modules/packetizer/mpegaudio.c

   1 /*****************************************************************************
   2  * mpegaudio.c: parse MPEG audio sync info and packetize the stream
   3  *****************************************************************************
   4  * Copyright (C) 2001-2016 VLC authors and VideoLAN
   5  *
   6  * Authors: Laurent Aimar <fenrir@via.ecp.fr>
   7  *          Eric Petit <titer@videolan.org>
   8  *          Christophe Massiot <massiot@via.ecp.fr>
   9  *          Gildas Bazin <gbazin@videolan.org>
  10  *
  11  * This program is free software; you can redistribute it and/or modify it
  12  * under the terms of the GNU Lesser General Public License as published by
  13  * the Free Software Foundation; either version 2.1 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  19  * GNU Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public License
  22  * along with this program; if not, write to the Free Software Foundation,
  23  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  24  *****************************************************************************/
  25
  26 /*****************************************************************************
  27  * Preamble
  28  *****************************************************************************/
  29 #ifdef HAVE_CONFIG_H
  30 # include "config.h"
  31 #endif
  32
  33 #include <vlc_common.h>
  34 #include <vlc_plugin.h>
  35 #include <vlc_codec.h>
  36 #include <vlc_aout.h>
  37 #include <vlc_modules.h>
  38 #include <assert.h>
  39
  40 #include <vlc_block_helper.h>
  41
  42 #include "packetizer_helper.h"
  43
  44 /*****************************************************************************
  45  * decoder_sys_t : decoder descriptor
  46  *****************************************************************************/
  47 typedef struct
  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
  61     vlc_tick_t i_pts;
  62
  63     int i_frame_size, i_free_frame_size;
  64     unsigned int i_channels_conf, i_chan_mode, i_channels;
  65     unsigned int i_rate, i_max_frame_size, i_frame_length;
  66     unsigned int i_layer, i_bit_rate;
  67
  68     bool   b_discontinuity;
  69 } decoder_sys_t;
  70
  71 #define MAD_BUFFER_GUARD 8
  72 #define MPGA_HEADER_SIZE 4
  73
  74 /****************************************************************************
  75  * Local prototypes
  76  ****************************************************************************/
  77
  78 static int  Open( vlc_object_t * );
  79 static void Close(  vlc_object_t * );
  80
  81 /*****************************************************************************
  82  * Module descriptor
  83  *****************************************************************************/
  84 vlc_module_begin ()
  85     set_category( CAT_INPUT )
  86     set_subcategory( SUBCAT_INPUT_ACODEC )
  87     set_description( N_("MPEG audio layer I/II/III packetizer") )
  88     set_capability( "packetizer", 10 )
  89     set_callbacks( Open, Close )
  90 vlc_module_end ()
  91
  92 /*****************************************************************************
  93  * Flush:
  94  *****************************************************************************/
  95 static void Flush( decoder_t *p_dec )
  96 {
  97     decoder_sys_t *p_sys = p_dec->p_sys;
  98
  99     date_Set( &p_sys->end_date, VLC_TICK_INVALID );
 100     p_sys->i_state = STATE_NOSYNC;
 101     block_BytestreamEmpty( &p_sys->bytestream );
 102     p_sys->b_discontinuity = true;
 103 }
 104
 105 /*****************************************************************************
 106  * GetOutBuffer:
 107  *****************************************************************************/
 108 static uint8_t *GetOutBuffer( decoder_t *p_dec, block_t **pp_out_buffer )
 109 {
 110     decoder_sys_t *p_sys = p_dec->p_sys;
 111
 112     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate ||
 113         date_Get( &p_sys->end_date ) == VLC_TICK_INVALID )
 114     {
 115         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 116                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 117
 118         if( p_sys->end_date.i_divider_num == 0 )
 119             date_Init( &p_sys->end_date, p_sys->i_rate, 1 );
 120         else
 121             date_Change( &p_sys->end_date, p_sys->i_rate, 1 );
 122         date_Set( &p_sys->end_date, p_sys->i_pts );
 123     }
 124
 125     p_dec->fmt_out.i_profile        = p_sys->i_layer;
 126     p_dec->fmt_out.audio.i_rate     = p_sys->i_rate;
 127     p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
 128     p_dec->fmt_out.audio.i_frame_length = p_sys->i_frame_length;
 129     p_dec->fmt_out.audio.i_bytes_per_frame = p_sys->i_max_frame_size;
 130
 131     p_dec->fmt_out.audio.i_physical_channels = p_sys->i_channels_conf;
 132     p_dec->fmt_out.audio.i_chan_mode = p_sys->i_chan_mode;
 133
 134     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 135
 136     block_t *p_block = block_Alloc( p_sys->i_frame_size );
 137     if( p_block == NULL )
 138         return NULL;
 139
 140     p_block->i_pts = p_block->i_dts = date_Get( &p_sys->end_date );
 141     p_block->i_length =
