philips/mcd212: Darken Black Level (#16262)

-cdi: Improvements to color range: [Vincent Halver]
 * Adjust black level to account for NTSC white-point/black-point range.
 * Perform range clamping after plane mixing rather than to each plane independently.
 * Avoid clobbering VSR field in DCR register.
 * Expand MCD212 color range from 16-240 to 0-255, significantly improving DVC mixing.

Author: Vincent-Halver

src/mame/philips/mcd212.cpp

@@ -250,15 +250,15 @@ void mcd212_device::set_register(uint8_t reg, uint32_t value)
 			if (Path == 0)
 			{
 				LOGMASKED(LOG_REGISTERS, "%s: Scanline %d, Path 0: Weight Factor A = %08x\n", machine().describe_context(), screen().vpos(), value);
-				m_weight_factor[0][0] = (uint8_t)value;
+				m_weight_factor[0][0] = value & 0x3f;
 				update_matte_arrays();
 			}
 			break;
 		case 0xdc: // Weight Factor B
 			if (Path == 1)
 			{
 				LOGMASKED(LOG_REGISTERS, "%s: Scanline %d, Path 1: Weight Factor B = %08x\n", machine().describe_context(), screen().vpos(), value);
-				m_weight_factor[1][0] = (uint8_t)value;
+				m_weight_factor[1][0] = value & 0x3f;
 				update_matte_arrays();
 			}
 			break;
@@ -325,10 +325,10 @@ uint32_t mcd212_device::get_backdrop_plane(int x, int y)
 		uint32_t argb = 0;
 		if (m_ext_video && m_ext_video->ext_video_pixel(x, y, argb))
 			return argb;
-		return s_4bpp_color[0];
+		return s_4bpp_display_color[0];
 	}
 	else
-		return s_4bpp_color[m_backdrop_color];
+		return s_4bpp_display_color[m_backdrop_color];
 }
 
 void mcd212_device::process_ica()
@@ -659,6 +659,12 @@ const uint32_t mcd212_device::s_4bpp_color[16] =
 	0xff101010, 0xff1010e6, 0xff10e610, 0xff10e6e6, 0xffe61010, 0xffe610e6, 0xffe6e610, 0xffe6e6e6
 };
 
+const uint32_t mcd212_device::s_4bpp_display_color[16] =
+{
+	0xff000000, 0xff00007b, 0xff007b00, 0xff007b7b, 0xff7b0000, 0xff7b007b, 0xff7b7b00, 0xff7b7b7b,
+	0xff000000, 0xff0000f9, 0xff00f900, 0xff00f9f9, 0xfff90000, 0xfff900f9, 0xfff9f900, 0xfff9f9f9
+};
+
 template <bool MosaicA, bool MosaicB, bool OrderAB>
 void mcd212_device::mix_lines(uint32_t *plane_a, bool *transparent_a, uint32_t *plane_b, bool *transparent_b, uint32_t *out)
 {
@@ -681,10 +687,12 @@ void mcd212_device::mix_lines(uint32_t *plane_a, bool *transparent_a, uint32_t *
 	// If PAL and 'Standard' bit set, insert a 24px border on the left/right
 	if (border_width)
 	{
-		std::fill_n(out, border_width, s_4bpp_color[0]);
+		std::fill_n(out, border_width, s_4bpp_display_color[0]);
 		out += border_width;
 	}
 
+	const uint32_t *limit = m_dyuv_limit_lut + 0x100;
+
 	for (int x = 0; x < width; x++)
 	{
 		if (transparent_a[x] && transparent_b[x])
@@ -697,20 +705,20 @@ void mcd212_device::mix_lines(uint32_t *plane_a, bool *transparent_a, uint32_t *
 
 		if (transparent_a[x])
 		{
-			plane_a_cur = 0;
+			plane_a_cur = s_4bpp_color[0];
 		}
 		else if (OrderAB && (m_transparency_control & TCR_DISABLE_MX))
 		{
-			plane_b_cur = 0;
+			plane_b_cur = s_4bpp_color[0];
 		}
 
 		if (transparent_b[x])
 		{
-			plane_b_cur = 0;
+			plane_b_cur = s_4bpp_color[0];
 		}
 		else if (!OrderAB && (m_transparency_control & TCR_DISABLE_MX))
 		{
-			plane_a_cur = 0;
+			plane_a_cur = s_4bpp_color[0];
 		}
 
 		const int32_t plane_a_r = 0xff & (plane_a_cur >> 16);
@@ -720,23 +728,27 @@ void mcd212_device::mix_lines(uint32_t *plane_a, bool *transparent_a, uint32_t *
 		const int32_t plane_b_g = 0xff & (plane_b_cur >> 8);
 		const int32_t plane_b_b = 0xff & plane_b_cur;
 
