Note: Silicon Graphics also offers Cosmo Compress(tm), an option card providing compression and decompression of incoming and outgoing video to the CCITT/ISO JPEG standard. For information on Cosmo Compress, see the Silicon Studio Technical Report.
Video display does not affect workstation performance, since the Indy Video card performs all input, scaling and switching between graphics pixels and video pixels in real time.
Almost all of the full graphics screen (1280x960) or an NTSC- or PAL-sized portion of it may be output in real time. The output is taken from the graphics subsystem frame buffer and scan converted with flicker reduction and filtering. The outputting and scan converting are performed by the video board, so they place no additional demands on the workstation CPU or graphics subsystem. This filtered scaling is set in the hardware to 2:1 for NTSC output and 5:3 for PAL output.
All output signals are low-pass-filtered and sin x/x-corrected. The board has a notch filter that an application may select as needed. It reduces the cross-chroma artifacts created when dithered graphics images are encoded to composite video.
Applications may use the board as a frame buffer to record single frames to a frame-accurate VTR.
The standard video inputs can be used as the source of the graphics subsystem input to the keyer/mixer circuitry on the Indy Video option card. Using the standard video input from the Indy Video option card allows keying and mixing of two composite or Y/C video channels.
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YUV 525/60 Square Pixel 625/50 Square Pixel
Component
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Y 12.2727 MHz 14.75 MHz
U (B-Y) 6.13635 MHz 7.375 MHz
V (R-Y) 6.13635 MHz 7.375 MHz
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Composite and S-VHS analog output is converted from 4:2:2 YUV by a Philips 7199 encoder and reconstructed with a 5-MHz low-pass filter and sin x/x correction.
Data in the port is sampled as square-pixel 4:2:2 YUV with 8-bits per channel:
Digitized video is converted to RGB in a dedicated frame buffer. Note this frame buffer is not shown on the block diagram. It resides in the scan converter block and is not shown because it is not accessible by applications or end users. The buffer may be displayed at full 24-bit resolution (8 bits per component) or split into two half-resolution, 12-bit planes (4 bits per component). All three windows (one 24-bit and two 12-bit) may be displayed at the same time, or two 24-bit windows may be displayed.
Although the video may be displayed on the workstation monitor at 12-bit resolution all 24 bits of data are available to Indy Video and the system. Note the following restrictions apply to all video windows:
Framelocking the graphics frame rates to input can be performed which allows for smooth graphics output to video without repeat or skip frames.
Source Destination
Analog video in Analog Video out
Digital video in 1 Digital Video out
Digital video in 2 Host memory (frame buffer input)
Host memory (frame buffer output) Alpha blender foreground
Alpha blender pixels Alpha blender background
Alpha blender alpha Graphics 1 (24-bit resolution)
Graphics A (24-bit resolution) Graphics 2 (12-bit or 24-bit resolution)
Graphics B (24-bit resolution) Graphics 3 (12-bit resolution)
Keys are created on a pixel-by-pixel basis. Indy Video applies mathematical formulas to the Y and U-V values of each pixel in a selected portion of an image, producing an alpha value for that portion. It blends this value with the corresponding alpha of the remainder of the image:
Pixels may be chosen in three ways:
Dedicated registers containing the YUV values of a flat field background may be used for fades to and from any color.
Note: For more information please refer to the Video Library Programmer's Guide.
Libraries insure that upgrades are compatible with current releases, that applications developed for one product can be ported easily to other products, and that functions provided by one library interface reliably and consistently with the functions of other libraries.
The software consists of the following:
The basic model for the library is the video stream. Library routines manage the video stream by defining a source device, a destination device and the path between the two. Parameters called controls modify the path; all devices should recognize a subset of common controls.
Applications written to the square-pixel Video Library API will be able to access the other Silicon Graphics libraries, such as Compression Library(tm) and Graphics Library(tm).
To illustrate how to use the library, the source code for each tool and control panel is also provided.
The basic tools are outlined as follows:
Use this graphical user interface to set controls, such as hue or contrast, on devices. The panel resizes itself dynamically to reflect available video devices.
The tools vlinfo, vidtomem, and memtovid are command line tools. In addition to their man pages, these tools are explained in the IRIS Utilities Guide.
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Board Function Specification Value
Compatibility Television standard NTSC
PAL
Sampling Square-pixel NTSC 12.27 MHz, 640 pixels/line
Square-pixel PAL 14.75 MHz, 768 pixels/line
4:2:2 YUV 8-bits/component, U and V sub-sampled by 2
Input connectors Composite 2 RCA
Y/C (S-VHS) 1 S-VHS (4-pin DIN)
Output connectors Composite 1 RCA
Y/C (S-VHS) 1 S-VHS
Composite Input Color separation Chrominance trap only
Aperture filters Selectable
Coring Selectable up to ±3 LSB
Hue control ±180
Chroma gain Automatic
Luminance gain Automatic
Differential phase 4
Chrominance-luminance gain ± 4%
Composite output Operating modes Genlocked or stand-alone
Horizontal phase 3 µsec advance to 1 µsec delay
Horizontal blanking Fixed at the following rates:
11.4 µsec NTSC square pixel
11.9 µsec PAL square pixel
Vertical blanking Adjustable through all vertical interval lines
SC-H phase ±180
Differential phase 1
Differential gain 1%
Chrominance-luminance gain ± 2%
Chrominance-luminance delay ± 20 nsec
Frequency response 4.2 MHz - 2 dB
Blanking level output voltage ±0.25 V
S/N ratio 48 dB
Board Function Specification Value
Y/C (S-VHS) input Aperture filters Selectable
Coring Selectable up to ±3 LSB
Hue control ±180
Chroma gain Automatic
Luminance gain Automatic
Differential phase 4
Differential gain 4%
Chrominance-luminance gain ± 4%
Chrominance-luminance delay ± 40 nsec
Frequency response 4.2 MHz -3 dB (Y only)
Frame buffers Number 4
Bandwidth to CPU 1.5 Mpixels/sec maximum
Readback to CPU decimation 2x or 4x, with or without anti-alias filtering
Data format 4:2:2 YUV, 8 bits/component
Graphics-to-video Reduction ratios, with anti-alias filtering 2:1 NTSC square-pixel; 5:3 PAL square-pixel
conversion Flicker reduction Selectable
Color space conversion accuracy ±1 LSB
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