[melted] / src / modules / core / transition_composite.c

/*
 * transition_composite.c -- compose one image over another using alpha channel
 * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
 * Author: Dan Dennedy <dan@dennedy.org>
 *
 * 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 "transition_composite.h"
#include <framework/mlt.h>

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>

/** Geometry struct.
*/

struct geometry_s
{
        float position;
        float mix;
        int nw; // normalised width
        int nh; // normalised height
        int sw; // scaled width, not including consumer scale based upon w/nw
        int sh; // scaled height, not including consumer scale based upon h/nh
        float x;
        float y;
        float w;
        float h;
        int halign; // horizontal alignment: 0=left, 1=center, 2=right
        int valign; // vertical alignment: 0=top, 1=middle, 2=bottom
        int distort;
        struct geometry_s *next;
};

/** Parse a value from a geometry string.
*/

static float parse_value( char **ptr, int normalisation, char delim, float defaults )
{
        float value = defaults;

        if ( *ptr != NULL && **ptr != '\0' )
        {
                char *end = NULL;
                value = strtod( *ptr, &end );
                if ( end != NULL )
                {
                        if ( *end == '%' )
                                value = ( value / 100.0 ) * normalisation;
                        while ( *end == delim || *end == '%' )
                                end ++;
                }
                *ptr = end;
        }

        return value;
}

/** Parse a geometry property string with the syntax X,Y:WxH:MIX. Any value can be 
        expressed as a percentage by appending a % after the value, otherwise values are
        assumed to be relative to the normalised dimensions of the consumer.
*/

static void geometry_parse( struct geometry_s *geometry, struct geometry_s *defaults, char *property, int nw, int nh )
{
        // Assign normalised width and height
        geometry->nw = nw;
        geometry->nh = nh;

        // Assign from defaults if available
        if ( defaults != NULL )
        {
                geometry->x = defaults->x;
                geometry->y = defaults->y;
                geometry->w = geometry->sw = defaults->w;
                geometry->h = geometry->sh = defaults->h;
                geometry->distort = defaults->distort;
                geometry->mix = defaults->mix;
                defaults->next = geometry;
        }
        else
        {
                geometry->mix = 100;
        }

        // Parse the geomtry string
        if ( property != NULL && strcmp( property, "" ) )
        {
                char *ptr = property;
                geometry->x = parse_value( &ptr, nw, ',', geometry->x );
                geometry->y = parse_value( &ptr, nh, ':', geometry->y );
                geometry->w = geometry->sw = parse_value( &ptr, nw, 'x', geometry->w );
                geometry->h = geometry->sh = parse_value( &ptr, nh, ':', geometry->h );
                if ( *ptr == '!' )
                {
                        geometry->distort = 1;
                        ptr ++;
                        if ( *ptr == ':' )
                                ptr ++;
                }
                geometry->mix = parse_value( &ptr, 100, ' ', geometry->mix );
        }
}

/** Calculate real geometry.
*/

static void geometry_calculate( struct geometry_s *output, struct geometry_s *in, float position )
{
        // Search in for position
        struct geometry_s *out = in->next;

        if ( position >= 1.0 )
        {
                int section = floor( position );
                position -= section;
                if ( section % 2 == 1 )
                        position = 1.0 - position;
        }

        while ( out->next != NULL )
        {
                if ( position >= in->position && position < out->position )
                        break;

                in = out;
                out = in->next;
        }

        position = ( position - in->position ) / ( out->position - in->position );

        // Calculate this frames geometry
        output->nw = in->nw;
        output->nh = in->nh;
        output->x = in->x + ( out->x - in->x ) * position;
        output->y = in->y + ( out->y - in->y ) * position;
        output->w = in->w + ( out->w - in->w ) * position;
        output->h = in->h + ( out->h - in->h ) * position;
        output->mix = in->mix + ( out->mix - in->mix ) * position;
        output->distort = in->distort;

        output->x = ( int )floor( output->x ) & 0xfffffffe;
        output->w = ( int )floor( output->w ) & 0xfffffffe;
        output->sw &= 0xfffffffe;
}

void transition_destroy_keys( void *arg )
{
        struct geometry_s *ptr = arg;
        struct geometry_s *next = NULL;

        while ( ptr != NULL )
        {
                next = ptr->next;
                free( ptr );
                ptr = next;
        }
}

static struct geometry_s *transition_parse_keys( mlt_transition this,  int normalised_width, int normalised_height )
{
        // Loop variable for property interrogation
        int i = 0;

        // Get the properties of the transition
        mlt_properties properties = mlt_transition_properties( this );

        // Get the in and out position
        mlt_position in = mlt_transition_get_in( this );
        mlt_position out = mlt_transition_get_out( this );

        // Create the start
        struct geometry_s *start = calloc( 1, sizeof( struct geometry_s ) );

        // Create the end (we always need two entries)
        struct geometry_s *end = calloc( 1, sizeof( struct geometry_s ) );

        // Pointer
        struct geometry_s *ptr = start;

        // Parse the start property
        geometry_parse( start, NULL, mlt_properties_get( properties, "start" ), normalised_width, normalised_height );

        // Parse the keys in between
        for ( i = 0; i < mlt_properties_count( properties ); i ++ )
        {
                // Get the name of the property
                char *name = mlt_properties_get_name( properties, i );

                // Check that it's valid
                if ( !strncmp( name, "key[", 4 ) )
                {
                        // Get the value of the property
                        char *value = mlt_properties_get_value( properties, i );

                        // Determine the frame number
                        int frame = atoi( name + 4 );

                        // Determine the position
                        float position = 0;
                        
                        if ( frame >= 0 && frame < ( out - in ) )
                                position = ( float )frame / ( float )( out - in + 1 );
                        else if ( frame < 0 && - frame < ( out - in ) )
                                position = ( float )( out - in + frame ) / ( float )( out - in + 1 );

                        // For now, we'll exclude all keys received out of order
                        if ( position > ptr->position )
                        {
                                // Create a new geometry
                                struct geometry_s *temp = calloc( 1, sizeof( struct geometry_s ) );

                                // Parse and add to the list
                                geometry_parse( temp, ptr, value, normalised_width, normalised_height );

                                // Assign the position
                                temp->position = position;

                                // Allow the next to be appended after this one
                                ptr = temp;
                        }
                        else
                        {
                                fprintf( stderr, "Key out of order - skipping %s\n", name );
                        }
                }
        }
        
        // Parse the end
        geometry_parse( end, ptr, mlt_properties_get( properties, "end" ), normalised_width, normalised_height );
        if ( out > 0 )
                end->position = ( float )( out - in ) / ( float )( out - in + 1 );
        else
                end->position = 1;

        // Assign to properties to ensure we get destroyed
        mlt_properties_set_data( properties, "geometries", start, 0, transition_destroy_keys, NULL );

        return start;
}

/** Parse the alignment properties into the geometry.
*/

static int alignment_parse( char* align )
{
        int ret = 0;
        
        if ( align == NULL );
        else if ( isdigit( align[ 0 ] ) )
                ret = atoi( align );
        else if ( align[ 0 ] == 'c' || align[ 0 ] == 'm' )
                ret = 1;
        else if ( align[ 0 ] == 'r' || align[ 0 ] == 'b' )
                ret = 2;

        return ret;
}

/** Adjust position according to scaled size and alignment properties.
*/

static void alignment_calculate( struct geometry_s *geometry )
{
        geometry->x += ( geometry->w - geometry->sw ) * geometry->halign / 2;
        geometry->y += ( geometry->h - geometry->sh ) * geometry->valign / 2;
}

/** Calculate the position for this frame.
*/

static float position_calculate( mlt_transition this, mlt_position position )
{
        // Get the in and out position
        mlt_position in = mlt_transition_get_in( this );
        mlt_position out = mlt_transition_get_out( this );

        // Now do the calcs
        return ( float )( position - in ) / ( float )( out - in + 1 );
}

/** Calculate the field delta for this frame - position between two frames.
*/

static inline float delta_calculate( mlt_transition this, mlt_frame frame )
{
        // Get the in and out position
        mlt_position in = mlt_transition_get_in( this );
        mlt_position out = mlt_transition_get_out( this );

        // Get the position of the frame
        mlt_position position = mlt_frame_get_position( frame );

