我正在阅读Capturing a stream或Loopback recording之类的文档，但找不到关于如何从Loopback记录块的很好的可重现示例（包括include，build指令等）。 Windows WASAPI的音频设备（有时称为“您听到的内容”，“立体声混音”）。
您是否有一个简单的可重现示例，该示例演示如何在C ++中以循环方式从WASAPI设备记录音频块？
这是Python中类似的（有效的）示例：
import soundcard as sc # installed with: pip install soundcard
lb = sc.all_microphones(include_loopback=True)[0]
with lb.recorder(samplerate=44100) as mic:
while True:
data = mic.record(numframes=None)
print(data) # chunks of audio data (448 samples x 2 channels as an array by default)
答案 0 :(得分：1)
这是回送模式音频捕获的示例。
根据文档Capturing a stream，制作Loopback recording指出的某些版本，如下所示：
// In the call to the IMMDeviceEnumerator::GetDefaultAudioEndpoint method, change the first parameter (dataFlow) from eCapture to eRender.
hr = pEnumerator->GetDefaultAudioEndpoint(
eRender, eConsole, &pDevice);
...
// In the call to the IAudioClient::Initialize method, change the value of the second parameter (StreamFlags) from 0 to AUDCLNT_STREAMFLAGS_LOOPBACK.
hr = pAudioClient->Initialize(
AUDCLNT_SHAREMODE_SHARED,
AUDCLNT_STREAMFLAGS_LOOPBACK,
hnsRequestedDuration,
0,
pwfx,
NULL);
文档中缺少的部分：CopyData()和写入文件功能（WriteWaveHeader()和FinishWaveFile()）。以下显示了这些功能实现的示例。有关更多详细信息，请访问博客Sample - WASAPI loopback capture (record what you hear)。
HRESULT MyAudioSink::CopyData(BYTE* pData, UINT32 NumFrames, BOOL* pDone, WAVEFORMATEX* pwfx, HMMIO hFile)
{
HRESULT hr = S_OK;
if (0 == NumFrames) {
wprintf(L"IAudioCaptureClient::GetBuffer said to read 0 frames\n");
return E_UNEXPECTED;
}
LONG lBytesToWrite = NumFrames * pwfx->nBlockAlign;
#pragma prefast(suppress: __WARNING_INCORRECT_ANNOTATION, "IAudioCaptureClient::GetBuffer SAL annotation implies a 1-byte buffer")
LONG lBytesWritten = mmioWrite(hFile, reinterpret_cast<PCHAR>(pData), lBytesToWrite);
if (lBytesToWrite != lBytesWritten) {
wprintf(L"mmioWrite wrote %u bytes : expected %u bytes", lBytesWritten, lBytesToWrite);
return E_UNEXPECTED;
}
static int CallCount = 0;
cout << "CallCount = " << CallCount++ << "NumFrames: " << NumFrames << endl ;
if (clock() > 10 * CLOCKS_PER_SEC) //Record 10 seconds. From the first time call clock() at the beginning of the main().
*pDone = true;
return S_OK;
}
HRESULT WriteWaveHeader(HMMIO hFile, LPCWAVEFORMATEX pwfx, MMCKINFO* pckRIFF, MMCKINFO* pckData) {
MMRESULT result;
// make a RIFF/WAVE chunk
pckRIFF->ckid = MAKEFOURCC('R', 'I', 'F', 'F');
pckRIFF->fccType = MAKEFOURCC('W', 'A', 'V', 'E');
result = mmioCreateChunk(hFile, pckRIFF, MMIO_CREATERIFF);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"RIFF/WAVE\") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// make a 'fmt ' chunk (within the RIFF/WAVE chunk)
MMCKINFO chunk;
chunk.ckid = MAKEFOURCC('f', 'm', 't', ' ');
result = mmioCreateChunk(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"fmt \") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// write the WAVEFORMATEX data to it
LONG lBytesInWfx = sizeof(WAVEFORMATEX) + pwfx->cbSize;
LONG lBytesWritten =
mmioWrite(
hFile,
reinterpret_cast<PCHAR>(const_cast<LPWAVEFORMATEX>(pwfx)),
lBytesInWfx
);
if (lBytesWritten != lBytesInWfx) {
wprintf(L"mmioWrite(fmt data) wrote %u bytes; expected %u bytes", lBytesWritten, lBytesInWfx);
return E_FAIL;
}
// ascend from the 'fmt ' chunk
