[melted] / src / framework / mlt_frame.c

/*
 * mlt_frame.c -- interface for all frame classes
 * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
 * Author: Charles Yates <charles.yates@pandora.be>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include "config.h"
#include "mlt_frame.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct
{
        mlt_image_format vfmt;
        int width;
        int height;
        uint8_t *image;
        uint8_t *alpha;
        mlt_audio_format afmt;
        int16_t *audio;
}
frame_test;

static frame_test test_card = { mlt_image_none, 0, 0, NULL, NULL, mlt_audio_none, NULL };

/** Constructor for a frame.
*/

mlt_frame mlt_frame_init( )
{
        // Allocate a frame
        mlt_frame this = calloc( sizeof( struct mlt_frame_s ), 1 );

        if ( this != NULL )
        {
                // Initialise the properties
                mlt_properties properties = &this->parent;
                mlt_properties_init( properties, this );

                // Set default properties on the frame
                mlt_properties_set_position( properties, "position", 0.0 );
                mlt_properties_set_data( properties, "image", NULL, 0, NULL, NULL );
                mlt_properties_set_int( properties, "width", 720 );
                mlt_properties_set_int( properties, "height", 576 );
                mlt_properties_set_double( properties, "aspect_ratio", 4.0 / 3.0 );
                mlt_properties_set_data( properties, "audio", NULL, 0, NULL, NULL );
                mlt_properties_set_data( properties, "alpha", NULL, 0, NULL, NULL );
        }
        return this;
}

/** Fetch the frames properties.
*/

mlt_properties mlt_frame_properties( mlt_frame this )
{
        return &this->parent;
}

/** Check if we have a way to derive something other than a test card.
*/

int mlt_frame_is_test_card( mlt_frame this )
{
        return this->stack_get_image_size == 0;
}

/** Get the aspect ratio of the frame.
*/

double mlt_frame_get_aspect_ratio( mlt_frame this )
{
        mlt_properties properties = mlt_frame_properties( this );
        return mlt_properties_get_double( properties, "aspect_ratio" );
}

/** Set the aspect ratio of the frame.
*/

int mlt_frame_set_aspect_ratio( mlt_frame this, double value )
{
        mlt_properties properties = mlt_frame_properties( this );
        return mlt_properties_set_double( properties, "aspect_ratio", value );
}

/** Get the position of this frame.
*/

mlt_position mlt_frame_get_position( mlt_frame this )
{
        mlt_properties properties = mlt_frame_properties( this );
        return mlt_properties_get_position( properties, "position" );
}

/** Set the position of this frame.
*/

int mlt_frame_set_position( mlt_frame this, mlt_position value )
{
        mlt_properties properties = mlt_frame_properties( this );
        return mlt_properties_set_position( properties, "position", value );
}

/** Stack a get_image callback.
*/

int mlt_frame_push_get_image( mlt_frame this, mlt_get_image get_image )
{
        int ret = this->stack_get_image_size >= 10;
        if ( ret == 0 )
                this->stack_get_image[ this->stack_get_image_size ++ ] = get_image;
        return ret;
}

/** Pop a get_image callback.
*/

mlt_get_image mlt_frame_pop_get_image( mlt_frame this )
{
        mlt_get_image result = NULL;
        if ( this->stack_get_image_size > 0 )
                result = this->stack_get_image[ -- this->stack_get_image_size ];
        return result;
}

/** Push a frame.
*/

int mlt_frame_push_frame( mlt_frame this, mlt_frame that )
{
        int ret = this->stack_frame_size >= 10;
        if ( ret == 0 )
                this->stack_frame[ this->stack_frame_size ++ ] = that;
        return ret;
}

/** Pop a frame.
*/

mlt_frame mlt_frame_pop_frame( mlt_frame this )
{
        mlt_frame result = NULL;
        if ( this->stack_frame_size > 0 )
                result = this->stack_frame[ -- this->stack_frame_size ];
        return result;
}

int mlt_frame_get_image( mlt_frame this, uint8_t **buffer, mlt_image_format *format, int *width, int *height, int writable )
{
        mlt_properties properties = mlt_frame_properties( this );
        mlt_get_image get_image = mlt_frame_pop_get_image( this );
        
        if ( get_image != NULL )
        {
                return get_image( this, buffer, format, width, height, writable );
        }
        else if ( mlt_properties_get_data( properties, "image", NULL ) != NULL )
        {
                *format = mlt_image_yuv422;
                *buffer = mlt_properties_get_data( properties, "image", NULL );
                *width = mlt_properties_get_int( properties, "width" );
                *height = mlt_properties_get_int( properties, "height" );
        }
        else
        {
                if ( test_card.vfmt != *format )
                {
                        uint8_t *p;
                        uint8_t *q;
                        
