// Initialise transition previous mix value to prevent an inadvertant jump from 0
mlt_position last_position = mlt_properties_get_position( properties, "_last_position" );
mlt_position current_position = mlt_frame_get_position( b_frame );
+ mlt_properties_set_position( properties, "_last_position", current_position );
if ( mlt_properties_get( properties, "_previous_mix" ) == NULL
|| current_position != last_position + 1 )
mlt_properties_set_double( properties, "_previous_mix", mix );