An applet is not a stand-alone program -- it's a simple program that works within a larger application. Most applets use only a small amount of memory, have limited features and can work on most operating systems. Flash applets use Web browsers to create a user interface through which a viewer can decode and play Flash files.
YouTube videos are all in Adobe Flash Video format, which has the file extension designation of .flv. You've probably encountered several different video formats on the Internet, each with its own dedicated video player. These include:
- QuickTime, from Apple, plays files that end in .mov
- RealNetworks RealMedia plays .rm files
- Microsoft Windows Media can play a few streaming file types: Windows Media Audio (.wma), Windows Media Video (.wmv) and Advanced Streaming Format (.asf)
- Adobe Flash player plays .flv files and .swf animation files
Flash Video has two big advantages over other formats. First, it has high compression ratios, which means .flv files tend to be smaller than other formats. Second, Flash Video requires a flash player applet rather than a stand-alone video player.
Creating a Flash applet is a fairly simple coding task -- there are several Web pages that can guide you through the entire process. YouTube's Flash player has the standard bells and whistles, including volume control, play, rewind and a couple of buttons that allow the viewer to minimize or maximize the viewing screen.
In order to view YouTube videos, users must have Macromedia Flash Player 7.0 or higher installed on their computers. Since the player is free, there's no cost to the user to get his or her computer up to speed. YouTube's player only works with .flv files, but fortunately users don't have to create or convert files into that format before sending them in.
YouTube accepts video files in Quicktime (.mov), Windows Media Video (.wmv), Audio Visual Interleave (.avi) and Moving Pictures Expert Group (.mgp) formats. Users upload video files in one of these formats and YouTube converts them into .flv. YouTube calls the period between uploading a file and the completion of conversion processing time, which varies depending on the size and format of the original file. YouTube says that processing time might only take a few minutes or could require several hours. If a video takes longer than eight hours to upload, YouTube suggests that the video's creator remove the video and try uploading it again.
In the next section, we'll take a look at YouTube's layout.