Adobe Media Encoder CS4 User Manual

Using

™

ADOBE® MEDIA ENCODER

CS4

This user guide is protected under copyright law, furnished for informational use only, is subject to change without notice, and should not be construed as a commitment by Adobe Systems Incorporated. Adobe Systems Incorporated assumes no responsibility or liability for any errors or inaccuracies that may appear in the informational content contained in this guide.

This user guide is licensed for use under the terms of the Creative Commons Attribution Non-Commercial 3.0 License. This License allows users to copy, distribute, and transmit the user guide for noncommercial purposes only so long as (1) proper attribution to Adobe is given as the owner of the user guide; and (2) any reuse or distribution of the user guide contains a notice that use of the user guide is governed by these terms. The best way to provide notice is to include the following link. To view a copy of this license, visit

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Updated Information/Additional Third Party Code Information available at

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Portions include software under the following terms:

MPEG Layer-3 audio coding technology licensed by Fraunhofer IIS and Thomson Multimedia (http://www.iis.fhg.de/amm/).

This product includes software developed by the Apache Software Foundation (http://www.apache.org/).

This product contains either BSAFE and/or TIPEM software by RSA Security, Inc.

Sorenson Spark™ video compression and decompression technology licensed from Sorenson Media, Inc.

Adobe Systems Incorporated, 345 Park Avenue, San Jose, California 95110, USA.

Notice to U.S. Government End Users. The Software and Documentation are “Commercial Items,” as that term is defined at 48 C.F.R. §2.101, consisting of “Commercial Computer Software” and “Commercial Computer Software Documentation,” as such terms are used in 48 C.F.R. §12.212 or 48 C.F.R. §227.7202, as applicable. Consistent with 48 C.F.R. §12.212 or 48 C.F.R. §§227.7202-1 through 227.7202-4, as applicable, the Commercial Computer Software and Commercial Computer Software Documentation are being licensed to U.S. Government end users (a) only as Commercial Items and (b) with only those rights as are granted to all other end users pursuant to the terms and conditions herein. Unpublished-rights reserved under the copyright laws of the United States. Adobe Systems Incorporated, 345 Park Avenue, San Jose, CA 95110-2704, USA. For U.S. Government End Users, Adobe agrees to comply with all applicable equal opportunity laws including, if appropriate, the provisions of Executive Order 11246, as amended, Section 402 of the Vietnam Era Veterans Readjustment Assistance Act of 1974 (38 USC 4212), and Section 503 of the Rehabilitation Act of 1973, as amended, and the regulations at 41 CFR Parts 60-1 through 60-60, 60-250, and 60-741. The affirmative action clause and regulations contained in the preceding sentence shall be incorporated by reference.

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Chapter 1: Resources

Activation and registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Help and support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Services, downloads, and extras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

What’s new . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Chapter 2: Video and audio basics

About video and audio encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Compression tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Video formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Chapter 3: Encoding media

About Adobe Media Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

File formats supported for import . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Encode media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Custom encoding settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Log files and error messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

iii

Index ................................................................................................................ 41

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Chapter 1: Resources

Before you begin working with your software, take a few moments to read an overview of activation and the many resources available to you. You have access to instructional videos, plug-ins, templates, user communities, seminars, tutorials, RSS feeds, and much more.

Activation and registration

Help with installation

For help with installation issues, see the Installation Support Center at www.adobe.com/go/cs4install.

License activation

During the installation process, your Adobe software contacts Adobe to complete the license activation process. No personal data is transmitted. For more information on product activation, visit the Adobe website at

www.adobe.com/go/activation.

A single-user retail license activation supports two computers. For example, you can install the product on a desktop computer at work and on a laptop computer at home. If you want to install the software on a third computer, first deactivate it on one of the other two computers. Choose Help

> Deactivate.

Register

❖ To register, follow the on-screen instructions in the Registration dialog box, which appears after you install the

software.

If you postpone registration, you can register at any time by choosing Help > Registration.

Adobe Product Improvement Program

After you have used your Adobe software a certain number of times, a dialog box appears, asking whether you want to participate in the AdobeProduct Improvement Program.

If you choose to participate, data about your use of Adobe software is sent to Adobe. No personal information is recorded or sent. TheAdobe Product Improvement Program only collects information about the features and tools that you use in the software and how often you use them.

You can opt in to or opt out of the program at any time:

• To participate, choose Help > Adobe Product Improvement Program and click Yes, Participate.

