Modeline Calculator https://arachnoid.com/modelines/

gtf.rb

#!/usr/bin/ruby -w
=begin

 * gtf.rb Copyright (c) 2008, Paul Lutus
 * Released under the GPL

 * This Ruby program is largely based on:
 * -------------------------------------------------------------
 * gtf.c  Generate mode timings using the GTF Timing Standard
 *
 * Copyright (c) 2001, Andy Ritger  aritger@nvidia.com
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * o Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * o Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer
 *   in the documentation and/or other materials provided with the
 *   distribution.
 * o Neither the name of NVIDIA nor the names of its contributors
 *   may be used to endorse or promote products derived from this
 *   software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
=end

class Mode
   attr_accessor :hr, :hss, :hse, :hbl, :hfl, :vr, :vbase, :vss, :vse, :vfl, :pclk, :h_freq, :v_freq, :interlace, :interlaced
end

class Options
   attr_accessor :x, :y,:v_freq,:xf86mode,:interlaced,:margins
   def initialize()
      @xf86mode = true
      @margins = false
      @interlaced = false
   end
end

class Gtf
   # constants from GTF specification
   MARGIN_PERCENT    = 1.8   # % of active vertical image
   CELL_GRAN         = 8.0   # assumed character cell granularity
   MIN_PORCH         = 1     # minimum front porch
   V_SYNC_RQD        = 3     # width of vsync in lines
   H_SYNC_PERCENT    = 8.0   # width of hsync as % of total line
   MIN_VSYNC_PLUS_BP = 550.0 # min time of vsync + back porch (microsec)
   M                 = 600.0 # blanking formula gradient
   C                 = 40.0  # blanking formula offset
   K                 = 128.0 # blanking formula scaling factor
   J                 = 20.0  # blanking formula scaling factor

   def initialize()
      @verbose = false
      compute()
   end

   # imitate the effect of "rint()" from the math.c library
   def rint(v)
      return ((v+0.5).to_i).to_f
   end

   def print_verbose(n, name, val)
      if (@verbose)
         printf("%2d: %-27s: %15f\n", n, name, val);
      end
   end

   def print_xf86_mode (m)
      s_int1 = (m.interlaced)?"i":""
      s_int2 = (m.interlaced)?" interlace":""

      printf("\n  # %dx%d @ %.2f Hz (GTF) hsync: %.2f kHz; pclk: %.2f MHz\n",
      m.hr, m.vbase, m.v_freq, m.h_freq, m.pclk)

      printf("  Modeline \"%dx%d_%.2f%s\"  %.2f" +
      "  %d %d %d %d" +
      "  %d %d %d %d" +
      "  -HSync +Vsync%s\n\n",
      m.hr, m.vbase, m.v_freq, s_int1, m.pclk,
      m.hr, m.hss, m.hse, m.hfl,
      m.vr, m.vss, m.vse, m.vfl,s_int2)

   end

   def print_fb_mode (m)
      printf("\nmode \"%dx%d %.2fHz 32bit (GTF)\"\n",
      m.hr, m.vbase, m.v_freq)
      printf("    # PCLK: %.2f MHz, H: %.2f kHz, V: %.2f Hz\n",
      m.pclk, m.h_freq, m.v_freq)
      printf("    geometry %d %d %d %d 32\n",
      m.hr, m.vbase, m.hr, m.vr)
      printf("    timings %d %d %d %d %d %d %d\n",
      rint(1000000.0/m.pclk),     # pixclock in picoseconds
      m.hfl - m.hse,              # left margin (in pixels)
      m.hss - m.hr,               # right margin (in pixels)
      m.vfl - m.vse,              # upper margin (in pixel lines)
      m.vss - m.vr,               # lower margin (in pixel lines)
      m.hse - m.hss,              # horizontal sync length (in pixels)
      m.vse - m.vss);             # vert sync length (in pixel lines)
      printf("    hsync low\n")
      printf("    vsync high\n")
      printf("    laced true\n") if m.interlaced
      printf("endmode\n\n")
   end

   def comp_stage_1(options)

=begin
    /*  1. In order to give correct results, the number of horizontal
     *  pixels requested is first processed to ensure that it is divisible
     *  by the character size, by rounding it to the nearest character
     *  cell boundary:
     *
     *  [H PIXELS RND] = ((ROUND([H PIXELS]/[CELL GRAN RND],0))*[CELLGRAN RND])
     */
=end

      h_pixels_rnd = rint(options.x.to_f / CELL_GRAN) * CELL_GRAN
      print_verbose(1, "[H PIXELS RND]", h_pixels_rnd)