                        test_card.vfmt = *format;
                        test_card.width = *width == 0 ? 720 : *width;
                        test_card.height = *height == 0 ? 576 : *height;

                        switch( *format )
                        {
                                case mlt_image_none:
                                        break;
                                case mlt_image_rgb24:
                                        test_card.image = realloc( test_card.image, test_card.width * test_card.height * 3 );
                                        memset( test_card.image, 255, test_card.width * test_card.height * 3 );
                                        break;
                                case mlt_image_rgb24a:
                                        test_card.image = realloc( test_card.image, test_card.width * test_card.height * 4 );
                                        memset( test_card.image, 255, test_card.width * test_card.height * 4 );
                                        break;
                                case mlt_image_yuv422:
                                        test_card.image = realloc( test_card.image, test_card.width * test_card.height * 2 );
                                        p = test_card.image;
                                        q = test_card.image + test_card.width * test_card.height * 2;
                                        while ( p != q )
                                        {
                                                *p ++ = 255;
                                                *p ++ = 128;
                                        }
                                        break;
                                case mlt_image_yuv420p:
                                        test_card.image = realloc( test_card.image, test_card.width * test_card.height * 3 / 2 );
                                        memset( test_card.image, 255, test_card.width * test_card.height * 3 / 2 );
                                        break;
                        }
                }

                *width = test_card.width;
                *height = test_card.height;
                *buffer = test_card.image;
        }

        return 0;
}

uint8_t *mlt_frame_get_alpha_mask( mlt_frame this )
{
        if ( this->get_alpha_mask != NULL )
                return this->get_alpha_mask( this );
        return test_card.alpha;
}

int mlt_frame_get_audio( mlt_frame this, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
{
        if ( this->get_audio != NULL )
        {
                return this->get_audio( this, buffer, format, frequency, channels, samples );
        }
        else
        {
                if ( *samples <= 0 )
                        *samples = 1920;
                if ( *channels <= 0 )
                        *channels = 2;
                if ( *frequency <= 0 )
                        *frequency = 48000;
                if ( test_card.audio == NULL || test_card.afmt != *format )
                {
                        test_card.afmt = *format;
                        test_card.audio = realloc( test_card.audio, *samples * *channels * sizeof( int16_t ) );
                        memset( test_card.audio, 0, *samples * *channels * sizeof( int16_t ) );
                }
                
                *buffer = test_card.audio;
        }
        return 0;
}

void mlt_frame_close( mlt_frame this )
{
        mlt_frame frame = mlt_frame_pop_frame( this );
        
        while ( frame != NULL )
        {
                mlt_frame_close( frame);
                frame = mlt_frame_pop_frame( this );
        }
        
        mlt_properties_close( &this->parent );

        free( this );
}

/***** convenience functions *****/
#define RGB2YUV(r, g, b, y, u, v)\
  y = (306*r + 601*g + 117*b)  >> 10;\
  u = ((-172*r - 340*g + 512*b) >> 10)  + 128;\
  v = ((512*r - 429*g - 83*b) >> 10) + 128;\
  y = y < 0 ? 0 : y;\
  u = u < 0 ? 0 : u;\
  v = v < 0 ? 0 : v;\
  y = y > 255 ? 255 : y;\
  u = u > 255 ? 255 : u;\
  v = v > 255 ? 255 : v

int mlt_convert_rgb24a_to_yuv422( uint8_t *rgba, int width, int height, int stride, uint8_t *yuv, uint8_t *alpha )
{
        int ret = 0;
        register int y0, y1, u0, u1, v0, v1;
        register int r, g, b;
        register uint8_t *d = yuv;
        register int i, j;

        for ( i = 0; i < height; i++ )
        {
                register uint8_t *s = rgba + ( stride * i );
                for ( j = 0; j < ( width / 2 ); j++ )
                {
                        r = *s++;
                        g = *s++;
                        b = *s++;
                        *alpha++ = *s++;
                        RGB2YUV (r, g, b, y0, u0 , v0);
                        r = *s++;
                        g = *s++;
                        b = *s++;
                        *alpha++ = *s++;
                        RGB2YUV (r, g, b, y1, u1 , v1);
                        *d++ = y0;
                        *d++ = (u0+u1) >> 1;
                        *d++ = y1;
                        *d++ = (v0+v1) >> 1;
                }
                if ( width % 2 )
                {
                        r = *s++;
                        g = *s++;
                        b = *s++;
                        *alpha++ = *s++;
                        RGB2YUV (r, g, b, y0, u0 , v0);
                        *d++ = y0;
                        *d++ = u0;
                }
        }
        return ret;
}

