Add documentation on ID3 parsing

pages/advanced/event-handling.md

@@ -19,16 +19,20 @@ dash.js supports inline and inband events included in the MPD and the media segm
 timing and how to use them please checkout ISO/IEC 23009-1 and the DASH-IF IOP Guidelines.
 
 ## Example
-An example is available as part of the [sample section](https://reference.dashif.org/dash.js/nightly/samples/advanced/listening-to-SCTE-EMSG-events.html).
+
+An example is available as part of
+the [sample section](https://reference.dashif.org/dash.js/nightly/samples/advanced/listening-to-SCTE-EMSG-events.html).
 
 ## Inband Events
-Inband events are events that are included in the ISOBMFF segments as an `emsg` box. 
+
+Inband events are events that are included in the ISOBMFF segments as an `emsg` box.
 The `schemeIdUri` and the `value` of inband events need to be signaled in the MPD using an `InbandEventStream` element.
 
 An example of an `InbandEventStream` element and the structure of the `emsg` box are depicted below:
 
 ```xml
-<InbandEventStream schemeIdUri="urn:scte:scte35:2013:xml" value="999" />
+
+<InbandEventStream schemeIdUri="urn:scte:scte35:2013:xml" value="999"/>
 ```
 
 ```
@@ -58,7 +62,8 @@ MPD events are signaled directly in the MPD. Events of the same type are summari
 An example of an MPD event is depicted below.
 
 ```xml
-<EventStream schemeIdUri="urn:scte:scte35:2013:xml" value="999" >
+
+<EventStream schemeIdUri="urn:scte:scte35:2013:xml" value="999">
     <Event duration="1" presentationTime="10">someMessage</Event>
 </EventStream>
 ```
@@ -67,15 +72,16 @@ An example of an MPD event is depicted below.
 
 ### Application events
 
-dash.js dispatches events that are not directly processed by the player (application events) to the underlying application. To register for a specific type
+dash.js dispatches events that are not directly processed by the player (application events) to the underlying
+application. To register for a specific type
 of event use the `on` method of the `player` object and specify the target `schemeIdUri` to listen for:
 
 ```javascript
 const SCHEMEIDURI = "urn:scte:scte35:2013:xml";
 const EVENT_MODE_ON_START = dashjs.MediaPlayer.events.EVENT_MODE_ON_START;
 const EVENT_MODE_ON_RECEIVE = dashjs.MediaPlayer.events.EVENT_MODE_ON_RECEIVE;
 
-player.on(SCHEMEIDURI, showStartEvent, null); 
+player.on(SCHEMEIDURI, showStartEvent, null);
 player.on(SCHEMEIDURI, showReceiveEvent, null, { mode: EVENT_MODE_ON_RECEIVE });
 ```
 
@@ -93,3 +99,22 @@ Some events are to be processed by the DASH player directly and are not dispatch
 | `urn:mpeg:dash:event:2012`          | 1     | Triggers and MPD reload                                            |
 | `urn:mpeg:dash:event:callback:2015` | 1     | Sends a callback request to the provided URL ignoring the response |
 
+### ID3 parsing
+
+dash.js uses the [Common Media Library](https://github.com/streaming-video-technology-alliance/common-media-library) to
+support the parsing of ID3 time metadata for inband events. ID3 time metadata is signaled via
+the `https://aomedia.org/emsg/ID3` `schemeIdUri`. The parsed message data is dispatched via
+the `event.parsedMessageData`
+field. The raw ID3 message data is available via the `event.messageData` field. As an example:
+
+````js
+event.messageData = Uint8Array(89)[
+...]
+event.parsedMessageData = [
+    {
+        "key": "PRIV",
+        "info": "com.elementaltechnologies.timestamp.utc",
+        "data": {}
+    }
+]
+````