GA_computeCRTCTimings

Compute the VESA GTF timings for a display mode

Declaration

ibool NAPI GA_computeCRTCTimings(
GA_devCtx *dc,
GA_modeInfo *modeInfo,
N_int32 refreshRate,
N_int32 interlaced,
GA_CRTCInfo *crtc,
N_int32 pureGTF)

Prototype In

snap/graphics.h

Parameters

dc | Device context for driver to compute timings for
modeInfo | SuperVGA mode information block for the mode
refreshRate | Desired refresh rate to generate timings for
interlaced | True if the CRTC timings should be interlaced
crtc | Place to store the computed CRTC timings
pureGTF | True to use pure GTF formulas

Return Value

True on success, or false if refresh rate is out of range.

Description

This function computes a set of CRTC timings for the specific graphics mode at the specified refresh rate. The CRTC timings are computed using the VESA GTF timing formulas, combined with information returned by the SNAP driver. Note that the exact refresh rate that you get will not be exactly what you requested, and the exact value is returned in the CRTC information block block.

If the pureGTF parameter is set to true, we will leave the CRTC timings as is after the GTF formulas have computed the appropriate timings for the refresh rate given the closest available pixel clock. This means that we may not be able to hit a specific refresh rate exactly, but the CRTC timings will be GTF compliant. In some cases it may be more beneficial to hit an exact refresh rate on the nail (such as when viewing sterero images) and in order to do this we will modify the horizontal and vertical totals slightly to compensate for the granularity in the pixel clock (which in some cases may be quite large).

See Also

GA_getMaxRefreshRate

Copyright © 2002 SciTech Software, Inc. Visit our web site at http://www.scitechsoft.com