int mlt_convert_rgb24_to_yuv422( uint8_t *rgb, int width, int height, int stride, uint8_t *yuv )
{
        int ret = 0;
        register int y0, y1, u0, u1, v0, v1;
        register int r, g, b;
        register uint8_t *d = yuv;
        register int i, j;

        for ( i = 0; i < height; i++ )
        {
                register uint8_t *s = rgb + ( stride * i );
                for ( j = 0; j < ( width / 2 ); j++ )
                {
                        r = *s++;
                        g = *s++;
                        b = *s++;
                        RGB2YUV (r, g, b, y0, u0 , v0);
                        r = *s++;
                        g = *s++;
                        b = *s++;
                        RGB2YUV (r, g, b, y1, u1 , v1);
                        *d++ = y0;
                        *d++ = (u0+u1) >> 1;
                        *d++ = y1;
                        *d++ = (v0+v1) >> 1;
                }
                if ( width % 2 )
                {
                        r = *s++;
                        g = *s++;
                        b = *s++;
                        RGB2YUV (r, g, b, y0, u0 , v0);
                        *d++ = y0;
                        *d++ = u0;
                }
        }
        return ret;
}

int mlt_convert_yuv420p_to_yuv422( uint8_t *yuv420p, int width, int height, int stride, uint8_t *yuv )
{
        int ret = 0;
        register int i, j;

        int half = width >> 1;

        uint8_t *Y = yuv420p;
        uint8_t *U = Y + width * height;
        uint8_t *V = U + width * height / 4;

        register uint8_t *d = yuv;

        for ( i = 0; i < height; i++ )
        {
                register uint8_t *u = U + ( i / 2 ) * ( half );
                register uint8_t *v = V + ( i / 2 ) * ( half );

                for ( j = 0; j < half; j++ )
                {
                        *d ++ = *Y ++;
                        *d ++ = *u ++;
                        *d ++ = *Y ++;
                        *d ++ = *v ++;
                }
        }
        return ret;
}

int mlt_frame_composite_yuv( mlt_frame this, mlt_frame that, int x, int y, float weight )
{
        int ret = 0;
        int width_src = 0, height_src = 0;
        int width_dest = 0, height_dest = 0;
        mlt_image_format format_src = mlt_image_yuv422, format_dest = mlt_image_yuv422;
        uint8_t *p_src, *p_dest;
        int i, j;
        int stride_src;
        int stride_dest;
        int x_src = 0, y_src = 0;

        // optimization point - no work to do
        if ( ( x < 0 && -x >= width_src ) || ( y < 0 && -y >= height_src ) )
                return ret;

        format_src = mlt_image_yuv422;
        format_dest = mlt_image_yuv422;

        //fprintf( stderr, "call get_image on frame a\n"), fflush( stderr );
        mlt_frame_get_image( this, &p_dest, &format_dest, &width_dest, &height_dest, 1 /* writable */ );
        //fprintf( stderr, "call get_image on frame b\n"), fflush( stderr );
        mlt_frame_get_image( that, &p_src, &format_src, &width_src, &height_src, 0 /* writable */ );

        //fprintf( stderr, "mlt_frame_composite_yuv %dx%d -> %dx%d\n", width_src, height_src, width_dest, height_dest );
        //fflush(stderr);
        //return ret;
        stride_src = width_src * 2;
        stride_dest = width_dest * 2;
        
        // crop overlay off the left edge of frame
        if ( x < 0 )
        {
                x_src = -x;
                width_src -= x_src;
                x = 0;
        }
        
        // crop overlay beyond right edge of frame
        else if ( x + width_src > width_dest )
                width_src = width_dest - x;

        // crop overlay off the top edge of the frame
        if ( y < 0 )
        {
                y_src = -y;
                height_src -= y_src;
        }
        // crop overlay below bottom edge of frame
        else if ( y + height_src > height_dest )
                height_src = height_dest - y;

        // offset pointer into overlay buffer based on cropping
        p_src += x_src * 2 + y_src * stride_src;

        // offset pointer into frame buffer based upon positive, even coordinates only!
//      if ( interlaced && y % 2 )
//              ++y;
        p_dest += ( x < 0 ? 0 : x ) * 2 + ( y < 0 ? 0 : y ) * stride_dest;

        // Get the alpha channel of the overlay
        uint8_t *p_alpha = mlt_frame_get_alpha_mask( that );

        // offset pointer into alpha channel based upon cropping
        if ( p_alpha )
                p_alpha += x_src + y_src * stride_src / 2;

        // now do the compositing only to cropped extents
        for ( i = 0; i < height_src; i++ )
        {
                uint8_t *p = p_src;
                uint8_t *q = p_dest;
                uint8_t *o = p_dest;
                uint8_t *z = p_alpha;

                for ( j = 0; j < width_src; j ++ )
                {
                                uint8_t y = *p ++;
                                uint8_t uv = *p ++;
                                uint8_t a = ( z == NULL ) ? 255 : *z ++;
                                float value = ( weight * ( float ) a / 255.0 );
                                *o ++ = (uint8_t)( y * value + *q++ * ( 1 - value ) );
                                *o ++ = (uint8_t)( uv * value + *q++ * ( 1 - value ) );
                }

                p_src += stride_src;
                p_dest += stride_dest;
                if ( p_alpha )
                        p_alpha += stride_src / 2;
        }

        return ret;
}

void *memfill( void *dst, void *src, int l, int elements )
{
        int i = 0;
        for ( i = 0; i < elements; i ++ )
                dst = memcpy( dst, src, l ) + l;
        return dst;
}

void mlt_resize_yuv422( uint8_t *output, int owidth, int oheight, uint8_t *input, int iwidth, int iheight )
{
        // Calculate strides
        int istride = iwidth * 2;
        int ostride = owidth * 2;

        iwidth = iwidth - ( iwidth % 4 );
        owidth = owidth - ( owidth % 4 );
        iheight = iheight - ( iheight % 2 );
        oheight = oheight - ( oheight % 2 );

        // Coordinates (0,0 is middle of output)
        int y;

        // Calculate ranges
        int out_x_range = owidth / 2;
        int out_y_range = oheight / 2;
        int in_x_range = iwidth / 2 < out_x_range ? iwidth / 2 : out_x_range;
        int in_y_range = iheight / 2 < out_y_range ? iheight / 2 : out_y_range;

        // Output pointers
        uint8_t *out_line = output;
        uint8_t *out_ptr = out_line;

        // Calculate a middle and possibly invalid pointer in the input
        uint8_t *in_middle = input + istride * ( iheight / 2 ) + ( iwidth / 2 ) * 2;
        int in_line = - in_y_range * istride - in_x_range * 2;

        uint8_t black[ 2 ] = { 16, 128 };

        // Loop for the entirety of our output height.
        for ( y = - out_y_range; y < out_y_range ; y ++ )
        {
        // Start at the beginning of the line
        out_ptr = out_line;

                if ( abs( y ) < iheight / 2 )
                {
                        // Fill the outer part with black
                        out_ptr = memfill( out_ptr, black, 2, out_x_range - in_x_range );

                // We're in the input range for this row.
                        memcpy( out_ptr, in_middle + in_line, 2 * iwidth );
                        out_ptr += 2 * iwidth;

                        // Fill the outer part with black
                        out_ptr = memfill( out_ptr, black, 2, out_x_range - in_x_range );

                // Move to next input line
                in_line += istride;
                }
                else
                {
                        // Fill whole line with black
                        out_ptr = memfill( out_ptr, black, 2, owidth );
                }

        // Move to next output line
        out_line += ostride;
        }
}

/** A resizing function for yuv422 frames - this does not rescale, but simply
        resizes. It assumes yuv422 images available on the frame so use with care.
*/

uint8_t *mlt_frame_resize_yuv422( mlt_frame this, int owidth, int oheight )
{
        // Get properties
        mlt_properties properties = mlt_frame_properties( this );

        // Get the input image, width and height
        uint8_t *input = mlt_properties_get_data( properties, "image", NULL );
        int iwidth = mlt_properties_get_int( properties, "width" );
        int iheight = mlt_properties_get_int( properties, "height" );

        // If width and height are correct, don't do anything
        if ( iwidth != owidth || iheight != oheight )
        {
                // Create the output image
                uint8_t *output = malloc( owidth * oheight * 2 );

