Document rendition selection logic in README and update code commentary for rend…

…ition sort by viewport logic

@@ -101,5 +101,22 @@ configured. Easy [instructions are
 available](http://enable-cors.org/server.html) for popular webservers
 and most CDNs should have no trouble turning CORS on for your account.
 
+## MBR Rendition Selection Logic
+In situations where manifests have multiple renditions, the player will
+go through the following algorithm to determine the best rendition by
+bandwidth and viewport dimensions.
+
+- Start on index 0 as defined in the HLS Spec (link above)
+- On a successful load complete per segment determine the following;
+    - player.hls.bandwidth set to value as segment byte size over download time
+    - Viewport width/height as determined by player.width()/player.height()
+    - Playlists mapped and sorted by BANDWIDTH less than or equal to 1.1x player.hls.bandwidth
+    - Best playlist variant by BANDWIDTH determined
+    - Subset of bandwidth appropriate renditions mapped
+    - Subset validated for RESOLUTION attributes less than or equal to player dimensions
+    - Best playlist variant by RESOLUTION determined
+- Result is as follows;
+    - [Best RESOLUTION variant] OR [Best BANDWIDTH variant] OR [inital playlist in manifest]
+
 ## Release History
 _(Nothing yet)_

@@ -85,6 +85,8 @@ var
 
     rightWidth = rightWidth || window.Number.MAX_VALUE;
 
+    // NOTE - Fallback to bandwidth sort as appropriate in cases where multiple renditions
+    // have the same media dimensions/ resolution
     if (leftWidth === rightWidth && left.attributes.BANDWIDTH && right.attributes.BANDWIDTH) {
       return left.attributes.BANDWIDTH - right.attributes.BANDWIDTH;
     } else {