This appendix takes a high-level look at the SunVideo card's four hardware subsystems, which are shown in Figure C-1.
Figure C-1 The SunVideo Card
The video-capture subsystem accepts video in either NTSC or PAL formats and performs the video signal processing that is required to separate luminance and chrominance information. The subsystem digitizes the analog input and passes the digital bytestream to the compression engine.
The video-capture subsystem is implemented with A/D converters, a Square Pixel Digital Multi-Standard Decoder (DMSD), and a Phase Locked Loop (PLL).
The compression engine, a programmable video-rate processor, is implemented with a C-Cube CL4000 chip. The CL4000 compresses the digital data, using CellB, JPEG, MPEG-1, or UYVY. The compressor software, provided with the SunVideo subsystem, is downloaded to the compression engine under control of an XIL application.
The data memory buffer is used by the CL4000 compression engine to store the intermediate results of the compression operations. The amount of data that is stored in the buffer can be set from XIL (with the MAX_BUFFERS attribute), which enables applications to control performance and latency.
The SBus-video interface connects the SunVideo card and the host workstation's SBus. The subsystem is implemented with an ASIC and an OpenBoot PROM.
The OpenBoot PROM contains Power On Self Test (POST) tests that verify the card's operation. In addition, the OpenBoot PROM contains extended POST diagnostic programs that support more extensive tests.
