The InfiniteReality video display subsystem takes rendered images from the raster subsystem digital framebuffer and processes the pixels through digital-to-analog converters (DACs) to generate an analog pixel stream suitable for display on a high-resolution RGB video monitor. The display subsystem supports programmable pixel timings so that the system can drive displays with a wide variety of resolutions, refresh rates, and interlace/noninterlace characteristics.
Use the Combiner only with Onyx InfiniteReality or i-Station graphics systems. For RealityEngine2 and VTX graphics systems, you must use the video out panel or other custom applications.
The InfiniteReality hardware includes either two or eight independent video channels in the standard configuration. The second video channel serves a dual role as a standard RGB video channel or as a composite or S-Video encoder.
For the InfiniteReality video graphics display subsystem, Silicon Graphics provides a configuration utility, the Video Format Combiner, ircombine(1G). The Combiner groups video output formats into a video format combination—descriptions of raster sizes and timing to be used on video outputs— to validate that they operate correctly on the InfiniteReality video display subsystem hardware. The Combiner also configures the underlying graphics framebuffer and instructs the video subsystem to convert digital information stored there into a variety of video signals, or channels, ranging from high-resolution to low-resolution outputs. The output can then be displayed on additional monitors or projection devices, or stored on videotape, in any combination. Output can be genlocked to an external reference signal.
This chapter discusses
 | Note: For more information on ircombine, consult its man (reference) page, ircombine(1G). |
All channels derive their pixels from areas on the raster (framebuffer area). You can use the Combiner to select any area of the screen, or the contents of any window on the screen, as channel input; channels can overlap. A convenience feature allows you to click a specific window on the screen for channel input. You can also copy one channel's format to another.
InfiniteReality's multichannel feature takes the digital, ordered pixel output from the framebuffer and allows you to specify two to eight separate rectangular areas to be sent from the rectangular framebuffer area managed by the X Window System to independent component RGB video outputs. Each video channel can have its own video timing. This capability is particularly useful for applications such as visual simulation, virtual reality, or entertainment.
After you set up the channels, you can save them as a video format combination. You can download a video format combination into the hardware as the current video configuration, store it as the default configuration to be used at system power-on or graphics initialization, or save it in a video format combination file. You can create a combination from scratch or by modifying a current or default combination or a previously saved combination. The Combiner software includes sample combinations.
Video output combinations include “combinations” of a single video output format.
The Onyx2 accommodates video option boards: Sirius Video, Digital Video Port (DVP), and Graphics to Video Option (GVO). These options appear as dedicated channels in the Video Format Combiner interface.
The Sirius Video option is available for applications that require live video input. Data from the Sirius Video board's two inputs can be blended using incoming alpha-key blending, internal chroma-key generation, or a key generated in real time from InfiniteReality graphics.
If the Sirius Video option is installed, you can use its dedicated channel for its output. You can configure this Sirius Video channel to use a high-resolution channel as input, set it up to pass pixels through or filter them, and set other options as well.
The Sirius Video Programming and Configuration Guide (007-2238-003 or later) describes this option.
The Digital Video Port (DVP) option board provides digital video data from the InfiniteReality framebuffer in raster-scan order, left to right, top to bottom, one pixel at a time, at the pixel clock rate. Pixel data is 36 bits wide (12 bits per RGB component). It can also access 16-bit luminance information.
If the DVP option is installed, you can use its dedicated channel to set configuration, timing, and so on.
The Graphics to Video Option (GVO) allows you to output CCIR 601 serial digital video from the graphics frame buffer. GVO by itself is perfect for output of graphics to digital video in real time. This board is a daughtercard installed on a Display Generator (DG) board that has two channels only (DG5-2); the two DG5 channels remain available.