        // Now do the calcs
        float x = ( float )( position - in ) / ( float )( out - in + 1 );
        float y = ( float )( position + 1 - in ) / ( float )( out - in + 1 );

        return ( y - x ) / 2.0;
}

static int get_value( mlt_properties properties, char *preferred, char *fallback )
{
        int value = mlt_properties_get_int( properties, preferred );
        if ( value == 0 )
                value = mlt_properties_get_int( properties, fallback );
        return value;
}

/** A linear threshold determination function.
*/

static inline int32_t linearstep( int32_t edge1, int32_t edge2, int32_t a )
{
        if ( a < edge1 )
                return 0;

        if ( a >= edge2 )
                return 0x10000;

        return ( ( a - edge1 ) << 16 ) / ( edge2 - edge1 );
}

/** A smoother, non-linear threshold determination function.
*/

static inline int32_t smoothstep( int32_t edge1, int32_t edge2, uint32_t a )
{
        if ( a < edge1 )
                return 0;

        if ( a >= edge2 )
                return 0x10000;

        a = ( ( a - edge1 ) << 16 ) / ( edge2 - edge1 );

        return ( ( ( a * a ) >> 16 )  * ( ( 3 << 16 ) - ( 2 * a ) ) ) >> 16;
}

/** Load the luma map from PGM stream.
*/

static void luma_read_pgm( FILE *f, uint16_t **map, int *width, int *height )
{
        uint8_t *data = NULL;
        while (1)
        {
                char line[128];
                char comment[128];
                int i = 2;
                int maxval;
                int bpp;
                uint16_t *p;

                line[127] = '\0';

                // get the magic code
                if ( fgets( line, 127, f ) == NULL )
                        break;

                // skip comments
                while ( sscanf( line, " #%s", comment ) > 0 )
                        if ( fgets( line, 127, f ) == NULL )
                                break;

                if ( line[0] != 'P' || line[1] != '5' )
                        break;

                // skip white space and see if a new line must be fetched
                for ( i = 2; i < 127 && line[i] != '\0' && isspace( line[i] ); i++ );
                if ( ( line[i] == '\0' || line[i] == '#' ) && fgets( line, 127, f ) == NULL )
                        break;

                // skip comments
                while ( sscanf( line, " #%s", comment ) > 0 )
                        if ( fgets( line, 127, f ) == NULL )
                                break;

                // get the dimensions
                if ( line[0] == 'P' )
                        i = sscanf( line, "P5 %d %d %d", width, height, &maxval );
                else
                        i = sscanf( line, "%d %d %d", width, height, &maxval );

                // get the height value, if not yet
                if ( i < 2 )
                {
                        if ( fgets( line, 127, f ) == NULL )
                                break;

                        // skip comments
                        while ( sscanf( line, " #%s", comment ) > 0 )
                                if ( fgets( line, 127, f ) == NULL )
                                        break;

                        i = sscanf( line, "%d", height );
                        if ( i == 0 )
                                break;
                        else
                                i = 2;
                }

                // get the maximum gray value, if not yet
                if ( i < 3 )
                {
                        if ( fgets( line, 127, f ) == NULL )
                                break;

                        // skip comments
                        while ( sscanf( line, " #%s", comment ) > 0 )
                                if ( fgets( line, 127, f ) == NULL )
                                        break;

                        i = sscanf( line, "%d", &maxval );
                        if ( i == 0 )
                                break;
                }

                // determine if this is one or two bytes per pixel
                bpp = maxval > 255 ? 2 : 1;

                // allocate temporary storage for the raw data
                data = mlt_pool_alloc( *width * *height * bpp );
                if ( data == NULL )
                        break;

                // read the raw data
                if ( fread( data, *width * *height * bpp, 1, f ) != 1 )
                        break;

                // allocate the luma bitmap
                *map = p = (uint16_t*)mlt_pool_alloc( *width * *height * sizeof( uint16_t ) );
                if ( *map == NULL )
                        break;

                // proces the raw data into the luma bitmap
                for ( i = 0; i < *width * *height * bpp; i += bpp )
                {
                        if ( bpp == 1 )
                                *p++ = data[ i ] << 8;
                        else
                                *p++ = ( data[ i ] << 8 ) + data[ i+1 ];
                }

                break;
        }

        if ( data != NULL )
                mlt_pool_release( data );
}

/** Generate a luma map from any YUV image.
*/

static void luma_read_yuv422( uint8_t *image, uint16_t **map, int width, int height )
{
        int i;
        
