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BANDWIDTH 557screen. Then lines are inserted between the first set. This
process of alternating the picture lines eliminates any
flicker on the screen. Videos also have this feature. How-
ever, for streaming video that will be displayed on a
computer screen, interlacing is not needed. Some cap-
ture cards have a deinterlacing feature and some cam-
corders will record video without interlacing. However, if
the video is interlaced at the editing step, and the file is
very large, it is advisable to deinterlace the video during
editing (Kennedy, 2001).
Also, when film is converted to video, additional frames
are added because film is shot at 24 frames per second and
depending on the video standard, television may run from
25 to 30 frames per second (Kennedy, 2001). The process
of converting film to video, where the additional frames
are put in, is called Telecine. It is best to avoid adding
frames that are not needed. Therefore, if it is available, an
Inverse Telecine conversion should be used to reduce the
video back to 24 frames per second (Kennedy, 2001).
If a video has been shot with a lot of motion, the video
could appear to be shaky or fuzzy, and not ideal for stream-
ing. If this is the case, the best option may to use a still
frame or slow motion. A still frame or slow motion may
not look very natural, but it is better than streamed video
that is not viewable.
Although special effects are great when viewed in a
movie, they do not work well in streaming video because
they utilize a lot of memory and impact the quality of the
video. It is generally recommended that special effects be
removed from the video. Streaming video is limited in its
ability to deliver smooth video for any motion such as
dance that relies on fluid movements. Also, if text is used
in the video, it should be concise, legible, and easy to read.
Audio is a very important part of streaming video. If
the video has an audio portion, the quality of the audio
needs to be reviewed. For example, it is advisable to avoid
the use of background music or other noise in order to
ensure that speakers can be heard clearly. It is also good
to prepare the audio to work on the worst speaker sys-
tem that any potential user may have. If the audio is not
clear then the usefulness of the video is greatly dimin-
ished.BANDWIDTH
Before covering the topic of compressing and encoding, it
is essential to understand the concept of bandwidth. The
reason is that bandwidth is a critical factor in the trans-
mission and reception of streaming video. Bandwidth
is, simply put, the amount of information that can pass
through a particular point of the wire in a specific amount
of time (RealNetworks, 2000). Network bandwidth can be
compared to a water pipe and a file to a tank of water. If
the pipe is very narrow, then it will take a long time for the
water from the tank to flow through the pipe. If the pipe
is larger, then it will take less time for the water to flow
through (Microsoft.com, 2000). Therefore, the higher the
bandwidth, the greater the amount of information that
can flow through the network to the destination. At the
destination, the speed of the modem or other device used
to connect to the Internet determines the bandwidth of
the stream that is received.Table 1Available BandwidthsTechnology Throughout
Fast Ethernet 100 Mbps
Ethernet 10 Mbps
Cable Modem 8 Mbps
ADSL 6 Mbps
1 ×CD-ROM 1.2 Mbps
Single Channel ISDN 64 Kbps
High Speed Modem 56 Kbps
Standard Modem 28 KbpsBecause video files are large and many networks have
limited bandwidths, there are many issues involved in
transmitting these files over networks. Although many
computer networks have installed new devices and tech-
nology to improve their bandwidths, this is one of the
biggest challenges to streaming a video over a net-
work. The Internet was not designed to handle streaming
video.
File sizes are measured in kilobytes (abbreviated as K
or KB). A kilobyte contains 1,024 bytes. When this conver-
sion is applied to large video files and the math is done to
determine transmission rates, it is apparent that these files
have a huge amount of information that has to be trans-
mitted. For example, a full-screen, full-motion video can
require a data transmission rate of up to 216 Megabits per
second (Mbps) (Compaq, 1998). This exceeds the highest
available data rates in most networks. Table 1 shows the
available bandwidth for several methods of data delivery,
according to Compaq (1998).
In reviewing the above exhibit, it should be noted that
the throughput listed for each technology represents an
upper limit for that technology. In most cases, the actual
throughput will be below this limit due to the amount of
traffic on the network. Depending on the conditions of
their connections, many users will see their data fluctu-
ate up and down. One minute, they may have a 10 Kbps
rate; the next minute, it may jump to 24 Kbps (Kennedy,
2000). Therefore, it is important for the provider of the
streaming video to match the data rate to the conditions
and limitations of the potential users.
Also, the Fast Ethernet and Ethernet technologies
listed in Table 1 are used primarily in businesses and orga-
nizations. Single channel ISDN (integrated services digi-
tal network) is also used by businesses for video phones
and video conferencing. Cable modems and ASDL (asym-
metrical digital subscriber loops) are available to individ-
ual Internet users, but they are newer, more expensive
technologies and are not as widely available as modems.
Thus, it is safe to say that most Internet users have ei-
ther a 56-Kbps high-speed modem or a 28-Kbps standard
modem.
Two options are available for successfully delivering
streaming video over networks. The first option involves
scaling the video to smaller window sizes. This is impor-
tant for low-bandwidth networks where many clients have
modem access. The second option involves compressing
the video using compression algorithms designed for this
purpose. This is needed for most networks because of the