/****************************************************************************
*
* VESA Generalized Timing Formula (GTF)
* Version 1.1
*
* ========================================================================
*
* The contents of this file are subject to the SciTech MGL Public
* License Version 1.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.scitechsoft.com/mgl-license.txt
*
* Software distributed under the License is distributed on an
* "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is Copyright (C) 1991-1998 SciTech Software, Inc.
*
* The Initial Developer of the Original Code is SciTech Software, Inc.
* All Rights Reserved.
*
* ========================================================================
*
* Developed by: SciTech Software, Inc.
*
* Language: ANSI C
* Environment: Any.
*
* Description: C module for generating GTF compatible timings given a set
* of input requirements. Translated from the original GTF
* 1.14 spreadsheet definition.
*
* Compile with #define TESTING to build a command line test
* program.
*
* NOTE: The code in here has been written for clarity and
* to follow the original GTF spec as closely as
* possible.
*
****************************************************************************/
#include "gtf.h"
#ifndef __WIN32_VXD__
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#endif
/*------------------------- Global Variables ------------------------------*/
static GTF_constants GC = {
1.8, /* Margin size as percentage of display */
8, /* Character cell granularity */
1, /* Minimum front porch in lines/chars */
3, /* Width of V sync in lines */
8, /* Width of H sync as percent of total */
550, /* Minimum vertical sync + back porch (us) */
600, /* Blanking formula gradient */
40, /* Blanking formula offset */
128, /* Blanking formula scaling factor */
20, /* Blanking formula scaling factor weight */
};
/*-------------------------- Implementation -------------------------------*/
#ifdef __WIN32_VXD__
/* These functions are not supported in a VxD, so we stub them out so this
* module will at least compile. Calling the functions in here will do
* something wierd!
*/
double sqrt(double x)
{ return x; }
double floor(double x)
{ return x; }
double pow(double x,double y)
{ return x*y; }
#endif
static double round(double v)
{
return floor(v + 0.5);
}
static void GetInternalConstants(GTF_constants *c)
/****************************************************************************
*
* Function: GetInternalConstants
* Parameters: c - Place to store the internal constants
*
* Description: Calculates the rounded, internal set of GTF constants.
* These constants are different to the real GTF constants
* that can be set up for the monitor. The calculations to
* get these real constants are defined in the 'Work Area'
* after the constants are defined in the Excel spreadsheet.
*
****************************************************************************/
{
c->margin = GC.margin;
c->cellGran = round(GC.cellGran);
c->minPorch = round(GC.minPorch);
c->vSyncRqd = round(GC.vSyncRqd);
c->hSync = GC.hSync;
c->minVSyncBP = GC.minVSyncBP;
if (GC.k == 0)
c->k = 0.001;
else
c->k = GC.k;
c->m = (c->k / 256) * GC.m;
c->c = (GC.c - GC.j) * (c->k / 256) + GC.j;
c->j = GC.j;
}
void GTF_calcTimings(double hPixels,double vLines,double freq,
int type,ibool wantMargins,ibool wantInterlace,GTF_timings *t)
/****************************************************************************
*
* Function: GTF_calcTimings
* Parameters: hPixels - X resolution
* vLines - Y resolution
* freq - Frequency (Hz, KHz or MHz depending on type)
* type - 1 - vertical, 2 - horizontal, 3 - dot clock
* margins - True if margins should be generated
* interlace - True if interlaced timings to be generated
* t - Place to store the resulting timings
*
* Description: Calculates a set of GTF timing parameters given a specified
* resolution and vertical frequency. The horizontal frequency
* and dot clock will be automatically generated by this
* routines.
*
* For interlaced modes the CRTC parameters are calculated for
* a single field, so will be half what would be used in
* a non-interlaced mode.
