RTCRtpEncodingParameters.scaleResolutionDownBy - Web APIs
the rtcrtpencodingparameters dictionary's scaleresolutiondownby property can be used to specify a factor by which to reduce the size of a video track during encoding.
... syntax rtpencodingparameters.scaleresolutiondownby = scalingfactor; rtpencodingparameters = { scaleresolutiondownby: scalingfactor }; value a double-precison floating-point number specifying the amount by which to reduce the size of the video during encoding.
... specifications specification status comment webrtc 1.0: real-time communication between browsersthe definition of 'rtcrtpencodingparameters.scaleresolutiondownby' in that specification.

Index - Web APIs
3486 rtcrtpencodingparameters.scaleresolutiondownby api, codec, encoding, media, rtcrtpencodingparameters, rtp, reference, scale, scaling, settings, video, webrtc, webrtc api, parameters, rtc, scaleresolutiondownby, size the rtcrtpencodingparameters dictionary's scaleresolutiondownby property can be used to specify a factor by which to reduce the size of a video track during encoding.

RTCRtpEncodingParameters - Web APIs
scaleresolutiondownby only used for senders whose track's kind is video, this is a double-precision floating-point value specifying a factor by which to scale down the video during encoding.

RTCRtpSendParameters.encodings - Web APIs
scaleresolutiondownby only used for senders whose track's kind is video, this is a double-precision floating-point value specifying a factor by which to scale down the video during encoding.

RTCRtpSender.setParameters() - Web APIs
rangeerror the value specified for scaleresolutiondownby is less than 1.0, which would result in scaling up rather than down, which is not allowed; or one or more of the specified encodings' maxframerate values is less than 0.0.