Recipe 16.8. Listening for Cue Points

Problem

You want to listen for cue points encoded in the FLV.

Solution

Use an onCuePoint( ) callback.

Discussion

The FLV format allows you to embed cue points within the file. You can use cue points for many purposes, such as:

• Captions

• Synchronizing animations with video

• Logging video playback statistics

You have to embed the cue points in the FLV file using one of the FLV encoders such as the Flash Video Exporter (which ships with Flash Professional), On2 Flix (http:// www.on2.com), or Sorenson Squeeze (http:// www.sorensonmedia.com). When playing back the video, the Flash Player receives a notification when a cue point is reached. As with metadata, cue points don't use the standard event model used by most of ActionScript 3.0. Rather, when a cue point is reached Flash Player calls a callback method called onCuePoint( ). As with onMetaData( ) the onCuePoint( ) method must be defined for an object that is assigned to the client property of the NetStream object. The onCuePoint( ) method accepts one parameter, which is an object with the following properties:

name

The name assigned to the cue point when encoding.

time

The time at which the cue point occurs (in seconds)

type

Either "event" or "navigation," depending on which type was selected when encoding

parameters

An associative array with string key/value pairs assigned when encoding the FLV

The following illustrates one way in which you can create a client object, assign the onCuePoint reference, and assign the client object to the NetStream object:

var client:Object = new Object(  ); client.onCuePoint = onCuePoint; videoStream.client = client;

Then define the method appropriately:

private function onCuePoint(cuePoint:Object):void {     trace(cuePoint.name + " " + cuePoint.time); }

See Also

Recipe 16.4