MACROMEDIA FLASH 8-DEVELOPING FLASH LITE 2.X Manual de usuario descargar pdf (Pagina 14)

Adobe Flash CS3 Classroom in a Book

Strive for simplicity

Avoid elaborate transitions—they don’t compress

well and can make your ﬁnal compressed video look

“chunky” during the change. Hard cuts (as opposed to

dissolves) are usually best. Eye-catching video sequenc-

es—for instance showing an object zooming from

behind the ﬁrst track, doing a “page peel,” or wrapping

around a ball and then ﬂying off the screen—don’t

compress well and should be used sparingly.

Know your audience data rate

When you deliver video over the Internet, produce ﬁles

at lower data rates. Users with fast Internet connections

can view the ﬁles with little or no delay for loading, but

dial-up users must wait for ﬁles to download. Make the

clips short to keep the download times within accept-

able limits for dial-up users.

Select the proper frame rate

Frame rate indicates frames per second (fps). If you

have a higher data rate clip, a lower frame rate can

improve playback through limited bandwidth. For ex-

ample, if you are compressing a clip with little motion,

cutting the frame rate in half probably saves you only

20% of the data rate. However, if you are compressing

high-motion video, reducing the frame rate has a much

greater effect on the data rate.

Because video looks much better at native frame rates,

leave the frame rate high if your delivery channels and

playback platforms allow. For web delivery, get this

detail from your hosting service. For mobile devices,

use the device-speciﬁc encoding presets, and Device

Central. If you need to reduce the frame rate, the best

results come from dividing the frame rate by whole

numbers.

Note: When you embed video clips in the SWF ﬁle,

the frame rate of the video clip must be the same as

the frame rate of the SWF ﬁle. To encode video using

the frame rate of the FLA ﬁle, use the Advanced Video

Encoding settings in the Flash Video Import wizard.

Select a frame size that ﬁts your data rate and frame

aspect ratio

At a given data rate (connection speed), increasing the

frame size decreases video quality. When you select the

frame size for your encoding settings, consider frame

rate, source material, and personal preferences. To pre

vent pillarboxing, it’s important to choose a frame size

of the same aspect ratio as that of your source footage.

For example, you get pillarboxing if you encode NTSC

footage to a PAL frame size.

Adobe Premiere Pro makes several Adobe Flash Video

presets available through Adobe Media Encoder. These

include preset frame sizes and frame rates for the dif-

ferent television standards at different data rates. Use

the following list of common frame sizes (in pixels) as

a guide, or experiment with the various Adobe Media

Encoder presets to ﬁnd the best setting for your project.

Stream for best performance

To eliminate download time, provide deep interactiv-

ity and navigation capabilities, or monitor quality of

service, stream Adobe Flash Video ﬁles with the Flash

Media Server or use the hosted service from one of

Adobe’s Flash Video Streaming Service partners avail-

able through the Adobe website.

Know progressive download times

Know how long it will take to download enough of

your video so that it can play to the end without paus-

ing to ﬁnish downloading. While the ﬁrst part of your

video clip downloads, you may want to display other

content that disguises the download. For short clips,

use the following formula: Pause = download time –

play time + 10% of play time. For example, if your clip

is 30 seconds long and it takes one minute to down-

load, give your clip a 33-second buffer (60 seconds – 30

seconds + 3 seconds = 33 seconds).

Remove noise and interlacing

For the best encoding, you might need to remove noise

and interlacing. The higher the quality of the original,

the better the ﬁnal result. Although frame rates and

sizes of Internet video are usually smaller than those of

television, computer monitors have much better color

ﬁdelity, saturation, sharpness, and resolution than

conventional televisions. Even with a small window,

image quality can be more important for digital video

than for standard analog television. Artifacts and noise

that are barely noticeable on TV can be obvious on a

computer screen.

Adobe Flash is intended for progressive display on

computer screens and other devices, rather than on

LESSON 9

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