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  * $Id$
   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 it
  13  * under the terms of the GNU Lesser General Public License as published by
  14  * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public License
  23  * along with this program; if not, write to the Free Software Foundation,
  24  * 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 #include <vlc_modules.h>
  39 #include <assert.h>
  40
  41 #include <vlc_block_helper.h>
  42
  43 #include "packetizer_helper.h"
  44
  45 /*****************************************************************************
  46  * decoder_sys_t : decoder descriptor
  47  *****************************************************************************/
  48 struct decoder_sys_t
  49 {
  50     /*
  51      * Input properties
  52      */
  53     int        i_state;
  54
  55     block_bytestream_t bytestream;
  56
  57     /*
  58      * Common properties
  59      */
  60     date_t          end_date;
  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 #define MAD_BUFFER_GUARD 8
  73 #define MPGA_HEADER_SIZE 4
  74
  75 /****************************************************************************
  76  * Local prototypes
  77  ****************************************************************************/
  78
  79 static int  Open( vlc_object_t * );
  80 static void Close(  vlc_object_t * );
  81
  82 /*****************************************************************************
  83  * Module descriptor
  84  *****************************************************************************/
  85 vlc_module_begin ()
  86     set_category( CAT_INPUT )
  87     set_subcategory( SUBCAT_INPUT_ACODEC )
  88     set_description( N_("MPEG audio layer I/II/III packetizer") )
  89     set_capability( "packetizer", 10 )
  90     set_callbacks( Open, Close )
  91 vlc_module_end ()
  92
  93 /*****************************************************************************
  94  * Flush:
  95  *****************************************************************************/
  96 static void Flush( decoder_t *p_dec )
  97 {
  98     decoder_sys_t *p_sys = p_dec->p_sys;
  99
 100     date_Set( &p_sys->end_date, VLC_TS_INVALID );
 101     p_sys->i_state = STATE_NOSYNC;
 102     block_BytestreamEmpty( &p_sys->bytestream );
 103     p_sys->b_discontinuity = true;
 104 }
 105
 106 /*****************************************************************************
 107  * GetOutBuffer:
 108  *****************************************************************************/
 109 static uint8_t *GetOutBuffer( decoder_t *p_dec, block_t **pp_out_buffer )
 110 {
 111     decoder_sys_t *p_sys = p_dec->p_sys;
 112
 113     if( p_dec->fmt_out.audio.i_rate != p_sys->i_rate ||
 114         date_Get( &p_sys->end_date ) == VLC_TS_INVALID )
 115     {
 116         msg_Dbg( p_dec, "MPGA channels:%d samplerate:%d bitrate:%d",
 117                   p_sys->i_channels, p_sys->i_rate, p_sys->i_bit_rate );
 118
 119         if( p_sys->end_date.i_divider_num == 0 )
 120             date_Init( &p_sys->end_date, p_sys->i_rate, 1 );
 121         else
 122             date_Change( &p_sys->end_date, p_sys->i_rate, 1 );
 123         date_Set( &p_sys->end_date, p_sys->i_pts );
 124     }
 125
 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_original_channels = p_sys->i_channels_conf;
 132     p_dec->fmt_out.audio.i_physical_channels =
 133         p_sys->i_channels_conf & AOUT_CHAN_PHYSMASK;
 134
 135     p_dec->fmt_out.i_bitrate = p_sys->i_bit_rate * 1000;
 136
