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crt_ntscvhs.h
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crt_ntscvhs.h
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/*****************************************************************************/
/*
* NTSC/CRT - integer-only NTSC video signal encoding / decoding emulation
*
* by EMMIR 2018-2023
*
* YouTube: https://www.youtube.com/@EMMIR_KC/videos
* Discord: https://discord.com/invite/hdYctSmyQJ
*/
/*****************************************************************************/
#ifndef _CRT_NTSC_VHS_H_
#define _CRT_NTSC_VHS_H_
#ifdef __cplusplus
extern "C" {
#endif
/* crt_ntscvhs.h
*
* An interface to convert a digital image to an analog NTSC signal with VHS
* quality and some optional signal aberration at the bottom.
*
*/
/* 0 = vertical chroma (228 chroma clocks per line) */
/* 1 = checkered chroma (227.5 chroma clocks per line) */
#define CRT_CHROMA_PATTERN 1
/* set to zero to remove the noise at the bottom of the frame */
#define CRT_VHS_NOISE 1
/* chroma clocks (subcarrier cycles) per line */
#if (CRT_CHROMA_PATTERN == 1)
#define CRT_CC_LINE 2275
#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 */
#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 21 /* first line with active video */
#define CRT_BOT 261 /* 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 1 /* vertical period in which the artifacts repeat */
/* search windows, in samples */
#define CRT_HSYNC_WINDOW 8
#define CRT_VSYNC_WINDOW 8
/* 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
/*
* FULL HORIZONTAL LINE SIGNAL (~63500 ns)
* |---------------------------------------------------------------------------|
* HBLANK (~10900 ns) ACTIVE VIDEO (~52600 ns)
* |-------------------||------------------------------------------------------|
*
*
* WITHIN HBLANK PERIOD:
*
* FP (~1500 ns) SYNC (~4700 ns) BW (~600 ns) CB (~2500 ns) BP (~1600 ns)
* |--------------||---------------||------------||-------------||-------------|
* BLANK SYNC BLANK BLANK BLANK
*
*/
#define LINE_BEG 0
#define FP_ns 1500 /* front porch */
#define SYNC_ns 4700 /* sync tip */
#define BW_ns 600 /* breezeway */
#define CB_ns 2500 /* color burst */
#define BP_ns 1600 /* back porch */
#define AV_ns 52600 /* active video */
#define HB_ns (FP_ns + SYNC_ns + BW_ns + CB_ns + BP_ns) /* h blank */
/* line duration should be ~63500 ns */
#define LINE_ns (FP_ns + SYNC_ns + BW_ns + CB_ns + BP_ns + AV_ns)
/* convert nanosecond offset to its corresponding point on the sampled line */
#define ns2pos(ns) ((ns) * CRT_HRES / LINE_ns)
/* starting points for all the different pulses */
#define FP_BEG ns2pos(0)
#define SYNC_BEG ns2pos(FP_ns)
#define BW_BEG ns2pos(FP_ns + SYNC_ns)
#define CB_BEG ns2pos(FP_ns + SYNC_ns + BW_ns)
#define BP_BEG ns2pos(FP_ns + SYNC_ns + BW_ns + CB_ns)
#define AV_BEG ns2pos(HB_ns)
#define AV_LEN ns2pos(AV_ns)
/* somewhere between 7 and 12 cycles */
#define CB_CYCLES 10
#define VHS_SP 0
#define VHS_LP 1
#define VHS_EP 2
#define VHS_MODE VHS_SP
/* frequencies for bandlimiting */
#if (VHS_MODE == VHS_SP)
#define L_FREQ 1431818 /* full line */
#define Y_FREQ 300000 /* Luma (Y) 3.0 MHz of the 14.31818 MHz */
#define I_FREQ 62700 /* Chroma (I) 627 kHz of the 14.31818 MHz */
#define Q_FREQ 62700 /* Chroma (Q) 627 kHz of the 14.31818 MHz */
#elif (VHS_MODE == VHS_LP)
#define L_FREQ 1431818 /* full line */
#define Y_FREQ 240000 /* Luma (Y) 2.4 MHz of the 14.31818 MHz */
#define I_FREQ 40000 /* Chroma (I) 400 kHz of the 14.31818 MHz */
#define Q_FREQ 40000 /* Chroma (Q) 400 kHz of the 14.31818 MHz */
#elif (VHS_MODE == VHS_EP)
#define L_FREQ 1431818 /* full line */
#define Y_FREQ 200000 /* Luma (Y) 2.0 MHz of the 14.31818 MHz */
#define I_FREQ 37000 /* Chroma (I) 370 kHz of the 14.31818 MHz */
#define Q_FREQ 37000 /* Chroma (Q) 370 kHz of the 14.31818 MHz */
#endif
/* IRE units (100 = 1.0V, -40 = 0.0V) */
#define WHITE_LEVEL 100
#define BURST_LEVEL 20
#define BLACK_LEVEL 7
#define BLANK_LEVEL 0
#define SYNC_LEVEL -40
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 raw; /* 0 = scale image to fit monitor, 1 = don't scale */
int as_color; /* 0 = monochrome, 1 = full color */
int field; /* 0 = even, 1 = odd */
int frame; /* 0 = even, 1 = odd */
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 */
int do_aberration; /* 0 = no aberration, 1 = with aberration */
/* make sure your NTSC_SETTINGS struct is zeroed out before you do anything */
int iirs_initialized; /* internal state */
};
#ifdef __cplusplus
}
#endif
#endif