FAQ
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General questions

    What is Microsoft Silverlight?
Microsoft Silverlight is a cross-browser, cross-platform, and cross-device plug-in for delivering the next generation of .NET based media experiences and rich interactive applications for the Web. By using Silverlight's support for .NET, High Definition video, cost-effective advanced streaming, unparalleled high-resolution interactivity with Deep Zoom technology, and controls, businesses can reach out to new markets across the Web, desktop, and devices.
    Is Silverlight free?
Yes, Microsoft has made the Silverlight browser plug-in freely available for all supported platforms and browsers.
    What is the long-term goal or vision for Silverlight?
Microsoft Silverlight is a cross-browser, cross-platform, and cross-device plug-in for delivering the next generation of .NET based media experiences and rich interactive applications for the Web. Silverlight offers a flexible programming model that supports AJAX, VB, C#, IronPython, and IronRuby, and integrates with existing Web applications. By using Expression Studio and Visual Studio, designers and developers can collaborate more effectively using the skills they have today to light up the Web of tomorrow. By leveraging Silverlight's support for .NET, High Definition video, cost-effective advanced streaming, unparalleled high-resolution interactivity with Deep Zoom technology, and controls, businesses can reach out to new markets across the Web, desktop, and devices.
    What is new in Silverlight 2 Beta 2?
  • UI Framework: Silverlight 2 includes a UI framework that makes building rich Web applications much easier. It provides a powerful graphics and animation engine, as well as rich support for higher-level UI capabilities like controls, layout management, data-binding, styles, and template skinning. Silverlight 2 is a compatible subset of the features in the full .NET Framework, and enables developers to re-use skills, controls, code and content to build both rich cross browser web applications, as well as rich desktop Windows applications.

    Beta 2 includes improvements in animation support, error handling and reporting, automation and accessibility support, keyboard input support, and general performance. This release also provides more compatibility between Silverlight and WPF.
  • Rich Controls: Silverlight 2 includes a rich set of built-in controls that developers and designers can use to quickly build applications. This release includes core form controls (TextBox, CheckBox, RadioButton, etc), built-in layout management panels (StackPanel, Grid, Panel, etc), common functionality controls (Slider, ScrollViewer, Calendar, DatePicker, etc), and data manipulation controls (DataGrid, ListBox, etc). The built-in controls support a rich control templating model, which enables developers and designers to collaborate together to build highly polished solutions.

    Beta 2 includes a new templating model called Visual State Manager that allows for easier templating for controls. Other features include the introduction of TabControl, text wrapping and scrollbars for TextBox, and for DataGrid additions include Autosize, Reorder, Sort, performance increases and more. Most controls are now in the runtime instead of packaged with the application.
  • Networking Support: Silverlight 2 includes rich networking support. It includes out of the box support for calling REST, WS*/SOAP, POX, RSS, and standard HTTP services. It supports cross domain network access (enabling Silverlight clients to directly access resources and data from resources on the web) and built-in sockets networking support.

    Beta 2 includes improved Cross Domain support and security enhancements, upload support for WebClient, and duplex communications ("push" from server to Silverlight client).
  • Rich Base Class Library: Silverlight 2 includes a rich .NET base class library of functionality (collections, IO, generics, threading, globalization, XML, local storage, etc). It includes rich APIs that enable HTML DOM/JavaScript integration with .NET code. It also includes LINQ and LINQ to XML library support (enabling easy transformation and querying of data), as well as local data caching and storage support. The .NET APIs in Silverlight are a compatible subset of the full .NET Framework.

    Beta 2 includes improved threading abilities, LINQ-to-JSON, ADO.NET Data Services support, better support for SOAP, and various other improvements to make networking and data handling easier.
  • Deep Zoom: The new Deep Zoom technology in Silverlight 2 Beta 2 allows users to see images on the Web like they never have before. The smooth in-place zooming and panning that Deep Zoom allows is based on advanced technology from Microsoft Research and raises the bar on what image viewing should be. For the Silverlight developer, using a Deep Zoom image is really simple since it behaves like any other image in Silverlight and can be manipulated with standard Silverlight metaphors such as Storyboards.

