git.sesse.net Git - vlc/blob - modules/packetizer/mpegvideo.c

   1 /*****************************************************************************
   2  * mpegvideo.c: parse and packetize an MPEG1/2 video stream
   3  *****************************************************************************
   4  * Copyright (C) 2001, 2002 VideoLAN
   5  * $Id$
   6  *
   7  * Authors: Laurent Aimar <fenrir@via.ecp.fr>
   8  *          Eric Petit <titer@videolan.org>
   9  *          Gildas Bazin <gbazin@netcourrier.com>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 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 General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  24  *****************************************************************************/
  25
  26 /*****************************************************************************
  27  * Problem with this implementation:
  28  *
  29  * Although we should time-stamp each picture with a PTS, this isn't possible
  30  * with the current implementation.
  31  * The problem comes from the fact that for non-low-delay streams we can't
  32  * calculate the PTS of pictures used as backward reference. Even the temporal
  33  * reference number doesn't help here because all the pictures don't
  34  * necessarily have the same duration (eg. 3:2 pulldown).
  35  *
  36  * However this doesn't really matter as far as the MPEG muxers are concerned
  37  * because they allow having empty PTS fields. --gibalou
  38  *****************************************************************************/
  39
  40 /*****************************************************************************
  41  * Preamble
  42  *****************************************************************************/
  43 #include <stdlib.h>                                      /* malloc(), free() */
  44
  45 #include <vlc/vlc.h>
  46 #include <vlc/decoder.h>
  47 #include <vlc/input.h>
  48
  49 #include "vlc_block_helper.h"
  50
  51 /*****************************************************************************
  52  * Module descriptor
  53  *****************************************************************************/
  54 static int  Open ( vlc_object_t * );
  55 static void Close( vlc_object_t * );
  56
  57 vlc_module_begin();
  58     set_description( _("MPEG-I/II video packetizer") );
  59     set_capability( "packetizer", 50 );
  60     set_callbacks( Open, Close );
  61 vlc_module_end();
  62
  63 /*****************************************************************************
  64  * Local prototypes
  65  *****************************************************************************/
  66 static block_t *Packetize( decoder_t *, block_t ** );
  67 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
  68
  69 struct decoder_sys_t
  70 {
  71     /*
  72      * Input properties
  73      */
  74     block_bytestream_t bytestream;
  75     int i_state;
  76     int i_offset;
  77     uint8_t p_startcode[3];
  78
  79     /* Sequence header and extension */
  80     block_t *p_seq;
  81     block_t *p_ext;
  82
  83     /* Current frame being built */
  84     block_t    *p_frame;
  85     vlc_bool_t b_frame_slice;
  86     mtime_t i_pts;
  87     mtime_t i_dts;
  88
  89     /* Sequence properties */
  90     int         i_frame_rate;
  91     int         i_frame_rate_base;
  92     vlc_bool_t  b_seq_progressive;
  93     vlc_bool_t  b_low_delay;
  94     int         i_aspect_ratio_info;
  95     vlc_bool_t  b_inited;
  96
  97     /* Picture properties */
  98     int i_temporal_ref;
  99     int i_picture_type;
 100     int i_picture_structure;
 101     int i_top_field_first;
 102     int i_repeat_first_field;
 103     int i_progressive_frame;
 104
 105     mtime_t i_interpolated_dts;
 106     mtime_t i_old_duration;
 107     mtime_t i_last_ref_pts;
 108
 109     /* Number of pictures since last sequence header */
 110     int i_seq_old;
 111
 112 };
 113
 114 enum {
 115     STATE_NOSYNC,
 116     STATE_NEXT_SYNC
 117 };
 118
 119 /*****************************************************************************
 120  * Open:
 121  *****************************************************************************/
 122 static int Open( vlc_object_t *p_this )
 123 {
 124     decoder_t *p_dec = (decoder_t*)p_this;
 125     decoder_sys_t *p_sys;
 126
 127     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 128         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 129         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 130     {
 131         return VLC_EGENERIC;
 132     }
 133
 134     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 135     p_dec->pf_packetize = Packetize;
 136
 137     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 138
 139     /* Misc init */
 140     p_sys->i_state = STATE_NOSYNC;
 141     p_sys->bytestream = block_BytestreamInit( p_dec );
 142     p_sys->p_startcode[0] = 0;
 143     p_sys->p_startcode[1] = 0;
 144     p_sys->p_startcode[2] = 1;
 145     p_sys->i_offset = 0;
 146
 147     p_sys->p_seq = NULL;
 148     p_sys->p_ext = NULL;
 149     p_sys->p_frame = NULL;
 150     p_sys->b_frame_slice = VLC_FALSE;
 151
 152     p_sys->i_dts = p_sys->i_pts = 0;
 153
 154     p_sys->i_frame_rate = 1;
 155     p_sys->i_frame_rate_base = 1;
 156     p_sys->b_seq_progressive = VLC_TRUE;
 157     p_sys->b_low_delay = VLC_TRUE;
 158     p_sys->i_seq_old = 0;
 159
 160     p_sys->i_temporal_ref = 0;
 161     p_sys->i_picture_type = 0;
 162     p_sys->i_picture_structure = 0x03; /* frame */
 163     p_sys->i_top_field_first = 0;
 164     p_sys->i_repeat_first_field = 0;
 165     p_sys->i_progressive_frame = 0;
 166     p_sys->b_inited = 0;
 167
 168     p_sys->i_interpolated_dts = 0;
 169     p_sys->i_old_duration = 0;
 170     p_sys->i_last_ref_pts = 0;
 171
 172     return VLC_SUCCESS;
 173 }
 174
 175 /*****************************************************************************
 176  * Close:
 177  *****************************************************************************/
 178 static void Close( vlc_object_t *p_this )
 179 {
 180     decoder_t     *p_dec = (decoder_t*)p_this;
 181     decoder_sys_t *p_sys = p_dec->p_sys;
 182
 183     block_BytestreamRelease( &p_sys->bytestream );
 184
 185     if( p_sys->p_seq )
 186     {
 187         block_Release( p_sys->p_seq );
 188     }
 189     if( p_sys->p_ext )
 190     {
 191         block_Release( p_sys->p_ext );
 192     }
 193     if( p_sys->p_frame )
 194     {
 195         block_ChainRelease( p_sys->p_frame );
 196     }
 197
 198     free( p_sys );
 199 }
 200
 201 /*****************************************************************************
 202  * Packetize:
 203  *****************************************************************************/
 204 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 205 {
 206     decoder_sys_t *p_sys = p_dec->p_sys;
 207     block_t       *p_pic;
 208
 209     if( pp_block == NULL || *pp_block == NULL )
 210     {
 211         return NULL;
 212     }
 213
 214     if( (*pp_block)->i_flags & BLOCK_FLAG_DISCONTINUITY )
 215     {
 216         p_sys->i_state = STATE_NOSYNC;
 217         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 218         p_sys->p_frame = NULL;
 219         p_sys->b_frame_slice = VLC_FALSE;
 220         block_Release( *pp_block );
 221         return NULL;
 222     }
 223
 224     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 225
 226     while( 1 )
 227     {
 228         switch( p_sys->i_state )
 229         {
 230
 231         case STATE_NOSYNC:
 232             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 233                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 234             {
 235                 p_sys->i_state = STATE_NEXT_SYNC;
 236             }
 237
 238             if( p_sys->i_offset )
 239             {
 240                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 241                 p_sys->i_offset = 0;
 242                 block_BytestreamFlush( &p_sys->bytestream );
 243             }
 244
 245             if( p_sys->i_state != STATE_NEXT_SYNC )
 246             {
 247                 /* Need more data */
 248                 return NULL;
 249             }
 250
 251             p_sys->i_offset = 1; /* To find next startcode */
 252
 253         case STATE_NEXT_SYNC:
 254             /* TODO: If p_block == NULL, flush the buffer without checking the
 255              * next sync word */
 256
 257             /* Find the next startcode */
 258             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 259                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 260             {
 261                 /* Need more data */
 262                 return NULL;
 263             }
 264
 265             /* Get the new fragment and set the pts/dts */
 266             p_pic = block_New( p_dec, p_sys->i_offset );
 267             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 268             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 269
 270             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 271                             p_pic->i_buffer );
 272
 273             /* don't reuse the same timestamps several times */
 274             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 275             {
 276                 /* We have a picture start code */
 277                 p_sys->bytestream.p_block->i_pts = 0;
 278                 p_sys->bytestream.p_block->i_dts = 0;
 279             }
 280
 281             p_sys->i_offset = 0;
 282
 283             /* Get picture if any */
 284             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 285             {
 286                 p_sys->i_state = STATE_NOSYNC;
 287                 break;
 288             }
 289
 290             /* We've just started the stream, wait for the first PTS.
