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     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_CODEC_MPGA )
 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     date_Set( &p_sys->end_date, 0 );
 151     p_sys->bytestream = block_BytestreamInit();
 152     p_sys->i_pts = VLC_TS_INVALID;
 153     p_sys->b_discontinuity = false;
 154
 155     /* Set output properties */
 156     p_dec->fmt_out.i_cat = AUDIO_ES;
 157     p_dec->fmt_out.i_codec = VLC_CODEC_MPGA;
 158     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 159
 160     /* Set callback */
 161     p_dec->pf_decode_audio = (aout_buffer_t *(*)(decoder_t *, block_t **))
 162         DecodeBlock;
 163     p_dec->pf_packetize    = (block_t *(*)(decoder_t *, block_t **))
 164         DecodeBlock;
 165
 166     /* Start with the minimum size for a free bitrate frame */
 167     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 168
 169     return VLC_SUCCESS;
 170 }
 171
 172 static int OpenDecoder( vlc_object_t *p_this )
 173 {
 174     /* HACK: Don't use this codec if we don't have an mpga audio filter */
 175     if( !module_exists( "mpgatofixed32" ) )
 176         return VLC_EGENERIC;
 177
 178     return Open( p_this );
 179 }
 180
 181 static int OpenPacketizer( vlc_object_t *p_this )
 182 {
 183     decoder_t *p_dec = (decoder_t*)p_this;
 184
 185     int i_ret = Open( p_this );
 186
 187     if( i_ret == VLC_SUCCESS ) p_dec->p_sys->b_packetizer = true;
 188
 189     return i_ret;
 190 }
 191
 192 /****************************************************************************
 193  * DecodeBlock: the whole thing
 194  ****************************************************************************
 195  * This function is called just after the thread is launched.
 196  ****************************************************************************/
 197 static void *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 198 {
 199     decoder_sys_t *p_sys = p_dec->p_sys;
 200     uint8_t p_header[MAD_BUFFER_GUARD];
 201     uint32_t i_header;
 202     uint8_t *p_buf;
 203     void *p_out_buffer;
 204
 205     if( !pp_block || !*pp_block ) return NULL;
 206
 207     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 208     {
 209         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 210         {
 211             p_sys->i_state = STATE_NOSYNC;
 212             block_BytestreamEmpty( &p_sys->bytestream );
 213         }
 214         date_Set( &p_sys->end_date, 0 );
 215         block_Release( *pp_block );
 216         p_sys->b_discontinuity = true;
 217         return NULL;
 218     }
 219
 220     if( !date_Get( &p_sys->end_date ) && (*pp_block)->i_pts <= VLC_TS_INVALID )
 221     {
 222         /* We've just started the stream, wait for the first PTS. */
 223         msg_Dbg( p_dec, "waiting for PTS" );
 224         block_Release( *pp_block );
 225         return NULL;
 226     }
 227
 228     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 229
 230     while( 1 )
 231     {
 232         switch( p_sys->i_state )
 233         {
 234
 235         case STATE_NOSYNC:
 236             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 237                    == VLC_SUCCESS )
 238             {
 239                 /* Look for sync word - should be 0xffe */
 240                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 241                 {
 242                     p_sys->i_state = STATE_SYNC;
 243                     break;
 244                 }
 245                 block_SkipByte( &p_sys->bytestream );
 246             }
 247             if( p_sys->i_state != STATE_SYNC )
 248             {
 249                 block_BytestreamFlush( &p_sys->bytestream );
 250
 251                 /* Need more data */
 252                 return NULL;
 253             }
 254
 255         case STATE_SYNC:
 256             /* New frame, set the Presentation Time Stamp */
 257             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 258             if( p_sys->i_pts > VLC_TS_INVALID &&
 259                 p_sys->i_pts != date_Get( &p_sys->end_date ) )
 260             {
 261                 date_Set( &p_sys->end_date, p_sys->i_pts );
 262             }
 263             p_sys->i_state = STATE_HEADER;
 264
 265         case STATE_HEADER:
 266             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 267             if( block_PeekBytes( &p_sys->bytestream, p_header,
 268                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 269             {
 270                 /* Need more data */
 271                 return NULL;
 272             }
 273
 274             /* Build frame header */
 275             i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 276                        |p_header[3];
 277
 278             /* Check if frame is valid and get frame info */
 279             p_sys->i_frame_size = SyncInfo( i_header,
 280                                             &p_sys->i_channels,
 281                                             &p_sys->i_channels_conf,
 282                                             &p_sys->i_rate,
 283                                             &p_sys->i_bit_rate,
 284                                             &p_sys->i_frame_length,
 285                                             &p_sys->i_max_frame_size,
 286                                             &p_sys->i_layer );
 287
 288             if( p_sys->i_frame_size == -1 )
 289             {
 290                 msg_Dbg( p_dec, "emulated startcode" );
 291                 block_SkipByte( &p_sys->bytestream );
 292                 p_sys->i_state = STATE_NOSYNC;
 293                 p_sys->b_discontinuity = true;
 294                 break;
 295             }
 296
 297             if( p_sys->i_bit_rate == 0 )
 298             {
 299                 /* Free bitrate, but 99% emulated startcode :( */
 300                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 301                 {
