Update sys.

sys/sys_top.v

@@ -124,6 +124,12 @@ module sys_top
 	inout   [6:0] USER_IO
 );
 
+`ifdef MISTER_DUAL_SDRAM
+	`ifndef MISTER_DISABLE_YC
+		`define MISTER_DISABLE_YC
+	`endif
+`endif
+
 //////////////////////  Secondary SD  ///////////////////////////////////
 wire SD_CS, SD_CLK, SD_MOSI;
 

sys/vga_out.sv

@@ -16,14 +16,16 @@ module vga_out
 	output reg    csync_o
 );
 
-wire [5:0] red   = din[23:18];
+wire [7:0] red   = din[23:16];
-wire [5:0] green = din[15:10];
+wire [7:0] green = din[15:8];
-wire [5:0] blue  = din[7:2];
+wire [7:0] blue  = din[7:0];
 
 // http://marsee101.blog19.fc2.com/blog-entry-2311.html
-// Y  =  16 + 0.257*R + 0.504*G + 0.098*B (Y  =  0.299*R + 0.587*G + 0.114*B)
+
-// Pb = 128 - 0.148*R - 0.291*G + 0.439*B (Pb = -0.169*R - 0.331*G + 0.500*B)
+
-// Pr = 128 + 0.439*R - 0.368*G - 0.071*B (Pr =  0.500*R - 0.419*G - 0.081*B)
+// Y  =       0.301*R + 0.586*G + 0.113*B (Y  =  0.299*R + 0.587*G + 0.114*B)
+// Pb = 128 - 0.168*R - 0.332*G + 0.500*B (Pb = -0.169*R - 0.331*G + 0.500*B)
+// Pr = 128 + 0.500*R - 0.418*G - 0.082*B (Pr =  0.500*R - 0.419*G - 0.081*B)
 
 reg  [7:0] y, pb, pr;
 reg [23:0] rgb;
@@ -36,25 +38,25 @@ always @(posedge clk) begin
 	reg hsync2, vsync2, csync2;
 	reg hsync1, vsync1, csync1;
 
-	y_1r  <= 19'd04096 + ({red, 8'd0} + {red, 3'd0});
+	y_1r <= {red, 6'd0} + {red, 3'd0} + {red, 2'd0} + red;
-	pb_1r <= 19'd32768 - ({red, 7'd0} + {red, 4'd0} + {red, 3'd0});
+	pb_1r <= 19'd32768 - ({red, 5'd0} + {red, 3'd0} + {red, 1'd0});
-	pr_1r <= 19'd32768 + ({red, 8'd0} + {red, 7'd0} + {red, 6'd0});
+	pr_1r <= 19'd32768 + {red, 7'd0};
 
-	y_1g  <= {green, 9'd0} + {green, 2'd0};
+	y_1g  <= {green, 7'd0} + {green, 4'd0} + {green, 2'd0} + {green, 1'd0};
-	pb_1g <= {green, 8'd0} + {green, 5'd0} + {green, 3'd0};
+	pb_1g <= {green, 6'd0} + {green, 4'd0} + {green, 2'd0} + green;
-	pr_1g <= {green, 8'd0} + {green, 6'd0} + {green, 5'd0} + {green, 4'd0} + {green, 3'd0};
+	pr_1g <= {green, 6'd0} + {green, 5'd0} + {green, 3'd0} + {green, 1'd0};
 
-	y_1b  <= {blue, 6'd0} + {blue, 5'd0} + {blue, 2'd0};
+	y_1b  <= {blue, 4'd0} + {blue, 3'd0} + {blue, 2'd0} + blue;
-	pb_1b <= {blue, 8'd0} + {blue, 7'd0} + {blue, 6'd0};
+	pb_1b <= {blue, 7'd0};
-	pr_1b <= {blue, 6'd0} + {blue, 3'd0};
+	pr_1b <= {blue, 4'd0} + {blue, 2'd0} + blue;
 
 	y_2  <= y_1r  + y_1g  + y_1b;
 	pb_2 <= pb_1r - pb_1g + pb_1b;
 	pr_2 <= pr_1r - pr_1g - pr_1b;
 
-	y  <= ( y_2[18] ||  !y_2[17:12]) ? 8'd16 : (y_2[17:8] > 235) ? 8'd235 :  y_2[15:8];
+	y  <= y_2[18] ? 8'd0 : y_2[16] ? 8'd255 :  y_2[15:8];
-	pb <= (pb_2[18] || !pb_2[17:12]) ? 8'd16 : (&pb_2[17:12])    ? 8'd240 : pb_2[15:8];
+	pb <= pb_2[18] ? 8'd0 : pb_2[16] ? 8'd255 : pb_2[15:8];
-	pr <= (pr_2[18] || !pr_2[17:12]) ? 8'd16 : (&pr_2[17:12])    ? 8'd240 : pr_2[15:8];
+	pr <= pr_2[18] ? 8'd0 : pr_2[16] ? 8'd255 : pr_2[15:8];
 
 	hsync_o <= hsync2; hsync2 <= hsync1; hsync1 <= hsync;
 	vsync_o <= vsync2; vsync2 <= vsync1; vsync1 <= vsync;

sys/video_freak.sv

@@ -173,7 +173,7 @@ sys_umul #(12,12) mul(CLK_VIDEO,mul_start,mul_run, mul_arg1,mul_arg2,mul_res);
 wire [11:0] wideres = mul_res[11:0] + hsize;
 
