> ## Documentation Index > Fetch the complete documentation index at: https://apidoc.cometapi.com/llms.txt > Use this file to discover all available pages before exploring further. # 建立一個 Runway 影片轉影片任務 > 使用 CometAPI Runway POST /runwayml/v1/video_to_video 啟動影片轉影片生成任務、設定 X-Runway-Version，並轉換來源片段。 使用此端點可透過 Runway 的影片轉影片工作流程轉換既有的來源片段。它會啟動非同步任務，而不是立即回傳最終輸出。 ## 呼叫之前 * 準備符合供應商輸入需求的來源影片 * 加入所需的 `X-Runway-Version` 標頭，以使用你想要的功能集 * 先從一個描述變更的簡短 Prompt 開始，而不是完整分鏡腳本 ## 輸出比例 | 設定 | 支援的值 | 預設起始點 | 邊界行為 | | ------- | ------------------------------------------------------ | ---------- | --------------------- | | `ratio` | `1280:720`、`720:1280`，或所選 Runway model/version 接受的其他比例 | `1280:720` | 在可行情況下，請與來源片段的方向保持一致。 | 此端點預期使用以冒號分隔的 `ratio` 值。對於 `1280x720` 輸出，請使用 `1280:720`；對於 `720x1280`，請使用 `720:1280`；並非所有 Runway 影片轉影片路由都接受 `1280x720`。 ## 任務流程 從此端點啟動任務，並儲存回傳的 task id。 使用 [取得 Runway 任務](./runway-to-get-task-details)，直到任務進入終止狀態。 透過你的一般媒體處理流程下載或保存完成的資產。 ## OpenAPI ````yaml api/openapi/video/runway/official-format/post-generate-a-video-from-a-video.openapi.json POST /runwayml/v1/video_to_video openapi: 3.1.0 info: title: Generate a video from a video API version: 1.0.0 servers: - url: https://api.cometapi.com security: - bearerAuth: [] paths: /runwayml/v1/video_to_video: post: summary: Generate a video from a video operationId: generate_a_video_from_a_video parameters: - name: X-Runway-Version in: header required: true description: Runway API version header, for example `2024-11-06`. schema: type: string requestBody: required: true content: application/json: schema: type: object required: - videoUri - promptText - seed - model - references - ratio - contentModeration properties: videoUri: type: string description: >- HTTPS URL of the source video, or a base64 data URI containing the video. default: https://your-video-host/source.mp4 promptText: type: string description: >- Text prompt describing the desired output. Maximum 1000 characters. default: A cat yawning in slow motion. seed: type: integer description: 'Random seed for reproducible results. Range: 0–4294967295.' default: 1 model: type: string description: Model variant to use. default: gen4_aleph references: type: array description: >- Optional reference images to guide generation. Each item must include `type` (e.g. `image`) and `uri` (HTTPS URL). items: type: object properties: type: type: string uri: type: string default: - {} ratio: type: string description: >- Requested output frame shape. Use colon-separated values such as 1280:720 or 720:1280; read them as 1280x720 and 720x1280 targets. Do not assume every Runway video-to-video route accepts 1280x720 with an x separator. default: '1280:720' contentModeration: type: object required: - publicFigureThreshold properties: publicFigureThreshold: type: string description: >- Threshold for public-figure detection. Use `auto` for default behavior. default: publicFigureThreshold: auto default: videoUri: https://media.w3.org/2010/05/sintel/trailer.mp4 promptText: Make the motion feel cinematic. model: gen4_aleph references: - type: image uri: https://res.cloudinary.com/demo/image/upload/dog.jpg ratio: '1280:720' examples: Default: summary: Default value: videoUri: https://media.w3.org/2010/05/sintel/trailer.mp4 promptText: Make the motion feel cinematic. model: gen4_aleph references: - type: image uri: https://res.cloudinary.com/demo/image/upload/dog.jpg ratio: '1280:720' responses: '200': description: success content: application/json: schema: type: object required: - id properties: id: type: string description: >- The ID of the task that was created. Use this to retrieve the task later. example: id: 12a01a5e-ab55-4aa7-b002-7b873546cf76 x-codeSamples: - lang: Shell label: Default source: | curl https://api.cometapi.com/runwayml/v1/video_to_video \ -H "Authorization: Bearer $COMETAPI_KEY" \ -H "Content-Type: application/json" \ -d '{ "videoUri": "https://your-video-host/source.mp4", "promptText": "Make the motion feel cinematic.", "model": "gen4_aleph", "references": [ { "type": "image", "uri": "https://your-image-host/style.jpg" } ] }' - lang: Python label: Default source: > import os import requests response = requests.post( "https://api.cometapi.com/runwayml/v1/video_to_video", headers={"Authorization": "Bearer " + os.environ["COMETAPI_KEY"]}, json={ "videoUri": "https://your-video-host/source.mp4", "promptText": "Make the motion feel cinematic.", "model": "gen4_aleph", "references": [ { "type": "image", "uri": "https://your-image-host/style.jpg" } ] }, ) task = response.json() print(task["id"]) # poll GET /runwayml/v1/tasks/{id} until the output array appears - lang: JavaScript label: Default source: > const response = await fetch("https://api.cometapi.com/runwayml/v1/video_to_video", { method: "POST", headers: { Authorization: `Bearer ${process.env.COMETAPI_KEY}`, "Content-Type": "application/json", }, body: JSON.stringify({ "videoUri": "https://your-video-host/source.mp4", "promptText": "Make the motion feel cinematic.", "model": "gen4_aleph", "references": [ { "type": "image", "uri": "https://your-image-host/style.jpg" } ] }), }); const task = await response.json(); console.log(task.id); // poll GET /runwayml/v1/tasks/{id} until the output array appears components: securitySchemes: bearerAuth: type: http scheme: bearer description: Bearer token authentication. Use your CometAPI key. ````