In the list of new features in Silverlight 4, you will find the following:
A webcam and microphone for exchanging video and audio, for example, for chat or customer service applications.
Silverlight captures the sound stream as raw pcm. So, how could you implement, for example, audio / video chat or an application for recording audio to a client / server without any encoding on the client side, where there are no APIs in Silverlight?
Significantly less in Silverlight you cannot use an unmanaged dll. You can use com automation (a new Silverlight 4 feature, I think, only for Windows), but only if it is already installed on the client side (do you know any encoding COM servers that are installed with windows). Otherwise, how would you deploy a custom COM server inside a Silverlight application?
The only way I found is to either deploy the encoding on the command line, or use it with COM AutomationFactory.CreateObject ("WScript.Shell") or implement the encoding to use it in your own AudioSink .