Chapter 18. Working with Video

Flash Player 8 can deliver better video quality than Flash Players 6 and 7 could. With the new On2 VP6 codec that is part of the Flash Player 8 plug-in, you can encode your video content to display better detail, better color, and smoother motion. You still have the option to use the Sorenson Spark codec with any Flash Player 6, 7, or 8 content, and you'll learn later in this chapter how to choose the appropriate codec for your Flash production.

Regardless of how you deploy web-based video, there are a few principles of video that you should understand. Most video files, even after heavy compression, are substantially larger than other files loaded into a web browser, such as HTML, XML, CSS, or other Flash content. One of the most critical factors of a video file is its bit rate, also referred to as a data rate. The data rate of a video file determines how much data (in bits or kilobits per second) is required to sustain smooth playback of the video. Every computer or device connected to the Internet has a connection speed, or available bandwidth, which determines how fast content over the Web can load and display in a browser.

The data rate of any given Flash Video file is fixed, and can be allocated across a variety of video properties, including frame rate (how smooth the motion appears within the content), frame size (how large the video displays on the screen), and quality (how much compression is applied to each frame of video). You can use the data rate of a video file to favor any one of these properties, depending on your content. For example, a video clip of a person delivering a lecture could afford to use a slower frame rate, and a clip of cars racing could use a higher frame to retain the smoothness of motion. A clip with a slower frame rate could use the remaining data rate for a higher quality image (or less compression) or a larger frame size.

In addition to data rate, video content can also be buffered in the playback environment. Buffering is the process of storing a specific amount (in units of time) of video in the player before playback can begin or resume. You can set the buffer time for video playback with the Flash Player, using ActionScript or parameters of video components.

With these factors in mind, you should plan how you want the user to experience the playback of the file:

• Does everyone get the same video file, regardless of his or her connection speed to your server?

• Will each user need to wait for the entire clip to download before playback, or will you use a specific buffer time to enable the video to begin playback sooner?

• If you offer several data rates for the same video content (that is, you create two or more Flash Video files, each with a unique data rate), can the user choose which one to play or do you script your Flash movie to pick the best clip for that user's available bandwidth? Does each clip have the same frame size or will the user interface layout change depending on which clip is played?

The answers to these questions are largely up to you. In order to make the right decisions, you need to know more about the specifics of Flash Video. This chapter helps you better understand how to encode, deploy, and optimize your Flash Video (FLV) content. You also learn how to create embedded cue points, a capability found within the Flash 8 Video Encoder that ships with Flash Professional 8. It is possible to embed video content into a Flash file directly. However, progressive and streaming FLV are preferable in nearly all cases, and therefore this chapter discusses FLV solutions only.