research.m1stereo.tv/gitweb/ - melted/blob - src/modules/core/transition_composite.c

   1 /*
   2  * transition_composite.c -- compose one image over another using alpha channel
   3  * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
   4  * Author: Dan Dennedy <dan@dennedy.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 #include "transition_composite.h"
  22 #include <framework/mlt_frame.h>
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <ctype.h>
  27 #include <string.h>
  28 #include <math.h>
  29
  30 /** Geometry struct.
  31 */
  32
  33 struct geometry_s
  34 {
  35         float position;
  36         float mix;
  37         int nw; // normalised width
  38         int nh; // normalised height
  39         int sw; // scaled width, not including consumer scale based upon w/nw
  40         int sh; // scaled height, not including consumer scale based upon h/nh
  41         float x;
  42         float y;
  43         float w;
  44         float h;
  45         int halign; // horizontal alignment: 0=left, 1=center, 2=right
  46         int valign; // vertical alignment: 0=top, 1=middle, 2=bottom
  47         int distort;
  48         struct geometry_s *next;
  49 };
  50
  51 /** Parse a value from a geometry string.
  52 */
  53
  54 static float parse_value( char **ptr, int normalisation, char delim, float defaults )
  55 {
  56         float value = defaults;
  57
  58         if ( *ptr != NULL && **ptr != '\0' )
  59         {
  60                 char *end = NULL;
  61                 value = strtod( *ptr, &end );
  62                 if ( end != NULL )
  63                 {
  64                         if ( *end == '%' )
  65                                 value = ( value / 100.0 ) * normalisation;
  66                         while ( *end == delim || *end == '%' )
  67                                 end ++;
  68                 }
  69                 *ptr = end;
  70         }
  71
  72         return value;
  73 }
  74
  75 /** Parse a geometry property string with the syntax X,Y:WxH:MIX. Any value can be
  76         expressed as a percentage by appending a % after the value, otherwise values are
  77         assumed to be relative to the normalised dimensions of the consumer.
  78 */
  79
  80 static void geometry_parse( struct geometry_s *geometry, struct geometry_s *defaults, char *property, int nw, int nh )
  81 {
  82         // Assign normalised width and height
  83         geometry->nw = nw;
  84         geometry->nh = nh;
  85
  86         // Assign from defaults if available
  87         if ( defaults != NULL )
  88         {
  89                 geometry->x = defaults->x;
  90                 geometry->y = defaults->y;
  91                 geometry->w = geometry->sw = defaults->w;
  92                 geometry->h = geometry->sh = defaults->h;
  93                 geometry->distort = defaults->distort;
  94                 geometry->mix = defaults->mix;
  95                 defaults->next = geometry;
  96         }
  97         else
  98         {
  99                 geometry->mix = 100;
 100         }
 101
 102         // Parse the geomtry string
 103         if ( property != NULL && strcmp( property, "" ) )
 104         {
 105                 char *ptr = property;
 106                 geometry->x = parse_value( &ptr, nw, ',', geometry->x );
 107                 geometry->y = parse_value( &ptr, nh, ':', geometry->y );
 108                 geometry->w = geometry->sw = parse_value( &ptr, nw, 'x', geometry->w );
 109                 geometry->h = geometry->sh = parse_value( &ptr, nh, ':', geometry->h );
 110                 if ( *ptr == '!' )
 111                 {
 112                         geometry->distort = 1;
 113                         ptr ++;
 114                         if ( *ptr == ':' )
 115                                 ptr ++;
 116                 }
 117                 geometry->mix = parse_value( &ptr, 100, ' ', geometry->mix );
 118         }
 119 }
 120
 121 /** Calculate real geometry.
