66 lines
1.4 KiB
GLSL
66 lines
1.4 KiB
GLSL
/*
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Linear vs Logarithmic FFT
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some good test songs:
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https://soundcloud.com/kraddy/winning
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https://soundcloud.com/grey-houston/soothing-piano-melody
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https://soundcloud.com/pointpoint/life-in-gr
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*/
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//from https://stackoverflow.com/questions/35799286
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float toLog(float value, float min, float max){
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float exp = (value-min) / (max-min);
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return min * pow(max/min, exp);
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}
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float getLevel(float samplePos){
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// the sound texture is 512x2
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int tx = int(samplePos*512.0);
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// first row is frequency data (48Khz/4 in 512 texels, meaning 23 Hz per texel)
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return texelFetch( iChannel0, ivec2(tx,0), 0 ).x;
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}
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void mainImage( out vec4 fragColor, in vec2 fragCoord )
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{
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vec2 uv = fragCoord.xy / iResolution.xy;
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float xPos;
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float fft;
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if (uv.y > 0.5){
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//linear sampling
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xPos = uv.x;
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fft = getLevel(xPos);
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}else{
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//crop bottom and top of range
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uv.x = mix(0.3,0.7, uv.x);
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//logarithmic sampling
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xPos = toLog(uv.x, 0.01, 1.0);
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fft = getLevel(xPos);
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//boost contrast
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fft = pow(fft,3.0);
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//boost gain
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fft *= 1.5;
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//contrast / brightness
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float contrast = 1.4;
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float brightness = 0.;
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fft = (fft - 0.5) * contrast + 0.5 + brightness;
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}
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fragColor = vec4(vec3(fft),1.0);
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}
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