• To stop participating, choose Help > Adobe Product Improvement Program and click No, Thank You.

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ReadMe

A ReadMe file for your software is available on-line and on the installation disc. Open the file to read important information about topics such as the following:

• System requirements

• Installation (including uninstalling the software)

• Activation and registration

• Font installation

• Troubleshooting

• Customer support

• Legal notices

Help and support

Community Help

Community Help is an integrated environment on Adobe.com that gives you access to community-generated content moderated by Adobe and industry experts. Comments from users help guide you to an answer.

Community Help draws on a number of resources, including:

• Videos, tutorials, tips and techniques, blogs, articles, and examples for designers and developers.

• Complete on-line product Help, which is updated regularly by the Adobe documentation team.

• All other content on Adobe.com, including knowledgebase articles, downloads and updates, Developer

Connection, and more.

Choose Help > product name Help in the application to access the Help and Support page, the portal to all of the Community Help content for your product. You can also use the Help search field in some Creative Suite 4 applications, or press F1 (Windows), to access Community Help for your product.

The sites searched by the default Community Help search engine are hand-selected and reviewed for quality by Adobe and Adobe Community Experts. Adobe experts also work to ensure that the top search results include a mixture of different kinds of content, including results from on-line product Help.

For more information on using Community Help, see http://help.adobe.com/en_US/CommunityHelp/.

For a video overview of Community Help, see www.adobe.com/go/lrvid4117_xp.

For frequently asked questions about Community Help, see http://community.adobe.com/help/profile/faq.html

Product Help

Adobe provides a comprehensive user guide for each product in several formats, including on-line product Help, PDF, and printed book. Results from on-line product Help are included in your results whenever you search Community Help.

If you’re connected to the Internet, the Help menu within the product opens the product Help and Support page by default. This page is a portal to all of the Community Help content for the product. If you want to consult or search on-line product Help only, you can access it by clicking the product Help link in the upper-right corner of the Help and Support page. Be sure to select the This Help System Only option before you do your search.

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Resources

If you’re not connected to the Internet, the Help menu within the product opens local Help, a subset of the content available in on-line product Help. Because local Help is not as complete or up-to-date as on-line product Help, Adobe recommends that you use the PDF version of product Help if you want to stay offline. A downloadable PDF of complete product Help is available from two places:

• The product’s Help and Support page (upper-right corner of the page)

• Local and web Help (top of the Help interface)

For more information on accessing product help, see http://help.adobe.com/en_US/CommunityHelp/.

If you are working in Adobe InDesign, Photoshop, Illustrator, Flash, Fireworks, or Dreamweaver, and you want to turn off Community Help so that local Help opens by default, do the following:

1 Open the Connections panel (Window > Extensions > Connections).

2 From the Connections panel menu , select Offline Options.

3 Select Keep Me Offline and click OK.

Note: When you disable web services from the Connections panel, all other web services (such as Adobe Kuler and Adobe ConnectNow) are also disabled.

Printed resources

Printed versions of the complete on-line product Help are available for the cost of shipping and handling at

www.adobe.com/go/store.

Support resources

Visit the Adobe Support website at www.adobe.com/support to learn about free and paid technical support options.

Services, downloads, and extras

You can enhance your product by integrating a variety of services, plug-ins, and extensions in your product. You can also download samples and other assets to help you get your work done.

Adobe creative on-line services

Adobe®Creative Suite® 4 includes new on-line features that bring the power of the web to your desktop. Use these features to connect with the community, collaborate, and get more from your Adobe tools. Powerful creative on-line services let you complete tasks ranging from color matching to data conferencing. The services seamlessly integrate with desktop applications so you can quickly enhance existing workflows. Some services offer full or partial functionality when you’re offline too.

Visit Adobe.com to learn more about available services. SomeCreative Suite 4 applications include these initial offerings:

Kuler™ panel Quickly create, share, and explore color themes on-line.

Adobe® ConnectNow Collaborate with dispersed working teams over the web, sharing voice, data, and multimedia.

Resource Central Instantly access tutorials, sample files, and extensions for Adobe digital video applications.

For information on managing your services, see the Adobe website at www.adobe.com/go/learn_creativeservices_en.

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Resources

Adobe Exchange

Visit the Adobe Exchange at www.adobe.com/go/exchange to download samples as well as thousands of plug-ins and extensions from Adobe and third-party developers. The plug-ins and extensions can help you automate tasks, customize workflows, create specialized professional effects, and more.

