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使用 Windows Core Audio APs 进行 Loopback Recording 并生成 WAV 文件

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参考文档COM Coding PracticesAudio File Format SpecificationsCore Audio APIsLoopback 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 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<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 CoTaskMemFreeCComPtr<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 = 100nsconstexpr int REFTIMES_PER_MILLISEC = 10000;// 初始化 IAudioClient 对象const REFERENCE_TIME hnsRequestedDuration = 2 * REFTIMES_PER_SEC; // 1shr = 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 chunkofile.write("RIFF", 4);ofile.write((const char*)&sizePlaceholder, 4);ofile.write("WAVE", 4);// 12// fmt chunkofile.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 chunkbool 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 chunkofile.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 60sint seconds{};// 已经录制的时间time_t t_begin = time(NULL);//UINT32do {// 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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