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[This article is for Windows 8.x and Windows Phone 8.x developers writing Windows Runtime apps. If you’re developing for Windows 10, see the latest documentation]

In this step, we examine how the shooting game sample creates an object for sound playback using the XAudio2 APIs.

Objective

  • To add sound output using XAudio2.

Note  Complete sample code that corresponds to this tutorial is found in the Windows Store Direct3D shooting game sample.

 

In the game sample, the audio objects and behaviors are defined in three files:

  • Audio.h/.cpp. This code file defines the Audio object, which contains the XAudio2 resources for sound playback. It also defines method for suspending and resuming audio playback if the game is paused or deactivated.
  • MediaReader.h/.cpp. This code defines methods for reading audio .wav files from local storage.
  • SoundEffect.h/.cpp. This code defines an object for in-game sound playback.

Defining the audio engine

When the game sample starts, it creates an Audio object that allocates the audio resources for the game. The code that declares this object looks like this:

public:
    Audio();

    void Initialize();
    void CreateDeviceIndependentResources();
    IXAudio2* MusicEngine();
    IXAudio2* SoundEffectEngine();
    void SuspendAudio();
    void ResumeAudio();

protected:
    bool                                m_audioAvailable;
    Microsoft::WRL::ComPtr<IXAudio2>    m_musicEngine;
    Microsoft::WRL::ComPtr<IXAudio2>    m_soundEffectEngine;
    IXAudio2MasteringVoice*             m_musicMasteringVoice;
    IXAudio2MasteringVoice*             m_soundEffectMasteringVoice;
};

The Audio::MusicEngine and Audio::SoundEffectEngine methods return references to IXAudio2 objects that define the mastering voice for each audio type. A mastering voice is the audio device used for playback. Sound data buffers cannot be submitted directly to mastering voices, but data submitted to other types of voices must be directed to a mastering voice to be heard.

Initializing the audio resources

The sample initializes the IXAudio2 objects for the music and sound effect engines with calls to XAudio2Create. After the engines have been instantiated, it creates a mastering voice for each with calls to IXAudio2::CreateMasteringVoice, as here:


void Audio::CreateDeviceIndependentResources()
{
    UINT32 flags = 0;

    DX::ThrowIfFailed(
        XAudio2Create(&m_musicEngine, flags)
        );

    HRESULT hr = m_musicEngine->CreateMasteringVoice(&m_musicMasteringVoice);
    if (FAILED(hr))
    {
        // Unable to create an audio device
        m_audioAvailable = false;
        return;
    }

    DX::ThrowIfFailed(
        XAudio2Create(&m_soundEffectEngine, flags)
        );

    DX::ThrowIfFailed(
        m_soundEffectEngine->CreateMasteringVoice(&m_soundEffectMasteringVoice)
        );

    m_audioAvailable = true;
}

As a music or sound effect audio file is loaded, this method calls IXAudio2::CreateSourceVoice on the mastering voice, which creates an instance of a source voice for playback. We look at the code for this as soon as we finish reviewing how the game sample loads audio files.

Reading an audio file

In the game sample, the code for reading audio format files is defined in MediaReader.cpp. The specific method that reads in an encoded .wav audio file, MediaReader::LoadMedia, looks like this:

Platform::Array<byte>^  MediaReader::LoadMedia(_In_ Platform::String^ filename)
{
    DX::ThrowIfFailed(
        MFStartup(MF_VERSION)
        );

    ComPtr<IMFSourceReader> reader;
    DX::ThrowIfFailed(
        MFCreateSourceReaderFromURL(
            Platform::String::Concat(m_installedLocationPath, filename)->Data(),
            nullptr,
            &reader
            )
        );

    // Set the decoded output format as PCM
    // XAudio2 on Windows can process PCM and ADPCM-encoded buffers.
    // When using MediaFoundation, this sample always decodes into PCM.
    Microsoft::WRL::ComPtr<IMFMediaType> mediaType;
    DX::ThrowIfFailed(
        MFCreateMediaType(&mediaType)
        );

    DX::ThrowIfFailed(
        mediaType->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Audio)
        );

    DX::ThrowIfFailed(
        mediaType->SetGUID(MF_MT_SUBTYPE, MFAudioFormat_PCM)
        );

    DX::ThrowIfFailed(
        reader->SetCurrentMediaType(MF_SOURCE_READER_FIRST_AUDIO_STREAM, 0, mediaType.Get())
        );