 137     block_t *p_block = block_Alloc( p_sys->i_frame_size );
 138     if( p_block == NULL )
 139         return NULL;
 140
 141     p_block->i_pts = p_block->i_dts = date_Get( &p_sys->end_date );
 142     p_block->i_length =
 143         date_Increment( &p_sys->end_date, p_sys->i_frame_length ) - p_block->i_pts;
 144
 145     *pp_out_buffer = p_block;
 146     return p_block->p_buffer;
 147 }
 148
 149 /*****************************************************************************
 150  * SyncInfo: parse MPEG audio sync info
 151  *****************************************************************************/
 152 static int SyncInfo( uint32_t i_header, unsigned int * pi_channels,
 153                      unsigned int * pi_channels_conf,
 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
 209     if( *pi_layer != 4 &&
 210         i_bitrate_index < 0x0f &&
 211         i_samplerate_index != 0x03 &&
 212         i_emphasis != 0x02 )
 213     {
 214         switch ( i_mode )
 215         {
 216         case 0: /* stereo */
 217         case 1: /* joint stereo */
 218             *pi_channels = 2;
 219             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
 220             break;
 221         case 2: /* dual-mono */
 222             *pi_channels = 2;
 223             *pi_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 224                                 | AOUT_CHAN_DUALMONO;
 225             break;
 226         case 3: /* mono */
 227             *pi_channels = 1;
 228             *pi_channels_conf = AOUT_CHAN_CENTER;
 229             break;
 230         }
 231         *pi_bit_rate = ppi_bitrate[i_version][*pi_layer-1][i_bitrate_index];
 232         i_max_bit_rate = ppi_bitrate[i_version][*pi_layer-1][14];
 233         *pi_sample_rate = ppi_samplerate[i_version][i_samplerate_index];
 234
 235         if ( b_mpeg_2_5 )
 236         {
 237             *pi_sample_rate >>= 1;
 238         }
 239
 240         switch( *pi_layer )
 241         {
 242         case 1:
 243             i_frame_size = ( 12000 * *pi_bit_rate / *pi_sample_rate +
 244                            b_padding ) * 4;
 245             *pi_max_frame_size = ( 12000 * i_max_bit_rate /
 246                                  *pi_sample_rate + 1 ) * 4;
 247             *pi_frame_length = 384;
 248             break;
 249
 250         case 2:
 251             i_frame_size = 144000 * *pi_bit_rate / *pi_sample_rate + b_padding;
 252             *pi_max_frame_size = 144000 * i_max_bit_rate / *pi_sample_rate + 1;
 253             *pi_frame_length = 1152;
 254             break;
 255
 256         case 3:
 257             i_frame_size = ( i_version ? 72000 : 144000 ) *
 258                            *pi_bit_rate / *pi_sample_rate + b_padding;
 259             *pi_max_frame_size = ( i_version ? 72000 : 144000 ) *
 260                                  i_max_bit_rate / *pi_sample_rate + 1;
 261             *pi_frame_length = i_version ? 576 : 1152;
 262             break;
 263
 264         default:
 265             break;
 266         }
 267
 268         /* Free bitrate mode can support higher bitrates */
 269         if( !*pi_bit_rate ) *pi_max_frame_size *= 2;
 270     }
 271     else
 272     {
 273         return -1;
 274     }
 275
 276     return i_frame_size;
 277 }
 278
 279 /****************************************************************************
 280  * DecodeBlock: the whole thing
 281  ****************************************************************************
 282  * This function is called just after the thread is launched.