 142         date_Increment( &p_sys->end_date, p_sys->i_frame_length ) - p_block->i_pts;
 143
 144     *pp_out_buffer = p_block;
 145     return p_block->p_buffer;
 146 }
 147
 148 /*****************************************************************************
 149  * SyncInfo: parse MPEG audio sync info
 150  *****************************************************************************/
 151 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 152                      unsigned int * pi_channels_conf,
 153                      unsigned int * pi_chan_mode,
 154                      unsigned int * pi_sample_rate, unsigned int * pi_bit_rate,
 155                      unsigned int * pi_frame_length,
 156                      unsigned int * pi_max_frame_size, unsigned int * pi_layer)
 157 {
 158     static const int ppi_bitrate[2][3][16] =
 159     {
 160         {
 161             /* v1 l1 */
 162             { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384,
 163               416, 448, 0},
 164             /* v1 l2 */
 165             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256,
 166               320, 384, 0},
 167             /* v1 l3 */
 168             { 0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224,
 169               256, 320, 0}
 170         },
 171
 172         {
 173             /* v2 l1 */
 174             { 0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192,
 175               224, 256, 0},
 176             /* v2 l2 */
 177             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 178               144, 160, 0},
 179             /* v2 l3 */
 180             { 0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128,
 181               144, 160, 0}
 182         }
 183     };
 184
 185     static const int ppi_samplerate[2][4] = /* version 1 then 2 */
 186     {
 187         { 44100, 48000, 32000, 0 },
 188         { 22050, 24000, 16000, 0 }
 189     };
 190
 191     int i_version, i_mode, i_emphasis;
 192     bool b_padding, b_mpeg_2_5;
 193     int i_frame_size = 0;
 194     int i_bitrate_index, i_samplerate_index;
 195     int i_max_bit_rate;
 196
 197     b_mpeg_2_5  = 1 - ((i_header & 0x100000) >> 20);
 198     i_version   = 1 - ((i_header & 0x80000) >> 19);
 199     *pi_layer   = 4 - ((i_header & 0x60000) >> 17);
 200     //bool b_crc = !((i_header >> 16) & 0x01);
 201     i_bitrate_index = (i_header & 0xf000) >> 12;
 202     i_samplerate_index = (i_header & 0xc00) >> 10;
 203     b_padding   = (i_header & 0x200) >> 9;
 204     /* Extension */
 205     i_mode      = (i_header & 0xc0) >> 6;
 206     /* Modeext, copyright & original */
 207     i_emphasis  = i_header & 0x3;
 208     *pi_chan_mode = 0;
 209
 210     if( *pi_layer != 4 &&
 211         i_bitrate_index < 0x0f &&
 212         i_samplerate_index != 0x03 &&
 213         i_emphasis != 0x02 )
 214     {
 215         switch ( i_mode )
 216         {
 217         case 2: /* dual-mono */
 218             *pi_chan_mode = AOUT_CHANMODE_DUALMONO;
 219             /* fall through */
 220         case 0: /* stereo */
 221         case 1: /* joint stereo */
 222             *pi_channels = 2;
 223             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 224             break;
 225         case 3: /* mono */
 226             *pi_channels = 1;
 227             *pi_channels_conf = AOUT_CHAN_CENTER;
 228             break;
 229         }
 230         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 231         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 232         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 233
 234         if ( b_mpeg_2_5 )
 235         {
 236             *pi_sample_rate >>= 1;
 237         }
 238
 239         switch( *pi_layer )
 240         {
 241         case 1:
 242             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 243                            b_padding ) * 4;
 244             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 245                                  *pi_sample_rate + 1 ) * 4;
 246             *pi_frame_length = 384;
 247             break;
 248
 249         case 2:
 250             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 251             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 252             *pi_frame_length = 1152;
 253             break;
 254
 255         case 3:
 256             i_frame_size = ( i_version ? 72000 : 144000 ) *
 257                            *pi_bit_rate / *pi_sample_rate + b_padding;
 258             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 259                                  i_max_bit_rate / *pi_sample_rate + 1;
 260             *pi_frame_length = i_version ? 576 : 1152;
 261             break;
 262
 263         default:
 264             break;
 265         }
 266
 267         /* Free bitrate mode can support higher bitrates */
 268         if( !*pi_bit_rate ) *pi_max_frame_size *= 2;
 269     }
 270     else
 271     {
 272         return -1;
 273     }
 274
 275     return i_frame_size;
 276 }
 277
 278 /****************************************************************************
 279  * DecodeBlock: the whole thing
 280  ****************************************************************************
 281  * This function is called just after the thread is launched.
