AK::SoundEngine::PostEvent( AK::EVENTS::PLAY_HELLO, GAME_OBJECT_HUMAN, AK_SpeakerVolumeMatrix, VoiceCallback );

static void VoiceCallback( 
    AkCallbackType in_eType,                            // Callback type.
    AkCallbackInfo* in_pCallbackInfo                    // Structure containing desired information. You can cast it to the proper sub-type, depending on the callback type.
    )
{
    // We know this is a speaker volume matrix callback. Cast to proper subtype.
    AKASSERT( in_eType == AK_SpeakerVolumeMatrix );
    AkSpeakerVolumeMatrixCallbackInfo* pVolumeCallbackInfo = (AkSpeakerVolumeMatrixCallbackInfo*)in_pCallbackInfo;

    // Event, game object and playing ID correspond to the IDs passed to / returned from PostEvent().
    AkUniqueID eventID = pVolumeCallbackInfo->eventID;
    AkGameObjectID objID = pVolumeCallbackInfo->gameObjID;
    AkPlayingID playingID = pVolumeCallbackInfo->playingID;
    
    AKASSERT( eventID == AK::EVENTS::PLAY_HELLO );
    
    // This callback gets called for each bus into which the voice is routed. In this example, we want to customize mix into the "My_Dry_Bus" bus only.
    if ( pVolumeCallbackInfo->pMixerContext->GetBusID() != AK::SoundEngine::GetIDFromString( "My_Dry_Bus" ) )
        return;

        
    // Apply arbitrary changes to "base" volumes (i.e. common to all channels).
    // ---------------------------------------------------------------------------------
    
    // Double the volume (+6dB) of the voice into "My_Dry_Bus".
    *pVolumeCallbackInfo->pfBaseVolume *= 2.f;
    
    // Undo distance attenuation of the voice into "My_Dry_Bus" (in the single position case).
    *pVolumeCallbackInfo->pfEmitterListenerVolume = 1.f;
    
    
    // Change panning of the voice into "My_Dry_Bus". Say the sound uses 3D positioning.
    // ---------------------------------------------------------------------------------
    AkUInt32 uNumPosition = pVolumeCallbackInfo->pContext->GetNum3DPositions();

    // A 3D sound may have multiple positions (see AK::SoundEngine::SetMultiplePositions()). この例では、最初のみを考慮します。
    if ( uNumPosition > 0 )
    {
        // Get angle of incidence using the input (voice) context.
        AkEmitterListenerPair ray;
        pVolumeCallbackInfo->pContext->Get3DPosition( 0, ray );

        // Use mixing services of the bus/mixer to compute new panning volumes, by shifting the azimuth by 90 degrees (PI/2) to the right (positive angle).
        pVolumeCallbackInfo->pMixerContext->Compute3DPositioning( 
            ray.Azimuth() + 1.57079f,                       // Azimuth: Shift azimuth angle.
            pVolumeCallbackInfo->pContext->GetSpread( 0 ),  // Spread: Use spread value computed by Wwise.
            pVolumeCallbackInfo->pContext->GetFocus( 0 ),   // Focus: Use focus value computed by Wwise.
            pVolumeCallbackInfo->inputConfig,               // Input (voice) channel config.
            pVolumeCallbackInfo->outputConfig,              // Output (bus) channel config.
            pVolumeCallbackInfo->pContext->GetCenterPerc(), // Center%: Use center% value computed by Wwise.
            pVolumeCallbackInfo->pVolumes );                // Pass in the mixing matrix; its values will be overriden by Compute3DPositioning(), thus changing the resulting panning.
    }
}

AK::SoundEngine::RegisterBusVolumeCallback( AK::SoundEngine::GetIDFromString( "My_Bus" ), BusCallback );

static void BusCallback( 
    AkSpeakerVolumeMatrixCallbackInfo* in_pCallbackInfo // Structure containing desired bus information.
    )
{
    // Called from a bus: cannot be associated to a playing ID.
    AKASSERT( in_pCallbackInfo->playingID == AK_INVALID_PLAYING_ID );
    
    // Change panning volumes of the mixdown signal at the output of this bus before it gets mixed into its parent;
    // Using mixing services, transmix input into a 3-stereo configuration, and silence out contribution to all other channels of the parent bus.

