Page 1 of 1 A cue point is any significant moment in time occurring within a video clip. Cue points enable you to access different segments of a video clip. With Flash Video, you can create and manage cue points in a variety of ways. This series provides a comprehensive guide to the use of cue points in Flash Video. In this first installment, you learn the basics of cue points and the requirements to create cue point data.
While cue points can add significant control to your Flash Video clips, you don't need cue points for all video content. A 15 or 30 second theatrical trailer for a blockbuster movie won't likely require cue points. Nor will a 60 second news brief on CNN.com require cue points. In general, anything less than 5 minutes in length will not benefit from cue points. Use the following checklist to help you decide if cue points will aid the playback of your video content:
Tip: If you need to add captions, text, or graphic overlays to your video for Flash presentations, you'll achieve better quality by layering such content on top of your video clip in the Flash movie. Don't be tempted to put such graphics and overlays into your video content directly in your editing software, as the compression used by Flash Video (On2 VP6 or Sorenson Spark) is not ideal for text and vector graphics.
A cue point usually contains at least one piece of information: a time within the video clip. So, if you have a video clip that showcases a collection of dog tricks, the starting time of each trick within the clip could be a cue point. All of the Flash Video components, including the Media and FLVPlayback components, delineate cue points in seconds, as a unit of time. You can use other units, such as video frames, for cue points, but you must convert your preferred unit of time into seconds if you're using Macromedia's components. Each cue point should also have a unique name, just like Movie Clip instances within a Flash movie. Continuing with the dog trick example, the first cue point could be named "dog_jump", the second cue point could be named "dog_speak", and so on. Each cue point would have a unique time as well. If dog_jump was the first cue point, it might have a time of 0 seconds (if it's at the very beginning of the clip). The dog_speak cue point might have a time of 13 seconds, because the speaking trick starts 13 seconds from the beginning of the dog trick clip.
You can also associate other data with a cue point. If you need a specific caption to display below the video display area, you can specify the text with the cue point. You might also want to associate a linkage identifier of a MovieClip graphic to be attached on the stage (on top of the video, for example) for each cue point as well.
In later installments of this series, you'll learn how to specify cue point data in ActionScript, XML, and other data formats.
When you're creating Flash Video content and playback interfaces in Flash Professional 8, you have more than one option to deploy the content with cue points enabled. There are two general classifications for cue points: external or embedded.
Since Flash Player 6 introduced the capability to use Flash Video, you have had the capability to create cue point data that resided outside of the actual Flash Video clip (SWF or FLV file). If you're not using the Media components that ship with Flash MX Pro 2004 or Flash Pro 8, you need to create your own tracking system that monitors playback of the video content and fires an event whenever a cue point's time has been reached. If you are using the Media components, you can use the addCuePoint() method of the MediaPlayback or MediaDisplay component to specify cue point data. If you're using the new FLVPlayback component that ships with Flash Pro 8, you can use the addASCuePoint() method to specify cue points.
External cue point data can be declared as arrays of objects within your ActionScript code, or you can create an XML document with your own custom cue point schema to load and parse within your ActionScript code. The benefit to using external cue point data is that you can easily adjust the information associated with each cue point throughout the production process. So, if you need to adjust the timing of a cue point, you can just edit your ActionScript code or XML data and you're able to view the presentation with the updated information. However, the drawback to using external cue point data is that the time of each cue point is not necessary linked to a keyframe in the Flash Video file. You'll learn why this is important in the next section.
Tip: With respect to the FLVPlayback component, any cue point that is not embedded within the FLV file is referred to as an ActionScript cue point.
Starting with Flash Professional 8, you can now add cue point data directly into the Flash Video file (.flv). Using the Video Import wizard or the new Flash 8 Video Encoder application, you can specify cue points during the encoding process. While the user interface for adding cue points is somewhat awkward, you have the capability to scrub to specific frames within the source video clip and add customized data to each cue point. When you are done typing your cue point information, you can proceed to encode the FLV file just as you would any other Flash Video file. There are two types of embedded cue points in the Flash 8 Video Encoder application, both of which are automatically recognized by the new FLVPlayback component:
If you have encoded an FLV file to use embedded cue points, you can capture the cue point data by using the new NetStream.onCuePoint() handler available in Flash Player 8. You can also detect embedded or external cue point events using the "cuePoint" event name with the FLVPlayback component. The "cuePoint" event can be registered with the FLVPlayback.addEventListener() method. Embedded cue point data is also contained with the cuePoints property (as an array) of the metadata object returned to the NetStream.onMetaData() method.
Note: Buraks Captionate can now also add embedded cue points to an FLV file. We'll discuss this utility in a later installment.
You now have the information you need to begin building Flash Video files that work with cue points to enhance the playback experience. In the next installment of this series, you learn how to added embedded navigation cue points to a video clip controlled by the FLVPlayback component.
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Keywords
Flash 8 Video, FLV, Embedded cue points