 302                     msg_Dbg( p_dec, "free bitrate mode");
 303                 }
 304                 /* The -1 below is to account for the frame padding */
 305                 p_sys->i_frame_size = p_sys->i_free_frame_size - 1;
 306             }
 307
 308             p_sys->i_state = STATE_NEXT_SYNC;
 309
 310         case STATE_NEXT_SYNC:
 311             /* TODO: If p_block == NULL, flush the buffer without checking the
 312              * next sync word */
 313
 314             /* Check if next expected frame contains the sync word */
 315             if( block_PeekOffsetBytes( &p_sys->bytestream,
 316                                        p_sys->i_frame_size, p_header,
 317                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 318             {
 319                 /* Need more data */
 320                 return NULL;
 321             }
 322
 323             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 324             {
 325                 /* Startcode is fine, let's try the header as an extra check */
 326                 int i_next_frame_size;
 327                 unsigned int i_next_channels, i_next_channels_conf;
 328                 unsigned int i_next_rate, i_next_bit_rate;
 329                 unsigned int i_next_frame_length, i_next_max_frame_size;
 330                 unsigned int i_next_layer;
 331
 332                 /* Build frame header */
 333                 i_header = (p_header[0]<<24)|(p_header[1]<<16)|(p_header[2]<<8)
 334                            |p_header[3];
 335
 336                 i_next_frame_size = SyncInfo( i_header,
 337                                               &i_next_channels,
 338                                               &i_next_channels_conf,
 339                                               &i_next_rate,
 340                                               &i_next_bit_rate,
 341                                               &i_next_frame_length,
 342                                               &i_next_max_frame_size,
 343                                               &i_next_layer );
 344
 345                 /* Free bitrate only */
 346                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 347                 {
 348                     if( (unsigned int)p_sys->i_frame_size >
 349                         p_sys->i_max_frame_size )
 350                     {
 351                         msg_Dbg( p_dec, "frame too big %d > %d "
 352                                  "(emulated startcode ?)", p_sys->i_frame_size,
 353                                  p_sys->i_max_frame_size );
 354                         block_SkipByte( &p_sys->bytestream );
 355                         p_sys->i_state = STATE_NOSYNC;
 356                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 357                         break;
 358                     }
 359
 360                     p_sys->i_frame_size++;
 361                     break;
 362                 }
 363
 364                 if( i_next_frame_size == -1 )
 365                 {
 366                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 367                     block_SkipByte( &p_sys->bytestream );
 368                     p_sys->i_state = STATE_NOSYNC;
 369                     p_sys->b_discontinuity = true;
 370                     break;
 371                 }
 372
 373                 /* Check info is in sync with previous one */
 374                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 375                     i_next_rate != p_sys->i_rate ||
 376                     i_next_layer != p_sys->i_layer ||
 377                     i_next_frame_length != p_sys->i_frame_length )
 378                 {
 379                     /* Free bitrate only */
 380                     if( p_sys->i_bit_rate == 0 )
 381                     {
 382                         p_sys->i_frame_size++;
 383                         break;
 384                     }
 385
 386                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 387                              "(emulated startcode ?)" );
 388                     block_SkipByte( &p_sys->bytestream );
 389                     p_sys->i_state = STATE_NOSYNC;
 390                     break;
 391                 }
 392
 393                 /* Free bitrate only */
 394                 if( p_sys->i_bit_rate == 0 )
 395                 {
 396                     if( i_next_bit_rate != 0 )
 397                     {
 398                         p_sys->i_frame_size++;
 399                         break;
 400                     }
 401                 }
 402
 403             }
 404             else
 405             {
 406                 /* Free bitrate only */
 407                 if( p_sys->i_bit_rate == 0 )
 408                 {
 409                     if( (unsigned int)p_sys->i_frame_size >
 410                         p_sys->i_max_frame_size )
 411                     {
 412                         msg_Dbg( p_dec, "frame too big %d > %d "
 413                                  "(emulated startcode ?)", p_sys->i_frame_size,
 414                                  p_sys->i_max_frame_size );
 415                         block_SkipByte( &p_sys->bytestream );
 416                         p_sys->i_state = STATE_NOSYNC;
 417                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 418                         break;
 419                     }
 420
 421                     p_sys->i_frame_size++;
 422                     break;
 423                 }
 424
 425                 msg_Dbg( p_dec, "emulated startcode "
 426                          "(no startcode on following frame)" );
 427                 p_sys->i_state = STATE_NOSYNC;
 428                 block_SkipByte( &p_sys->bytestream );
 429                 break;
 430             }
 431
 432             p_sys->i_state = STATE_SEND_DATA;
 433             break;
 434
 435         case STATE_GET_DATA:
 436             /* Make sure we have enough data.
