research.m1stereo.tv/gitweb/ - melted/blob - src/framework/mlt_frame.c

   1 /*
   2  * mlt_frame.c -- interface for all frame classes
   3  * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
   4  * Author: Charles Yates <charles.yates@pandora.be>
   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 "config.h"
  22 #include "mlt_frame.h"
  23 #include "mlt_producer.h"
  24 #include "mlt_factory.h"
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28
  29 /** Constructor for a frame.
  30 */
  31
  32 mlt_frame mlt_frame_init( )
  33 {
  34         // Allocate a frame
  35         mlt_frame this = calloc( sizeof( struct mlt_frame_s ), 1 );
  36
  37         if ( this != NULL )
  38         {
  39                 // Get the normalisation
  40                 char *normalisation = mlt_environment( "MLT_NORMALISATION" );
  41
  42                 // Initialise the properties
  43                 mlt_properties properties = &this->parent;
  44                 mlt_properties_init( properties, this );
  45
  46                 // Set default properties on the frame
  47                 mlt_properties_set_position( properties, "_position", 0.0 );
  48                 mlt_properties_set_data( properties, "image", NULL, 0, NULL, NULL );
  49
  50                 if ( normalisation == NULL || strcmp( normalisation, "NTSC" ) )
  51                 {
  52                         mlt_properties_set_int( properties, "width", 720 );
  53                         mlt_properties_set_int( properties, "height", 576 );
  54                         mlt_properties_set_int( properties, "normalised_width", 720 );
  55                         mlt_properties_set_int( properties, "normalised_height", 576 );
  56                         mlt_properties_set_double( properties, "aspect_ratio", 72.0/79.0 );
  57                 }
  58                 else
  59                 {
  60                         mlt_properties_set_int( properties, "width", 720 );
  61                         mlt_properties_set_int( properties, "height", 480 );
  62                         mlt_properties_set_int( properties, "normalised_width", 720 );
  63                         mlt_properties_set_int( properties, "normalised_height", 480 );
  64                         mlt_properties_set_double( properties, "aspect_ratio", 128.0/117.0 );
  65                 }
  66
  67                 mlt_properties_set_data( properties, "audio", NULL, 0, NULL, NULL );
  68                 mlt_properties_set_data( properties, "alpha", NULL, 0, NULL, NULL );
  69
  70                 // Construct stacks for frames and methods
  71                 this->stack_image = mlt_deque_init( );
  72                 this->stack_audio = mlt_deque_init( );
  73         }
  74
  75         return this;
  76 }
  77
  78 /** Fetch the frames properties.
  79 */
  80
  81 mlt_properties mlt_frame_properties( mlt_frame this )
  82 {
  83         return &this->parent;
  84 }
  85
  86 /** Check if we have a way to derive something other than a test card.
  87 */
  88
  89 int mlt_frame_is_test_card( mlt_frame this )
  90 {
  91         return mlt_deque_count( this->stack_image ) == 0 || mlt_properties_get_int( mlt_frame_properties( this ), "test_image" );
  92 }
  93
  94 /** Check if we have a way to derive something than test audio.
  95 */
  96
  97 int mlt_frame_is_test_audio( mlt_frame this )
  98 {
  99         return this->get_audio == NULL || mlt_properties_get_int( mlt_frame_properties( this ), "test_audio" );
 100 }
 101
 102 /** Get the aspect ratio of the frame.
 103 */
 104
 105 double mlt_frame_get_aspect_ratio( mlt_frame this )
 106 {
 107         return mlt_properties_get_double( mlt_frame_properties( this ), "aspect_ratio" );
 108 }
 109
 110 /** Set the aspect ratio of the frame.
 111 */
 112
 113 int mlt_frame_set_aspect_ratio( mlt_frame this, double value )
 114 {
 115         return mlt_properties_set_double( mlt_frame_properties( this ), "aspect_ratio", value );
 116 }
 117
 118 /** Get the position of this frame.
