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: mpegvideo.c,v 1.28 2004/01/27 14:05:33 gbazin Exp $
   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 extention */
  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
  96     /* Picture properties */
  97     int i_temporal_ref;
  98     int i_picture_type;
  99     int i_picture_structure;
 100     int i_top_field_first;
 101     int i_repeat_first_field;
 102     int i_progressive_frame;
 103
 104     mtime_t i_interpolated_dts;
 105     mtime_t i_old_duration;
 106     mtime_t i_last_ref_pts;
 107
 108     /* Number of pictues since last sequence header */
 109     int i_seq_old;
 110
 111 };
 112
 113 enum {
 114     STATE_NOSYNC,
 115     STATE_NEXT_SYNC
 116 };
 117
 118 /*****************************************************************************
 119  * Open:
 120  *****************************************************************************/
 121 static int Open( vlc_object_t *p_this )
 122 {
 123     decoder_t *p_dec = (decoder_t*)p_this;
 124     decoder_sys_t *p_sys;
 125
 126     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 127         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 128         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 129     {
 130         return VLC_EGENERIC;
 131     }
 132
 133     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 134     p_dec->pf_packetize = Packetize;
 135
 136     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 137
 138     /* Misc init */
 139     p_sys->i_state = STATE_NOSYNC;
 140     p_sys->bytestream = block_BytestreamInit( p_dec );
 141     p_sys->p_startcode[0] = 0;
 142     p_sys->p_startcode[1] = 0;
 143     p_sys->p_startcode[2] = 1;
 144     p_sys->i_offset = 0;
 145
 146     p_sys->p_seq = NULL;
 147     p_sys->p_ext = NULL;
 148     p_sys->p_frame = NULL;
 149     p_sys->b_frame_slice = VLC_FALSE;
 150
 151     p_sys->i_dts = p_sys->i_pts = 0;
 152
 153     p_sys->i_frame_rate = 1;
 154     p_sys->i_frame_rate_base = 1;
 155     p_sys->b_seq_progressive = VLC_TRUE;
 156     p_sys->b_low_delay = VLC_TRUE;
 157     p_sys->i_seq_old = 0;
 158
 159     p_sys->i_temporal_ref = 0;
 160     p_sys->i_picture_type = 0;
 161     p_sys->i_picture_structure = 0x03; /* frame */
 162     p_sys->i_top_field_first = 0;
 163     p_sys->i_repeat_first_field = 0;
 164     p_sys->i_progressive_frame = 0;
 165
 166     p_sys->i_interpolated_dts = 0;
 167     p_sys->i_old_duration = 0;
 168     p_sys->i_last_ref_pts = 0;
 169
 170     return VLC_SUCCESS;
 171 }
 172
 173 /*****************************************************************************
 174  * Close:
 175  *****************************************************************************/
 176 static void Close( vlc_object_t *p_this )
 177 {
 178     decoder_t     *p_dec = (decoder_t*)p_this;
 179     decoder_sys_t *p_sys = p_dec->p_sys;
 180
 181     block_BytestreamRelease( &p_sys->bytestream );
 182
 183     if( p_sys->p_seq )
 184     {
 185         block_Release( p_sys->p_seq );
 186     }
 187     if( p_sys->p_ext )
 188     {
 189         block_Release( p_sys->p_ext );
 190     }
 191     if( p_sys->p_frame )
 192     {
 193         block_ChainRelease( p_sys->p_frame );
 194     }
 195
 196     free( p_sys );
 197 }
 198
 199 /*****************************************************************************
 200  * Packetize:
 201  *****************************************************************************/
 202 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 203 {
 204     decoder_sys_t *p_sys = p_dec->p_sys;
 205     block_t       *p_pic;
 206
 207     if( pp_block == NULL || *pp_block == NULL )
 208     {
 209         return NULL;
 210     }
 211
 212     if( (*pp_block)->b_discontinuity )
 213     {
 214         p_sys->i_state = STATE_NOSYNC;
 215         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 216         p_sys->p_frame = NULL;
 217         p_sys->b_frame_slice = VLC_FALSE;
 218     }
 219
 220     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 221
 222     while( 1 )
 223     {
 224         switch( p_sys->i_state )
 225         {
 226
 227         case STATE_NOSYNC:
 228             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 229                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 230             {
 231                 p_sys->i_state = STATE_NEXT_SYNC;
 232             }
 233
 234             if( p_sys->i_offset )
 235             {
 236                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 237                 p_sys->i_offset = 0;
 238                 block_BytestreamFlush( &p_sys->bytestream );
 239             }
 240
 241             if( p_sys->i_state != STATE_NEXT_SYNC )
 242             {
 243                 /* Need more data */
 244                 return NULL;
 245             }
 246
 247             p_sys->i_offset = 1; /* To find next startcode */
 248
 249         case STATE_NEXT_SYNC:
 250             /* TODO: If p_block == NULL, flush the buffer without checking the
 251              * next sync word */
 252
 253             /* Find the next startcode */
 254             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 255                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 256             {
 257                 /* Need more data */
 258                 return NULL;
 259             }
 260
 261             /* Get the new fragment and set the pts/dts */
 262             p_pic = block_New( p_dec, p_sys->i_offset );