    Beta 2 introduces a new XML-based file format for Deep Zoom image tiles, as well as a new MultiScaleTileSource that enables existing tile databases to utilize Deep Zoom. Better, event driven notification for zoom/pan state is another improvement in Silverlight 2 Beta 2.
    Which platforms and browsers will Silverlight 2 support?
Silverlight will support all major browsers on both Mac OS X and on Windows. Particular care is being taken to account for differences in platform and browser capabilities to ensure a consistent experience including experiences on Firefox, Safari, and Internet Explorer. Microsoft will extend the support for Silverlight on Linux through a partnership with Novell.
    How will Silverlight be distributed by Microsoft?
Microsoft designed Silverlight to fit a broad range of uses that require reach and a compelling user experience. Both third-party customers around the world and internal customers at Microsoft continue to embrace Silverlight. Examples of worldwide third-party customers and partners include ET Online, NBA, Major League Baseball, World Wrestling Entertainment, Home Shopping Network from USA; QuickSilver from France; BMW and Vodafone from Germany; Miniclip and British Library from UK; Baidu from China, to name a few. Examples of internal Microsoft customers include are MSN, Halo 3, and www.microsoft.com, which are leading global websites that serve millions of customers worldwide. In addition, Microsoft Update and Windows System Update Service also serve as Silverlight distribution channels. And this is just the beginning. With an exciting customer pipeline, like the Beijing 2008 Olympics, Silverlight is clearly on an upward rising adoption curve.
    Will I need more memory, a faster processor, or a better Graphics Processing Unit (GPU)?
Microsoft designed Silverlight with the ability to deliver high-fidelity experiences on the broadest set of system configurations. Some features, such as HD video, may benefit from newer personal computers. Final system requirements will be available at release.
    Which devices will be supported?
Device support is coming soon.
    How do I verify Silverlight is installed?
Verify your installation by visiting the Silverlight installation page.
    How can I deploy Silverlight on my corporate network?
The Silverlight Deployment Guide thoroughly details all the steps for rolling out Silverlight on a corporate network.

Development related

    Can I redistribute Silverlight 2 Beta 2 release?
The Go-Live license enables developers to begin deploying new Silverlight 2 applications, as well as deploying updated versions of existing applications.
    What exactly is a Go-Live license?
A Go-Live license gives developers and organizations authorization to begin deployment of their applications using pre-RTM code. Our primary recommendation is for developers to use the Go-Live license and the Silverlight 2 Beta 2 to begin building applications with the knowledge that Microsoft will be updating the bits in the future.
    Should developers/organizations wait until Silverlight 2 RTW to build applications?
As with all pre-release software organizations should proceed knowing that things can change. While Microsoft does everything to ensure every Beta reaches a high quality bar, Beta 2 is not meant for mission critical applications. Microsoft recommends that companies begin to experiment and build with the Beta to make sure applications are ready to deploy on subsequent releases.
    What is in Silverlight 1 that is not in Silverlight 2?
Nothing, Silverlight 2 is a full superset of Silverlight 1.0 – it is 100% compatible with Silverlight 1.0 applications and provides significantly more powerful features and functionality. Silverlight 1.0 applications even benefit from improvements in media playback and performance characteristics of Silverlight 2 with no additional work.
    Does the recently released Visual Studio 2008 and Expression Blend work with Silverlight 2 Beta 2?
Yes.
To build content that targets the Silverlight 2 Beta 2 you should install the Expression Blend 2.5 June 2008 Preview.
You will also need the Silverlight 2 Beta 2 SDK, unless you install the tools for Visual Studio mentioned below. Visual Studio 2008 also supports Silverlight 2 Beta 2 by installing Microsoft Silverlight Tools Beta 2 for Visual Studio 2008. This includes the Silverlight 2 Beta 2 SDK.
    Where can I find Silverlight and associated Software Development Kits (SDKs) for download?
The Silverlight installer and tools for Designers and Developers can be found on the Tools page. The Silverlight community site is also a great resource for developers to find additional resources and get started.
    Are the features of the Macintosh and Windows releases of Silverlight fully compatible?
Yes.
    When would a customer use Silverlight instead of ASP.NET AJAX?

Silverlight integrates with existing Web applications, including ASP.NET AJAX applications. Consequently, ASP.NET AJAX and Silverlight are designed to be complementary technologies. In the broader sense, Silverlight can talk to any AJAX application, both client-side and server-side. ASP.NET AJAX can additionally be used to control Silverlight-based visualization of data or delivery of rich experiences. Examples might include mapping applications or video playback with rich presentation.

ASP.NET AJAX and Silverlight at final release will also benefit its status as a fully supported technology from Microsoft with the benefits of technical support around the clock and the breadth support of the Microsoft development community. AJAX is a fundamental technology supported in Silverlight and now, in ASP.NET.

Customers can enhance existing ASP.NET or ASP.NET AJAX applications by using Silverlight's media experiences and RIAs.

    How does Silverlight make the Microsoft development system better?
Silverlight is a cross-browser, cross-platform plug-in for delivering the next generation of media experiences and rich interactive applications (RIAs) for the Web. Examples include:

For ASP.NET-based Web applications, Silverlight provides a rich UI front-end that, with a consistent programming model, adds support for richer interactivity, media, and audio.
For Microsoft SharePoint–based content, Silverlight offers the ability to create rich Web parts.
For Windows Live services, Silverlight offers the ability to consume services and APIs more effectively.
    When would a customer use Silverlight versus Windows Presentation Foundation? Is Silverlight for a certain type of application?
Microsoft recommends the Windows Presentation Foundation for building rich immersive applications and experiences that can take full advantage of the Windows platform, including UI, Media, offline communication, OS integration, Office integration, peripheral access, Document support and more. Silverlight will be used for broad reach interactive media content and browser-based rich interactive and high-performance applications and experiences.
    What features are missing from Silverlight presentation markup that will be supported in the Windows Presentation Foundation?
Some areas that will not be a part of Silverlight include the support for 3D and GPU rendering found in the .NET Framework. However, we are working hard to make Silverlight a perfect subset of WPF functionality making it possible to easily reuse code, assets, and tools for building applications.
    Where can I go to connect with other Silverlight developers to ask questions?
For Silverlight-related forums, blogs, and community resources for the CTP, visit the Silverlight Support and Community page.

Media (audio and video)

    Is Silverlight a new media player?
No. Silverlight is a cross-browser, cross-platform plug-in for delivering media experiences and RIAs. It is not a desktop application or stand-alone media player.
    What is the relationship between Silverlight and Windows Media Player?
The Silverlight browser plug-in is a separate component, independent of Windows Media Player. Silverlight is designed for delivery of cross-platform, cross-browser media experiences and rich interactive applications (RIAs) inside a Web browser combining audio, video, animation, overlays, and more. Windows Media Player delivers a breadth of local playback and user focused experiences, while also offering support for application and Web page embedding.
    Do I need to have the latest version of Windows Media Player installed?
No. Silverlight is completely independent and when installed is less than 4 MB in size.
    What audio or video formats are supported in Silverlight?
Silverlight supports Windows Media Audio and Video (WMA, VC-1/WMV7–9) as well as MP3 audio. Additional formats may be available over time based on customer feedback.
    Will Silverlight support all the codecs Windows Media Player supports?
Since Silverlight is a lightweight cross-platform technology, it only carries the most common codices that are needed for Web playback. However, we are gathering information from customers about the needed codecs and can update Silverlight when necessary.
    What is SMPTE VC-1?
VC-1 is an industry-standard video format, recognized by the Society of Motion Picture and Television Engineers (SMPTE). Windows Media Video 9 (WMV-9) is the Microsoft implementation of the SMPTE VC-1 standard video codec. Microsoft initiated development of the standard with the release of WMV-9 to SMPTE.
    Does Silverlight support HD quality?
Yes, Silverlight supports 720p, HD quality with considerable performance benefits over other solutions. Performance is dependent upon the central processing unit (CPU) capabilities of your computer and configurations. Generally, in testing, a 3-gigahertz (GHz) CPU and/or dual-core support greatly benefit the HD playback experience.
    Will Silverlight work with my new or existing Windows Media services platform for streaming?
Silverlight takes advantage of Windows Server features for streaming.
    Will Silverlight support live streaming events as well as downloading media?
Yes. Silverlight together with Windows Media Services enable live streaming experiences.
    Does Silverlight support MPEG4 and H.264 video, or Advanced Audio Coding (AAC) audio, or Flash video?
No. However, content from many of these formats can be transposed into formats that are supported by Silverlight, such as by an automated server function (many available third-party solutions support this workflow), and then incorporated into a Silverlight-based application. However, we are gathering information from customers about the needed codecs and can update Silverlight when necessary.
    Does Silverlight support digital rights management?
Silverlight 2 supports key online protected content distribution scenarios including live streaming, on-demand streaming, and progressive download through Silverlight DRM, Powered by PlayReady. For more information visit our Silverlight DRM pages.
    Will Silverlight-based applications run in Media Center? What about Media Center Extender?
Silverlight-based applications can run in Media Center but may have rendering issues on Media Center Extenders. Applications that are implemented using the Media Center SDK will provide a better experience. The engineering team is actively evaluating customer requirements for a variety of scenarios moving forward.
    Are there any new tools for creating and publishing media content with Silverlight?
Yes. Expression Encoder, a feature of Expression Media, will support live and on-demand encoding and template-based publishing of Silverlight media experiences. In addition, Silverlight works with the broad range of Windows Media encoding tools and utilities available today.

