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crt_nesrgb.h
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crt_nesrgb.h
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/*****************************************************************************/
/*
* NTSC/CRT - integer-only NTSC video signal encoding / decoding emulation
*
* by EMMIR 2018-2023
* modifications for Mesen by Persune
* https://github.com/LMP88959/NTSC-CRT
*
* YouTube: https://www.youtube.com/@EMMIR_KC/videos
* Discord: https://discord.com/invite/hdYctSmyQJ
*/
/*****************************************************************************/
#ifndef _CRT_NESRGB_H_
#define _CRT_NESRGB_H_
#ifdef __cplusplus
extern "C" {
#endif
/* crt_nesrgb.h
*
* An interface to convert NES PPU output in RGB form to an analog NTSC signal.
*
*/
/* 0 = vertical chroma (228 chroma clocks per line) */
/* 1 = checkered chroma (227.5 chroma clocks per line) */
/* 2 = sawtooth chroma (227.3 chroma clocks per line) */
#define CRT_CHROMA_PATTERN 2
/* chroma clocks (subcarrier cycles) per line */
#if (CRT_CHROMA_PATTERN == 1)
#define CRT_CC_LINE 2275
#elif (CRT_CHROMA_PATTERN == 2)
#define CRT_CC_LINE 2273
#else
/* this will give the 'rainbow' effect in the famous waterfall scene */
#define CRT_CC_LINE 2280
#endif
/* NOTE, in general, increasing CRT_CB_FREQ reduces blur and bleed */
#define CRT_CB_FREQ 4 /* carrier frequency relative to sample rate */
/* https://www.nesdev.org/wiki/NTSC_video#Scanline_Timing */
#define CRT_HRES (CRT_CC_LINE * CRT_CB_FREQ / 10) /* horizontal res */
#define CRT_VRES 262 /* vertical resolution */
#define CRT_INPUT_SIZE (CRT_HRES * CRT_VRES)
#define CRT_TOP 15 /* first line with active video */
#define CRT_BOT 255 /* final line with active video */
#define CRT_LINES (CRT_BOT - CRT_TOP) /* number of active video lines */
#define CRT_CC_SAMPLES 4 /* samples per chroma period (samples per 360 deg) */
#define CRT_CC_VPER 3 /* vertical period in which the artifacts repeat */
/* search windows, in samples */
#define CRT_HSYNC_WINDOW 6
#define CRT_VSYNC_WINDOW 6
/* accumulated signal threshold required for sync detection.
* Larger = more stable, until it's so large that it is never reached in which
* case the CRT won't be able to sync
*/
#define CRT_HSYNC_THRESH 4
#define CRT_VSYNC_THRESH 94
/* NES composite signal is measured in terms of PPU pixels, or cycles
* https://www.nesdev.org/wiki/NTSC_video#Scanline_Timing
*
* FULL HORIZONTAL LINE SIGNAL
* (341 PPU px; one cycle skipped on odd rendered frames)
* |---------------------------------------------------------------------------|
* HBLANK (58 PPU px) ACTIVE VIDEO (283 PPU px)
* |-------------------||------------------------------------------------------|
*
*
* WITHIN HBLANK PERIOD:
*
* FP (9 PPU px) SYNC (25 PPU px) BW (4 PPU px) CB (15 PPU px) BP (5 PPU px)
* |--------------||---------------||------------||-------------||-------------|
* BLANK SYNC BLANK BLANK BLANK
*
*
* WITHIN ACTIVE VIDEO PERIOD:
*
* LB (15 PPU px) AV (256 PPU px) RB (11 PPU px)
* |--------------||--------------------------------------------||-------------|
* BORDER VIDEO BORDER
*
*/
#define LINE_BEG 0
#define FP_PPUpx 9 /* front porch */
#define SYNC_PPUpx 25 /* sync tip */
#define BW_PPUpx 4 /* breezeway */
#define CB_PPUpx 15 /* color burst */
#define BP_PPUpx 5 /* back porch */
#define PS_PPUpx 1 /* pulse */
#define LB_PPUpx 15 /* left border */
#define AV_PPUpx 256 /* active video */
#define RB_PPUpx 11 /* right border */
#define HB_PPUpx (FP_PPUpx + SYNC_PPUpx + BW_PPUpx + CB_PPUpx + BP_PPUpx) /* h blank */
/* line duration should be ~63500 ns */
#define LINE_PPUpx (FP_PPUpx + SYNC_PPUpx + BW_PPUpx + CB_PPUpx + BP_PPUpx + PS_PPUpx + LB_PPUpx + AV_PPUpx + RB_PPUpx)
/* convert pixel offset to its corresponding point on the sampled line */
#define PPUpx2pos(PPUpx) ((PPUpx) * CRT_HRES / LINE_PPUpx)
/* starting points for all the different pulses */
#define FP_BEG PPUpx2pos(0) /* front porch point */
#define SYNC_BEG PPUpx2pos(FP_PPUpx) /* sync tip point */
#define BW_BEG PPUpx2pos(FP_PPUpx + SYNC_PPUpx) /* breezeway point */
#define CB_BEG PPUpx2pos(FP_PPUpx + SYNC_PPUpx + BW_PPUpx) /* color burst point */
#define BP_BEG PPUpx2pos(FP_PPUpx + SYNC_PPUpx + BW_PPUpx + CB_PPUpx) /* back porch point */
#define LAV_BEG PPUpx2pos(HB_PPUpx) /* full active video point */
#define AV_BEG PPUpx2pos(HB_PPUpx + PS_PPUpx + LB_PPUpx) /* PPU active video point */
#define AV_LEN PPUpx2pos(AV_PPUpx) /* active video length */
/* somewhere between 7 and 12 cycles */
#define CB_CYCLES 10
/* line frequency */
#define L_FREQ 1431818 /* full line */
/* IRE units (100 = 1.0V, -40 = 0.0V) */
/* https://www.nesdev.org/wiki/NTSC_video#Terminated_measurement */
#define WHITE_LEVEL 100
#define BURST_LEVEL 30
#define BLACK_LEVEL 0
#define BLANK_LEVEL 0
#define SYNC_LEVEL -37
struct NTSC_SETTINGS {
const unsigned char *data; /* image data */
int format; /* pix format (one of the CRT_PIX_FORMATs in crt_core.h) */
int w, h; /* width and height of image */
int dot_crawl_offset; /* 0, 1, or 2 */
/* NOTE: NES mode is always progressive */
int hue; /* 0-359 */
int xoffset; /* x offset in sample space. 0 is minimum value */
int yoffset; /* y offset in # of lines. 0 is minimum value */
/* make sure your NTSC_SETTINGS struct is zeroed out before you do anything */
int field_initialized; /* internal state */
};
#ifdef __cplusplus
}
#endif
#endif