Data feed and show filters

[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 "mlt_producer.h"
#include "mlt_factory.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/** 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 )
        {
                // Get the normalisation
                char *normalisation = mlt_environment( "MLT_NORMALISATION" );

                // 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 );

                if ( normalisation == NULL || strcmp( normalisation, "NTSC" ) )
                {
                        mlt_properties_set_int( properties, "width", 720 );
                        mlt_properties_set_int( properties, "height", 576 );
                        mlt_properties_set_int( properties, "normalised_width", 720 );
                        mlt_properties_set_int( properties, "normalised_height", 576 );
                        mlt_properties_set_double( properties, "aspect_ratio", 72.0/79.0 );
                }
                else
                {
                        mlt_properties_set_int( properties, "width", 720 );
                        mlt_properties_set_int( properties, "height", 480 );
                        mlt_properties_set_int( properties, "normalised_width", 720 );
                        mlt_properties_set_int( properties, "normalised_height", 480 );
                        mlt_properties_set_double( properties, "aspect_ratio", 128.0/117.0 );
                }

                mlt_properties_set_data( properties, "audio", NULL, 0, NULL, NULL );
                mlt_properties_set_data( properties, "alpha", NULL, 0, NULL, NULL );

                // Construct stacks for frames and methods
                this->stack_image = mlt_deque_init( );
                this->stack_audio = mlt_deque_init( );
        }

        return this;
}

/** Fetch the frames properties.
*/

mlt_properties mlt_frame_properties( mlt_frame this )
{
        return this != NULL ? &this->parent : NULL;
}

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

int mlt_frame_is_test_card( mlt_frame this )
{
        return mlt_deque_count( this->stack_image ) == 0 || mlt_properties_get_int( mlt_frame_properties( this ), "test_image" );
}

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

int mlt_frame_is_test_audio( mlt_frame this )
{
        return this->get_audio == NULL || mlt_properties_get_int( mlt_frame_properties( this ), "test_audio" );
}

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

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

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

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

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

mlt_position mlt_frame_get_position( mlt_frame this )
{
        return mlt_properties_get_position( mlt_frame_properties( this ), "_position" );
}

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

int mlt_frame_set_position( mlt_frame this, mlt_position value )
{
        return mlt_properties_set_position( mlt_frame_properties( this ), "_position", value );
}

/** Stack a get_image callback.
*/

int mlt_frame_push_get_image( mlt_frame this, mlt_get_image get_image )
{
        return mlt_deque_push_back( this->stack_image, get_image );
}

/** Pop a get_image callback.
*/

mlt_get_image mlt_frame_pop_get_image( mlt_frame this )
{
        return mlt_deque_pop_back( this->stack_image );
}

/** Push a frame.
*/

int mlt_frame_push_frame( mlt_frame this, mlt_frame that )
{
        return mlt_deque_push_back( this->stack_image, that );
}

/** Pop a frame.
*/

mlt_frame mlt_frame_pop_frame( mlt_frame this )
{
        return mlt_deque_pop_back( this->stack_image );
}

/** Push a service.
*/

int mlt_frame_push_service( mlt_frame this, void *that )
{
        return mlt_deque_push_back( this->stack_image, that );
}

/** Pop a service.
*/

void *mlt_frame_pop_service( mlt_frame this )
{
        return mlt_deque_pop_back( this->stack_image );
}

/** Push an audio item on the stack.
*/

int mlt_frame_push_audio( mlt_frame this, void *that )
{
        return mlt_deque_push_back( this->stack_audio, that );
}

/** Pop an audio item from the stack
*/

void *mlt_frame_pop_audio( mlt_frame this )
{
        return mlt_deque_pop_back( this->stack_audio );
}

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 );
        mlt_producer producer = mlt_properties_get_data( properties, "test_card_producer", NULL );

