大规模更智能直播：为所有 Netflix 直播活动推出 VBR

By Renata Teixeira, Zhi Li, Reenal Mahajan, and Wei Wei

作者：Renata Teixeira、Zhi Li、Reenal Mahajan 和 Wei Wei

On January 26, 2026, we flipped an important switch for Live at Netflix: all Live events are now encoded using VBR (Variable Bitrate) instead of CBR (Constant Bitrate). It sounds like a small configuration change, but it required us to revisit some of the foundational assumptions behind how we deliver Live video at global scale.

2026 年 1 月 26 日，我们为 Netflix 的 Live 翻转了一个重要的开关：所有 Live 活动现在使用 VBR (可变比特率) 而非 CBR (恒定比特率) 进行编码。这听起来像是一个小的配置更改，但它要求我们重新审视我们全球规模交付 Live 视频背后的某些基础假设。

VBR lets us tailor the bitrate to the actual complexity of the scene, instead of sending every second of video at roughly the same bitrate. When a scene is simple, VBR “shaves off” bits that wouldn’t improve what you see on screen; when a scene is complex, it spends more bits to preserve quality. (The more general idea is often referred to as capped variable bitrate, or capped VBR.) That makes our encodes more efficient and our network more scalable. But it also makes traffic much less predictable: large bitrate swings can overload servers and CDNs, and our old assumptions about “what bitrate equals what quality” no longer hold. As a result, we have to rethink both how we manage delivery and capacity, and which bitrates we offer for each version of the stream. In our live pipeline, we currently use AWS Elemental MediaLive, where this “capped” VBR is implemented using the QVBR (Quality‑Defined Variable Bitrate) setting.

VBR 允许我们根据场景的实际复杂度调整比特率，而不是以大致相同的比特率发送视频的每一秒。当场景简单时，VBR “shaves off” 不会改善屏幕上显示效果的比特；当场景复杂时，它花费更多比特来保持质量。（更通用的概念通常被称为 capped variable bitrate，或 capped VBR。）这使我们的编码更高效，我们的网络更具可扩展性。但它也使流量不可预测得多：大的比特率波动可能使服务器和 CDNs 过载，我们关于“什么比特率等于什么质量”的旧假设不再成立。因此，我们必须重新思考我们如何管理交付和容量，以及为流媒体的每个版本提供哪些比特率。在我们的直播管道中，我们目前使用 AWS Elemental MediaLive，在那里这种“capped” VBR 使用 QVBR (质量定义的可变比特率) 设置实现。

| Why Move Live from CBR to VBR?

| 为什么将 Live 从 CBR 转向 VBR？

Our initial Live encoding pipeline used constant bitrate (CBR). For each encoded stream, we configured a r...