diff --git a/index.bs b/index.bs index 7d7dd73..e47097a 100644 --- a/index.bs +++ b/index.bs @@ -708,6 +708,23 @@ dictionary RTCEncodedAudioFrameMetadata : RTCEncodedFrameMetadata { The audio level of this frame. The value is between 0..1 (linear), where 1.0 represents 0 dBov, 0 represents silence, and 0.5 represents approximately 6 dBSPL change in the sound pressure level from 0 dBov. + + If the frame comes from a remotely sourced track, this MUST be + converted from the level value defined in [[!RFC6464]]. If the + [[!RFC6464]] header extension is not present in the received packets of the frame, + this value MUST be absent. + This RFC defines the audio level as an integral value from 0 to 127 + representing the audio level in negative decibels relative to the + loudest signal that the system could possibly encode. Thus, 0 + represents the loudest signal the system could possibly encode, + and 127 represents silence. To convert these values to the linear + 0..1 range, a value of 127 is converted to 0, and all other values + are converted using the equation: + 10^(-rfc_level/20). + + If the frame comes from a locally sourced track, the level MUST be + taken directly from the source and used as input to generate a value + for the [[!RFC6464]] header extension, if negotiated.