Adobe downloads

Visit www.adobe.com/go/downloads to find free updates, tryouts, and other useful software.

Adobe Labs

Adobe Labs at www.adobe.com/go/labs gives you the opportunity to experience and evaluate new and emerging technologies and products from Adobe. At Adobe Labs, you have access to resources such as these:

• Prerelease software and technologies

• Code samples and best practices to accelerate your learning

• Early versions of product and technical documentation

• Forums, wiki-based content, and other collaborative resources to help you interact with like-minded users.

Adobe Labs fosters a collaborative software development process. In this environment, customers quickly become productive with new products and technologies. Adobe Labs is also a forum for early feedback. The Adobe development teams use this feedback to create software that meets the needs and expectations of the community.

Adobe TV

Visit Adobe TV at http://tv.adobe.com to view instructional and inspirational videos.

Extras

The installation disc contains a variety of extras to help you make the most of your Adobe software. Some extras are installed on your computer during the setup process; others are located on the disc.

To view the extras installed during the setup process, navigate to the application folder on your computer.

• Windows®: [startup drive]\Program Files\Adobe\[Adobe application]

• Mac OS®: [startup drive]/Applications/[Adobe application]

To view the extras on the disc, navigate to the Goodies folder in your language folder on the disc. Example:

• /English/Goodies/

What’s new

New features

The following features are new to Adobe® Media Encoder CS4.

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Resources

Batch encoding

Adobe Media Encoder includes several batch encoding features that let you easily create a dedicated media encoding workstation. Using this workstation lets you encode video and audio assets—a computationally demanding process— without interrupting your work with other computer applications.

Prioritize the encoding of assets You can specify the order in which media assets are encoded. You can also specify a

delayed start time so that encoding begins at a time when other applications aren’t using the encoding workstation.

Export duplicate items with multiple formats and encoding settings You can add multiple instances of the same

media asset, and apply different export formats and encoding settings to each asset for use with different applications and delivery methods.

Watch folder You can configure Adobe Media Encoder to look for video or audio files in certain folders called watched

folders. When Adobe

Media Encoder finds a video or audio file located in a watched folder, it encodes the file using the specified encoding settings. Adobe Media Encoder then exports the encoded file to the Output folder created inside the watched folder. For more information, see

“Create a watch folder” on page 26.

Encoding presets

Adobe Media Encoder includes encoding presets appropriate for the different video formats that it can export. Each encoding preset is designed for particular delivery scenarios and applications. Selecting a preset activates the appropriate video and audio encoding options (for example, bit rate, frame rate, and aspect ratio). In most cases, one of the provided presets matches your output goals. However, you can also adjust the parameters of an existing preset and save it as a custom preset. You can share customized presets with others and reload them when needed.

After Effect compositions and Adobe Premiere Pro sequences

You can import After Effects compositions and Adobe Premiere Pro sequences like any other supported file type.

Cue point support for F4V and FLV

Cue points cause video playback to start other actions within the presentation. For example, you can create a SWF application that has video playing in one area of the screen while text and graphics appear in another area. A cue point placed in the video triggers an update to the text and graphics, letting them remain relevant to the content of the video.

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Chapter 2: Video and audio basics

About video and audio encoding

Recording video and audio to a digital format involves balancing quality with file size and bitrate. Most formats use compression to reduce file size and bitrate by selectively reducing quality. Compression is essential for reducing the size of movies so that they can be stored, transmitted, and played back effectively. Without compression, a single frame of standard-definition video uses nearly 1 MB (megabyte) of storage. At the NTSC frame rate of approximately 30 frames per second, uncompressed video plays at nearly 30 MB per second, and 35 seconds of footage takes up about 1 GB of storage. By comparison, an NTSC file compressed in DV format fits 5 minutes of footage into 1 GB of storage at a bitrate of about 3.6 MB per second. To compress video for distribution at the highest possible quality, select the smallest compression ratio that delivers video within the file size and bitrate constraints of your target delivery media and playback devices.

When exporting a movie file for playback on a specific type of device at a certain bandwidth, you choose a compressor/decompressor (also known as an encoder/decoder, or codec), to compress the information and generate a file readable by that type of device at that bandwidth.

A wide range of codecs is available; no single codec is best for all situations. For example, the best codec for compressing cartoon animation is generally not efficient for compressing live-action video. When compressing a movie file, you can fine-tune it for the best-quality playback on a computer, a mobile device, the web, or a DVD player. Depending on which encoder you use, you may be able to reduce the size of compressed files by removing artifacts that interfere with compression, such as random camera motion and excessive film grain.

