size = SyncInfo( i_header,
 249                                             &p_sys->i_channels,
 250                                             &p_sys->i_channels_conf,
 251                                             &p_sys->i_rate,
 252                                             &p_sys->i_bit_rate,
 253                                             &p_sys->i_frame_length,
 254                                             &p_sys->i_max_frame_size,
 255                                             &p_sys->i_layer );
 256
 257             if( p_sys->i_frame_size == -1 )
 258             {
 259                 msg_Dbg( p_dec, "emulated startcode" );
 260                 block_SkipByte( &p_sys->bytestream );
 261                 p_sys->i_state = STATE_NOSYNC;
 262                 break;
 263             }
 264
 265             if( p_sys->i_bit_rate == 0 )
 266             {
 267                 /* Free birate, but 99% emulated startcode :( */
 268                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 269                 {
 270                     msg_Dbg( p_dec, "free bitrate mode");
 271                 }
 272                 p_sys->i_frame_size = p_sys->i_free_frame_size;
 273             }
 274
 275             p_sys->i_state = STATE_NEXT_SYNC;
 276
 277         case STATE_NEXT_SYNC:
 278             /* TODO: If p_block == NULL, flush the buffer without checking the
 279              * next sync word */
 280
 281             /* Check if next expected frame contains the sync word */
 282             if( block_PeekOffsetBytes( &p_sys->bytestream,
 283                                        p_sys->i_frame_size, p_header,
 284                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 285             {
 286                 /* Need more data */
 287                 return NULL;
 288             }
 289
 290             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 291             {
 292                 /* Startcode is fine, let's try the header as an extra check */
 293                 int i_next_frame_size;
 294                 unsigned int i_next_channels, i_next_channels_conf;
 295                 unsigned int i_next_rate, i_next_bit_rate;
 296                 unsigned int i_next_frame_length, i_next_max_frame_size;
 297                 unsigned int i_next_layer;
 298
 299                 /* Build frame header */
 300                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 301                            |p_header[3];
 302
 303                 i_next_frame_size = SyncInfo( i_header,
 304                                               &i_next_channels,
 305                                               &i_next_channels_conf,
 306                                               &i_next_rate,
 307                                               &i_next_bit_rate,
 308                                               &i_next_frame_length,
 309                                               &i_next_max_frame_size,
 310                                               &i_next_layer );
 311
 312                 /* Free bitrate only */
 313                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 314                 {
 315                     if( (unsigned int)p_sys->i_frame_size >
 316                         p_sys->i_max_frame_size )
 317                     {
 318                         msg_Dbg( p_dec, "frame too big %d > %d "
 319                                  "(emulated startcode ?)", p_sys->i_frame_size,
 320                                  p_sys->i_max_frame_size );
 321                         block_SkipByte( &p_sys->bytestream );
 322                         p_sys->i_state = STATE_NOSYNC;
 323                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 324                         break;
 325                     }
 326
 327                     p_sys->i_frame_size++;
 328                     break;
 329                 }
 330
 331                 if( i_next_frame_size == -1 )
 332                 {
 333                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 334                     block_SkipByte( &p_sys->bytestream );
 335                     p_sys->i_state = STATE_NOSYNC;
 336                     break;
 337                 }
 338
 339                 /* Check info is in sync with previous one */
 340                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 341                     i_next_rate != p_sys->i_rate ||
 342                     i_next_layer != p_sys->i_layer ||
 343                     i_next_frame_length != p_sys->i_frame_length )
 344                 {
 345                     /* Free bitrate only */
 346                     if( p_sys->i_bit_rate == 0 )
 347                     {
 348                         p_sys->i_frame_size++;
 349                         break;
 350                     }
 351
 352                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 353                              "(emulated startcode ?)" );
 354                     block_SkipByte( &p_sys->bytestream );
 355                     p_sys->i_state = STATE_NOSYNC;
 356                     break;
 357                 }
 358
 359                 /* Free bitrate only */
 360                 if( p_sys->i_bit_rate == 0 )
 361                 {
 362                     if( i_next_bit_rate != 0 )
 363                     {
 364                         p_sys->i_frame_size++;
 365                         break;
 366                     }
 367                 }
 368
 369             }
 370             else
 371             {
 372                 /* Free bitrate only */
 373                 if( p_sys->i_bit_rate == 0 )
 374                 {
 375                     if( (unsigned int)p_sys->i_frame_size >
 376                         p_sys->i_max_frame_size )
 377                     {
 378                         msg_Dbg( p_dec, "frame too big %d > %d "
 379                                  "(emulated startcode ?)", p_sys->i_frame_size,
 380                                  p_sys->i_max_frame_size );
 381                         block_SkipByte( &p_sys->bytestream );
 382                         p_sys->i_state = STATE_NOSYNC;
 383                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 384                         break;
 385                     }
 386
 387                     p_sys->i_frame_size++;
 388                     break;
 389                 }
 390
 391                 msg_Dbg( p_dec, "emulated startcode "
 392                          "(no startcode on following frame)" );
 393                 p_sys->i_state = STATE_NOSYNC;
 394                 block_SkipByte( &p_sys->bytestream );
 395                 break;
 396             }
 397
 398             p_sys->i_state = STATE_SEND_DATA;
 399             break;
 400
 401         case STATE_GET_DATA:
 402             /* Make sure we have enough data.
