rem: csetup_repp->change_position_exact(seconds); csetup_repp->seek_position(); if (csetup_repp->double_buffering() == true) csetup_repp->pserver_repp->flush();
add: csetup_repp->seek_position_in_seconds(csetup_repp->position_in_seconds() + seconds);
context: void ECA_ENGINE::change_position(double seconds) {  conditional_stop();  csetup_repp->change_position_exact(seconds);  csetup_repp->seek_position();  if (csetup_repp->double_buffering() == true) csetup_repp->pserver_repp->flush();  conditional_start();}