WebRTC Simulcast：RTCRtpSender.setParameters 编码层配置

概述Simulcast 通过发送多层编码（高/中/低）让接收端按网络与设备选择合适层。`sender.setParameters({ encodings })` 用于指定码率与缩放等参数。用法/示例const pc = new RTCPeerConnection() const stream = await navigator.mediaDevices.getUserMedia({ video: { width: 1280, height: 720 } }) const sender = pc.addTrack(stream.getVideoTracks()[0], stream) const params = sender.getParameters() params.encodings = [ { rid: 'h', maxBitrate: 2_000_000 }, { rid: 'm', maxBitrate: 1_000_000, scaleResolutionDownBy: 1.5 }, { rid: 'l', maxBitrate: 400_000, scaleResolutionDownBy: 2 } ] await sender.setParameters(params) 工程建议依据设备与网络选择层数与码率；避免过多层造成 CPU 与带宽负担。与 SVC/编码器能力协作并校验浏览器支持；记录丢包与码率指标做自适应。在不支持 Simulcast 的环境回退单层或服务端转码。参考与验证W3C：WebRTC — https://www.w3.org/TR/webrtc/MDN：RTCRtpSender — https://developer.mozilla.org/docs/Web/API/RTCRtpSender