 437              * (Not useful if we went through NEXT_SYNC) */
 438             if( block_WaitBytes( &p_sys->bytestream,
 439                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 440             {
 441                 /* Need more data */
 442                 return NULL;
 443             }
 444             p_sys->i_state = STATE_SEND_DATA;
 445
 446         case STATE_SEND_DATA:
 447             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 448             {
 449                 //p_dec->b_error = true;
 450                 return NULL;
 451             }
 452
 453             /* Free bitrate only */
 454             if( p_sys->i_bit_rate == 0 )
 455             {
 456                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 457             }
 458
 459             /* Copy the whole frame into the buffer. When we reach this point
 460              * we already know we have enough data available. */
 461             block_GetBytes( &p_sys->bytestream, p_buf, p_sys->i_frame_size );
 462
 463             /* Get beginning of next frame for libmad */
 464             if( !p_sys->b_packetizer )
 465             {
 466                 memcpy( p_buf + p_sys->i_frame_size,
 467                         p_header, MAD_BUFFER_GUARD );
 468             }
 469
 470             p_sys->i_state = STATE_NOSYNC;
 471
 472             /* Make sure we don't reuse the same pts twice */
 473             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 474                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = VLC_TS_INVALID;
 475
 476             /* So p_block doesn't get re-added several times */
 477             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 478
 479             return p_out_buffer;
 480         }
 481     }
 482
 483     return NULL;
 484 }
 485
 486 /*****************************************************************************
 487  * GetOutBuffer:
 488  *****************************************************************************/
 489 static uint8_t *GetOutBuffer( decoder_t *p_dec, void **pp_out_buffer )
 490 {
 491     decoder_sys_t *p_sys = p_dec->p_sys;
 492     uint8_t *p_buf;
 493
 494     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate )
 495     {
 496         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 497                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 498
 499         date_Init( &p_sys->end_date, p_sys->i_rate, 1 );
 500         date_Set( &p_sys->end_date, p_sys->i_pts );
 501     }
 502
 503     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 504     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 505     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 506     p_dec->fmt_out.audio.i_bytes_per_frame =
 507         p_sys->i_max_frame_size + MAD_BUFFER_GUARD;
 508
 509     p_dec->fmt_out.audio.i_original_channels = p_sys->i_channels_conf;
 510     p_dec->fmt_out.audio.i_physical_channels =
 511         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 512
 513     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 514
 515     if( p_sys->b_packetizer )
 516     {
 517         block_t *p_sout_buffer = GetSoutBuffer( p_dec );
 518         p_buf = p_sout_buffer ? p_sout_buffer->p_buffer : NULL;
 519         *pp_out_buffer = p_sout_buffer;
 520     }
 521     else
 522     {
 523         aout_buffer_t *p_aout_buffer = GetAoutBuffer( p_dec );
 524         p_buf = p_aout_buffer ? p_aout_buffer->p_buffer : NULL;
 525         *pp_out_buffer = p_aout_buffer;
 526     }
 527
 528     return p_buf;
 529 }
 530
 531 /*****************************************************************************
 532  * GetAoutBuffer:
 533  *****************************************************************************/
 534 static aout_buffer_t *GetAoutBuffer( decoder_t *p_dec )
 535 {
 536     decoder_sys_t *p_sys = p_dec->p_sys;
 537     aout_buffer_t *p_buf;
 538
 539     p_buf = decoder_NewAudioBuffer( p_dec, p_sys->i_frame_length );
 540     if( p_buf == NULL ) return NULL;
 541
 542     p_buf->i_pts = date_Get( &p_sys->end_date );
 543     p_buf->i_length = date_Increment( &p_sys->end_date, p_sys->i_frame_length )
 544                       - p_buf->i_pts;
 545     if( p_sys->b_discontinuity )
 546         p_buf->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 547     p_sys->b_discontinuity = false;
 548
 549     /* Hack for libmad filter */
 550     p_buf->i_buffer = p_sys->i_frame_size + MAD_BUFFER_GUARD;
 551
 552     return p_buf;
 553 }
 554
 555 /*****************************************************************************
 556  * GetSoutBuffer:
 557  *****************************************************************************/
 558 static block_t *GetSoutBuffer( decoder_t *p_dec )
 559 {
 560     decoder_sys_t *p_sys = p_dec->p_sys;
 561     block_t *p_block;
 562
 563     p_block = block_New( p_dec, p_sys->i_frame_size );
 564     if( p_block == NULL ) return NULL;
 565
 566     p_block->i_pts = p_block->i_dts = date_Get( &p_sys->end_date );
 567
 568     p_block->i_length =
 569         date_Increment( &p_sys->end_date, p_sys->i_frame_length ) - p_block->i_pts;
 570
 571     return p_block;
 572 }
 573