 291              * We discard here so we can still get the sequence header. */
 292             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 293                 p_sys->i_interpolated_dts <= 0 )
 294             {
 295                 msg_Dbg( p_dec, "need a starting pts/dts" );
 296                 p_sys->i_state = STATE_NOSYNC;
 297                 block_Release( p_pic );
 298                 break;
 299             }
 300
 301             /* When starting the stream we can have the first frame with
 302              * a null DTS (i_interpolated_pts is initialized to 0) */
 303             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 304
 305             /* So p_block doesn't get re-added several times */
 306             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 307
 308             p_sys->i_state = STATE_NOSYNC;
 309
 310             return p_pic;
 311         }
 312     }
 313 }
 314
 315 /*****************************************************************************
 316  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 317  *****************************************************************************/
 318 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 319 {
 320     decoder_sys_t *p_sys = p_dec->p_sys;
 321     block_t *p_pic = NULL;
 322
 323     /*
 324      * Check if previous picture is finished
 325      */
 326     if( ( p_sys->b_frame_slice &&
 327           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 328           p_sys->p_seq == NULL )
 329     {
 330         /* We have a picture but without a sequence header we can't
 331          * do anything */
 332         msg_Dbg( p_dec, "waiting for sequence start" );
 333         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 334         p_sys->p_frame = NULL;
 335         p_sys->b_frame_slice = VLC_FALSE;
 336
 337     }
 338     else if( p_sys->b_frame_slice &&
 339              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 340     {
 341         mtime_t i_duration;
 342
 343         p_pic = block_ChainGather( p_sys->p_frame );
 344
 345         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 346                                 p_sys->i_frame_rate );
 347
 348         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 349         {
 350             i_duration /= 2;
 351         }
 352
 353         if( p_sys->b_seq_progressive )
 354         {
 355             if( p_sys->i_top_field_first == 0 &&
 356                 p_sys->i_repeat_first_field == 1 )
 357             {
 358                 i_duration *= 2;
 359             }
 360             else if( p_sys->i_top_field_first == 1 &&
 361                      p_sys->i_repeat_first_field == 1 )
 362             {
 363                 i_duration *= 3;
 364             }
 365         }
 366         else
 367         {
 368             if( p_sys->i_picture_structure == 0x03 )
 369             {
 370                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 371                 {
 372                     i_duration += i_duration / 2;
 373                 }
 374             }
 375         }
 376
 377         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 378         {
 379             /* Trivial case (DTS == PTS) */
 380             /* Correct interpolated dts when we receive a new pts/dts */
 381             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 382             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 383         }
 384         else
 385         {
 386             /* Correct interpolated dts when we receive a new pts/dts */
 387             if( p_sys->i_last_ref_pts > 0 )
 388                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 389             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 390
 391             p_sys->i_last_ref_pts = p_sys->i_pts;
 392         }
 393
 394         p_pic->i_dts = p_sys->i_interpolated_dts;
 395
 396         /* Set PTS only if we have a B frame or if it comes from the stream */
 397         if( p_sys->i_pts > 0 )
 398         {
 399             p_pic->i_pts = p_sys->i_pts;
 400         }
 401         else if( p_sys->i_picture_type == 0x03 )
 402         {
 403             p_pic->i_pts = p_pic->i_dts;
 404         }
 405         else
 406         {
 407             p_pic->i_pts = 0;
 408         }
 409
 410         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 411         {
 412             /* Trivial case (DTS == PTS) */
 413             p_sys->i_interpolated_dts += i_duration;
 414         }
 415         else
 416         {
 417             p_sys->i_interpolated_dts += p_sys->i_old_duration;
 418             p_sys->i_old_duration = i_duration;
 419         }
 420
 421         switch ( p_sys->i_picture_type )
 422         {
 423         case 0x01:
 424             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 425             break;
 426         case 0x02:
 427             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 428             break;
 429         case 0x03:
 430             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 431             break;
 432         }
 433
 434         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 435
 436 #if 0
