DATA STREAMING BETWEEN PEER SUBSYSTEMS OF A COMPUTER

摘要

A data handling arrangement for a computer system, with particular application to multimedia systems, allows device adapters (control units) attached to the system to autonomously (without interrupting the system processor) control processing of a data stream of arbitrary length through memory buffers which are smaller than the stream. In this (stream processing) operation, data constituting the data stream flows through devices controlled by the adapter in succession, and is held in shared memory buffers as it passes between devices. The adapters are prepared for the stream processing operation by a system processor, indicate their preparation status to the processor, receive an initiating signal from the processor, and then proceed to direct the operation to completion without further assistance from the processor. In the operation, the adapters coordinate usage of the memory buffers by respective devices. Coordination is accomplished using a notification signalling protocol defined during preparation of the adapters. For notifying each other of buffer events (filling, emptying, etc.), the adapters use a peer communication feature of a system channel which connects the adapters and devices to the system processor and memory. This feature permits one adapter to directly communicate "notification" information to another control unit without involving the system processor. Information furnished to the adapters during their preparation includes descriptors defining the memory buffers and the notification protocol. It also may include descriptors enabling a control unit to synchronize the processing of data in a stream with events external to the stream; e.g. an external timer function or events associated with the processing of another data stream. Thus, for instance, video and audio components of a live motion picture presentation could be synchronized. The controlling functions affecting stream processing are isolated from the controlled devices, and the processing functions performed by each device on data in a stream are performed independent of the functions performed by any other device relative to the same stream; thereby simplifying development of new devices and new processing functions.