 122 */
 123
 124 static void geometry_calculate( struct geometry_s *output, struct geometry_s *in, float position )
 125 {
 126         // Search in for position
 127         struct geometry_s *out = in->next;
 128
 129         if ( position >= 1.0 )
 130         {
 131                 int section = floor( position );
 132                 position -= section;
 133                 if ( section % 2 == 1 )
 134                         position = 1.0 - position;
 135         }
 136
 137         while ( out->next != NULL )
 138         {
 139                 if ( position >= in->position && position < out->position )
 140                         break;
 141
 142                 in = out;
 143                 out = in->next;
 144         }
 145
 146         position = ( position - in->position ) / ( out->position - in->position );
 147
 148         // Calculate this frames geometry
 149         output->nw = in->nw;
 150         output->nh = in->nh;
 151         output->x = in->x + ( out->x - in->x ) * position;
 152         output->y = in->y + ( out->y - in->y ) * position;
 153         output->w = in->w + ( out->w - in->w ) * position;
 154         output->h = in->h + ( out->h - in->h ) * position;
 155         output->mix = in->mix + ( out->mix - in->mix ) * position;
 156         output->distort = in->distort;
 157
 158         output->x = ( int )floor( output->x ) & 0xfffffffe;
 159         output->w = ( int )floor( output->w ) & 0xfffffffe;
 160         output->sw &= 0xfffffffe;
 161 }
 162
 163 void transition_destroy_keys( void *arg )
 164 {
 165         struct geometry_s *ptr = arg;
 166         struct geometry_s *next = NULL;
 167
 168         while ( ptr != NULL )
 169         {
 170                 next = ptr->next;
 171                 free( ptr );
 172                 ptr = next;
 173         }
 174 }
 175
 176 static struct geometry_s *transition_parse_keys( mlt_transition this,  int normalised_width, int normalised_height )
 177 {
 178         // Loop variable for property interrogation
 179         int i = 0;
 180
 181         // Get the properties of the transition
 182         mlt_properties properties = mlt_transition_properties( this );
 183
 184         // Get the in and out position
 185         mlt_position in = mlt_transition_get_in( this );
 186         mlt_position out = mlt_transition_get_out( this );
 187
 188         // Create the start
 189         struct geometry_s *start = calloc( 1, sizeof( struct geometry_s ) );
 190
 191         // Create the end (we always need two entries)
 192         struct geometry_s *end = calloc( 1, sizeof( struct geometry_s ) );
 193
 194         // Pointer
 195         struct geometry_s *ptr = start;
 196
 197         // Parse the start property
 198         geometry_parse( start, NULL, mlt_properties_get( properties, "start" ), normalised_width, normalised_height );
 199
 200         // Parse the keys in between
 201         for ( i = 0; i < mlt_properties_count( properties ); i ++ )
 202         {
 203                 // Get the name of the property
 204                 char *name = mlt_properties_get_name( properties, i );
 205
 206                 // Check that it's valid
 207                 if ( !strncmp( name, "key[", 4 ) )
 208                 {
 209                         // Get the value of the property
 210                         char *value = mlt_properties_get_value( properties, i );
 211
 212                         // Determine the frame number
 213                         int frame = atoi( name + 4 );
 214
 215                         // Determine the position
 216                         float position = 0;
 217
 218                         if ( frame >= 0 && frame < ( out - in ) )
 219                                 position = ( float )frame / ( float )( out - in + 1 );
 220                         else if ( frame < 0 && - frame < ( out - in ) )
 221                                 position = ( float )( out - in + frame ) / ( float )( out - in + 1 );
 222
 223                         // For now, we'll exclude all keys received out of order
 224                         if ( position > ptr->position )
 225                         {
 226                                 // Create a new geometry
 227                                 struct geometry_s *temp = calloc( 1, sizeof( struct geometry_s ) );
 228
 229                                 // Parse and add to the list
 230                                 geometry_parse( temp, ptr, value, normalised_width, normalised_height );
 231
 232                                 // Assign the position
 233                                 temp->position = position;
 234
 235                                 // Allow the next to be appended after this one
 236                                 ptr = temp;
 237                         }
 238                         else
 239                         {
 240                                 fprintf( stderr, "Key out of order - skipping %s\n", name );
 241                         }
 242                 }
 243         }
 244
 245         // Parse the end
 246         geometry_parse( end, ptr, mlt_properties_get( properties, "end" ), normalised_width, normalised_height );
 247         if ( out > 0 )
 248                 end->position = ( float )( out - in ) / ( float )( out - in + 1 );
 249         else
 250                 end->position = 1;
 251
 252         // Assign to properties to ensure we get destroyed
 253         mlt_properties_set_data( properties, "geometries", start, 0, transition_destroy_keys, NULL );
 254
 255         return start;
 256 }
 257
 258 /** Parse the alignment properties into the geometry.
 259 */
 260
 261 static int alignment_parse( char* align )
 262 {
 263         int ret = 0;
 264
 265         if ( align == NULL );
 266         else if ( isdigit( align[ 0 ] ) )
 267                 ret = atoi( align );
 268         else if ( align[ 0 ] == 'c' || align[ 0 ] == 'm' )
 269                 ret = 1;
 270         else if ( align[ 0 ] == 'r' || align[ 0 ] == 'b' )
 271                 ret = 2;
 272
 273         return ret;
 274 }
 275
 276 /** Adjust position according to scaled size and alignment properties.
