Installation guide

Progressive download video delivery

SinceFlashMX2004,progressivedownloadhasbeensupportedforvideodelivery.ismethod

allows developers to load external video les into a Flash or Flex interface and play them back

during runtime. is can be accomplished using ActionScript commands with the Video object

or playback components, or by setting parameters for the playback components in the authoring

environment, as shown in the following gure.

Parameters set for an FLVPlayback component to stream an external video le into a SWF

When the video is played, the video le rst begins to download to the user’s hard drive, then

playback starts. e video begins to play when enough of it has downloaded to the user’s hard

drive. e le is served from a standard web server through an HTTP request, just like a normal

web page or any other downloadable document.

Incomparisontostreamingvideo,there’sreallyonlyoneconsistentbenettoprogressive

download—youdon’tneedastreamingservertodeliverthevideo.Progressivedownloadvideocan

be served from any normal web server. While this can be convenient and potentially cost-eective,

you should keep in mind that progressive downloads have limited seek and navigation capabilities,

anduserscanaccessandrepurposeyourcontent.Insomesituations,suchasplaybackbehindvery

strictnetworkrewalls,streamingdeliverycanbeblocked.Inthesecases,rollbacktoprogressive

delivery can be desirable.

When to choose progressive download

Progressive download is a good choice for hobbyists or websites that have low trac requirements,

if they don’t mind if their content is cached on a user’s computer, they only need to deliver videos

lessthan10minuteslong,ortheirvisitorscannotreceivestreamingvideoforsomereason.You

must stream your video if you need advanced features and control over video delivery, or if you

needtodisplayvideotolargeraudiences(forexample,severalhundredsimultaneousviewers),

track and report usage or viewing statistics, or if you want to oer your viewers the best interactive

playback experience. Streaming delivery also consumes less bandwidth than progressive delivery,

because only the portion of the video that is watched is actually delivered.