gta 5 radio effect

#ifdef GL_ES
    precision mediump float;
#endif

float normpdf(in float x, in float sigma)
{
    return 0.39894*exp(-0.5*x*x/(sigma*sigma))/sigma;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 uv = fragCoord/iResolution.xy;
    // GAUSSIAN BLUR PASS
    //vec4 color = texture(iChannel0, uv).rgba;

    const int mSize = 32;
    const int kSize = (mSize-1)/2;
    float kernel[mSize];
    vec3 final_colour = vec3(0.0);

    //create the 1-D kernel
    float sigma = 4.0;
    float Z = 0.0;
    for (int j = 0; j <= kSize; ++j)
    {
        kernel[kSize+j] = kernel[kSize-j] = normpdf(float(j), sigma);
    }

    //get the normalization factor (as the gaussian has been clamped)
    for (int j = 0; j < mSize; ++j)
    {
        Z += kernel[j];
    }

    //read out the texels
    for (int i=-kSize; i <= kSize; ++i)
    {
        for (int j=-kSize; j <= kSize; ++j)
        {
            final_colour += kernel[kSize+j]*kernel[kSize+i]*texture(iChannel0, (fragCoord.xy+vec2(float(i),float(j))) / iResolution.xy).rgb;
        }
    }

    fragColor = vec4(final_colour/(Z*Z), 1.0);

    // GREEN COLOR PASS
    fragColor *= vec4(1, 1.20, 1, 1);

    // VIGNETTE PASS
    vec2 coord = (uv - 0.5) * (iResolution.x/iResolution.y) * 2.0;
    float rf = sqrt(dot(coord, coord)) * 0.3;
    float rf2_1 = rf * rf + 1.0;
    float e = 1.0 / (rf2_1 * rf2_1);

    vec4 src = vec4(1.0,1.0,1.0,1.0);
    fragColor = vec4(fragColor.rgb * e, 1.0);
}