XAudio2学习之IXAudio2VoiceCallback回调

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使用IXAudio2VoiceCallback回调的好处是，在音频数据播放完的时候，可以通知外部程序进行其他操作。

使用IXAudio2VoiceCallback需要继承此接口，然后重新实现，因为内部所有函数都是纯虚函数。所有函数中使用比较多的是OnStreamEnd函数，当音频数据播放完成的时候，OnStreamEnd会触发一个事件。

继承实现IXAudio2VoiceCallback接口：

class VoiceCallback : public IXAudio2VoiceCallback
{
public:
    HANDLE hBufferEndEvent;
    VoiceCallback(): hBufferEndEvent( CreateEvent( NULL, FALSE, FALSE, NULL ) ){}
    ~VoiceCallback(){ CloseHandle( hBufferEndEvent ); }

    //Called when the voice has just finished playing a contiguous audio stream.
    void OnStreamEnd() { SetEvent( hBufferEndEvent ); }

    //Unused methods are stubs
    void OnVoiceProcessingPassEnd() { }
    void OnVoiceProcessingPassStart(UINT32 SamplesRequired) {    }
    void OnBufferEnd(void * pBufferContext)    { }
    void OnBufferStart(void * pBufferContext) {    }
    void OnLoopEnd(void * pBufferContext) {    }
    void OnVoiceError(void * pBufferContext, HRESULT Error) { }
};

怎么使用回调呢？

IXAudio2VoiceCallback是创建IXAudio2SourceVoice对象的时候给CreateSourceVoice使用的，第五个参数就是IXAudio2VoiceCallback对象的指针或者地址。

VoiceCallback pCallBack;
 	IXAudio2SourceVoice *pSourceVoice = NULL;
	hr = pEngine->CreateSourceVoice(&pSourceVoice, waveFormat, 0, 1.0f, &pCallBack);//创建源声音，用来提交数据
 	if (FAILED(hr))
 		return 0;

WaitForSingleObject(pCallBack.hBufferEndEvent, INFINITE);

XAUDIO2_VOICE_STATE state;
	pSourceVoice->GetState(&state);//获取状态
	while (state.BuffersQueued > XAUDIO2_MAX_QUEUED_BUFFERS - 1)
	{
		WaitForSingleObject(pCallBack.hBufferEndEvent, INFINITE);
		pSourceVoice->GetState(&state);
	}

注意：IXAudio2SourceVoice待播放队列中的数据要一直保持有效，直到播放完成，否则会崩溃。

测试代码（WaveFile.h/WaveFile.cpp见前面文章：XAudio2学习四之wave文件格式）：

#pragma once
#include "WaveFile.h"
#include "XAudio2.h"

class VoiceCallback : public IXAudio2VoiceCallback
{
public:
	HANDLE hBufferEndEvent;
	VoiceCallback() : hBufferEndEvent(CreateEvent(NULL, FALSE, FALSE, NULL)){}
	~VoiceCallback(){ CloseHandle(hBufferEndEvent); }

	//Called when the voice has just finished playing a contiguous audio stream.
	void OnStreamEnd() { SetEvent(hBufferEndEvent); }

	//Unused methods are stubs
	void OnVoiceProcessingPassEnd() { }
	void OnVoiceProcessingPassStart(UINT32 SamplesRequired) {    }
	void OnBufferEnd(void * pBufferContext)    { }
	void OnBufferStart(void * pBufferContext) {    }
	void OnLoopEnd(void * pBufferContext) {    }
	void OnVoiceError(void * pBufferContext, HRESULT Error) { }
};

 int main(int argc, char *argv[])
 {
	 HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);;//com初始化
 	if (FAILED(hr))
 		return 0;
 
 	IXAudio2 *pEngine = NULL;
 	hr = XAudio2Create(&pEngine);//创建引擎
 	if (FAILED(hr))
 		return 0;
 
 	IXAudio2MasteringVoice *pMasterVoice = NULL;
 	hr = pEngine->CreateMasteringVoice(&pMasterVoice);//创建主声音，默认是输出当前扬声器
 	if (FAILED(hr))
 		return 0;
 
 	CWaveFile waveFile;
 	hr = waveFile.Open(L"F:\\桌面\\24bit-48khz.wav", NULL, WAVEFILE_READ);//加载文件
 	if (FAILED(hr))
 		return 0;
 
 	WAVEFORMATEX *waveFormat = waveFile.GetFormat();//获取文件格式

	VoiceCallback pCallBack;
 	IXAudio2SourceVoice *pSourceVoice = NULL;
	hr = pEngine->CreateSourceVoice(&pSourceVoice, waveFormat, 0, 1.0f, &pCallBack);//创建源声音，用来提交数据
 	if (FAILED(hr))
 		return 0;
 
 	DWORD size = waveFile.GetSize();//获取文件的大小
 	BYTE *pData = new BYTE[size];//申请内存空间，用于保存数据
 	hr = waveFile.Read(pData, size, &size);//读取文件内容
 	if (FAILED(hr))
 		return 0;
 
	XAUDIO2_BUFFER buffer = {0};//将读取的文件数据，赋值XAUDIO2_BUFFER
 	buffer.AudioBytes = size;
 	buffer.pAudioData = pData;
	buffer.Flags = XAUDIO2_END_OF_STREAM;
 
 	hr = pSourceVoice->SubmitSourceBuffer(&buffer);//提交内存数据
 	if (FAILED(hr))
 		return 0;
 
 	hr = pSourceVoice->Start(0);//启动源声音
 	if (FAILED(hr))
 		return 0;
 
	XAUDIO2_VOICE_STATE state;
	pSourceVoice->GetState(&state);//获取状态
	while (state.BuffersQueued > XAUDIO2_MAX_QUEUED_BUFFERS - 1)
	{
		WaitForSingleObject(pCallBack.hBufferEndEvent, INFINITE);
		pSourceVoice->GetState(&state);
	}
 
 	pMasterVoice->DestroyVoice();//释放资源
 	pSourceVoice->DestroyVoice();//释放资源
 	pEngine->Release();//释放资源
 	CoUninitialize();//释放资源

	delete []pData;//释放资源
	pData = NULL;

 	return 0;
 }

源码下载：http://download.csdn.net/detail/u011417605/9471383

XAudio2学习之IXAudio2VoiceCallback回调

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原文地址：http://blog.csdn.net/u011417605/article/details/50970574