The Present invention relates to electronic data processing, and more specifically concerns managing the flow of streaming data through multiple hardware and/or software processing modules in a computer.
Streaming data is a continuous flow of data that must be ultimately presented to a user in a particular sequence in real time. Digital samples representing an audio signal, for example, must be converted to a sound wave in the same sequence they were transmitted, and at exactly the time spacing they were generated, or some user-specified alternative. Digital data representing video frames require assembly into the proper sequence in the frame for presentation on a display together, and successive frames must display at the correct real-time rate.
Streaming data need not necessarily maintain correct sequence or timing throughout an entire communication chain among various transmitters, processors, memories, and receivers. Indeed, video and audio clips are frequently stored as static data in recording media, computer memory, and network buffers. Packet-switched systems might also carry parts of the same streaming data over different paths and even in different time sequences. Processors such as digital filters can assemble parts of the data stream, modify them as a static unit, then release them to further units in the system. Eventually, however, the stream must be heard or seen in the correct sequence at the proper relative times.
Streaming data almost always involves very large amounts of data. Streaming data almost always challenges the capacity of digital buses in computers to access it, carry it and switch it. Streaming data almost always taxes the processing power of functional units, both software and hardware, to receive it, convert it, and pass it on to other units. Those in the art speak of the necessity of xe2x80x9cfat pipesxe2x80x9d for streaming data.
An abstract model has been developed to represent the connections among various facilities in a computer that are required to process a given type of streaming data. For example, a video clip might require MPEG decoding in a dedicated chip, rasterizing the video fields in another hardware module, digital filtering of the audio in a software module, insertion of subtitles by another software module, D/A conversion of the video in a video adapter card, and D/A conversion of the audio in a separate audio card. A number of different types of memory in different locations can store the data between successive operations, and a number of buses can be made available to transport the data.
An architecture called WDM-CSA (Windows Driver Model Connection and Streaming Architecture) introduces the concept of a graph for specifying the connections among the facilities of a computer where a data stream must pass through a number of processing units in an efficient manner. The WDM-CSA protocol also simplifies the development of drivers for such data. Basically, WDM-CSA specifies the flow of data frames through a graph, and also the control protocols by which adjacent modules in the graph communicate with each other to request and accept the data frames.
Commonly assigned patent application Ser. No. 09/310,610 xe2x80x9cImproving the Flow of Streaming Data through Multiple Processing Units,xe2x80x9d filed on even date herewith, introduces the concept of data pipes for enhancing the efficiency of transporting data frames through a graph of interconnected modules in WDM-CSA and in other streaming-data environments. That application is incorporated herein by reference. Basically, data pipes avoid redundant storage and copying of data as a number of modules process the frames, and streamline allocation of the frames in which the data is packaged.
However, further inefficiencies occur in conventional control protocols for managing the transport of streaming data through multiple hardware and/or software modules interconnected in pipes, graphs, and similar arrangements.
The simplest and fastest method of controlling such data is a dedicated protocol for transporting frames in a hard-wired, unchanging configuration of modules. This option is not practical for environments such as a personal computer or multimedia system capable of receiving many different kinds of streaming data in multiple formats, especially where a number of manufacturers provide the individual modules. Also, of course, introduction of new data types and new modules would require upgrading an entire system, rather than substituting components individually.
The other extreme is a one-size-fits-all protocol capable of handling a broad spectrum of data types and formats, and a wide range of modules. A number of computer operating systems provide this kind of protocol. The Windows(copyright) 2000 operating system from Microsoft Corp., for example, incorporates an I/O Manager subsystem that accommodates the connection of multiple driver and filter modules in a chain between a data source and a data sink. This protocol is very flexible, and works reliably with a variety of data types, including streaming data. But flexibility almost always sacrifices speed. The very features that permit broad applicability often lead to redundancy and lower efficiency in particular situations.
Streaming data does require high speed and efficient control. The use of multiple reconfigurable modules also requires flexibility. Conventional control of streaming data has maximized one of these goals to the derogation of the other. This important emerging technology requires an improved control mechanism that achieves the very efficient control of a dedicated protocol, and yet allows enough flexibility for different data types, different modules, and different configurations in the environment of streaming data transported in frames through multiple processing modules.
The present invention proposes a mechanism for controlling the flow of streaming data packaged in frames or similar units through a graph or network of multiple processing modules. The mechanism improves the speed and efficiency of general-purpose mechanisms, while retaining the flexibility to accommodate many different kinds of data, data packages, and processing modules, and to permit the interconnection of those modules into arbitrary graphs or other configurations for achieving overall operations upon the streaming data.
The proposed mechanism is conceptually uncomplicated, and in fact can simplify the design of modules that incorporate it, in many cases. The mechanism coexists with conventional protocols, and permits their use for other kinds of data in other applications.
Basically, the mechanism employs a set of components that can be used and combined among themselves to implement control functions at the control pins of processing modules. The components can include a source pin, a sink pin, a queue, a requestor, and an optional splitter.
When the components are defined and implemented as control pins in a number of hardware and/or software modules, the control pins of the modules are selected and connected together to form a desired graph for processing the streaming data. Although the control pins perform more or less standard functions when viewed from outside the modules, the interconnections in a specific graph frequently reveal redundant or superfluous internal functions as between adjacent modules in that graph. In these cases, the invention bypasses the connected control pins so as to remove the unnecessary functions, and connects the internal mechanism components to each other directly. In this way, control packets for frames of the streaming data can be transported through the graph more efficiently.
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