 282  ****************************************************************************/
 283 static block_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 284 {
 285     decoder_sys_t *p_sys = p_dec->p_sys;
 286     uint8_t p_header[MAD_BUFFER_GUARD];
 287     uint32_t i_header;
 288     uint8_t *p_buf;
 289     block_t *p_out_buffer;
 290
 291     block_t *p_block = pp_block ? *pp_block : NULL;
 292
 293     if (p_block)
 294     {
 295         if( p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 296         {
 297             /* First always drain complete blocks before discontinuity */
 298             block_t *p_drain = DecodeBlock( p_dec, NULL );
 299             if( p_drain )
 300                 return p_drain;
 301
 302             Flush( p_dec );
 303
 304             if( p_block->i_flags & BLOCK_FLAG_CORRUPTED )
 305             {
 306                 block_Release( p_block );
 307                 return NULL;
 308             }
 309         }
 310
 311         if( p_block->i_pts == VLC_TICK_INVALID &&
 312             date_Get( &p_sys->end_date ) == VLC_TICK_INVALID )
 313         {
 314             /* We've just started the stream, wait for the first PTS. */
 315             msg_Dbg( p_dec, "waiting for PTS" );
 316             block_Release( p_block );
 317             return NULL;
 318         }
 319
 320         block_BytestreamPush( &p_sys->bytestream, p_block );
 321     }
 322
 323     while( 1 )
 324     {
 325         switch( p_sys->i_state )
 326         {
 327
 328         case STATE_NOSYNC:
 329             while( block_PeekBytes( &p_sys->bytestream, p_header, 2 )
 330                    == VLC_SUCCESS )
 331             {
 332                 /* Look for sync word - should be 0xffe */
 333                 if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 334                 {
 335                     p_sys->i_state = STATE_SYNC;
 336                     break;
 337                 }
 338                 block_SkipByte( &p_sys->bytestream );
 339             }
 340             if( p_sys->i_state != STATE_SYNC )
 341             {
 342                 block_BytestreamFlush( &p_sys->bytestream );
 343
 344                 /* Need more data */
 345                 return NULL;
 346             }
 347             /* fallthrough */
 348
 349         case STATE_SYNC:
 350             /* New frame, set the Presentation Time Stamp */
 351             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 352             if( p_sys->i_pts != VLC_TICK_INVALID &&
 353                 p_sys->i_pts != date_Get( &p_sys->end_date ) )
 354             {
 355                 if( p_dec->fmt_in.i_original_fourcc == VLC_FOURCC( 'D','V','R',' ') )
 356                 {
 357                     if( date_Get( &p_sys->end_date ) == VLC_TICK_INVALID )
 358                         date_Set( &p_sys->end_date, p_sys->i_pts );
 359                 }
 360                 else if ( p_sys->i_pts != date_Get( &p_sys->end_date ) )
 361                 {
 362                     date_Set( &p_sys->end_date, p_sys->i_pts );
 363                 }
 364             }
 365             p_sys->i_state = STATE_HEADER;
 366             /* fallthrough */
 367
 368         case STATE_HEADER:
 369             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 370             if( block_PeekBytes( &p_sys->bytestream, p_header,
 371                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 372             {
 373                 /* Need more data */
 374                 return NULL;
 375             }
 376
 377             /* Build frame header */
 378             i_header = GetDWBE(p_header);
 379
 380             /* Check if frame is valid and get frame info */
 381             p_sys->i_frame_size = SyncInfo( i_header,
 382                                             &p_sys->i_channels,
 383                                             &p_sys->i_channels_conf,
 384                                             &p_sys->i_chan_mode,
 385                                             &p_sys->i_rate,
 386                                             &p_sys->i_bit_rate,
 387                                             &p_sys->i_frame_length,
 388                                             &p_sys->i_max_frame_size,
 389                                             &p_sys->i_layer );
 390
 391             if( p_sys->i_frame_size == -1 )
 392             {
 393                 msg_Dbg( p_dec, "emulated startcode" );
 394                 block_SkipByte( &p_sys->bytestream );
 395                 p_sys->i_state = STATE_NOSYNC;
 396                 break;
 397             }
 398
 399             if( p_sys->i_bit_rate == 0 )
 400             {
 401                 /* Free bitrate, but 99% emulated startcode :( */
 402                 if( p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 403                 {
 404                     msg_Dbg( p_dec, "free bitrate mode");
 405                 }
 406                 /* The -1 below is to account for the frame padding */
 407                 p_sys->i_frame_size = p_sys->i_free_frame_size - 1;
 408             }
 409
 410             p_sys->i_state = STATE_NEXT_SYNC;
 411             /* fallthrough */
 412
 413         case STATE_NEXT_SYNC:
 414             /* Check if next expected frame contains the sync word */
 415             if( block_PeekOffsetBytes( &p_sys->bytestream,
 416                                        p_sys->i_frame_size, p_header,
