edid-decode: add support for CVT RBv3

This new CVT 1.2 reduced blanking formula was published in the CVT 1.2
Errata E1 and is used by CTA-861 and DisplayID 2.0.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

4 files changed, 38 insertions, 15 deletions

diff --git a/calc-gtf-cvt.cpp b/calc-gtf-cvt.cpp
index 78c64c3..bc32ea0 100644
--- a/calc-gtf-cvt.cpp
+++ b/calc-gtf-cvt.cpp
@@ -126,12 +126,9 @@ void edid_state::edid_gtf_mode(unsigned refresh, struct timings &t)
 
 // If rb == RB_CVT_V2, then alt means video-optimized (i.e. 59.94 instead of 60 Hz, etc.).
 // If rb == RB_CVT_V3, then alt means that rb_h_blank is 160 instead of 80.
-// Note: for RB_CVT_V3 this calculation is slightly different, but
-// since CVT 1.3 is not yet public, I cannot update the calculation yet. For now
-// it will follow V2. So RBv3 timings will be off for now.
 timings edid_state::calc_cvt_mode(unsigned h_pixels, unsigned v_lines,
 				  double ip_freq_rqd, unsigned rb, bool int_rqd,
-				  bool margins_rqd, bool alt)
+				  bool margins_rqd, bool alt, unsigned rb_h_blank)
 {
 	timings t = {};
 
@@ -159,6 +156,14 @@ timings edid_state::calc_cvt_mode(unsigned h_pixels, unsigned v_lines,
 	double v_blank;
 	double v_sync_bp;
 
+	if (rb == RB_CVT_V3 && rb_h_blank) {
+		h_blank = rb_h_blank & ~7;
+		if (h_blank < 80)
+			h_blank = 80;
+		else if (h_blank > 200)
+			h_blank = 200;
+	}
+
 	/* Determine VSync Width from aspect ratio */
 	if ((t.vact * 4 / 3) == t.hact)
 		v_sync = 4;
@@ -204,8 +209,11 @@ timings edid_state::calc_cvt_mode(unsigned h_pixels, unsigned v_lines,
 		else
 			v_sync_bp = v_sync + CVT_MIN_V_BPORCH;
 		double total_pixels = h_blank + total_active_pixels;
-		pixel_freq = floor((v_field_rate_rqd * total_v_lines * total_pixels / 1000000.0 *
-				    refresh_multiplier) / clock_step) * clock_step;
+		double freq = v_field_rate_rqd * total_v_lines * total_pixels * refresh_multiplier;
+		if (rb == RB_CVT_V3)
+			pixel_freq = ceil((freq / 1000000.0) / clock_step) * clock_step;
+		else
+			pixel_freq = floor((freq / 1000000.0) / clock_step) * clock_step;
 	}
 
 	t.vbp = v_sync_bp - v_sync;
@@ -213,8 +221,11 @@ timings edid_state::calc_cvt_mode(unsigned h_pixels, unsigned v_lines,
 	t.vfp = v_blank - t.vbp - t.vsync;
 	t.pixclk_khz = round(1000.0 * pixel_freq);
 	t.hsync = h_sync;
-	t.hfp = (h_blank / 2.0) - t.hsync;
-	t.hbp = t.hfp + t.hsync;
+	if (rb == RB_CVT_V3)
+		t.hfp = 8;
+	else
+		t.hfp = (h_blank / 2.0) - t.hsync;
+	t.hbp = h_blank - t.hfp - t.hsync;
 	t.hborder = hor_margin;
 	t.vborder = vert_margin;
 	t.rb = rb;
diff --git a/edid-decode.1 b/edid-decode.1
index e87570f..ecd7fe3 100644
--- a/edid-decode.1
+++ b/edid-decode.1
@@ -148,6 +148,8 @@ DMT 1.3: VESA and Industry Standards and Guidelines for Computer Display Monitor
 .TP
 CVT 1.2: VESA Coordinated Video Timings (CVT) Standard, Version 1.2
 .TP
+CVT 1.2: VESA CVT v1.2 Errata E1
+.TP
 GTF 1.1: VESA Generalized Timing Formula Standard, Version: 1.1
 .RE
 
@@ -253,7 +255,7 @@ Show the timings for this VIC.
 \fB\-\-hdmi\-vic\fR \fI<hdmivic>\fR
 Show the timings for this HDMI VIC.
 .TP
-\fB\-\-cvt\fR \fBw\fR=\fI<width>\fR,\fBh\fR=\fI<height>\fR,\fBfps\fR=\fI<fps>\fR[,\fBrb\fR=\fI<rb>\fR][,\fBinterlaced\fR][,\fBoverscan\fR][,\fBalt\fR]
+\fB\-\-cvt\fR \fBw\fR=\fI<width>\fR,\fBh\fR=\fI<height>\fR,\fBfps\fR=\fI<fps>\fR[,\fBrb\fR=\fI<rb>\fR][,\fBinterlaced\fR][,\fBoverscan\fR][,\fBalt\fR][,\fBhblank\fR=\fI<hblank>\fR]
 .br
 Calculate the CVT timings for the given format.
 