 437         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 438         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 439 #endif
 440
 441         /* Reset context */
 442         p_sys->p_frame = NULL;
 443         p_sys->b_frame_slice = VLC_FALSE;
 444     }
 445
 446     /*
 447      * Check info of current fragment
 448      */
 449     if( p_frag->p_buffer[3] == 0xb8 )
 450     {
 451         /* Group start code */
 452         if( p_sys->p_seq &&
 453             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 454         {
 455             /* Usefull for mpeg1: repeat sequence header every second */
 456             block_ChainAppend( &p_sys->p_frame,
 457                                block_Duplicate( p_sys->p_seq ) );
 458             if( p_sys->p_ext )
 459             {
 460                 block_ChainAppend( &p_sys->p_frame,
 461                                    block_Duplicate( p_sys->p_ext ) );
 462             }
 463
 464             p_sys->i_seq_old = 0;
 465         }
 466     }
 467     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 468     {
 469         /* Sequence header code */
 470         static const int code_to_frame_rate[16][2] =
 471         {
 472             { 1, 1 },  /* invalid */
 473             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 474             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 475             /* Unofficial 15fps from Xing*/
 476             { 15, 1001 },
 477             /* Unofficial economy rates from libmpeg3 */
 478             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 479             { 1, 1 },  { 1, 1 }  /* invalid */
 480         };
 481
 482         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 483         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 484
 485         p_sys->p_seq = block_Duplicate( p_frag );
 486         p_sys->i_seq_old = 0;
 487         p_sys->p_ext = NULL;
 488
 489         p_dec->fmt_out.video.i_width =
 490             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 491         p_dec->fmt_out.video.i_height =
 492             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 493         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 494
 495         /* TODO: MPEG1 aspect ratio */
 496
 497         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 498         p_sys->i_frame_rate_base =
 499             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 500
 501         p_sys->b_seq_progressive = VLC_TRUE;
 502         p_sys->b_low_delay = VLC_TRUE;
 503
 504         if ( !p_sys->b_inited )
 505         {
 506             msg_Dbg( p_dec, "Size %dx%d fps=%.3f",
 507                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 508                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 509             p_sys->b_inited = 1;
 510         }
 511     }
 512     else if( p_frag->p_buffer[3] == 0xb5 )
 513     {
 514         int i_type = p_frag->p_buffer[4] >> 4;
 515
 516         /* Extention start code */
 517         if( i_type == 0x01 )
 518         {
 519             static const int mpeg2_aspect[16][2] =
 520             {
 521                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 522                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 523                 {0,1}, {0,1}
 524             };
 525
 526             /* sequence extention */
 527             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 528             p_sys->p_ext = block_Duplicate( p_frag );
 529
 530             if( p_frag->i_buffer >= 10 )
 531             {
 532                 p_sys->b_seq_progressive =
 533                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 534                 p_sys->b_low_delay =
 535                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 536             }
 537
 538             p_dec->fmt_out.video.i_aspect =
 539                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 540                 VOUT_ASPECT_FACTOR /
 541                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 542
 543         }
 544         else if( i_type == 0x08 )
 545         {
 546             /* picture extention */
 547             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 548             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 549             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 550             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 551         }
 552     }
 553     else if( p_frag->p_buffer[3] == 0x00 )
 554     {
 555         /* Picture start code */
 556         p_sys->i_seq_old++;
 557
 558         if( p_frag->i_buffer >= 6 )
 559         {
 560             p_sys->i_temporal_ref =
 561                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 562             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 563         }
 564
 565         p_sys->i_dts = p_frag->i_dts;
 566         p_sys->i_pts = p_frag->i_pts;
 567     }
 568     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 569     {
 570         /* Slice start code */
 571         p_sys->b_frame_slice = VLC_TRUE;
 572     }
 573
 574     /* Append the block */
 575     block_ChainAppend( &p_sys->p_frame, p_frag );
 576
 577     return p_pic;
 578 }