[中文]

用途:

• 获取指定 itag 的已签名播放地址
• 配合 get_video_streams 接口使用，先获取所有格式，再选择 itag 获取播放地址

代理要求:

• 调用本接口无需配置或传入代理；本接口不接受 proxy_url，无法指定签名链接的公网出口。
• 已签名不等于可从任意网络下载；下载端出口不同可能收到 403。 需要自带代理完成下载时，推荐 get_video_streams_v3。
• V3 首选固定出口或粘性会话的美国住宅代理，也可用固定公网出口的静态住宅/ISP 代理； 数据中心代理不作为首选。美国并非强制地区：地区受限视频应选允许访问的国家/地区， 并在获取链接与下载时保持同一实际公网出口。

参数:

• video_id: 视频ID（推荐）
• video_url: 完整的视频URL（可选）
• itag: 格式标识符，从 get_video_streams 接口返回的格式列表中选择

返回数据:

• itag: 格式标识符
• url: 已签名的播放地址（不保证跨公网出口可下载）
• expires_in_seconds: URL有效期（通常为6小时 = 21600秒）

注意事项:

• 播放地址有时效性（约6小时），过期后需重新获取
• URL 长度较长（约1000-2000字符）
• 某些视频可能受地区限制

[English]

Purpose:

• Get a signed playback URL for a specific itag
• Use with get_video_streams endpoint: first get all formats, then select itag to get playback URL

Proxy requirements:

• You do not need to configure or provide a proxy to call this endpoint. It does not accept proxy_url or let you choose the public exit for the signed URL.
• A signed URL is not guaranteed to download from every network; a different downloader exit may receive 403. Prefer get_video_streams_v3 when using your own download proxy.
• For V3, prefer a US residential proxy with a fixed exit or sticky session, or a static residential/ISP proxy with a fixed public exit. Datacenter proxies are not the first choice. The US is not mandatory: choose a region where the video is available and keep the same actual exit for retrieval and download.

Parameters:

• video_id: Video ID (recommended)
• video_url: Full video URL (optional)
• itag: Format identifier, selected from formats list returned by get_video_streams

Returns:

• itag: Format identifier
• url: Signed playback URL (download from another public exit is not guaranteed)
• expires_in_seconds: URL validity period (typically 6 hours = 21600 seconds)

Notes:

• Playback URLs expire after approximately 6 hours, need to regenerate after expiration
• URL length is long (approximately 1000-2000 characters)
• Some videos may have regional restrictions

[示例/Example]

video_id = "dQw4w9WgXcQ" itag = 18 # 360p mp4 with audio