If you are new to digital video or want to learn more about digital video and encoding high-quality video content, this information can help you understand the trade-offs related to encoding video for different applications and viewing environments.

Frame rate

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, the higher the frame rate, the larger the file size. To reduce the file size lower either the frame rate or the bitrate. If you lower the bitrate and leave the frame rate unchanged, the image quality is reduced. If you lower the frame rate and leave the bitrate 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), Adobe 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), Adobe® achieve the new fps rate. However, if you must 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.

Media Encoder CS4 drops frames at a linear rate to

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Video and audio basics

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).

If your video clip is encoded with a higher bitrate, a lower frame rate can improve playback on lower-end computers. For example, if you are compressing a talking-head video clip with little motion, cutting the frame rate in half could save only 20% of the bitrate. However, if you are compressing high-motion video, reducing the frame rate has a much greater effect on the bitrate.

Bitrate

The bitrate (also referred to as 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, produce files using lower bitrates. 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, make short video clips to keep the download times within acceptable limits.

Key frames

Key frames are complete video frames (or images) that are inserted at consistent intervals in a video clip. The frames between the key frames contain information on movement and scene changes that occurs between key frames. For example, if a video depicts a person walking past a doorway, the key frames 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, Adobe Media Encoder automatically determines the key frame interval to use based on the frame rate of the video clip. The key frame interval value tells the encoder how often to re-evaluate the video image and record a full frame, or key frame, into a file. In Adobe the number of frames between key frames. Adobe by estimating the full value of all pixels on the screen by comparing multiple frames and eliminating redundant information.

In general, the default key frame interval value provides a reasonable level of control when seeking within a video clip. If you select a custom key frame placement value, be aware that the smaller the key frame 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 key frame interval. In general, a higher key frame interval produces better image quality because data is not wasted describing the areas of an image that remain unchanged from frame to frame.

Media Encoder, this setting is the key frame interval value, which represents

Media Encoder approximates frames that reside between key frames

Aspect ratios (frame size)

As with the frame rate, the aspect ratio (or frame size) for your file is important for producing high-quality video. At a specific bitrate (connection speed), increasing the frame size results in decreased video quality. When you select the frame size for your document, consider the frame rate, the aspect ratio of the source video clip, and your personal preferences to create a successful video presentation. Standard display resolutions on the Internet include 640 x 480, 512 x 384, 320 x 240, and 160 x 120 pixels.

The most common aspect ratio is 4:3 (standard television). Increasingly, 16:9 and 2:1 (wide screen) aspect ratios are becoming more commonplace as well. Typically, you should encode the video using the same aspect ratio at which it was originally captured. Altering the aspect ratio of a video clip can result in black bars (or masks) being placed on the sides or top and bottom sides of the image. The black bars are necessary when video not originally designed for widescreen viewing is shown on a widescreen display, or a narrower widescreen image is displayed within a wider

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Video and audio basics

aspect ratio. The original video is shrunk and placed in the middle of the widescreen frame. An exception to this practice is when encoding digital video (DV) formats, whose aspect ratio is slightly different than the 4:3 aspect ratio because DV uses rectangular pixels. When encoding video content captured with a digital video camera, manually specify the frame size of the DV format you are using to preserve the aspect ratio of the video, or select an appropriate preset (NTSC or PAL, for example).

The following list of standard frame sizes can be used as a guideline. You can experiment to find the best setting for your project.

Frame sizes for 4:3 aspect ratio video:

• Modem (56k): 160 x 120

• DSL: 320 x 240

• Cable: 512 x 384

• Cable/corporate LAN: 640 x 480

Frame sizes for 16:9 aspect ratio video:

• Modem (56k): 192 x 108

• DSL: 384 x 216

• Cable: 448 x 252

• Cable/corporate LAN: 704 x 396

Video with non-square pixels

Most static computer graphics use square pixels, which have a width-to-height ratio of 1:1. When working with digital video, pixels often have a different width-to height ratio and are referred to as rectangular pixels. The reason for this behavior is to allow analog video (for example, broadcast television) and digital video (for example, DVD video) to coexist. When encoding video formats with non-square pixels (also known as anamorphic video), resample the video image to the correct Display Aspect Ratio (DAR).