=begin
         /*  2. If interlace is requested, the number of vertical lines assumed
         *  by the calculation must be halved, as the computation calculates
         *  the number of vertical lines per field. In either case, the
         *  number of lines is rounded to the nearest integer.
         *
         *  [V LINES RND] = IF([INT RQD?]="y", ROUND([V LINES]/2,0),
         *                                     ROUND([V LINES],0))
         */
=end

      v_lines_rnd = (options.interlaced)?
      rint(options.y.to_f)/ 2.0 :
      rint(options.y.to_f);
      print_verbose(2, "[V LINES RND]", v_lines_rnd);

=begin
         /*  3. Find the frame rate required:
         *
         *  [V FIELD RATE RQD] = IF([INT RQD?]="y", [I/P FREQ RQD]*2,
         *                                          [I/P FREQ RQD])
         */
=end

      v_field_rate_rqd = (options.interlaced)? (options.v_freq * 2.0) : (options.v_freq);
      print_verbose(3, "[V FIELD RATE RQD]", v_field_rate_rqd);

=begin
         /*  4. Find number of lines in Top margin:
         *
         *  [TOP MARGIN (LINES)] = IF([MARGINS RQD?]="Y",
         *          ROUND(([MARGIN%]/100*[V LINES RND]),0),
         *          0)
         */
=end

      top_margin = (options.margins)? rint(MARGIN_PERCENT / 100.0 * v_lines_rnd) : (0.0);
      print_verbose(4, "[TOP MARGIN (LINES)]", top_margin);

=begin
         /*  5. Find number of lines in Bottom margin:
         *
         *  [BOT MARGIN (LINES)] = IF([MARGINS RQD?]="Y",
         *          ROUND(([MARGIN%]/100*[V LINES RND]),0),
         *          0)
         */
=end

      bottom_margin = (options.margins)? rint(MARGIN_PERCENT/100.0 * v_lines_rnd) : (0.0)
      print_verbose(5, "[BOT MARGIN (LINES)]", bottom_margin);

=begin
           /*  6. If interlace is required, then set variable [INTERLACE]=0.5:
            *
            *  [INTERLACE]=(IF([INT RQD?]="y",0.5,0))
            */
=end

      interlace = (options.interlaced)? 0.5 : 0.0;
      print_verbose(6, "[INTERLACE]", interlace);

=begin
            /*  7. Estimate the Horizontal period
            *
            *  [H PERIOD EST] = ((1/[V FIELD RATE RQD]) - [MIN VSYNC+BP]/1000000) /
            *                    ([V LINES RND] + (2*[TOP MARGIN (LINES)]) +
            *                     [MIN PORCH RND]+[INTERLACE]) * 1000000
            */
=end

      h_period_est = (((1.0/v_field_rate_rqd) - (MIN_VSYNC_PLUS_BP/1000000.0)) /
      (v_lines_rnd + (2*top_margin) + MIN_PORCH + interlace) * 1000000.0)
      print_verbose(7, "[H PERIOD EST]", h_period_est);

=begin
            /*  8. Find the number of lines in V sync + back porch:
            *
            *  [V SYNC+BP] = ROUND(([MIN VSYNC+BP]/[H PERIOD EST]),0)
            */
=end

      vsync_plus_bp = rint(MIN_VSYNC_PLUS_BP/h_period_est);
      print_verbose(8, "[V SYNC+BP]", vsync_plus_bp);

=begin
            /*  9. Find the number of lines in V back porch alone:
            *
            *  [V BACK PORCH] = [V SYNC+BP] - [V SYNC RND]
            *
            *  XXX is "[V SYNC RND]" a typo? should be [V SYNC RQD]?
            */
=end

      v_back_porch = vsync_plus_bp - V_SYNC_RQD;
      print_verbose(9, "[V BACK PORCH]", v_back_porch);

=begin
            /*  10. Find the total number of lines in Vertical field period:
            *
            *  [TOTAL V LINES] = [V LINES RND] + [TOP MARGIN (LINES)] +
            *                    [BOT MARGIN (LINES)] + [V SYNC+BP] + [INTERLACE] +
            *                    [MIN PORCH RND]
            */
=end

      total_v_lines = v_lines_rnd + top_margin + bottom_margin + vsync_plus_bp +
      interlace + MIN_PORCH;
      print_verbose(10, "[TOTAL V LINES]", total_v_lines);

=begin
            /*  11. Estimate the Vertical field frequency:
            *
            *  [V FIELD RATE EST] = 1 / [H PERIOD EST] / [TOTAL V LINES] * 1000000
            */
=end

      v_field_rate_est = 1.0 / h_period_est / total_v_lines * 1000000.0;
      print_verbose(11, "[V FIELD RATE EST]", v_field_rate_est);

