A computing system connected to storage medium and one or more rendering devices receives streamed multimedia data. The multimedia data is encoded in a format, such as an Advanced Streaming Format, that is conducive to storing the multimedia data in files having appended indexes. Upon receiving the multimedia data, the multimedia data is written to file structures within the storage medium, while at the same time maintaining a real-time index for each file in a shared memory. After a file is complete, the real-time index is appended to the completed file and deleted from the shared memory. When a request for data is received that pertains to a file that does not have an appended index, the computing system obtains any necessary file index information from the real-time index in the shared memory, thereby enabling the requested data to be accessed.