        // allocate the luma bitmap
        uint16_t *p = *map = ( uint16_t* )mlt_pool_alloc( width * height * sizeof( uint16_t ) );
        if ( *map == NULL )
                return;

        // proces the image data into the luma bitmap
        for ( i = 0; i < width * height * 2; i += 2 )
                *p++ = ( image[ i ] - 16 ) * 299; // 299 = 65535 / 219
}

/** Composite function.
*/

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, uint16_t *p_luma, int32_t softness )
{
        int ret = 0;
        int i, j;
        int x_src = 0, y_src = 0;
        int32_t weight = ( 1 << 16 ) * ( geometry.mix / 100 );
        int stride_src = width_src * bpp;
        int stride_dest = width_dest * bpp;

        // Adjust to consumer scale
        int x = geometry.x * width_dest / geometry.nw;
        int y = geometry.y * height_dest / geometry.nh;

        x &= 0xfffffffe;
        width_src &= 0xfffffffe;

        // optimization points - no work to do
        if ( width_src <= 0 || height_src <= 0 )
                return ret;

        if ( ( x < 0 && -x >= width_src ) || ( y < 0 && -y >= height_src ) )
                return ret;

        // 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 * bpp + y_src * stride_src;

        // offset pointer into frame buffer based upon positive coordinates only!
        p_dest += ( x < 0 ? 0 : x ) * bpp + ( y < 0 ? 0 : y ) * stride_dest;

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

        // offset pointer into luma channel based upon cropping
        if ( p_luma )
                p_luma += x_src + y_src * stride_src / bpp;
        
        // Assuming lower field first
        // Special care is taken to make sure the b_frame is aligned to the correct field.
        // field 0 = lower field and y should be odd (y is 0-based).
        // field 1 = upper field and y should be even.
        if ( ( field > -1 ) && ( y % 2 == field ) )
        {
                //fprintf( stderr, "field %d y %d\n", field, y );
                if ( ( field == 1 && y < height_dest - 1 ) || ( field == 0 && y == 0 ) )
                        p_dest += stride_dest;
                else
                        p_dest -= stride_dest;
        }

        // On the second field, use the other lines from b_frame
        if ( field == 1 )
        {
                p_src += stride_src;
                if ( p_alpha )
                        p_alpha += stride_src / bpp;
                height_src--;
        }

        uint8_t *p = p_src;
        uint8_t *q = p_dest;
        uint8_t *o = p_dest;
        uint16_t *l = p_luma;
        uint8_t *z = p_alpha;

        uint8_t a;
        int32_t current_weight;
        int32_t value;
        int step = ( field > -1 ) ? 2 : 1;

        stride_src = stride_src * step;
        int alpha_stride = stride_src / bpp;
        stride_dest = stride_dest * step;

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

                for ( j = 0; j < width_src; j ++ )
                {
                        a = ( z == NULL ) ? 255 : *z ++;
                        current_weight = ( l == NULL ) ? weight : linearstep( l[ j ], l[ j ] + softness, weight );
                        value = ( current_weight * ( a + 1 ) ) >> 8;
                        *o ++ = ( *p++ * value + *q++ * ( ( 1 << 16 ) - value ) ) >> 16;
                        *o ++ = ( *p++ * value + *q++ * ( ( 1 << 16 ) - value ) ) >> 16;
                }

                p_src += stride_src;
                p_dest += stride_dest;
                if ( p_alpha )
                        p_alpha += alpha_stride;
                if ( p_luma )
                        p_luma += alpha_stride;
        }

        return ret;
}

static uint16_t* get_luma( mlt_properties properties, int width, int height )
{
        // The cached luma map information
        int luma_width = mlt_properties_get_int( properties, "_luma.width" );
        int luma_height = mlt_properties_get_int( properties, "_luma.height" );
        uint16_t *luma_bitmap = mlt_properties_get_data( properties, "_luma.bitmap", NULL );
        
        // If the filename property changed, reload the map
        char *resource = mlt_properties_get( properties, "luma" );

        if ( luma_bitmap == NULL && resource != NULL )
        {
                char *extension = extension = strrchr( resource, '.' );