 283  ****************************************************************************/
 284 static block_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
 285 {
 286     decoder_sys_t *p_sys = p_dec->p_sys;
 287     uint8_t p_header[MAD_BUFFER_GUARD];
 288     uint32_t i_header;
 289     uint8_t *p_buf;
 290     block_t *p_out_buffer;
 291
 292     block_t *p_block = pp_block ? *pp_block : NULL;
 293
 294     if (p_block)
 295     {
 296         if( p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 297         {
 298             /* First always drain complete blocks before discontinuity */
 299             block_t *p_drain = DecodeBlock( p_dec, NULL );
 300             if( p_drain )
 301                 return p_drain;
 302
 303             Flush( p_dec );
 304
 305             if( p_block->i_flags & BLOCK_FLAG_CORRUPTED )
 306             {
 307                 block_Release( p_block );
 308                 return NULL;
 309             }
 310         }
 311
 312         if( !date_Get( &p_sys->end_date ) && p_block->i_pts <= VLC_TS_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
 348         case STATE_SYNC:
 349             /* New frame, set the Presentation Time Stamp */
 350             p_sys->i_pts = p_sys->bytestream.p_block->i_pts;
 351             if( p_sys->i_pts > VLC_TS_INVALID &&
 352                 p_sys->i_pts != date_Get( &p_sys->end_date ) )
 353             {
 354                 if( p_dec->fmt_in.i_original_fourcc == VLC_FOURCC( 'D','V','R',' ') )
 355                 {
 356                     if( date_Get( &p_sys->end_date ) == VLC_TS_INVALID )
 357                         date_Set( &p_sys->end_date, p_sys->i_pts );
 358                 }
 359                 else if ( p_sys->i_pts != date_Get( &p_sys->end_date ) )
 360                 {
 361                     date_Set( &p_sys->end_date, p_sys->i_pts );
 362                 }
 363             }
 364             p_sys->i_state = STATE_HEADER;
 365
 366         case STATE_HEADER:
 367             /* Get MPGA frame header (MPGA_HEADER_SIZE bytes) */
 368             if( block_PeekBytes( &p_sys->bytestream, p_header,
 369                                  MPGA_HEADER_SIZE ) != VLC_SUCCESS )
 370             {
 371                 /* Need more data */
 372                 return NULL;
 373             }
 374
 375             /* Build frame header */
 376             i_header = GetDWBE(p_header);
 377
 378             /* Check if frame is valid and get frame info */
 379             p_sys->i_frame_size = SyncInfo( i_header,
 380                                             &p_sys->i_channels,
 381                                             &p_sys->i_channels_conf,
 382                                             &p_sys->i_rate,
 383                                             &p_sys->i_bit_rate,
 384                                             &p_sys->i_frame_length,
 385                                             &p_sys->i_max_frame_size,
 386                                             &p_sys->i_layer );
 387
 388             p_dec->fmt_in.i_profile = p_sys->i_layer;
 389
 390             if( p_sys->i_frame_size == -1 )
 391             {
 392                 msg_Dbg( p_dec, "emulated startcode" );
 393                 block_SkipByte( &p_sys->bytestream );
 394                 p_sys->i_state = STATE_NOSYNC;
 395                 break;
 396             }
 397
 398             if( p_sys->i_bit_rate == 0 )
 399             {
 400                 /* Free bitrate, but 99% emulated startcode :( */
 401                 if( p_dec->p_sys->i_free_frame_size == MPGA_HEADER_SIZE )
 402                 {
 403                     msg_Dbg( p_dec, "free bitrate mode");
 404                 }
 405                 /* The -1 below is to account for the frame padding */
 406                 p_sys->i_frame_size = p_sys->i_free_frame_size - 1;
 407             }
 408
 409             p_sys->i_state = STATE_NEXT_SYNC;
 410
 411         case STATE_NEXT_SYNC:
 412             /* Check if next expected frame contains the sync word */
 413             if( block_PeekOffsetBytes( &p_sys->bytestream,
 414                                        p_sys->i_frame_size, p_header,
 415                                        MAD_BUFFER_GUARD ) != VLC_SUCCESS )
 416             {
 417                 if( p_block == NULL ) /* drain */
 418                 {
 419                     p_sys->i_state = STATE_SEND_DATA;
 420                     break;
 421                 }
 422                 /* Need more data */
 423                 return NULL;
 424             }
 425
 426             if( p_header[0] == 0xff && (p_header[1] & 0xe0) == 0xe0 )
 427             {
 428                 /* Startcode is fine, let's try the header as an extra check */
 429                 int i_next_frame_size;