 403              * (Not useful if we went through NEXT_SYNC) */
 404             if( block_WaitBytes( &p_sys->bytestream,
 405                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 406             {
 407                 /* Need more data */
 408                 return NULL;
 409             }
 410             p_sys->i_state = STATE_SEND_DATA;
 411
 412         case STATE_SEND_DATA:
 413             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 414             {
 415                 //p_dec->b_error = VLC_TRUE;
 416                 return NULL;
 417             }
 418
 419             /* Free bitrate only */
 420             if( p_sys->i_bit_rate == 0 )
 421             {
 422                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 423             }
 424
 425             /* Copy the whole frame into the buffer. When we reach this point
 426              * we already know we have enough data available. */
 427             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 428
 429             /* Get beginning of next frame for libmad */
 430             if( !p_sys->b_packetizer )
 431             {
 432                 memcpy( p_buf + p_sys->i_frame_size,
 433                         p_header, MAD_BUFFER_GUARD );
 434             }
 435
 436             p_sys->i_state = STATE_NOSYNC;
 437
 438             /* Make sure we don't reuse the same pts twice */
 439             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 440                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = 0;
 441
 442             /* So p_block doesn't get re-added several times */
 443             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 444
 445             return p_out_buffer;
 446         }
 447     }
 448
 449     return NULL;
 450 }
 451
 452 /*****************************************************************************
 453  * GetOutBuffer:
 454  *****************************************************************************/
 455 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 456 {
 457     decoder_sys_t *p_sys = p_dec->p_sys;
 458     uint8_t *p_buf;
 459
 460     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 461     {
 462         msg_Info( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 463                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 464
 465         aout_DateInit( &p_sys->end_date, p_sys->i_rate );
 466         aout_DateSet( &p_sys->end_date, p_sys->i_pts );
 467     }
 468
 469     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 470     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 471     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 472     p_dec->fmt_out.audio.i_bytes_per_frame =
 473         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 474
 475     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 476     p_dec->fmt_out.audio.i_physical_channels =
 477         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 478
 479     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate;
 480
 481     if( p_sys->b_packetizer )
 482     {
 483         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 484         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 485         *pp_out_buffer = p_sout_buffer;
 486     }
 487     else
 488     {
 489         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 490         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 491         *pp_out_buffer = p_aout_buffer;
 492     }
 493
 494     return p_buf;
 495 }
 496
 497 /*****************************************************************************
 498  * GetAoutBuffer:
 499  *****************************************************************************/
 500 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 501 {
 502     decoder_sys_t *p_sys = p_dec->p_sys;
 503     aout_buffer_t *p_buf;
 504
 505     p_buf = p_dec->pf_aout_buffer_new( p_dec, p_sys->i_frame_length );
 506     if( p_buf == NULL ) return NULL;
 507
 508     p_buf->start_date = aout_DateGet( &p_sys->end_date );
 509     p_buf->end_date =
 510         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length );
 511
 512     /* Hack for libmad filter */
 513     p_buf->i_nb_bytes = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 514
 515     return p_buf;
 516 }
 517
 518 /*****************************************************************************
 519  * GetSoutBuffer:
 520  *****************************************************************************/
 521 static block_t *GetSoutBuffer( decoder_t *p_dec )
 522 {
 523     decoder_sys_t *p_sys = p_dec->p_sys;
 524     block_t *p_block;
 525
 526     p_block = block_New( p_dec, p_sys->i_frame_size );
 527     if( p_block == NULL ) return NULL;
 528
 529     p_block->i_pts = p_block->i_dts = aout_DateGet( &p_sys->end_date );
 530
 531     p_block->i_length =
 532         aout_DateIncrement( &p_sys->end_date, p_sys->i_frame_length ) -
 533             p_block->i_pts;
 534
 535     return p_block;
 536 }
 537
 538 /*****************************************************************************
