Học Actionscript 3.0 - p 37 pdf

For example, the component will automatically determine if you’re using a streaming server by parsing the URL of the video source.. To choose a skin, save your FLA, or create a new tempo

Customizing Settings

If you’re not content with a preset, or if you have additional needs (such as

resizing the source), you can click on the Settings button to customize the

settings (You can even save your customizations as a preset of your own.)

Figure 12-4 shows the Settings interface The upper left quadrant allows you

to see various sizes of the source material, as well as crop the source prior to

encoding The bottom left quadrant allows you to create cue points that will

be embedded in the video during encoding Between those areas is the video

timeline, which you can use to preview the video and set in and out points if

you wish to compress only a portion of the video

Figure 12-4. The Settings interface of Adobe Media Encoder (CS5 pictured)

The upper right quadrant is a general settings area that allows you to choose

the file format, encoding preset, and output directory, as well as show a

sum-mary of the settings applied by the chosen preset The lower right quadrant

contains more specific settings including video and audio encoding options,

and the ability to apply a blur during encoding

For more information about Adobe Media Encoder, see the Using Adobe Media Encoder CS5 resource at http://help.adobe.com/en_US/mediaencoder/ cs/using/index.html Information about embedding cue points during

encod-ing can be found in the “Encodencod-ing and exportencod-ing” section of this resource The companion website has additional information about creating cue points—both during encoding and at runtime through ActionScript when using the FLVPlayback component

Starting the Queue

Once a preset is selected, all you need to do is press the Start Queue button Adobe Media Encoder will encode the file and save it in the location specified

in the Output File column (The default location for the output is the same directory in which the source file resides.)

Components

Components offer designers and coders alike a chance to speed up the development process by using precreated widgets Components usually combine ActionScript and assets to make it easier to achieve a specific goal Components can be dropped onto the stage like a movie clip or button sym-bol and often function with little or no intervention When effort is required, most components can be configured using the Flash Professional CS5 Properties panel or Flash Professional CS3 or CS4 Components Inspector panel

Most components can also be manipulated with ActionScript, which is what we’ll focus on in this section Before working with any component, however, Flash Professional users must place the component in the library of the FLA file that will compile to SWF Simply drag any component from the Components panel to the Library panel, or drag it to the stage and delete it immediately In this chapter, we’ll work with three different components First, we’ll add the FLVPlayback component as a prefabricated video player Next, we’ll add captioning support to the player with the FLVPlaybackCaptioning component Finally, we’ll add a Button component to satisfy a simple user interface need

Working with the FLVPlayback Component

The fastest way to add video to your ActionScript application is by using the FLVPlayback component (Figure 12.5) The component is available in two fla-vors FLVPlayback is available to Flash Professional users of version CS3 and later, and FLVPlayback 2.5 was introduced with version Flash Professional CS4 and is also available for Flex

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By default, Adobe Media Encoder will

start processing the assets in the

encod-ing queue after two minutes of idle time

This behavior can be adjusted in the

application preferences.

Figure 12-5. The FLVPlayback component simplifies adding video to projects

In addition to Flex compatibility, FLVPlayback 2.5 was designed to take

advantage of features introduced in version 3.5 of Flash Media Interactive

Server—Adobe’s streaming media and real-time communication server

software It improves performance for video on demand and live streaming

and supports live DVR functionality (pausing, rewinding, and recording live

streams) introduced in FMS 3.5

If you prefer to avoid components—perhaps because you want to design your

own player interface, or because components increase the size of your SWF

(the FLVPlayback component contributes between 50k and 65k)—we’ll show

you how to play video entirely with ActionScript shortly If you’re open to the

use of components, however, FLVPlayback has a few useful benefits

First, you can pick from several preconfigured controllers, or skins, or you

can use the component without a skin and create your own custom

control-ler This lets the component handle all the heavy lifting in the video display

area, but allows you to control playback with your own code and your own

design (We’ll show you a very simple implementation of this approach later

in the chapter.)

