51Figure 4-32 Playback MarkDuring 1-window playback mode, click mark file list button in Figure 4-29, you can goto mark file list interface. Double click one mark file, you can begin playback from the marktime. Play before mark timeHere you can set to begin playback from previous N seconds of the mark time.NoteUsually, systems can playbacks previous N seconds record if there is such kind of recordfile. Otherwise, system playbacks from the previous X seconds when there is such as kindof record. Mark ManagerClick the mark manager button on the Playback interface (Figure 4-29); you cango to Mark Manager interface. SeeFigure 4-33. System can manage all the record mark information of current channel bydefault. You can view all mark information of current channel by time.Figure 4-33 ModifyDouble click one mark information item, you can see system pops up a dialogue box foryou to change mark information. You can only change mark name here. DeleteHere you can select the mark information item you want to delete and then click Deletebutton, you can remove one mark item. .