 430                 unsigned int i_next_channels, i_next_channels_conf;
 431                 unsigned int i_next_rate, i_next_bit_rate;
 432                 unsigned int i_next_frame_length, i_next_max_frame_size;
 433                 unsigned int i_next_layer;
 434
 435                 /* Build frame header */
 436                 i_header = GetDWBE(p_header);
 437
 438                 i_next_frame_size = SyncInfo( i_header,
 439                                               &i_next_channels,
 440                                               &i_next_channels_conf,
 441                                               &i_next_rate,
 442                                               &i_next_bit_rate,
 443                                               &i_next_frame_length,
 444                                               &i_next_max_frame_size,
 445                                               &i_next_layer );
 446
 447                 /* Free bitrate only */
 448                 if( p_sys->i_bit_rate == 0 && i_next_frame_size == -1 )
 449                 {
 450                     if( (unsigned int)p_sys->i_frame_size >
 451                         p_sys->i_max_frame_size )
 452                     {
 453                         msg_Dbg( p_dec, "frame too big %d > %d "
 454                                  "(emulated startcode ?)", p_sys->i_frame_size,
 455                                  p_sys->i_max_frame_size );
 456                         block_SkipByte( &p_sys->bytestream );
 457                         p_sys->i_state = STATE_NOSYNC;
 458                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 459                         break;
 460                     }
 461
 462                     p_sys->i_frame_size++;
 463                     break;
 464                 }
 465
 466                 if( i_next_frame_size == -1 )
 467                 {
 468                     msg_Dbg( p_dec, "emulated startcode on next frame" );
 469                     block_SkipByte( &p_sys->bytestream );
 470                     p_sys->i_state = STATE_NOSYNC;
 471                     break;
 472                 }
 473
 474                 /* Check info is in sync with previous one */
 475                 if( i_next_channels_conf != p_sys->i_channels_conf ||
 476                     i_next_rate != p_sys->i_rate ||
 477                     i_next_layer != p_sys->i_layer ||
 478                     i_next_frame_length != p_sys->i_frame_length )
 479                 {
 480                     /* Free bitrate only */
 481                     if( p_sys->i_bit_rate == 0 )
 482                     {
 483                         p_sys->i_frame_size++;
 484                         break;
 485                     }
 486
 487                     msg_Dbg( p_dec, "parameters changed unexpectedly "
 488                              "(emulated startcode ?)" );
 489                     block_SkipByte( &p_sys->bytestream );
 490                     p_sys->i_state = STATE_NOSYNC;
 491                     break;
 492                 }
 493
 494                 /* Free bitrate only */
 495                 if( p_sys->i_bit_rate == 0 )
 496                 {
 497                     if( i_next_bit_rate != 0 )
 498                     {
 499                         p_sys->i_frame_size++;
 500                         break;
 501                     }
 502                 }
 503
 504             }
 505             else
 506             {
 507                 /* Free bitrate only */
 508                 if( p_sys->i_bit_rate == 0 )
 509                 {
 510                     if( (unsigned int)p_sys->i_frame_size >
 511                         p_sys->i_max_frame_size )
 512                     {
 513                         msg_Dbg( p_dec, "frame too big %d > %d "
 514                                  "(emulated startcode ?)", p_sys->i_frame_size,
 515                                  p_sys->i_max_frame_size );
 516                         block_SkipByte( &p_sys->bytestream );
 517                         p_sys->i_state = STATE_NOSYNC;
 518                         p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 519                         break;
 520                     }
 521
 522                     p_sys->i_frame_size++;
 523                     break;
 524                 }
 525
 526                 msg_Dbg( p_dec, "emulated startcode "
 527                          "(no startcode on following frame)" );
 528                 p_sys->i_state = STATE_NOSYNC;
 529                 block_SkipByte( &p_sys->bytestream );
 530                 break;
 531             }
 532
 533             p_sys->i_state = STATE_GET_DATA;
 534             break;
 535
 536         case STATE_GET_DATA:
 537             /* Make sure we have enough data.