 574 /*****************************************************************************
 575  * CloseDecoder: clean up the decoder
 576  *****************************************************************************/
 577 static void CloseDecoder( vlc_object_t *p_this )
 578 {
 579     decoder_t *p_dec = (decoder_t *)p_this;
 580     decoder_sys_t *p_sys = p_dec->p_sys;
 581
 582     block_BytestreamRelease( &p_sys->bytestream );
 583
 584     free( p_sys );
 585 }
 586
 587 /*****************************************************************************
 588  * SyncInfo: parse MPEG audio sync info
 589  *****************************************************************************/
 590 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 591                      unsigned int * pi_channels_conf,
 592                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 593                      unsigned int * pi_frame_length,
 594                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 595 {
 596     static const int ppi_bitrate[2][3][16] =
 597     {
 598         {
 599             /* v1 l1 */
 600             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 601               416, 448, 0},
 602             /* v1 l2 */
 603             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 604               320, 384, 0},
 605             /* v1 l3 */
 606             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 607               256, 320, 0}
 608         },
 609
 610         {
 611             /* v2 l1 */
 612             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 613               224, 256, 0},
 614             /* v2 l2 */
 615             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 616               144, 160, 0},
 617             /* v2 l3 */
 618             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 619               144, 160, 0}
 620         }
 621     };
 622
 623     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 624     {
 625         { 44100, 48000, 32000, 0 },
 626         { 22050, 24000, 16000, 0 }
 627     };
 628
 629     int i_version, i_mode, i_emphasis;
 630     bool b_padding, b_mpeg_2_5, b_crc;
 631     int i_frame_size = 0;
 632     int i_bitrate_index, i_samplerate_index;
 633     int i_max_bit_rate;
 634
 635     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 636     i_version   = 1 - ((i_header & 0x80000) >> 19);
 637     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 638     b_crc = !((i_header >> 16) & 0x01);
 639     i_bitrate_index = (i_header & 0xf000) >> 12;
 640     i_samplerate_index = (i_header & 0xc00) >> 10;
 641     b_padding   = (i_header & 0x200) >> 9;
 642     /* Extension */
 643     i_mode      = (i_header & 0xc0) >> 6;
 644     /* Modeext, copyright & original */
 645     i_emphasis  = i_header & 0x3;
 646
 647     if( *pi_layer != 4 &&
 648         i_bitrate_index < 0x0f &&
 649         i_samplerate_index != 0x03 &&
 650         i_emphasis != 0x02 )
 651     {
 652         switch ( i_mode )
 653         {
 654         case 0: /* stereo */
 655         case 1: /* joint stereo */
 656             *pi_channels = 2;
 657             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 658             break;
 659         case 2: /* dual-mono */
 660             *pi_channels = 2;
 661             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 662                                 | AOUT_CHAN_DUALMONO;
 663             break;
 664         case 3: /* mono */
 665             *pi_channels = 1;
 666             *pi_channels_conf = AOUT_CHAN_CENTER;
 667             break;
 668         }
 669         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 670         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 671         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 672
 673         if ( b_mpeg_2_5 )
 674         {
 675             *pi_sample_rate >>= 1;
 676         }
 677
 678         switch( *pi_layer )
 679         {
 680         case 1:
 681             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 682                            b_padding ) * 4;
 683             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 684                                  *pi_sample_rate + 1 ) * 4;
 685             *pi_frame_length = 384;
 686             break;
 687
 688         case 2:
 689             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 690             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 691             *pi_frame_length = 1152;
 692             break;
 693
 694         case 3:
 695             i_frame_size = ( i_version ? 72000 : 144000 ) *
 696                            *pi_bit_rate / *pi_sample_rate + b_padding;
 697             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 698                                  i_max_bit_rate / *pi_sample_rate + 1;
 699             *pi_frame_length = i_version ? 576 : 1152;
 700             break;
 701
 702         default:
 703             break;
 704         }
 705
 706         /* Free bitrate mode can support higher bitrates */
 707         if( !*pi_bit_rate ) *pi_max_frame_size *= 2;
 708     }
 709     else
 710     {
 711         return -1;
 712     }
 713
 714     return i_frame_size;
 715 }