Chapter 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22
Appendix A | Appendix B | Appendix C | Glossary | Index | Legal Stuff | License

Appendix B - Multimedia Architecture and Codecs

Multimedia Architectures | CD-ROM Architectures | World-Wide Web Architectures | Codecs | Codec Central | QuickTime Video Codecs | QuickTime Audio Codecs | RealMedia Codecs | RealMedia Audio Codecs | VDO Codecs

QuickTime Codecs: ClearVideo | Cinepak | Indeo | JPEG | Video | None | Animation | Power!Video | IMA | GSM | Other Audio Codecs


Multimedia Architectures

A multimedia architecture provides for the creation, storage and playback of sychronized multiple media types. The architectural elements that relate to Media Cleaner include:
1.) Software services - a set of programs or operating system features that allow other programs to handle multimedia files. These may include System extensions, plug-ins, servers, etc.; for example, the QuickTime extension and plug-in.

2.) File formats - the specific structure(s) which store the elements that make up a multimedia presentation; for example, a QuickTime movie.

3.) Support for codecs (video and audio compressors) - either in an open fashion like QuickTime, or in a proprietary fashion like VDOLive.

Architectures, formats, and codecs are closely related but not interchangeable terms. Understanding these distinctions will help you produce better multimedia solutions. For example, QuickTime movies which use the correct codecs can actually play back under ActiveMovie. In some cases this might provide more flexibility to your users.

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CD-ROM Architectures

QuickTime


The dominant architecture for CD-ROM video is Apple's QuickTime. It enjoys an impressive market share due to its cross-platform support, wide range of features, and free licensing. QuickTime provides for more data-types than simply audio and video. Text tracks, MIDI audio, sprites, VR panoramas, and VR objects all are possible within QuickTime. It is a mature technology with an extremely large installed user base.

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Video for Windows

Microsoft's Video for Windows is very similar to a limited version of QuickTime, but does not support tracks other than video and audio ­ text, sprites, etc. are unsupported. In addition, Video for Windows doesn't handle audio/video synchronization as well as QuickTime, and doesn't support variable-length frames.

Video for Windows files are often called "AVIs" due to the ".avi" Windows file suffix. Video for Windows is no longer supported by Microsoft, and will be replaced by ActiveMovie. Unlike QuickTime, Video for Windows is a Windows-only architecture. Because of this, the Video for Windows architecture has not been adopted for most CD-ROMs.

There are free conversion utilities for changing movies from QuickTime to Video for Windows, and vice versa without recompressing the video. This conversion is called "transcoding" and takes advantage of similarities between the architectures so the files don't need to be recompressed. Check out our web site for links to these tools.

Video for Windows is normally installed on all Windows machines as part of the system software ­ this is the main reason it is sometimes used for Windows-only products.

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ActiveMovie

Microsoft's ActiveMovie has been announced as the replacement for Video for Windows. ActiveMovie 1.0 plays Video for Windows and QuickTime files, but is not available on the Macintosh. ActiveMovie does not currently support capture applications, and cannot be used for cross-platform titles.

ActiveMovie 2.0 may address these issues, but was still in development at the time this manual was written.

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World-Wide Web Architectures

QuickTime

QuickTime is widely used for putting movies on the WWW, due to the fact that it is free, easy to use, and has a very large installed base. QuickTime has a "fast start" feature which allows movies to be played inside a web page as they download. The QuickTime plug-in is included with Netscape Navigator 3.0, so most users will be able to view QuickTime movies without downloading any additional software, as long as the movies are made with the standard QuickTime codecs.

QuickTime is currently a "progressive download" architecture that lets users watch movies as they download. If the user has a fast connection and the movie was made with a low data rate, this may mean they can see the movie almost immediately as it downloads. If the user has a slow connection, or the movie was made at a high data rate, the movie will pause for a while before it starts playing, and may pause during play as it continues to download. Regardless of connection, users don't have to wait for the entire file to download before they can start viewing the movie.

You do not need special server hardware or software to put QuickTime on your site. Movies are simply files as far as the server is concerned, so you can host these movies on Macintosh, Windows, or Unix servers.