 539  * CloseDecoder: clean up the decoder
 540  *****************************************************************************/
 541 static void CloseDecoder( vlc_object_t *p_this )
 542 {
 543     decoder_t *p_dec = (decoder_t *)p_this;
 544     decoder_sys_t *p_sys = p_dec->p_sys;
 545
 546     block_BytestreamRelease( &p_sys->bytestream );
 547
 548     free( p_sys );
 549 }
 550
 551 /*****************************************************************************
 552  * SyncInfo: parse MPEG audio sync info
 553  *****************************************************************************/
 554 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 555                      unsigned int * pi_channels_conf,
 556                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 557                      unsigned int * pi_frame_length,
 558                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 559 {
 560     static const int ppi_bitrate[2][3][16] =
 561     {
 562         {
 563             /* v1 l1 */
 564             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 565               416, 448, 0},
 566             /* v1 l2 */
 567             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 568               320, 384, 0},
 569             /* v1 l3 */
 570             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 571               256, 320, 0}
 572         },
 573
 574         {
 575             /* v2 l1 */
 576             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 577               224, 256, 0},
 578             /* v2 l2 */
 579             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 580               144, 160, 0},
 581             /* v2 l3 */
 582             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 583               144, 160, 0}
 584         }
 585     };
 586
 587     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 588     {
 589         { 44100, 48000, 32000, 0 },
 590         { 22050, 24000, 16000, 0 }
 591     };
 592
 593     int i_version, i_mode, i_emphasis;
 594     vlc_bool_t b_padding, b_mpeg_2_5, b_crc;
 595     int i_frame_size = 0;
 596     int i_bitrate_index, i_samplerate_index;
 597     int i_max_bit_rate;
 598
 599     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 600     i_version   = 1 - ((i_header & 0x80000) >> 19);
 601     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 602     b_crc = !((i_header >> 16) & 0x01);
 603     i_bitrate_index = (i_header & 0xf000) >> 12;
 604     i_samplerate_index = (i_header & 0xc00) >> 10;
 605     b_padding   = (i_header & 0x200) >> 9;
 606     /* Extension */
 607     i_mode      = (i_header & 0xc0) >> 6;
 608     /* Modeext, copyright & original */
 609     i_emphasis  = i_header & 0x3;
 610
 611     if( *pi_layer != 4 &&
 612         i_bitrate_index < 0x0f &&
 613         i_samplerate_index != 0x03 &&
 614         i_emphasis != 0x02 )
 615     {
 616         switch ( i_mode )
 617         {
 618         case 0: /* stereo */
 619         case 1: /* joint stereo */
 620             *pi_channels = 2;
 621             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 622             break;
 623         case 2: /* dual-mono */
 624             *pi_channels = 2;
 625             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 626                                 | AOUT_CHAN_DUALMONO;
 627             break;
 628         case 3: /* mono */
 629             *pi_channels = 1;
 630             *pi_channels_conf = AOUT_CHAN_CENTER;
 631             break;
 632         }
 633         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 634         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 635         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 636
 637         if ( b_mpeg_2_5 )
 638         {
 639             *pi_sample_rate >>= 1;
 640         }
 641
 642         switch( *pi_layer )
 643         {
 644         case 1:
 645             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 646                            b_padding ) * 4;
 647             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 648                                  *pi_sample_rate + 1 ) * 4;
 649             *pi_frame_length = 384;
 650             break;
 651
 652         case 2:
 653             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 654             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 655             *pi_frame_length = 1152;
 656             break;
 657
 658         case 3:
 659             i_frame_size = ( i_version ? 72000 : 144000 ) *
 660                            *pi_bit_rate / *pi_sample_rate + b_padding;
 661             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 662                                  i_max_bit_rate / *pi_sample_rate + 1;
 663             *pi_frame_length = i_version ? 576 : 1152;
 664             break;
 665
 666         default:
 667             break;
 668         }
 669     }
 670     else
 671     {
 672         return -1;
 673     }
 674
 675     return i_frame_size;
 676 }