Tài liệu Flash After Effects- P2 pdf

36 Chapter 1: Getting Started in After Effects

Summary

Your journey has begun. This chapter introduced you to After Effects. Each

of the four exercises discussed the steps it takes to create a typical project.

Although Flash and After Effects share a common project workflow, the two

applications differ when it comes to animation and visual effects. Throughout

the chapter comparisons were made to Flash, its workspace and workflow.

These tables summarize the key similarities and differences.

Table 1.1: After Effects and Flash Workspace

After Effects Workspace Similarities to Flash Differences from Flash

Project Panel It is similar to the Library

in Flash. It displays the

imported footage and stores

compositions.

It provides more information

about the imported footage

files within the panel itself.

A search feature allows you

to quickly locate footage

nested within folders.

Composition Panel It is similar to the Stage in

Flash. It is used to compose,

preview, and edit a project.

In addition to magnification,

there are more controls

available. The workspace

outside the Comp Window’s

image area does not render

pixels, only a bounding box.

Timeline Panel It shows the structure of

your project’s composition.

Footage layers are stacked

in a similar order. Keyframes

are displayed over time.

You can access individual

Transform properties for a

layer. Adjustment layers can

be added to effect other

layers.

Table 1.2: After Effects and Flash Project Workflow

After Effects Workflow Similarities to Flash Differences from Flash

Creating a Project The project file is similar to

a Flash file. It references

imported files and stores the

animation for publishing.

Only one project file can be

open at one time. Flash can

open multiple files at the

same time.

Importing Footage Files These imported files are used

to compose the project.

The files are NOT embedded

within the project.

Setting Keyframes Interpolation is the same as

tweening in Flash — filling

in the transitional frames

between two keyframes.

After Effects interpolates

both space and time. Bezier

handles give you more

control over a motion path.

Applying Effects Enhances items on the Stage. After Effects provides

hundreds of effects and an

unlimited number of ways

to combine them.

Rendering a Project This is similar to publishing

a file in Flash.

You have more output

options available.

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CHAPTER 2

From Flash to After Effects

Video production presents technical requirements

and limitations that can’t be ignored. This chapter

explores the world of broadcast design and offers a

basic guide to exporting Flash files to After Effects.

2 Flash to Broadcast Video .................................................. 38

2 Publishing SWF Files for After Effects............................... 45

2 Using the QuickTime Exporter...........................................51

2 Exporting ActionScript-driven Movies............................... 56

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38 Chapter 2: From Flash to After Effects

Flash to Broadcast Video

Say you have just finished the world’s greatest Flash animation and want to

watch it on TV. What do you do? Similar to the Web standards you follow

when publishing your Flash file online, there are video standards you need to

be aware of when creating a Flash file destined for video.

This chapter guides you through these technical issues surrounding broadcast

design. These include frame and pixel aspect ratio, frame rate, title safe and

action safe areas, and color management. A good place to start is at the

beginning by determining the proper frame size to use.

Setting the Stage

Before you start any Flash project, you first determine the dimensions of the

document’s Stage. In video, this is referred to as the frame aspect ratio. It is

the relationship between the width and height of an image. Standard television

has a 4:3 frame aspect ratio (Figure 2.1). Where did this ratio come from?

Figure 2.1: For every four units of width there are three units of height.

Motion pictures through the early 1950s had roughly the same aspect ratio.

This became known as Academy Standard and had an aspect ratio of 1.37:1.

Television adopted the Academy Standard to a 1.33:1 aspect ratio. This is the

recognized video standard commonly referred to as a 4:3 frame aspect ratio.

In 1953 Hollywood introduced the widescreen format for motion pictures in

an effort to pry audiences away from their television sets. Today, widescreen

film has two standardized ratios: Academy Flat (1.85:1) and Anamorphic Scope

(2.35:1). High-definition (HD) television adopted Academy Flat and has an

aspect ratio of 1.78:1. This is referred to as a 16:9 aspect ratio (Figure 2.2).