result = mmioAscend(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"fmt \" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// make a 'fact' chunk whose data is (DWORD)0
chunk.ckid = MAKEFOURCC('f', 'a', 'c', 't');
result = mmioCreateChunk(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"fmt \") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// write (DWORD)0 to it
// this is cleaned up later
DWORD frames = 0;
lBytesWritten = mmioWrite(hFile, reinterpret_cast<PCHAR>(&frames), sizeof(frames));
if (lBytesWritten != sizeof(frames)) {
wprintf(L"mmioWrite(fact data) wrote %u bytes; expected %u bytes", lBytesWritten, (UINT32)sizeof(frames));
return E_FAIL;
}
// ascend from the 'fact' chunk
result = mmioAscend(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"fact\" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// make a 'data' chunk and leave the data pointer there
pckData->ckid = MAKEFOURCC('d', 'a', 't', 'a');
result = mmioCreateChunk(hFile, pckData, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"data\") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
return S_OK;
}
HRESULT FinishWaveFile(HMMIO hFile, MMCKINFO* pckRIFF, MMCKINFO* pckData) {
MMRESULT result;
result = mmioAscend(hFile, pckData, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"data\" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
result = mmioAscend(hFile, pckRIFF, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"RIFF/WAVE\" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
return S_OK;
}
在WriteWaveHeader之前致电pAudioClient->Start()。在FinishWaveFile之后致电pAudioClient->Stop()。
因此，它将记录在Windows上播放约10秒的音频。
更新＃1：
#include <Windows.h>
#include <mmsystem.h>
#include <mmdeviceapi.h>
#include <audioclient.h>
#include <time.h>
#include <iostream>
int main()
{
clock();
HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
// Create file
MMIOINFO mi = { 0 };
hFile = mmioOpen(
// some flags cause mmioOpen write to this buffer
// but not any that we're using
(LPWSTR)fileName,
&mi,
MMIO_WRITE | MMIO_CREATE
);
if (NULL == hFile) {
wprintf(L"mmioOpen(\"%ls\", ...) failed. wErrorRet == %u", fileName, GetLastError());
return E_FAIL;
}
MyAudioSink AudioSink;
RecordAudioStream(&AudioSink);
mmioClose(hFile, 0);
CoUninitialize();
return 0;
}
编译命令：
cl -DUNICODE loopbackCapture.cpp /link winmm.lib user32.lib Kernel32.lib Ole32.lib
更新＃2：
#include <Windows.h>
#include <mmsystem.h>
#include <mmdeviceapi.h>
#include <audioclient.h>
#include <time.h>
#include <iostream>
using namespace std;
#pragma comment(lib, "Winmm.lib")
WCHAR fileName[] = L"loopback-capture.wav";
BOOL bDone = FALSE;
HMMIO hFile = NULL;
// REFERENCE_TIME time units per second and per millisecond
#define REFTIMES_PER_SEC 10000000
#define REFTIMES_PER_MILLISEC 10000
#define EXIT_ON_ERROR(hres) \
if (FAILED(hres)) { goto Exit; }
#define SAFE_RELEASE(punk) \
if ((punk) != NULL) \
{ (punk)->Release(); (punk) = NULL; }
const CLSID CLSID_MMDeviceEnumerator = __uuidof(MMDeviceEnumerator);
const IID IID_IMMDeviceEnumerator = __uuidof(IMMDeviceEnumerator);
const IID IID_IAudioClient = __uuidof(IAudioClient);
const IID IID_IAudioCaptureClient = __uuidof(IAudioCaptureClient);
class MyAudioSink
{
public:
HRESULT CopyData(BYTE* pData, UINT32 NumFrames, BOOL* pDone, WAVEFORMATEX* pwfx, HMMIO hFile);
};
