was being served by a Web server that is, the fi le must download completely before being played from 

the user's hard drive as you know, this is not streaming. 

To differentiate between a downloadable media fi le and a streaming media fi le, a media metafi le is used. 

The link you insert into your Web page points to the metafi le, which is posted on the Web server. The 

metafi le, which is a simple text fi le, invokes the correct media player on the client desktop, locates the 

selected streaming media fi le on the streaming media server and, as the streaming media fi le downloads, 

redirects it from the browser to the media player.

Metafi le extensions and streaming media fi le extensions

Architecture                Metafi le Extensions          Streaming Media File Extensions

RealMedia                    .rpm or .ram                         .rm                                                                        

Windows Media         .asx, .wax, or .wvx               .asf or .wmv (.wma for audio)

QuickTime                    .mov or .sdp                         .mov (sometimes .qt or .qti)

The QuickTime approach is a bit different from RealMedia and Windows Media. In the QuickTime 

architecture, the streaming instructions are embedded right into the movie as a hint track, and the link 

from the Web page goes directly to the streaming server. But some browsers will automatically attempt 

to open an RTSP URL with the specifi ed default player, which may not be QuickTime. To be sure the 

QuickTime player is invoked, a form of metafi le which Apple calls a reference movie can be employed; 

to take advantage of QuickTime's answer to MBR alternate bit rate fi les a reference movie must be 

used. A reference movie is a separate, tiny .mov fi le published on your Web server. When invoked, the 

reference movie calls up the appropriate streaming (i.e., hinted) movie fi le from the streaming media 

server. Live feeds in QuickTime use a more standard metafi le scheme, with a text fi le format called SDP 

(Session Description Protocol); the SDP fi le is published on the Web server and points to the proper 

location on the broadcasting media server.

Integrating streaming media into a rich media experience

 [SMIL] is a simple but powerful 

A Web page is often like a three ring circus, with different things going on, in different 

markup language that lets you 

places, on different timelines. It has been diffi cult for Web developers to synchronize 

presentations comprised of assorted components, especially when those components are 

coordinate the clips so that they each 

served up from different locations via connections that are each subject to their own con 

play how, when and where you want 

gestion patterns. Synchronized Multimedia Integration Language, or SMIL (pronounced 

them to  If you are familiar with 

 smile ), lets Web developers choreograph rich media presentations, including streaming 

other Web based markup languages, 

media, with comparative ease. 

such as HTML, you will pick up 

SMIL, based on the language XML, is reputed to be as easy to learn and use as HTML. 

SMIL quickly. You'll need to be 

It can, of course, be written with a text editor, but there are several convenient SMIL 

editors now available for this relatively new technology. In essence, SMIL is to RTSP and 

careful, though, because SMIL is less 

media servers what HTML is to HTTP and Web servers it is the language that best 

namic Media

forgiving than HTML. Lapses that 

takes advantage of the benefi ts of the streaming protocol. And, as HTML is the standard 

y

may not matter in HTML markup, 

language used to coordinate the content displayed on Web browsers, SMIL is the language 

such as missing quotations marks  

that is rapidly becoming the standard for coordinating the content played on media 

players. Once your  clips  (e.g., video, text, still images, animations, etc.) are encoded in 

will prevent a SMIL fi le from 

their streaming (or other) formats, you assemble your presentation using SMIL. 

obe D

working properly.  

d

 SMIL Basics

The end user must have an SMIL enabled media player or browser to take advantage 

A

realnetworks.com

54

of SMIL fi les. The latest versions of all three dominant architectures' players and several 

others', as well as the newest version of Internet Explorer, are compliant.

37

55   http://www.realnetworks.com/devzone/tutorials/authoring/smil/smil_basics.html