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How you compress your video is largely determined by the content of the video. A video clip of a talking head with very little action and only short bursts of moderate motion compresses very differently than footage of a soccer match does. Following are some tips on delivering the best possible Flash video:
Strive for simplicity Avoid elaborate transitions—they don't compress well and may make your final compressed video look "chunky" during the change. Hard cuts are usually best, or quick cross-fades. Video sequences that show an object zooming from behind the first track, doing a "page turn," or wrapping around a ball and then flying off the screen may be eye-catching, but they usually don't compress well and should be used sparingly.
Know your audience data rate When you deliver video over the Internet, you should produce files at lower data rates. Users with fast Internet connections can view the files with little or no wait, but dialup users have to wait for the files to download. It is best to make the clips short to keep the download times within acceptable limits for dialup users.
Select the proper frame rate Frame rate indicates how many frames are played each second. If you have a higher data rate clip, a lower frame rate can improve playback on lower-end computers. For example, if you are compressing a talking head clip with little motion, cutting the frame rate in half will probably save you only 20% of the data rate. However, if you are compressing high-motion video, reducing the frame rate has a much greater effect on the data rate.
Because video looks much better at native frame rates, Macromedia recommends leaving it high if your delivery channels and playback platforms allow. However, if you need to reduce the frame rate, the best results come from dividing the frame rate by whole numbers.
Select a frame size that fits your data rate Like the frame rate, the frame size for your document is important for producing high-quality video. At a given data rate (connection speed), increasing the frame size results in decreased video quality. When you select the frame size for your document, you must also consider frame rate, source material, and personal preferences. The following list of common frame sizes should be used as a guideline. Experiment to find the best setting for your project.
Modem: 160 x 120
Dual ISDN: 192 x 144
T1/DSL/cable: 320 x 240
Know progressive download You should know how long it is going to take to download your video. While your video clip is downloading, you might want to have other content that appears and "disguises" the download. For short clips you can use the following formula: Pause = download time - play time + 10% of play time. For example, If your clip is 30 seconds long and it takes one minute to download, you should give your clip a 33-second buffer: 60 seconds - 30 seconds + 3 seconds = 33 seconds.
Use clean video The higher the quality of the original, the better the final result. Although frame rates and sizes of Internet video are usually smaller than those of television, computer monitors have much better color fidelity, saturation, sharpness, and resolution than conventional televisions. Even with a small window, image quality can be more important for digital video than for standard analog television. Artifacts and noise that would hardly be noticeable on TV can be painfully obvious on a computer.
Remove noise and interlace After you capture your video content, you might need to remove noise and interlace.
Follow the same guidelines for audio The same considerations exist for audio production as for video production. To achieve good audio compression, you must begin with clean audio. If you are encoding material from a CD, try to record the file using direct digital transfer instead of through the analog input of your sound card. The sound card introduces an unnecessary digital-to-analog and analog-to-digital conversion that can create noise in your source audio. Direct digital transfer tools are available for both Windows and Macintosh platforms. If you must record from an analog source, be sure to use the highest quality sound card available.
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