参考文档

COM Coding Practices
Audio File Format Specifications
Core Audio APIs
Loopback Recording

#include #include #include #include #include #include #include #include #include // 利用RAII手法,自动调用 CoUninitializeclass CoInitializeGuard {public:    CoInitializeGuard()    {        _hr = CoInitializeEx(nullptr, COINIT::COINIT_MULTITHREADED);    }    ~CoInitializeGuard()    {        if (_hr == S_OK || _hr == S_FALSE) {            CoUninitialize();        }    }    HRESULT result() const { return _hr; }private:    HRESULT _hr;};constexpr inline void exit_on_failed(HRESULT hr);void printEndpoints(CComPtr pColletion);std::string wchars_to_mbs(const wchar_t* s);int main(){    HRESULT hr{};    CoInitializeGuard coInitializeGuard;    exit_on_failed(coInitializeGuard.result());    // COM 对象都用 CComPtr 包装,会自动调用 Release    // COM 接口分配的堆变量用 CComHeapPtr 包装,会自动调用 CoTaskMemFree    CComPtr pEnumerator;    hr = pEnumerator.CoCreateInstance(__uuidof(MMDeviceEnumerator));    exit_on_failed(hr);    // 打印所有可用的音频设备    //CComPtr pColletion;    //hr = pEnumerator->EnumAudioEndpoints(eRender, DEVICE_STATE_ACTIVE, &pColletion);    //exit_on_failed(hr);    //printEndpoints(pColletion);    // 使用默认的 Audio Endpoint,eRender 表示音频播放设备,而不是录音设备    CComPtr pEndpoint;    hr = pEnumerator->GetDefaultAudioEndpoint(eRender, eConsole, &pEndpoint);    exit_on_failed(hr);    // 打印出播放设备的名字,可能包含中文    CComPtr pProps;    hr = pEndpoint->OpenPropertyStore(STGM_READ, &pProps);    exit_on_failed(hr);    PROPVARIANT varName;    PropVariantInit(&varName);    hr = pProps->GetValue(PKEY_Device_FriendlyName, &varName);    exit_on_failed(hr);    std::cout << "select audio endpoint: " << wchars_to_mbs(varName.pwszVal) << std::endl;    PropVariantClear(&varName);    // 由 IMMDevice 对象 得到 IAudioClient 对象     CComPtr pAudioClient;    hr = pEndpoint->Activate(__uuidof(IAudioClient), CLSCTX_ALL, nullptr, (void**)&pAudioClient);    exit_on_failed(hr);    // 获得音频播放设备格式信息    CComHeapPtr pDeviceFormat;    pAudioClient->GetMixFormat(&pDeviceFormat);    constexpr int REFTIMES_PER_SEC = 10000000;      // 1 reference_time = 100ns    constexpr int REFTIMES_PER_MILLISEC = 10000;    // 初始化 IAudioClient 对象    const REFERENCE_TIME hnsRequestedDuration = 2 * REFTIMES_PER_SEC; // 1s    hr = pAudioClient->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_LOOPBACK, hnsRequestedDuration, 0, pDeviceFormat, nullptr);    exit_on_failed(hr);    // 获得缓冲区大小    UINT32 bufferFrameCount{};    hr = pAudioClient->GetBufferSize(&bufferFrameCount);    exit_on_failed(hr);    // 由 IAudioClient 对象 得到 IAudioCaptureClient 对象,也就是将音频播放设备视为录音设备    CComPtr pCaptureClient;    hr = pAudioClient->GetService(__uuidof(IAudioCaptureClient), (void**)&pCaptureClient);    exit_on_failed(hr);        // 开始录音    hr = pAudioClient->Start();    exit_on_failed(hr);    const REFERENCE_TIME hnsActualDuration = (long long)REFTIMES_PER_SEC * bufferFrameCount / pDeviceFormat->nSamplesPerSec;    std::ofstream ofile("./out.wav", std::ios::binary);    if (!ofile) {        exit(-1);    }    // 写入各种 header 信息    constexpr UINT32 sizePlaceholder{};    // master RIFF chunk    ofile.write("RIFF", 4);    ofile.write((const char*)&sizePlaceholder, 4);    ofile.write("WAVE", 4);    // 12    // fmt chunk    ofile.write("fmt ", 4);    UINT32 fmt_ckSize = sizeof(WAVEFORMATEX) + pDeviceFormat->cbSize;    ofile.write((const char*)&fmt_ckSize, 4);    {        auto p = pDeviceFormat.Detach();        