✨ 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/contribute/video.ts

@@ -0,0 +1,111 @@
+const SUPPORTED = [
+	"avc1", // H.264
+	"hev1", // HEVC (aka h.265)
+	// "av01", // TDOO support AV1
+]
+
+export interface EncoderSupported {
+	codecs: string[]
+}
+
+export class Encoder {
+	#encoder!: VideoEncoder
+	#encoderConfig: VideoEncoderConfig
+	#decoderConfig?: VideoDecoderConfig
+
+	// true if we should insert a keyframe, undefined when the encoder should decide
+	#keyframeNext: true | undefined = true
+
+	// Count the number of frames without a keyframe.
+	#keyframeCounter = 0
+
+	// Converts raw rames to encoded frames.
+	frames: TransformStream<VideoFrame, VideoDecoderConfig | EncodedVideoChunk>
+
+	constructor(config: VideoEncoderConfig) {
+		config.bitrateMode ??= "constant"
+		config.latencyMode ??= "realtime"
+
+		this.#encoderConfig = config
+
+		this.frames = new TransformStream({
+			start: this.#start.bind(this),
+			transform: this.#transform.bind(this),
+			flush: this.#flush.bind(this),
+		})
+	}
+
+	static async isSupported(config: VideoEncoderConfig) {
+		// Check if we support a specific codec family
+		const short = config.codec.substring(0, 4)
+		if (!SUPPORTED.includes(short)) return false
+
+		// Default to hardware encoding
+		config.hardwareAcceleration ??= "prefer-hardware"
+
+		// Default to CBR
+		config.bitrateMode ??= "constant"
+
+		// Default to realtime encoding
+		config.latencyMode ??= "realtime"
+
+		const res = await VideoEncoder.isConfigSupported(config)
+		return !!res.supported
+	}
+
+	#start(controller: TransformStreamDefaultController<EncodedVideoChunk>) {
+		this.#encoder = new VideoEncoder({
+			output: (frame, metadata) => {
+				this.#enqueue(controller, frame, metadata)
+			},
+			error: (err) => {
+				throw err
+			},
+		})
+
+		this.#encoder.configure(this.#encoderConfig)
+	}
+
+	#transform(frame: VideoFrame) {
+		const encoder = this.#encoder
+
+		// Set keyFrame to undefined when we're not sure so the encoder can decide.
+		encoder.encode(frame, { keyFrame: this.#keyframeNext })
+		this.#keyframeNext = undefined
+
+		frame.close()
+	}
+
+	#enqueue(
+		controller: TransformStreamDefaultController<VideoDecoderConfig | EncodedVideoChunk>,
+		frame: EncodedVideoChunk,
+		metadata?: EncodedVideoChunkMetadata,
+	) {
+		if (!this.#decoderConfig) {
+			const config = metadata?.decoderConfig
+			if (!config) throw new Error("missing decoder config")
+
+			controller.enqueue(config)
+			this.#decoderConfig = config
+		}
+
+		if (frame.type === "key") {
+			this.#keyframeCounter = 0
+		} else {
+			this.#keyframeCounter += 1
+			if (this.#keyframeCounter + this.#encoder.encodeQueueSize >= 2 * this.#encoderConfig.framerate!) {
+				this.#keyframeNext = true
+			}
+		}
+
+		controller.enqueue(frame)
+	}
+
+	#flush() {
+		this.#encoder.close()
+	}
+
+	get config() {
+		return this.#encoderConfig
+	}
+}