A S t r e a m i n g M e d i a P r i m e r :
W H A T I S S T R E A M I N G M E D I A ?
Traditional download lets you save and redistribute media
I S F L A S H S T R E A M I N G ?
The downloadable approach is good for the end user who wants to keep the content and
replay it whenever they like. In 1999, the phenomenal popularity of the 2 1/2 minute
The Macromedia Flash (SWF) format
movie trailer for Star Wars: The Phantom Menace a whopping big 25 MB fi le at
was designed to deliver low bandwidth
480x216 resolution (good quality) was proof that media hungry Internet audiences are
motion graphics specifi cally for the Web.
willing to be forgiving of long waits for large fi les. But if an artist or publisher does
It's great strength lies in generating
smooth vector animations.
not want end users to be able to save and freely redistribute their media content, the
downloadable approach is problematic that's the story of MP3s and Napster.
According to our defi nition of true
streaming, Macromedia Flash anima
Progressive download can get hung up
tions and other SWF format fi les are not
Unlike traditional download, progressive download (also known as pseudo streaming
streaming media. However, SWF fi les do
and, in QuickTime, fast start streaming) allows playback to begin before the fi le is
share some of the important character
completely downloaded. Progressive download allows playback of content that has been
istics of streaming media.
received to continue, while the remainder is still being downloaded. Progressive down
SWF fi les do:
load, therefore, allows the end user to view the beginning of the fi le, as the remainder is
Deliver content with motion and
being downloaded, and to quit the download if the content is not worth the wait.
sound, as well as with interactivity
Like streaming, progressive download does allow audiences to see and hear the content
However, SWF fi les do not deliver full
immediately as it is being downloaded but only if the download speed can be main
motion video. AVI and MPEG fi les cannot
tained at the rate needed to keep up with playback. If the Internet connection becomes
be imported into Flash. QuickTime
busy, causing the download to slow or stall, audio and video playback may not always
(MOV) fi les can be imported, but do not
become part of the Flash fi le and cannot
stay synchronized, playback may become choppy or, as is often the case, may come to a
be viewed with the Flash player. A utility
halt, as the player waits for the download to catch up.
can be used to reduce a video fi le to a
Progressive download also leaves a copy of content behind
sequence of still bitmap images which
can then be used in a series of key
Unlike streaming, progressive download writes the media fi le to disk, leaving a copy of
frames to simulate video, but the
the content in the memory of the receiving device. Streaming media is processed, played,
resulting movie does not deliver the
and discarded, leaving no physical copy behind.
same quality as streaming video opti
Despite the drawbacks of progressive download, it can be a good alternative if true
mized in a native streaming fi le format
streaming is not possible. Progressive download can be easier and less costly to imple
and played back on a video player.
Furthermore, Flash fi les are limited in
ment than true streaming. All the production techniques described in this Primer should
size to 16,000 frames. At 15 frames per
be applied to preparing media for progressive download, as well as for streaming.
second, that's approximately 17 minutes
True streaming is based on a different architecture
worth of material.
Streaming media requires a different architecture from that used for downloadable
Begin to play before the fi le is
media an architecture that supports a higher level interactivity over the Web, and offers
a wealth of additional advantages. Streaming allows you to browse through and jump
However, SWF delivery is really pro
back and forth in the content as opposed to progressive download, which requires
gressive download. Served from a Web
server and transmitted via HTTP, Flash
viewing from beginning to end. Streaming supports both on demand and live content
playback will stall if network congestion
to be transmitted over the Web in real time, allowing audiences anywhere in the world
is encountered, and transmission cannot
to playback media whenever and however they need or want it, and to experience live
be adjusted to accommodate real time
events as they happen.
conditions as can true streaming.
True streaming requires a specialized media server
Can only play back using the media
Downloadable media fi les including those prepared for progressive download are
player that is part of the Flash
typically served from a standard Web server that does not have any ability to adjust
transmission to the uncontrollable fl uctuations in connection speed that are inherent in
However, SWF fi les can be created using
a variety of other software tools in
the Internet environment.
addition to Macromedia Flash, including
Streaming exploits new Web transfer protocols, as well as communication techniques
but not limited to Adobe LiveMotion
between clients and servers, to facilitate the continuous playback of synchronized audio
and Adobe After Effects.
and video in real time. Streaming media fi les are usually encoded in several versions,
According to the Macromedia Web site,
optimized for different data rates. The streaming media server delivers the appropriate
Flash was created to make small,
version, either as selected by the end user manually or as indicated by browser default
streamable, vector based fi les for Web
settings. In some cases, the server can automatically select the best version, based on
delivery. This is where Flash performs
information brought back from the client regarding the platform and the connection
best. it's important for users to ask
themselves, `Is this program designed to
speed. Depending on the intelligence built into the media server and client player
do what I am attempting''
software, the stream can be dynamically adjusted, at one or both ends, if the
connection slows down.