XSGIvc(3)XSGIvc(3)
NAME
XSGIvc - Control video operation
SYNOPSIS
The XSGIvc extension permits user control of video operation
on Silicon GraphicsTM base graphics hardware.
DESCRIPTION
This X extension provides a range of services to permit
programmatic user control of video operations on the base
graphics hardware. This extension does not provide a means
to control optional video hardware such as
SiriusVideo(Reg.); optional video is controlled via
VideoLibrary(3).
Examples of control include loading video formats, setting
video output gain, setting pedestal, and changing H-phase.
Channel
The optional notion of channel adds a tangential dimension
to the existing X hierarchy of display and Screen. Put
briefly, a single Screen's managed area may be subdivided
into channels, each a physical output which displays some or
all of the Screen. Typically, a channel's output is to a
physical connection on the server.
Some graphics hardware has only one channel; other kinds of
graphics hardware implement many channels.
Neither the OpenGL(Reg.) nor standard X drawing contain the
notion of channel, and images are simply rendered to a
single managed area, or Screen. The portions of the managed
area produced on the physical outputs are specified by the
video format or video format combination (see description of
Combination below).
Most XSGIvc functions require you specify a channel number
which specifies on which physical channel the operation
should be performed. The channel number can be specified
directly; client applications may determine the number of
channels on a server via the XSGIvcQueryVideoScreenInfo
function. Channel numbers range 0 to (numChannels - 1).
For most functions, you must also specify the screen on
which the channel is located. The macros ScreenCount and
DefaultScreen may be of some value in determining the screen
number.
A server may offer channels with varying capabilities and
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attributes, so it will not do to presume a uniform
arrangment if only one channel is queried. For each
channel, query the capabilities before performing
operations.
Controls
The video output of a graphics pipe may have a number of
alterations, or controls, that can be made to change its
operation. Different graphics hardware may support
different controls, and different channels on a single
graphics hardware may support different controls. The
calling program should query the capabilities and
characteristics of a control for a channel via the function
XSGIvcQueryChannelInfo. The documentation accompanying
graphics hardware may also contain information on which
channels controls are available.
Each control has a XSGIvcSet<control>, and a
XSGIvcQuery<control>, function associated with it. The Set
function allows you to change the setting or state of
operation. The Query function returns to you the extant
settings. The <control> is the name of the control to be
changed or queried; for example, XSGIvcSetOutputGain and
XSGIvcQueryOutputGain both deal with output gain.
The Query function returns to you information about the
capabilities or range of values permitted by the server (as
different servers may have different ranges of legal
values). The query function returns True if the server
supports the function, False if the server does not support
it. On servers with more than one output channel, you will
need to query the characteristics for each channel, since
different channels may have different capabilities.
Events unique to XSGIvc
XSGIvc offers a unique event type which has several sub-
types. One large use of these events permits the client
program to monitor changes made to the different channel's
parameters by other client programs.
Another use of events communicates asynchronous hardware
state changes (e.g., external lock status) to the client
program.
Combination
Some servers with multiple channels permit independent
alteration of video format resolution and timing. Other
servers may require that only a compatible ensemble of
formats, a combination, may be loaded. The combination may
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either reference or include other video formats; it may
additionally include frame buffer configuration information
and default control settings for both Screen and channel.
Combinations are prepared independently
FILES
The system administrator may specify configuration
information to the server extension via database files.
moninfo
Describes characteristics of different monitor models.
chantab
Describes which monitor is connected to which channel and
gives instructions regarding automatic monitor queries.
FUNCTIONS
The following are major functions available for use.
Administrative
XSGIvcQueryChannelInfo - Query channel information for a
specific channel
XSGIvcQueryVideoScreenInfo - Query video information for the
screen
Control
XSGIvcSet<control> - Set the value for a particular control
on an output channel
XSGIvcQuery<control> - Get the extant value for a particular
control on an output channel
XSGIvcLoadVideoFormat - Changes the video format of a
channel
SEE ALSO
X, XSGIvcSetOutputPhaseSCH, XSGIvcSetOutputGain,
XSGIvcSetOutputPhaseV, XSGIvcSetOutputPedestal,
XSGIvcSetOutputPhaseH, XSGIvcSetOutputSync,
XSGIvcStoreGammaColors8, moninfo, chantab
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