Codice di esempio di streaming audio
[La funzionalità associata a questa pagina, DirectShow, è una funzionalità legacy. È stata sostituita da MediaPlayer, IMFMediaEngine e Audio/Video Capture in Media Foundation. Queste funzionalità sono state ottimizzate per Windows 10 e Windows 11. Microsoft consiglia vivamente che il nuovo codice usi MediaPlayer, IMFMediaEngine e Audio/Video Capture in Media Foundation invece di DirectShow, quando possibile. Microsoft suggerisce che il codice esistente che usa le API legacy venga riscritto per usare le nuove API, se possibile.
Nota
Queste API sono deprecate. Le applicazioni devono usare il filtro Sample Grabber o implementare un filtro personalizzato per ottenere dati da un grafico di filtro DirectShow.
L'esempio di codice seguente illustra come trasmettere dati audio usando le interfacce IAudioMediaStream, IAudioStreamSample, IMemoryData e IAudioData . Per brevità, questo esempio esegue un controllo degli errori minimo.
#include <windows.h>
#include <stdio.h>
#include <mmsystem.h>
#include <amstream.h>
class CWaveBuffer {
public:
~CWaveBuffer();
BOOL Init(HWAVEOUT hWave, int Size);
BOOL Write(PBYTE pData, int nBytes, int& BytesWritten);
void Flush();
private:
WAVEHDR m_Hdr;
HWAVEOUT m_hWave;
int m_nBytes;
};
class CWaveOut {
public:
CWaveOut(LPCWAVEFORMATEX Format, int nBuffers, int BufferSize);
~CWaveOut();
void Write(PBYTE Data, int nBytes);
void Flush();
void Wait();
void Reset();
private:
const HANDLE m_hSem;
const int m_nBuffers;
int m_CurrentBuffer;
BOOL m_NoBuffer;
CWaveBuffer *m_Hdrs;
HWAVEOUT m_hWave;
};
BOOL CWaveBuffer::Init(HWAVEOUT hWave, int Size)
{
m_hWave = hWave;
m_nBytes = 0;
/* Allocate a buffer and initialize the header. */
m_Hdr.lpData = (LPSTR)LocalAlloc(LMEM_FIXED, Size);
if (m_Hdr.lpData == NULL)
{
return FALSE;
}
m_Hdr.dwBufferLength = Size;
m_Hdr.dwBytesRecorded = 0;
m_Hdr.dwUser = 0;
m_Hdr.dwFlags = 0;
m_Hdr.dwLoops = 0;
m_Hdr.lpNext = 0;
m_Hdr.reserved = 0;
/* Prepare it. */
waveOutPrepareHeader(hWave, &m_Hdr, sizeof(WAVEHDR));
return TRUE;
}
CWaveBuffer::~CWaveBuffer()
{
if (m_Hdr.lpData)
{
waveOutUnprepareHeader(m_hWave, &m_Hdr, sizeof(WAVEHDR));
LocalFree(m_Hdr.lpData);
}
}
void CWaveBuffer::Flush()
{
// ASSERT(m_nBytes != 0);
m_nBytes = 0;
waveOutWrite(m_hWave, &m_Hdr, sizeof(WAVEHDR));
}
BOOL CWaveBuffer::Write(PBYTE pData, int nBytes, int& BytesWritten)
{
// ASSERT((DWORD)m_nBytes != m_Hdr.dwBufferLength);
BytesWritten = min((int)m_Hdr.dwBufferLength - m_nBytes, nBytes);
CopyMemory((PVOID)(m_Hdr.lpData + m_nBytes), (PVOID)pData, BytesWritten);
m_nBytes += BytesWritten;
if (m_nBytes == (int)m_Hdr.dwBufferLength)
{
/* Write it! */
m_nBytes = 0;
waveOutWrite(m_hWave, &m_Hdr, sizeof(WAVEHDR));
return TRUE;
}
return FALSE;
}
void CALLBACK WaveCallback(HWAVEOUT hWave, UINT uMsg, DWORD dwUser,
DWORD dw1, DWORD dw2)
{
if (uMsg == WOM_DONE)
{
ReleaseSemaphore((HANDLE)dwUser, 1, NULL);
}
}
CWaveOut::CWaveOut(LPCWAVEFORMATEX Format, int nBuffers, int BufferSize) :
m_nBuffers(nBuffers),
m_CurrentBuffer(0),
m_NoBuffer(TRUE),
m_hSem(CreateSemaphore(NULL, nBuffers, nBuffers, NULL)),
m_Hdrs(new CWaveBuffer[nBuffers]),
m_hWave(NULL)
{
/* Create wave device. */
waveOutOpen(&m_hWave,
WAVE_MAPPER,
Format,
(DWORD)WaveCallback,
(DWORD)m_hSem,
CALLBACK_FUNCTION);
/* Initialize the wave buffers. */
for (int i = 0; i < nBuffers; i++)
{
m_Hdrs[i].Init(m_hWave, BufferSize);
}
}
CWaveOut::~CWaveOut()
{
/* First, get the buffers back. */
waveOutReset(m_hWave);
/* Free the buffers. */
delete [] m_Hdrs;
/* Close the wave device. */
waveOutClose(m_hWave);
/* Free the semaphore. */
CloseHandle(m_hSem);
}
void CWaveOut::Flush()
{
if (!m_NoBuffer)
{
m_Hdrs[m_CurrentBuffer].Flush();
m_NoBuffer = TRUE;
m_CurrentBuffer = (m_CurrentBuffer + 1) % m_nBuffers;
}
}
void CWaveOut::Reset()
{
waveOutReset(m_hWave);
}
void CWaveOut::Write(PBYTE pData, int nBytes)
{
while (nBytes != 0)
{
/* Get a buffer if necessary. */
if (m_NoBuffer)
{
WaitForSingleObject(m_hSem, INFINITE);
m_NoBuffer = FALSE;
}
/* Write into a buffer. */
int nWritten;
if (m_Hdrs[m_CurrentBuffer].Write(pData, nBytes, nWritten))
{
m_NoBuffer = TRUE;
m_CurrentBuffer = (m_CurrentBuffer + 1) % m_nBuffers;
nBytes -= nWritten;
pData += nWritten;
}
else
{
// ASSERT(nWritten == nBytes);
break;
}
}
}
void CWaveOut::Wait()
{
/* Send any remaining buffers. */
Flush();
/* Wait for the buffers back. */
for (int i = 0; i < m_nBuffers; i++)
{
WaitForSingleObject(m_hSem, INFINITE);
}
LONG lPrevCount;
ReleaseSemaphore(m_hSem, m_nBuffers, &lPrevCount);
}
HRESULT RenderStreamToDevice(IMultiMediaStream *pMMStream)
{
WAVEFORMATEX wfx;
#define DATA_SIZE 5000
IMediaStream *pStream = NULL;
IAudioStreamSample *pSample = NULL;
IAudioMediaStream *pAudioStream = NULL;
IAudioData *pAudioData = NULL;
HRESULT hr = pMMStream->GetMediaStream(MSPID_PrimaryAudio, &pStream);
if (FAILED(hr))
{
return hr;
}
pStream->QueryInterface(IID_IAudioMediaStream, (void **)&pAudioStream);
pStream->Release();
hr = CoCreateInstance(CLSID_AMAudioData, NULL,
CLSCTX_INPROC_SERVER, IID_IAudioData, (void **)&pAudioData);
if (FAILED(hr))
{
pAudioStream->Release();
return hr;
}
PBYTE pBuffer = (PBYTE)LocalAlloc(LMEM_FIXED, DATA_SIZE);
if (pBuffer == NULL)
{
pAudioStream->Release();
pAudioData->Release();
return E_OUTOFMEMORY;
}
pAudioStream->GetFormat(&wfx);
pAudioData->SetBuffer(DATA_SIZE, pBuffer, 0);
pAudioData->SetFormat(&wfx);
hr = pAudioStream->CreateSample(pAudioData, 0, &pSample);
pAudioStream->Release();
if (FAILED(hr))
{
LocalFree((HLOCAL)pBuffer);
pAudioData->Release();
pSample->Release();
return hr;
}
CWaveOut WaveOut(&wfx, 4, 2048);
HANDLE hEvent = CreateEvent(FALSE, NULL, NULL, FALSE);
if (hEvent != 0)
{
int iTimes;
for (iTimes = 0; iTimes < 3; iTimes++)
{
DWORD dwStart = timeGetTime();
for (; ; )
{
hr = pSample->Update(0, hEvent, NULL, 0);
if (FAILED(hr) || hr == MS_S_ENDOFSTREAM)
{
break;
}
WaitForSingleObject(hEvent, INFINITE);
DWORD dwTimeDiff = timeGetTime() - dwStart;
// Limit to 10 seconds
if (dwTimeDiff > 10000) {
break;
}
DWORD dwLength;
pAudioData->GetInfo(NULL, NULL, &dwLength);
WaveOut.Write(pBuffer, dwLength);
}
pMMStream->Seek(0);
}
}
pAudioData->Release();
pSample->Release();
LocalFree((HLOCAL)pBuffer);
return S_OK;
}
HRESULT RenderFileToMMStream(
const char * szFileName,
IMultiMediaStream **ppMMStream)
{
if (strlen(szFileName) > MAX_PATH)
{
return E_INVALIDARG;
}
IAMMultiMediaStream *pAMStream;
HRESULT hr = CoCreateInstance(CLSID_AMMultiMediaStream, NULL,
CLSCTX_INPROC_SERVER, IID_IAMMultiMediaStream,
(void **)&pAMStream);
if (FAILED(hr))
{
return hr;
}
WCHAR wszName[MAX_PATH + 1];
MultiByteToWideChar(CP_ACP, 0, szFileName, -1, wszName,
MAX_PATH + 1);
pAMStream->Initialize(STREAMTYPE_READ, AMMSF_NOGRAPHTHREAD, NULL);
pAMStream->AddMediaStream(NULL, &MSPID_PrimaryAudio, 0, NULL);
hr = pAMStream->OpenFile(wszName, AMMSF_RUN);
{
if (SUCCEEDED(hr))
{
hr = pAMStream->QueryInterface(IID_IMultiMediaStream,
(void**)ppMMStream);
}
}
pAMStream->Release();
return hr;
}
int __cdecl main(int argc, char *argv[])
{
if (argc < 2)
{
printf("Specify a file name.\n");
exit(0);
}
IMultiMediaStream *pMMStream;
CoInitialize(NULL);
HRESULT hr = RenderFileToMMStream(argv[1], &pMMStream);
if (SUCCEEDED(hr))
{
RenderStreamToDevice(pMMStream);
pMMStream->Release();
}
CoUninitialize();
return 0;
}
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