The main downside to QuickTime 2.5 (and earlier) is that it currently lacks built-in, optimal codecs for web video content, so the image quality isn't as good as the images produced by the other architectures at low data rates. Low data rate audio codecs are also missing, so the sound isn't great and it takes more bandwidth than necessary.

Fortunately, other companies produce good codecs for QuickTime, such as Iterated Systems' ClearVideo. However, users must manually download these additional codecs before viewing movies made with them. To simplify this process, Terran has an all-in-one codec installer on our site. Terran also maintains a "Movie Help" page that you can link to in order to provide your viewers with help configuring their browsers for QuickTime viewing. See our Web page for more details.

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RealMedia

RealMedia is a new architecture for Internet multimedia. RealMedia was created by Progressive Networks, makers of RealAudio.

The first version of RealMedia is focused on video and audio, and is referred to as RealVideo. Later releases of RealMedia will incorporate other formats including MIDI, text, images, vector graphics, animations and presentations.

RealMedia content can be placed on your site either with or without special server software. There are performance advantages with the server, but you don't have to buy one to get started. However, high volume sites will definitely want a server to get substantially improved file delivery performance.

Progressive's RealMedia was designed to address some of the issues associated with putting video on the Internet, such as the problem of non-guaranteed data delivery over the Internet. It also has very high quality audio codecs built in, so movies sound good even at low data rates. RealMedia has provisions for "broadcasting" your movies, as well as many other interesting features.

Users can view RealMedia sites with the RealPlayer, a free "client" application available from Progressive. A Netscape plug-in is also available. For users who want all the "goodies", Progressive sells an "enhanced" version of the RealPlayer for a small fee.

The main downside to RealMedia is that it currently requires a PowerMac or Pentium computer to view. As such, RealMedia movies aren't available to the full range of potential users.

For more information on RealMedia, please see the "RealMedia" folder on the Media Cleaner Pro 2.0 CD-ROM, or stop by Progressive's WWW site at: http://www.real.com

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VDO

VDOnet Corporation makes two complementary formats targeted at web video delivery. VDOLive is a streaming architecture that adjusts to viewers' connections, and LiteVDO is a progressive download format that is useful for viewers that can't access VDOLive files.

VDOLive
VDOLive is a "true streaming" architecture that adjusts to viewers' connections as they watch movies. Thus, "true streaming" movies play in real-time with no delays for downloading. For example, if you clicked on a 30 second movie, it would start playing and 30 seconds later it would be over, regardless of your connection, with no substantial delays.

VDOLive's true streaming approach differs from both RealMedia and QuickTime's "progressive download" approach. Progressive download allows you to watch (or hear) as much of the movie as has downloaded at any time, but movies may periodically pause if the movie has a higher data rate than the user's connection, or if there are problems with the connection or server, such as very high traffic.

In contrast to progressive download, the VDOLive server continuously "talks" to the VDOPlayer (the client) to determine how much bandwidth a connection can support. The server then only sends that much information, so movies always play in real-time. In order to support this real-time adjustment of the data-stream, you must use special server software to put VDOLive files on your site.

The real-time adjustment to the viewer's connection works like this: VDOLive files are encoded in a "pyramidal" fashion. The top level of the pyramid contains the smallest amount of the most critical image data. If your user has a slow connection, they are only sent this top portion. The file's next level has more data, and will be sent if the viewer's connection can handle it, and so forth. Users with very fast connections (T1 or better) are sent the whole file. Thus, users are only sent what they can receive in real-time, but the data has been "presorted" so that the information they get is the best image for their bandwidth.

Because VDOLive uses a different type of Internet protocol than the standard one used by web sites, it may not work for some users behind firewalls and other web obstacles. LiteVDO is a solution to this dilemma (see below).

A downside to VDOLive is that viewers must have a PowerMac or Pentium computer to view it. Also, since VDOLive automatically adjusts the video to the bandwidth of the user's connection, you do not have control over how the final image will appear to viewers. Over slow connections, the image may be "blurry" and play at low frame rates. However, users don't have to wait to see the video. We recommend you experiment with the demo version of VDOLive included on the Media Cleaner Pro 2.0 CD-ROM to see how it meets your needs.

