C# Windows Store App microphone playback

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C#

Windows

audio

Hey, I'm really stumped on this and it just seems like I'm missing something obvious.

I'm trying to implement a feature in a C# windows store app that allows you to speak through the microphone and that sound to come out of the speakers in real-time.
Recording sound to a file for later playback was a piece of cake, but no matter what I try I can't get it to play back immediately. This is really easy on non-store apps using NAudio, but unfortunately there is no support for that yet.

I'm using a mediacapture object to record to a stream, and then using that stream as the source of a mediaelement object, but this doesn't work.

MediaCapture input = new MediaCapture()
MediaCaptureInitializationSettings inputSettings = new MediaCaptureInitializationSettings();
MediaEncodingProfile encodingProfile = new MediaEncoding Profile();
InMemoryRandomAccessStream recStream = new InMemoryRandomAccessStream();
MediaElement playback = new MediaElement();
;

inputSettings.AudioDeviceId = "";
inputSettings.StreamingCaptureMode = StreamingCaptureMode.Audio;
await input.InitializeAsync(inputSettings);
encodingProfile = MediaEncodingProfile.CreateWma(AudioEncodingQuality.Auto);

LayoutRoot.Children.Add(playback);
playback.RealTimePlayback = true;
playback.AudioCategory = AudioCategory.Communications;

await input.StartRecordToStreamAsync(encodingProfile, recStream);
playback.SetSource(recStream, "audio/x-ms-wma");
playback.Play();

This code works if i change it to record to a storage file, so I know the device is set up ok.

Has anyone done anything like this on Windows 8 before? Any help would be greatly appreciated.