The J300 family of video and audio products is a feature-rich set of multimedia hardware adapters developed by Digital for its Alpha workstations. This paper describes the design and implementation of the J300 software architecture, focusing on the Sound & Motion J300 product. The software approach taken was to consider the hardware as two separate devices: the J300 audio subsystem and the J300 video subsystem. Libraries corresponding to the two subsystems provide application programming interfaces that offer flexible control of the hardware while supporting a client-server model for multimedia applications. The design places special emphasis on performance by favoring an asynchronous I/O programming model implemented through an innovative use of queues. The kernel-mode device driver is portable across devices because it requires minimal knowledge of the hardware. The overall design aims at easing application programming while extracting real-time performance from a non-real-time operating system. The software architecture has been successfully implemented over multiple platforms, including those based on the OpenVMS, Microsoft Windows NT and Digital UNIX operating systems, and is the foundation on which software for Digital`s current video capture, compression and rendering hardware adapters exists.
Copyright 1995 by Digital