diff --git a/crt_core.c b/crt_core.c
index eda68b6..8295b1c 100644
--- a/crt_core.c
+++ b/crt_core.c
@@ -66,6 +66,9 @@ crt_sincos14(int *s, int *c, int n)
 
 /* convolution is much faster but the EQ looks softer, more authentic, and more analog */
 #define USE_CONVOLUTION 0
+#define USE_7_SAMPLE_KERNEL 0
+#define USE_6_SAMPLE_KERNEL 0
+#define USE_5_SAMPLE_KERNEL 1
 
 #if USE_CONVOLUTION
 
@@ -101,9 +104,23 @@ eqf(struct EQF *f, int s)
         h[i] = h[i - 1];
     }
     h[0] = s;
+#if USE_7_SAMPLE
+    /* index : 0 1 2 3 4 5 6 */
+    /* weight: 1 4 7 8 7 4 1 */
+    return (s + h[6] + ((h[1] + h[5]) * 4) + ((h[2] + h[4]) * 7) + (h[3] * 8)) >> 5;
+#elseif USE_6_SAMPLE
+    /* index : 0 1 2 3 4 5 */
+    /* weight: 1 3 4 4 3 1 */
+    return (s + h[5] + 3 * (h[1] + h[4]) + 4 * (h[2] + h[3])) >> 4;
+#elseif USE_5_SAMPLE
     /* index : 0 1 2 3 4 */
     /* weight: 1 2 2 2 1 */
     return (s + h[4] + ((h[1] + h[2] + h[3]) << 1)) >> 3;
+#else
+    /* index : 0 1 2 3 */
+    /* weight: 1 1 1 1*/
+    return (s + h[3] + h[1] + h[2]) >> 2;
+#endif
 }
 
 #else
diff --git a/crt_nes.c b/crt_nes.c
index 8b90130..fd9c689 100644
--- a/crt_nes.c
+++ b/crt_nes.c
@@ -17,6 +17,62 @@
 #include <stdlib.h>
 #include <string.h>
 
+// Precalculate the low and high signal chosen for each 64 base colors
+// with their respective attenuated values
+// https://www.nesdev.org/wiki/NTSC_video#Brightness_Levels
+const int8_t IRE_levels[2][2][0x40]{
+   // waveform low
+   {
+      // normal
+      {
+         // 0x
+         43, -12, -12, -12, -12, -12, -12, -12, -12, -12, -12, -12, -12, -12, 0, 0,
+         // 1x
+         74, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+         // 2x
+         110, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 0, 0,
+         // 3x
+         110, 80, 80, 80, 80, 80, 80, 80, 80, 80, 80, 80, 80, 80, 0, 0
+      },
+      // attenuated
+      {
+         // 0x
+         26 , -17, -17, -17, -17, -17, -17, -17, -17, -17, -17, -17, -17, -17, 0, 0,
+         // 1x
+         51, -8, -8, -8, -8, -8, -8, -8, -8, -8, -8, -8, -8, -8, 0, 0,
+         // 2x
+         82, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 0, 0,
+         // 3x
+         82, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 0, 0
+      }
+   },
+   // waveform high
+   {
+      // normal
+      {
+         // 0x
+         43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, -12, 0, 0,
+         // 1x
+         74, 74, 74, 74, 74, 74, 74, 74, 74, 74, 74, 74, 74, 0, 0, 0,
+         // 2x
+         110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 34, 0, 0,
+         // 3x
+         110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 110, 80, 0, 0
+         },
+      // attenuated
+      {
+         // 0x
+         26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, -17, 0, 0,
+         // 1x
+         51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, -8, 0, 0,
+         // 2x
+         82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 19, 0, 0,
+         // 3x
+         82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 82, 56, 0, 0
+      }
+   }
+};
+
 /* generate the square wave for a given 9-bit pixel and phase */
 static int
 square_sample(int p, int phase)
@@ -26,38 +82,17 @@ square_sample(int p, int phase)
         0500, 0400,
         0600, 0200
     };
-    int bri, hue, v;
+    int hue;
+    bool e, v;
 
     hue = (p & 0x0f);
-    
-    /* last two columns are black */
-    if (hue >= 0x0e) {
-        return 0;
-    }
 
-    bri = ((p & 0x30) >> 4) * 300;
-    
-    switch (hue) {
-        case 0:
-            v = bri + 410;
-            break;
-        case 0x0d:
-            v = bri - 300;
-            break;
-        default:
-            v = (((hue + phase) % 12) < 6) ? (bri + 410) : (bri - 300);
-            break;
-    }
+    v = (((hue + phase) % 12) < 6);
 
-    if (v > 1024) {
-        v = 1024;
-    }
     /* red 0100, green 0200, blue 0400 */
-    if ((p & 0700) & active[(phase >> 1) % 6]) {
-        return (v >> 1) + (v >> 2);
-    }
+    e = ((p & 0700) & active[(phase >> 1) % 6]);
 
-    return v;
+    return IRE_levels[v][e][p & 0x3F];
 }
 
 #define NES_OPTIMIZED 0