 277 */
 278
 279 static void alignment_calculate( struct geometry_s *geometry )
 280 {
 281         geometry->x += ( geometry->w - geometry->sw ) * geometry->halign / 2;
 282         geometry->y += ( geometry->h - geometry->sh ) * geometry->valign / 2;
 283 }
 284
 285 /** Calculate the position for this frame.
 286 */
 287
 288 static float position_calculate( mlt_transition this, mlt_position position )
 289 {
 290         // Get the in and out position
 291         mlt_position in = mlt_transition_get_in( this );
 292         mlt_position out = mlt_transition_get_out( this );
 293
 294         // Now do the calcs
 295         return ( float )( position - in ) / ( float )( out - in + 1 );
 296 }
 297
 298 /** Calculate the field delta for this frame - position between two frames.
 299 */
 300
 301 static inline float delta_calculate( mlt_transition this, mlt_frame frame )
 302 {
 303         // Get the in and out position
 304         mlt_position in = mlt_transition_get_in( this );
 305         mlt_position out = mlt_transition_get_out( this );
 306
 307         // Get the position of the frame
 308         mlt_position position = mlt_frame_get_position( frame );
 309
 310         // Now do the calcs
 311         float x = ( float )( position - in ) / ( float )( out - in + 1 );
 312         float y = ( float )( position + 1 - in ) / ( float )( out - in + 1 );
 313
 314         return ( y - x ) / 2.0;
 315 }
 316
 317 static int get_value( mlt_properties properties, char *preferred, char *fallback )
 318 {
 319         int value = mlt_properties_get_int( properties, preferred );
 320         if ( value == 0 )
 321                 value = mlt_properties_get_int( properties, fallback );
 322         return value;
 323 }
 324
 325 /** Composite function.
 326 */
 327
 328 static int composite_yuv( uint8_t *p_dest, int width_dest, int height_dest, int bpp, uint8_t *p_src, int width_src, int height_src, uint8_t *p_alpha, struct geometry_s geometry, int field )
 329 {
 330         int ret = 0;
 331         int i, j;
 332         int x_src = 0, y_src = 0;
 333         int32_t weight = ( 1 << 16 ) * ( geometry.mix / 100 );
 334         int stride_src = width_src * bpp;
 335         int stride_dest = width_dest * bpp;
 336
 337         // Adjust to consumer scale
 338         int x = geometry.x * width_dest / geometry.nw;
 339         int y = geometry.y * height_dest / geometry.nh;
 340
 341         x &= 0xfffffffe;
 342         width_src &= 0xfffffffe;
 343
 344         // optimization points - no work to do
 345         if ( width_src <= 0 || height_src <= 0 )
 346                 return ret;
 347
 348         if ( ( x < 0 && -x >= width_src ) || ( y < 0 && -y >= height_src ) )
 349                 return ret;
 350
 351         // crop overlay off the left edge of frame
 352         if ( x < 0 )
 353         {
 354                 x_src = -x;
 355                 width_src -= x_src;
 356                 x = 0;
 357         }
 358
 359         // crop overlay beyond right edge of frame
 360         else if ( x + width_src > width_dest )
 361                 width_src = width_dest - x;
 362
 363         // crop overlay off the top edge of the frame
 364         if ( y < 0 )
 365         {
 366                 y_src = -y;
 367                 height_src -= y_src;
 368         }
 369         // crop overlay below bottom edge of frame
 370         else if ( y + height_src > height_dest )
 371                 height_src = height_dest - y;
 372
 373         // offset pointer into overlay buffer based on cropping
 374         p_src += x_src * bpp + y_src * stride_src;
 375
 376         // offset pointer into frame buffer based upon positive coordinates only!
 377         p_dest += ( x < 0 ? 0 : x ) * bpp + ( y < 0 ? 0 : y ) * stride_dest;
 378
 379         // offset pointer into alpha channel based upon cropping
 380         if ( p_alpha )
 381                 p_alpha += x_src + y_src * stride_src / bpp;
 382
 383         // Assuming lower field first
 384         // Special care is taken to make sure the b_frame is aligned to the correct field.
 385         // field 0 = lower field and y should be odd (y is 0-based).
 386         // field 1 = upper field and y should be even.
