WebCodecs
for Node.js

// effects/textOverlay.js
// Runs identically in browser AND server

export function applyTextOverlay(frame, config) {
  const ctx = getContext(frame);
  ctx.font = config.font;
  ctx.fillStyle = config.color;
  ctx.fillText(config.text, config.x, config.y);
  return frame;
}

// In your Mediasoup server

participants.forEach(p => {
  const decoder = new VideoDecoder({
    output: frame => frames.set(p.id, frame)
  });
  p.videoTrack.pipe(decoder);
});

// Composite all participants in real-time
const composed = composePiP(frames, layout);
encoder.encode(composed);

const decoder = new VideoDecoder({
  output: async (frame) => {
    const dominated = await detectKill(frame);

    if (dominated && !clipping) {
      startClip(frame.timestamp);
    }

    if (clipping) {
      clipEncoder.encode(frame);
    }
  }
});

async function validateVideo(file) {
  let frozen = 0, black = 0, lastHash;

  for await (const frame of decode(file)) {
    const hash = perceptualHash(frame);
    if (hash === lastHash) frozen++;
    if (isBlack(frame)) black++;
    lastHash = hash;
  }

  return { decodable: true, frozen, black };
}

for await (const frame of decode(template)) {
  const t = frame.timestamp / 1e6;

  // Actual programming, not filter DSL
  if (customer.isPremium) {
    addGoldBorder(frame);
  }

  drawText(frame, customer.name, positions[t]);
  encoder.encode(frame, {
    keyFrame: t % 2 === 0
  });
}