*
****************************************************************************/
{
double interlace,vFieldRate,hPeriod;
double topMarginLines,botMarginLines;
double leftMarginPixels,rightMarginPixels;
double hPeriodEst,vSyncBP,vBackPorch;
double vTotalLines,vFieldRateEst;
double hTotalPixels,hTotalActivePixels,hBlankPixels;
double idealDutyCycle,hSyncWidth,hSyncBP,hBackPorch;
double idealHPeriod;
double vFreq,hFreq,dotClock;
GTF_constants c;
/* Get rounded GTF constants used for internal calculations */
GetInternalConstants(&c);
/* Move input parameters into appropriate variables */
vFreq = hFreq = dotClock = freq;
/* Round pixels to character cell granularity */
hPixels = round(hPixels / c.cellGran) * c.cellGran;
/* For interlaced mode halve the vertical parameters, and double
* the required field refresh rate.
*/
vFieldRate = vFreq;
interlace = 0;
if (wantInterlace)
dotClock *= 2;
/* Determine the lines for margins */
if (wantMargins) {
topMarginLines = round(c.margin / 100 * vLines);
botMarginLines = round(c.margin / 100 * vLines);
}
else {
topMarginLines = 0;
botMarginLines = 0;
}
if (type != GTF_lockPF) {
if (type == GTF_lockVF) {
/* Estimate the horizontal period */
hPeriodEst = ((1/vFieldRate) - (c.minVSyncBP/1000000)) /
(vLines + (2*topMarginLines) + c.minPorch + interlace) * 1000000;
/* Find the number of lines in vSync + back porch */
vSyncBP = round(c.minVSyncBP / hPeriodEst);
}
else if (type == GTF_lockHF) {
/* Find the number of lines in vSync + back porch */
vSyncBP = round((c.minVSyncBP * hFreq) / 1000);
}
/* Find the number of lines in the V back porch alone */
vBackPorch = vSyncBP - c.vSyncRqd;
/* Find the total number of lines in the vertical period */
vTotalLines = vLines + topMarginLines + botMarginLines + vSyncBP
+ interlace + c.minPorch;
if (type == GTF_lockVF) {
/* Estimate the vertical frequency */
vFieldRateEst = 1000000 / (hPeriodEst * vTotalLines);
/* Find the actual horizontal period */
hPeriod = (hPeriodEst * vFieldRateEst) / vFieldRate;
/* Find the actual vertical field frequency */
vFieldRate = 1000000 / (hPeriod * vTotalLines);
}
else if (type == GTF_lockHF) {
/* Find the actual vertical field frequency */
vFieldRate = (hFreq / vTotalLines) * 1000;
}
}
/* Find the number of pixels in the left and right margins */
if (wantMargins) {
leftMarginPixels = round(hPixels * c.margin) / (100 * c.cellGran);
rightMarginPixels = round(hPixels * c.margin) / (100 * c.cellGran);
}
else {
leftMarginPixels = 0;
rightMarginPixels = 0;
}
/* Find the total number of active pixels in image + margins */
hTotalActivePixels = hPixels + leftMarginPixels + rightMarginPixels;
if (type == GTF_lockVF) {
/* Find the ideal blanking duty cycle */
idealDutyCycle = c.c - ((c.m * hPeriod) / 1000);
}
else if (type == GTF_lockHF) {
/* Find the ideal blanking duty cycle */
idealDutyCycle = c.c - (c.m / hFreq);
}
else if (type == GTF_lockPF) {
/* Find ideal horizontal period from blanking duty cycle formula */
idealHPeriod = (((c.c - 100) + (sqrt((pow(100-c.c,2)) +
(0.4 * c.m * (hTotalActivePixels + rightMarginPixels +