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LiteVDO
LiteVDO is a QuickTime codec for Macintosh and a proprietary format for Windows. Future versions may be incorporated into one format. It is a progressive download format that works around firewalls and other Internet obstacles. By using LiteVDO in conjunction with VDOLive, you can be sure that your viewers can see your material, regardless of their Internet configuration.

Like fast start QuickTime, LiteVDO is simply a file, and does not require a special server. However, many people who own VDOLive servers also use LiteVDO to provide access to viewers that can't see the streaming files.

For more information on VDOnet's products, please visit their web site at: http://www.vdo.net

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Codecs

Codecs are the actual compression and decompression algorithms that reduce the size of desktop movies so they can be played on personal computers.

Below are brief descriptions of the most common codecs as of April 1997. Instead of trying to cover the available codecs here in depth, we invite you to drop by our web site for more details and examples. Our web site will also have the latest news on the new codecs which should be available in mid- to late- 1997.

To go to Terran's web site and view the various codecs, please check out Codec Central.

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Codec Central

Codec Central is a web site Terran maintains to help you stay current with the various codecs and architectures. Codec Central has sample compressed video, more codec information, and other useful resources. As a Media Cleaner owner, you may also be eligible for special discounts on software.

To go to Codec Central, choose it from Media Cleaner's Internet menu, or go to: http://www.CodecCentral.com

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QuickTime Video Codecs

ClearVideo

ClearVideo is a commercially available codec designed for low data rate movies. It is well suited to WWW video and corporate LAN/WAN applications. The ClearVideo codec is made by Iterated Systems, Inc. and is based on their patented fractal technology. For movies at data rates between 1 - 30 KBps, ClearVideo normally produces results that far exceed the standard QuickTime codecs, such as Cinepak, JPEG, etc.

The main downside to ClearVideo is that it requires at least a mid-range PowerMac or Pentium for acceptable playback. ClearVideo is available as a codec for QuickTime, RealMedia and Video for Windows. Please see Codec Central for more details and samples.

The ClearVideo codec is not applicable to CD-ROM and higher data rates at this time.

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Cinepak

Cinepak is the old standard for CD-ROM QuickTime compression. It plays well on most mid-range and faster machines (68040 Mac or any PowerMac, 486 PC or any Pentium).

The image quality of Cinepak often leaves something to be desired. Cinepak must always compress movies at least 10:1, so it is less useful at higher data rates (4x CD-ROM and above). If you are making a Cinepak movie in which the data rate stays too low despite the data rate you specify, you may get better results with the Video codec (see below).

In the past, there weren't any good alternatives to Cinepak, so most CD-ROM titles were created with it. However, a few new codecs are in development that may offer attractive alternatives to Cinepak in mid- to late- 1997. Please see Codec Central for more details.

If you don't wish to purchase a commercial codec for your CD-ROM titles, Cinepak is often the best choice for 2x CD-ROM data rates. While it can be used at WWW data rates, Cinepak was never designed for very low bandwidth, and does not work well under about 30 KBps.

Cinepak is available for Video for Windows as well as QuickTime. Because of this fact, files can be "transcoded" from one architecture to the other without recompressing the data. For more information on changing QuickTime to Video for Windows, and vice versa, please select "Terran's WWW site" from Media Cleaner's Internet menu, and press the "Tips & Info" button.

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Indeo

Indeo is an alternative to Cinepak produced by Intel. It usually requires a somewhat faster CPU than Cinepak for good playback. Indeo may produce better image quality in some cases, but has color artifacting that some producers find objectionable.

Indeo 4 (also called "IVI", which is short for Indeo Video Interactive), is a newer version of Indeo that supports interactive controls such as dynamic brightness control, sprites, multi-version movies, and more. However, as of the writing of this manual, IVI was not available on the Macintosh and requires a very fast Pentium for optimal playback. Because of this, it has not been widely adopted for CD-ROMs.

Like Cinepak, Indeo is not well suited to WWW data rates.

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JPEG

JPEG is generally used for capture, editing and storage of high-quality video files; it is not normally used as a distribution codec for normal desktop playback.