Server

    Will Silverlight-based applications and content run on any Web Server?
Silverlight works with any Web server just like HTML does. Video and audio content can also be progressively downloaded and played back from any Web server platform.
    Is Microsoft making new server investments for creation and delivery of digital media?

The recently released Windows Server 2008 is the next-generation server operating system from Microsoft that will help content providers realize new levels of reliability and scalability, all with lower-cost content delivery. With the release of Windows Server 2008 we have made significant investments in two key areas : IIS 7.0 Media Pack for delivering media via progressive download from a web server and Windows Media Services 2008 for live and on-demand streaming from a dedicated streaming media server.

To deliver streaming media, customers can use Windows Media Services (WMS) 2008. Windows Media Services 2008, like all of Windows Server 2008, is significantly more secure, reliable and robust. Windows Media Services 9.0 was already considered by many customers to be the best in the market for live and streaming delivery, and the latest improvements provide up to 2x scalability increases.

Silverlight joins the list of client platforms that can connect to and present WMS streamed audio and video as an integrated part of media-enabled applications for the Web, whether you are building a simple cross-platform, browser-based media experience or a rich internet application (RIA) for the Web.

For delivering content from a web server, also known as progressive download, we are introducing the Internet Information Services (IIS) 7.0 Media Pack, a new set of features designed to reduce Web server media delivery costs. The first shipping feature of the IIS 7.0 Media Pack is Bit Rate Throttling, which gives administrators the ability to control the amount of media that is delivered to the client. By controlling media delivery, Bit Rate Throttling reduces bandwidth costs, streamlines network traffic and increases concurrent connections. The next feature in the IIS7.0 Media Pack is Web Playlists, a server-side playlist solution for progressively download media.

    What is streaming? What is progressive download?

Streaming occurs when an active connection exists between the client application and the server. Content can be on-demand or live. On average, the cost of delivery of streamed content is lower since only those portions actually viewed are delivered.

Progressive download traditionally refers to the send-and-forget download of an on-demand audio or video file to the client. It is simple to implement with only a Web server, which can be attractive for existing Web infrastructures. The new IIS Media Pack Bit Rate Throttling feature allows you to do progressive downloads from IIS with increased scalability and reduced bandwidth costs.

Globalization and localization

    What UI languages does Silverlight provide?

In the Beta, the installation and control runtime are available in English, French, German, Spanish, Italian, Chinese Simplified, Chinese Traditional, Korean, and Japanese, for Windows only, as well as English on the Mac. Developers may provide an in-page "Get Microsoft Silverlight" experience for their customers in English, French, German, Spanish, Italian, Chinese Simplified, Chinese Traditional, Korean, and Japanese. Support for additional languages is planned to follow.

Silverlight 2 Beta 2 introduces support for end to end application localization via one xap per supported locale.

    Does Silverlight support East Asian languages?
In the Beta, there is full support of East Asian languages via TextBlock element. TextBlock supports and uses the East Asian fonts installed on the user's machine. In addition TextBlock supports surrogate content as well as handling proper line breaking for East Asian text. For text input, Silverlight 2 Beta 2 supports East Asian text entry via an IME.
    Does Silverlight support bi-di or complex scripts?
In the Beta, Silverlight does not support the bi-directionality, shaping or justification support required by complex script languages. A developer, however, may utilize the rendering of the browser (DHTML) or text-graphics as alternative approaches.