                // See if it is a PGM
                if ( extension != NULL && strcmp( extension, ".pgm" ) == 0 )
                {
                        // Open PGM
                        FILE *f = fopen( resource, "r" );
                        if ( f != NULL )
                        {
                                // Load from PGM
                                luma_read_pgm( f, &luma_bitmap, &luma_width, &luma_height );
                                fclose( f );

                                // Set the transition properties
                                mlt_properties_set_int( properties, "_luma.width", luma_width );
                                mlt_properties_set_int( properties, "_luma.height", luma_height );
                                mlt_properties_set_data( properties, "_luma.bitmap", luma_bitmap, luma_width * luma_height * 2, mlt_pool_release, NULL );
                        }
                }
                else
                {
                        // Get the factory producer service
                        char *factory = mlt_properties_get( properties, "factory" );

                        // Create the producer
                        mlt_producer producer = mlt_factory_producer( factory, resource );

                        // If we have one
                        if ( producer != NULL )
                        {
                                // Get the producer properties
                                mlt_properties producer_properties = mlt_producer_properties( producer );

                                // Ensure that we loop
                                mlt_properties_set( producer_properties, "eof", "loop" );

                                // Now pass all producer. properties on the transition down
                                mlt_properties_pass( producer_properties, properties, "luma." );

                                // We will get the alpha frame from the producer
                                mlt_frame luma_frame = NULL;

                                // Get the luma frame
                                if ( mlt_service_get_frame( mlt_producer_service( producer ), &luma_frame, 0 ) == 0 )
                                {
                                        uint8_t *luma_image;
                                        mlt_image_format luma_format = mlt_image_yuv422;

                                        // Request a luma image the size of transition image request
                                        luma_width = width;
                                        luma_height = height;

                                        // Get image from the luma producer
                                        mlt_properties_set( mlt_frame_properties( luma_frame ), "distort", "true" );
                                        mlt_frame_get_image( luma_frame, &luma_image, &luma_format, &luma_width, &luma_height, 0 );

                                        // Generate the luma map
                                        if ( luma_image != NULL && luma_format == mlt_image_yuv422 )
                                        {
                                                luma_read_yuv422( luma_image, &luma_bitmap, luma_width, luma_height );
                                        
                                                // Set the transition properties
                                                mlt_properties_set_int( properties, "_luma.width", luma_width );
                                                mlt_properties_set_int( properties, "_luma.height", luma_height );
                                                mlt_properties_set_data( properties, "_luma.bitmap", luma_bitmap, luma_width * luma_height * 2, mlt_pool_release, NULL );
                                        }

                                        // Cleanup the luma frame
                                        mlt_frame_close( luma_frame );
                                }

                                // Cleanup the luma producer
                                mlt_producer_close( producer );
                        }
                }
        }
        return luma_bitmap;
}

/** Get the properly sized image from b_frame.
*/

static int get_b_frame_image( mlt_transition this, mlt_frame b_frame, uint8_t **image, int *width, int *height, struct geometry_s *geometry )
{
        int ret = 0;
        mlt_image_format format = mlt_image_yuv422;

        // Get the properties objects
        mlt_properties b_props = mlt_frame_properties( b_frame );
        mlt_properties properties = mlt_transition_properties( this );

        if ( mlt_properties_get( properties, "distort" ) == NULL && geometry->distort == 0 )
        {
                // Adjust b_frame pixel aspect
                int normalised_width = geometry->w;
                int normalised_height = geometry->h;
                int real_width = get_value( b_props, "real_width", "width" );
                int real_height = get_value( b_props, "real_height", "height" );
                double input_ar = mlt_frame_get_aspect_ratio( b_frame );
                double output_ar = mlt_properties_get_double( b_props, "consumer_aspect_ratio" );
                int scaled_width = input_ar / output_ar * real_width;
                int scaled_height = real_height;
                        
                // Now ensure that our images fit in the normalised frame
                if ( scaled_width > normalised_width )
                {
                        scaled_height = scaled_height * normalised_width / scaled_width;
                        scaled_width = normalised_width;
                }
                if ( scaled_height > normalised_height )
                {
                        scaled_width = scaled_width * normalised_height / scaled_height;
                        scaled_height = normalised_height;
                }

                // Now apply the fill
                // TODO: Should combine fill/distort in one property
                if ( mlt_properties_get( properties, "fill" ) != NULL )
                {
                        scaled_width = ( geometry->w / scaled_width ) * scaled_width;
                        scaled_height = ( geometry->h / scaled_height ) * scaled_height;
                }

                // Save the new scaled dimensions
                geometry->sw = scaled_width;
                geometry->sh = scaled_height;
        }
        else
        {
                geometry->sw = geometry->w;
                geometry->sh = geometry->h;
        }

        // We want to ensure that we bypass resize now...
        mlt_properties_set( b_props, "distort", "true" );

        // Take into consideration alignment for optimisation
        alignment_calculate( geometry );

        // Adjust to consumer scale
        int x = geometry->x * *width / geometry->nw;
        int y = geometry->y * *height / geometry->nh;
        *width = geometry->sw * *width / geometry->nw;
        *height = geometry->sh * *height / geometry->nh;

        x -= x % 2;

        // optimization points - no work to do
        if ( *width <= 0 || *height <= 0 )
                return 1;

        if ( ( x < 0 && -x >= *width ) || ( y < 0 && -y >= *height ) )
                return 1;

        ret = mlt_frame_get_image( b_frame, image, &format, width, height, 1 );

        return ret;
}


struct geometry_s *composite_calculate( struct geometry_s *result, mlt_transition this, mlt_frame a_frame, float position )
{
        // Get the properties from the transition
        mlt_properties properties = mlt_transition_properties( this );

        // Get the properties from the frame
        mlt_properties a_props = mlt_frame_properties( a_frame );
        
        // Structures for geometry
        struct geometry_s *start = mlt_properties_get_data( properties, "geometries", NULL );

        // Now parse the geometries
        if ( start == NULL )
        {
                // Obtain the normalised width and height from the a_frame
                int normalised_width = mlt_properties_get_int( a_props, "normalised_width" );
                int normalised_height = mlt_properties_get_int( a_props, "normalised_height" );

                // Parse the transitions properties
                start = transition_parse_keys( this, normalised_width, normalised_height );
        }

        // Do the calculation
        geometry_calculate( result, start, position );

        // Now parse the alignment
        result->halign = alignment_parse( mlt_properties_get( properties, "halign" ) );
        result->valign = alignment_parse( mlt_properties_get( properties, "valign" ) );

        return start;
}

mlt_frame composite_copy_region( mlt_transition this, mlt_frame a_frame, mlt_position frame_position )
{
        // Create a frame to return
        mlt_frame b_frame = mlt_frame_init( );

        // Get the properties of the a frame
        mlt_properties a_props = mlt_frame_properties( a_frame );

        // Get the properties of the b frame
        mlt_properties b_props = mlt_frame_properties( b_frame );

        // Get the position
        float position = position_calculate( this, frame_position );

        // Destination image
        uint8_t *dest = NULL;

        // Get the image and dimensions
        uint8_t *image = mlt_properties_get_data( a_props, "image", NULL );
        int width = mlt_properties_get_int( a_props, "width" );
        int height = mlt_properties_get_int( a_props, "height" );

        // Pointers for copy operation
        uint8_t *p;
        uint8_t *q;
        uint8_t *r;

        // Corrdinates
        int w = 0;
        int h = 0;
        int x = 0;
        int y = 0;

        // Will need to know region to copy
        struct geometry_s result;

        // Calculate the region now
        composite_calculate( &result, this, a_frame, position );

        // Need to scale down to actual dimensions
        x = result.x * width / result.nw ;
        y = result.y * height / result.nh;
        w = result.w * width / result.nw;
        h = result.h * height / result.nh;

        x &= 0xfffffffe;
        w &= 0xfffffffe;

        // Now we need to create a new destination image
        dest = mlt_pool_alloc( w * h * 2 );

        // Copy the region of the image
        p = image + y * width * 2 + x * 2;
        q = dest;
        r = dest + w * h * 2; 

        while ( q < r )
        {
                memcpy( q, p, w * 2 );
                q += w * 2;
                p += width * 2;
        }

        // Assign to the new frame
        mlt_properties_set_data( b_props, "image", dest, w * h * 2, mlt_pool_release, NULL );
        mlt_properties_set_int( b_props, "width", w );
        mlt_properties_set_int( b_props, "height", h );

