Streaming Video
Streaming video is a sequence of
"moving images" that are sent in
compressed form over the Internet and displayed by the viewer as
they arrive. Streaming media is streaming video with sound. With
streaming video or streaming media, a Web user does not have to
wait to download a large file before seeing the video or hearing the
sound. Instead, the media is sent in a continuous stream and is
played as it arrives. The user needs a player, which is a special
program that uncompresses and sends video data
to the display
and audio data to speakers. A player can be either an integral part
of a browser or downloaded from the software maker's Web site.
Major streaming video and streaming media technologies include
RealSystem G2 from RealNetwork, Microsoft Windows
Media
Technologies (including its NetShow Services and Theater
Server), and VDO. Microsoft's approach uses the standard MPEG
compression algorithm
for video. The other approaches use
proprietary algorithms. (The program that does the compression
and decompression is sometimes called the codec.)
Microsoft's
technology offers streaming audio at up to 96 Kbps and
streaming
video at up to 8 Mbps
(for the NetShow Theater Server). However,
for most Web users, the streaming video will be limited to the data
rates of the connection (for example, up to 128 Kbps with an ISDN
connection). Microsoft's streaming media files are in its Advanced
Streaming Format (ASF).
Streaming video is usually sent from prerecorded video files, but
can be distributed as part of a live broadcast "feed." In a
live
broadcast, the video signal is converted into a compressed digital
signal and transmitted from a special Web server that is able to do
multicast,
sending the same file to multiple users at the same time.
Producing
Streaming Video
That's essentially
all there is to it. When a user clicks the hyperlink, their media player opens
and begins streaming the video file. We'll deal with the specifics soon, but
first we'll have a quick look at specialised
streaming servers.
Streaming media can
be produced in several different ways. We will discuss the two most likely
scenarios for creating your streaming content: live capture and transcoding.
Live capture allows
you to take a video and audio source, such as a video camera or VCR, and
capture it to your computer's hard drive. Your computer will need some sort of
capture device that is compatible with source hardware. Most camcorders have
analog audio/video out jacks that you can plug into your computer's capture
device. Some newer camcorders and VCRs, though, use a digital signal that is
far superior to analog, but requires your computer to also have compatible
hardware.
Transcoding allows you to take existing audio/video files on your
computer and convert them to a streaming format. For example, you may already already have videos that you produced for CD-ROM
distribution. You will need to transcode those videos
to a streaming format before you can stream them.
Sometimes you will
need to use both live capture and transcoding to
create your streaming videos. If you have video editing software on your
computer, such as Adobe Premiere or Apple iMovie, you
will need to capture your video in your editor's preferred format. When you are
finished editing, you will then transcode your movie
to a streaming format.
Many of the software
tools necessary to create streaming media are free, but you will have to pay
for extra features and/or functionality. Hardware for capturing video is
included in some computers such as all of the new Apple Macintosh models as
well as some Windows PCs.