ofile.write((const char*)p, fmt_ckSize);        pDeviceFormat.Attach(p);    }    // 8 + fmt_ckSize    // fact chunk    bool has_fact_chunt = pDeviceFormat->wFormatTag != WAVE_FORMAT_PCM;    if (has_fact_chunt) {        ofile.write("fact", 4);        UINT32 fact_ckSize = 4;        ofile.write((const char*)&fact_ckSize, 4);        DWORD dwSampleLength{};        ofile.write((const char*)&dwSampleLength, 4);    }    // 12    // data chunk    ofile.write("data", 4);    ofile.write((const char*)&sizePlaceholder, 4);    UINT32 data_ckSize = 0; // samples data 的大小    UINT32 frame_count = 0; // 帧数    constexpr int max_duration = 60;    // 录制 60s    int seconds{};                      // 已经录制的时间    time_t t_begin = time(NULL);    //UINT32     do {        // 睡眠一定时间,防止CPU占用率高        Sleep(9);        BYTE* pData{};                  // samples 数据        UINT32 numFramesAvailable{};    // 缓冲区有多少帧        DWORD dwFlags{};        hr = pCaptureClient->GetBuffer(&pData, &numFramesAvailable, &dwFlags, NULL, NULL);        exit_on_failed(hr);        int frame_bytes = pDeviceFormat->nChannels * pDeviceFormat->wBitsPerSample / 8;        int count = numFramesAvailable * frame_bytes;        ofile.write((const char*)pData, count);        data_ckSize += count;        frame_count += numFramesAvailable;        seconds = frame_count / pDeviceFormat->nSamplesPerSec;        std::cout << "numFramesAvailable: " << numFramesAvailable << " seconds: " << seconds <ReleaseBuffer(numFramesAvailable);        exit_on_failed(hr);    } while (seconds < max_duration);    // 检测实际花了多久,实际时间 - max_duration = 延迟    time_t t_end = time(NULL);    std::cout << "use wall clock: " << t_end - t_begin << "s" << std::endl;    if (data_ckSize % 2) {        ofile.put(0);        ++data_ckSize;    }    UINT32 wave_ckSize = 4 + (8 + fmt_ckSize) + (8 + data_ckSize);    ofile.seekp(4);    ofile.write((const char*)&wave_ckSize, 4);    if (has_fact_chunt) {        ofile.seekp(12 + (8 + fmt_ckSize) + 8);        ofile.write((const char*)&frame_count, 4);    }    ofile.seekp(12 + (8 + fmt_ckSize) + 12 + 4);    ofile.write((const char*)&data_ckSize, 4);    ofile.close();    //所有 COM 对象和 Heap 都会自动释放}void printEndpoints(CComPtr pColletion){    HRESULT hr{};    UINT count{};    hr = pColletion->GetCount(&count);    exit_on_failed(hr);    for (UINT i = 0; i < count; ++i) {        CComPtr pEndpoint;        hr = pColletion->Item(i, &pEndpoint);        exit_on_failed(hr);        CComHeapPtr pwszID;        hr = pEndpoint->GetId(&pwszID);        exit_on_failed(hr);        CComPtr pProps;        hr = pEndpoint->OpenPropertyStore(STGM_READ, &pProps);        exit_on_failed(hr);        PROPVARIANT varName;        PropVariantInit(&varName);        hr = pProps->GetValue(PKEY_Device_FriendlyName, &varName);        exit_on_failed(hr);        std::cout << wchars_to_mbs(varName.pwszVal) << std::endl;        PropVariantClear(&varName);    }}constexpr inline void exit_on_failed(HRESULT hr) {    if (FAILED(hr)) {        exit(-1);    }}// 汉字会有编码问题,全部转成窄字符std::string wchars_to_mbs(const wchar_t* src){    UINT cp = GetACP();    int ccWideChar = (int)wcslen(src);    int n = WideCharToMultiByte(cp, 0, src, ccWideChar, 0, 0, 0, 0);    std::vector buf(n);    WideCharToMultiByte(cp, 0, src, ccWideChar, buf.data(), (int)buf.size(), 0, 0);    std::string dst(buf.data(), buf.size());    return dst;}

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