The present invention seeks to provide an improved file system that provides essence data for a media file in a way that does not require the contents of the entire file to be available before any file data can be provided. The present invention is reflected in a method of providing file data for a media file of a pre-determined format from a file system comprising a file record database and a data store, wherein the media file corresponds to a programme. The method comprises the steps of receiving details of the programme including the duration of the programme, and determining the layout of the media file in the pre-determined format from the received details of the programme, the layout including locations for essence data within the file. A file record for the media file is then created in the file record database. In response to a request for the location of essence data within the file, a location given by the determined layout of the media file is returned. Further, a stream of essence data corresponding to the contents of the programme is received and the received essence data is stored in the data store. In response to a request for a portion of essence data from the media file corresponding to a time period of the programme, essence data derived from the received essence data is returned according to the determined layout of the media file.