diff --git a/webrtc-stats.html b/webrtc-stats.html
index 6100d5c3..06647b7a 100644
--- a/webrtc-stats.html
+++ b/webrtc-stats.html
@@ -350,7 +350,7 @@ <h3>
              unsigned long pliCount;
              unsigned long nackCount;
              unsigned long sliCount;
-             unsigned long qpSum;
+             unsigned long long qpSum;
 };</pre>
           <section>
             <h2>
@@ -466,20 +466,21 @@ <h2>
                 </p>
               </dd>
               <dt><dfn><code>qpSum</code></dfn> of type
-                <span class="idlMemberType"><a>unsigned long</a></span>
+                <span class="idlMemberType"><a>unsigned long long</a></span>
               </dt>
               <dd>
                 <p>
                   The sum of the QP values of frames passed. The count
                   of frames is in <a>framesDecoded</a> for inbound
                   stream stats, and in <a>framesEncoded</a> for
-                  outbound stream stats.
+                  outbound stream stats. If QP varies across the frame,
+		  an average or typical QP value is recorded.
                 </p>
                 <p>
                   The definition of QP value depends on
                   the <a>codec</a>; for VP8, QP values are defined in
                   [[RFC6386]]. <!-- Need appropriate references for
-                  VP9 and H.264 -->
+                  VP8, VP9 and H.264 - RFC 6386 doesn't use the term -->
                 </p>
                 <p>Only valid for video.</p>
               </dd>
@@ -594,7 +595,7 @@ <h3>
              double             burstDiscardRate;
              double             gapLossRate;
              double             gapDiscardRate;
-             unsigned long     framesDecoded;
+             unsigned long      framesDecoded;
 };</pre>
             <section>
               <h2>