 417                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 418             {
 419                 if( p_block == NULL ) /* drain */
 420                 {
 421                     p_sys->i_state = STATE_SEND_DATA;
 422                     break;
 423                 }
 424                 /* Need more data */
 425                 return NULL;
 426             }
 427
 428             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 429             {
 430                 /* Startcode is fine, let's try the header as an extra check */
 431                 int i_next_frame_size;
 432                 unsigned int i_next_channels, i_next_stereo_mode, i_next_channels_conf;
 433                 unsigned int i_next_rate, i_next_bit_rate;
 434                 unsigned int i_next_frame_length, i_next_max_frame_size;
 435                 unsigned int i_next_layer;
 436
 437                 /* Build frame header */
 438                 i_header = GetDWBE(p_header);
 439
 440                 i_next_frame_size = SyncInfo( i_header,
 441                                               &i_next_channels,
 442                                               &i_next_channels_conf,
 443                                               &i_next_stereo_mode,
 444                                               &i_next_rate,
 445                                               &i_next_bit_rate,
 446                                               &i_next_frame_length,
 447                                               &i_next_max_frame_size,
 448                                               &i_next_layer );
 449
 450                 /* Free bitrate only */
 451                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 452                 {
 453                     if( (unsigned int)p_sys->i_frame_size >
 454                         p_sys->i_max_frame_size )
 455                     {
 456                         msg_Dbg( p_dec, "frame too big %d > %d "
 457                                  "(emulated startcode ?)", p_sys->i_frame_size,
 458                                  p_sys->i_max_frame_size );
 459                         block_SkipByte( &p_sys->bytestream );
 460                         p_sys->i_state = STATE_NOSYNC;
 461                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 462                         break;
 463                     }
 464
 465                     p_sys->i_frame_size++;
 466                     break;
 467                 }
 468
 469                 if( i_next_frame_size == -1 )
 470                 {
 471                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 472                     block_SkipByte( &p_sys->bytestream );
 473                     p_sys->i_state = STATE_NOSYNC;
 474                     break;
 475                 }
 476
 477                 /* Check info is in sync with previous one */
 478                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 479                     i_next_stereo_mode != p_sys->i_chan_mode ||
 480                     i_next_rate != p_sys->i_rate ||
 481                     i_next_layer != p_sys->i_layer ||
 482                     i_next_frame_length != p_sys->i_frame_length )
 483                 {
 484                     /* Free bitrate only */
 485                     if( p_sys->i_bit_rate == 0 )
 486                     {
 487                         p_sys->i_frame_size++;
 488                         break;
 489                     }
 490
 491                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 492                              "(emulated startcode ?)" );
 493                     block_SkipByte( &p_sys->bytestream );
 494                     p_sys->i_state = STATE_NOSYNC;
 495                     break;
 496                 }
 497
 498                 /* Free bitrate only */
 499                 if( p_sys->i_bit_rate == 0 )
 500                 {
 501                     if( i_next_bit_rate != 0 )
 502                     {
 503                         p_sys->i_frame_size++;
 504                         break;
 505                     }
 506                 }
 507
 508             }
 509             else
 510             {
 511                 /* Free bitrate only */
 512                 if( p_sys->i_bit_rate == 0 )
 513                 {
 514                     if( (unsigned int)p_sys->i_frame_size >
 515                         p_sys->i_max_frame_size )
 516                     {
 517                         msg_Dbg( p_dec, "frame too big %d > %d "
 518                                  "(emulated startcode ?)", p_sys->i_frame_size,
 519                                  p_sys->i_max_frame_size );
 520                         block_SkipByte( &p_sys->bytestream );
 521                         p_sys->i_state = STATE_NOSYNC;
 522                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 523                         break;
 524                     }
 525
 526                     p_sys->i_frame_size++;
 527                     break;
 528                 }
 529
 530                 msg_Dbg( p_dec, "emulated startcode "
 531                          "(no startcode on following frame)" );
 532                 p_sys->i_state = STATE_NOSYNC;
 533                 block_SkipByte( &p_sys->bytestream );
 534                 break;
 535             }
 536
 537             p_sys->i_state = STATE_GET_DATA;
 538             break;
 539
 540         case STATE_GET_DATA:
 541             /* Make sure we have enough data.
