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When using a computer to create digital video, there are two main types of output desktop video and analog output.
Analog output refers to digital video that has been composed and edited on the computer and then transferred to video tape (or film) for broadcast. This procedure is often referred to as "output to tape." Its primary use is to take advantage of the tremendous power of digital editing that the computer provides while delivering video in a widely adopted and accessible medium.
Desktop video refers to digital video that is intended to be played back on a computer. Its uses include such things as CD-ROM or DVD-ROM games, WWW sites with video, network-based training systems, PC-based kiosks, etc. Because of the tremendous size of digital movies, video that is destined for the desktop typically needs to be compressed. Due to this fact, desktop videos are frequently referred to as "compressed movies." Compression is the process by which files are reduced in size by the removal of redundant or less important data. But we'll talk more about this later.
Often a producer will want to make both types of output. For example, a TV show might need to create a tape version of their program for broadcast and a compressed version for their web site. Recently, there has been a shift towards producing both types of output as people realize that they can easily repurpose their content for a wide range of playback systems (broadcast, VHS tape, CD-ROM, DVD-ROM, Internet, LAN, etc.)
NOTE: Media Cleaner is focused on
producing compressed movies for desktop playback.
While it may be useful to people who are
outputting their material to tape, the majority of
features are geared towards helping optimize and compress video for desktop playback.
Making multimedia movies involves five
different steps which are briefly outlined below.
This section is not intended to give you a
thorough understanding of each step, but rather to
help place Media Cleaner's compression in context with the other parts of the multimedia
production cycle. Each step is elaborated on at our web
site in the "Tips & Info" section please
select "Terran's WWW site" from Media
Cleaner's Internet menu and press the "Tips & Info"
button for more details.
A capture card takes in the analog video
signal, runs it through an analog-to-digital converter
to produce a digital signal, usually compresses
this digital signal with special chips on the board,
and then sends the file to the system for storage on
a hard drive. Depending on your card, system, and hard drive, the captured video signal may
range from 1 to 10 Mb per second. Higher quality capture cards will generally give you
better results, but may be fairly expensive. You
should try to capture the video at full screen if
possible, and make sure that your system is
properly configured to get the best results.
For basic editing, Apple's MoviePlayer lets you do simple cuts. For more complicated edits and effects, a dedicated editing program such as Adobe Premiere is required. Premiere uses a time-line interface to allow you to put clips in order and set various transitions between the clips.
If you are using Adobe Premiere for your editing, you can use the Media Cleaner Export Module to transfer the movie from Premiere to Media Cleaner for compression.
If you aren't using Premiere, you must save the edited file in a high-quality QuickTime format. For most high-end capture systems (such as the Avid Media Composer, Media 100, Radius Video Vision PCI, Targa 2000 RTX, etc), you can use your card's capture codec with quality set to 100% (if applicable).
If you are using an inexpensive capture card or AV Macintosh, you may get better results using the "Animation" codec with the quality slider set to 100%. This will be somewhat slow and will produce a very big file. If this large file size is a problem, you can use the Photo-JPEG codec set to 100%. Photo-JPEG will be somewhat slower, but produces significantly smaller files. There is a very slight image degradation with Photo-JPEG, but for most applications, this degradation is not noticeable.
NOTE: Do not save the movie with
Cinepak (or any other distribution codec) within your
editing package; Media Cleaner will do this better
than your editing program. You should never Cinepak-compress a movie twice, since
this dramatically increases the compression
artifacts and lowers your final movie quality.
The compression step is often overlooked, yet has a dramatic impact on the final
image quality. The rest of this manual is focused on
this step, so we'll go into more detail later.
To put your video on a web site, you can use
the HTML Media Cleaner creates, or a WWW layout program such as Adobe PageMill or
Claris HomePage. Depending on the multimedia architecture you choose for your WWW
movies, you may also need a special video server
(more about this in Chapter 2.)