Capture, receive, and RTP timestamp concept definitions & normative requirements for gUM/gDM

index.html

@@ -1155,20 +1155,20 @@ <h2>Constrainable Properties</h2>
       </table>
     </section>
     <section class="informative">
-      <h2>Timestamp concepts</h2>
+      <h2>Video timestamp concepts</h2>
       <p>
-        Media flowing inside media stream tracks comprise of a sequence of media frames, where
+        Video media flowing inside media stream tracks comprise of a sequence of video frames, where
         the frames are sampled from the media at instants spread out over time.
       </p>
+      <p>
+        Each video frame has a <dfn class="export">presentation timestamp</dfn>
+        which is relative to the first frame appearing on the track.
+      </p>
       <p>
         Each frame may have a <dfn class="export">capture timestamp</dfn> representing
         the instant it was captured. A source of frames can define how this timestamp is set, otherwise
         it is unset.
       </p>
-      <p>
-        Each video frame has a <dfn class="export">presentation timestamp</dfn>
-        which is relative to the first frame appearing on the track.
-      </p>
       <p>
         Each frame may have a <dfn class="export">receive timestamp</dfn> representing
         the last received timestamp of packets used to produce this video frame was received in its entirety.
@@ -1193,30 +1193,39 @@ <h5>Members</h5>
         <dl class="dictionary-members" data-link-for="VideoFrameMetadata" data-dfn-for="VideoFrameMetadata">
           <dt><dfn><code>captureTime</code></dfn> of type <span class="idlMemberType">DOMHighResTimeStamp</span></dt>
           <dd>
-            <p>
-              The capture timestamp of the frame relative to {{Performance}}.{{Performance/timeOrigin}}.
-              MUST be set to the [=capture timestamp=] of the source {{MediaStreamTrack}} video frame if set.
-              It is not [=map/exist|present=] if [=capture timestamp=] is unset.
+            <p>The capture timestamp of the frame relative to {{Performance}}.{{Performance/timeOrigin}}. It corresponds to
+              the [=capture timestamp=] of {{MediaStreamTrack}} video frames.
             </p>
           </dd>
           <dt><dfn><code>receiveTime</code></dfn> of type <span class="idlMemberType">DOMHighResTimeStamp</span></dt>
           <dd>
-            <p>
-              The receive time of the corresponding encoded frame relative to {{Performance}}.{{Performance/timeOrigin}}.
-              MUST be set to the [=receive timestamp=] of the source {{MediaStreamTrack}} video frame if set.
-              It is not [=map/exist|present=] if [=receive timestamp=] is unset.
-            </p>
+            <p>The receive time of the corresponding encoded frame relative to {{Performance}}.{{Performance/timeOrigin}}.
+              It corresponds to the [=receive timestamp=] of {{MediaStreamTrack}} video frames.</p>
           </dd>
           <dt><dfn><code>rtpTimestamp</code></dfn> of type <span class="idlMemberType">unsigned long</span></dt>
           <dd>
-            <p>
-              The RTP timestamp of the corresponding encoded frame.
-              MUST be set to the [=RTP timestamp=] of the source {{MediaStreamTrack}} video frames if set.
-              It is not [=map/exist|present=] if [=receive timestamp=] is unset.
-            </p>
+            <p>The RTP timestamp of the corresponding encoded frame.  It corresponds to [=RTP timestamp=] of
+            {{MediaStreamTrack}} video frames.</p>
           </dd>
         </dl>
       </section>
+      <h3>Algorithms</h3>
+      The <dfn for=VideoFrame class="export">Initialize Video Frame Timestamps From Internal MediaStreamTrack Video Frame</dfn>
+      algorithm runs with |frame| as input.
+      <ol>
+        <li>Set {{VideoFrame/timestamp}} from [=presentation timestamp=].</li>
+        <li>Set {{VideoFrameMetadata/captureTime}} from [=capture timestamp=] if set.</li>
+        <li>Set {{VideoFrameMetadata/receiveTime}} from [=receive timestamp=] if set.</li>
+        <li>Set {{VideoFrameMetadata/rtpTimestamp}} from [=RTP timestamp=] if set.</li>
+      </ol>
+      The <dfn for=VideoFrame class="export">Copy Video Frame Timestamps To Internal MediaStreamTrack Video Frame</dfn>
+      algorithm runs with |frame| as input.
+      <ol>
+        <li>Set [=presentation timestamp=] from {{VideoFrame/timestamp}}.</li>
+        <li>Set [=capture timestamp=] from {{VideoFrameMetadata/captureTime}} if [=map/exist|present=].</li>
+        <li>Set [=receive timestamp=] from {{VideoFrameMetadata/receiveTime}} if [=map/exist|present=].</li>
+        <li>Set [=RTP timestamp=] from {{VideoFrameMetadata/rtpTimestamp}} if [=map/exist|present=].</li>
+      </ol>
     </section>
     <section>
       <h3>Local video capture timestamps</h3>