MACROMEDIA FLASH 8-DEVELOPING FLASH LITE 2.X Manual de usuario descargar pdf (Pagina 15)

Adobe Flash CS3 Classroom in a Book

interlaced displays such as TVs. Interlaced footage

viewed on a progressive display can exhibit alternating

vertical lines in high-motion areas. Thus, all the Adobe

Flash Video presets in the Adobe Media Encoder have

deinterlacing turned on by default.

Follow the same guidelines for audio

The same considerations apply to audio production as

to video production. To achieve good audio compres-

sion, begin with clean audio. If you are encoding mate-

rial 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 Windows and Macintosh

platforms. To record from an analog source, use the

highest-quality sound card available.

Embedding video in a SWF le

Embedded video lets you embed a video ﬁle within

a SWF ﬁle. When you import video in this way, the

video is placed in the Timeline where you can see the

individual video frames represented in the Timeline

frames. An embedded video ﬁle becomes part of the

Flash document.

When you create a SWF ﬁle with embedded video, the

frame rate of the video clip and the SWF ﬁle must be

the same. If you use different frame rates for the SWF

ﬁle and the embedded video clip, playback is incon-

sistent. To use variable frame rates, import the video

using either progressive download or Flash Media

Server. When you import video ﬁles using either of

these methods, the FLV ﬁles are self-contained and run

at a frame rate separate from that of all other timeline

frame rates included in the Flash SWF ﬁle.

You can import video clips into Flash as embedded ﬁles

in QuickTime video (MOV), Audio Video Interleaved

ﬁle (AVI), Motion Picture Experts Group ﬁle (MPEG),

or other formats, depending on your system.

Embedded video works best for smaller video clips,

with a playback time of less than 10 seconds. If you are

using video clips with longer playback times, consider

using progressively downloaded video, or streaming

video using Flash Media Server.

The limitations of embedded video include:

• You might encounter problems if the resulting SWF

ﬁles become excessively large. Flash Player reserves a lot

of memory when downloading and attempting to play

large SWF ﬁles with embedded video, which can cause

Flash Player to fail.

• Longer video ﬁles (over 10 seconds long) often have

synchronization issues between the video and audio

portions of a video clip. Over time, the audio track

begins playing out of sequence with the video, causing

a less than desirable viewing experience.

• To play a video embedded in a SWF ﬁle, the entire

video ﬁle must be downloaded before the video starts

to play. If you embed an excessively large video ﬁle, it

might take a long time for the SWF ﬁle to download in

its entirety and for playback to start.

Playing back external FLV les dynamically

An alternative to importing video into the Flash

authoring environment it to use either the FLVPlay-

back component or ActionScript to dynamically play

external FLV ﬁles in Flash Player. You can play FLV ﬁles

posted as HTTP downloads or as local media ﬁles.

Create FLV ﬁles by importing video into the Flash

authoring tool and exporting it as an FLV ﬁle. You can

use the FLV Export plug-in to export FLV ﬁles from

supported video-editing applications.

To play back an external FLV ﬁle, post an FLV ﬁle to a

URL (either an HTTP site or a local folder) and add ei-

ther the FLVPlayback component or ActionScript code

to the Flash document to access the ﬁle and control

playback during runtime.

Using external FLV ﬁles provides the following capabil-

ities that are not available when using imported video:

• You can use longer video clips without slowing down

playback. External FLV ﬁles are played using cached

memory, which means that large ﬁles are stored in

small pieces and accessed dynamically; they do not

require as much memory as embedded video ﬁles.

• An external FLV ﬁle can have a different frame rate

from the Flash document in which it plays. For ex-

ample, you can set the Flash document frame rate to 30

fps and the video frame rate to 21 fps, which gives you

greater control in ensuring smooth video playback.

LESSON 9

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