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How to: Integrate X3DAudio with XAudio2

This topic shows how to integrate X3DAudio with XAudio2. You can use X3DAudio to provide the volume and pitch values for XAudio2 voices and the parameters for the XAudio2 built in reverb effect. This topic assumes that you have created an audio graph as described in How to: Build a Basic Audio Processing Graph. If you have not already created an audio graph, X3DAudioInitialize will fail.

Ee415798.wedge(en-us,VS.85).gifTo initialize X3DAudio

  1. Initialize X3DAudio by calling X3DAudioInitialize.

    The X3DAudioInitialize function takes flags indicating the speaker setup, the speed of sound in user-defined world units per second, and a handle to return an instance of the X3DAudio engine. Call IXAudio2MasteringVoice::GetChannelMask to get the output format's channel mask.

    DWORD dwChannelMask;       
    pMasteringVoice->GetChannelMask( &dwChannelMask );       
    X3DAUDIO_HANDLE X3DInstance;
    X3DAudioInitialize( dwChannelMask, X3DAUDIO_SPEED_OF_SOUND, X3DInstance );
  2. Create instances of the X3DAUDIO_LISTENER and X3DAUDIO_EMITTER structures.

    The X3DAUDIO_LISTENER structure represents the position of whatever is hearing the sound. Generally, this is the position of the camera or a position close to it. The X3DAUDIO_EMITTER structure represents the position of the thing making the sound. There will be one X3DAUDIO_EMITTER structure for each sound that is being tracked.

    Members of the structures that will not be updated in a game loop should be initialized here. Most members of the structures can simply be initialized to zero. However, some members of X3DAUDIO_EMITTER need to be set to be initialized to non-zero values. The ChannelCount member of the X3DAUDIO_EMITTER needs to be initialized to the number of channels in the voice the emitter represents. Also, the CurveDistanceScaler member of X3DAUDIO_EMITTER must be in the range FLT_MIN to FLT_MAX.

    X3DAUDIO_LISTENER Listener = {0};
    X3DAUDIO_EMITTER Emitter = {0};
    Emitter.ChannelCount = 1;
    Emitter.CurveDistanceScaler = FLT_MIN;
  3. Create an instance of the X3DAUDIO_DSP_SETTINGS structure.

    The X3DAUDIO_DSP_SETTINGS structure is used to return results calculated by X3DAudioCalculate. The X3DAudioCalculate function does not allocate memory for any of its parameters. This means that you need to allocate arrays for the X3DAUDIO_DSP_SETTINGS structure's pMatrixCoefficients and pDelayTimes members if you intend to use them. In addition, you need to set the SrcChannelCount and DstChannelCount members to the number of channels in the emitter's source and destination voices.

    X3DAUDIO_DSP_SETTINGS DSPSettings = {0};
    FLOAT32 * matrix = new FLOAT32[deviceDetails.OutputFormat.Format.nChannels];
    DSPSettings.SrcChannelCount = 1;
    DSPSettings.DstChannelCount = deviceDetails.OutputFormat.Format.nChannels;
    DSPSettings.pMatrixCoefficients = matrix;
    Note  Use IXAudio2Voice::GetVoiceDetails on the mastering voice to obtain the number of InputChannels for nChannels. For DirectX SDK versions of XAUDIO2 prior to Windows 8, use IXAudio2::GetDeviceDetails.

Perform these steps once every two to three frames to calculate new settings and apply them. In this example, a source voice is sending directly to the mastering voice and to a submix voice with a reverb effect applied to it.

Ee415798.wedge(en-us,VS.85).gifTo use X3DAudio to calculate and apply new 3D audio settings

  1. Update the X3DAUDIO_LISTENER and X3DAUDIO_EMITTER structures with their current position, velocity, and orientation.

    Emitter.OrientFront = EmitterOrientFront;
    Emitter.OrientTop = EmitterOrientTop;
    Emitter.Position = EmitterPosition;
    Emitter.Velocity = EmitterVelocity;
    Listener.OrientFront = ListenerOrientFront;
    Listener.OrientTop = ListenerOrientTop;
    Listener.Position = ListenerPosition;
    Listener.Velocity = ListenerVelocity;
  2. Call X3DAudioCalculate to calculate new settings for the voices.

    The parameters for X3DAudioCalculate will be the updated X3DAUDIO_LISTENER and X3DAUDIO_EMITTER structures. The flags will indicate what values X3DAudioCalculate should calculate, and which X3DAUDIO_DSP_SETTINGS structure will hold the results of the calculations performed.

    X3DAudioCalculate(X3DInstance, &Listener, &Emitter,
        &DSPSettings );
  3. Use IXAudio2Voice::SetOutputMatrix and IXAudio2SourceVoice::SetFrequencyRatio to apply the volume and pitch values to the source voice.

    pSFXSourceVoice->SetOutputMatrix( pMasterVoice, 1, deviceDetails.OutputFormat.Format.nChannels, DSPSettings.pMatrixCoefficients ) ;
  4. Use IXAudio2Voice::SetOutputMatrix to apply the calculated reverb level to the submix voice.

    pSFXSourceVoice->SetOutputMatrix(pSubmixVoice, 1, 1, &DSPSettings.ReverbLevel);
  5. Use IXAudio2Voice::SetFilterParameters to apply the calculated low pass filter direct coefficient to the source voice.

    XAUDIO2_FILTER_PARAMETERS FilterParameters = { LowPassFilter, 2.0f * sinf(X3DAUDIO_PI/6.0f * DSPSettings.LPFDirectCoefficient), 1.0f };

Related topics

X3DAudio Overview
XAudio2 Programming Guide
XAudio2 Volume and Pitch Control



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