Working on processors a tiny bit

src/lib/audio/processors/HighPassSweepDown.ts

@@ -0,0 +1,65 @@
+import type { AudioProcessor, ProcessorCategory } from './AudioProcessor';
+
+export class HighPassSweepDown implements AudioProcessor {
+	getName(): string {
+		return 'HP Sweep Down';
+	}
+
+	getDescription(): string {
+		return 'Sweeps a high-pass filter from thin to full';
+	}
+
+	getCategory(): ProcessorCategory {
+		return 'Filter';
+	}
+
+	process(leftIn: Float32Array, rightIn: Float32Array): [Float32Array, Float32Array] {
+		const length = leftIn.length;
+		const leftOut = new Float32Array(length);
+		const rightOut = new Float32Array(length);
+
+		const sampleRate = 44100;
+		const startFreq = 8000;
+		const endFreq = 20;
+		const Q = 1.5;
+
+		let lx1 = 0, lx2 = 0, ly1 = 0, ly2 = 0;
+		let rx1 = 0, rx2 = 0, ry1 = 0, ry2 = 0;
+
+		let b0 = 0, b1 = 0, b2 = 0, a1 = 0, a2 = 0;
+
+		for (let i = 0; i < length; i++) {
+			if (i % 64 === 0) {
+				const t = i / length;
+				const freq = startFreq * Math.pow(endFreq / startFreq, t);
+				const omega = 2.0 * Math.PI * freq / sampleRate;
+				const alpha = Math.sin(omega) / (2.0 * Q);
+
+				const a0 = 1.0 + alpha;
+				b0 = ((1.0 + Math.cos(omega)) / 2.0) / a0;
+				b1 = (-(1.0 + Math.cos(omega))) / a0;
+				b2 = b0;
+				a1 = (-2.0 * Math.cos(omega)) / a0;
+				a2 = (1.0 - alpha) / a0;
+			}
+
+			const lx0 = leftIn[i];
+			const rx0 = rightIn[i];
+
+			leftOut[i] = b0 * lx0 + b1 * lx1 + b2 * lx2 - a1 * ly1 - a2 * ly2;
+			rightOut[i] = b0 * rx0 + b1 * rx1 + b2 * rx2 - a1 * ry1 - a2 * ry2;
+
+			lx2 = lx1;
+			lx1 = lx0;
+			ly2 = ly1;
+			ly1 = leftOut[i];
+
+			rx2 = rx1;
+			rx1 = rx0;
+			ry2 = ry1;
+			ry1 = rightOut[i];
+		}
+
+		return [leftOut, rightOut];
+	}
+}