More importantly, the code in the FLVPlayback component takes care of

some important behind-the-scenes tasks that you would have to recreate

For example, the component will automatically determine if you’re using a

streaming server by parsing the URL of the video source If so, it will then

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You may notice in further research that Flash Media Interactive Server is typically abbreviated as FMS This is because “interactive” was added to the product’s name only in recent versions.

handle the necessary initial communication with the streaming server for you

so you don’t have to script those connections yourself

We advise starting out with the FLVPlayback component, even if you choose

to create your own controller Then you can move on to coding your own player to replace the component after you’re comfortable with the relevant classes

Scripting the component

The following example, found in the video_comp.fla source file, demonstrates the minimum code necessary to play a video

1 import fl.video.FLVPlayback ;

2

3 var vid: FLVPlayback = new FLVPlayback ();

4 vid source = "nero.flv" ;

5 addChild (vid);

Note in line 1 that the FLVPlayback class must be imported even in the time-line because it’s not part of the flash package (Most component classes are

found in the fl package and are not automatically part of the Flash Player to keep the player size small.) Line 3 types the instance variable and instantiates the component Line 4 populates the source property (telling the component which video to play), and line 5 adds the instance to the display list

Skinning the component

To add controls simply, we can use a skin that ships with the component FLVPlayback skins are external SWFs that are loaded at runtime Therefore,

to add a skin with ActionScript, you must know the path to the skin Fortunately, Flash Professional users can take advantage of the fact that Flash will move your chosen skin to the same directory as your SWF when you test your file To choose a skin, save your FLA, or create a new temporary file and save that, to the directory you’re using for your project Temporarily drag the component from your file’s library to the stage and select it Flash Professional CS5 users can then look in the Component Parameters section

of the Properties panel (shown in Figure 12-6) to customize the component Flash Professional CS3 and CS4 users will need to open the Component Inspector panel to see the same content

Next, click on the UI element next to the skin option (In Flash Professional

CS5 there’s a pencil button, while other versions show a magnifying glass button after clicking on the field.) This will open a dialog box that allows you

to preview all the available skins, collected into groups that display the con-troller under your video or over your video Flash Professional CS5 users will also see an additional grouping of new skins called Minima You can choose which functionality to include in your controller by looking at the name of the skin and previewing its appearance when displayed in the dialog box

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If you test the video_comp.fla file, you

may wonder how it can play without

any instruction to do so The component

has an autoplay property that’s set to

true by default

Figure 12-6. The Component Parameters

section of the Properties panel (CS5

pictured)

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Users of Flex Framework authoring

tools can download the component,

skins, sample files, component source,

and several additional related tools at

http://www.adobe.com/products/flash-mediaserver/tool_downloads/

For the following exercise, found in the video_comp_skin.fla source file, choose

the SkinUnderAllNoFullNoCaption skin and test your movie Don’t worry

about the fact that it won’t work After all, you didn’t select a video source

All that matters is that Flash copies the skin to the same directory in which

you published your SWF You should see SkinUnderAllNoFullNoCaption.

swf in that directory (If not, be sure you save the FLA you were using for

this task and retest.) Once you have your skin in place, you can remove the

FLVPlayback component from the stage, or discard any temporary file you

created

Once the skin is in place, all that remains is to add one or more of the

fol-lowing three lines to your existing script Line 6 specifies your skin choice,

and the optional lines 7 and 8 specify the color and alpha of the skin Now,

when you test your movie, you’ll see a skin that you can use to control video

playback

6 vid skin = "SkinUnderAllNoFullNoCaption.swf" ;

7 vid skinBackgroundColor = 0x003366;

8 vid skinBackgroundAlpha = 0.75;

If you don’t want to store the skin file in the same directory as your main

SWF (for example, if you want to store multiple skins in a directory), you can

specify another path for the skin property Also, remember that the skin you

see is an external SWF that’s loaded at runtime Therefore, just like the video

file, the skin must be deployed with your main SWF and HTML files

Full-Screen Video

One of the most entertaining Flash video features is true full-screen video—

video that occupies the entire screen, rather than a maximized browser or

player window, hiding other computer operating system interface elements

for a fully immersive experience Both the FLVPlayback component and pure

ActionScript can launch into full-screen mode, both of which we’ll cover

Before we get to implementation, however, we need to cover two preliminary

steps

The first step is to start with optimal source material for final assets This

includes the highest quality source, the largest size your interface will allow,

and careful attention during encoding Beyond those common sense

sug-gestions, you’ll probably want to experiment with such encoding options as

different bitrates and deinterlacing your content if you’re using a DV source

Deinterlacing is the process of converting the two fields of a DV source (which

are like video frames but each contain half the horizontal lines and are

dis-played twice as fast) into the frames used by the FLV format One common

artifact that is more pronounced when working with interlaced source

mate-rial is jagged lines visible along sharp edges in your videos Deinterlacing the

source during encoding significantly reduces this effect

The second step is to instruct Flash Player to allow the switch to full-screen display If you think about it for a moment, you certainly don’t want the deci-sion to switch to full-screen mode left in the hands of content creators If that were the case, every Flash advertisement would take over your screen, leaving you no control Instead, the developer must make the feature possible, and the user must be responsible for switching back and forth between normal and full-screen modes