        // Assign this position to the b frame
        mlt_frame_set_position( b_frame, frame_position );

        // Return the frame
        return b_frame;
}

/** Get the image.
*/

static int transition_get_image( mlt_frame a_frame, uint8_t **image, mlt_image_format *format, int *width, int *height, int writable )
{
        // Get the b frame from the stack
        mlt_frame b_frame = mlt_frame_pop_frame( a_frame );

        // Get the transition from the a frame
        mlt_transition this = mlt_frame_pop_service( a_frame );

        // This compositer is yuv422 only
        *format = mlt_image_yuv422;

        // Get the image from the a frame
        mlt_frame_get_image( a_frame, image, format, width, height, 1 );

        if ( b_frame != NULL )
        {
                // Get the properties of the a frame
                mlt_properties a_props = mlt_frame_properties( a_frame );

                // Get the properties of the b frame
                mlt_properties b_props = mlt_frame_properties( b_frame );

                // Get the properties from the transition
                mlt_properties properties = mlt_transition_properties( this );

                // Structures for geometry
                struct geometry_s result;

                // Calculate the position
                float position = mlt_properties_get_double( b_props, "relative_position" );
                float delta = delta_calculate( this, a_frame );

                // Do the calculation
                struct geometry_s *start = composite_calculate( &result, this, a_frame, position );
                
                // Optimisation - no compositing required
                if ( result.mix == 0 )
                        return 0;

                // Since we are the consumer of the b_frame, we must pass along these
                // consumer properties from the a_frame
                mlt_properties_set_double( b_props, "consumer_aspect_ratio", mlt_properties_get_double( a_props, "consumer_aspect_ratio" ) );

                // Get the image from the b frame
                uint8_t *image_b = NULL;
                int width_b = *width;
                int height_b = *height;
                
                if ( get_b_frame_image( this, b_frame, &image_b, &width_b, &height_b, &result ) == 0 )
                {
                        uint8_t *dest = *image;
                        uint8_t *src = image_b;
                        int bpp = 2;
                        uint8_t *alpha = mlt_frame_get_alpha_mask( b_frame );
                        int progressive = mlt_properties_get_int( a_props, "progressive" ) ||
                                        mlt_properties_get_int( a_props, "consumer_progressive" ) ||
                                        mlt_properties_get_int( properties, "progressive" );
                        int field;
                        
                        int32_t luma_softness = mlt_properties_get_double( properties, "softness" ) * ( 1 << 16 );
                        uint16_t *luma_bitmap = get_luma( properties, width_b, height_b );

                        for ( field = 0; field < ( progressive ? 1 : 2 ); field++ )
                        {
                                // Assume lower field (0) first
                                float field_position = position + field * delta;
                                
                                // Do the calculation if we need to
                                geometry_calculate( &result, start, field_position );

                                // Align
                                alignment_calculate( &result );

                                // Composite the b_frame on the a_frame
                                composite_yuv( dest, *width, *height, bpp, src, width_b, height_b, alpha, result, progressive ? -1 : field, luma_bitmap, luma_softness );
                        }
                }
        }

        return 0;
}

/** Composition transition processing.
*/

static mlt_frame composite_process( mlt_transition this, mlt_frame a_frame, mlt_frame b_frame )
{
        // Propogate the transition properties to the b frame
        mlt_properties_set_double( mlt_frame_properties( b_frame ), "relative_position", position_calculate( this, mlt_frame_get_position( a_frame ) ) );
        mlt_frame_push_service( a_frame, this );
        mlt_frame_push_get_image( a_frame, transition_get_image );
        mlt_frame_push_frame( a_frame, b_frame );
        return a_frame;
}

/** Constructor for the filter.
*/

mlt_transition transition_composite_init( char *arg )
{
        mlt_transition this = calloc( sizeof( struct mlt_transition_s ), 1 );
        if ( this != NULL && mlt_transition_init( this, NULL ) == 0 )
        {
                this->process = composite_process;
                mlt_properties_set( mlt_transition_properties( this ), "start", arg != NULL ? arg : "85%,5%:10%x10%" );
                
                // Default factory
                mlt_properties_set( mlt_transition_properties( this ), "factory", "fezzik" );
        }
        return this;
}