 542              * (Not useful if we went through NEXT_SYNC) */
 543             if( block_WaitBytes( &p_sys->bytestream,
 544                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 545             {
 546                 /* Need more data */
 547                 return NULL;
 548             }
 549             p_sys->i_state = STATE_SEND_DATA;
 550             /* fallthrough */
 551
 552         case STATE_SEND_DATA:
 553             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 554             {
 555                 return NULL;
 556             }
 557
 558             /* Free bitrate only */
 559             if( p_sys->i_bit_rate == 0 )
 560             {
 561                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 562             }
 563
 564             /* Copy the whole frame into the buffer. */
 565             if (block_GetBytes( &p_sys->bytestream,
 566                             p_buf, __MIN( (unsigned)p_sys->i_frame_size, p_out_buffer->i_buffer ) )) {
 567                 block_Release(p_out_buffer);
 568                 return NULL;
 569             }
 570
 571             p_sys->i_state = STATE_NOSYNC;
 572
 573             /* Make sure we don't reuse the same pts twice */
 574             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 575                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = VLC_TICK_INVALID;
 576
 577             if( p_sys->b_discontinuity )
 578             {
 579                 p_out_buffer->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 580                 p_sys->b_discontinuity = false;
 581             }
 582
 583             /* So p_block doesn't get re-added several times */
 584             p_block = block_BytestreamPop( &p_sys->bytestream );
 585             if (pp_block)
 586                 *pp_block = p_block;
 587             else if (p_block)
 588                 block_Release(p_block);
 589
 590             return p_out_buffer;
 591         }
 592     }
 593
 594     return NULL;
 595 }
 596
 597 /*****************************************************************************
 598  * Close: clean up the decoder
 599  *****************************************************************************/
 600 static void Close( vlc_object_t *p_this )
 601 {
 602     decoder_t *p_dec = (decoder_t *)p_this;
 603     decoder_sys_t *p_sys = p_dec->p_sys;
 604
 605     block_BytestreamRelease( &p_sys->bytestream );
 606
 607     free( p_sys );
 608 }
 609
 610 /*****************************************************************************
 611  * Open: probe the decoder and return score
 612  *****************************************************************************/
 613 static int Open( vlc_object_t *p_this )
 614 {
 615     decoder_t *p_dec = (decoder_t*)p_this;
 616     decoder_sys_t *p_sys;
 617
 618     if(( p_dec->fmt_in.i_codec != VLC_CODEC_MPGA ) &&
 619        ( p_dec->fmt_in.i_codec != VLC_CODEC_MP3 ) )
 620     {
 621         return VLC_EGENERIC;
 622     }
 623
 624     /* Allocate the memory needed to store the decoder's structure */
 625     if( ( p_dec->p_sys = p_sys =
 626           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 627         return VLC_ENOMEM;
 628
 629     /* Misc init */
 630     p_sys->i_state = STATE_NOSYNC;
 631     date_Init( &p_sys->end_date, 1, 1 );
 632     block_BytestreamInit( &p_sys->bytestream );
 633     p_sys->i_pts = VLC_TICK_INVALID;
 634     p_sys->b_discontinuity = false;
 635     p_sys->i_frame_size = 0;
 636
 637     p_sys->i_channels_conf = p_sys->i_chan_mode = p_sys->i_channels =
 638     p_sys->i_rate = p_sys->i_max_frame_size = p_sys->i_frame_length =
 639     p_sys->i_layer = p_sys->i_bit_rate = 0;
 640
 641     /* Set output properties */
 642     p_dec->fmt_out.i_codec = VLC_CODEC_MPGA;
 643     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 644
 645     /* Set callback */
 646     p_dec->pf_packetize    = DecodeBlock;
 647     p_dec->pf_flush        = Flush;
 648     p_dec->pf_get_cc       = NULL;
 649
 650     /* Start with the minimum size for a free bitrate frame */
 651     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 652
 653     return VLC_SUCCESS;
 654 }