 always @(posedge CLK_VIDEO) begin
-	reg [11:0] oheight,wres;
+	reg [11:0] oheight,htarget,wres;
 	reg [12:0] arxf,aryf;
 	reg  [3:0] cnt;
 	reg        narrow;
@@ -188,11 +188,18 @@ always @(posedge CLK_VIDEO) begin
 	else if(~div_start & ~div_run & ~mul_start & ~mul_run) begin
 		cnt <= cnt + 1'd1;
 		case(cnt)
+			// example ideal and non-ideal cases:
+			// [1] 720x400 4:3 VGA 80x25 text-mode (non-square pixels)
+			// [2] 640x480 4:3 VGA graphics mode (square pixels)
+			// [3] 512x512 4:3 X68000 graphics mode (non-square pixels)
 			0: begin
 					div_num   <= HDMI_HEIGHT;
 					div_den   <= vsize;
 					div_start <= 1;
 				end
+				// [1] 1080 / 400 -> 2
+				// [2] 1080 / 480 -> 2
+				// [3] 1080 / 512 -> 2
 
 			1: if(!div_res[11:0]) begin
 					// screen resolution is lower than video resolution.
@@ -206,6 +213,9 @@ always @(posedge CLK_VIDEO) begin
 					mul_arg2  <= div_res[11:0];
 					mul_start <= 1;
 				end
+				// [1] 1080 / 400 * 400 -> 800
+				// [2] 1080 / 480 * 480 -> 960
+				// [3] 1080 / 512 * 512 -> 1024
 
 			2: begin
 					oheight   <= mul_res[11:0];
@@ -219,24 +229,39 @@ always @(posedge CLK_VIDEO) begin
 					mul_arg2  <= arx_i;
 					mul_start <= 1;
 				end
+				// [1] 1080 / 400 * 400 * 4 -> 3200
+				// [2] 1080 / 480 * 480 * 4 -> 3840
+				// [3] 1080 / 512 * 512 * 4 -> 4096
 
 			4: begin
 					div_num   <= mul_res;
 					div_den   <= ary_i;
 					div_start <= 1;
 				end
+				// [1] 1080 / 480 * 480 * 4 / 3 -> 1066
+				// [2] 1080 / 480 * 480 * 4 / 3 -> 1280
+				// [3] 1080 / 512 * 512 * 4 / 3 -> 1365
+				// saved as htarget
 
 			5: begin
+					htarget   <= div_res[11:0];
 					div_num   <= div_res;
 					div_den   <= hsize;
 					div_start <= 1;
 				end
+				// computes wide scaling factor as a ceiling division
+				// [1] 1080 / 400 * 400 * 4 / 3 / 720 -> 1
+				// [2] 1080 / 480 * 480 * 4 / 3 / 640 -> 2
+				// [3] 1080 / 512 * 512 * 4 / 3 / 512 -> 2
 
 			6: begin
 					mul_arg1  <= hsize;
 					mul_arg2  <= div_res[11:0] ? div_res[11:0] : 12'd1;
 					mul_start <= 1;
 				end
+				// [1] 1080 / 400 * 400 * 4 / 3 / 720 * 720 -> 720
+				// [2] 1080 / 480 * 480 * 4 / 3 / 640 * 640 -> 1280
+				// [3] 1080 / 512 * 512 * 4 / 3 / 512 * 512 -> 1024
 
 			7: if(mul_res <= HDMI_WIDTH) begin
 					cnt       <= 10;
@@ -247,17 +272,32 @@ always @(posedge CLK_VIDEO) begin
 					div_den   <= hsize;
 					div_start <= 1;
 				end
+				// [1] 1920 / 720 -> 2
+				// [2] 1920 / 640 -> 3
+				// [3] 1920 / 512 -> 3
 
 			9: begin
 					mul_arg1  <= hsize;
 					mul_arg2  <= div_res[11:0] ? div_res[11:0] : 12'd1;
 					mul_start <= 1;
 				end
+				// [1] 1920 / 720 * 720 -> 1440
+				// [2] 1920 / 640 * 640 -> 1920
+				// [3] 1920 / 512 * 512 -> 1536
 
 			10: begin
-					narrow    <= ((div_num[11:0] - mul_res[11:0]) <= (wideres - div_num[11:0])) || (wideres > HDMI_WIDTH);
+					narrow    <= ((htarget - mul_res[11:0]) <= (wideres - htarget)) || (wideres > HDMI_WIDTH);
-					wres      <= wideres;
+					wres      <= mul_res[11:0] == htarget ? mul_res[11:0] : wideres;
 				end
+				// [1] 1066 - 720  = 346 <= 1440 - 1066 = 374 || 1440 > 1920 -> true
+				// [2] 1280 - 1280 = 0   <= 1920 - 1280 = 640 || 1920 > 1920 -> true
+				// [3] 1365 - 1024 = 341 <= 1536 - 1365 = 171 || 1536 > 1920 -> false
+				// 1. narrow flag is true when mul_res[11:0] narrow width is closer to
+				//    htarget aspect ratio target width or when wideres wider width
+				//    does not fit to the screen.
+				// 2. wres becomes wideres only when mul_res[11:0] narrow width not equal
+				//    to target width, meaning it is not optimal for source aspect ratio.
+				//    otherwise it is set to narrow width that is optimal.
 
 			11: begin
 					case(SCALE)