                // Call the generic resize
                mlt_resize_yuv422( output, owidth, oheight, input, iwidth, iheight );

                // Now update the frame
                mlt_properties_set_data( properties, "image", output, owidth * oheight * 2, free, NULL );
                mlt_properties_set_int( properties, "width", owidth );
                mlt_properties_set_int( properties, "height", oheight );

                // Return the output
                return output;
        }

        // No change, return input
        return input;
}

/** A rescaling function for yuv422 frames - low quality, and provided for testing
        only. It assumes yuv422 images available on the frame so use with care.
*/

uint8_t *mlt_frame_rescale_yuv422( mlt_frame this, int owidth, int oheight )
{
        // Get properties
        mlt_properties properties = mlt_frame_properties( this );

        // Get the input image, width and height
        uint8_t *input = mlt_properties_get_data( properties, "image", NULL );
        int iwidth = mlt_properties_get_int( properties, "width" );
        int iheight = mlt_properties_get_int( properties, "height" );

        // If width and height are correct, don't do anything
        if ( iwidth != owidth || iheight != oheight )
        {
                // Create the output image
                uint8_t *output = malloc( owidth * oheight * 2 );

                // Calculate strides
                int istride = iwidth * 2;
                int ostride = owidth * 2;

                iwidth = iwidth - ( iwidth % 4 );

        // Coordinates (0,0 is middle of output)
        int y, x;

                // Derived coordinates
                int dy, dx;

        // Calculate ranges
        int out_x_range = owidth / 2;
        int out_y_range = oheight / 2;
        int in_x_range = iwidth / 2;
        int in_y_range = iheight / 2;

        // Output pointers
        uint8_t *out_line = output;
        uint8_t *out_ptr;

        // Calculate a middle pointer
        uint8_t *in_middle = input + istride * in_y_range + in_x_range * 2;
        uint8_t *in_line;
                uint8_t *in_ptr;

                // Generate the affine transform scaling values
                float scale_width = ( float )iwidth / ( float )owidth;
                float scale_height = ( float )iheight / ( float )oheight;

        // Loop for the entirety of our output height.
        for ( y = - out_y_range; y < out_y_range ; y ++ )
        {
                        // Calculate the derived y value
                        dy = scale_height * y;

                // Start at the beginning of the line
                out_ptr = out_line;
        
                // Pointer to the middle of the input line
                in_line = in_middle + dy * istride;
        
                // Loop for the entirety of our output row.
                for ( x = - out_x_range; x < out_x_range; x += 1 )
                {
                                // Calculated the derived x
                                dx = scale_width * x;

                // Check if x and y are in the valid input range.
                if ( abs( dx ) < in_x_range && abs( dy ) < in_y_range  )
                {
                        // We're in the input range for this row.
                                        in_ptr = in_line + ( dx >> 1 ) * 4 + 2 * ( x & 1 );
                        *out_ptr ++ = *in_ptr ++;
                        *out_ptr ++ = *in_ptr ++;
                }
                else
                {
                        // We're not in the input range for this row.
                        *out_ptr ++ = 16;
                        *out_ptr ++ = 128;
                }
                }

                // Move to next output line
                out_line += ostride;
        }

                // Now update the frame
                mlt_properties_set_data( properties, "image", output, owidth * oheight * 2, free, NULL );
                mlt_properties_set_int( properties, "width", owidth );
                mlt_properties_set_int( properties, "height", oheight );

                // Return the output
                return output;
        }

        // No change, return input
        return input;
}

int mlt_frame_mix_audio( mlt_frame this, mlt_frame that, float weight, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
{
        int ret = 0;
        int16_t *p_src, *p_dest;
        int16_t *src, *dest;
        //static int16_t *extra_src = NULL, *extra_dest = NULL;
        static int extra_src_samples = 0, extra_dest_samples = 0;
        int frequency_src = 0, frequency_dest = 0;
        int channels_src = 0, channels_dest = 0;
        int samples_src = 0, samples_dest = 0;
        int i, j;

        mlt_frame_get_audio( this, &p_dest, format, &frequency_dest, &channels_dest, &samples_dest );
        //fprintf( stderr, "frame dest samples %d channels %d position %f\n", samples_dest, channels_dest, mlt_properties_get_position( mlt_frame_properties( this ), "position" ) );
        mlt_frame_get_audio( that, &p_src, format, &frequency_src, &channels_src, &samples_src );
        //fprintf( stderr, "frame src  samples %d channels %d\n", samples_src, channels_src );
        if ( channels_src > 6 )
                channels_src = 0;
        if ( channels_dest > 6 )
                channels_dest = 0;
        if ( samples_src > 4000 )
                samples_src = 0;
        if ( samples_dest > 4000 )
                samples_dest = 0;

