From f1043734438c8518a302f698d9ae6583a75f0c14 Mon Sep 17 00:00:00 2001
From: cashmere <cashmere@autistici.org>
Date: Sun, 16 Aug 2026 06:16:56 +0200
Subject: feat: add transitions, track mixing, and voiceover controls

---
 apps/web/src/voiceover/live-waveform.tsx | 171 +++++++++++++++++++++++++++++++
 1 file changed, 171 insertions(+)
 create mode 100644 apps/web/src/voiceover/live-waveform.tsx

(limited to 'apps/web/src/voiceover/live-waveform.tsx')

diff --git a/apps/web/src/voiceover/live-waveform.tsx b/apps/web/src/voiceover/live-waveform.tsx
new file mode 100644
index 00000000..cd25c833
--- /dev/null
+++ b/apps/web/src/voiceover/live-waveform.tsx
@@ -0,0 +1,171 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+import { cn } from "@/utils/ui";
+import { getActiveVoiceOverRecordingStream } from "@/voiceover/recorder";
+
+const FFT_SIZE = 1024;
+const HISTORY_SIZE = 96;
+
+export function VoiceOverLiveWaveform({
+	recording,
+	className,
+}: {
+	recording: boolean;
+	className?: string;
+}) {
+	const canvasRef = useRef<HTMLCanvasElement>(null);
+	const levelRef = useRef(0);
+	const historyRef = useRef<number[]>(
+		Array.from({ length: HISTORY_SIZE }, () => 0),
+	);
+	const [level, setLevel] = useState(0);
+
+	useEffect(() => {
+		const canvas = canvasRef.current;
+		if (!canvas || !recording) {
+			drawWaveform({
+				canvas,
+				history: historyRef.current,
+				level: 0,
+			});
+			setLevel(0);
+			return;
+		}
+
+		const stream = getActiveVoiceOverRecordingStream();
+		if (!stream) {
+			return;
+		}
+
+		const audioContext = createAudioContext();
+		const source = audioContext.createMediaStreamSource(stream);
+		const analyser = audioContext.createAnalyser();
+		analyser.fftSize = FFT_SIZE;
+		analyser.smoothingTimeConstant = 0.72;
+		source.connect(analyser);
+
+		const samples = new Uint8Array(analyser.fftSize);
+		let animationFrame = 0;
+		let lastLevelUpdate = 0;
+
+		const render = (timestamp: number) => {
+			analyser.getByteTimeDomainData(samples);
+			const rms = getRmsLevel({ samples });
+			levelRef.current = rms;
+			historyRef.current = [...historyRef.current.slice(1), rms];
+			drawWaveform({
+				canvas,
+				history: historyRef.current,
+				level: rms,
+			});
+
+			if (timestamp - lastLevelUpdate > 80) {
+				lastLevelUpdate = timestamp;
+				setLevel(rms);
+			}
+			animationFrame = requestAnimationFrame(render);
+		};
+
+		animationFrame = requestAnimationFrame(render);
+
+		return () => {
+			cancelAnimationFrame(animationFrame);
+			source.disconnect();
+			analyser.disconnect();
+			void audioContext.close();
+		};
+	}, [recording]);
+
+	return (
+		<div className={cn("space-y-2", className)}>
+			<div className="bg-muted relative h-16 overflow-hidden rounded-sm border">
+				<canvas ref={canvasRef} className="absolute inset-0 size-full" />
+			</div>
+			<div className="bg-muted h-1.5 overflow-hidden rounded-full">
+				<div
+					className="bg-primary h-full rounded-full transition-[width]"
+					style={{ width: `${Math.min(100, Math.round(level * 140))}%` }}
+				/>
+			</div>
+		</div>
+	);
+}
+
+function getRmsLevel({ samples }: { samples: Uint8Array }): number {
+	let sum = 0;
+	for (let index = 0; index < samples.length; index++) {
+		const centered = ((samples[index] ?? 128) - 128) / 128;
+		sum += centered * centered;
+	}
+	return Math.sqrt(sum / samples.length);
+}
+
+function drawWaveform({
+	canvas,
+	history,
+	level,
+}: {
+	canvas: HTMLCanvasElement | null;
+	history: number[];
+	level: number;
+}): void {
+	if (!canvas) {
+		return;
+	}
+
+	const rect = canvas.getBoundingClientRect();
+	const dpr = window.devicePixelRatio || 1;
+	const width = Math.max(1, Math.round(rect.width * dpr));
+	const height = Math.max(1, Math.round(rect.height * dpr));
+	if (canvas.width !== width || canvas.height !== height) {
+		canvas.width = width;
+		canvas.height = height;
+	}
+
+	const ctx = canvas.getContext("2d");
+	if (!ctx) {
+		return;
+	}
+
+	ctx.setTransform(1, 0, 0, 1, 0, 0);
+	ctx.clearRect(0, 0, width, height);
+
+	const centerY = height / 2;
+	const step = width / Math.max(1, history.length);
+
+	ctx.strokeStyle = "rgba(148, 163, 184, 0.35)";
+	ctx.lineWidth = 1;
+	ctx.beginPath();
+	ctx.moveTo(0, centerY);
+	ctx.lineTo(width, centerY);
+	ctx.stroke();
+
+	for (let index = 0; index < history.length; index++) {
+		const value = Math.max(0, history[index] ?? 0);
+		const barHeight = Math.max(1, Math.min(height, value * height * 2.8));
+		const x = Math.round(index * step);
+		const y = Math.round(centerY - barHeight / 2);
+		ctx.fillStyle =
+			value > 0.62
+				? "rgba(239, 68, 68, 0.9)"
+				: value > 0.32
+					? "rgba(245, 158, 11, 0.9)"
+					: "rgba(34, 197, 94, 0.9)";
+		ctx.fillRect(x, y, Math.max(1, Math.floor(step - 1)), barHeight);
+	}
+
+	if (level > 0.78) {
+		ctx.fillStyle = "rgba(239, 68, 68, 0.18)";
+		ctx.fillRect(0, 0, width, height);
+	}
+}
+
+function createAudioContext(): AudioContext {
+	const AudioContextConstructor =
+		window.AudioContext ||
+		(window as typeof window & { webkitAudioContext?: typeof AudioContext })
+			.webkitAudioContext;
+
+	return new AudioContextConstructor();
+}
-- 
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