-		const int32_t weighted_a_r = std::clamp((std::clamp(plane_a_r - 16, 0, 255) * weight_a[x]) >> 6, 0, 255);
-		const int32_t weighted_a_g = std::clamp((std::clamp(plane_a_g - 16, 0, 255) * weight_a[x]) >> 6, 0, 255);
-		const int32_t weighted_a_b = std::clamp((std::clamp(plane_a_b - 16, 0, 255) * weight_a[x]) >> 6, 0, 255);
+		const int32_t weighted_a_r = ((plane_a_r - 16) * weight_a[x]) >> 6;
+		const int32_t weighted_a_g = ((plane_a_g - 16) * weight_a[x]) >> 6;
+		const int32_t weighted_a_b = ((plane_a_b - 16) * weight_a[x]) >> 6;
+
+		const int32_t weighted_b_r = ((plane_b_r - 16) * weight_b[x]) >> 6;
+		const int32_t weighted_b_g = ((plane_b_g - 16) * weight_b[x]) >> 6;
+		const int32_t weighted_b_b = ((plane_b_b - 16) * weight_b[x]) >> 6;
 
-		const int32_t weighted_b_r = std::clamp((std::clamp(plane_b_r - 16, 0, 255) * weight_b[x]) >> 6, 0, 255);
-		const int32_t weighted_b_g = std::clamp((std::clamp(plane_b_g - 16, 0, 255) * weight_b[x]) >> 6, 0, 255);
-		const int32_t weighted_b_b = std::clamp((std::clamp(plane_b_b - 16, 0, 255) * weight_b[x]) >> 6, 0, 255);
+		const uint32_t mixed_r = limit[weighted_a_r + weighted_b_r + 16];
+		const uint32_t mixed_g = limit[weighted_a_g + weighted_b_g + 16];
+		const uint32_t mixed_b = limit[weighted_a_b + weighted_b_b + 16];
 
-		const uint8_t out_r = std::clamp(weighted_a_r + weighted_b_r + 16, 0, 255);
-		const uint8_t out_g = std::clamp(weighted_a_g + weighted_b_g + 16, 0, 255);
-		const uint8_t out_b = std::clamp(weighted_a_b + weighted_b_b + 16, 0, 255);
+		const uint32_t out_r = limit[((int32_t(mixed_r) - 16) * 298 + 128) >> 8];
+		const uint32_t out_g = limit[((int32_t(mixed_g) - 16) * 298 + 128) >> 8];
+		const uint32_t out_b = limit[((int32_t(mixed_b) - 16) * 298 + 128) >> 8];
 		out[x] = 0xff000000 | (out_r << 16) | (out_g << 8) | out_b;
 	}
 
 	if (border_width)
 	{
-		std::fill_n(&out[width], border_width, s_4bpp_color[0]);
+		std::fill_n(&out[width], border_width, s_4bpp_display_color[0]);
 	}
 }
 
@@ -762,7 +774,7 @@ void mcd212_device::draw_cursor(uint32_t *scanline)
 
 	if ((0 <= y) && (y < 16))
 	{
-		const uint32_t color = s_4bpp_color[color_index];
+		const uint32_t color = s_4bpp_display_color[color_index];
 		const uint8_t resolution = (m_cursor_control & CURCNT_CUW) ? 1 : 2;
 		for (int x = 0; x < 16; x++)
 		{
@@ -817,6 +829,7 @@ uint16_t mcd212_device::dcr1_r(offs_t offset, uint16_t mem_mask)
 void mcd212_device::dcr1_w(offs_t offset, uint16_t data, uint16_t mem_mask)
 {
 	LOGMASKED(LOG_MAIN_REG_WRITES, "%s: Display Command Register 1 Write: %04x & %08x\n", machine().describe_context(), data, mem_mask);
+	mem_mask &= 0xff00;
 	COMBINE_DATA(&m_dcr[0]);
 	update_frame_geometry(false);
 }
@@ -909,6 +922,7 @@ uint16_t mcd212_device::dcr2_r(offs_t offset, uint16_t mem_mask)
 void mcd212_device::dcr2_w(offs_t offset, uint16_t data, uint16_t mem_mask)
 {
 	LOGMASKED(LOG_MAIN_REG_WRITES, "%s: Display Command Register 2 Write: %04x & %08x\n", machine().describe_context(), data, mem_mask);
+	mem_mask &= 0xff00;
 	COMBINE_DATA(&m_dcr[1]);
 }
 
@@ -1022,7 +1036,7 @@ uint32_t mcd212_device::screen_update(screen_device &screen, bitmap_rgb32 &bitma
 			// If PAL and 'Standard' bit set, insert a 20-line border on the top/bottom
 			if ((scanline - m_ica_height < 20) || (scanline >= (m_total_height - 20)))
 			{
-				std::fill_n(out, 768, s_4bpp_color[0]);
+				std::fill_n(out, 768, s_4bpp_display_color[0]);
 				draw_line = false;
 			}
 		}

src/mame/philips/mcd212.h

@@ -268,6 +268,7 @@ class mcd212_device : public device_t,
 	bool m_blink_active = false;
 
 	static const uint32_t s_4bpp_color[16];
+	static const uint32_t s_4bpp_display_color[16];
 
 	uint8_t get_weight_factor(const uint32_t Matte_idx);
 	uint8_t get_matte_op(const uint32_t Matte_idx);