#if 0
        // Append new samples to leftovers
        if ( extra_dest_samples > 0 )
        {
                fprintf( stderr, "prepending %d samples to dest\n", extra_dest_samples );
                dest = realloc( extra_dest, ( samples_dest + extra_dest_samples ) * 2 * channels_dest );
                memcpy( &extra_dest[ extra_dest_samples * channels_dest ], p_dest, samples_dest * 2 * channels_dest );
        }
        else
                dest = p_dest;
        if ( extra_src_samples > 0 )
        {
                fprintf( stderr, "prepending %d samples to src\n", extra_src_samples );
                src = realloc( extra_src, ( samples_src + extra_src_samples ) * 2 * channels_src );
                memcpy( &extra_src[ extra_src_samples * channels_src ], p_src, samples_src * 2 * channels_src );
        }
        else
                src = p_src;
#else
        src = p_src;
        dest = p_dest;
#endif

        // determine number of samples to process       
        if ( samples_src + extra_src_samples < samples_dest + extra_dest_samples )
                *samples = samples_src + extra_src_samples;
        else if ( samples_dest + extra_dest_samples < samples_src + extra_src_samples )
                *samples = samples_dest + extra_dest_samples;
        
        *channels = channels_src < channels_dest ? channels_src : channels_dest;
        *buffer = p_dest;

        // Mixdown
        for ( i = 0; i < *samples; i++ )
        {
                for ( j = 0; j < *channels; j++ )
                {
                        double d = (double) dest[ i * channels_dest + j ];
                        double s = (double) src[ i * channels_src + j ];
                        dest[ i * channels_dest + j ] = s * weight + d * ( 1.0 - weight );
                }
        }

        // We have to copy --sigh
        if ( dest != p_dest )
                memcpy( p_dest, dest, *samples * 2 * *channels );

#if 0
        // Store the leftovers
        if ( samples_src + extra_src_samples < samples_dest + extra_dest_samples )
        {
                extra_dest_samples = ( samples_dest + extra_dest_samples ) - ( samples_src + extra_src_samples );
                size_t size = extra_dest_samples * 2 * channels_dest;
                fprintf( stderr, "storing %d samples from dest\n", extra_dest_samples );
                if ( extra_dest )
                        free( extra_dest );
                extra_dest = malloc( size );
                if ( extra_dest )
                        memcpy( extra_dest, &p_dest[ ( samples_dest - extra_dest_samples - 1 ) * channels_dest ], size );
                else
                        extra_dest_samples = 0;
        }
        else if ( samples_dest + extra_dest_samples < samples_src + extra_src_samples )
        {
                extra_src_samples = ( samples_src + extra_src_samples ) - ( samples_dest + extra_dest_samples );
                size_t size = extra_src_samples * 2 * channels_src;
                fprintf( stderr, "storing %d samples from src\n", extra_dest_samples );
                if ( extra_src )
                        free( extra_src );
                extra_src = malloc( size );
                if ( extra_src )
                        memcpy( extra_src, &p_src[ ( samples_src - extra_src_samples - 1 ) * channels_src ], size );
                else
                        extra_src_samples = 0;
        }
#endif
        
        return ret;
}

int mlt_sample_calculator( float fps, int frequency, int64_t position )
{
        int samples = 0;

        if ( fps > 29 && fps <= 30 )
        {
                samples = frequency / 30;

                switch ( frequency )
                {
                        case 48000:
                                if ( position % 5 != 0 )
                                        samples += 2;
                                break;
                        case 44100:
                                if ( position % 300 == 0 )
                                        samples = 1471;
                                else if ( position % 30 == 0 )
                                        samples = 1470;
                                else if ( position % 2 == 0 )
                                        samples = 1472;
                                else
                                        samples = 1471;
                                break;
                        case 32000:
                                if ( position % 30 == 0 )
                                        samples = 1068;
                                else if ( position % 29 == 0 )
                                        samples = 1067;
                                else if ( position % 4 == 2 )
                                        samples = 1067;
                                else
                                        samples = 1068;
                                break;
                        default:
                                samples = 0;
                }
        }
        else if ( fps != 0 )
        {
                samples = frequency / fps;
        }

        return samples;
}