The J300 Family of Video and Audio Adapters: Architecture and Hardware Design
Kenneth W. Correll, Robert A. Ulichney · Digital technical journal · 1995
family of video and audio adapters was to provide the hardware support necessary to allow the integration of broadcast video into workstations. The three primary objectives were as follows: (1) digitized video data should be treated the same as any other data type in the system; (2) the video and the graphics subsystem designs should be completely independent of each other; and (3) any hardware designed should be low cost. Digital has implemented the J300 architecture in three products: Sound & Motion J300, FullVideo Supreme JPEG, and FullVideo Supreme. The Sound & Motion J300 (referred to in this paper simply as the J300) was the first product designed with this architecture and is the primary focus of this paper. The FullVideo Supreme JPEG and FullVideo Supreme products are based on the same design database as the J300. They differ from the J300 in the bus supported (they support the peripheral component interconnect [PCI] bus) and the lack of audio support. Additionally, the FullVideo Supreme product does not include hardware compression/decompression circuitry. The J300 brings a wide range of video and audio capabilities to machines based on Digital’s TURBOchannel I/O interconnect. Analog broadcast video can be digitized, demodulated, and rendered for display on any graphics device. The J300 provides hardware video compression and decompression to accelerate applications such as videoconferencing. The J300 supports analog broadcast video output from either compressed or uncompressed video files. Audio support includes a general-purpose, digital signal processor (DSP) to assist in the real-time management of the audio streams and for advanced processing, such as compression, decompression, and echo cancellation. Audio input and output capabilities include stereo analog I/O, digital audio I/O, and a headphone/microphone jack. Analog audio can be digitized to 16 bits per sample at a rate of up to 48 kilohertz (kHz). This paper begins with an overview of some terminology commonly used in the field of broadcast video. The paper then presents the evolution and design of the J300 architecture, including several key enabling The J300 family of video and audio adapters provides a feature-rich set of hardware options for Alpha-based workstations. Unlike earlier attempts to integrate full-motion digital video with general-purpose computer systems, the architecture and design of J300 adapters exploit fast system and I/O buses to allow video data to be treated like any other data type used by the system, independent of the graphics subsystem. This paper describes the architecture used in J300 products, the video and audio features supported, and some key aspects of the hardware design. In particular, the paper describes a simple yet versatile color-map-friendly rendering system that generates high-quality 8-bit image data.