@@ -272,6 +274,9 @@ optimized for video: 1000 / 1001 * \fI<fps>\fR.
 .br
 If \fBalt\fR is given and \fI<rb>\fR=3, then the horizontal blanking
 is 160 instead of 80 pixels.
+.br
+If \fBhblank\fR is given and \fI<rb>\fR=3, then the horizontal blanking
+is \fI<hblank>\fR pixels (range of 80-200 and divisible by 8), overriding \fBalt\fR.
 .TP
 \fB\-\-gtf\fR \fBw\fR=\fI<width>\fR,\fBh\fR=\fI<height>\fR[,\fBfps\fR=\fI<fps>\fR][,\fBhorfreq\fR=\fI<horfreq>\fR][,\fBpixclk\fR=\fI<pixclk>\fR]
 [,\fBinterlaced\fR][,\fBoverscan\fR][,\fBsecondary\fR][,\fBC\fR=\fI<c>\fR][,\fBM\fR=\fI<m>\fR][,\fBK\fR=\fI<k>\fR][,\fBJ\fR=\fI<j>\fR]
diff --git a/edid-decode.cpp b/edid-decode.cpp
index e28a3a3..de70242 100644
--- a/edid-decode.cpp
+++ b/edid-decode.cpp
@@ -139,7 +139,7 @@ static void usage(void)
 	       "  --dmt <dmt>           Show the timings for the DMT with the given DMT ID.\n"
 	       "  --vic <vic>           Show the timings for this VIC.\n"
 	       "  --hdmi-vic <hdmivic>  Show the timings for this HDMI VIC.\n"
-	       "  --cvt w=<width>,h=<height>,fps=<fps>[,rb=<rb>][,interlaced][,overscan][,alt]\n"
+	       "  --cvt w=<width>,h=<height>,fps=<fps>[,rb=<rb>][,interlaced][,overscan][,alt][,hblank=<hblank]\n"
 	       "                        Calculate the CVT timings for the given format.\n"
 	       "                        <fps> is frames per second for progressive timings,\n"
 	       "                        or fields per second for interlaced timings.\n"
@@ -151,6 +151,8 @@ static void usage(void)
 	       "                        optimized for video: 1000 / 1001 * <fps>.\n"
 	       "                        If 'alt' is given and <rb>=3, then the horizontal blanking\n"
 	       "                        is 160 instead of 80 pixels.\n"
+	       "                        If 'hblank' is given and <rb>=3, then the horizontal blanking\n"
+	       "                        is <hblank> pixels (range of 80-200), overriding 'alt'.\n"
 	       "  --gtf w=<width>,h=<height>[,fps=<fps>][,horfreq=<horfreq>][,pixclk=<pixclk>][,interlaced]\n"
 	       "        [,overscan][,secondary][,C=<c>][,M=<m>][,K=<k>][,J=<j>]\n"
 	       "                        Calculate the GTF timings for the given format.\n"
@@ -540,12 +542,10 @@ bool edid_state::print_timings(const char *prefix, const struct timings *t,
 	if (rb) {
 		bool alt = t->rb & RB_ALT;
 		s = "RB";
-		// Mark RB_CVT_V3 as preliminary since CVT 1.3 has not been
-		// released yet.
 		if (rb == RB_CVT_V2)
 			s += std::string("v2") + (alt ? ",video-optimized" : "");
 		else if (rb == RB_CVT_V3)
-			s += std::string("v3-is-preliminary") + (alt ? ",h-blank-160" : "");
+			s += std::string("v3") + (alt ? ",h-blank-160" : "");
 	}
 	add_str(s, flags);
 	if (t->hsize_mm || t->vsize_mm)
@@ -1334,6 +1334,7 @@ enum cvt_opts {
 	CVT_OVERSCAN,
 	CVT_RB,
 	CVT_ALT,
+	CVT_RB_H_BLANK,
 };
 
 static int parse_cvt_subopt(char **subopt_str, double *value)
@@ -1349,6 +1350,7 @@ static int parse_cvt_subopt(char **subopt_str, double *value)
 		"overscan",
 		"rb",
 		"alt",
+		"hblank",
 		nullptr
 	};
 
@@ -1377,6 +1379,7 @@ static void parse_cvt(char *optarg)
 	unsigned w = 0, h = 0;
 	double fps = 0;
 	unsigned rb = RB_NONE;
+	unsigned rb_h_blank = 0;
 	bool interlaced = false;
 	bool alt = false;
 	bool overscan = false;
@@ -1409,6 +1412,9 @@ static void parse_cvt(char *optarg)
 		case CVT_ALT:
 			alt = opt_val;
 			break;
+		case CVT_RB_H_BLANK:
+			rb_h_blank = opt_val;
+			break;
 		default:
 			break;
 		}
@@ -1421,7 +1427,7 @@ static void parse_cvt(char *optarg)
 	}
 	if (interlaced)
 		fps /= 2;
-	timings t = state.calc_cvt_mode(w, h, fps, rb, interlaced, overscan, alt);
+	timings t = state.calc_cvt_mode(w, h, fps, rb, interlaced, overscan, alt, rb_h_blank);
 	state.print_timings("", &t, "CVT", "", true, false);
 }
 
diff --git a/edid-decode.h b/edid-decode.h
index 4b73fd4..f3fdfd0 100644
--- a/edid-decode.h
+++ b/edid-decode.h
@@ -313,7 +313,8 @@ struct edid_state {
 	void edid_gtf_mode(unsigned refresh, struct timings &t);
 	timings calc_cvt_mode(unsigned h_pixels, unsigned v_lines,
 			      double ip_freq_rqd, unsigned rb, bool int_rqd = false,
-			      bool margins_rqd = false, bool alt = false);
+			      bool margins_rqd = false, bool alt = false,
+			      unsigned rb_h_blank = 0);
 	void edid_cvt_mode(unsigned refresh, struct timings &t);
 	void detailed_cvt_descriptor(const char *prefix, const unsigned char *x, bool first);
 	void print_standard_timing(const char *prefix, unsigned char b1, unsigned char b2,