pidff_rescale
usage->value[0] = pidff_rescale(value, U16_MAX, usage->field);
pidff_rescale(-value, -S16_MIN, usage->field);
pidff_rescale(value, S16_MAX, usage->field);
pidff_rescale(direction, U16_MAX, pidff->effect_direction);
pidff->effect_direction->value[index] = pidff_rescale(
pidff_rescale(envelope->attack_level >
pidff_rescale(envelope->fade_level >