For example, standard NTSC digital video (DV), has a frame size of 720 x 480 pixels, and it’s displayed at an aspect ratio of 4:3. This means that each pixel is rectangular, with a pixel aspect ratio (PAR) of 10:11 (a tall, narrow pixel).

To calculate the image frame size to use when encoding video using non-square pixels, first decide which dimension— width or height—is the preferred master dimension, and then compute the other dimension as follows:

If height is the master dimension, calculate the width using the following formula:

width = height x

For example, if your video uses an aspect ratio of 4:3 the equation would appear as:

width = height x

If width is the master dimension, calculate the height using the following formula:

height = width x

aspect ratio width

aspect ratio height

3 4

aspect ratio height

aspect ratio width

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For example, if your video uses an aspect ratio of 4:3 the equation would appear as:

height = width x

As an example, if you are encoding a video whose frame size is 720 x 480 pixels, and you want to encode it with a 4:3 aspect ratio, first determine the width at which to encode the video frame in pixels:

640 = 480 x

The result is a video image height of 640 pixels.

Thus, you must encode the 720 x 480 image to 640 x 480, a standard 4:3 aspect ratio.

4 3

Interlaced versus noninterlaced video

Adobe Media Encoder deinterlaces video before encoding whenever you choose to encode an interlaced source to a noninterlaced output.

Most broadcast video is interlaced, though emerging high-definition television standards have interlaced and noninterlaced variants. Interlaced video consists of two fields that make up each video frame. Each field contains half the number of horizontal lines in the frame; the upper field (or Field 1) contains all of the odd-numbered lines, and the lower field (or Field 2) contains all of the even-numbered lines. An interlaced video monitor (such as a television) displays each frame by first drawing all of the lines in one field and then drawing all of the lines in the other field. Field order specifies which field is drawn first. In NTSC video, new fields are drawn to the screen approximately 60 times per second, which corresponds to a frame rate of approximately 30 frames per second.

Noninterlaced video frames are not separated into fields. A progressive-scan monitor displays a noninterlaced video frame by drawing all of the horizontal lines, from top to bottom, in one pass. Because of this, both fields that make up a video frame are shown simultaneously. Thus, a computer monitor displays video at 30 fps, and most video displayed on computer monitors is noninterlaced.

Compression tips

When you compress video, consider these recommendations:

Work with video in the native format of your project until your final output If you convert a precompressed digital

video format into another format such as FLV or F4V, the previous encoder can introduce video noise. The first compressor already applied its encoding algorithm to the video, reducing its quality, frame size, and rate. That compression may have also introduced digital artifacts or noise. This additional noise affects the final encoding process, and a higher bitrate may be required to encode a good-quality file. Use raw footage or the least compressed footage that is available to you.

Make your video as short as possible Trim the beginning and end of your video, and edit your video to remove any

unnecessary content.

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USING ADOBE MEDIA ENCODER CS4

Video and audio basics

Adjust your compression settings If you compress footage and it looks great, try changing your settings to reduce the

file size. Test your footage, and modify it until you find the best setting possible for the video you are compressing. All video has varying attributes that affect compression and file size; each video needs its own setting for the best results.

Limit effects and rapid movement Limit movement if you are concerned about file size. Any movement, particularly

with many colors, increases file size. Shaky camera work and zooms are particularly bad in this regard. Some effects increase file size because of the information they add to the video. On the other hand, some effects, such as blurs, can be used to decrease the number of bits in a compressed file.

Choose appropriate dimensions If your target audience has a slow Internet connection (such as phone modems),

make the dimensions of your video smaller, such as 160x120 pixels. If your audience has fast connections, you can make your dimensions larger (for example, 320x240 pixels).

Select an appropriate frame rate Frame rate indicates frames per second (fps). If you have a higher bitrate clip, a lower

frame rate can improve playback through limited bandwidth. For example, if you are compressing a clip with little motion, cutting the

frame rate in half probably saves you only 20% of the bitrate. 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 information from your hosting service. For mobile devices, use the devicespecific encoding presets, and the device emulator available through Adobe

Media Encoder. If you must reduce the

frame rate, the best results come from dividing the frame rate by whole numbers.

Note: When creating video for Flash, if you are creating 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 inconsistent.

Choose an appropriate number of key frames Each key frame is a frame that draws when the video is compressed, so

the more frequent your key frames are the better quality the footage is. More key frames also mean a larger file size. If you choose 30, a video key frame draws every 30 frames. If you choose 15, the quality is higher because a key frame draws ever 15 frames and the pixels in your footage are more accurate to the original.