 387         if ( ( field > -1 ) && ( y % 2 == field ) )
 388         {
 389                 //fprintf( stderr, "field %d y %d\n", field, y );
 390                 if ( ( field == 1 && y < height_dest - 1 ) || ( field == 0 && y == 0 ) )
 391                         p_dest += stride_dest;
 392                 else
 393                         p_dest -= stride_dest;
 394         }
 395
 396         // On the second field, use the other lines from b_frame
 397         if ( field == 1 )
 398         {
 399                 p_src += stride_src;
 400                 if ( p_alpha )
 401                         p_alpha += stride_src / bpp;
 402                 height_src--;
 403         }
 404
 405         uint8_t *p = p_src;
 406         uint8_t *q = p_dest;
 407         uint8_t *o = p_dest;
 408         uint8_t *z = p_alpha;
 409
 410         uint8_t a;
 411         int32_t value;
 412         int step = ( field > -1 ) ? 2 : 1;
 413
 414         stride_src = stride_src * step;
 415         int alpha_stride = stride_src / bpp;
 416         stride_dest = stride_dest * step;
 417
 418         // now do the compositing only to cropped extents
 419         for ( i = 0; i < height_src; i += step )
 420         {
 421                 p = p_src;
 422                 q = p_dest;
 423                 o = q;
 424                 z = p_alpha;
 425
 426                 for ( j = 0; j < width_src; j ++ )
 427                 {
 428                         a = ( z == NULL ) ? 255 : *z ++;
 429                         value = ( weight * ( a + 1 ) ) >> 8;
 430                         *o ++ = ( *p++ * value + *q++ * ( ( 1 << 16 ) - value ) ) >> 16;
 431                         *o ++ = ( *p++ * value + *q++ * ( ( 1 << 16 ) - value ) ) >> 16;
 432                 }
 433
 434                 p_src += stride_src;
 435                 p_dest += stride_dest;
 436                 if ( p_alpha )
 437                         p_alpha += alpha_stride;
 438         }
 439
 440         return ret;
 441 }
 442
 443
 444 /** Get the properly sized image from b_frame.
 445 */
 446
 447 static int get_b_frame_image( mlt_transition this, mlt_frame b_frame, uint8_t **image, int *width, int *height, struct geometry_s *geometry )
 448 {
 449         int ret = 0;
 450         mlt_image_format format = mlt_image_yuv422;
 451
 452         // Get the properties objects
 453         mlt_properties b_props = mlt_frame_properties( b_frame );
 454         mlt_properties properties = mlt_transition_properties( this );
 455
 456         if ( mlt_properties_get( properties, "distort" ) == NULL && geometry->distort == 0 )
 457         {
 458                 // Adjust b_frame pixel aspect
 459                 int normalised_width = geometry->w;
 460                 int normalised_height = geometry->h;
 461                 int real_width = get_value( b_props, "real_width", "width" );
 462                 int real_height = get_value( b_props, "real_height", "height" );
 463                 double input_ar = mlt_frame_get_aspect_ratio( b_frame );
 464                 double output_ar = mlt_properties_get_double( b_props, "consumer_aspect_ratio" );
 465                 int scaled_width = real_width;
 466                 int scaled_height = real_height;
 467                 double output_sar = ( double ) geometry->nw / geometry->nh / output_ar;
 468
 469                 // If the output is fat pixels (NTSC) then stretch our input horizontally
 470                 // derived from: output_sar / input_sar * real_width
 471                 scaled_width = output_sar * real_height * input_ar;
 472
 473                 // Now ensure that our images fit in the normalised frame
 474                 if ( scaled_width > normalised_width )
 475                 {
 476                         scaled_height = scaled_height * normalised_width / scaled_width;
 477                         scaled_width = normalised_width;
 478                 }
 479                 if ( scaled_height > normalised_height )
 480                 {
 481                         scaled_width = scaled_width * normalised_height / scaled_height;
 482                         scaled_height = normalised_height;
 483                 }
 484
 485                 // Now apply the fill
 486                 // TODO: Should combine fill/distort in one property
 487                 if ( mlt_properties_get( properties, "fill" ) != NULL )
 488                 {
 489                         scaled_width = ( geometry->w / scaled_width ) * scaled_width;
 490                         scaled_height = ( geometry->h / scaled_height ) * scaled_height;
 491                 }
 492
 493                 // Save the new scaled dimensions
 494                 geometry->sw = scaled_width;
 495                 geometry->sh = scaled_height;
 496         }
 497         else
 498         {
 499                 geometry->sw = geometry->w;
 500                 geometry->sh = geometry->h;
 501         }
 502
 503         // We want to ensure that we bypass resize now...
