C# XAudio2 Sound Playback for Windows Phone

     Let's begin with a small introduction to XAudio2:
     XAudio2 is a low-level audio API. It provides a signal processing and mixing foundation for games that is similar to its predecessors, DirectSound and XAudio. XAudio2 is the replacement for both DirectSound and XAudio.
     XAudio2 abstracts audio generation by separating sound data from "voice", allowing each voice to be filtered by programmable digital signal processing and effects processing functions. Voices can be "submixed" together into a single stream. There is always only one Mastering Voice that outputs the result using WASAPI.

     XAudio2 is primarily intended for developing high performance audio engines for games. For game developers who want to add sound effects and background music to their modern games, XAudio2 offers an audio graph and mixing engine with low-latency and support for dynamic buffers, synchronous sample-accurate playback, and implicit source rate conversion. Compared to WASAPI, XAudio2 requires only a minimum amount of code even for complex audio solutions. Compared to the Media Foundation engine, XAudio2 is a low-level, low-latency C++ API that is designed for use in games.

     XAudio2 cannot be used for background music - for this task you will have to use the IMFMediaEngine. XAudio2 cannot be used for capturing audio - for this task you will have to use WASAPI. Do not use XAudio2 for media playback. For that task you can use MediaElement

    XAudio2 is part of the DirectX api that is included in the new Windows Phone 8 SDK. The Api is shared between Windows 8 and Windows Phone 8 which means that you will be able to fully reuse your source code on both platforms. 

If you want to use XAudio2 for your C#/VB/HTML code you have two options:

1. Use SharpDX . SharpDX is a wrapper of the DirectX Api under .Net platform. Theoretically you can use it to call XAudio2 api directly from your managed code. Practically what happens is that the .Net CLR/GC on ARM seem to block native threads so your audio will shutter/glitch in certain conditions. I had the same problem when I was developing our Windows 8 game Kids' Orchestra and the audio had glitches even on a core i7 processor.

2. The other option, which from my experience works better, is to develop an Windows Phone Runtime Component that will manage the XAudio2 part and expose the needed methods/events to the managed code.

      To better understand how it is done I took the Windows 8 sample XAudio2 audio file playback sample C++ from MSDN and ported to Windows Phone 8 by splitting it in two projects: The C#/Xaml part for the UI and the "audio" project which is a Windows Phone Runtime component developed in C++.

     The porting was pretty easy. I only had to re-code the player class to make it "visible" to the managed code project and added an event that will tell you when a certain Source Voice has finished playing its buffer/sound (we have 7 sounds and each sound has a Source Voice associated to it). If you need further details on how to write a Windows Phone Runtime component in C++ have a look at this  MSDN Post

    This sample only plays Wav files that are resources in the C++ project. You could also dynamically generate sounds in managed code and pass the Wave/buffer data as a byte[] to the runtime component. Inside the native code you will then generate an XAUDIO2_BUFFER and submit it to a Source Voice for playing.

     I have attached the SOURCE CODE for the Windows Phone project. If you have problems with it don't hesitate to contact me.

NAMASTE!

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Farseer Physics for Windows Store Apps using Monogame

  Last week I did a session on porting XNA Windows Phone 7.x games to Windows Store apps using MonoGame. I have to thank Dean Ellis from the MonoGame project team for all the help. 

 While XNA is not a framework directly supported by Microsoft for Windows Store apps the current version of MonoGame is compatible with Windows 8 and, the most important thing, the applications pass the WACK. There are already several games available in the Windows Store developed using MonoGame (Armed, Skiddy, Rune Legend and I guess there are more). 

   For the session I ended up using the Simple Animation sample but seeing how easy is to share the code between the platforms (Windows, Windows Phone,PC, MAC, iOS, Android, Playstation, Linux) I started looking for a physics engine. The most used Open Source physics engine seems to be Farseer Physics but it was too late to do the porting for my session. On Sunday I tried the porting and everything went pretty smooth. The only thing I've changed was the serialization/de-serialization of the "World" state. I compiled the engine and also the sample. For the Sample project the Content Project was compiled using Visual Studio 2010 (for the moment Visual Studio 2012 doesn't recognize this type of project) and added the xnb's to a Content folder inside the Visual Studio 2012 solution. 

 You can see the result in this YouTube video:

I've used SnagIt to capture the movie and it influenced the frame rate (when running without capturing the framerate is always at 60 fps). The test device was the Samsung Slate which has a powerful cpu. I would love to know if a WinRT device will be able to run at the . If any of my readers has access to a WinRT device please deploy the sample to the device and let me know if the framerate is as expected. For the sample you will have to use an external keyboard and mouse as the touch screen is not working in this version. I will try to fix it for the next release (the problem seems to be inside the MonoGame framework as I only receive the move event and not the pressed and released from the touch screen).

   

Use this link to download the full project (engine and sample): 

SOURCE CODE

NAMASTE

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