 263             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 264             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 265
 266             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 267                             p_pic->i_buffer );
 268
 269             /* don't reuse the same timestamps several times */
 270             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 271             {
 272                 /* We have a picture start code */
 273                 p_sys->bytestream.p_block->i_pts = 0;
 274                 p_sys->bytestream.p_block->i_dts = 0;
 275             }
 276
 277             p_sys->i_offset = 0;
 278
 279             /* Get picture if any */
 280             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 281             {
 282                 p_sys->i_state = STATE_NOSYNC;
 283                 break;
 284             }
 285
 286             /* We've just started the stream, wait for the first PTS.
 287              * We discard here so we can still get the sequence header. */
 288             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 289                 p_sys->i_interpolated_dts <= 0 )
 290             {
 291                 msg_Dbg( p_dec, "need a starting pts/dts" );
 292                 p_sys->i_state = STATE_NOSYNC;
 293                 block_Release( p_pic );
 294                 break;
 295             }
 296
 297             /* When starting the stream we can have the first frame with
 298              * a null DTS (i_interpolated_pts is initialized to 0) */
 299             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 300
 301             /* So p_block doesn't get re-added several times */
 302             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 303
 304             p_sys->i_state = STATE_NOSYNC;
 305
 306             return p_pic;
 307         }
 308     }
 309 }
 310
 311 /*****************************************************************************
 312  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 313  *****************************************************************************/
 314 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 315 {
 316     decoder_sys_t *p_sys = p_dec->p_sys;
 317     block_t *p_pic = NULL;
 318
 319     /*
 320      * Check if previous picture is finished
 321      */
 322     if( ( p_sys->b_frame_slice &&
 323           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 324           p_sys->p_seq == NULL )
 325     {
 326         /* We have a picture but without a sequence header we can't
 327          * do anything */
 328         msg_Dbg( p_dec, "waiting for sequence start" );
 329         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 330         p_sys->p_frame = NULL;
 331         p_sys->b_frame_slice = VLC_FALSE;
 332
 333     }
 334     else if( p_sys->b_frame_slice &&
 335              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 336     {
 337         mtime_t i_duration;
 338
 339         p_pic = block_ChainGather( p_sys->p_frame );
 340
 341         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 342                                 p_sys->i_frame_rate );
 343
 344         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 345         {
 346             i_duration /= 2;
 347         }
 348
 349         if( p_sys->b_seq_progressive )
 350         {
 351             if( p_sys->i_top_field_first == 0 &&
 352                 p_sys->i_repeat_first_field == 1 )
 353             {
 354                 i_duration *= 2;
 355             }
 356             else if( p_sys->i_top_field_first == 1 &&
 357                      p_sys->i_repeat_first_field == 1 )
 358             {
 359                 i_duration *= 3;
 360             }
 361         }
 362         else
 363         {
 364             if( p_sys->i_picture_structure == 0x03 )
 365             {
 366                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 367                 {
 368                     i_duration += i_duration / 2;
 369                 }
 370             }
 371         }
 372
 373         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 374         {
 375             /* Trivial case (DTS == PTS) */
 376             /* Correct interpolated dts when we receive a new pts/dts */
 377             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 378             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 379         }
 380         else
 381         {
 382             /* Correct interpolated dts when we receive a new pts/dts */
 383             if( p_sys->i_last_ref_pts > 0 )
 384                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 385             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 386
 387             p_sys->i_last_ref_pts = p_sys->i_pts;
 388         }
 389
 390         p_pic->i_dts = p_sys->i_interpolated_dts;
 391
 392         /* Set PTS only if we have a B frame or if it comes from the stream */
 393         if( p_sys->i_pts > 0 )
 394         {
 395             p_pic->i_pts = p_sys->i_pts;
 396         }
 397         else if( p_sys->i_picture_type == 0x03 )
 398         {
 399             p_pic->i_pts = p_pic->i_dts;
 400         }
 401         else
 402         {
 403             p_pic->i_pts = 0;
 404         }
 405
 406         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 407         {
 408             /* Trivial case (DTS == PTS) */
 409             p_sys->i_interpolated_dts += i_duration;