 504         mlt_properties_set( b_props, "distort", "true" );
 505
 506         // Take into consideration alignment for optimisation
 507         alignment_calculate( geometry );
 508
 509         // Adjust to consumer scale
 510         int x = geometry->x * *width / geometry->nw;
 511         int y = geometry->y * *height / geometry->nh;
 512         *width = geometry->sw * *width / geometry->nw;
 513         *height = geometry->sh * *height / geometry->nh;
 514
 515         x -= x % 2;
 516
 517         // optimization points - no work to do
 518         if ( *width <= 0 || *height <= 0 )
 519                 return 1;
 520
 521         if ( ( x < 0 && -x >= *width ) || ( y < 0 && -y >= *height ) )
 522                 return 1;
 523
 524         ret = mlt_frame_get_image( b_frame, image, &format, width, height, 1 );
 525
 526         return ret;
 527 }
 528
 529
 530 struct geometry_s *composite_calculate( struct geometry_s *result, mlt_transition this, mlt_frame a_frame, float position )
 531 {
 532         // Get the properties from the transition
 533         mlt_properties properties = mlt_transition_properties( this );
 534
 535         // Get the properties from the frame
 536         mlt_properties a_props = mlt_frame_properties( a_frame );
 537
 538         // Structures for geometry
 539         struct geometry_s *start = mlt_properties_get_data( properties, "geometries", NULL );
 540
 541         // Now parse the geometries
 542         if ( start == NULL )
 543         {
 544                 // Obtain the normalised width and height from the a_frame
 545                 int normalised_width = mlt_properties_get_int( a_props, "normalised_width" );
 546                 int normalised_height = mlt_properties_get_int( a_props, "normalised_height" );
 547
 548                 // Parse the transitions properties
 549                 start = transition_parse_keys( this, normalised_width, normalised_height );
 550         }
 551
 552         // Do the calculation
 553         geometry_calculate( result, start, position );
 554
 555         // Now parse the alignment
 556         result->halign = alignment_parse( mlt_properties_get( properties, "halign" ) );
 557         result->valign = alignment_parse( mlt_properties_get( properties, "valign" ) );
 558
 559         return start;
 560 }
 561
 562 mlt_frame composite_copy_region( mlt_transition this, mlt_frame a_frame, mlt_position frame_position )
 563 {
 564         // Create a frame to return
 565         mlt_frame b_frame = mlt_frame_init( );
 566
 567         // Get the properties of the a frame
 568         mlt_properties a_props = mlt_frame_properties( a_frame );
 569
 570         // Get the properties of the b frame
 571         mlt_properties b_props = mlt_frame_properties( b_frame );
 572
 573         // Get the position
 574         float position = position_calculate( this, frame_position );
 575
 576         // Destination image
 577         uint8_t *dest = NULL;
 578
 579         // Get the image and dimensions
 580         uint8_t *image = mlt_properties_get_data( a_props, "image", NULL );
 581         int width = mlt_properties_get_int( a_props, "width" );
 582         int height = mlt_properties_get_int( a_props, "height" );
 583
 584         // Pointers for copy operation
 585         uint8_t *p;
 586         uint8_t *q;
 587         uint8_t *r;
 588
 589         // Corrdinates
 590         int w = 0;
 591         int h = 0;
 592         int x = 0;
 593         int y = 0;
 594
 595         // Will need to know region to copy
 596         struct geometry_s result;
 597
 598         // Calculate the region now
 599         composite_calculate( &result, this, a_frame, position );
 600
 601         // Need to scale down to actual dimensions
 602         x = result.x * width / result.nw ;
 603         y = result.y * height / result.nh;
 604         w = result.w * width / result.nw;
 605         h = result.h * height / result.nh;
 606
 607         x &= 0xfffffffe;
 608         w &= 0xfffffffe;
 609
 610         // Now we need to create a new destination image
 611         dest = mlt_pool_alloc( w * h * 2 );
 612
 613         // Copy the region of the image
 614         p = image + y * width * 2 + x * 2;
 615         q = dest;
 616         r = dest + w * h * 2;
 617
 618         while ( q < r )
 619         {
 620                 memcpy( q, p, w * 2 );
 621                 q += w * 2;
 622                 p += width * 2;
 623         }
 624
 625         // Assign to the new frame
 626         mlt_properties_set_data( b_props, "image", dest, w * h * 2, mlt_pool_release, NULL );
 627         mlt_properties_set_int( b_props, "width", w );
 628         mlt_properties_set_int( b_props, "height", h );
 629
 630         // Assign this position to the b frame
 631         mlt_frame_set_position( b_frame, frame_position );
 632
 633         // Return the frame
 634         return b_frame;
 635 }
 636
 637 /** Get the image.
