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https://github.com/italicsjenga/slang-shaders.git
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212 lines
6.8 KiB
Plaintext
212 lines
6.8 KiB
Plaintext
#version 450
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/*
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pal-singlepass.slang
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svo's PAL single pass shader, ported to libretro
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------------------------------------------------
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"Software composite video modulation/demodulation experiments
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The idea is to reproduce in GLSL shaders realistic composite-like
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artifacting by applying PAL modulation and demodulation.
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Digital texture, passed through the model of an analog channel,
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should suffer same effects as its analog counterpart and exhibit properties,
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such as dot crawl and colour bleeding, that may be desirable for faithful
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reproduction of look and feel of old computer games."
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https://github.com/svofski/CRT
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Copyright (c) 2016, Viacheslav Slavinsky
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED.
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IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
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DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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layout(push_constant) uniform Push
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{
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float FIR_GAIN;
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float FIR_INVGAIN;
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float PHASE_NOISE;
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} param;
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#pragma parameter FIR_GAIN "FIR lowpass gain" 1.5 0.0 5.0 0.1
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#pragma parameter FIR_INVGAIN "Inverse gain for luma recovery" 1.1 0.0 5.0 0.1
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#pragma parameter PHASE_NOISE "Phase noise" 1.0 0.0 5.0 0.1
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layout(std140, set = 0, binding = 0) uniform UBO
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{
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mat4 MVP;
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vec4 OutputSize;
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vec4 OriginalSize;
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vec4 SourceSize;
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uint FrameCount;
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} global;
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#pragma stage vertex
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layout(location = 0) in vec4 Position;
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layout(location = 1) in vec2 TexCoord;
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layout(location = 0) out vec2 vTexCoord;
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void main()
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{
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gl_Position = global.MVP * Position;
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vTexCoord = TexCoord;
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}
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#pragma stage fragment
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layout(location = 0) in vec2 vTexCoord;
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layout(location = 0) out vec4 FragColor;
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layout(set = 0, binding = 2) uniform sampler2D Source;
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/* Subcarrier frequency */
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#define FSC 4433618.75
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/* Line frequency */
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#define FLINE 15625
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#define VISIBLELINES 312
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#define PI 3.14159265358
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#define RGB_to_YIQ mat3x3( 0.299, 0.595716, 0.211456,\
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0.587, -0.274453, -0.522591,\
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0.114, -0.321263, 0.311135)
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#define YIQ_to_RGB mat3x3( 1.0 , 1.0, 1.0,\
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0.9563, -0.2721, -1.1070,\
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0.6210, -0.6474, 1.7046)
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#define RGB_to_YUV mat3x3( 0.299, -0.14713, 0.615,\
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0.587, -0.28886, -0.514991,\
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0.114, 0.436, -0.10001)
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#define YUV_to_RGB mat3x3( 1.0, 1.0, 1.0,\
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0.0, -0.39465, 2.03211,\
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1.13983, -0.58060, 0.0)
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#define fetch(ofs,center,invx) texture(Source, vec2((ofs) * (invx) + center.x, center.y))
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#define FIRTAPS 20
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float FIR[FIRTAPS] = float[FIRTAPS] (
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-0.008030271,
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0.003107906,
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0.016841352,
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0.032545161,
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0.049360136,
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0.066256720,
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0.082120150,
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0.095848433,
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0.106453014,
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0.113151423,
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0.115441842,
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0.113151423,
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0.106453014,
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0.095848433,
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0.082120150,
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0.066256720,
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0.049360136,
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0.032545161,
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0.016841352,
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0.003107906
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);
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/* subcarrier counts per scan line = FSC/FLINE = 283.7516 */
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/* We save the reciprocal of this only to optimize it */
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float counts_per_scanline_reciprocal = 1.0 / (FSC/FLINE);
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float width_ratio;
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float height_ratio;
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float altv;
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float invx;
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/* http://byteblacksmith.com/improvements-to-the-canonical-one-liner-glsl-rand-for-opengl-es-2-0/ */
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float rand(vec2 co)
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{
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float a = 12.9898;
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float b = 78.233;
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float c = 43758.5453;
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float dt = dot(co.xy, vec2(a, b));
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float sn = mod(dt,3.14);
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return fract(sin(sn) * c);
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}
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float modulated(vec2 xy, float sinwt, float coswt)
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{
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vec3 rgb = fetch(0, xy, invx).xyz;
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vec3 yuv = RGB_to_YUV * rgb;
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return clamp(yuv.x + yuv.y * sinwt + yuv.z * coswt, 0.0, 1.0);
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}
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vec2 modem_uv(vec2 xy, float ofs) {
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float t = (xy.x + ofs * invx) * global.SourceSize.x;
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float wt = t * 2 * PI / width_ratio;
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float sinwt = sin(wt);
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float coswt = cos(wt + altv);
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vec3 rgb = fetch(ofs, xy, invx).xyz;
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vec3 yuv = RGB_to_YUV * rgb;
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float signal = clamp(yuv.x + yuv.y * sinwt + yuv.z * coswt, 0.0, 1.0);
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if (param.PHASE_NOISE != 0)
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{
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/* .yy is horizontal noise, .xx looks bad, .xy is classic noise */
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vec2 seed = xy.yy * global.FrameCount;
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wt = wt + param.PHASE_NOISE * (rand(seed) - 0.5);
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sinwt = sin(wt);
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coswt = cos(wt + altv);
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}
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return vec2(signal * sinwt, signal * coswt);
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}
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void main()
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{
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vec2 xy = vTexCoord;
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width_ratio = global.SourceSize.x * (counts_per_scanline_reciprocal);
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height_ratio = global.SourceSize.y / VISIBLELINES;
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altv = mod(floor(xy.y * VISIBLELINES + 0.5), 2.0) * PI;
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invx = 0.25 * (counts_per_scanline_reciprocal); // equals 4 samples per Fsc period
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// lowpass U/V at baseband
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vec2 filtered = vec2(0.0, 0.0);
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for (int i = 0; i < FIRTAPS; i++) {
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vec2 uv = modem_uv(xy, i - FIRTAPS*0.5);
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filtered += param.FIR_GAIN * uv * FIR[i];
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}
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float t = xy.x * global.SourceSize.x;
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float wt = t * 2 * PI / width_ratio;
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float sinwt = sin(wt);
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float coswt = cos(wt + altv);
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float luma = modulated(xy, sinwt, coswt) - param.FIR_INVGAIN * (filtered.x * sinwt + filtered.y * coswt);
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vec3 yuv_result = vec3(luma, filtered.x, filtered.y);
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FragColor = vec4(YUV_to_RGB * yuv_result, 1.0);
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}
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