 119 */
 120
 121 mlt_position mlt_frame_get_position( mlt_frame this )
 122 {
 123         return mlt_properties_get_position( mlt_frame_properties( this ), "_position" );
 124 }
 125
 126 /** Set the position of this frame.
 127 */
 128
 129 int mlt_frame_set_position( mlt_frame this, mlt_position value )
 130 {
 131         return mlt_properties_set_position( mlt_frame_properties( this ), "_position", value );
 132 }
 133
 134 /** Stack a get_image callback.
 135 */
 136
 137 int mlt_frame_push_get_image( mlt_frame this, mlt_get_image get_image )
 138 {
 139         return mlt_deque_push_back( this->stack_image, get_image );
 140 }
 141
 142 /** Pop a get_image callback.
 143 */
 144
 145 mlt_get_image mlt_frame_pop_get_image( mlt_frame this )
 146 {
 147         return mlt_deque_pop_back( this->stack_image );
 148 }
 149
 150 /** Push a frame.
 151 */
 152
 153 int mlt_frame_push_frame( mlt_frame this, mlt_frame that )
 154 {
 155         return mlt_deque_push_back( this->stack_image, that );
 156 }
 157
 158 /** Pop a frame.
 159 */
 160
 161 mlt_frame mlt_frame_pop_frame( mlt_frame this )
 162 {
 163         return mlt_deque_pop_back( this->stack_image );
 164 }
 165
 166 /** Push a service.
 167 */
 168
 169 int mlt_frame_push_service( mlt_frame this, void *that )
 170 {
 171         return mlt_deque_push_back( this->stack_image, that );
 172 }
 173
 174 /** Pop a service.
 175 */
 176
 177 void *mlt_frame_pop_service( mlt_frame this )
 178 {
 179         return mlt_deque_pop_back( this->stack_image );
 180 }
 181
 182 /** Push an audio item on the stack.
 183 */
 184
 185 int mlt_frame_push_audio( mlt_frame this, void *that )
 186 {
 187         return mlt_deque_push_back( this->stack_audio, that );
 188 }
 189
 190 /** Pop an audio item from the stack
 191 */
 192
 193 void *mlt_frame_pop_audio( mlt_frame this )
 194 {
 195         return mlt_deque_pop_back( this->stack_audio );
 196 }
 197
 198 int mlt_frame_get_image( mlt_frame this, uint8_t **buffer, mlt_image_format *format, int *width, int *height, int writable )
 199 {
 200         mlt_properties properties = mlt_frame_properties( this );
 201         mlt_get_image get_image = mlt_frame_pop_get_image( this );
 202         mlt_producer producer = mlt_properties_get_data( properties, "test_card_producer", NULL );
 203
 204         if ( get_image != NULL )
 205         {
 206                 return get_image( this, buffer, format, width, height, writable );
 207         }
 208         else if ( mlt_properties_get_data( properties, "image", NULL ) != NULL )
 209         {
 210                 *format = mlt_image_yuv422;
 211                 *buffer = mlt_properties_get_data( properties, "image", NULL );
 212                 *width = mlt_properties_get_int( properties, "width" );
 213                 *height = mlt_properties_get_int( properties, "height" );
 214         }
 215         else if ( producer != NULL )
 216         {
 217                 mlt_frame test_frame = NULL;
 218                 mlt_service_get_frame( mlt_producer_service( producer ), &test_frame, 0 );
 219                 if ( test_frame != NULL )
 220                 {
 221                         mlt_properties test_properties = mlt_frame_properties( test_frame );
 222                         mlt_properties_pass( properties, test_properties, "" );
 223                         mlt_frame_get_image( test_frame, buffer, format, width, height, writable );
 224                         mlt_properties_set_data( properties, "test_card_frame", test_frame, 0, ( mlt_destructor )mlt_frame_close, NULL );
 225                         mlt_properties_set_data( properties, "image", *buffer, *width * *height * 2, NULL, NULL );
 226                         mlt_properties_set_int( properties, "width", *width );
 227                         mlt_properties_set_int( properties, "height", *height );
 228                         mlt_properties_set( properties, "rescale.interps", "none" );
 229                         mlt_properties_set( properties, "scale", "off" );
 230                 }
 231                 else
 232                 {
