CD-i: Add Interlace Graphics (#13997)

* CD-i: Doubles Vertical Resolution

Minimal code to double the vertical resolution for #13231 . The result is a slightly crisper looking image on most monitors due to better upscaling on images are have less oblique pixels.

This was tested minimally and seems stable.

Something closer to a proper interlaced image can be accomplished using the _PA bit, however current screen blanks between frames preventing the parity bit from being able to produce a correct interlace image yet.

* CD-i: Remove excess vertical resolution

* Use 2x clock multiplier

* CD-i: Add Interlaced Graphics

Fixes #13231

* CD-i: Toggle Interlace Effect

When the interlace bit is off, line-duplication is re-enabled. This ensures the interlace effect is only visible when the game declares the output to be interlaced.

* CD-i: Fix interlaced line offset

In some cases, such as during startup, the line length of the interlaced line is impacted. This corrects the offset.

* CD-i: Fix Interlace Clock Speed

Author: Vincent-Halver

src/mame/philips/cdi.cpp

@@ -434,7 +434,7 @@ void cdi_state::cdimono1_base(machine_config &config)
 	m_mcd212->int_callback().set(m_maincpu, FUNC(scc68070_device::int1_w));
 
 	screen_device &screen(SCREEN(config, "screen", SCREEN_TYPE_RASTER));
-	screen.set_raw(14976000, 960, 0, 768, 312, 32, 312);
+	screen.set_raw(960*(312*2-32)*50, 960, 0, 768, 312*2-32, 32, 312*2-32);
 	screen.set_video_attributes(VIDEO_UPDATE_SCANLINE);
 	screen.set_screen_update(m_mcd212, FUNC(mcd212_device::screen_update));
 

src/mame/philips/mcd212.cpp

@@ -6,7 +6,7 @@
     CD-i MCD212 Video Decoder and System Controller emulation
     -------------------
 
-    written by Ryan Holtz
+    written by Ryan Holtz, Vincent.Halver
 
 
 *******************************************************************************
@@ -330,13 +330,13 @@ template <int Path>
 void mcd212_device::process_ica()
 {
 	uint16_t *ica = Path ? m_planeb.target() : m_planea.target();
-	uint32_t addr = 0x200;
-	uint32_t cmd = 0;
-
 	const int max_to_process = m_ica_height * 120;
+	// LCT depends on the current frame parity
+	uint32_t addr = (BIT(m_csrr[0], CSR1R_PA_BIT) == 0) ? 0x200 : 0x202;
+	
 	for (int i = 0; i < max_to_process; i++)
 	{
-		cmd = ica[addr++] << 16;
+		uint32_t cmd = ica[addr++] << 16;
 		cmd |= ica[addr++];
 		switch ((cmd & 0xff000000) >> 24)
 		{
@@ -666,6 +666,11 @@ void mcd212_device::mix_lines(uint32_t *plane_a, bool *transparent_a, uint32_t *
 	if (icmB == ICM_CLUT4)
 		mosaic_count_b >>= 1;
 
+	// If PAL and 'Standard' bit set, insert a 24px border on the left/right
+	uint32_t offset = (!BIT(m_dcr[0], DCR_CF_BIT) || BIT(m_csrw[0], CSR1W_ST_BIT)) ? 24 : 0;
+	std::fill_n(out, offset, s_4bpp_color[0]);
+	out += offset;
+
 	for (int x = 0; x < width; x++)
 	{
 		if (transparent_a[x] && transparent_b[x])
@@ -963,12 +968,19 @@ uint32_t mcd212_device::screen_update(screen_device &screen, bitmap_rgb32 &bitma
 	bool transparent_a[768];
 	bool transparent_b[768];
 
-	int scanline = screen.vpos();
+	if (screen.vpos() >= m_total_height)
+	{
+		return 0; // Do nothing on the extended rows.
+	}
 
+	int scanline = screen.vpos();
+	
 	// Process VSR and mix if we're in the visible region
 	if (scanline >= m_ica_height)
 	{
-		uint32_t *out = &bitmap.pix(scanline);
+		uint32_t bitmap_line = ((scanline - m_ica_height) << 1) + m_ica_height;
+		uint32_t *out = &bitmap.pix(bitmap_line + (!BIT(m_csrr[0], CSR1R_PA_BIT)));
+		uint32_t* out2 = &bitmap.pix(bitmap_line + (BIT(m_csrr[0], CSR1R_PA_BIT)));
 
 		bool draw_line = true;
 		if (!BIT(m_dcr[0], DCR_FD_BIT) && BIT(m_csrw[0], CSR1W_ST_BIT))
@@ -985,12 +997,6 @@ uint32_t mcd212_device::screen_update(screen_device &screen, bitmap_rgb32 &bitma
 
 		if (draw_line)
 		{
-			// If PAL and 'Standard' bit set, insert a 24px border on the left/right
-			if (!BIT(m_dcr[0], DCR_CF_BIT) || BIT(m_csrw[0], CSR1W_ST_BIT))
-			{
-				std::fill_n(out, 24, s_4bpp_color[0]);
-				out += 24;
-			}
 
 			process_vsr<0>(plane_a, transparent_a);
 			process_vsr<1>(plane_b, transparent_b);
@@ -1028,6 +1034,16 @@ uint32_t mcd212_device::screen_update(screen_device &screen, bitmap_rgb32 &bitma
 
 			draw_cursor(out);
 		}
+
+		if (BIT(m_dcr[0], DCR_SM_BIT)) {
+			// Interlace Output
+			memcpy(out2, m_interlace_field[scanline], 768 * sizeof(uint32_t));
+			memcpy(m_interlace_field[scanline], out, 768 * sizeof(uint32_t));
+		}
+		else {
+			// Single Field Output (duplicate lines)
+			memcpy(out2, out, 768 * sizeof(uint32_t));
+		}
 	}
 
 	// Toggle frame parity at the end of the visible frame (even in non-interlaced mode).
@@ -1118,6 +1134,9 @@ void mcd212_device::device_reset()
 	m_ica_height = 32;
 	m_total_height = 312;
 	m_blink_time = 0;
+	for (int i = 0; i < 312; i++) {
+		std::fill_n(m_interlace_field[i], 768, 0);
+	}
 
 	m_int_callback(CLEAR_LINE);
 
@@ -1197,6 +1216,8 @@ void mcd212_device::device_start()
 	save_item(NAME(m_blink_time));
 	save_item(NAME(m_blink_active));
 
+	save_item(NAME(m_interlace_field));
+
 	m_dca_timer = timer_alloc(FUNC(mcd212_device::dca_tick), this);
 	m_dca_timer->adjust(attotime::never);
 

src/mame/philips/mcd212.h

@@ -139,6 +139,7 @@ class mcd212_device : public device_t,
 		MC_OP_SHIFT          = 20,
 
 		CSR1R_PA             = 0x20,        // Parity
+		CSR1R_PA_BIT         = 5,
 		CSR1R_DA             = 0x80,        // Display Active
 
 		CSR1W_BE             = 0x0001,      // Bus Error
@@ -231,6 +232,8 @@ class mcd212_device : public device_t,
 	required_shared_ptr<uint16_t> m_planea;
 	required_shared_ptr<uint16_t> m_planeb;
 
+	uint32_t m_interlace_field[312][768];
+
 	// internal state
 	bool m_matte_flag[2][768]{};
 	int m_ica_height = 0;