}
break;
+ case REWIND:
+ start_position = 0;
case CURRENT_FRAME:
case LAST_FRAME:
case SINGLE_FRAME_FWD:
end_position = start_position + frame_period;
break;
+ case GOTO_END:
+ end_position = length;
case SINGLE_FRAME_REWIND:
start_position = end_position - frame_period;
break;