        *width = *width >> 1 << 1;
        
        if ( get_image != NULL )
        {
                int error = 0;
                mlt_position position = mlt_frame_get_position( this );
                error = get_image( this, buffer, format, width, height, writable );
                mlt_frame_set_position( this, position );
                return error;
        }
        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 ( producer != NULL )
        {
                mlt_frame test_frame = NULL;
                mlt_service_get_frame( mlt_producer_service( producer ), &test_frame, 0 );
                if ( test_frame != NULL )
                {
                        mlt_properties test_properties = mlt_frame_properties( test_frame );
                        mlt_properties_set_double( test_properties, "consumer_aspect_ratio", mlt_properties_get_double( properties, "consumer_aspect_ratio" ) );
                        mlt_properties_set( test_properties, "rescale.interp", mlt_properties_get( properties, "rescale.interp" ) );
                        mlt_frame_get_image( test_frame, buffer, format, width, height, writable );
                        mlt_properties_set_data( properties, "test_card_frame", test_frame, 0, ( mlt_destructor )mlt_frame_close, NULL );
                        mlt_properties_set_data( properties, "image", *buffer, *width * *height * 2, NULL, NULL );
                        mlt_properties_set_int( properties, "width", *width );
                        mlt_properties_set_int( properties, "height", *height );
                        mlt_properties_set_double( properties, "aspect_ratio", mlt_frame_get_aspect_ratio( test_frame ) );
                        mlt_properties_set( properties, "rescale.interp", "none" );
                        mlt_properties_set( properties, "scale", "off" );
                }
                else
                {
                        mlt_properties_set_data( properties, "test_card_producer", NULL, 0, NULL, NULL );
                        mlt_frame_get_image( this, buffer, format, width, height, writable );
                }
        }
        else
        {
                register uint8_t *p;
                register uint8_t *q;
                int size = 0;

                *width = *width == 0 ? 720 : *width;
                *height = *height == 0 ? 576 : *height;
                size = *width * *height;

                mlt_properties_set_int( properties, "width", *width );
                mlt_properties_set_int( properties, "height", *height );
                mlt_properties_set_int( properties, "aspect_ratio", 1 );

                switch( *format )
                {
                        case mlt_image_none:
                                size = 0;
                                *buffer = NULL;
                                break;
                        case mlt_image_rgb24:
                                size *= 3;
                                size += *width * 3;
                                *buffer = mlt_pool_alloc( size );
                                if ( *buffer )
                                        memset( *buffer, 255, size );
                                break;
                        case mlt_image_rgb24a:
                                size *= 4;
                                size += *width * 4;
                                *buffer = mlt_pool_alloc( size );
                                if ( *buffer )
                                        memset( *buffer, 255, size );
                                break;
                        case mlt_image_yuv422:
                                size *= 2;
                                size += *width * 2;
                                *buffer = mlt_pool_alloc( size );
                                p = *buffer;
                                q = p + size;
                                while ( p != NULL && p != q )
                                {
                                        *p ++ = 235;
                                        *p ++ = 128;
                                }
                                break;
                        case mlt_image_yuv420p:
                                size = size * 3 / 2;
                                *buffer = mlt_pool_alloc( size );
                                if ( *buffer )
                                        memset( *buffer, 255, size );
                                break;
                }

                mlt_properties_set_data( properties, "image", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_int( properties, "test_image", 1 );
        }

