To enable record and reproduction control of isochronous data from a controller such as PC etc. to be performed after defining a command for recording and reproducing about a camcorder using a memory medium capable of random access.

Reproduction and recording are made to be performed after designating a file name by adding a PLAYFILE, RECORDFILE command for Isochronous Profile to a Camera Storage subunit. Data to be input and output from a subunit plug and a file to be recorded and reproduced are made to be related by a controller after adding a PLUGINFO command.