HRESULT WriteWaveHeader(HMMIO hFile, LPCWAVEFORMATEX pwfx, MMCKINFO* pckRIFF, MMCKINFO* pckData);
HRESULT FinishWaveFile(HMMIO hFile, MMCKINFO* pckRIFF, MMCKINFO* pckData);
HRESULT RecordAudioStream(MyAudioSink* pMySink);
int main()
{
clock();
HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
// Create file
MMIOINFO mi = { 0 };
hFile = mmioOpen(
// some flags cause mmioOpen write to this buffer
// but not any that we're using
(LPWSTR)fileName,
&mi,
MMIO_WRITE | MMIO_CREATE
);
if (NULL == hFile) {
wprintf(L"mmioOpen(\"%ls\", ...) failed. wErrorRet == %u", fileName, GetLastError());
return E_FAIL;
}
MyAudioSink AudioSink;
RecordAudioStream(&AudioSink);
mmioClose(hFile, 0);
CoUninitialize();
return 0;
}
HRESULT MyAudioSink::CopyData(BYTE* pData, UINT32 NumFrames, BOOL* pDone, WAVEFORMATEX* pwfx, HMMIO hFile)
{
HRESULT hr = S_OK;
if (0 == NumFrames) {
wprintf(L"IAudioCaptureClient::GetBuffer said to read 0 frames\n");
return E_UNEXPECTED;
}
LONG lBytesToWrite = NumFrames * pwfx->nBlockAlign;
#pragma prefast(suppress: __WARNING_INCORRECT_ANNOTATION, "IAudioCaptureClient::GetBuffer SAL annotation implies a 1-byte buffer")
LONG lBytesWritten = mmioWrite(hFile, reinterpret_cast<PCHAR>(pData), lBytesToWrite);
if (lBytesToWrite != lBytesWritten) {
wprintf(L"mmioWrite wrote %u bytes : expected %u bytes", lBytesWritten, lBytesToWrite);
return E_UNEXPECTED;
}
static int CallCount = 0;
cout << "CallCount = " << CallCount++ << "NumFrames: " << NumFrames << endl ;
if (clock() > 10 * CLOCKS_PER_SEC) //Record 10 seconds. From the first time call clock() at the beginning of the main().
*pDone = true;
return S_OK;
}
HRESULT RecordAudioStream(MyAudioSink* pMySink)
{
HRESULT hr;
REFERENCE_TIME hnsRequestedDuration = REFTIMES_PER_SEC;
REFERENCE_TIME hnsActualDuration;
UINT32 bufferFrameCount;
UINT32 numFramesAvailable;
IMMDeviceEnumerator* pEnumerator = NULL;
IMMDevice* pDevice = NULL;
IAudioClient* pAudioClient = NULL;
IAudioCaptureClient* pCaptureClient = NULL;
WAVEFORMATEX* pwfx = NULL;
UINT32 packetLength = 0;
BYTE* pData;
DWORD flags;
MMCKINFO ckRIFF = { 0 };
MMCKINFO ckData = { 0 };
hr = CoCreateInstance(
CLSID_MMDeviceEnumerator, NULL,
CLSCTX_ALL, IID_IMMDeviceEnumerator,
(void**)& pEnumerator);
EXIT_ON_ERROR(hr)
hr = pEnumerator->GetDefaultAudioEndpoint(
eRender, eConsole, &pDevice);
EXIT_ON_ERROR(hr)
hr = pDevice->Activate(
IID_IAudioClient, CLSCTX_ALL,
NULL, (void**)& pAudioClient);
EXIT_ON_ERROR(hr)
hr = pAudioClient->GetMixFormat(&pwfx);
EXIT_ON_ERROR(hr)
hr = pAudioClient->Initialize(
AUDCLNT_SHAREMODE_SHARED,
AUDCLNT_STREAMFLAGS_LOOPBACK,
hnsRequestedDuration,
0,
pwfx,
NULL);
EXIT_ON_ERROR(hr)
// Get the size of the allocated buffer.
hr = pAudioClient->GetBufferSize(&bufferFrameCount);
EXIT_ON_ERROR(hr)
hr = pAudioClient->GetService(
IID_IAudioCaptureClient,
(void**)& pCaptureClient);
EXIT_ON_ERROR(hr)
hr = WriteWaveHeader((HMMIO)hFile, pwfx, &ckRIFF, &ckData);
if (FAILED(hr)) {
// WriteWaveHeader does its own logging
return hr;
}
// Calculate the actual duration of the allocated buffer.
hnsActualDuration = (double)REFTIMES_PER_SEC *
bufferFrameCount / pwfx->nSamplesPerSec;
hr = pAudioClient->Start(); // Start recording.
EXIT_ON_ERROR(hr)
// Each loop fills about half of the shared buffer.
while (bDone == FALSE)
{
// Sleep for half the buffer duration.
Sleep(hnsActualDuration / REFTIMES_PER_MILLISEC / 2);
hr = pCaptureClient->GetNextPacketSize(&packetLength);
EXIT_ON_ERROR(hr)
while (packetLength != 0)
{
// Get the available data in the shared buffer.
hr = pCaptureClient->GetBuffer(
&pData,
&numFramesAvailable,
&flags, NULL, NULL);
EXIT_ON_ERROR(hr)
if (flags & AUDCLNT_BUFFERFLAGS_SILENT)
{
pData = NULL; // Tell CopyData to write silence.
}
// Copy the available capture data to the audio sink.
hr = pMySink->CopyData(
pData, numFramesAvailable, &bDone, pwfx, (HMMIO)hFile);
EXIT_ON_ERROR(hr)
hr = pCaptureClient->ReleaseBuffer(numFramesAvailable);
EXIT_ON_ERROR(hr)
hr = pCaptureClient->GetNextPacketSize(&packetLength);
EXIT_ON_ERROR(hr)
}
}
hr = pAudioClient->Stop(); // Stop recording.
EXIT_ON_ERROR(hr)
hr = FinishWaveFile((HMMIO)hFile, &ckData, &ckRIFF);
if (FAILED(hr)) {
// FinishWaveFile does it's own logging
return hr;
}
Exit:
CoTaskMemFree(pwfx);
SAFE_RELEASE(pEnumerator)
SAFE_RELEASE(pDevice)
SAFE_RELEASE(pAudioClient)
SAFE_RELEASE(pCaptureClient)
return hr;
}
HRESULT WriteWaveHeader(HMMIO hFile, LPCWAVEFORMATEX pwfx, MMCKINFO* pckRIFF, MMCKINFO* pckData) {
MMRESULT result;
// make a RIFF/WAVE chunk
pckRIFF->ckid = MAKEFOURCC('R', 'I', 'F', 'F');
pckRIFF->fccType = MAKEFOURCC('W', 'A', 'V', 'E');
result = mmioCreateChunk(hFile, pckRIFF, MMIO_CREATERIFF);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"RIFF/WAVE\") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// make a 'fmt ' chunk (within the RIFF/WAVE chunk)
MMCKINFO chunk;
chunk.ckid = MAKEFOURCC('f', 'm', 't', ' ');
result = mmioCreateChunk(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"fmt \") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// write the WAVEFORMATEX data to it
LONG lBytesInWfx = sizeof(WAVEFORMATEX) + pwfx->cbSize;
LONG lBytesWritten =
mmioWrite(
hFile,
reinterpret_cast<PCHAR>(const_cast<LPWAVEFORMATEX>(pwfx)),
lBytesInWfx
);
if (lBytesWritten != lBytesInWfx) {
wprintf(L"mmioWrite(fmt data) wrote %u bytes; expected %u bytes", lBytesWritten, lBytesInWfx);
return E_FAIL;
}
// ascend from the 'fmt ' chunk
result = mmioAscend(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"fmt \" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// make a 'fact' chunk whose data is (DWORD)0
chunk.ckid = MAKEFOURCC('f', 'a', 'c', 't');
result = mmioCreateChunk(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"fmt \") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// write (DWORD)0 to it
// this is cleaned up later
DWORD frames = 0;
lBytesWritten = mmioWrite(hFile, reinterpret_cast<PCHAR>(&frames), sizeof(frames));
if (lBytesWritten != sizeof(frames)) {
wprintf(L"mmioWrite(fact data) wrote %u bytes; expected %u bytes", lBytesWritten, (UINT32)sizeof(frames));
return E_FAIL;
}
// ascend from the 'fact' chunk
result = mmioAscend(hFile, &chunk, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"fact\" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
// make a 'data' chunk and leave the data pointer there
pckData->ckid = MAKEFOURCC('d', 'a', 't', 'a');
result = mmioCreateChunk(hFile, pckData, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioCreateChunk(\"data\") failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
return S_OK;
}
HRESULT FinishWaveFile(HMMIO hFile, MMCKINFO* pckRIFF, MMCKINFO* pckData) {
MMRESULT result;
result = mmioAscend(hFile, pckData, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"data\" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
result = mmioAscend(hFile, pckRIFF, 0);
if (MMSYSERR_NOERROR != result) {
wprintf(L"mmioAscend(\"RIFF/WAVE\" failed: MMRESULT = 0x%08x", result);
return E_FAIL;
}
return S_OK;
}