 638 */
 639
 640 static int transition_get_image( mlt_frame a_frame, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
 641 {
 642         // Get the b frame from the stack
 643         mlt_frame b_frame = mlt_frame_pop_frame( a_frame );
 644
 645         // Get the transition from the a frame
 646         mlt_transition this = mlt_frame_pop_service( a_frame );
 647
 648         // This compositer is yuv422 only
 649         *format = mlt_image_yuv422;
 650
 651         // Get the image from the a frame
 652         mlt_frame_get_image( a_frame, image, format, width, height, 1 );
 653
 654         if ( b_frame != NULL )
 655         {
 656                 // Get the properties of the a frame
 657                 mlt_properties a_props = mlt_frame_properties( a_frame );
 658
 659                 // Get the properties of the b frame
 660                 mlt_properties b_props = mlt_frame_properties( b_frame );
 661
 662                 // Get the properties from the transition
 663                 mlt_properties properties = mlt_transition_properties( this );
 664
 665                 // Structures for geometry
 666                 struct geometry_s result;
 667
 668                 // Calculate the position
 669                 float position = mlt_properties_get_double( b_props, "relative_position" );
 670                 float delta = delta_calculate( this, a_frame );
 671
 672                 // Do the calculation
 673                 struct geometry_s *start = composite_calculate( &result, this, a_frame, position );
 674
 675                 // Since we are the consumer of the b_frame, we must pass along these
 676                 // consumer properties from the a_frame
 677                 mlt_properties_set_double( b_props, "consumer_aspect_ratio", mlt_properties_get_double( a_props, "consumer_aspect_ratio" ) );
 678                 mlt_properties_set_double( b_props, "consumer_scale", mlt_properties_get_double( a_props, "consumer_scale" ) );
 679
 680                 // Get the image from the b frame
 681                 uint8_t *image_b = NULL;
 682                 int width_b = *width;
 683                 int height_b = *height;
 684
 685                 if ( get_b_frame_image( this, b_frame, &image_b, &width_b, &height_b, &result ) == 0 )
 686                 {
 687                         uint8_t *dest = *image;
 688                         uint8_t *src = image_b;
 689                         int bpp = 2;
 690                         uint8_t *alpha = mlt_frame_get_alpha_mask( b_frame );
 691                         int progressive = mlt_properties_get_int( a_props, "progressive" ) ||
 692                                         mlt_properties_get_int( a_props, "consumer_progressive" ) ||
 693                                         mlt_properties_get_int( properties, "progressive" );
 694                         int field;
 695
 696                         for ( field = 0; field < ( progressive ? 1 : 2 ); field++ )
 697                         {
 698                                 // Assume lower field (0) first
 699                                 float field_position = position + field * delta;
 700
 701                                 // Do the calculation if we need to
 702                                 geometry_calculate( &result, start, field_position );
 703
 704                                 // Align
 705                                 alignment_calculate( &result );
 706
 707                                 // Composite the b_frame on the a_frame
 708                                 composite_yuv( dest, *width, *height, bpp, src, width_b, height_b, alpha, result, progressive ? -1 : field );
 709                         }
 710                 }
 711         }
 712
 713         return 0;
 714 }
 715
 716 /** Composition transition processing.
 717 */
 718
 719 static mlt_frame composite_process( mlt_transition this, mlt_frame a_frame, mlt_frame b_frame )
 720 {
 721         // Propogate the transition properties to the b frame
 722         mlt_properties_set_double( mlt_frame_properties( b_frame ), "relative_position", position_calculate( this, mlt_frame_get_position( a_frame ) ) );
 723         mlt_frame_push_service( a_frame, this );
 724         mlt_frame_push_get_image( a_frame, transition_get_image );
 725         mlt_frame_push_frame( a_frame, b_frame );
 726         return a_frame;
 727 }
 728
 729 /** Constructor for the filter.
 730 */
 731
 732 mlt_transition transition_composite_init( char *arg )
 733 {
 734         mlt_transition this = calloc( sizeof( struct mlt_transition_s ), 1 );
 735         if ( this != NULL && mlt_transition_init( this, NULL ) == 0 )
 736         {
 737                 this->process = composite_process;
 738                 mlt_properties_set( mlt_transition_properties( this ), "start", arg != NULL ? arg : "85%,5%:10%x10%" );
 739         }
 740         return this;
 741 }
 742