An (Matroska) file is a multimedia container that can hold video, audio, subtitle tracks, and chapters. Unlike simple streaming formats, MKV relies heavily on an internal index (also called Cues or Seek Head ) to allow fast seeking, accurate timestamp retrieval, and smooth playback.
mkvpropedit input.mkv --add-track-statistics-tags index mkv
mkvinfo yourfile.mkv
Without a proper index: