MACROMEDIA FLASH 8-USING FLASH VIDEO ENCODER Istruzioni per il montaggio

Using Flash Video Encoder

000_FLVEncoder.book Page 1 Friday, August 12, 2005 3:50 PM

Trademarks

1 Step RoboPDF, ActiveEdit, ActiveTest, Authorware, Blue Sky Software, Blue Sky, Breeze, Breezo, Captivate, Central,

ColdFusion, Contribute, Database Explorer, Director, Dreamweaver, Fireworks, Flash, FlashCast, FlashHelp, Flash Lite,

FlashPaper, Flash Video Encoder, Flex, Flex Builder, Fontographer, FreeHand, Generator, HomeSite, JRun, MacRecorder,

Macromedia, MXML, RoboEngine, RoboHelp, RoboInfo, RoboPDF, Roundtrip, Roundtrip HTML, Shockwave, SoundEdit,

Studio MX, UltraDev, and WebHelp are either registered trademarks or trademarks of Macromedia, Inc. and may be registered in

the United States or in other jurisdictions including internationally. Other product names, logos, designs, titles, words, or phrases

mentioned within this publication may be trademarks, service marks, or trade names of Macromedia, Inc. or other entities and

may be registered in certain jurisdictions including internationally.

Third-Party Information

This guide contains links to third-party websites that are not under the control of Macromedia, and Macromedia is not

responsible for the content on any linked site. If you access a third-party website mentioned in this guide, then you do so at your

own risk. Macromedia provides these links only as a convenience, and the inclusion of the link does not imply that Macromedia

endorses or accepts any responsibility for the content on those third-party sites.

Speech compression and decompression technology licensed from Nellymoser, Inc. (www.nellymoser.com).

Sorenson™ Spark™ video compression and decompression technology licensed from

Sorenson Media, Inc.

Reserved. http://www.on2.com.

Visual SourceSafe is a registered trademark or trademark of Microsoft Corporation in the United States and/or other countries.

translated, or converted to any electronic or machine-readable form in whole or in part without written approval from

Macromedia, Inc. Notwithstanding the foregoing, the owner or authorized user of a valid copy of the software with which

this manual was provided may print out one copy of this manual from an electronic version of this manual for the sole

purpose of such owner or authorized user learning to use such software, provided that no part of this manual may be

printed out, reproduced, distributed, resold, or transmitted for any other purposes, including, without limitation,

commercial purposes, such as selling copies of this documentation or providing paid-for support services.

Acknowledgments

Project Management: Sheila McGinn

Writing: Chris Bedford

Managing Editor: Rosana Francescato

Lead Editor: Lisa Stanziano

Editing: Lisa Stanziano, Anne Szabla

Production Management: Patrice O’Neill, Kristin Conradi, Yuko Yagi

Media Design and Production: Adam Barnett, Aaron Begley, Paul Benkman. John Francis, Geeta Karmarkar, Masayo Noda,

Paul Rangel, Arena Reed, Mario Reynoso

Special thanks to Jody Bleyle, Mary Burger, Lisa Friendly, Stephanie Gowin, Bonnie Loo, Mary Ann Walsh, Erick Vera, the beta

testers, and the entire Flash and Flash Player engineering and QA teams.

First Edition: September 2005

Macromedia, Inc.

601 Townsend St.

San Francisco, CA 94103

000_FLVEncoder.book Page 2 Friday, August 12, 2005 3:50 PM

Contents

Using Flash Video Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

About Flash Video and Flash Video Encoder . . . . . . . . . . . . . . . . . . . . . . 6

About Flash Video Exporter (QuickTime Export plug-in) . . . . . . . . . . . . 6

Supported video compression codecs for Flash Video . . . . . . . . . . . . . . 7

Comparing the On2 VP6 and Sorenson Spark video codecs . . . . . . 8

Understanding video standards and terminology . . . . . . . . . . . . . . . . . . . 8

Frame rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Data rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Keyframes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Aspect ratios (frame size) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

About encoding audio-only files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

About cue points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Encoding video with Flash Video Encoder . . . . . . . . . . . . . . . . . . . . . . . . 14

Saving the encoding queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Removing files from the encoding queue . . . . . . . . . . . . . . . . . . . . . . . 16

Skipping a file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Stopping the encoding of the current file . . . . . . . . . . . . . . . . . . . . . . . 17

Selecting advanced video encoding settings. . . . . . . . . . . . . . . . . . . . . . 17

Specifying advanced video encoding settings . . . . . . . . . . . . . . . . . . 18

Specifying advanced audio encoding settings . . . . . . . . . . . . . . . . . . 21

Defining and embedding cue points . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Cropping and trimming video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Setting Flash Video Encoder preferences . . . . . . . . . . . . . . . . . . . . . . . 26

Viewing the Flash Video Encoder log file . . . . . . . . . . . . . . . . . . . . . . . . .27

Troubleshooting video encoding errors. . . . . . . . . . . . . . . . . . . . . . . . . . 28

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

000_FLVEncoder.book Page 3 Friday, August 12, 2005 3:50 PM

4Contents

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Using Flash Video Encoder

Macromedia Flash 8 Video Encoder is a stand-alone video encoding application that lets you

encode video in Macromedia Flash Video (FLV) format. The FLV format lets you easily

incorporate video into a web page or Flash document in a format that almost anyone can view

using the Flash Player. The ubiquity of Flash Player ensures that most visitors to your website

can view Flash Video without downloading additional plug-ins, so you can reach the largest

possible Internet viewing audience with low development, testing, and support costs.

Flash Video Encoder comes with Macromedia Flash Professional 8 or Macromedia Studio 8.

This chapter contains the following topics:

About Flash Video and Flash Video Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Supported video compression codecs for Flash Video . . . . . . . . . . . . . . . . . . . . . . . . . 7

Understanding video standards and terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

About encoding audio-only files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

About cue points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Encoding video with Flash Video Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Selecting advanced video encoding settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Setting Flash Video Encoder preferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Viewing the Flash Video Encoder log file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Troubleshooting video encoding errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

000_FLVEncoder.book Page 5 Friday, August 12, 2005 3:50 PM

6 Using Flash Video Encoder

About Flash Video and Flash Video

Encoder

Flash Video offers technological and creative benefits that let you create rich, immersive

experiences that combine video presentations with data, graphics, sound, and interactive

control.

Flash Video provides full creative control and integrates easily into your website. You can use

video skins (graphic themes) to customize video presentations, incorporate your organization’s

branding, and design unique controls that let visitors to your website interact with video

content.

Flash treats Flash Video simply as a media type, so you can layer, script, and control video like

any other object in a Flash SWF file. Flash Video is an integral part of the viewing experience,

not a separate pop-up window that plays video externally and interrupts the experience.

Flash Video Encoder lets you encode video files in either the On2 VP6 or Sorenson Spark

video codecs. A codec is an algorithm that controls how video files are compressed during

import and and decompressed during playback. You can use Flash Video Encoder on a

computer that does not have Flash or other Macromedia Studio products installed. This

configuration lets you continue working with Flash, Dreamweaver, or another application

because video encoding is a processor-intensive activity that often prevents you from

simultaneously working in other applications.

Using Flash Video Encoder on a dedicated computer for video encoding lets you batch-

process multiple video clips; in environments where video is a significant form of content,

batch processing produces an expedited workflow. You can add, reorder, and change the

encoding settings of files in the batch processing queue while Flash Video Encoder is

encoding video files.

About Flash Video Exporter (QuickTime

Export plug-in)

If you have Macromedia Flash Professional 8 and QuickTime 6.1.1 or later installed on your

computer, you can use the Macromedia Flash Video Exporter (QuickTime Export plug-in) to

export FLV files from supported video-editing applications. You can then import these FLV

files directly into Flash to use in your Flash documents. The QuickTime Export plug-in is

installed by the Flash 8 Video Encoder installer.

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Supported video compression codecs for Flash Video 7

The following video-editing applications are supported by the QuickTime Export plug-in:

■Adobe After Effects (Windows and Macintosh)

■Apple FinalCut Pro (Macintosh)

■Apple QuickTime Pro (Windows and Macintosh)

■Avid Xpress DV (Windows and Macintosh)

Exporting FLV files from either Flash 8 Video Encoder or video-editing applications using the

QuickTime Export plug-in significantly streamlines the workflow in using FLV files in your

Flash documents. With the QuickTime Export plug-in, you can select encoding options for

video and audio content as you export, including frame rate, bit rate, quality, and other

options. You can import FLV files directly into Flash without needing to re-encode the video

after you import them.

Supported video compression codecs for

Flash Video

By default, Flash Video Encoder encodes video using the On2 VP6 codec for use with Flash

Player 8 and the Sorenson Spark codec for use with Flash Player 7. To understand how Flash

achieves high-quality video with low bandwidth requirements, you should understand video

compression.

There are two types of compression that can be applied to digital media: spatial and temporal.

Spatial compression is applied to a single frame of data, independent of any surrounding

frames. Spatial compression can be lossless (in which no data is discarded from the image) or

lossy (in which data is selectively discarded). A spatially compressed frame is often called an

intraframe.

Temporal compression identifies the differences between frames and stores only those

differences, so that frames are described based on their difference from the preceding frame.

Unchanged areas are simply repeated from the previous frame(s). A temporally compressed

frame is often called an interframe.

Both the On2 VP6 and Sorenson Spark are interframe codecs. Although many other codecs

use intraframe compression (for example, JPEG is an intraframe codec), the efficient

interframe compression of the On2 VP6 and Sorenson Spark codecs, among other features,

distinguishes them from other compression technologies because these codecs require a much

lower data rate (also known as the bit rate) to produce high-quality video.

NOTE

Avid Xpress DV does not support the encoding of an alpha channel when you use it

to export to the FLV video format.

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8 Using Flash Video Encoder

It’s important to note that interframe codecs also use intraframes. Intraframes are used as the

reference frames (keyframes) for the interframes. Both the On2 VP6 and Sorenson Spark

codecs always begin with a keyframe. Each keyframe becomes the main reference frame for

the following interframes. Whenever the next frame is significantly different from the

previous frame, the codec compresses a new keyframe.

Comparing the On2 VP6 and Sorenson Spark video

codecs

The On2 VP6 codec is the default video codec to use when encoding FLV content for use

with Flash Player 8. Using the On2 VP6 codec provides the following advantages when

compared to the Sorenson Spark codec:

■Encodes higher quality video at the same data rate

■Supports the use of an alpha channel to create composite video

In order to support better quality video at the same data rate, the On2 VP6 codec is

noticeably slower to encode, and requires more processor power on the client computer to

decode and play back the video data. For this reason, you should consider the lowest common

denominator of computer that your audience will use when they access your Flash video

content.

If you anticipate a large user base that is using older computers, it may be advisable to

consider encoding your FLV files using the Sorenson Spark codec.

Understanding video standards and

terminology

The following section introduces digital video concepts and terminology you should know

when working with video content. If you are new to digital video or want to learn more about

digital video and encoding high-quality video content, this section can help you understand

the trade-offs related to encoding video for different applications and Internet viewing

environments.

000_FLVEncoder.book Page 8 Friday, August 12, 2005 3:50 PM

Understanding video standards and terminology 9

Frame rates

Video is a sequence of images that appear on the screen in rapid succession, giving the illusion

of motion. The number of frames that appear every second is known as the frame rate, and it

is measured in frames per second (fps). The higher the frame rate, the more frames per second

are used to display the sequence of images, resulting in smoother motion. The trade-off for

higher quality, however, is that higher frame rates require a larger amount of data to display

the video, which uses more bandwidth.

