int mlt_animation_get_item( mlt_animation self, mlt_animation_item item, int position )
{
int error = 0;
// Need to find the nearest keyframe to the position specifed
animation_node node = self->nodes;
// Iterate through the keyframes until we reach last or have
while ( node && node->next && position >= node->next->item.frame )
node = node->next;
if ( node )
{
item->keyframe_type = node->item.keyframe_type;
// Position is before the first keyframe.
if ( position < node->item.frame )
{
item->is_key = 0;
if ( item->property )
mlt_property_pass( item->property, node->item.property );
}
// Item exists.
else if ( position == node->item.frame )
{
item->is_key = node->item.is_key;
if ( item->property )
mlt_property_pass( item->property, node->item.property );
}
// Position is after the last keyframe.
else if ( !node->next )
{
item->is_key = 0;
if ( item->property )
mlt_property_pass( item->property, node->item.property );
}
// Interpolation needed.
else
{
double progress;
mlt_property points[4];
points[0] = node->prev? node->prev->item.property : node->item.property;
points[1] = node->item.property;
points[2] = node->next->item.property;
points[3] = node->next->next? node->next->next->item.property : node->next->item.property;
progress = position - node->item.frame;
progress /= node->next->item.frame - node->item.frame;
mlt_property_interpolate( item->property, points, progress,
self->fps, self->locale, item->keyframe_type );
item->is_key = 0;
}
}
else
{
item->frame = item->is_key = 0;
error = 1;
}
item->frame = position;
return error;
}
void mlt_animation_interpolate( mlt_animation self )
{
// Parse all items to ensure non-keyframes are calculated correctly.
if ( self->nodes )
{
animation_node current = self->nodes;
while ( current )
{
if ( !current->item.is_key )
{
double progress;
mlt_property points[4];
animation_node prev = current->prev;
animation_node next = current->next;
while ( prev && !prev->item.is_key ) prev = prev->prev;
while ( next && !next->item.is_key ) next = next->next;
if ( !prev ) {
current->item.is_key = 1;
prev = current;
}
if ( !next ) {
next = current;
}
points[0] = prev->prev? prev->prev->item.property : prev->item.property;
points[1] = prev->item.property;
points[2] = next->item.property;
points[3] = next->next? next->next->item.property : next->item.property;
progress = current->item.frame - prev->item.frame;
progress /= next->item.frame - prev->item.frame;
mlt_property_interpolate( current->item.property, points, progress,
self->fps, self->locale, current->item.keyframe_type );
}
// Move to the next item
current = current->next;
}
}
}