Add a note telling why backpressure is disabled

Author: youennf

index.bs

@@ -90,7 +90,7 @@ At construction of each {{RTCRtpSender}} or {{RTCRtpReceiver}}, run the followin
 5. Set [=this=].`[[readable]]`.`[[owner]]` to |this|.
 6. Initialize [=this=].`[[writable]]` to a new {{WritableStream}}.
 7. <a dfn for="WritableStream">Set up</a> [=this=].`[[writable]]` with its [=WritableStream/set up/writeAlgorithm=] set to [$writeEncodedData$] given |this| as parameter and its [=WritableStream/set up/highWaterMark=] set to <code>Infinity</code>.
-    <p class="note">highWaterMark is set to Infinity to explicitly disable backpressure. The goal is to limit buffering as much as possible.</p>
+    <p class="note">highWaterMark is set to Infinity to explicitly disable backpressure.</p>
 8. Set [=this=].`[[writable]]`.`[[owner]]` to |this|.
 9. Initialize [=this=].`[[pipeToController]]` to null.
 1. Initialize [=this=].`[[lastReceivedFrameCounter]]` to <code>0</code>.
@@ -101,6 +101,15 @@ At construction of each {{RTCRtpSender}} or {{RTCRtpReceiver}}, run the followin
     <!-- FIXME: Use pipeTo algorithm when available. -->
     3. Call <a href="https://streams.spec.whatwg.org/#readable-stream-pipe-to">pipeTo</a> with [=this=].`[[readable]]`, [=this=].`[[writable]]`, preventClose equal to true, preventAbort equal to true, preventCancel equal to true and [=this=].`[[pipeToController]]`.signal.
 
+<p class=note>
+Streams backpressure can optimize throughput while limiting processing and memory consumption by pausing data production as early as possible in a data pipeline.
+This proves useful in contexts where reliability is essential and latency is less of a concern.
+On the other hand, WebRTC media pipelines favour latency over reliability, for instance by allowing to drop frames at various places and by using recovery mechanisms.
+Buffering within WebRTC encoded transform would add latency without allowing web applications to adapt much.
+The User Agent is responsible to do these adaptations, especially since it controls both ends of the transform.
+For those reasons, streams backpressure is disabled in WebRTC encoded transforms.
+</p>
+
 ### Stream processing ### {#stream-processing}
 
 The <dfn abstract-op>readEncodedData</dfn> algorithm is given a |rtcObject| as parameter. It is defined by running the following steps: