From d1be7b1e98329a733dd9f8a8c5b92776adfad770 Mon Sep 17 00:00:00 2001
From: Bernard Aboba <bernard.aboba@gmail.com>
Date: Sat, 17 Aug 2024 05:23:37 -0700
Subject: [PATCH] Move media capabilities discussion to negotiation section

---
 index.html | 66 ++++++++++++++++++++++++++++--------------------------
 1 file changed, 34 insertions(+), 32 deletions(-)

diff --git a/index.html b/index.html
index cb1b086..a2cfda8 100644
--- a/index.html
+++ b/index.html
@@ -312,16 +312,38 @@ <h2>Negotiation issues</h2>
             the application will negotiate codecs to be sent and received with
             the conferencing server. However, since scalability modes are not
             negotiated in Offer/Answer, the application needs to determine
-            which scalability modes the conference server supports by other
-            means.
+            which scalability modes the browser and conference server support
+            by other means.
+          </p>
+          <p>
+            The [[?Media-Capabilities]] API enables discovery of encoder and decoder
+            support for scalable video coding. {{VideoConfiguration//scalabilityMode}}
+            is used to query whether an encoder supports a 
+            {{RTCRtpEncodingParameters/scalabilityMode}} value, indicating whether
+            it is "supported", "smooth" and "power efficient".
+          </p>
+          <p>
+            The [[?Media-Capabilities]] API also provides information on decoder support
+            for spatial scalablity modes. {{VideoConfiguration/spatialScalability}}
+            indicates whether a decoder has the ability to support spatial prediction,
+            which requires the ability to use frames of a resolution different than
+            the current resolution as a dependency. If {{VideoConfiguration/spatialScalability}}
+            is set to <code>true</code>, the decoder can decode any
+            {{RTCRtpEncodingParameters/scalabilityMode}} value supported by the encoder.
+            If {{VideoConfiguration/spatialScalability}} is set to <code>false</code>
+            or is absent, the decoder cannot decode spatial scalability modes, but can
+            can decode all other {{RTCRtpEncodingParameters/scalabilityMode}} values
+            supported by the encoder.
           </p>
           <p>  
-            One way to handle this is for the SFM to indicate the combination
-            of codecs and scalability modes it can forward in the form of receiver
-            capabilities. After receiving the SFM's capabilities, the application
-            can compute the intersection of codec and
-            {{RTCRtpEncodingParameters/scalabilityMode}} values supported
-            by the browser's {{RTCRtpSender}} and the
+            Once an application has determined which combination of codecs and
+            {{RTCRtpEncodingParameters/scalabilityMode}} values it has available to use,
+            it needs to determine which of these combinations are supported by the SFM. 
+            One way to handle this is for the SFM to indicate the combination of codecs
+            and scalability modes it can forward in the form of receiver capabilities
+            After receiving the SFM's capabilities, the application can compute the
+            intersection of codec and {{RTCRtpEncodingParameters/scalabilityMode}} values
+            supported by the browser's {{RTCRtpSender}} and the
             <a title="Selective Forwarding Middlebox">SFM</a>'s receiver. This
             can be used to determine the arguments passed to the browser's
             {{RTCPeerConnection/addTransceiver()}} and {{RTCRtpSender/setParameters()}}
@@ -334,10 +356,10 @@ <h2>Negotiation issues</h2>
                 An <a title="Selective Forwarding Middlebox">SFM</a> that parses
                 codec payloads may only support the H.264/AVC codec without scalability and
                 the VP8 codec with temporal scalability. On the other hand, the browser
-                may be able to encode VP8 with temporal scalability, VP9 and AV1 with temporal
-                and spatial scalability and H.264/AVC with temporal scalability.
-                In this example, an application desiring to use SVC would only
-                be able to encode VP8 with temporal scalability.
+                may be able to encode VP8 with temporal scalability, VP9 and AV1 with
+                temporal and spatial scalability and H.264/AVC with temporal scalability.
+                In this example, an application desiring to use SVC would only be able
+                to encode VP8 with temporal scalability.
               </li>
               <li>
                 An <a title="Selective Forwarding Middlebox">SFM</a> may only support 
@@ -929,26 +951,6 @@ <h2>Persistent information</h2>
         is decodable for the codec in use can be obtained,
         which provides more information on hardware capabilities.
       </p>
-      <p>
-        The [[?Media-Capabilities]] API enables discovery of encoder and decoder
-        support for scalable video coding. {{VideoConfiguration//scalabilityMode}}
-        is used to query whether an encoder supports a 
-        {{RTCRtpEncodingParameters/scalabilityMode}} value, indicating whether
-        it is "supported", "smooth" and "power efficient".
-      </p>
-      <p>
-        The [[?Media-Capabilities]] API also provides information on decoder support
-        for spatial scalablity modes. {{VideoConfiguration/spatialScalability}}
-        indicates whether a decoder has the ability to support spatial prediction,
-        which requires the ability to use frames of a resolution different than
-        the current resolution as a dependency. If {{VideoConfiguration/spatialScalability}}
-        is set to <code>true</code>, the decoder can decode any
-        {{RTCRtpEncodingParameters/scalabilityMode}} value supported by the encoder.
-        If {{VideoConfiguration/spatialScalability}} is set to <code>false</code>
-        or is absent, the decoder cannot decode spatial scalability modes, but can
-        can decode all other {{RTCRtpEncodingParameters/scalabilityMode}} values
-        supported by the encoder.
-      </p>
       <p>
         As noted in [[?Media-Capabilities]] Section 3.1, the Media
         Capabilities API "will likely provide more accurate and