Silverlight vs. Flash

With the rocket development of Internet, the techniques used for building web pages is improving all the time, which not only brings people more information but new experience of surfing on the Internet. Many techniques have been applied to enrich the web page these years, from totally the plaintext in early 90's, first to web page with pictures and then that with embedded sounds. Later, Sun Microsystems proposed Java Applet, which was popular for not long time until being conquered by Adobe Flash. Now Microsoft proposed Silverlight technology. Some people say that Microsoft made a wrong decision while others claim that Silverlight will kill Flash at last. According to the next step in the value chain, for Flash, it focus on building rich applications with Flex. For Silverlight, Ajax is becoming the way to add more value.

(CC) Image: Ganggang Hu
Made by Ganggang Hu, 2008

Technology

When it comes to general technology features, both Flash and Silverlight have the same functions and benefits as follows:

• Rich 2D animation/graphics with audio and video
• Choice of standards-based and high-performance languages
• End-to-end server and application platform
• Client side playlists for ad-insertion
• Robust video publishing tools
• High-performance, multi-core enabled lightweight client
• Data exchange with web server
• Easy installation support for platform requirements
• Tools product line integrity
• Multiple browsers support such as IE, Firefox, Safari and Opera

On the other hand, both of them have their unique features. For example, Flash has offline document support, rich set of control library and test tools. While Silverlight has hardware-assisted editing and encoding solutions, XML-based presentation for Search Engine Optimization (SEO), and content access protection, Digital Rights Management (DRM).

Below is the table of technology comparison between Flash and Silverlight.

	Silverlight	Flash
Animation manipulation	time based	frame based
Video codec	industry standard VC-1 codec	no industry standard
Audio decoder	MP3, WMA, WMV	MP3
Binary or text file	XAML text based and XML object	SWF binary shape records
Platform support	Windows, Max OS X, Linux (Moonlight), Mobile	Windows, Max OS X, Linux, Mobile
Programming tools	Visual Studio, Expression Studio	ActionScript

Animation manipulation

Flash is frame based, which requires users to compute the duration of an animation. For example, there are 12 frames per second in Flash animation model. If users want an object to move 5 seconds continuously, they need to calculate how many frames 5 seconds will take. Also, the player doesn't maintain any frame rate unless users embed blank audio tracks.

Instead of frame based, Silverlight supports the time based WPF animation model, which allows users to define the start and end conditions without calculating positions on various frames. Then Silverlight can generate animation process automatically.

Additionally, when create animation, the Adobe suite of products can easily share objects and files between applications such as Illustrator, Flash, Dreamweaver, Photoshop, etc. While Silverlight has these options built into it already along with several other tempting products such as ad-insertion and free streaming solutions.

Video codec and audio decoder

Flash supports multiple video formats with high quality codec and nice bandwidth usage, such as scalable full screen video up to HD(720p). The price of its media server licensing(unlimited bandwidth) is only one forth of that of Silverlight. But except that its Sorenson’s proprietary H.263 implementation is loosely based on a standard, Flash has no industry standard video codec yet. Also, the audio formats Flash supports are all proprietary, except for MP3 and ADPCM, whose quality of compression is not so impressive, and still requires licensing fees and third party conversion libraries.

Compare to Flash, Silverlight implements industry standard VC-1 codec for video, as well as offering support for WMV and WMA. Microsoft makes available a free Encoder SDK for producing WMA and WMV so that people are able to encode by themselves with easier integration and cheaper cost.

Here is a comparison of video codec between Flash and Silverlight using different computer systems.

	Flash VP6E	Flash VP6S	Flash H.264-High	Silverlight
PowerMac Dual 2.7 GHz PPC G5, OS 10.4.11, FireFox, Flash Player 9.0.115.0, SL 1.0.30401.0
Processor(percentage of 2 processors)	72.0%	66.3%	85.8%	108.0%
Drop frames	no	no	yes	yes
Estimated frame rate	full	full	5-6 fps	1-2 fps
Drop audio	no	no	yes	no
HP xw4100, 3.0 GHz P4 with HTT, Windows XP, FireFox Flash Player 9.0.124, SL 1.0.30401.0
Processor	87.5%	97.1%	NA	NA
Drop frames	yes	no	yes-stopped	yes-lost synch
Estimated frame rate	2 fps	full	stopped	1 frame/3 seconds
Drop audio	yes	no	yes	yes
HP 8710P, 2.2 GHz Core 2 Duao, Vista, IE, Flash 9.0.124.0, SL 2.0.30226.2
Processor	51.9%	52.0%	34.8%	47.3%
Drop frames	no	no	no	no
Estimated frame rate	full	full	full	full
Drop audio	no	no	no	no
Dell Precision 390, 2.9 GHz Core 2 Duo, XP, IE, Flash 9.0.124.0, SL 2.0.30226.2
Processor	22.7%	17.5%	7.7%	26.0%
Drop frames	no	no	no	no
Estimated frame rate	full	full	full	full
Drop audio	no	no	no	no