 233                         mlt_properties_set_data( properties, "test_card_producer", NULL, 0, NULL, NULL );
 234                         mlt_frame_get_image( this, buffer, format, width, height, writable );
 235                 }
 236         }
 237         else
 238         {
 239                 uint8_t *p;
 240                 uint8_t *q;
 241                 int size = 0;
 242
 243                 *width = *width == 0 ? 720 : *width;
 244                 *height = *height == 0 ? 576 : *height;
 245                 size = *width * *height;
 246
 247                 mlt_properties_set_int( properties, "width", *width );
 248                 mlt_properties_set_int( properties, "height", *height );
 249                 mlt_properties_set_int( properties, "aspect_ratio", 1 );
 250
 251                 switch( *format )
 252                 {
 253                         case mlt_image_none:
 254                                 size = 0;
 255                                 *buffer = NULL;
 256                                 break;
 257                         case mlt_image_rgb24:
 258                                 size *= 3;
 259                                 size += *width * 3;
 260                                 *buffer = mlt_pool_alloc( size );
 261                                 if ( *buffer )
 262                                         memset( *buffer, 255, size );
 263                                 break;
 264                         case mlt_image_rgb24a:
 265                                 size *= 4;
 266                                 size += *width * 4;
 267                                 *buffer = mlt_pool_alloc( size );
 268                                 if ( *buffer )
 269                                         memset( *buffer, 255, size );
 270                                 break;
 271                         case mlt_image_yuv422:
 272                                 size *= 2;
 273                                 size += *width * 2;
 274                                 *buffer = mlt_pool_alloc( size );
 275                                 p = *buffer;
 276                                 q = p + size;
 277                                 while ( p != NULL && p != q )
 278                                 {
 279                                         *p ++ = 235;
 280                                         *p ++ = 128;
 281                                 }
 282                                 break;
 283                         case mlt_image_yuv420p:
 284                                 size = size * 3 / 2;
 285                                 *buffer = mlt_pool_alloc( size );
 286                                 if ( *buffer )
 287                                         memset( *buffer, 255, size );
 288                                 break;
 289                 }
 290
 291                 mlt_properties_set_data( properties, "image", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
 292                 mlt_properties_set_int( properties, "test_image", 1 );
 293         }
 294
 295         return 0;
 296 }
 297
 298 uint8_t *mlt_frame_get_alpha_mask( mlt_frame this )
 299 {
 300         if ( this->get_alpha_mask != NULL )
 301                 return this->get_alpha_mask( this );
 302         return NULL;
 303 }
 304
 305 int mlt_frame_get_audio( mlt_frame this, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
 306 {
 307         mlt_properties properties = mlt_frame_properties( this );
 308
 309         if ( this->get_audio != NULL )
 310         {
 311                 return this->get_audio( this, buffer, format, frequency, channels, samples );
 312         }
 313         else
 314         {
 315                 int size = 0;
 316                 *samples = *samples <= 0 ? 1920 : *samples;
 317                 *channels = *channels <= 0 ? 2 : *channels;
 318                 *frequency = *frequency <= 0 ? 48000 : *frequency;
 319                 size = *samples * *channels * sizeof( int16_t );
 320                 *buffer = mlt_pool_alloc( size );
 321                 if ( *buffer != NULL )
 322                         memset( *buffer, 0, size );
