Creating Dynamic Soundtracks Using Chunks and Flash 5

Welcome to the second tutorial in our dynamic audio trilogy: Creating Dynamic Soundtracks using Chunks and Macromedia Flash. In the first tutorial, Creating Dynamic Soundtracks using Layering and Macromedia Flash, we showed you how to make your sound tracks more interesting by layering and controlling individual instrument parts using Flash 5 and DoReMedia Sound Families™. Sound Family Layers provide the "unmixed" instrument tracks necessary to accomplish this feat. But layers are just one of three dimensions of the Sound Family. The second dimension is Chunks.

What are Chunks?

Chunks are pre-mixed phrases taken out of a musical arrangement. Chunks open a whole new world of possibilities for audio interactivity in Flash, and in some ways, are more powerful and easier to work with than layers. Rather than individual instrument parts, Chunks provided with DoReMedia Sound Families are the most common song sections, such as the verse, chorus, breakdown, intro, and outro. By shuffling the order and repetitions of each chunk, you can easily tailor your own musical arrangement to the timing and visuals of your Flash project.

Why Use Chunks?

Chunks can be implemented in a few different ways. They can be implemented almost exactly the same way as layers, triggering 2 or more chunks on the same keyframe, and then using volume envelopes to mute and unmute each piece of audio to create musical dynamics. Chunks can also be used in conjunction with a "sync track", provided with every Sound Family, and inserted at various points across the timeline. Using chunks frees you from the 8 part limitation of Layers, and allows for more musical variation. Layers give you more permutations, but less dynamic range. Think of it this way: Layers put together make up a section of a song; Chunks put together make up the entire song.

As described in Tutorial 1, by using layers and volume envelopes, we can avoid the need to force frame rates (see below). But Layers can be limiting. You can only have up to 8 layers at a time (muted or unmuted). You can only have up to 8 envelopes per layer, which can become an limiting issue with longer or more complex soundtracks. And layers can be difficult to modify - if your movie structure changes, or you want to change the arrangement of your layered soundtrack, you have to progressively edit every layer's envelope many times. In these situations, Chunks can save the day.

Chunks are like sound Legos. You simply "attach" one clip to the next to construct your own musical arrangement. The nice thing about chunks and Flash is that after you use a chunk the first time, it's "free". The file is stored in cache and can be re-used later in your movie without increasing your file size. And you can associate specific pages, scenes, buttons and user actions with specific chunks, making your soundtrack truly interactive.

Forcing Flash's Frame Rate

Flash allows you to select a frame rate for your movie between 1 frame per second and 30 frames per second. The two most common rates are 12fps and 15fps, but any rate is acceptable to a tenth of a frame per second resolution. The tricky part is that no matter what frame rate you pick, actual playback is dependent on the user's processor and the complexity of the movie. So even though you may choose 12fps, your audience may only experience 10fps, or 6fps. This poses a problem when trying to synchronize audio and graphic elements in your Flash movie.

It's fairly easy to synchronize the beginning of a sound clip with an event by simply triggering the audio at the same keyframe as your event. But what if you want to synchronize something with the end of a sound clip, like another sound clip, as in our Lego example? How do you know on which keyframe to trigger your second clip? We need to know what frame the timeline is on when one chunk finishes, so we can then trigger the next chunk to build our arrangement.

In order for all of this to work, we have to force Flash to keep a precise, consistent frame rate. We could set the sound SYNC METHOD to STREAMING for all of our sounds, but this would increase our file size by a factor of 10 or more.

The answer is what DoReMedia calls a Sync Track. Every Sound Family comes with a corresponding, tempo-matched Sync track. The purpose of the Sync Track is two-fold. It forces Flash's frame rate to be constant, and it provides a very useful visual reference which can be used to avoid trial and error in placing and synchronizing sound clips.

What is a Sync Track?

A Sync Track is a one measure sound clip that is recorded at the same tempo as the Sound Family. It is a multiple in length of every component (layers and chunks) in a Sound Family. It also has an audio spike at the beginning of the clip, which provides the visual reference on your Flash timeline that corresponds to every musical measure. By inserting this low-resolution clip throughout the length of your movie soundtrack with a SYNC SETTING of STREAMING, we can force Flash's frame rate to be constant and determine when to trigger the next chunk.

Using Chunks and the Sync Track to Build a Custom SoundTrack

In the following exercise, we will create a background track using DoReMedia Sound Family chunks that will save over 50% download time versus streaming the same amount of audio:

Begin by setting your frame rate from the MODIFY>MOVIE dialog box. We will use 13 fps for this exercise because it is an optimized frame rate for the musical tempo of our soundrack (see "Dealing With Seams and Timing Inconsistencies" below). Then IMPORT your audio components and sync track into your Flash movie. In this example we will use Spankin_intro.aif, Spankin_A.aif, Spankin_B.aif, and Spankin_break.aif. ADD 6 new LAYERS and rename them to match your audio components - including your sync track: "Sync", "Intro", "A", "B", "Break", and "Outro" {figure 1}.

Next, drop your sync track onto your timeline by selecting SYNC_130.aif in the Sound pulldown menu of the SOUND PROPERTIES dialogue box. Set the SYNC METHOD to STREAMING and enter 50 in the LOOPS box {figure 2}. Click the EDIT button. Drag the volume envelop handles down to the bottom to turn the volume for this track off {figure 3}.

