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/*
Psychtoolbox3/Source/Common/SCREENNominalFrameRate.c
AUTHORS:
Allen.Ingling@nyu.edu awi
mario.kleiner@tuebingen.mpg.de mk
PLATFORMS:
All systems.
HISTORY:
12/04/02 awi Created.
06/07/06 mk Extended to return float precision values on request.
Extended to allow setting the framerate on systems that
support this (Currently Linux only).
DESCRIPTION:
Return the the nominal frame rate as reported by the video subsystem/driver, or
change the nominal frame rate on systems that support this.
TO DO:
*/
#include "Screen.h"
// If you change useString then also change the corresponding synopsis string in ScreenSynopsis.c
static char useString[] = "hz=Screen('NominalFrameRate', windowPtrOrScreenNumber [, mode] [, reqFrameRate]);";
static char synopsisString[] =
"Returns or sets the nominal video frame rate in Hz, as reported by your computer's video driver. "
"'FrameRate' is an alias for 'NominalFrameRate'. By default, this function returns the nominal "
"framerate, as reported by your operating system, rounded to the closest integral value. If you "
"set the optional 'mode' flag to 1, then the framerate is returned without rounding to the closest "
"integer, but at floating point precision, on systems that support this (MacOS-X and Linux). "
"GNU/Linux only: If you set the 'mode' flag to 2 and specify 'reqFrameRate', then Psychtoolbox "
"will try to change the current video refresh rate of the display: If 'reqFrameRate' is above "
"10.0, Screen will try to switch to a framerate as close as possible to 'reqFrameRate' Hz. If "
"'reqFrameRate' is a positive or negative value smaller than 10.0, then the video setting will be "
"changed by 'reqFrameRate' system dependent units. The new settings that would result are validated "
"to make sure they are safe for your display. Invalid settings are rejected, returning a value of "
"-1. On systems other than Linux, 0 is always returned to signal failure. On successfull framerate "
"change, the new resulting nominal framerate is returned with double precision. NOTE: 'reqFrameRate' "
"must be pretty close to the initial framerate, e.g. initial +/- 2 Hz. It is not possible to apply big "
"changes, e.g., from 60 Hz to 75 Hz. This function is meant for fine-tuning the video refresh interval "
"for the purpose of synchronizing different displays or the display and other stimulation- or acquisition "
"devices. You can compensate for small phase-shifts or deviations... "
"Due to manufacturing tolerances and other noise in your system, the real monitor refresh interval can "
"differ slightly from the nominal values returned by this function. To query the real, measured framerate "
"use Screen('GetFlipInterval') instead. ";
static char seeAlsoString[] = "FrameRate GetFlipInterval";
PsychError SCREENNominalFramerate(void)
{
int screenNumber, opmode;
double *rate;
double requestedHz;
//all sub functions should have these two lines
PsychPushHelp(useString, synopsisString, seeAlsoString);
if(PsychIsGiveHelp()){PsychGiveHelp();return(PsychError_none);};
//check to see if the user supplied superfluous arguments
PsychErrorExit(PsychCapNumOutputArgs(1));
PsychErrorExit(PsychCapNumInputArgs(3));
//get specified screen number and sanity check the number against the number of connected displays.
PsychCopyInScreenNumberArg(kPsychUseDefaultArgPosition, TRUE, &screenNumber);
// Get opmode. Defaults to zero for integral precision query:
opmode = 0;
PsychCopyInIntegerArg(2, FALSE, &opmode);
//Allocate a return matrix.
PsychAllocOutDoubleArg(1, FALSE, &rate);
// Query mode (0 or 1)?
if (opmode<=1) {
// Query the float precision nominal frame rate and put it into the return value:
*rate=(double) PsychGetNominalFramerate(screenNumber);
}
else {
// Query new requested framerate or mode increment:
PsychCopyInDoubleArg(3, TRUE, &requestedHz);
// Set mode: This is currently only supported on GNU/Linux:
#if PSYCH_SYSTEM == PSYCH_LINUX
// Call the Set-function, it will process and return the new nominal framerate:
*rate=(double) PsychSetNominalFramerate(screenNumber, (float) requestedHz);
#else
// Return 0 to signal the unsupported feature:
*rate = 0;
#endif
}
// Round it to closest integer, if opmode <= 0:
if (opmode <= 0) *rate = (double) ((int) (*rate + 0.5));
// Done.
return(PsychError_none);
}
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