Markers may be used to indicate various events (like track start/end, important parts of a song etc.). They can be manually added using number keys. To enable markers, use --markers [file] command line option (they will be saved in file).
Marker file consists of lines, one per marker. The format is:
[marker_number]: [marker_time_in_ticks]
Example:
1: 4422
2: 15961
3: 19417