This is due to the precise timing of Sound Family components, and allows for seamless audio synchronization. On Frame 49 of track A, INSERT KEYFRAME and add the sound Spankin_A.aif {figure 5}. Again, make sure you are setting the SYNC METHOD to EVENT. Set the LOOP parameter to FOUR (4). {Follow this same proceedure as we add more audio tracks}

This will take us to frame 239. On frame 240 of track B, add the sound Spankin_B.aif. Set the LOOP parameter to TWO (2) for this clip {figure 6}. You should now be at frame 337. At frame 338, add the sound Spankin_break.aif on the track labeled Break, and set it's LOOP parameter to TWO (2) {figure 7}.

Now go back to track A, frame 433 and add another instance of Spankin_A.aif Set it's loop parameter to 2 {figure 8}. Finally, we are ready to wrap up our arrangement with an ending. On the one remaining unused track labeled Outro, insert Spankin_outro.aif at frame 529 {figure 9}.

Using the Sync Track's Waveform Display to Help Create Dynamics

Lets IMPORT two more components from our Sound Family called Spankin_fill_01.aif and Spankin_crash.aif. Sound Family chunks have been engineered without drum fills and cross-phrase melodies for looping purposes. Because of the uniqueness of every multimedia project, having fills and melodies as part of the chunk would be a disadvantage. But fills and melodies add impact and dynamics, right? Isn't that why traditional loops get so mundane?

The answer is, yes. Loops alone are almost the opposite of dynamic and compelling. However, using the sync track and layerable audio components like drum fills, give you the ability to add these impact building elements back into our mix... when YOU want them.

Fills provided with Sound Families are always edited to be one or two full measures in length. This means that they will always align with a waveform spike on our sync track.

ADD a new LAYER and label it "FILLS". Lets look on our timeline to find frame number 240. This is where we switch from Spankin_A to Spankin_B.Go back one spike to frame 217 and insert a new keyframe {figure 10}. Add the sound Spankin_fill_01, with a SYNC METHOD of EVENT. Not bad, but there is one more thing we need to do to really give it punch. We need a cymbal crash at the end of the fill. ADD another LAYER and label it "CRASH". On frame 240 of this track, INSERT a KEYFRAME and select the sound Spankin_crash.aif from the sound menu {figure 11}.

Repeat the same process throughout your soundtrack to suit your taste. I have put the fill and crash on some transitions, while using only the crash on others. Give it a play. You may need to adjust your volume levels so the drum fill and crash are mixed properly with your chunks.

Dealing with Seams and Timing Inconsistencies

Seams are small gaps or pauses between chunks or loops that are placed back to back. Depending on processor speed, playback quality may vary within the Flash application, causing small seams between chunks. However, if all chunks have been inserted in the correct frames, this should not be a problem upon export to SWF format.

If seams still exist in your exported movie, there are a couple of possible causes and resolutions.

The first reason you may experience seams is due to mis-matched frame rates and beats per minute. Flash's timing method is frames per second, while music is measured in beats per minute. The average ear can hear a 3 millisecond (3/1000) gap in a solid music stream. So, if your frame rate is set at 10 frames per second, and your first chunk ends in the middle of a frame, you will have a 5/100 of a second space (50/1000 or 50 millisecond) before the next chunks starts, causing a seam. This problem is solved by choosing frame rates and beat-per-minute rates that divide evenly. A simple equation to use is: Beats per minute divided by frames per second must be a whole number. For example:

To illustrate this better, go to MODIFY > MOVIE and change your frame rate to 12 FPS. Notice in the timeline that the audio waveforms no longer end precisely at the end of a frame.

All DoReMedia Sound Families are recorded at optimal BPM rates and engineered to have timing accurate to 1 millisecond.

If you are using frame-optimized sound files such as a Sound Family, and still experience timing inconsistencies upon export, there are a couple of work arounds.

• Re-export your movie. Sometimes the process of encoding MP3 files can make slight variations in the length of the audio file.

• Stagger the start of your sync track and the start of your chunks by selecting all frames and sliding them back to frame 5 or so. Then move the sync track back up to frame one {see figure 12}. This will give the sync track a little extra time to "take hold". It's best to do this just before publishing your movie so you can take advantage of the visual reference of the sync track during production.

More Tips and Tricks

• Because Chunks do not need to start on the same keyframe to stay in sync, they can be targeted more easily with mouse events and action scripting. If you create your soundtrack as a separate movie clip, you can use tell targeting to instruct your soundtrack movie to begin playing at a various keyframes, depending on user choices. This technique can make your soundtrack interactive to a whole new level.

• If a sync track is not desirable for your project, try using Chunks just like layers. Trigger them all at the same keyframe and then use volume envelopes to mute and unmute them as needed. Depending on your project requirements, you might find this method will save you time and/or file size compared with using the LAYERING method. Just remember that Chunks are pre-mixed, so they will not sound good if more than one plays at a given time.

• Chunks and Layers can be used in combination throughout a soundtrack to create endless possibilities. Layer a lead line on top of a breakdown...Mute the last bar of the A section and insert a bit of the percussion track to create a dynamic effect...Use layers to make a changing background track, and then on a mouse click, trigger sound effect along with the B section to make a stunning transition. Another benefit is that very often you might find one chunk that incorporates all the layers you want to use, significantly saving on file size.

• Just before publishing your movie, delete all of the frames on your sync track, except the first one. Technically, Flash only needs a single keyframe with a sound set to the streaming method to "kick" it into forced-frame mode. This will save you considerable file size.

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