 323                 mlt_properties_set_data( properties, "audio", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
 324                 mlt_properties_set_int( properties, "test_audio", 1 );
 325         }
 326         return 0;
 327 }
 328
 329 void mlt_frame_close( mlt_frame this )
 330 {
 331         if ( this != NULL )
 332         {
 333                 mlt_deque_close( this->stack_image );
 334                 mlt_deque_close( this->stack_audio );
 335                 mlt_properties_close( &this->parent );
 336                 free( this );
 337         }
 338 }
 339
 340 /***** convenience functions *****/
 341
 342 int mlt_convert_rgb24a_to_yuv422( uint8_t *rgba, int width, int height, int stride, uint8_t *yuv, uint8_t *alpha )
 343 {
 344         int ret = 0;
 345         register int y0, y1, u0, u1, v0, v1;
 346         register int r, g, b;
 347         register uint8_t *d = yuv;
 348         register int i, j;
 349
 350         for ( i = 0; i < height; i++ )
 351         {
 352                 register uint8_t *s = rgba + ( stride * i );
 353                 for ( j = 0; j < ( width / 2 ); j++ )
 354                 {
 355                         r = *s++;
 356                         g = *s++;
 357                         b = *s++;
 358                         *alpha++ = *s++;
 359                         RGB2YUV (r, g, b, y0, u0 , v0);
 360                         r = *s++;
 361                         g = *s++;
 362                         b = *s++;
 363                         *alpha++ = *s++;
 364                         RGB2YUV (r, g, b, y1, u1 , v1);
 365                         *d++ = y0;
 366                         *d++ = (u0+u1) >> 1;
 367                         *d++ = y1;
 368                         *d++ = (v0+v1) >> 1;
 369                 }
 370                 if ( width % 2 )
 371                 {
 372                         r = *s++;
 373                         g = *s++;
 374                         b = *s++;
 375                         *alpha++ = *s++;
 376                         RGB2YUV (r, g, b, y0, u0 , v0);
 377                         *d++ = y0;
 378                         *d++ = u0;
 379                 }
 380         }
 381         return ret;
 382 }
 383
 384 int mlt_convert_rgb24_to_yuv422( uint8_t *rgb, int width, int height, int stride, uint8_t *yuv )
 385 {
 386         int ret = 0;
 387         register int y0, y1, u0, u1, v0, v1;
 388         register int r, g, b;
 389         register uint8_t *d = yuv;
 390         register int i, j;
 391
 392         for ( i = 0; i < height; i++ )
 393         {
 394                 register uint8_t *s = rgb + ( stride * i );
 395                 for ( j = 0; j < ( width / 2 ); j++ )
 396                 {
 397                         r = *s++;
 398                         g = *s++;
 399                         b = *s++;
 400                         RGB2YUV (r, g, b, y0, u0 , v0);
 401                         r = *s++;
 402                         g = *s++;
 403                         b = *s++;
 404                         RGB2YUV (r, g, b, y1, u1 , v1);
 405                         *d++ = y0;
 406                         *d++ = (u0+u1) >> 1;
 407                         *d++ = y1;
 408                         *d++ = (v0+v1) >> 1;
 409                 }
 410                 if ( width % 2 )
 411                 {
 412                         r = *s++;
 413                         g = *s++;
 414                         b = *s++;
 415                         RGB2YUV (r, g, b, y0, u0 , v0);
 416                         *d++ = y0;
 417                         *d++ = u0;
 418                 }
 419         }
 420         return ret;
 421 }
 422
 423 int mlt_convert_yuv420p_to_yuv422( uint8_t *yuv420p, int width, int height, int stride, uint8_t *yuv )
 424 {
 425         int ret = 0;
 426         register int i, j;
 427
 428         int half = width >> 1;
 429
 430         uint8_t *Y = yuv420p;
 431         uint8_t *U = Y + width * height;
 432         uint8_t *V = U + width * height / 4;
 433
 434         register uint8_t *d = yuv;
 435
