• Blogs
• Forums
• Tradeshows
• Partners
• White Papers
• Podcast Show Notes
• Events

 

Distribute Expertise: Flash vs. Silverlight

Jun 1, 2008 12:00 PM, By Jan Ozer

Which platform will suit your web-development needs?

Server/player functionality

The final relevant comparison of Flash and Silverlight is as a combination of server- and player-related functions as shown in Table 3. To access these features, you'll need to install one of Adobe's Flash Media Servers or a streaming server from Microsoft. Note that I've included Windows Media and Silverlight under separate columns because many organizations would consider both alternatives and their functionality differs.

Starting at the top, note that Silverlight streams via the HTTP (hypertext transfer protocol), while Flash uses RTMP (realtime messaging protocol) and Windows Media RTSP (realtime streaming protocol). Briefly, HTTP is the generic protocol used to push all information from a web server out to the viewer; RTSP is the industry-standard streaming protocol supported by most streaming servers; and RTMP is a proprietary protocol developed by Adobe for Flash.

Using HTTP for Silverlight has several implications that may or may not be important depending upon the application. Unlike both RTSP and RTMP — which enable true streaming — distributing via HTTP typically means that the file must be cached on the hard drive before playback, where it's easier to capture and pirate. However, if you create a custom Silverlight Player, you can include an option in the player that reads the stream directly without caching — preventing problems associated caching.

In most instances, communicating via HTTP usually prevents bandwidth negotiation, which is why the first version of Silverlight didn't support multiple-bit-rate (MBR) technology. Briefly, MBR lets a streaming server dynamically adjust the bit rate transmitted to the player to match varying throughput conditions, dropping the data rate when packets are lost and increasing the data rate as throughput improves.

However, MBR requires bandwidth negotiation between server and client, which wasn't possible with Silverlight 1.0. It will be available when version 2.0 ships later in 2008, enabling MBR. In March 2008, Microsoft also announced an agreement with Move Networks that will allow adoptive streaming for Silverlight content viewed with the Move Media Player.

Although bandwidth negotiation is available using the RTMP server protocol, Flash previously didn't support MBR functionality. However, with the release of the beta version of Flash Player 10, Adobe announced “dynamic streaming,” which similarly adapts the delivered bitstream to changing line conditions. Note that you'll need a future update for the current versions of the Flash Media Servers to access this feature.

Digital rights management (DRM) is another area where Flash has made significant recent strides. There was no DRM available at all until the launch of Flash Media Streaming Server 3.0. The new family of servers — which shipped in early 2008 — provides multiple options for digital rights management, including SSL encryption, RTMPE realtime encryption, and user authentication.

Although Windows Media has long offered a wide variety of DRM alternatives, including encryption and authentication, the first version of Silverlight shipped without this functionality. At NAB Show 2008, Microsoft announced that Silverlight DRM will be powered by PlayReady — a Microsoft DRM technology that will be backwards compatible with Windows Media DRM. PlayReady will be fully implemented by the time the Silverlight 2.0 player ships later in 2008.

As shown in Table 3, you can stream live to all three players — another relatively new innovation for Flash. However, streaming to the Windows Media Player is the only option for multicast, which is a highly efficient distribution method that allows multiple viewers on a network read the same stream.

The final item on the table reflects Microsoft Silverlight Streaming by Windows Live, which is a free hosting and streaming solution for Silverlight content. Today, users can store up to 10GB on the site and stream up to 5TB of aggregated bandwidth per user account per year. In the future, Microsoft will offer unlimited streaming with advertising, or with payment of a nominal fee for use of the service without advertising. Adobe doesn't currently offer a similar service.

The net

Overall, Flash vs. Silverlight is not a zero-sum game. Organizations faced with a wide variety of programming initiatives will likely find Flash right for some and Silverlight optimal for others. That said, the web-development community is largely composed of Flash fanatics, who harbor a great deal of natural skepticism regarding Silverlight. Microsoft needs to continue to add functionality to its offering, and then the company could do a much better job distinguishing clear usage cases where Silverlight is a better option.

---

To comment on this article, email the Digital Content Producer editorial staff at feedback@digitalcontentproducer.com.

Continue the discussion on “Crosstalk” the Millimeter Forum.
© 2009 Penton Media, Inc.