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556 VIDEOSTREAMINGwith the video files and servers, each technology may have
its own proprietary player. In some cases, one technol-
ogy’s media files cannot be played by another technology’s
player.
As indicated above, the third common streaming tech-
nology component is file creation, compression, and en-
coding. It involves the process of creating video files
for streaming. Again, each technology may have its own
proprietary way of creating, compressing, and encoding
streaming video files. Therefore, special software may be
needed to create streaming video files that are compatible
with the video player on the receiving end.
The above discussion has focused on the system re-
quirements for streaming video. At this point, it is worth
noting that the typical streaming video system has five
basic functions. First, the video must be captured, digi-
tized, and then stored on a disk. Second, after the video
is stored on a disk, it can be edited to improve its quality
and content. Third, the video file must be compressed and
encoded to the appropriate streaming format. Fourth, the
video is delivered to the user via the video server. And, fifth,
the user receives, decodes, buffers, and plays the video on
the computer.CAPTURING AND DIGITIZING VIDEO
In working with streaming video, the first step is to record
the video or obtain a recorded video. There are two types
of video that can be recorded. The first is analog video,
which is produced with a vhs, hi-8, or beta cam format.
The second is digital video, which is produced with a dig-
ital recorder or camera (DoIt & WISC, 2002).
Analog video contains video information in frames
consisting of varying analog voltage values. It tends to
degrade over time and it can contain imperfections such
as snow in the picture. Digital video contains video infor-
mation in a series of digital numbers that can be stored
and transmitted without imperfections. Digital video does
not degrade over time. The recent advances in the digital
technology make it easier to store, retrieve, and edit digital
video (Compaq, 1998).
If the video is from an analog source, it will have to be
converted and compressed into a digital format. In order
to do this conversion, an analog video capture card and
the appropriate software will have to be installed on the
computer. The video capture card is an expansion card
that works in conjunction with, or replaces, the graph-
ics adapter inside the computer. If the video is digital,
a FireWire capture card can be used and the analog-to-
digital step is not needed (Videomaker Magazine, 2001).
A side note on the digital video format that is worth-
while to review is that digital video often uses a different
color format than the format used for computer monitors.
Computer monitors display the color information for each
pixel on the screen using the RGB (red, green, blue) for-
mat. (Pixels can be defined as the small elements or points
that make up the frame.) Digital video frequently uses a
format known as YCrCb, where Y represents the bright-
ness (or luma) of a pixel, and Cr and Cb represent the pure
color. In the different color schemes used in digital video,
each pixel will have a brightness component but groups
of pixels may share the CrCb color data. Hence, the terms24-bit, 16-bit, and 12-bit color schemes refer to the num-
ber of color bits required per pixel (Compaq, 1998).
With the capture and conversion of the video, the video
is transferred into a format that can be edited and then
encoded for streaming. A number of formats are avail-
able. One of the most common of these is the AVI format.
AVI stands for Audio Video Interlaced and was created
by Microsoft. It is one of the oldest formats in use and is
included with Microsoft’s Windows applications (Fischer
& Schroeder, 1996). This format was used in many of the
early video editing systems and software. However, there
are restrictions in using this format; the most notable of
these is compatibility issues with some of the more ad-
vanced editing systems. Even with these issues, many edit-
ing systems and software can still use this format.
Another format is the MOV format, which was origi-
nally developed for the Macintosh computer by Apple. It
then became the proprietary standard of Apple’s Quick-
Time streaming technology (Fischer & Schroeder, 1996).
One of the most recent formats is the MPEG format.
MPEG is a newer format and it is becoming very popular
with streaming video users. MPEG stands for Motion Pic-
tures Experts Group, which is an international organiza-
tion that developed standards for the encoding of moving
images (Fischer & Schroeder, 1996). There are a number
of MPEG standards available, primarily for the encoding
and compression of streaming video. These will be dis-
cussed in more detail later in this paper. However, one of
the initial standards that was developed, MPEG-1, is used
for the storage of video.
In capturing and converting video for streaming, it is
recommended to maintain the highest quality video pos-
sible. The result will be very large video files that will have
to be edited and streamed. However, it is better to start
with the highest quality that can be maintained and then
scale down to the quality that can be streamed. Starting
with a lower quality leaves fewer options for editing, com-
pression, and encoding.EDITING THE VIDEO
Once the video has been captured and converted to a
digital format, it can be edited with a variety of edit-
ing tools. As mentioned above, each of the three main
streaming technologies—RealOne, QuickTime, and Win-
dows Media—has editing tools. Editing is critical as it
impacts how the video is ultimately received by the user
and the end user’s needs are paramount (see Producing
Streaming Video for more.)
In editing a video, one of the first things that may
have to be done is cropping the video. Cropping the
video involves removing the edges, where electronic er-
rors, glitches, and black bars may be seen. These usually
appear during the process of recording and converting the
video. In most cases, removing about 5% of the edges will
eliminate the glitches. In cropping a video, it is important
to remember that the final dimensions of the video must
be compatible with the encoding technology (Kennedy,
2001).
Television systems use a technique called interlacing
to display a picture on the screen. This process involves
displaying the picture on every other line on the television