    // Allocate a volume matrix to obtain transmix gains (input_config -> 3-stereo).
    AkChannelConfig cfgThreeStereo;
    cfgThreeStereo.SetStandard( AK_SPEAKER_SETUP_3STEREO );
    AkUInt32 uSize = AK::SpeakerVolumes::Matrix::GetRequiredSize( in_pCallbackInfo->inputConfig.uNumChannels, cfgThreeStereo.uNumChannels );
    AK::SpeakerVolumes::MatrixPtr mxTransmix = (AK::SpeakerVolumes::MatrixPtr)AkAlloca( uSize );

    in_pCallbackInfo->pMixerContext->ComputeSpeakerVolumesDirect(
        in_pCallbackInfo->inputConfig,  // Channel configuration of the input.
        cfgThreeStereo,                 // Channel configuration of the mixer output.
        in_pCallbackInfo->pContext->GetCenterPerc(),// Center%: Use center% value computed by Wwise.
        mxTransmix );

    // Copy result into real mixing matrix and clear out the back channels and LFE (if applicable).
    // Warning: we cannot assume that the mixing bus has a center channel, so we need to verify it.
    AkChannelConfig cfgThreeStereoANDBus;
    cfgThreeStereoANDBus.SetStandard( AK_SPEAKER_SETUP_3STEREO & in_pCallbackInfo->outputConfig.uChannelMask );
    AkUInt32 uNumOutputChannelsToCopy = cfgThreeStereoANDBus.uNumChannels;

    for ( AkUInt32 uChanIn = 0; uChanIn < in_pCallbackInfo->inputConfig.uNumChannels; uChanIn++ )
    {
        // Get output volume vector for each input channel.
        AK::SpeakerVolumes::VectorPtr vTransmixOut = AK::SpeakerVolumes::Matrix::GetChannel( mxTransmix, uChanIn, cfgThreeStereo.uNumChannels );
        AK::SpeakerVolumes::VectorPtr vMixOut = AK::SpeakerVolumes::Matrix::GetChannel( in_pCallbackInfo->pVolumes, uChanIn, in_pCallbackInfo->outputConfig.uNumChannels );

        // Copy panning to front channels.
        AkUInt32 uChanOut = 0;
        while ( uChanOut < uNumOutputChannelsToCopy )
        {
            vMixOut[uChanOut] = vTransmixOut[uChanOut];
            ++uChanOut;
        }

        // Clear out other channels.
        while ( uChanOut < in_pCallbackInfo->outputConfig.uNumChannels )
        {
            vMixOut[uChanOut] = 0;
            ++uChanOut;
        }
    }
}

// Register to bus metering. Note: there is a significant cost to registering to metering, especially True Peak and K-Weighted Power.
AK::SoundEngine::RegisterBusMeteringCallback( AK::SoundEngine::GetIDFromString( "My_Bus" ), MeterCallback, (AkMeteringFlags)( AK_EnableBusMeter_TruePeak | AK_EnableBusMeter_KPower ) );

static void MeterCallback(
    AK::IAkMetering * in_pMetering,                     // AK::IAkMetering interface for retrieving metering information.
    AkChannelConfig in_channelConfig,                   // Channel configuration of the bus.
    AkMeteringFlags in_eMeteringFlags                   // Metering flags that were asked for in RegisterBusMeteringCallback(). You may only access corresponding meter values from in_pMeteringInfo. Others will fail.
    )
{
    // At least true peak and K-weighted power metering must be enabled since we registered for this callback.
    AKASSERT( ( in_eMeteringFlags & AK_EnableBusMeter_TruePeak ) && ( in_eMeteringFlags & AK_EnableBusMeter_KPower ) );
    
    // Get K-weighted power and do something with it.
    AkReal32 fPower = in_pMetering->GetKWeightedPower();

    // Get true peak and do something with it.
    // There is one value per channel.
    AK::SpeakerVolumes::ConstVectorPtr vTruePeak = in_pMetering->GetTruePeak();
    for ( AkUInt32 uChannel = 0; uChannel < in_channelConfig.uNumChannels; uChannel++ )
    {
        AkReal32 fChannelPeak = vTruePeak[uChannel];

        ...
    }

    ...
}