1f2f3d216bc4b83a9d48b89c75f0eb96c49b2ab6
[melted] / 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_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_set_double( test_properties, "consumer_aspect_ratio", mlt_properties_get_double( properties, "consumer_aspect_ratio" ) );
223 mlt_properties_set( test_properties, "rescale.interp", "nearest" );
224 mlt_frame_get_image( test_frame, buffer, format, width, height, writable );
225 mlt_properties_set_data( properties, "test_card_frame", test_frame, 0, ( mlt_destructor )mlt_frame_close, NULL );
226 mlt_properties_set_data( properties, "image", *buffer, *width * *height * 2, NULL, NULL );
227 mlt_properties_set_int( properties, "width", *width );
228 mlt_properties_set_int( properties, "height", *height );
229 }
230 else
231 {
232 mlt_properties_set_data( properties, "test_card_producer", NULL, 0, NULL, NULL );
233 mlt_frame_get_image( this, buffer, format, width, height, writable );
234 }
235 }
236 else
237 {
238 uint8_t *p;
239 uint8_t *q;
240 int size = 0;
241
242 *width = *width == 0 ? 720 : *width;
243 *height = *height == 0 ? 576 : *height;
244 size = *width * *height;
245
246 mlt_properties_set_int( properties, "width", *width );
247 mlt_properties_set_int( properties, "height", *height );
248
249 switch( *format )
250 {
251 case mlt_image_none:
252 size = 0;
253 *buffer = NULL;
254 break;
255 case mlt_image_rgb24:
256 size *= 3;
257 size += *width * 3;
258 *buffer = mlt_pool_alloc( size );
259 if ( *buffer )
260 memset( *buffer, 255, size );
261 break;
262 case mlt_image_rgb24a:
263 size *= 4;
264 size += *width * 4;
265 *buffer = mlt_pool_alloc( size );
266 if ( *buffer )
267 memset( *buffer, 255, size );
268 break;
269 case mlt_image_yuv422:
270 size *= 2;
271 size += *width * 2;
272 *buffer = mlt_pool_alloc( size );
273 p = *buffer;
274 q = p + size;
275 while ( p != NULL && p != q )
276 {
277 *p ++ = 235;
278 *p ++ = 128;
279 }
280 break;
281 case mlt_image_yuv420p:
282 size = size * 3 / 2;
283 *buffer = mlt_pool_alloc( size );
284 if ( *buffer )
285 memset( *buffer, 255, size );
286 break;
287 }
288
289 mlt_properties_set_data( properties, "image", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
290 mlt_properties_set_int( properties, "test_image", 1 );
291 }
292
293 return 0;
294 }
295
296 uint8_t *mlt_frame_get_alpha_mask( mlt_frame this )
297 {
298 if ( this->get_alpha_mask != NULL )
299 return this->get_alpha_mask( this );
300 return NULL;
301 }
302
303 int mlt_frame_get_audio( mlt_frame this, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
304 {
305 mlt_properties properties = mlt_frame_properties( this );
306
307 if ( this->get_audio != NULL )
308 {
309 return this->get_audio( this, buffer, format, frequency, channels, samples );
310 }
311 else
312 {
313 int size = 0;
314 *samples = *samples <= 0 ? 1920 : *samples;
315 *channels = *channels <= 0 ? 2 : *channels;
316 *frequency = *frequency <= 0 ? 48000 : *frequency;
317 size = *samples * *channels * sizeof( int16_t );
318 *buffer = mlt_pool_alloc( size );
319 if ( *buffer != NULL )
320 memset( *buffer, 0, size );
321 mlt_properties_set_data( properties, "audio", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
322 mlt_properties_set_int( properties, "test_audio", 1 );
323 }
324 return 0;
325 }
326
327 void mlt_frame_close( mlt_frame this )
328 {
329 if ( this != NULL )
330 {
331 mlt_deque_close( this->stack_image );
332 mlt_deque_close( this->stack_audio );
333 mlt_properties_close( &this->parent );
334 free( this );
335 }
336 }
337
338 /***** convenience functions *****/
339
340 int mlt_convert_rgb24a_to_yuv422( uint8_t *rgba, int width, int height, int stride, uint8_t *yuv, uint8_t *alpha )
341 {
342 int ret = 0;
343 register int y0, y1, u0, u1, v0, v1;
344 register int r, g, b;
345 register uint8_t *d = yuv;
346 register int i, j;
347
348 for ( i = 0; i < height; i++ )
349 {
350 register uint8_t *s = rgba + ( stride * i );
351 for ( j = 0; j < ( width / 2 ); j++ )
352 {
353 r = *s++;
354 g = *s++;
355 b = *s++;
356 *alpha++ = *s++;
357 RGB2YUV (r, g, b, y0, u0 , v0);
358 r = *s++;
359 g = *s++;
360 b = *s++;
361 *alpha++ = *s++;
362 RGB2YUV (r, g, b, y1, u1 , v1);
363 *d++ = y0;
364 *d++ = (u0+u1) >> 1;
365 *d++ = y1;
366 *d++ = (v0+v1) >> 1;
367 }
368 if ( width % 2 )
369 {
370 r = *s++;
371 g = *s++;
372 b = *s++;
373 *alpha++ = *s++;
374 RGB2YUV (r, g, b, y0, u0 , v0);
375 *d++ = y0;
376 *d++ = u0;
377 }
378 }
379 return ret;
380 }
381
382 int mlt_convert_rgb24_to_yuv422( uint8_t *rgb, int width, int height, int stride, uint8_t *yuv )
383 {
384 int ret = 0;
385 register int y0, y1, u0, u1, v0, v1;
386 register int r, g, b;
387 register uint8_t *d = yuv;
388 register int i, j;
389
390 for ( i = 0; i < height; i++ )
391 {
392 register uint8_t *s = rgb + ( stride * i );
393 for ( j = 0; j < ( width / 2 ); j++ )
394 {
395 r = *s++;
396 g = *s++;
397 b = *s++;
398 RGB2YUV (r, g, b, y0, u0 , v0);
399 r = *s++;
400 g = *s++;
401 b = *s++;
402 RGB2YUV (r, g, b, y1, u1 , v1);
403 *d++ = y0;
404 *d++ = (u0+u1) >> 1;
405 *d++ = y1;
406 *d++ = (v0+v1) >> 1;
407 }
408 if ( width % 2 )
409 {
410 r = *s++;
411 g = *s++;
412 b = *s++;
413 RGB2YUV (r, g, b, y0, u0 , v0);
414 *d++ = y0;
415 *d++ = u0;
416 }
417 }
418 return ret;
419 }
420
421 int mlt_convert_yuv420p_to_yuv422( uint8_t *yuv420p, int width, int height, int stride, uint8_t *yuv )
422 {
423 int ret = 0;
424 register int i, j;
425
426 int half = width >> 1;
427
428 uint8_t *Y = yuv420p;
429 uint8_t *U = Y + width * height;
430 uint8_t *V = U + width * height / 4;
431
432 register uint8_t *d = yuv;
433
434 for ( i = 0; i < height; i++ )
435 {
436 register uint8_t *u = U + ( i / 2 ) * ( half );
437 register uint8_t *v = V + ( i / 2 ) * ( half );
438
439 for ( j = 0; j < half; j++ )
440 {
441 *d ++ = *Y ++;
442 *d ++ = *u ++;
443 *d ++ = *Y ++;
444 *d ++ = *v ++;
445 }
446 }
447 return ret;
448 }
449
450 void mlt_resize_yuv422( uint8_t *output, int owidth, int oheight, uint8_t *input, int iwidth, int iheight )
451 {
452 // Calculate strides
453 int istride = iwidth * 2;
454 int ostride = owidth * 2;
455
456 iwidth = iwidth - ( iwidth % 4 );
457 owidth = owidth - ( owidth % 4 );
458 iheight = iheight - ( iheight % 2 );
459 oheight = oheight - ( oheight % 2 );
460
461 // Optimisation point
462 if ( iwidth == owidth && iheight == oheight )
463 memcpy( output, input, iheight * istride );
464
465 // Coordinates (0,0 is middle of output)
466 int y;
467
468 // Calculate ranges
469 int out_x_range = owidth / 2;
470 int out_y_range = oheight / 2;
471 int in_x_range = iwidth / 2 < out_x_range ? iwidth / 2 : out_x_range;
472 int in_y_range = iheight / 2 < out_y_range ? iheight / 2 : out_y_range;
473
474 // Output pointers
475 uint8_t *out_line = output;
476 uint8_t *out_ptr = out_line;
477
478 // Calculate a middle and possibly invalid pointer in the input
479 uint8_t *in_middle = input + istride * ( iheight / 2 ) + ( iwidth / 2 ) * 2;
480 int in_line = - in_y_range * istride - in_x_range * 2;
481
482 int elements;
483
484 // Fill whole section with black
485 y = out_y_range - ( iheight / 2 );
486 int blank_elements = ostride * y / 2;
487 elements = blank_elements;
488 while ( elements -- )
489 {
490 *out_line ++ = 16;
491 *out_line ++ = 128;
492 }
493
494 int active_width = 2 * iwidth;
495 int inactive_width = out_x_range - in_x_range;
496
497 // Loop for the entirety of our output height.
