Abstract: A logical device that is coupled to a computer can be controlled using string commands. The logical device requires flags and a data structure to operate properly. A string command with tokens for operating a specific logical device is provided. A linked list of the tokens is created. A command table for the specified logical device is found. The command table contains possible commands for the logical device, which commands are able to provide the required flags and data structure for the logical device. Each command in the command table contains key words or tokens or multiword tokens. The command table tokens are parsed, one at a time, against the command string tokens. If no match between the command table token and a command string token occurs, then the next command table token is parsed against the command string tokens.

Abstract: Disclosed are apparatus and methods for synchronized presentation of analog and digital data by applying a common synchronization scheme to both types of data. Digital data is "streamed" by transferring the data in blocks from a source to a series of memory buffers, where it accumulates for subsequent transfer to an output device driver. The control module responsible for data streaming periodically reports a temporal location within the presentation represented by the data. A supervisory module designates one of the control modules a "master", and periodically compares the values reported by the various other control modules against that reported by the master. If a comparison exceeds a threshold tolerance value associated with each control module, a sync pulse is delivered to that control module, causing it to correct the synchronization mismatch.

Abstract: Disclosed are methods and apparatus that facilitate the introduction of filters, converters and effects into an active multimedia stream without interruption of the presentation. A control module or sequence permits such introduction only after verifying the presence of a sufficient supply of buffered presentation data. Responding to a user's request for introduction of a filter, the invention first determines whether its immediate implementation would cause interruption, and either introduces the filter, converter or effect into the data stream as backlogged data continues to be presented, or postpones its introduction until sufficient buffered data does exist.