When working with digitally compressed video in a format such as Flash Video, the higher

the frame rate, the larger the file size. To reduce the file size, you must lower either the frame

rate or the data rate (for more information, see “Data rates” on page 10). If you lower the data

rate and leave the frame rate unchanged, the image quality is reduced. If you lower the frame

rate and leave the data rate unchanged, the video motion may look less smooth than desired.

Because video looks much better at native frame rates (the frame rate at which the video was

originally filmed), Macromedia recommends leaving the frame rate high if your delivery

channels and playback platforms allow it. For full-motion NTSC, (the standard defined by

the National Television System Committee in the U.S.), use 29.97 fps; for PAL (Phase

Alternating Line, the dominant television standard in Europe), use 25 fps. If you lower the

frame rate (which can significantly reduce the video data that must be encoded), Flash Video

Encoder drops frames at a linear rate to achieve the new fps rate. However, if you need to

reduce the frame rate, the best results come from dividing evenly. For example, if your source

has a frame rate of 24 fps, then reduce the frame rate to 12 fps, 8 fps, 6 fps, 4 fps, 3 fps, or 2

fps. If the source frame rate is 30 fps, in most cases you can adjust the frame rate to 15 fps, 10

fps, 6 fps, and so on.

If your video clip is encoded with a higher data rate, a lower frame rate can improve playback

on lower-end computers. For example, if you are compressing a talking-head clip with little

motion, cutting the frame rate in half might save only 20 percent 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.

NOTE

If a video clip is longer than 10 minutes, the audio will drift noticeably out of sync if you do

not adhere to the 29.97 fps rate or an accurate even division for lower frame rates (such

as 14.98 fps, which is half of 29.97).

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10 Using Flash Video Encoder

Data rates

The data rate affects the quality of a video clip and the audience that can download the file

given their bandwidth constraints.

When you deliver video using the Internet, you should produce files using lower data rates.

Users with fast Internet connections can view the files with little or no delay, but dial-up users

must wait for files to download. If you anticipate an audience of dial-up users, you should

make short video clips to keep the download times within acceptable limits.

Flash Video Encoder lets you specify data rate settings for encoding video at a low, medium,

or high quality. If the available settings in the Quality pop-up menu do not produce the

desired results with your particular source footage, select Custom, and enter a higher data rate

in the Maximum Data Rate text box.

Keyframes

Keyframes are complete video frames (or images) that are inserted at consistent intervals in a

video clip. The frames between the keyframes contain information on movement and scene

changes that occurs between keyframes. For example, if a video depicts a person walking past

a doorway, the keyframes contain the complete image of the person and the door in the

background, and the interval frames contain information describing the person’s movement as

they walk in front of the door.

By default, Flash Video Encoder automatically determines the keyframe interval to use based

on the video clip’s frame rate. The keyframe interval value tells the encoder how often to re-

evaluate the video image and record a full frame, or keyframe, into an FLV file. In Flash Video

Encoder, this setting is the keyframe interval value, which represents the number of frames

between keyframes. Flash Video Encoder approximates frames that reside between keyframes

by estimating the full value of all pixels on the screen by comparing multiple frames and

eliminating redundant information.

The keyframe interval value can be any number up to 100. When you select Automatic as an

interval setting, Flash Video Encoder places a keyframe every two seconds of playback time.

For example, if the video you’re encoding has a frame rate of 30 fps, a keyframe will be

inserted every 60 frames. In general, the default keyframe interval value provides a reasonable

level of control when seeking within a video clip. If you need to select a custom keyframe

placement value, be aware that the smaller the keyframe interval, the larger the file size.

If your footage has a lot of scene changes or rapidly moving motion or animation, then the

overall image quality may benefit from a lower keyframe interval. In general, a higher

keyframe interval produces better image quality because data is not wasted describing the

areas of an image that remain unchanged from frame to frame.

000_FLVEncoder.book Page 10 Friday, August 12, 2005 3:50 PM

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