参考文档
COM Coding Practices
Audio File Format Specifications
Core Audio APIs
Loopback Recording
#include <iostream> #include <fstream> #include <vector> #include <mmdeviceapi.h> #include <combaseapi.h> #include <atlbase.h> #include <Functiondiscoverykeys_devpkey.h> #include <Audioclient.h> #include <Audiopolicy.h> // 利用RAII手法，自动调用 CoUninitialize class 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<IMMDeviceCollection> 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<IMMDeviceEnumerator> pEnumerator; hr = pEnumerator.CoCreateInstance(__uuidof(MMDeviceEnumerator)); exit_on_failed(hr); // 打印所有可用的音频设备 //CComPtr<IMMDeviceCollection> 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<IMMDevice> 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<IPropertyStore> 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<IAudioClient> 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<WAVEFORMATEX> 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<IAudioCaptureClient> 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 << std::endl; hr = pCaptureClient->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<IMMDeviceCollection> pColletion) { HRESULT hr{}; UINT count{}; hr = pColletion->GetCount(&count); exit_on_failed(hr); for (UINT i = 0; i < count; ++i) { CComPtr<IMMDevice> pEndpoint; hr = pColletion->Item(i, &pEndpoint); exit_on_failed(hr); CComHeapPtr<WCHAR> pwszID; hr = pEndpoint->GetId(&pwszID); exit_on_failed(hr); CComPtr<IPropertyStore> 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<char> 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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