=begin
            /*  12. Find the actual horizontal period:
            *
            *  [H PERIOD] = [H PERIOD EST] / ([V FIELD RATE RQD] / [V FIELD RATE EST])
            */
=end

      h_period = h_period_est / (v_field_rate_rqd / v_field_rate_est);
      print_verbose(12, "[H PERIOD]", h_period);

=begin
            /*  13. Find the actual Vertical field frequency:
            *
            *  [V FIELD RATE] = 1 / [H PERIOD] / [TOTAL V LINES] * 1000000
            */
=end

      v_field_rate = 1.0 / h_period / total_v_lines * 1000000.0;
      print_verbose(13, "[V FIELD RATE]", v_field_rate);

=begin
            /*  14. Find the Vertical frame frequency:
            *
            *  [V FRAME RATE] = (IF([INT RQD?]="y", [V FIELD RATE]/2, [V FIELD RATE]))
            */
=end

      v_frame_rate = (options.interlaced)? v_field_rate / 2.0 : v_field_rate;
      print_verbose(14, "[V FRAME RATE]", v_frame_rate);

=begin
            /*  15. Find number of pixels in left margin:
            *
            *  [LEFT MARGIN (PIXELS)] = (IF( [MARGINS RQD?]="Y",
            *          (ROUND( ([H PIXELS RND] * [MARGIN%] / 100 /
            *                   [CELL GRAN RND]),0)) * [CELL GRAN RND],
            *          0))
            */
=end

      left_margin = (options.margins)?
      rint(h_pixels_rnd * MARGIN_PERCENT / 100.0 / CELL_GRAN) * CELL_GRAN :
      0.0;
      print_verbose(15, "[LEFT MARGIN (PIXELS)]", left_margin);

=begin
            /*  16. Find number of pixels in right margin:
            *
            *  [RIGHT MARGIN (PIXELS)] = (IF( [MARGINS RQD?]="Y",
            *          (ROUND( ([H PIXELS RND] * [MARGIN%] / 100 /
            *                   [CELL GRAN RND]),0)) * [CELL GRAN RND],
            *          0))
            */
=end

      right_margin = (options.margins)?
      rint(h_pixels_rnd * MARGIN_PERCENT / 100.0 / CELL_GRAN) * CELL_GRAN :
      0.0
      print_verbose(16, "[RIGHT MARGIN (PIXELS)]", right_margin);

=begin
            /*  17. Find total number of active pixels in image and left and right
            *  margins:
            *
            *  [TOTAL ACTIVE PIXELS] = [H PIXELS RND] + [LEFT MARGIN (PIXELS)] +
            *                          [RIGHT MARGIN (PIXELS)]
            */
=end

      total_active_pixels = h_pixels_rnd + left_margin + right_margin;
      print_verbose(17, "[TOTAL ACTIVE PIXELS]", total_active_pixels);

=begin
            /*  18. Find the ideal blanking duty cycle from the blanking duty cycle
            *  equation:
            *
            *  [IDEAL DUTY CYCLE] = [C'] - ([M']*[H PERIOD]/1000)
            */
=end

      ideal_duty_cycle = (((C - J) * K/256.0) + J) - ((K/256.0 * M) * h_period / 1000.0);
      print_verbose(18, "[IDEAL DUTY CYCLE]", ideal_duty_cycle);

=begin
            /*  19. Find the number of pixels in the blanking time to the nearest
            *  double character cell:
            *
            *  [H BLANK (PIXELS)] = (ROUND(([TOTAL ACTIVE PIXELS] *
            *                               [IDEAL DUTY CYCLE] /
            *                               (100-[IDEAL DUTY CYCLE]) /
            *                               (2*[CELL GRAN RND])), 0))
            *                       * (2*[CELL GRAN RND])
            */
=end

      h_blank = rint(total_active_pixels *
      ideal_duty_cycle /
      (100.0 - ideal_duty_cycle) /
      (2.0 * CELL_GRAN)) * (2.0 * CELL_GRAN);
      print_verbose(19, "[H BLANK (PIXELS)]", h_blank);

=begin
            /*  20. Find total number of pixels:
            *
            *  [TOTAL PIXELS] = [TOTAL ACTIVE PIXELS] + [H BLANK (PIXELS)]
            */
=end

      total_pixels = total_active_pixels + h_blank;
      print_verbose(20, "[TOTAL PIXELS]", total_pixels);

=begin
            /*  21. Find pixel clock frequency:
            *
            *  [PIXEL FREQ] = [TOTAL PIXELS] / [H PERIOD]
            */
=end

      pixel_freq = total_pixels / h_period;
      print_verbose(21, "[PIXEL FREQ]", pixel_freq);