498 while ( iheight -- )
499 {
500 // Start at the beginning of the line
501 out_ptr = out_line;
502
503 // Fill the outer part with black
504 elements = inactive_width;
505 while ( elements -- )
506 {
507 *out_ptr ++ = 16;
508 *out_ptr ++ = 128;
509 }
510
511 // We're in the input range for this row.
512 memcpy( out_ptr, in_middle + in_line, active_width );
513 out_ptr += active_width;
514
515 // Fill the outer part with black
516 elements = inactive_width;
517 while ( elements -- )
518 {
519 *out_ptr ++ = 16;
520 *out_ptr ++ = 128;
521 }
522
523 // Move to next input line
524 in_line += istride;
525
526 // Move to next output line
527 out_line += ostride;
528 }
529
530 // Fill whole section with black
531 elements = blank_elements;
532 while ( elements -- )
533 {
534 *out_line ++ = 16;
535 *out_line ++ = 128;
536 }
537 }
538
539 /** A resizing function for yuv422 frames - this does not rescale, but simply
540 resizes. It assumes yuv422 images available on the frame so use with care.
541 */
542
543 uint8_t *mlt_frame_resize_yuv422( mlt_frame this, int owidth, int oheight )
544 {
545 // Get properties
546 mlt_properties properties = mlt_frame_properties( this );
547
548 // Get the input image, width and height
549 uint8_t *input = mlt_properties_get_data( properties, "image", NULL );
550 int iwidth = mlt_properties_get_int( properties, "width" );
551 int iheight = mlt_properties_get_int( properties, "height" );
552
553 // If width and height are correct, don't do anything
554 if ( iwidth != owidth || iheight != oheight )
555 {
556 // Create the output image
557 uint8_t *output = mlt_pool_alloc( owidth * ( oheight + 1 ) * 2 );
558
559 // Call the generic resize
560 mlt_resize_yuv422( output, owidth, oheight, input, iwidth, iheight );
561
562 // Now update the frame
563 mlt_properties_set_data( properties, "image", output, owidth * ( oheight + 1 ) * 2, ( mlt_destructor )mlt_pool_release, NULL );
564 mlt_properties_set_int( properties, "width", owidth );
565 mlt_properties_set_int( properties, "height", oheight );
566
567 // Return the output
568 return output;
569 }
570 // No change, return input
571 return input;
572 }
573
574 /** A rescaling function for yuv422 frames - low quality, and provided for testing
575 only. It assumes yuv422 images available on the frame so use with care.
576 */
577
578 uint8_t *mlt_frame_rescale_yuv422( mlt_frame this, int owidth, int oheight )
579 {
580 // Get properties
581 mlt_properties properties = mlt_frame_properties( this );
582
583 // Get the input image, width and height
584 uint8_t *input = mlt_properties_get_data( properties, "image", NULL );
585 int iwidth = mlt_properties_get_int( properties, "width" );
586 int iheight = mlt_properties_get_int( properties, "height" );
587
588 // If width and height are correct, don't do anything
589 if ( iwidth != owidth || iheight != oheight )
590 {
591 // Create the output image
592 uint8_t *output = mlt_pool_alloc( owidth * ( oheight + 1 ) * 2 );
593
594 // Calculate strides
595 int istride = iwidth * 2;
596 int ostride = owidth * 2;
597
598 iwidth = iwidth - ( iwidth % 4 );
599
600 // Derived coordinates
601 int dy, dx;
602
603 // Calculate ranges
604 int out_x_range = owidth / 2;
605 int out_y_range = oheight / 2;
606 int in_x_range = iwidth / 2;
607 int in_y_range = iheight / 2;
608
609 // Output pointers
610 register uint8_t *out_line = output;
611 register uint8_t *out_ptr;
612
613 // Calculate a middle pointer
614 uint8_t *in_middle = input + istride * in_y_range + in_x_range * 2;
615 uint8_t *in_line;
616
617 // Generate the affine transform scaling values
618 register int scale_width = ( iwidth << 16 ) / owidth;
619 register int scale_height = ( iheight << 16 ) / oheight;
620 register int base = 0;
621
622 int outer = out_x_range * scale_width;
623 int bottom = out_y_range * scale_height;
624
625 // Loop for the entirety of our output height.
