A S t r e a m i n g M e d i a P r i m e r :
H O W D O I M A K E ( G O O D ) S T R E A M I N G M E D I A ?
Adding interactivity to your video production
Streaming allows you to take advantage of the interactivity made possible by the Web. Chapterization
allows viewers to jump to the beginning of a sequence, or chapter, that is specifi ed in your production
with timeline markers. Adobe Premiere and Adobe After Effects also offer the ability to set Timeline
markers that include links to HTML pages. Using these markers, you can develop streaming videos
that automatically launch Web pages at precise points during playback. These URL fl ips may provide
different backgrounds for your video presentation, even titles, or offer additional information that is
relevant to the video content being viewed.
In this example, a URL fl ip provides relevant
information about the bald eagle, that auto
matically pops up in the right hand column of
the Web page, at the moment the bird is seen
in the video.
OUTPUTTING STREAMING MEDIA
A single frame of uncompressed
Encoding compresses and formats media for streaming
video takes about 1 megabyte
You've fi nished editing and assembling your movie. Now it's time to produce the fi nal
(MB) of space to store. You can
fi le or fi les for streaming distribution via the Internet or your intranet. Outputting
calculate this by multiplying the
or exporting your production for streaming requires encoding. Encoding accomplishes
two main objectives: 1) it reduces the size of your video and audio fi les, by means of
horizontal resolution (720 pixels)
compression, making Internet delivery feasible, and 2) it saves your fi les in a format that
by the vertical resolution (486
can be read and played back on the desktops of your targeted audience. Some encoding
solutions may also be confi gured to provide additional processing functions, such as
pixels), and then multiplying
digital watermarking, for example.
by 3 bytes for the RGB color
What is compression?
information. At the standard
The goal of compression is to reduce the data rate while still keeping the image quality
video rate of 29.97 frames per
high. Video for the Web might need to be compressed at a ratio of 50:1 or even more.
second, this would result in
Lossless compression, whereby, no essential data is lost (used for the transmission of
fi nancial data, for example) can compress no more than 30 percent. Fortunately, because
around 30 MB of storage
human perception is based not only on what we actually see and hear, but also on what
required for each and every
we infer, video and audio can withstand lossy compression and still maintain enough
quality to be acceptable. Lossy compression can compress to any level, but the more
second of uncompressed video!
compression is applied, the more quality is sacrifi ced.
It would take over 1.5 gigabyte
There are many different methods of compressing video. One way is to simply reduce the
namic Medianamic Media
(GB) to hold a minute of
size of each video frame. A 320x240 image has only one fourth the number of pixels as a
640x480 image. Or we could reduce the frame rate of the video. A 15 frame per second
(fps) video has only half the data of a 30 frame per second video. Both of these methods
are used to compress video for the Web. For narrowband connections, a very small frame
Adobe Digital Video Primer
obe Dobe D
size usually 240x180 is standard. While larger image sizes are often transmitted via
broadband connections, the recommended frame rate for streaming video is still 15 fps.
43 Creating Audio for the Web, by Steve Cunningham, Streaming Media.com, http://www.streamingmedia.com/tutorials/view.asp?tutorial_id=38
44 Streaming Basics: Editing Video for Streaming, by Tim Kennedy, Streaming Media World, March 8, 2001, http://smw.internet.com/video/tutor/streambasics2/index.html