To enable the feature, you must add the allowFullScreen parameter, with a value of true, to the file’s host HTML file One way to do this is to add this parameter manually to the object and embed tags, as seen in the following excerpt

<object>

<param name="allowFullScreen" value="true" />

<embed allowfullscreen="true" />

</object>

Flash Professional users can also use the quick and easy solution (par-ticularly handy during testing) of choosing the “Flash Only – Allow Full Screen” publishing template in the Publish Settings dialog (File→Publish Settings→HTML→Template)

After adding support for full-screen video in your HTML host file, you’re ready to enable the full-screen button in the FLVPlayback component To

do so, choose any skin that supports full screen, such as SkinUnderAll or SkinOverPlayFullscreen, to cite two examples These and other skins add the Full Screen button shown in Figure 12-7

The following change to line 6 of the previous example, found in the video_ comp_skin_full.fla source file, changes the skin to one that supports full

screen mode

6 vid skin = "SkinUnderAllNoCaption.swf" ;

Once you have a video and have supported full screen mode in your host HTML file and skin, you can test your file in a browser Full screen mode will not work when testing within Flash Professional, so Flash users can select the default Publish Preview command, File→Publish Preview→HTML Pressing the Full Screen button in the skin will switch to full-screen mode, and you can press the Escape key to return to normal mode Later in this chapter, we’ll show you how to add full-screen playback using your own ActionScript

Captions

Captions, also referred to in some contexts as subtitles, consist of text that

is displayed synchronously during video playback Captions are useful for providing alternate language tracks to bring your video to a wider audience Captions are also appreciated by the deaf and hearing impaired, as they provide

Figure 12-7. The Full Screen button used

by select FLVPlayback skins (color and

alpha may differ)

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If HTML is not available for

Flash Professional users, go to the

File→Publish Settings menu dialog and

add HTML as a publishable format.

a much needed accessible alternative for audio tracks when it comes to dialog

and descriptive audio services

Captions help satisfy requirements imposed by the United States

Rehabilitation Act of 1973, Section 508, which establishes accessibility

man-dates for content developed for government use, or financed by federal funds

Many private entities, particularly those serving the educational markets, also

require accessible content As the demand for this requirement increases,

cap-tions will play an increasingly more important role in digital video

Using the FLVPlaybackCaptioning Component

Flash supports captioning via the FLVPlaybackCaptioning component,

when used in conjunction with the FLVPlayback component Adding the

FLVPlaybackCaptioning component to the stage at authoring time, or

dynamically at runtime with ActionScript, opens the door for caption use

The simplest way to display captions is to use the FLVPlayback component

In fact, with only one FLVPlayback instance on the stage the captioning

component will automatically detect the playback component, and use its

internal text element for caption display You can also manually specify any

FLVPlayback component as the target for the captions (in case you require

more than one at any given time), or even your own target for the captions

(in the event that you want to use another text element—perhaps integrated

into your interface, rather than the video)

To use the FLVPlayback, you’ll need to choose any skin that supports

cap-tions, such as SkinUnderAll or SkinOverPlayCaption, among others These

skins feature the Captions button shown in Figure 12-8

The following edit to line 6 of the previous example, found in the video_

comp_skin_full_captions.fla source file, uses a skin that supports all skinned

features, including captions

6 vid skin = "SkinUnderAll.swf" ;

Once the FLVPlayback component is configured to display captions, we must

add the FLVPlaybackCaptioning component to the stage

The following code continues the example first by importing the component

class in line 10, and instantiating the component in line 11 Line 12 assigns the

caption file for loading at runtime (which we’ll discuss in a moment), and

line 13 adds the component to the display list

10 import fl.video.FLVPlaybackCaptioning ;

11 var cap: FLVPlaybackCaptioning = new FLVPlaybackCaptioning ();

12 cap source = "nero_timed_text.xml" ;

13 addChild (cap);

Note that we’re not placing the component at a particular location on the

stage Although it appears as a small rectangle when dragged to the stage in

Figure 12-8. The Captions button used by select FLVPlayback skins (color and alpha may differ)

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As with the FLVPlayback component, Flash Professional users must have the component in the library of their FLA

to instantiate it with ActionScript See the “Working with the FLVPlayback Component” section of this chapter for more information

authoring mode, this is merely to simplify selecting the component At run-time, it will be invisible, so its position is irrelevant