There are three JPEG-based codecs built into QuickTime. They are Photo-JPEG, MJPEG-A, and MJPEG-B. MJPEG stands for "Motion JPEG," and is identical to Photo-JPEG except that the MJPEG codecs have translators built in to support the different capture cards.

NOTE: MJPEG is not the same as MPEG - please see the "MPEG" section in Chapter 2 for more details on MPEG.

All of the JPEG codecs use the JPEG algorithm to spatially (not temporally) compress movies.
MJPEG-A and MJPEG-B are versions of JPEG that are designed to work with the hardware JPEG chips on most capture cards. They can theoretically be used instead of the proprietary codecs shipped with most cards, and may be useful for exchanging your raw capture files with other capture card owners.

The JPEG codecs require significant amounts of CPU power and are not well suited to CD-ROM or higher data rates, except when assisted by a hardware capture card. Large image and/or high frame rate movies usually don't play smoothly with JPEG.

Photo-JPEG has some application for WWW video, although other commercial codecs, such as ClearVideo, are often preferable for most movies. JPEG does work very well for "slide-show" movies that have a very low frame rate.

JPEG is often used as a "storage" format for large files that need to be archived with good quality. It is a lossy codec, but at 100% quality, the image degradation is minimal. However, you should avoid saving the same file multiple times with JPEG, as the JPEG artifacts may "build up," and become objectionable.

NOTE: MJPEG was added in QuickTime 2.5. As such, it will not be available on Windows machines until QuickTime 3.0 for Windows ships. Because of this, we don't recommend widely distributing your movies in MJPEG format at this time.

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Video

The Video codec is a precursor to Cinepak. Because it doesn't compress as highly as Cinepak, it often doesn't produce as good image quality at a given data rate. However, unlike Cinepak, it doesn't "top out" at higher data rates, and therefore often works better with 4x and higher CD-ROMs or DVD-ROMs. Like Cinepak, the Video codec plays well on lower-end machines, so it is a "safe" codec for the widest range of CPUs.

In the past, there haven't been any good tools to control the Video codec, because it doesn't internally limit its data rate. As such, very few titles have been made with the Video codec. Media Cleaner Pro 2.0 offers several data rate control options that now make the Video codec useful for various projects. Please see Chapter 19 for more information on using data rate control.

Like Cinepak, Video is not normally a good choice for WWW movies.

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None

The None codec stores the movie frames without any compression. As such, it is lossless and produces huge files. Movies using the None codec normally won't play smoothly given their high data rates.

None is often used as a "storage" format for files that need to be archived with perfect quality, as well as an intermediate format for files that need to have effects applied to them multiple times. However, the Animation codec is usually a better storage format given its smaller file sizes ­ see below for more details.

NOTE: Choosing the None codec does not pass through the current video without recompressing it. Instead, None changes the video to an uncompressed format. See Chapter 16 for details on how you can pass through video from your source movie without recompressing it.

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Animation

Animation is a codec designed for computer-generated content, such as screen captures. It is lossy at quality settings from 1%-99%, and lossless at 100%. Since it is lossless compression, files compressed with the Animation codec may be quite large at 100% quality.

Animation at 100% is often used as a "storage" format, as well as an intermediate work format. It is slightly slower than the None codec, but usually produces smaller files. Because it is lossless, Animation at 100% will not introduce any noise into the video signal, which is why it is sometimes used rather than JPEG.

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Power!Video (formerly "TrueMotion-S")

Power!Video is a commercial codec available from Horizons Technology. Previously named TrueMotion-S, Power!Video is a spatial-only compressor that works well for 4x and higher CD-ROMs and DVD-ROM discs. It is also good for kiosks which play video from hard drives.

Because Power!Video doesn't support temporal compression, it often does not produce as good results as Cinepak at 2x and lower CD-ROM speeds. It is fairly comparable to Cinepak in its CPU requirements, so it plays well on a wide range of computers. Power!Video is not useful for most WWW video.

When a Power!Video compressed movie is doubled on the screen, every other horizontal line is replaced with a black line. This allows for smoother playback, and reduces pixelation. Some people like the black-line effect, while others find it objectionable.