=begin
            /*  22. Find horizontal frequency:
            *
            *  [H FREQ] = 1000 / [H PERIOD]
            */
=end

      h_freq = 1000.0 / h_period;
      print_verbose(22, "[H FREQ]", h_freq);

      m = Mode.new


      m.hr  = (h_pixels_rnd).to_i
      m.hbl = h_blank.to_i
      m.hfl = (total_pixels).to_i

      m.vbase  = options.y # non-interlaced vertical line count
      m.vr  = (v_lines_rnd).to_i
      m.vfl = (total_v_lines).to_i

      m.pclk   = pixel_freq
      m.h_freq = h_freq
      m.v_freq = options.v_freq
      m.interlace = interlace # the value
      m.interlaced = options.interlaced # the flag

      return(m)
   end # comp_stage_1()

   def comp_stage_2(m)

=begin
               /*  17. Find the number of pixels in the horizontal sync period:
               *
               *  [H SYNC (PIXELS)] =(ROUND(([H SYNC%] / 100 * [TOTAL PIXELS] /
               *                             [CELL GRAN RND]),0))*[CELL GRAN RND]
               */
=end

      h_sync = rint(H_SYNC_PERCENT/100.0 * m.hfl / CELL_GRAN) * CELL_GRAN;
      print_verbose(17, "[H SYNC (PIXELS)]", h_sync);

=begin
               /*  18. Find the number of pixels in the horizontal front porch period:
               *
               *  [H FRONT PORCH (PIXELS)] = ([H BLANK (PIXELS)]/2)-[H SYNC (PIXELS)]
               */
=end

      h_front_porch = (m.hbl / 2.0) - h_sync;
      print_verbose(18, "[H FRONT PORCH (PIXELS)]", h_front_porch);

=begin
               /*  36. Find the number of lines in the odd front porch period:
               *
               *  [V ODD FRONT PORCH(LINES)]=([MIN PORCH RND]+[INTERLACE])
               */
=end

      v_odd_front_porch_lines = MIN_PORCH + m.interlace;
      print_verbose(36, "[V ODD FRONT PORCH(LINES)]", v_odd_front_porch_lines)

      m.hss = (m.hr + h_front_porch).to_i
      m.hse = (m.hr + h_front_porch + h_sync).to_i
      m.vss = (m.vr + v_odd_front_porch_lines).to_i
      m.vse = (m.vr + v_odd_front_porch_lines + V_SYNC_RQD).to_i

      if(m.interlaced)
         m.vr *= 2;
         m.vss *= 2;
         m.vse *= 2;
         m.vfl *= 2;
      end

      return(m)

   end # comp_stage_2()

   def usage()
      printf("\nusage: %s x y refresh [options]\n\n", __FILE__)
      puts("Required arguments:\n")
      puts("              x   : the desired horizontal resolution, pixels (example 640)\n")
      puts("              y   : the desired vertical resolution, pixels (example 480)\n")
      puts("        refresh   : the desired refresh rate, Hz (example 60)\n")
      puts("Options:\n")
      puts("  -m|--margins    : include standard image margins (#{MARGIN_PERCENT}%)\n")
      puts("  -i|--interlaced : interlaced video mode\n")
      puts("  -v|--verbose    : print all intermediate values\n")
      puts("  -x|--xf86mode   : output an XFree86-style mode description (default)\n")
      puts("  -f|--fbmode     : output an fbset(8)-style mode description\n\n")
   end

   def parse_command_line()
      if ARGV.size < 3 # not enough args
         usage()
         return false
      else # ARGV count valid
         options = Options.new
         options.x = ARGV.shift.to_i
         options.y = ARGV.shift.to_i
         options.v_freq = ARGV.shift.to_f
         if(options.x == 0 || options.y == 0 || options.v_freq == 0)
            usage()
            return false
         end
         ARGV.each do |arg|
            case arg
            when "-v","--verbose"
               @verbose = true;
            when "-f","--fbmode"
               options.xf86mode = false;
            when "-x","--xf86mode"
               options.xf86mode = true;
            when "-i","--interlaced"
               options.interlaced = true;
            when "-m","--margins"
               options.margins = true;
            else # option error
               usage()
               return false
            end # case
         end # ARGV.each do
      end # ARGV count valid
      return options
   end # parse_command_line()

   def compute()
      if(options = parse_command_line())
         m = comp_stage_1(options)
         m = comp_stage_2(m)
         if (options.xf86mode)
            print_xf86_mode(m)
         else
            print_fb_mode(m)
         end
      end # if options valid
   end # main()
end # class Gtf

gtf = Gtf.new