Now both components are ready to display captions, so we need to create the caption file You can create a captioned video in two ways You can embed the caption data in the video using cue points Embedding means they’ll always

be with the video, but it also means that you have to reencode the video just

to edit the text A far more flexible option is to load a caption file at runtime This approach also allows you to switch caption files dynamically—ideal for offering subtitles in multiple languages, a task we’ll look at later in the chap-ter First, however, we need to know how to format the captions

Creating Captions with Timed Text

To create a caption file to load at runtime, you need to write an XML (Extensible Markup Langauge, discussed in Chapter 14) file using the World Wide Web Consortium (W3C) Timed Text Markup Language (TTML or, familiarly, TT)—also sometimes referred to by its format name, Distribution Format Exchange Profile (DFXP) We’ll cover a portion of Timed Text features here, but you can learn more about the language by visiting the W3C page

at http://www.w3.org/AudioVideo/TT/ More importantly, you can learn about the subset of features supported by the FLVPlaybackCaptioning component from Adobe’s ActionScript 3.0 Language and Components Reference at http://

www.adobe.com/livedocs/flash/9.0/ActionScriptLangRefV3/TimedTextTags html

Several tools can create Timed Text files, including the pair listed in the adjacent note However, you can also write your own Timed Text files The example XML that follows is an edited excerpt of the nero_timed_text.xml

source file provided in this chapter’s source archive (For brevity, two cap-tions are shown and minor edits have been made to use all features from the source file.)

1 <?xml version="1.0" encoding="UTF-8"?>

2 <tt xmlns="http://www.w3.org/2006/04/ttaf1"

3 xmlns:tts="http://www.w3.org/2006/04/ttaf1#styling">

4 <head>

5 <styling>

6 <style id="1"

7 tts:textAlign="center"

8 tts:fontFamily="_sans"

9 tts:fontSize="18"

10 tts:fontWeight="bold"

11 tts:color="#FFFF00FF" />

12 <style id="2" tts:backgroundColor="#00000000" />

13 <style id="3" tts:backgroundColor="#000000FF" />

14 <style id="trans" style="1 2" />

15 <style id="opaq" style="1 3" />

16 </styling>

17 </head>

18 <body>

19 <div>

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MAGpie is a free captioning tool

devel-oped by accessibility leaders at the

National Center for Accessible Media

(NCAM) For more information, see

http://ncam.wgbh.org/invent_build/

web_multimedia/tools-guidelines/mag-pie You can find the Manitu Group’s

Captionate at http://www.captionate.

com , and Adobe’s Flash Developer

Center features a tutorial on using

Captionate with the FLVPlayback and

FLVPlaybackCaptioning components

( http://www.adobe.com/devnet/flash/

articles/video_captionate.html)

21 Nero is a Lionfish<br /> (<span tts:fontStyle="italic">

22 Pterois volitans</span>),

23 </p>

24 <p begin="00:00:09.00" dur="00:00:02.00" style="trans">

25 in his reef aquarium.

26 </p>

27 </div>

28 </body>

29 </tt>

We’ll discuss custom XML solutions in Chapter 14, but Timed Text is a

predefined format so conforming to its specification is pretty

straightfor-ward We’ll occasionally point out things that we’ll cover in greater detail in

Chapter 14, but you should feel comfortable simply editing an existing Timed

Text file until you gain a little experience with XML

Lines 1 through 3 include two default tags used to validate the file The first

tag (also called a node) is <?xml ?> and is the XML declaration tag We’ll

discuss this in Chapter 14 but, essentially, it declares the version of XML in

use and the character encoding used when writing the document

The second tag, <tt>, is the document’s root node All XML documents must

have a root node that encloses all other nodes, and we’ll discuss this further

in Chapter 14, as well Be sure to see the accompanying note describing the

use of attributes in this tag

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The ActionScript 3.0 Language and Components Reference entry “Timed Text

Tags”, found at http://www.adobe.com/livedocs/flash/9.0/ActionScriptLangRefV3/

TimedTextTags.html , specifies that all attributes of the <tt> tag are ignored

However, this is not the case if you style your captions If you omit the xmlns

attri-bute, your captions will not be styled, and if you omit the xmlns:tts attribute, the

use of the tts namespace in styles will result in errors When using styles, consider

both of these attributes required.

A <head> tag (spanning lines 4 through 17) is optional, but we recommend its

use because it makes styling your captions much easier Within it, a

<styl-ing> tag (spanning lines 5 through 16) is also optional but necessary if you

intend to create styles Styles are Cascading Style Sheet (CSS) entities for the

Timed Text document and are itemized in lines 6 through 15 You can have as

many styles as you like, but each must have a unique id attribute The style

attributes that are actually responsible for the formatting are very similar to

CSS properties, but are preceded by the tts: prefix

It’s possible to assign multiple styles directly by their alphanumeric id, but

it’s also possible to manage formatting efficiently by creating new styles

con-sisting of other styles Take a look at the styles in our example We wanted to

achieve two looks for our captions: one with a black background, for use over

light areas of video, and one with a transparent background, to allow more of

the video to show through the text

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Character encoding just maps text characters to specific codes (usually numeric), so that software responsible for parsing the text know which char-acter to use based on a given code It’s

a way of bringing platform, hardware, and software neutrality to the process

of rendering text We recommend using UTF-8, which includes a wide range of characters, such as those used in differ-ent languages around the world

For more information about character encoding, see http://en.wikipedia.org/ wiki/Character_encoding For more information about UTF-8, see http:// en.wikipedia.org/wiki/UTF-8

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Be sure to consult the “Timed Text Tags” ActionScript 3.0 Language and Components Reference resource, men-tioned earlier in this section, for a com-plete list of supported and unsupported properties Here are a few noteworthy mentions:

• fontFamily supports device fonts, as seen in our example.

• fontSize supports only the first size found; supports absolute and rela-tive sizes but not percentages.

• lineHeight , padding , and over-flow , although potentially useful for captions, are among several options that are not supported.

Style 1 consists of all styling attributes common to both treatments, which

means that the background alpha information appears in other styles Styles

2 and 3 itemize only the background color and specify transparent and

opaque, respectively The Timed Text format uses #RRGGBBAA color nota-tion, where AA is alpha However, the ActionScript components support only opaque and transparent settings All zeros will be seen as transparent, but

any value other than zero will be opaque We’ve used the opposite of zero for

alpha, FF, to remind us that this is opaque The resulting value of #000000FF

is, therefore, an opaque black background

Once you’ve created these individual styles, you can then apply more than one style at a time It’s possible to do so at the caption level by using syntax like id="1 2", but it’s also possible to create a new style the same way For example, you can create a new style combining styles 1 and 2 and, because the style names can be alphanumeric, you can give it a descriptive name We’ve done this in lines 14 and 15, specifying that trans is centered, sans-serif,

18-point, bold, yellow text on a transparent (because it uses styles 1 and 2),

and opaq shares the same font attributes but is atop an opaque background

because it uses styles 1 and 3.

A <body> tag (lines 18 through 28) is required and is used to hold all the

caption data Within the body tag, one <div> tag (lines 19 through 27) is

required, and paragraph tags <p> are required for each line of caption (lines

20 through 26)

The ActionScript documentation doesn’t say that <div> is required but nei-ther <p> nor <span> tags can appear in the <body> tag Similarly, the documen-tation says zero or more paragraph tags are supported, but we didn’t find a logical way of applying time or style attributes to individual captions without them For example, <span> tags (lines 21 and 22) are supported, but not in the <body> or <div> tags Therefore, we suggest you consider <div> and <p>

tags required

For each caption (in our case, in each <p> tag), a begin attribute is required

to set the time of the caption The attributes dur (duration) and end (the time

at which the caption should end) are optional If omitted, the caption will remain onscreen until the next caption appears Time can be specified in full clock format (HH:MM:SS.m, where m is milliseconds), partial clock format (MM:SS.m or SS.m), or offset time (with units, such as “1s” for one second) Frames are not supported as a measure of time

Now that you know how to create a Timed Text file, you can run the previous source file, video_comp_skin_full_captions.fla, (discussed in the “Captions”

section of this chapter) which makes use of the nero_timed_text.xml caption

source file

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If you’ve spent some time with Chapter

9 in this book, you may recall that the

color notation that included alpha was

specified as 0xAARRGGBB The

dif-ference between this BitmapData color

notation, and the #RRGGBBAA used

with Timed Text, can lead to confusion

If you see an unpredictable color behind

your caption text, check to see if you’ve

used the wrong format.

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In our main Timed Text example, we

used full clock format for clarity and

consistency, even when the duration

matched the time at which the next

caption appeared However, you can

simplify this by using partial clock

for-mat, and omitting any duration or end

attributes when the caption is to remain

on screen until replaced As an

illustra-tion, we have formatted our

Spanish-language example this way, which we’ll

discuss shortly.