 436         for ( i = 0; i < height; i++ )
 437         {
 438                 register uint8_t *u = U + ( i / 2 ) * ( half );
 439                 register uint8_t *v = V + ( i / 2 ) * ( half );
 440
 441                 for ( j = 0; j < half; j++ )
 442                 {
 443                         *d ++ = *Y ++;
 444                         *d ++ = *u ++;
 445                         *d ++ = *Y ++;
 446                         *d ++ = *v ++;
 447                 }
 448         }
 449         return ret;
 450 }
 451
 452 void mlt_resize_yuv422( uint8_t *output, int owidth, int oheight, uint8_t *input, int iwidth, int iheight )
 453 {
 454         // Calculate strides
 455         int istride = iwidth * 2;
 456         int ostride = owidth * 2;
 457
 458         iwidth = iwidth - ( iwidth % 4 );
 459         owidth = owidth - ( owidth % 4 );
 460         iheight = iheight - ( iheight % 2 );
 461         oheight = oheight - ( oheight % 2 );
 462
 463         // Optimisation point
 464         if ( iwidth == owidth && iheight == oheight )
 465                 memcpy( output, input, iheight * istride );
 466
 467         // Coordinates (0,0 is middle of output)
 468         int y;
 469
 470         // Calculate ranges
 471         int out_x_range = owidth / 2;
 472         int out_y_range = oheight / 2;
 473         int in_x_range = iwidth / 2 < out_x_range ? iwidth / 2 : out_x_range;
 474         int in_y_range = iheight / 2 < out_y_range ? iheight / 2 : out_y_range;
 475
 476         // Output pointers
 477         uint8_t *out_line = output;
 478         uint8_t *out_ptr = out_line;
 479
 480         // Calculate a middle and possibly invalid pointer in the input
 481         uint8_t *in_middle = input + istride * ( iheight / 2 ) + ( iwidth / 2 ) * 2;
 482         int in_line = - in_y_range * istride - in_x_range * 2;
 483
 484         int elements;
 485
 486         // Fill whole section with black
 487         y = out_y_range - ( iheight / 2 );
 488         int blank_elements = ostride * y / 2;
 489         elements = blank_elements;
 490         while ( elements -- )
 491         {
 492                 *out_line ++ = 16;
 493                 *out_line ++ = 128;
 494         }
 495
 496         int active_width = 2 * iwidth;
 497         int inactive_width = out_x_range - in_x_range;
 498         uint8_t *p = NULL;
 499         uint8_t *end = NULL;
 500
 501         // Loop for the entirety of our output height.
 502         while ( iheight -- )
 503         {
 504         // Start at the beginning of the line
 505         out_ptr = out_line;
 506
 507                 // Fill the outer part with black
 508                 elements = inactive_width;
 509                 while ( elements -- )
 510                 {
 511                         *out_ptr ++ = 16;
 512                         *out_ptr ++ = 128;
 513                 }
 514
 515                 // We're in the input range for this row.
 516                 p = in_middle + in_line;
 517                 end = out_ptr + active_width;
 518                 while ( out_ptr != end )
 519                 {
 520                         *out_ptr ++ = *p ++;
 521                         *out_ptr ++ = *p ++;
 522                 }
 523
 524                 // Fill the outer part with black
 525                 elements = inactive_width;
 526                 while ( elements -- )
 527                 {
 528                         *out_ptr ++ = 16;
 529                         *out_ptr ++ = 128;
 530                 }
 531
 532                 // Move to next input line
 533                 in_line += istride;
 534
 535         // Move to next output line
 536         out_line += ostride;
 537         }
 538
 539         // Fill whole section with black
 540         elements = blank_elements;
 541         while ( elements -- )
 542         {
 543                 *out_line ++ = 16;
 544                 *out_line ++ = 128;
 545         }
 546 }
 547
 548 /** A resizing function for yuv422 frames - this does not rescale, but simply
 549         resizes. It assumes yuv422 images available on the frame so use with care.
