Streaming versus Event Sounds

Sounds in Flash can be either streaming sounds or event sounds. When you stream a sound, you lock it to the timeline. That means that the sound plays frame-by-frame and forces any animations to keep up with it. If the animation can't render fast enough, frames of the animation are skipped . The downside of this is that your presentation can get jumpy. The upside is that you can use streaming to synchronize your animation and sound. A general rule of thumb to keep in mind is this: If you're going to stream your sound, keep your animation simple.

Streaming sounds begin to play as soon as enough frames of the sound have down-loaded. If a streamed sound is longer than the timeline it's in, the sound is cut off. In terms of behavior in the timeline, streamed sounds are like graphic symbols ”they are tied to the timeline.

Event sounds are more like movie clips. They're independent of the timeline in which they exist. They can play continuously, regardless of the length of the timeline. Event sounds don't begin to play until the entire sound is downloaded. Therefore, unless you are going to preload your sounds, event sounds are best for buttons , short sounds, and "ear candy " in your movie. Event sounds can be looped without affecting the final file size .

After you import an event sound into Flash, you can use it over and over again without increasing your file size. You don't get that benefit with streamed sounds. When you set a sound to stream, Flash breaks up that sound into a series of frames, forcing it to play at a constant pace. If you loop a streamed sound, Flash adds additional frames to the timeline, increasing your file size.

If you're working with animations that have specific sounds triggered by specific events, you're in luck. You can use event sounds keyed to a specific keyframe of the animation. It's when you're trying to synchronize animation to a continuous audio track that things become more difficult. They are more difficult because your sounds and animations won't necessarily play back at the same rate.

Streaming is the only way you can effectively synchronize long-playing sounds and animation in Flash. Thus, the question becomes this: "How do you deliver the smallest possible file size and still have the ability to synchronize it with animation?" The answer is that you have to get creative. There are a couple of neat tricks you can use to get the results you want.

Tip

In general, you don't want to loop a streamed sound. If a streamed sound is set to loop, additional frames are added to the final movie and the file size increases according to the number of frames added for the looped sound.

Flash is not particularly good at delivering long audio presentations. Sound is by its very nature data- intensive and the file sizes quickly get out of hand. What you can do in Flash is use short event sounds that loop. After the sound is downloaded, it can be used as many times as you need it. Looping doesn't have to be boring. If you get creative, you can use Flash to mix your sounds and create an interesting audio track.