Reduce noise Noise (scattered pixels in your footage) increases file size. Reduce noise using your video editor, to

reduce the video file size. Using more solid colors in your video reduces its file size. You can use the Gaussian blur filter to help reduce noise.

Compression tips for audio files

The same considerations exist for audio production as for video production. To achieve good audio compression, you must begin an audio file that is free of distortion and audible artifacts introduced from the source recording. If you are encoding material from a CD, try to record the file using direct digital transfer rather than the analog input of a sound card. The sound card introduces an unnecessary digital-to-analog and analog-to-digital conversion that can create noise in your transferred audio. Direct digital transfer tools are available for both Windows and Macintosh platforms. If you must record from an analog source, use the highest quality sound card available.

Note: If your source audio file is monaural (mono), it is recommended that you encode in mono for use with Flash. If you are encoding with Adobe mono, and select mono if necessary.

Media Encoder, and using an encoding preset, be sure to check if the preset encodes in stereo or

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USING ADOBE MEDIA ENCODER CS4

Video and audio basics

Video formats

FLV and F4V video formats for Flash

By default, Adobe Media Encoder encodes video for use with Flash using the F4V video format using the H.264 video codec for use with Flash Player 9.0.r115 and later, and the FLV format using either the On2 VP6 codec for use with Flash Player 8 and later, and the Sorenson Spark codec for use with Flash Player 7 and later. To understand how Flash achieves high-quality video with low bandwidth requirements, you must 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 repeated from the previous frames. A temporally compressed frame is often called an interframe.

H.264, On2 VP6, and Sorenson Spark are temporal codecs. Although many other codecs use spatial compression (for example, JPEG is a spatial codec), the efficient temporal compression of the H.264, On2 VP6, and Sorenson Spark codecs, among other features, distinguishes them from other compression technologies because these codecs require a much lower bitrate to produce high-quality video.

It’s important to note that interframe codecs also use intraframes. Intraframes are used as the reference frames (key frames) for the interframes. Both the On2 VP6 and Sorenson Spark codecs always begin with a key frame. Each key frame 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 key frame.

An important dependency of the key frame distance is that it affects the ability of Flash Player to seek (fast-forward or rewind) through an FLV or F4V file. Flash Player can only advance from key frame to key frame, so if you want to skip to different places and pause the frames, use a lower key frame distance value. If you want to advance to every frame in an FLV or F4V file, use a key frame distance value of 1. You set the keyframe distance in the Advanced section of the Video tab in the Export Settings dialog box. When you reduce the key frame distance value, raise the bitrate for the video file to maintain comparable image quality. You set the the bitrate in the Video tab of the Export Settings dialog box.

H.264, On2 VP6, and Sorenson Spark video codecs

When encoding video using Adobe Media Encoder, you can choose from three different video codecs with which to encode your video content for use with Flash Player:

H.264 Support for H.264 video was incorporated into Flash Player beginning with version 9.0.r115. F4V video is a

container format for the H.264 video codec, also referred to as MPEG-4 AVC (Advanced Video Encoding). The H.264 video codec provides higher quality video at lower bitrates than the Sorenson Spark and On2 VP6 video codecs used by earlier version of Flash Player, however, it is more computationally demanding than either of these codecs.

In addition to the F4V container format, Flash Player 9.0.115.0 and later versions support file formats derived from the standard MPEG-4 container format. These file formats include MP4, M4A, MOV, MP4V, 3GP, and 3G2, if they contain H.264 video or HE-AAC v2 encoded audio, or both.

Note: If you need to use video with alpha channel support for compositing, use the On2 VP6 video codec; F4V does not support alpha video channels.

Last updated 4/29/2012

+ 31 hidden pages

Adobe Media Encoder CS4 User Manual

Contents

Chapter 1: Resources

Activation and registration

Help with installation

License activation

Register

Adobe Product Improvement Program

ReadMe

Help and support

Community Help

Product Help

Printed resources

Support resources

Services, downloads, and extras

Adobe creative on-line services

Adobe Exchange

Adobe downloads

Adobe Labs

Adobe TV

Extras

What’s new

New features

Chapter 2: Video and audio basics

About video and audio encoding

Frame rate

Bitrate

Key frames

Aspect ratios (frame size)

Video with non-square pixels

Interlaced versus noninterlaced video

Compression tips

Compression tips for audio files

Video formats

FLV and F4V video formats for Flash

H.264, On2 VP6, and Sorenson Spark video codecs