✨ feat: Host a relay on Hetzner (#114)

We are hosting a [MoQ](https://quic.video) relay on a remote (bare
metal) server on Hetzner

With a lot of help from @victorpahuus

packages/moq/playback/worker/video.ts

@@ -0,0 +1,84 @@
+import { Frame, Component } from "./timeline"
+import * as MP4 from "../../media/mp4"
+import * as Message from "./message"
+
+export class Renderer {
+	#canvas: OffscreenCanvas
+	#timeline: Component
+
+	#decoder!: VideoDecoder
+	#queue: TransformStream<Frame, VideoFrame>
+
+	constructor(config: Message.ConfigVideo, timeline: Component) {
+		this.#canvas = config.canvas
+		this.#timeline = timeline
+
+		this.#queue = new TransformStream({
+			start: this.#start.bind(this),
+			transform: this.#transform.bind(this),
+		})
+
+		this.#run().catch(console.error)
+	}
+
+	async #run() {
+		const reader = this.#timeline.frames.pipeThrough(this.#queue).getReader()
+		for (;;) {
+			const { value: frame, done } = await reader.read()
+			if (done) break
+
+			self.requestAnimationFrame(() => {
+				this.#canvas.width = frame.displayWidth
+				this.#canvas.height = frame.displayHeight
+
+				const ctx = this.#canvas.getContext("2d")
+				if (!ctx) throw new Error("failed to get canvas context")
+
+				ctx.drawImage(frame, 0, 0, frame.displayWidth, frame.displayHeight) // TODO respect aspect ratio
+				frame.close()
+			})
+		}
+	}
+
+	#start(controller: TransformStreamDefaultController<VideoFrame>) {
+		this.#decoder = new VideoDecoder({
+			output: (frame: VideoFrame) => {
+				controller.enqueue(frame)
+			},
+			error: console.error,
+		})
+	}
+
+	#transform(frame: Frame) {
+		// Configure the decoder with the first frame
+		if (this.#decoder.state !== "configured") {
+			const { sample, track } = frame
+
+			const desc = sample.description
+			const box = desc.avcC ?? desc.hvcC ?? desc.vpcC ?? desc.av1C
+			if (!box) throw new Error(`unsupported codec: ${track.codec}`)
+
+			const buffer = new MP4.Stream(undefined, 0, MP4.Stream.BIG_ENDIAN)
+			box.write(buffer)
+			const description = new Uint8Array(buffer.buffer, 8) // Remove the box header.
+
+			if (!MP4.isVideoTrack(track)) throw new Error("expected video track")
+
+			this.#decoder.configure({
+				codec: track.codec,
+				codedHeight: track.video.height,
+				codedWidth: track.video.width,
+				description,
+				// optimizeForLatency: true
+			})
+		}
+
+		const chunk = new EncodedVideoChunk({
+			type: frame.sample.is_sync ? "key" : "delta",
+			data: frame.sample.data,
+			timestamp: frame.sample.dts / frame.track.timescale,
+		})
+
+		this.#decoder.decode(chunk)
+	}
+}