Binary or text file

Flash stores shapes using binary shape records. In order to write shape definitions, users need to either license a third party Flash file format SDK, or build libraries by themselves. While Silverlight uses text based XAML, which can be output using an XML object. So users don't need to buy special libraries or write their own libraries.

Flash stores fonts glyphs using the same exact shape definitions that are used for any other shape. The player does not understand TTF files, so users need to use the Win32 APIs to figure out intricacies of fonts in the Flash file format documentation by themselves. But in Silverlight, WPF/E lets users embed true type font information directly into projects, and download that information with the downloader object without doing extra work.

However, with the capability of compiling down into a binary, Flash can actually starts executing before it is fully downloaded, which is one of the serious benefits to using binary SWF and more satisfying than the pure text files in Silverlight, which brings the runtime from zero to hero before one can do anything. Furthermore, Flash has plenty of functionality encapsulated in the runtime. It has its own JIT compiler, its own language ActionScript and a healthy set of controls. But Silverlight uses JavaScript as the scripting language and depends on the browser for most of the interaction processing.

Platform support

Flash integrates with multiple platforms and languages. It supports Windows, Max OS X, Linux and also moblie platforms. While Silverlight has some limitations on this aspect. It mainly supports Windows and Max OS X. Silverlight looks to be as far as Microsoft has ever gone as a company to embrace cross-platform and yet they still fail to support Linux. However, a newly developed project called Moonlight by Mono open source project sponsored by Novell allows Linux users to run Silverlight applications on Linux, provide a Linux SDK to build Silverlight applications and reuse the Silverlight engine built by Mono for desktop applications. Written with a combination of C++ and C# code, Moonlight for Linux Supports Silverlight 1.0 was first released in May, 2008. Also, Silverlight is spreading to mobile platform by building various applications on mobile devices. The only hope for Silverlight is to make the runtime open source and cherish the hope for consistent cross-platform support, though Microsoft has a terrible cross-platform track record as a company and most of the company's prior efforts have been deprecated.

Programming tool

Microsoft provides a handful amount of programming tools to support its Silverlight. Visual Studio 2005 (supports Silverlight 1.0) and 2008 (supports Silverlight 1.0 and Silverlight 2.0), and Expression Studio are the main programming tools that developers can use to build Silverlight animations/applications. Programming languages which are supported by Silverlight are JavaScript, Visual Basic, and C#.

Adobe also provides its own developing tools to assist developers in creating Flash animations/applications. Such tools are Adoble Flash and Adobe Flex. However, compare to Silverlight, programming language supported by Flash is very limited. It is only supported by ActionScript.

Market

According to a survey given by Adobe System in June 2008, 99% of computer users have installed Flash Player. But until then, there was still no official statistics about Silverlight given by Microsoft.

This significant difference of market share between Flash and Silverlight may due to following reasons:

• Silverlight was released as 1.0 in 2007 while Flash 1.0 was released in 1996. Flash already has sufficient time to grow, thrive and dominate the media plug-in market before Silverlight was born. One way for Microsoft to increase the number of Silverlight users is to include Silverlight in Internet Explorer.
• Users choose to view content built in Flash and therefore need the plug-in. Since Silverlight is still new, there is relatively little knowledge of its existence (among non developers) and application created in it. Microsoft is providing more Silverlight content, such as the NBC online 2008 Olympic Games.

Although Silverlight has many advantages over Flash, it pales in front of Flash in terms of availability. It is not a unique Microsoft problem but a problem for every new offering when there is an incumbent who has a majority market share. Because Flash is so ubiquitous that it pushed QuickTime, Real Player, and windows movie files right out of the web space. As a juvenile in market, Silverlight may need a long time to get acceptance for itself.

See also

• Microsoft Silverlight
• Adobe Flash