Guide a Video with Reference Images

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const apiKey = process.env.OPENROUTER_API_KEY;
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const referenceImageUrl = process.env.REFERENCE_IMAGE_URL;
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if (!apiKey) {
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  throw new Error("Set OPENROUTER_API_KEY first.");
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}
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if (!referenceImageUrl) {
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  throw new Error(
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    "Set REFERENCE_IMAGE_URL to a directly downloadable image URL.",
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  );
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}
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const response = await fetch("https://openrouter.ai/api/v1/videos", {
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  method: "POST",
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  headers: {
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    Authorization: `Bearer ${apiKey}`,
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    "Content-Type": "application/json",
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  },
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  body: JSON.stringify({
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    model: "bytedance/seedance-2.0-fast",
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    prompt:
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      "Create a 4-second product video of the same backpack from the reference image. Keep the shape, color, and logo placement consistent. Place it on a wet city sidewalk at night with neon reflections. Use a slow orbiting camera move and realistic lighting.",
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    duration: 4,
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    resolution: "720p",
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    aspect_ratio: "16:9",
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    generate_audio: false,
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    input_references: [
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      {
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        type: "image_url",
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        image_url: {
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          url: referenceImageUrl,
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        },
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      },
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    ],
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  }),
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});
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if (!response.ok) {
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  throw new Error(await response.text());
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}
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const job = await response.json();
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console.log(job);

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const characterSideUrl = process.env.CHARACTER_SIDE_URL;
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const styleReferenceUrl = process.env.STYLE_REFERENCE_URL;
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if (!characterSideUrl || !styleReferenceUrl) {
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  throw new Error("Set CHARACTER_SIDE_URL and STYLE_REFERENCE_URL first.");
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}
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const inputReferences = [
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  {
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    type: "image_url",
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    image_url: { url: referenceImageUrl },
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  },
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  {
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    type: "image_url",
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    image_url: { url: characterSideUrl },
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  },
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  {
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    type: "image_url",
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    image_url: { url: styleReferenceUrl },
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  },
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];

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import { writeFile } from "node:fs/promises";
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async function waitForVideo(job) {
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  let current = job;
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  for (let attempt = 1; attempt <= 60; attempt += 1) {
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    if (current.status === "completed") {
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      return current;
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    }
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    if (current.status === "failed") {
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      throw new Error(current.error ?? "Video generation failed.");
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    }
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    if (["cancelled", "expired"].includes(current.status)) {
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      throw new Error(current.error ?? `Video generation ${current.status}.`);
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    }
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    await new Promise((resolve) => setTimeout(resolve, 30_000));
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    if (!current.polling_url) {
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      throw new Error("Video job did not include a polling_url.");
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    }
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    const pollingUrl = new URL(current.polling_url, "https://openrouter.ai");
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    const response = await fetch(pollingUrl, {
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      headers: {
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        Authorization: `Bearer ${apiKey}`,
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      },
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    });
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    if (!response.ok) {
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      throw new Error(await response.text());
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    }
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    current = await response.json();
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  }
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  throw new Error("Video generation did not complete after 60 attempts.");
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}
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async function downloadVideo(job) {
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  const videoUrl =
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    job.unsigned_urls?.[0] ??
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    `https://openrouter.ai/api/v1/videos/${job.id}/content?index=0`;
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  const response = await fetch(videoUrl, {
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    headers: videoUrl.startsWith("https://openrouter.ai/api/")
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      ? { Authorization: `Bearer ${apiKey}` }
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      : undefined,
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  });
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  if (!response.ok) {
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    throw new Error(await response.text());
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  }
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  return Buffer.from(await response.arrayBuffer());
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}
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const completedJob = await waitForVideo(job);
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const videoBuffer = await downloadVideo(completedJob);
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await writeFile("reference-video.mp4", videoBuffer);
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console.log("Saved reference-video.mp4");