        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 NULL;
}

int mlt_frame_get_audio( mlt_frame this, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
{
        mlt_properties properties = mlt_frame_properties( this );

        if ( this->get_audio != NULL )
        {
                this->get_audio( this, buffer, format, frequency, channels, samples );
        }
        else if ( mlt_properties_get_data( properties, "audio", NULL ) )
        {
                *buffer = mlt_properties_get_data( properties, "audio", NULL );
                *frequency = mlt_properties_get_int( properties, "audio_frequency" );
                *channels = mlt_properties_get_int( properties, "audio_channels" );
                *samples = mlt_properties_get_int( properties, "audio_samples" );
        }
        else
        {
                int size = 0;
                *samples = *samples <= 0 ? 1920 : *samples;
                *channels = *channels <= 0 ? 2 : *channels;
                *frequency = *frequency <= 0 ? 48000 : *frequency;
                size = *samples * *channels * sizeof( int16_t );
                *buffer = mlt_pool_alloc( size );
                if ( *buffer != NULL )
                        memset( *buffer, 0, size );
                mlt_properties_set_data( properties, "audio", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_int( properties, "test_audio", 1 );
        }

        mlt_properties_set_int( properties, "audio_frequency", *frequency );
        mlt_properties_set_int( properties, "audio_channels", *channels );
        mlt_properties_set_int( properties, "audio_samples", *samples );

        return 0;
}

unsigned char *mlt_frame_get_waveform( mlt_frame this, int w, int h )
{
        int16_t *pcm = NULL;
        mlt_properties properties = mlt_frame_properties( this );
        mlt_audio_format format = mlt_audio_pcm;
        int frequency = 32000; // lower frequency available?
        int channels = 2;
        double fps = mlt_properties_get_double( properties, "fps" );
        int samples = mlt_sample_calculator( fps, frequency, mlt_frame_get_position( this ) );
        
        // Get the pcm data
        mlt_frame_get_audio( this, &pcm, &format, &frequency, &channels, &samples );
        
        // Make an 8-bit buffer large enough to hold rendering
        int size = w * h;
        unsigned char *bitmap = ( unsigned char* )mlt_pool_alloc( size );
        if ( bitmap != NULL )
                memset( bitmap, 0, size );
        mlt_properties_set_data( properties, "waveform", bitmap, size, ( mlt_destructor )mlt_pool_release, NULL );
        
        // Render vertical lines
        int16_t *ubound = pcm + samples * channels;
        int skip = samples / w - 1;
        int i, j, k;
        
        // Iterate sample stream and along x coordinate
        for ( i = 0; i < w && pcm < ubound; i++ )
        {
                // pcm data has channels interleaved
                for ( j = 0; j < channels; j++ )
                {
                        // Determine sample's magnitude from 2s complement;
                        int pcm_magnitude = *pcm < 0 ? ~(*pcm) + 1 : *pcm;
                        // The height of a line is the ratio of the magnitude multiplied by 
                        // half the vertical resolution
                        int height = ( int )( ( double )( pcm_magnitude ) / 32768 * h / 2 );
                        // Determine the starting y coordinate - left channel above center,
                        // right channel below - currently assumes 2 channels
                        int displacement = ( h / 2 ) - ( 1 - j ) * height;
                        // Position buffer pointer using y coordinate, stride, and x coordinate
                        unsigned char *p = &bitmap[ i + displacement * w ];
                        
                        // Draw vertical line
                        for ( k = 0; k < height; k++ )
                                p[ w * k ] = 0xFF;
                        
                        pcm++;
                }
                pcm += skip * channels;
        }

        return bitmap;
}


void mlt_frame_close( mlt_frame this )
{
        if ( this != NULL && mlt_properties_dec_ref( mlt_frame_properties( this ) ) <= 0 )
        {
                mlt_deque_close( this->stack_image );
                mlt_deque_close( this->stack_audio );
                mlt_properties_close( &this->parent );
                free( this );
        }
}

/***** convenience functions *****/

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;
}

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 );

        // Optimisation point
        if ( iwidth == owidth && iheight == oheight )
                memcpy( output, input, iheight * istride );

        // 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;

        int elements;

        // Fill whole section with black
        y = out_y_range - ( iheight / 2 );
        int blank_elements = ostride * y / 2;
        elements = blank_elements;
        while ( elements -- )
        {
                *out_line ++ = 16;
                *out_line ++ = 128;
        }

        int active_width = 2 * iwidth;
        int inactive_width = out_x_range - in_x_range;
        uint8_t *p = NULL;
        uint8_t *end = NULL;