leftMarginPixels) / dotClock)))) / (2 * c.m)) * 1000;
/* Find the ideal blanking duty cycle */
idealDutyCycle = c.c - ((c.m * idealHPeriod) / 1000);
}
/* Find the number of pixels in blanking time */
hBlankPixels = round((hTotalActivePixels * idealDutyCycle) /
((100 - idealDutyCycle) * c.cellGran)) * c.cellGran;
/* Find the total number of pixels */
hTotalPixels = hTotalActivePixels + hBlankPixels;
/* Find the horizontal back porch */
hBackPorch = round((hBlankPixels / 2) / c.cellGran) * c.cellGran;
/* Find the horizontal sync width */
hSyncWidth = round(((c.hSync/100) * hTotalPixels) / c.cellGran) * c.cellGran;
/* Find the horizontal sync + back porch */
hSyncBP = hBackPorch + hSyncWidth;
if (type == GTF_lockPF) {
/* Find the horizontal frequency */
hFreq = (dotClock / hTotalPixels) * 1000;
/* Find the number of lines in vSync + back porch */
vSyncBP = round((c.minVSyncBP * hFreq) / 1000);
/* Find the number of lines in the V back porch alone */
vBackPorch = vSyncBP - c.vSyncRqd;
/* Find the total number of lines in the vertical period */
vTotalLines = vLines + topMarginLines + botMarginLines + vSyncBP
+ interlace + c.minPorch;
/* Find the actual vertical field frequency */
vFieldRate = (hFreq / vTotalLines) * 1000;
}
else {
if (type == GTF_lockVF) {
/* Find the horizontal frequency */
hFreq = 1000 / hPeriod;
}
else if (type == GTF_lockHF) {
/* Find the horizontal frequency */
hPeriod = 1000 / hFreq;
}
/* Find the pixel clock frequency */
dotClock = hTotalPixels / hPeriod;
}
/* Return the computed frequencies */
t->vFreq = vFieldRate;
t->hFreq = hFreq;
t->dotClock = dotClock;
/* Determine the vertical timing parameters */
t->h.hTotal = (int)hTotalPixels;
t->h.hDisp = (int)hTotalActivePixels;
t->h.hSyncStart = t->h.hTotal - (int)hSyncBP;
t->h.hSyncEnd = t->h.hTotal - (int)hBackPorch;
t->h.hFrontPorch = t->h.hSyncStart - t->h.hDisp;
t->h.hSyncWidth = (int)hSyncWidth;
t->h.hBackPorch = (int)hBackPorch;
/* Determine the vertical timing parameters */
t->v.vTotal = (int)vTotalLines;
t->v.vDisp = (int)vLines;
t->v.vSyncStart = t->v.vTotal - (int)vSyncBP;
t->v.vSyncEnd = t->v.vTotal - (int)vBackPorch;
t->v.vFrontPorch = t->v.vSyncStart - t->v.vDisp;
t->v.vSyncWidth = (int)c.vSyncRqd;
t->v.vBackPorch = (int)vBackPorch;
if (wantInterlace) {
/* Halve the timings for interlaced modes */
t->v.vTotal /= 2;
t->v.vDisp /= 2;
t->v.vSyncStart /= 2;
t->v.vSyncEnd /= 2;
t->v.vFrontPorch /= 2;
t->v.vSyncWidth /= 2;
t->v.vBackPorch /= 2;
t->dotClock /= 2;
}
/* Mark as GTF timing using the sync polarities */
t->interlace = (wantInterlace) ? 'I' : 'N';
t->hSyncPol = '-';
t->vSyncPol = '+';
}
void GTF_getConstants(GTF_constants *constants)
{ *constants = GC; }
void GTF_setConstants(GTF_constants *constants)
{ GC = *constants; }
#ifdef TESTING_GTF
void main(int argc,char *argv[])
{
FILE *f;
double xPixels,yPixels,freq;
ibool interlace;
GTF_timings t;
if (argc != 5 && argc != 6) {
printf("Usage: GTFCALC <xPixels> <yPixels> <freq> [[Hz] [KHz] [MHz]] [I]\n");
printf("\n");
