Add clarifications to audioLevel

Author: Guido Urdaneta

index.bs

@@ -708,6 +708,21 @@ 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 locally sourced track, the level MUST be
+            taken directly from the source.
+
+            For remotely sourced tracks, this MUST be converted from the level
+            value defined in [[!RFC6464]]. If the RFC 6464 header extension is
+            not present in the received packets, this value SHOULD 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:
+            <code class="math">10^(-rfc_level/20)</code>.
         </p>
     </dd>
 </dl>