 410         }
 411         else
 412         {
 413             p_sys->i_interpolated_dts += p_sys->i_old_duration;
 414             p_sys->i_old_duration = i_duration;
 415         }
 416
 417         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 418
 419 #if 0
 420         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 421         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 422 #endif
 423
 424         /* Reset context */
 425         p_sys->p_frame = NULL;
 426         p_sys->b_frame_slice = VLC_FALSE;
 427     }
 428
 429     /*
 430      * Check info of current fragment
 431      */
 432     if( p_frag->p_buffer[3] == 0xb8 )
 433     {
 434         /* Group start code */
 435         if( p_sys->p_seq &&
 436             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 437         {
 438             /* Usefull for mpeg1: repeat sequence header every second */
 439             block_ChainAppend( &p_sys->p_frame,
 440                                block_Duplicate( p_sys->p_seq ) );
 441             if( p_sys->p_ext )
 442             {
 443                 block_ChainAppend( &p_sys->p_frame,
 444                                    block_Duplicate( p_sys->p_ext ) );
 445             }
 446
 447             p_sys->i_seq_old = 0;
 448         }
 449     }
 450     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 451     {
 452         /* Sequence header code */
 453         static const int code_to_frame_rate[16][2] =
 454         {
 455             { 1, 1 },  /* invalid */
 456             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 457             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 458             /* Unofficial 15fps from Xing*/
 459             { 15, 1001 },
 460             /* Unofficial economy rates from libmpeg3 */
 461             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 462             { 1, 1 },  { 1, 1 }  /* invalid */
 463         };
 464
 465         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 466         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 467
 468         p_sys->p_seq = block_Duplicate( p_frag );
 469         p_sys->i_seq_old = 0;
 470         p_sys->p_ext = NULL;
 471
 472         p_dec->fmt_out.video.i_width =
 473             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 474         p_dec->fmt_out.video.i_height =
 475             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 476         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 477
 478         /* TODO: MPEG1 aspect ratio */
 479
 480         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 481         p_sys->i_frame_rate_base =
 482             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 483
 484         p_sys->b_seq_progressive = VLC_TRUE;
 485         p_sys->b_low_delay = VLC_TRUE;
 486
 487 #if 0
 488         msg_Dbg( p_dec, "Size %dx%d fps=%.3f",
 489                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 490                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 491 #endif
 492     }
 493     else if( p_frag->p_buffer[3] == 0xb5 )
 494     {
 495         int i_type = p_frag->p_buffer[4] >> 4;
 496
 497         /* Extention start code */
 498         if( i_type == 0x01 )
 499         {
 500             static const int mpeg2_aspect[16][2] =
 501             {
 502                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 503                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 504                 {0,1}, {0,1}
 505             };
 506
 507             /* sequence extention */
 508             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 509             p_sys->p_ext = block_Duplicate( p_frag );
 510
 511             if( p_frag->i_buffer >= 10 )
 512             {
 513                 p_sys->b_seq_progressive =
 514                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 515                 p_sys->b_low_delay =
 516                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 517             }
 518
 519             p_dec->fmt_out.video.i_aspect =
 520                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 521                 VOUT_ASPECT_FACTOR /
 522                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 523
 524         }
 525         else if( i_type == 0x08 )
 526         {
 527             /* picture extention */
 528             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 529             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 530             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 531             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 532         }
 533     }
 534     else if( p_frag->p_buffer[3] == 0x00 )
 535     {
 536         /* Picture start code */
 537         p_sys->i_seq_old++;
 538
 539         if( p_frag->i_buffer >= 6 )
 540         {
 541             p_sys->i_temporal_ref =
 542                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 543             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 544         }
 545
 546         p_sys->i_dts = p_frag->i_dts;
 547         p_sys->i_pts = p_frag->i_pts;
 548     }
 549     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 550     {
 551         /* Slice start code */
 552         p_sys->b_frame_slice = VLC_TRUE;
 553     }
 554
 555     /* Append the block */
 556     block_ChainAppend( &p_sys->p_frame, p_frag );
 557
 558     return p_pic;
 559 }