Silverlight streaming service

    What is Microsoft Silverlight Streaming by Windows Live?
Microsoft Silverlight Streaming by Windows Live offers a free cloud-based hosting and streaming solution for quickly delivering high-quality, high-scale, cross-platform, cross-browser, media-enabled RIAs.
    How much does Silverlight Streaming cost?
While the service is in beta, storage is free up to 10 GB and streaming is free up to 5 TB of aggregated bandwidth per user account per year. Videos should not exceed 10 minutes and have a maximum bit rate of 1.4 Mbps. As we move out of beta, unlimited streaming will also be available for free with advertising, or with payment of a nominal fee for use of the service without advertising.
    How much is the pay-for-use service if I chose not to use Microsoft-sponsored advertising?
We're not prepared to discuss the final pricing of the non advertising-based product at this time except to say that it will be extremely cost competitive. The advertising-based product will continue to be free in perpetuity.
    Can this service be used for non-video files such as music files?
Yes. Anything that can be encoded as Silverlight application content and rendered in Silverlight can be used. This includes music files such as WMA and MP3. Business logic written in .NET and JScript can also be stored and streamed to the client.
    How much storage do I get and what is the bit rate?
A user receives 10 GB of free storage for Silverlight applications hosted in Silverlight Streaming. Videos should not exceed 10 minutes and have a maximum bit rate of 1.4 Mbps. There is also a byte size-based limit set to 105 MB for all file uploads. For video files, the first limit to be reached –either based on the video length or on the video file size– will be applied. In any case, if the limit is exceeded, the upload will fail.
    What video encoding formats are supported?

The designer or developer is free to use any encoding format for their video supported by the Windows Media Video codec. This includes Variable Bit Rate (VBR) encoding for DVD-quality video and the use of the VC-1 codec for high-definition content. Remember that the optimized output rate from the service is 1.4 megabits per second.

Silverlight Streaming also provides transcoding in the cloud if the user chooses the Manage Video scenario. In that case, a wide variety of formats are supported in input, and a high quality WMV file encoded at 1.4 Mbps with VC_1 codecs will be generated as output. The technical details of the profile used by the Silverlight Streaming transcoding service are provided in the SDK on http://dev.live.com/silverlight.

    What is the difference between Silverlight Streaming and other video sharing services?
Silverlight Streaming is focused on developers who want to build their own media-rich applications or Web sites. Unlike other video sharing services, there are no third-party branding requirements for the use of Silverlight Streaming, and the developer is in full control over their rich media experience within the context of their Web site. This includes items that are not presently supported on other sites such as 16:9 aspect ratio video, DVD-quality video, stereo audio, and customized UI (XAML).
    Does Silverlight Streaming replace other video and file sharing services?
This service does not replace other video or file sharing services. Silverlight Streaming is intended to give developers the power and flexibility to build such services themselves, and more.
    What steps are being taken to ensure copyrighted content or illegal material is not uploaded?
The media owners as well as the Silverlight developers rendering content in their third-party Web sites are responsible for respecting the copyright of the content they expose. Microsoft reserves the right to remove from our servers any copyrighted content brought to our attention. The front page of our service has a Report Abuse link.
    Can I string together longer clips made of 10-minute files in a playlist?
Yes, so long as the total size of your Silverlight application content does not exceed the 10 GB storage quota of this free service, each video clip is encoded at a maximum bit rate of 1.4 Mbps, and each video file is not larger than 105 MB.
    What scalability does this system deliver? What if I have a large number of visitors to my Web site at the same time?
This service uses the Microsoft content delivery network specifically optimized for long-form video content. It has a provisioned global aggregate data rate in excess of 1 terabit/second.
    Does this solution compete with content delivery networks (CDNs)?
No, this service uses the Microsoft CDN for the low latency delivery of media and does not compete with CDNs because it is specifically optimized for use with Silverlight RIAs.
    Why is this service branded with Windows Live?
This service is part of the Windows Live Platform.
    It's free — what's the catch?
There is no catch. This is a new offering designed to accelerate the development of the next generation of Silverlight applications in general and media rich applications in particular.
    Can I tap into other Windows Live services?
Yes, customers are able to use Windows Live ID and other Windows Live APIs today and in the future. Silverlight provides a great platform to consume these services.
    What applications will Microsoft provide to make hosting easy?
Microsoft is building a simple uploading tool and has enabled direct publishing to the Silverlight Streaming service via an Expression Encoder publishing plug-in available on the Microsoft download center. In addition, third-party companies are adding support to their own applications for Silverlight Streaming integration.
    How is my content secured?
You will have to be signed into the Silverlight Streaming service to manage your account and your Silverlight applications. Your Silverlight Streaming account ID and secret key, associated to your Windows Live ID, will authenticate you as the unique and legitimate owner of the applications and content you upload to the service. You will also need Silverlight Streaming account ID to render your applications on your Web site. The Silverlight Streaming ID is public. However, the secret key should be kept confidential.
    How do I get started?
To sign up for your free account, visit silverlight.live.com. Anyone with a Windows Live ID can participate.