Flash Video: Progressively downloading Videos

Progressive downloading lets you use ActionScript to load external FLV files into a SWF file, and play them back at runtime. More specifically, you can use the netConnection and netStream objects to initiate playback of the FLV file, and to control the Play, Pause, and Seek behaviors, as well as the buffer time and size for a given video file.

Intergrated, external FLV file

Because the video content is kept external to the other Flash content and the video playback controls, it's relatively easy to update video content without republishing the SWF file.

Progressive downloading

• During authoring, you need to publish only the SWF interface for previewing or testing part or all of your Flash content. This results in faster preview times and quicker turnaround on iterative experimentation.
• During delivery, video begins playing as soon as the first segment has been downloaded and cached to the local computer's disk drive.
• At runtime, video files are loaded from the computer's disk drive into the SWF file, with no limitation on file size or duration. There are no audio synchronization issues or memory restrictions.
• The frame rate of the video file can be different from the frame rate of the SWF file, allowing for greater flexibility in authoring a movie.

Flash Video: Embedding video in a SWF file

Embedded video lets you embed a video file within a SWF file. When you import video in this way, the video is placed in the Timeline where you can see the individual video frames represented in the Timeline frames. As with an imported bitmap or vector artwork file, an embedded video file becomes part of the Flash document.

When you create a SWF file with embedded video, the frame rate of the video clip and the SWF file must be the same. If you use different frame rates for the SWF and the embedded movie clip, playback will be inconsistent. If you need to use variable frame rates, import the video using either progressive download or Flash Communication Server as your delivery options. When you import movies using either of these methods, the FLV files are self-contained and run at a frame rate separate from that of all other Timeline frame rates included in the Flash movie.

You can import video clips into Flash as embedded files in QuickTime video (MOV), Audio Video Interleaved file (AVI), Motion Picture Experts Group file (MPEG), or other formats, depending on your system.

Embedded video works best for smaller video clips, with a playback time of less than 10 seconds. If you are using video clips with longer playback times, consider using progressively downloaded video, or streaming video using Flash Communication Server.

The limitations of embedded video include:

• When embedding video files, you might encounter problems if the resulting SWF files get excessively large. Flash Player reserves a lot of memory when downloading and attempting to play large SWF files with embedded video, and this can in fact cause Flash Player to fail.
• Longer video files (over 10 seconds in length) often have synchronization issues between the video and audio portions of a video clip. Over time, the audio track begins playing out of sequence with the video, causing a less than desirable viewing experience.
• To play a video embedded in a SWF file, the entire movie must be downloaded before the video will start to play. If you embed an excessively large video clip, it may take a long time for the SWF file to download in its entirety and for playback to start.

Flash Video: Linked QuickTime video

Using Flash, you can create QuickTime movies (MOV files) that can be played back by users who have the QuickTime plug-in installed on their computers. This is often done when people use Flash to create title sequences or animation for use as video content. The published QuickTime file can be distributed as a DVD, or incorporated into other applications such as Macromedia Director or Adobe Premiere.

When using Flash to create a QuickTime video clip, you can link to a QuickTime video from the Flash file rather than embed the video in the Flash file. A linked QuickTime video imported into Flash does not become part of the Flash file. Instead, Flash maintains a pointer to the source file.

If you are creating a QuickTime video using Flash, your publish setting must be set to Flash 3, 4, or 5. You cannot display a linked QuickTime video in SWF format. The QuickTime file contains a Flash track, but the linked video clip remains in QuickTime format.

Supported file formats for video

If you have QuickTime 7 for Apple Macintosh, QuickTime 6.5 for Windows, or DirectX 9 or later (Windows only) installed on your system, you can import video clips in several file formats, including MOV, AVI, and MPG/MPEG. You can import linked video clips in MOV format.

Flash documents with embedded video can be published as SWF files. Flash documents with linked video must be published in QuickTime format.

The following video file formats are supported for importing embedded video if QuickTime 7 is installed:

The following video file formats are supported for importing embedded video if DirectX 9 or later is installed (Windows only):

By default, Flash imports and exports video using the On2 VP 6 codec. A codec is a compression/decompression algorithm that controls how multimedia files are compressed during encoding, and decompressed during playback.

If you attempt to import a file format that is not supported on your system, a warning message is displayed indicating that the operation cannot be completed. In some cases, Flash might import the video but not the audio in a file. For example, audio is not supported in MPG/MPEG files imported with QuickTime 7 on the Macintosh. In such cases, Flash displays a warning indicating that the audio portion of the file cannot be imported. You can still import the video without sound.

Audio support for MPEG video

Because MPEG encodes both the video and audio portions of a file into a single track, encoding MPEG files as FLV files may result in the audio portion being removed (or "dropped"). This occurs primarily when encoding video files into FLV format on the Macintosh platform. On the Macintosh, MPEG video is imported using QuickTime. QuickTime does not support extracting audio content from MPEG files (although QuickTime will correctly play back an MPEG file with audio programming).

If you are encoding MPEG video with audio on a Macintosh, it is recommended that you first convert the MPEG video clip into another format that encodes audio and video as separate tracks within the file. You can then encode the other format as an FLV file, and preserve the audio content.

Another alternative is to use a computer with the Windows operating system. Windows imports MPEG video using DirectShow, which supports extracting both the video and audio tracks of an MPEG file. This lets you convert MPEG video to the FLV format without removing the audio portion of the video clip.

Importing video using the Video Import wizard

The Video Import wizard provides a streamlined interface for importing video into a Flash document. The wizard lets you select whether to import a video clip as a streamed, progressively downloaded, embedded, or linked file. Also, depending on the location of your file, the Video Import wizard provides a series of options for different deployments.

If the video clip you wish to import is located on your local computer, you can browse to it and import the video. You can also import a video stored on a remote web server or Flash Communication Server by providing the URL of the file.