printf("where <xPixels> is the horizontal resolution of the mode, <yPixels> is the\n");
printf("vertical resolution of the mode. The <freq> value will be the frequency to\n");
printf("drive the calculations, and will be either the vertical frequency (in Hz)\n");
printf("the horizontal frequency (in KHz) or the dot clock (in MHz). To generate\n");
printf("timings for an interlaced mode, add 'I' to the end of the command line.\n");
printf("\n");
printf("For example to generate timings for 640x480 at 60Hz vertical:\n");
printf("\n");
printf(" GTFCALC 640 480 60 Hz\n");
printf("\n");
printf("For example to generate timings for 640x480 at 31.5KHz horizontal:\n");
printf("\n");
printf(" GTFCALC 640 480 31.5 KHz\n");
printf("\n");
printf("For example to generate timings for 640x480 with a 25.175Mhz dot clock:\n");
printf("\n");
printf(" GTFCALC 640 480 25.175 MHz\n");
printf("\n");
printf("GTFCALC will print a summary of the results found, and dump the CRTC\n");
printf("values to the UVCONFIG.CRT file in the format used by SciTech Display Doctor.\n");
exit(1);
}
/* Get values from command line */
xPixels = atof(argv[1]);
yPixels = atof(argv[2]);
freq = atof(argv[3]);
interlace = ((argc == 6) && (argv[5][0] == 'I'));
/* Compute the CRTC timings */
if (toupper(argv[4][0]) == 'H')
GTF_calcTimings(xPixels,yPixels,freq,GTF_lockVF,false,interlace,&t);
else if (toupper(argv[4][0]) == 'K')
GTF_calcTimings(xPixels,yPixels,freq,GTF_lockHF,false,interlace,&t);
else if (toupper(argv[4][0]) == 'M')
GTF_calcTimings(xPixels,yPixels,freq,GTF_lockPF,false,interlace,&t);
else {
printf("Unknown command line!\n");
exit(1);
}
/* Dump summary info to standard output */
printf("CRTC values for %.0fx%.0f @ %.2f %s\n", xPixels, yPixels, freq, argv[4]);
printf("\n");
printf(" hTotal = %-4d vTotal = %-4d\n",
t.h.hTotal, t.v.vTotal);
printf(" hDisp = %-4d vDisp = %-4d\n",
t.h.hDisp, t.v.vDisp);
printf(" hSyncStart = %-4d vSyncStart = %-4d\n",
t.h.hSyncStart, t.v.vSyncStart);
printf(" hSyncEnd = %-4d vSyncEnd = %-4d\n",
t.h.hSyncEnd, t.v.vSyncEnd);
printf(" hFrontPorch = %-4d vFrontPorch = %-4d\n",
t.h.hFrontPorch, t.v.vFrontPorch);
printf(" hSyncWidth = %-4d vSyncWidth = %-4d\n",
t.h.hSyncWidth, t.v.vSyncWidth);
printf(" hBackPorch = %-4d vBackPorch = %-4d\n",
t.h.hBackPorch, t.v.vBackPorch);
printf("\n");
printf(" Interlaced = %s\n", (t.interlace == 'I') ? "Yes" : "No");
printf(" H sync pol = %c\n", t.hSyncPol);
printf(" V sync pol = %c\n", t.vSyncPol);
printf("\n");
printf(" Vert freq = %.2f Hz\n", t.vFreq);
printf(" Horiz freq = %.2f KHz\n", t.hFreq);
printf(" Dot Clock = %.2f Mhz\n", t.dotClock);
/* Dump to file in format used by SciTech Display Doctor */
if ((f = fopen("UVCONFIG.CRT","w")) != NULL) {
fprintf(f, "[%.0f %.0f]\n", xPixels, yPixels);
fprintf(f, "%d %d %d %d '%c' %s\n",
t.h.hTotal, t.h.hDisp,
t.h.hSyncStart, t.h.hSyncEnd,
t.hSyncPol, (t.interlace == 'I') ? "I" : "NI");
fprintf(f, "%d %d %d %d '%c'\n",
t.v.vTotal, t.v.vDisp,
t.v.vSyncStart, t.v.vSyncEnd,
t.vSyncPol);
fprintf(f, "%.2f\n", t.dotClock);
fclose(f);
}
}
#endif /* TESTING */
