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QuickTime Codecs: ClearVideo | Cinepak | Indeo | JPEG | Video | None | Animation | Power!Video | IMA | GSM | Other Audio Codecs
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.
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.
ActiveMovie 2.0 may address these issues, but
was still in development at the time this manual
was written.
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.
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
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.
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
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.
To go to Codec Central, choose it from Media Cleaner's Internet menu, or go to:
http://www.CodecCentral.com
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.
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.
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.
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.
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.
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.
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.
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.
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.
GSM is currently available for Macintosh, but
is not part of the standard QuickTime install.
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.
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.
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.
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.
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.
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.