Method and system for optimising a data carousel

#The present invention relates generally to the protocol framework known as DSM-CC (Digital Storage Media—Control and Command) which allows the broadcasting of data to receivers.

#More specifically, the present invention relates to a way of constructing an Object Carousel so as to optimise the download times while a receiver is navigating a “virtual file system”.

#A full description of the DSM-CC specification may be found in ISO/IEC 13818-6. It enables a broadcaster to broadcast a “virtual file system” on top of MPEG-2 private sections. Receivers can then navigate and retrieve data from this virtual file system. The specification provides protocols for downloading software components from servers to clients. In particular, the DSM-CC system is applicable to DVB (Digital Video Broadcasting) systems which provide interactive multi-media applications such as video on demand (VOD), near video on demand (NVOD), home shopping, news on demand and electronic program guides (EPG).

#The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which:

#FIG. 1 shows schematically the messages which comprise a Data Carousel;

#FIG. 2 shows schematically a Data Carousel having various modules which are split into download data blocks;

#The present invention is based on the realisation that the construction of the Object Carousel is critical to the download time experienced by a client. Download time can be reduced by constructing the Object Carousel so that a minimum number of modules need to be downloaded and so that modules are presented on the Carousel in an order more closely representing the order in which they are likely to be downloaded.

#Typically, previous attempts at optimising the Object Carousel have proposed grouping the object representations (BIOP messages) that are used together in a single module. For example, a directory object representation would be grouped with all of the file object representations that it contains.

#In contrast to this, the present invention proposes not to group file object representations with their parent directory object representation, but instead to group all the directory object representations into a single module. Further, the present invention proposes that this module (hereinafter called the “Directory Module”) is broadcast regularly within the Carousel, for example every 10 or 15 seconds. The remaining file object representations may then be grouped into other modules, according to expected application execution patterns. These modules (hereinafter called “File Modules”) may then be distributed over the rest of the Carousel, preferably with the popular files (eg. start-up files) broadcast more frequently.