    // Get the complete WAVEFORMAT from the Media Type
    Microsoft::WRL::ComPtr<IMFMediaType> outputMediaType;
    DX::ThrowIfFailed(
        reader->GetCurrentMediaType(MF_SOURCE_READER_FIRST_AUDIO_STREAM, &outputMediaType)
        );

    UINT32 size = 0;
    WAVEFORMATEX* waveFormat;
    DX::ThrowIfFailed(
        MFCreateWaveFormatExFromMFMediaType(outputMediaType.Get(), &waveFormat, &size)
        );

    CopyMemory(&m_waveFormat, waveFormat, sizeof(m_waveFormat));
    CoTaskMemFree(waveFormat);

    // Get the total length of the stream in bytes
    PROPVARIANT propVariant;
    DX::ThrowIfFailed(
        reader->GetPresentationAttribute(MF_SOURCE_READER_MEDIASOURCE, MF_PD_DURATION, &propVariant)
        );
    LONGLONG duration = propVariant.uhVal.QuadPart;
    unsigned int maxStreamLengthInBytes;

    double durationInSeconds = (duration / static_cast<double>(10000 * 1000));
    maxStreamLengthInBytes = static_cast<unsigned int>(durationInSeconds * m_waveFormat.nAvgBytesPerSec);

    // Make length a multiple of 4 bytes
    maxStreamLengthInBytes = (maxStreamLengthInBytes + 3) / 4 * 4;

    Platform::Array<byte>^ fileData = ref new Platform::Array<byte>(maxStreamLengthInBytes);

    ComPtr<IMFSample> sample;
    ComPtr<IMFMediaBuffer> mediaBuffer;
    DWORD flags = 0;

    int positionInData = 0;
    bool done = false;
    while (!done)
    {
        DX::ThrowIfFailed(
            reader->ReadSample(MF_SOURCE_READER_FIRST_AUDIO_STREAM, 0, nullptr, &flags, nullptr, &sample)
            );

        if (sample != nullptr)
        {
            DX::ThrowIfFailed(
                sample->ConvertToContiguousBuffer(&mediaBuffer)
                );

            BYTE *audioData = nullptr;
            DWORD sampleBufferLength = 0;
            DX::ThrowIfFailed(
                mediaBuffer->Lock(&audioData, nullptr, &sampleBufferLength)
                );

            for (DWORD i = 0; i < sampleBufferLength; i++)
            {
                fileData[positionInData++] = audioData[i];
            }
        }
        if (flags & MF_SOURCE_READERF_ENDOFSTREAM)
        {
            done = true;
        }
    }

    // Fix up the array size on match the actual length.
    Platform::Array<byte>^ realfileData = ref new Platform::Array<byte>((positionInData + 3) / 4 * 4);
    memcpy(realfileData->Data, fileData->Data, positionInData);
    return realfileData;
}

This method uses the Media Foundation APIs to read in the .wav audio file as a Pulse Code Modulation (PCM) buffer.

  1. Creates a media source reader (IMFSourceReader) object by calling MFCreateSourceReaderFromURL.
  2. Creates a media type (IMFMediaType) for the decoding of the audio file by calling MFCreateMediaType. This method specifies that the decoded output is PCM audio, which is an audio type that XAudio2 can use.
  3. Sets the decoded output media type for the reader by calling IMFSourceReader::SetCurrentMediaType.
  4. Creates a WAVEFORMATEX buffer and copies the results of a call to IMFMediaType::MFCreateWaveFormatExFromMFMediaType on the IMFMediaType object. This formats the buffer that holds the audio file after it is loaded.
  5. Gets the duration, in seconds, of the audio stream by calling IMFSourceReader::GetPresentationAttribute and then converts the duration to bytes.
  6. Reads the audio file in as a stream by calling IMFSourceReader::ReadSample.
  7. Copies the contents of the audio sample buffer into an array returned by the method.

The most important thing in SoundEffect::Initialize is the creation of the source voice object, m_sourceVoice, from the mastering voice. We use the source voice for the actual play back of the sound data buffer obtained from MediaReader::LoadMedia.

The sample game calls this method when it initializes the SoundEffect object, like this:

void SoundEffect::Initialize(
    _In_ IXAudio2 *masteringEngine,
    _In_ WAVEFORMATEX *sourceFormat,
    _In_ Platform::Array<byte>^ soundData)
{
    m_soundData = soundData;

    if (masteringEngine == nullptr)
    {
        // audio is not available so return
        m_audioAvailable = false;
        return;
    }

    // Create and reuse a single source voice for the single sound effect in this sample
    DX::ThrowIfFailed(
        masteringEngine->CreateSourceVoice(
            &m_sourceVoice,
            sourceFormat
            )
        );
    m_audioAvailable = true;
}

This method is passed the results of calls to Audio::SoundEffectEngine (or Audio::MusicEngine), MediaReader::GetOutputWaveFormatEx, and the buffer returned by a call to MediaReader::LoadMedia, as seen here.

MediaReader^ mediaReader = ref new MediaReader;
auto targetHitSound = mediaReader->LoadMedia("hit.wav");

myTarget->HitSound(ref new SoundEffect());
myTarget->HitSound()->Initialize(
                m_audioController->SoundEffectEngine(),
                mediaReader->GetOutputWaveFormatEx(),
                targetHitSound);

SoundEffect::Initialize is called from the Simple3DGame:Initialize method that initializes the main game object.

Now that the sample game has an audio file in memory, let's see how it plays it back during game play!

Playing back an audio file

void SoundEffect::PlaySound(_In_ float volume)
{
    XAUDIO2_BUFFER buffer = {0};
    XAUDIO2_VOICE_STATE state = {0};

    if (!m_audioAvailable)
    {
        // Audio is not available so just return
        return;
    }

    // Interrupt sound effect if currently playing
    DX::ThrowIfFailed(
        m_sourceVoice->Stop()
        );
    DX::ThrowIfFailed(
        m_sourceVoice->FlushSourceBuffers()
        );

    // Queue in-memory buffer for playback and start the voice
    buffer.AudioBytes = m_soundData->Length;
    buffer.pAudioData = m_soundData->Data;
    buffer.Flags = XAUDIO2_END_OF_STREAM;

    m_sourceVoice->SetVolume(volume);
    DX::ThrowIfFailed(
        m_sourceVoice->SubmitSourceBuffer(&buffer)
        );
    DX::ThrowIfFailed(
        m_sourceVoice->Start()
        );
}

To play the sound, this method uses the source voice object m_sourceVoice to start the playback of the sound data buffer m_soundData. It creates an XAUDIO2_BUFFER, to which it provides a reference to the sound data buffer, and then submits it with a call to IXAudio2SourceVoice::SubmitSourceBuffer. With the sound data queued up, SoundEffect::PlaySound starts play back by calling IXAudio2SourceVoice::Start.

Now, whenever a collision between the ammo and a target occurs, a call to SoundEffect::PlaySound causes a noise to play.

Next steps

That was a whirlwind tour of Windows Store DirectX game development! At this point, you have an idea of what you need to do to make your own game for Windows 8 a great experience. Remember, your game can be played on a wide variety of Windows 8 devices and platforms, so design your components: your graphics, your controls, your user interface, and your audio for as wide a set of configurations as you can!

For more info on ways to modify the game sample provided in these documents, see Extending the game sample.

Complete sample code for this section

Audio.h

//// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
//// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
//// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
//// PARTICULAR PURPOSE.
////
//// Copyright (c) Microsoft Corporation. All rights reserved

#pragma once

ref class Audio
{
public:
    Audio();

    void Initialize();
    void CreateDeviceIndependentResources();
    IXAudio2* MusicEngine();
    IXAudio2* SoundEffectEngine();
    void SuspendAudio();
    void ResumeAudio();

protected:
    bool                                m_audioAvailable;
    Microsoft::WRL::ComPtr<IXAudio2>    m_musicEngine;
    Microsoft::WRL::ComPtr<IXAudio2>    m_soundEffectEngine;
    IXAudio2MasteringVoice*             m_musicMasteringVoice;
    IXAudio2MasteringVoice*             m_soundEffectMasteringVoice;
};

Audio.cpp

//// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
//// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
//// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
//// PARTICULAR PURPOSE.
////
//// Copyright (c) Microsoft Corporation. All rights reserved

#include "pch.h"
#include "Audio.h"
#include "DirectXSample.h"

using namespace Microsoft::WRL;
using namespace Windows::Foundation;
using namespace Windows::UI::Core;
using namespace Windows::Graphics::Display;

Audio::Audio():
    m_audioAvailable(false)
{
}

void Audio::Initialize()
{
}

void Audio::CreateDeviceIndependentResources()
{
    UINT32 flags = 0;