NOTE: Due to some issues surrounding Power!Video's implementation of the "Options" button, you cannot set the Power!Video specific features in Media Cleaner. Until Horizons Technologies revises Power!Video, you must use the Power!Video control panel to set the codec specific features.

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QuickTime Audio Codecs


IMA

IMA is a cross-platform audio codec that offers 4:1 compression. It is built into QuickTime 2.1 and later on the Mac, and QuickTime for Windows 2.1.2 and later. IMA only works on 16-bit audio, and provides very good sound quality. It is moderately CPU intensive, so it is best used with fast 486 or 68040 computers, or any PowerMac or Pentium.

Often IMA is used with 16-bit, 22 kHz audio for CD-ROM titles, which takes 11 KBps. This IMA compressed audio track sounds dramatically better than an uncompressed 8-bit, 11 kHz audio track, which also takes 11 KBps.

Because IMA is only 4:1 compression, it is not great for Web video. For example, a 6 kHz audio track is about 3 KBps (all of a 28.8 modem's bandwidth).

However, as of the publishing date of this manual, there were no other cross-platform QuickTime audio codecs available, so most people are using IMA for WWW video.

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GSM

GSM is an audio codec that offers 10:1 compression. GSM is not yet freely available cross-platform. Like IMA, it only works on 16-bit sound. Because it has a much higher compression ratio, it is primarily aimed at Web video. The sound quality is not as good as some other non-QuickTime technologies, such as RealAudio.

GSM is currently available for Macintosh, but is not part of the standard QuickTime install.

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Other QuickTime Audio Codecs (Mace, Ulaw, Macromind)

There were several audio compressors prior to IMA, including Mace and Ulaw. These produce larger files with worse sound quality than IMA, so they are generally no longer used.

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RealMedia Codecs

RealMedia currently only has two video codecs. However, RealMedia is changing rapidly, so we recommend that you check "Codec Central" in Media Cleaner's Internet menu for any new developments.


RealVideo (Standard)

The RealVideo (Standard) codec was developed by Progressive. It is usually best for data rates below 3 KBps. It tends to work better with relatively static material than it does with higher action content.

Depending on your settings, the RealVideo (Standard) codec usually encodes faster than the RealVideo (Fractal) codec. However, it is significantly more CPU intensive than the RealVideo (Fractal) codec, and usually requires a very fast PowerMac or Pentium for optimal playback.

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RealVideo (Fractal)

The RealVideo (Fractal) codec is a version of Iterated Systems' ClearVideo codec. As such, the image quality, compression time, etc. is very similar to the QuickTime version of ClearVideo.

RealVideo (Fractal) is usually a better option than RealVideo (Standard) for movies above 3 KBps. It is not quite as CPU intensive, but still requires a mid-range to fast PowerMac or Pentium for optimal playback.

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RealAudio Codecs

There are many different RealAudio codecs. Each codec is named according to the data rate it produces, and the type of content for which it is best suited. Generally, you should choose the codec that best describes your source movie content and the data rate you desire.

The various RealAudio codecs control most of the audio parameters, such as bit depth, frequency, and data rate. You can only select volume adjustments in the Audio tab when creating RealMedia or RealAudio files.

NOTE: The names of the RealAudio codecs refer to "Kbps" which is kilobits, not KiloBytes. Kilobits are 1/8th the size of KiloBytes. To do an approximate conversion, just shift the decimal one place to the left. For an accurate conversion, a calculator is useful.

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VDO Codecs

VDOWave Video Codec

There is only one VDO video codec at this time. It can produce both VDOLive and LiteVDO files. The codec controls most of the compression parameters, so you can only adjust a few options when creating VDO files.

VDOWave Audio Codec

There is also only one VDO audio codec at this time. It produces 20:1 compressed 16-bit, 8 kHz, mono audio. Because the codec specifies all the audio parameters, you can only select volume adjustments in the Audio tab when creating VDO files.

NOTE: The codec information presented above is very brief, and doesn't cover the new codecs that will be released in 1997. For a much more comprehensive discussion of codecs and sample video, please select the "Codec Central" option in Media Cleaner's Internet menu.

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