4:3 Aspect Ratio

1 234

1

2

3

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Flash to Broadcast Video 39

Figure 2.2: For every sixteen units of width there are nine units of height.

There are three popular video format standards used throughout the world.

NTSC, which stands for National Television Standards Committee, is the video

format used in the United States, Canada, Japan, and the Philippines. Phase

Alternating Line, or PAL, is the format of choice in most European countries.

France uses SECAM, which stands for Séquential Couleur Avec Memoire. All

three standard video formats use a 4:3 frame aspect ratio.

As previously mentioned, HDTV displays a 16:9 frame aspect ratio. It is a digital

television broadcasting system that provides higher resolution than the standard

video formats — NTSC, PAL, and SECAM. How does all this affect Flash and its

Stage size when Flash movies can be resolution independent?

If you use only vector art, the published Flash movie can be scaled as big or

small as you want without any loss in quality. Even though the movie size may

not be important, designing for the correct aspect ratio is. If you don’t, image

distortion will occur going from Flash to video or DVD. So what dimensions

should you set the Flash Stage to?

Square versus Non-square Pixels

Before you adjust the Stage width and height, you need to be aware of the

pixel aspect ratio. This refers to the width and height of each pixel that makes

up an image. Computer screens display square pixels. Every pixel has an aspect

ratio of 1:1. Video uses non-square rectangular pixels, actually scan lines.

To make matters even more complicated, the pixel aspect ratio is not consistent

between video formats. NTSC video uses a non-square pixel that is taller than it

16:9 Aspect Ratio

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

5

6

7

8

9

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40 Chapter 2: From Flash to After Effects

is wide. It has a pixel aspect ratio of 1:0.906. PAL is just the opposite. Its pixels

are wider than they are tall with a pixel aspect ratio of 1:1.06.

Figure 2.3: The pixel aspect ratio can produce undesirable image distortion if you do

not compensate for the difference between square and non-square pixels.

Flash only works in square pixels on your computer screen. As the Flash file

migrates to video, the pixel aspect ratio changes from square to non-square.

The end result will produce a slightly stretched image on your television screen.

On NTSC, round objects will appear flattened. PAL stretches objects making

them appear skinny. The solution is to adjust the dimensions of the Flash Stage.

A common Flash Stage size used for NTSC video is 720 x 540 which is slightly

taller than its video size of 720 x 486 (D1). For PAL, set the Stage size to

768 x 576. This is wider than its video size of 720 x 576. The published movie

can be rescaled in After Effects to fit the correct dimensions. Even though the

image may look distorted on the computer screen, it will appear correct on

video. Table 2.1 shows the correct Stage size needed for each video format.

Table 2.1: Flash Stage Size Settings for Different Video Formats

Video Format Frame Ratio Pixel Ratio Video Size Flash Stage

NTSC DV 4:3 non-square 720 x 480 720 x 534

NTSC D1 4:3 non-square 720 x 486 720 x 540

PAL DV/D1 4:3 non-square 720 x 576 768 x 576

NTSC DV 16:9 non-square 720 x 480 864 x 480

NTSC D1 16:9 non-square 720 x 486 864 x 486

PAL 16:9 non-square 720 x 576 1024 x 576

HDTV 720p 16:9 square 1280 x 720 1280 x 720

HDTV 1080i 16:9 square 1920 x 1080 1920 x 1080

There is some good news with high-definition (HD) television. HD uses square

pixels. This means that depending on the HD format you choose, either 720p

or 1080i, your Flash Stage dimensions are the same as the video size. We’ll

discuss other methods of adapting a 720 x 540 Stage size to HDTV’s wider

aspect ratio later in the chapter. Let’s focus on setting the proper frame rate.

Computer Screen

(square pixels)

NTSC DV or D1

(non-square pixels)

PAL DV or D1

(non-square pixels)

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