        // Loop for the entirety of our output height.
        while ( iheight -- )
        {
        // Start at the beginning of the line
        out_ptr = out_line;

                // Fill the outer part with black
                elements = inactive_width;
                while ( elements -- )
                {
                        *out_ptr ++ = 16;
                        *out_ptr ++ = 128;
                }

                // We're in the input range for this row.
                p = in_middle + in_line;
                end = out_ptr + active_width;
                while ( out_ptr != end )
                {
                        *out_ptr ++ = *p ++;
                        *out_ptr ++ = *p ++;
                }

                // Fill the outer part with black
                elements = inactive_width;
                while ( elements -- )
                {
                        *out_ptr ++ = 16;
                        *out_ptr ++ = 128;
                }

                // Move to next input line
                in_line += istride;

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

        // Fill whole section with black
        elements = blank_elements;
        while ( elements -- )
        {
                *out_line ++ = 16;
                *out_line ++ = 128;
        }
}

/** 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 = mlt_pool_alloc( owidth * ( oheight + 1 ) * 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 + 1 ) * 2, ( mlt_destructor )mlt_pool_release, 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 = mlt_pool_alloc( owidth * ( oheight + 1 ) * 2 );

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

                iwidth = iwidth - ( iwidth % 4 );

                // 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
        register uint8_t *out_line = output;
        register 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;

                // Generate the affine transform scaling values
                register int scale_width = ( iwidth << 16 ) / owidth;
                register int scale_height = ( iheight << 16 ) / oheight;
                register int base = 0;

                int outer = out_x_range * scale_width;
                int bottom = out_y_range * scale_height;

        // Loop for the entirety of our output height.
        for ( dy = - bottom; dy < bottom; dy += scale_height )
        {
                // Start at the beginning of the line
                out_ptr = out_line;
        
                // Pointer to the middle of the input line
                in_line = in_middle + ( dy >> 16 ) * istride;

                // Loop for the entirety of our output row.
                for ( dx = - outer; dx < outer; dx += scale_width )
                {
                                base = dx >> 15;
                                base &= 0xfffffffe;
                                *out_ptr ++ = *( in_line + base );
                                base &= 0xfffffffc;
                                *out_ptr ++ = *( in_line + base + 1 );
                                dx += scale_width;
                                base = dx >> 15;
                                base &= 0xfffffffe;
                                *out_ptr ++ = *( in_line + base );
                                base &= 0xfffffffc;
                                *out_ptr ++ = *( in_line + base + 3 );
                }

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

                // Now update the frame
                mlt_properties_set_data( properties, "image", output, owidth * ( oheight + 1 ) * 2, ( mlt_destructor )mlt_pool_release, 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_start, float weight_end, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
{
        int ret = 0;
        int16_t *src, *dest;
        int frequency_src = *frequency, frequency_dest = *frequency;
        int channels_src = *channels, channels_dest = *channels;
        int samples_src = *samples, samples_dest = *samples;
        int i, j;
        double d = 0, s = 0;

        mlt_frame_get_audio( this, &dest, format, &frequency_dest, &channels_dest, &samples_dest );
        //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" ) );
        mlt_frame_get_audio( that, &src, format, &frequency_src, &channels_src, &samples_src );
        //fprintf( stderr, "mix: 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;

        // determine number of samples to process
        *samples = samples_src < samples_dest ? samples_src : samples_dest;
        *channels = channels_src < channels_dest ? channels_src : channels_dest;
        *buffer = dest;
        *frequency = frequency_dest;

        // Compute a smooth ramp over start to end
        float weight = weight_start;
        float weight_step = ( weight_end - weight_start ) / *samples;

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

        return ret;
}

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

        if ( ( int )( fps * 100 ) == 2997 )
        {
                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;
}