 538              * (Not useful if we went through NEXT_SYNC) */
 539             if( block_WaitBytes( &p_sys->bytestream,
 540                                  p_sys->i_frame_size ) != VLC_SUCCESS )
 541             {
 542                 /* Need more data */
 543                 return NULL;
 544             }
 545             p_sys->i_state = STATE_SEND_DATA;
 546
 547         case STATE_SEND_DATA:
 548             if( !(p_buf = GetOutBuffer( p_dec, &p_out_buffer )) )
 549             {
 550                 return NULL;
 551             }
 552
 553             /* Free bitrate only */
 554             if( p_sys->i_bit_rate == 0 )
 555             {
 556                 p_sys->i_free_frame_size = p_sys->i_frame_size;
 557             }
 558
 559             /* Copy the whole frame into the buffer. */
 560             if (block_GetBytes( &p_sys->bytestream,
 561                             p_buf, __MIN( (unsigned)p_sys->i_frame_size, p_out_buffer->i_buffer ) )) {
 562                 block_Release(p_out_buffer);
 563                 return NULL;
 564             }
 565
 566             p_sys->i_state = STATE_NOSYNC;
 567
 568             /* Make sure we don't reuse the same pts twice */
 569             if( p_sys->i_pts == p_sys->bytestream.p_block->i_pts )
 570                 p_sys->i_pts = p_sys->bytestream.p_block->i_pts = VLC_TS_INVALID;
 571
 572             if( p_sys->b_discontinuity )
 573             {
 574                 p_out_buffer->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 575                 p_sys->b_discontinuity = false;
 576             }
 577
 578             /* So p_block doesn't get re-added several times */
 579             p_block = block_BytestreamPop( &p_sys->bytestream );
 580             if (pp_block)
 581                 *pp_block = p_block;
 582             else if (p_block)
 583                 block_Release(p_block);
 584
 585             return p_out_buffer;
 586         }
 587     }
 588
 589     return NULL;
 590 }
 591
 592 /*****************************************************************************
 593  * Close: clean up the decoder
 594  *****************************************************************************/
 595 static void Close( vlc_object_t *p_this )
 596 {
 597     decoder_t *p_dec = (decoder_t *)p_this;
 598     decoder_sys_t *p_sys = p_dec->p_sys;
 599
 600     block_BytestreamRelease( &p_sys->bytestream );
 601
 602     free( p_sys );
 603 }
 604
 605 /*****************************************************************************
 606  * Open: probe the decoder and return score
 607  *****************************************************************************/
 608 static int Open( vlc_object_t *p_this )
 609 {
 610     decoder_t *p_dec = (decoder_t*)p_this;
 611     decoder_sys_t *p_sys;
 612
 613     if(( p_dec->fmt_in.i_codec != VLC_CODEC_MPGA ) &&
 614        ( p_dec->fmt_in.i_codec != VLC_CODEC_MP3 ) )
 615     {
 616         return VLC_EGENERIC;
 617     }
 618
 619     /* Allocate the memory needed to store the decoder's structure */
 620     if( ( p_dec->p_sys = p_sys =
 621           (decoder_sys_t *)malloc(sizeof(decoder_sys_t)) ) == NULL )
 622         return VLC_ENOMEM;
 623
 624     /* Misc init */
 625     p_sys->i_state = STATE_NOSYNC;
 626     date_Init( &p_sys->end_date, 1, 1 );
 627     date_Set( &p_sys->end_date, VLC_TS_INVALID );
 628     block_BytestreamInit( &p_sys->bytestream );
 629     p_sys->i_pts = VLC_TS_INVALID;
 630     p_sys->b_discontinuity = false;
 631     p_sys->i_frame_size = 0;
 632
 633     p_sys->i_channels_conf = p_sys->i_channels = p_sys->i_rate =
 634     p_sys->i_max_frame_size = p_sys->i_frame_length = p_sys->i_layer =
 635     p_sys->i_bit_rate = 0;
 636
 637     /* Set output properties */
 638     p_dec->fmt_out.i_cat = AUDIO_ES;
 639     p_dec->fmt_out.i_codec = VLC_CODEC_MPGA;
 640     p_dec->fmt_out.audio.i_rate = 0; /* So end_date gets initialized */
 641
 642     /* Set callback */
 643     p_dec->pf_packetize    = DecodeBlock;
 644     p_dec->pf_flush        = Flush;
 645
 646     /* Start with the minimum size for a free bitrate frame */
 647     p_sys->i_free_frame_size = MPGA_HEADER_SIZE;
 648
 649     return VLC_SUCCESS;
 650 }