 550 */
 551
 552 uint8_t *mlt_frame_resize_yuv422( mlt_frame this, int owidth, int oheight )
 553 {
 554         // Get properties
 555         mlt_properties properties = mlt_frame_properties( this );
 556
 557         // Get the input image, width and height
 558         uint8_t *input = mlt_properties_get_data( properties, "image", NULL );
 559         int iwidth = mlt_properties_get_int( properties, "width" );
 560         int iheight = mlt_properties_get_int( properties, "height" );
 561
 562         // If width and height are correct, don't do anything
 563         if ( iwidth != owidth || iheight != oheight )
 564         {
 565                 // Create the output image
 566                 uint8_t *output = mlt_pool_alloc( owidth * ( oheight + 1 ) * 2 );
 567
 568                 // Call the generic resize
 569                 mlt_resize_yuv422( output, owidth, oheight, input, iwidth, iheight );
 570
 571                 // Now update the frame
 572                 mlt_properties_set_data( properties, "image", output, owidth * ( oheight + 1 ) * 2, ( mlt_destructor )mlt_pool_release, NULL );
 573                 mlt_properties_set_int( properties, "width", owidth );
 574                 mlt_properties_set_int( properties, "height", oheight );
 575
 576                 // Return the output
 577                 return output;
 578         }
 579         // No change, return input
 580         return input;
 581 }
 582
 583 /** A rescaling function for yuv422 frames - low quality, and provided for testing
 584         only. It assumes yuv422 images available on the frame so use with care.
 585 */
 586
 587 uint8_t *mlt_frame_rescale_yuv422( mlt_frame this, int owidth, int oheight )
 588 {
 589         // Get properties
 590         mlt_properties properties = mlt_frame_properties( this );
 591
 592         // Get the input image, width and height
 593         uint8_t *input = mlt_properties_get_data( properties, "image", NULL );
 594         int iwidth = mlt_properties_get_int( properties, "width" );
 595         int iheight = mlt_properties_get_int( properties, "height" );
 596
 597         // If width and height are correct, don't do anything
 598         if ( iwidth != owidth || iheight != oheight )
 599         {
 600                 // Create the output image
 601                 uint8_t *output = mlt_pool_alloc( owidth * ( oheight + 1 ) * 2 );
 602
 603                 // Calculate strides
 604                 int istride = iwidth * 2;
 605                 int ostride = owidth * 2;
 606
 607                 iwidth = iwidth - ( iwidth % 4 );
 608
 609                 // Derived coordinates
 610                 int dy, dx;
 611
 612         // Calculate ranges
 613         int out_x_range = owidth / 2;
 614         int out_y_range = oheight / 2;
 615         int in_x_range = iwidth / 2;
 616         int in_y_range = iheight / 2;
 617
 618         // Output pointers
 619         register uint8_t *out_line = output;
 620         register uint8_t *out_ptr;
 621
 622         // Calculate a middle pointer
 623         uint8_t *in_middle = input + istride * in_y_range + in_x_range * 2;
 624         uint8_t *in_line;
 625
 626                 // Generate the affine transform scaling values
 627                 register int scale_width = ( iwidth << 16 ) / owidth;
 628                 register int scale_height = ( iheight << 16 ) / oheight;
 629                 register int base = 0;
 630
 631                 int outer = out_x_range * scale_width;
 632                 int bottom = out_y_range * scale_height;
 633
 634         // Loop for the entirety of our output height.
 635         for ( dy = - bottom; dy < bottom; dy += scale_height )
 636         {
 637                 // Start at the beginning of the line
 638                 out_ptr = out_line;
 639
 640                 // Pointer to the middle of the input line
 641                 in_line = in_middle + ( dy >> 16 ) * istride;
 642
 643                 // Loop for the entirety of our output row.
 644                 for ( dx = - outer; dx < outer; dx += scale_width )
 645                 {
 646                                 base = dx >> 15;
 647                                 base &= 0xfffffffe;
 648                                 *out_ptr ++ = *( in_line + base );
 649                                 base &= 0xfffffffc;
 650                                 *out_ptr ++ = *( in_line + base + 1 );
 651                                 dx += scale_width;
 652                                 base = dx >> 15;
 653                                 base &= 0xfffffffe;
 654                                 *out_ptr ++ = *( in_line + base );
 655                                 base &= 0xfffffffc;
 656                                 *out_ptr ++ = *( in_line + base + 3 );
 657                 }
 658
 659                 // Move to next output line
 660                 out_line += ostride;
 661         }
 662
 663                 // Now update the frame
 664                 mlt_properties_set_data( properties, "image", output, owidth * ( oheight + 1 ) * 2, ( mlt_destructor )mlt_pool_release, NULL );
 665                 mlt_properties_set_int( properties, "width", owidth );
 666                 mlt_properties_set_int( properties, "height", oheight );
 667
 668                 // Return the output
 669                 return output;
 670         }
 671
 672         // No change, return input
 673         return input;
 674 }
 675
 676 int mlt_frame_mix_audio( mlt_frame this, mlt_frame that, float weight_start, float weight_end, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
 677 {
 678         int ret = 0;
 679         int16_t *src, *dest;
 680         int frequency_src = *frequency, frequency_dest = *frequency;
 681         int channels_src = *channels, channels_dest = *channels;
 682         int samples_src = *samples, samples_dest = *samples;
 683         int i, j;
 684         double d = 0, s = 0;
 685
 686         mlt_frame_get_audio( this, &dest, format, &frequency_dest, &channels_dest, &samples_dest );
 687         //fprintf( stderr, "mix: frame dest samples %d channels %d position %lld\n", samples_dest, channels_dest, mlt_properties_get_position( mlt_frame_properties( this ), "_position" ) );
 688         mlt_frame_get_audio( that, &src, format, &frequency_src, &channels_src, &samples_src );
 689         //fprintf( stderr, "mix: frame src  samples %d channels %d\n", samples_src, channels_src );
 690
 691         if ( channels_src > 6 )
 692                 channels_src = 0;
 693         if ( channels_dest > 6 )
 694                 channels_dest = 0;
 695         if ( samples_src > 4000 )
 696                 samples_src = 0;
 697         if ( samples_dest > 4000 )
 698                 samples_dest = 0;
 699
 700         // determine number of samples to process
 701         *samples = samples_src < samples_dest ? samples_src : samples_dest;
 702         *channels = channels_src < channels_dest ? channels_src : channels_dest;
 703         *buffer = dest;
 704         *frequency = frequency_dest;
 705
 706         // Compute a smooth ramp over start to end
 707         float weight = weight_start;
 708         float weight_step = ( weight_end - weight_start ) / *samples;
 709
 710         // Mixdown
 711         for ( i = 0; i < *samples; i++ )
 712         {
 713                 for ( j = 0; j < *channels; j++ )
 714                 {
 715                         if ( j < channels_dest )
 716                                 d = (double) dest[ i * channels_dest + j ];
 717                         if ( j < channels_src )
 718                                 s = (double) src[ i * channels_src + j ];
 719                         dest[ i * channels_dest + j ] = s * weight + d * ( 1.0 - weight );
 720                 }
 721                 weight += weight_step;
 722         }
 723
 724         return ret;
 725 }
 726
 727 int mlt_sample_calculator( float fps, int frequency, int64_t position )
 728 {
 729         int samples = 0;
 730
 731         if ( fps > 29 && fps <= 30 )
 732         {
 733                 samples = frequency / 30;
 734
 735                 switch ( frequency )
 736                 {
 737                         case 48000:
 738                                 if ( position % 5 != 0 )
 739                                         samples += 2;
 740                                 break;
 741                         case 44100:
 742                                 if ( position % 300 == 0 )
 743                                         samples = 1471;
 744                                 else if ( position % 30 == 0 )
 745                                         samples = 1470;
 746                                 else if ( position % 2 == 0 )
 747                                         samples = 1472;
 748                                 else
 749                                         samples = 1471;
 750                                 break;
 751                         case 32000:
 752                                 if ( position % 30 == 0 )
 753                                         samples = 1068;
 754                                 else if ( position % 29 == 0 )
 755                                         samples = 1067;
 756                                 else if ( position % 4 == 2 )
 757                                         samples = 1067;
 758                                 else
 759                                         samples = 1068;
 760                                 break;
 761                         default:
 762                                 samples = 0;
 763                 }
 764         }
 765         else if ( fps != 0 )
 766         {
 767                 samples = frequency / fps;
 768         }
 769
 770         return samples;
 771 }