    DX::ThrowIfFailed(
        XAudio2Create(&m_musicEngine, flags)
        );

#if defined(_DEBUG)
    XAUDIO2_DEBUG_CONFIGURATION debugConfiguration = {0};
    debugConfiguration.BreakMask = XAUDIO2_LOG_ERRORS;
    debugConfiguration.TraceMask = XAUDIO2_LOG_ERRORS;
    m_musicEngine->SetDebugConfiguration(&debugConfiguration);
#endif


    HRESULT hr = m_musicEngine->CreateMasteringVoice(&m_musicMasteringVoice);
    if (FAILED(hr))
    {
        // Unable to create an audio device
        m_audioAvailable = false;
        return;
    }

    DX::ThrowIfFailed(
        XAudio2Create(&m_soundEffectEngine, flags)
        );

#if defined(_DEBUG)
    m_soundEffectEngine->SetDebugConfiguration(&debugConfiguration);
#endif

    DX::ThrowIfFailed(
        m_soundEffectEngine->CreateMasteringVoice(&m_soundEffectMasteringVoice)
        );

    m_audioAvailable = true;
}

IXAudio2* Audio::MusicEngine()
{
    return m_musicEngine.Get();
}

IXAudio2* Audio::SoundEffectEngine()
{
    return m_soundEffectEngine.Get();
}

void Audio::SuspendAudio()
{
    if (m_audioAvailable)
    {
        m_musicEngine->StopEngine();
        m_soundEffectEngine->StopEngine();
    }
}

void Audio::ResumeAudio()
{
    if (m_audioAvailable)
    {
        DX::ThrowIfFailed(m_musicEngine->StartEngine());
        DX::ThrowIfFailed(m_soundEffectEngine->StartEngine());
    }
}

SoundEffect.h

//// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
//// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
//// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
//// PARTICULAR PURPOSE.
////
//// Copyright (c) Microsoft Corporation. All rights reserved

#pragma once

ref class SoundEffect
{
public:
    SoundEffect();

    void Initialize(
        _In_ IXAudio2*              masteringEngine,
        _In_ WAVEFORMATEX*          sourceFormat,
        _In_ Platform::Array<byte>^ soundData
        );

    void PlaySound(_In_ float volume);

protected:
    bool                    m_audioAvailable;
    IXAudio2SourceVoice*    m_sourceVoice;
    Platform::Array<byte>^  m_soundData;
};

SoundEffect.cpp

//// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
//// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
//// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
//// PARTICULAR PURPOSE.
////
//// Copyright (c) Microsoft Corporation. All rights reserved

#include "pch.h"
#include "SoundEffect.h"
#include "DirectXSample.h"

SoundEffect::SoundEffect():
    m_audioAvailable(false)
{
}
//----------------------------------------------------------------------
void SoundEffect::Initialize(
    _In_ IXAudio2 *masteringEngine,
    _In_ WAVEFORMATEX *sourceFormat,
    _In_ Platform::Array<byte>^ soundData)
{
    m_soundData = soundData;

    if (masteringEngine == nullptr)
    {
        // audio is not available so return
        m_audioAvailable = false;
        return;
    }

    // Create and reuse a single source voice for the single sound effect in this sample
    DX::ThrowIfFailed(
        masteringEngine->CreateSourceVoice(
            &m_sourceVoice,
            sourceFormat
            )
        );
    m_audioAvailable = true;
}
//----------------------------------------------------------------------
void SoundEffect::PlaySound(_In_ float volume)
{
    XAUDIO2_BUFFER buffer = {0};
    XAUDIO2_VOICE_STATE state = {0};

    if (!m_audioAvailable)
    {
        // Audio is not available so just return
        return;
    }

    // Interrupt sound effect if currently playing
    DX::ThrowIfFailed(
        m_sourceVoice->Stop()
        );
    DX::ThrowIfFailed(
        m_sourceVoice->FlushSourceBuffers()
        );

    // Queue in-memory buffer for playback and start the voice
    buffer.AudioBytes = m_soundData->Length;
    buffer.pAudioData = m_soundData->Data;
    buffer.Flags = XAUDIO2_END_OF_STREAM;

    m_sourceVoice->SetVolume(volume);
    DX::ThrowIfFailed(
        m_sourceVoice->SubmitSourceBuffer(&buffer)
        );
    DX::ThrowIfFailed(
        m_sourceVoice->Start()
        );
}