The Secondary Video Set is used for substitution of the Main Video/Main Audio streams to the corresponding streams in the Primary Video Set (Substitute Audio Video), substitution of the Main Audio stream to the corresponding sream in the Primary Video Set (Substitute Audio), or used for addition to/substitution of the Primary Video Set (Secondary Audio Video).

The Secondary Video Set may be recorded on a disc, recorded in Persisent Storage or delivered from a server. The file for the Secondary Video Set is once stored in the File Cache or Persistent Storage before playback, if the data is recorded on a disc, and it is possible to be played with the Primary Video Set simultaneously. The Secondary Video Set on a disc may be directly accessed in case that the Primary Video Set is not played back (i.e. it is not supplied from a disc). On the other hand, if the Secondary Video Set is located on a server, all of this data should be stored once in the File Cache or Persistent Storage and played back ("Complete downloading"), or a part of this data should be stored in the Streaming Buffer sequentially and played back from the buffer while downloading, without the buffer overflowing.