626 for ( dy = - bottom; dy < bottom; dy += scale_height )
627 {
628 // Start at the beginning of the line
629 out_ptr = out_line;
630
631 // Pointer to the middle of the input line
632 in_line = in_middle + ( dy >> 16 ) * istride;
633
634 // Loop for the entirety of our output row.
635 for ( dx = - outer; dx < outer; dx += scale_width )
636 {
637 base = dx >> 15;
638 base &= 0xfffffffe;
639 *out_ptr ++ = *( in_line + base );
640 base &= 0xfffffffc;
641 *out_ptr ++ = *( in_line + base + 1 );
642 dx += scale_width;
643 base = dx >> 15;
644 base &= 0xfffffffe;
645 *out_ptr ++ = *( in_line + base );
646 base &= 0xfffffffc;
647 *out_ptr ++ = *( in_line + base + 3 );
648 }
649
650 // Move to next output line
651 out_line += ostride;
652 }
653
654 // Now update the frame
655 mlt_properties_set_data( properties, "image", output, owidth * ( oheight + 1 ) * 2, ( mlt_destructor )mlt_pool_release, NULL );
656 mlt_properties_set_int( properties, "width", owidth );
657 mlt_properties_set_int( properties, "height", oheight );
658
659 // Return the output
660 return output;
661 }
662
663 // No change, return input
664 return input;
665 }
666
667 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 )
668 {
669 int ret = 0;
670 int16_t *src, *dest;
671 int frequency_src = *frequency, frequency_dest = *frequency;
672 int channels_src = *channels, channels_dest = *channels;
673 int samples_src = *samples, samples_dest = *samples;
674 int i, j;
675 double d = 0, s = 0;
676
677 mlt_frame_get_audio( this, &dest, format, &frequency_dest, &channels_dest, &samples_dest );
678 //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" ) );
679 mlt_frame_get_audio( that, &src, format, &frequency_src, &channels_src, &samples_src );
680 //fprintf( stderr, "mix: frame src samples %d channels %d\n", samples_src, channels_src );
681
682 if ( channels_src > 6 )
683 channels_src = 0;
684 if ( channels_dest > 6 )
685 channels_dest = 0;
686 if ( samples_src > 4000 )
687 samples_src = 0;
688 if ( samples_dest > 4000 )
689 samples_dest = 0;
690
691 // determine number of samples to process
692 *samples = samples_src < samples_dest ? samples_src : samples_dest;
693 *channels = channels_src < channels_dest ? channels_src : channels_dest;
694 *buffer = dest;
695 *frequency = frequency_dest;
696
697 // Compute a smooth ramp over start to end
698 float weight = weight_start;
699 float weight_step = ( weight_end - weight_start ) / *samples;
700
701 // Mixdown
702 for ( i = 0; i < *samples; i++ )
703 {
704 for ( j = 0; j < *channels; j++ )
705 {
706 if ( j < channels_dest )
707 d = (double) dest[ i * channels_dest + j ];
708 if ( j < channels_src )
709 s = (double) src[ i * channels_src + j ];
710 dest[ i * channels_dest + j ] = s * weight + d * ( 1.0 - weight );
711 }
712 weight += weight_step;
713 }
714
715 return ret;
716 }
717
718 int mlt_sample_calculator( float fps, int frequency, int64_t position )
719 {
720 int samples = 0;
721
722 if ( fps > 29 && fps <= 30 )
723 {
724 samples = frequency / 30;
725
726 switch ( frequency )
727 {
728 case 48000:
729 if ( position % 5 != 0 )
730 samples += 2;
731 break;
732 case 44100:
733 if ( position % 300 == 0 )
734 samples = 1471;
735 else if ( position % 30 == 0 )
736 samples = 1470;
737 else if ( position % 2 == 0 )
738 samples = 1472;
739 else
740 samples = 1471;
741 break;
742 case 32000:
743 if ( position % 30 == 0 )
744 samples = 1068;
745 else if ( position % 29 == 0 )
746 samples = 1067;
747 else if ( position % 4 == 2 )
748 samples = 1067;
749 else
750 samples = 1068;
751 break;
752 default:
753 samples = 0;
754 }
755 }
756 else if ( fps != 0 )
757 {
758 samples = frequency / fps;
759 }
760
761 return samples;
762 }