Video optimization terminology
Aspect ratio is the proportion of the horizontal to the vertical dimensions of an image. The
computer/standard TV ratio is 4:3. Film/HDTV (the new standard, and the ratio of Apple
Cinema Displays) runs at 16:9.
Codecs are algorithms that are built into software. They are converters that co mpress and
dec ompress digital data, particularly video files. There are dozens of video codecs, includ-
ing DV, MPEG-4, and Cinepak. Some are better for your purposes than others.
Fast Start is pseudo-streaming. When you play QuickTime and Windows Media Player files
from a regular web server, the file downloads to the viewer's computer at the best speed
for its connection and begins to play while the download is still taking place.
Hint Tracks tell a streaming server how to prepare video clip data for successful streaming.
Without a hint track, the video will not stream. Hint tracks aren't needed for downloading
Streaming is the process of sending data to a computer in real time. The viewer doesn't
have to wait for the clip to download before they can see it.
To see encoded video, the viewer needs a player in your format. The “best”
player format for you is one that is already installed on your viewer's computer.
Because you can't always predict what that will be, you'll need to create files for more
than one player. The players mentioned below are the most popular ones.
If you are creating movies for both Mac and PC users, save your edited files in
at least two formats—AVI (for Windows users) and MOV (for Mac users). Even though
both movie types can be played on both platforms, very few Mac users have Windows
Media Player. Conversely, although a reasonable number of Windows users have
QuickTime, all have WMP.
• QuickTime. QuickTime is Apple's cross-platform video software. It imports
many other file formats, including AVI, and outputs to a variety of codecs.
Windows users of IE5.5 and later need to download a special ActiveX file to
be able to see QuickTime content. Note that not all AVI files play correctly
on a Mac, while more and more Windows users have QuickTime support
because of the popularity of iTunes, which requires it.
• Windows Media Player. Windows Media Player is installed on all Windows
computers, making it the single-most popular player. The player is cross-plat-
form, but Mac users must downloaded it. The Mac version does not support
all formats, such as “secure” versions of Windows media.