编码器示例代码
本主题演示一些示例代码，这些代码将 Windows Media Audio (WMA) 编码器包装在名为 的 CWmaEncoderC++ 类中。
- 类声明
- 初始化
- SetEncodingType
- SetInputType
- GetOutputType
- GetLeakyBucket1
- ProcessInput
- ProcessOutput
- 排水
- 相关主题
以下几个主题引用了此代码：
在媒体基础中，编码器实现为 媒体基础转换 (MRT) 并公开 IMFTransform 接口。
类声明
enum EncodeMode
{
EncodeMode_CBR,
EncodeMode_VBR_Quality,
EncodeMode_VBR_Peak,
EncodeMode_VBR_Unconstrained,
};
struct LeakyBucket
{
DWORD dwBitrate;
DWORD msBufferSize;
DWORD msInitialBufferFullness;
};
class CWmaEncoder
{
public:
CWmaEncoder()
: m_pMFT(NULL), m_dwInputID(0), m_dwOutputID(0), m_pOutputType(NULL)
{
}
~CWmaEncoder()
{
SafeRelease(&m_pMFT);
SafeRelease(&m_pOutputType);
}
HRESULT Initialize();
HRESULT SetEncodingType(EncodeMode mode);
HRESULT SetInputType(IMFMediaType* pMediaType);
HRESULT GetOutputType(IMFMediaType** ppMediaType);
HRESULT GetLeakyBucket1(LeakyBucket *pBucket);
HRESULT ProcessInput(IMFSample* pSample);
HRESULT ProcessOutput(IMFSample **ppSample);
HRESULT Drain();
protected:
DWORD m_dwInputID; // Input stream ID.
DWORD m_dwOutputID; // Output stream ID.
IMFTransform *m_pMFT; // Pointer to the encoder MFT.
IMFMediaType *m_pOutputType; // Output media type of the encoder.
};
Initialize
方法 Initialize 创建 WMA 编码器的实例。
HRESULT CWmaEncoder::Initialize()
{
CLSID *pCLSIDs = NULL; // Pointer to an array of CLISDs.
UINT32 count = 0; // Size of the array.
IMFMediaType* pOutMediaType = NULL;
// Look for a encoder.
MFT_REGISTER_TYPE_INFO toutinfo;
toutinfo.guidMajorType = MFMediaType_Audio;
toutinfo.guidSubtype = MFAudioFormat_WMAudioV9;
HRESULT hr = S_OK;
hr = MFTEnum(
MFT_CATEGORY_AUDIO_ENCODER,
0, // Reserved
NULL, // Input type to match.
&toutinfo, // Output type to match.
NULL, // Attributes to match. (None.)
&pCLSIDs, // Receives a pointer to an array of CLSIDs.
&count // Receives the size of the array.
);
if (SUCCEEDED(hr))
{
if (count == 0)
{
hr = MF_E_TOPO_CODEC_NOT_FOUND;
}
}
//Create the MFT decoder
if (SUCCEEDED(hr))
{
hr = CoCreateInstance(pCLSIDs[0], NULL,
CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&m_pMFT));
}
return hr;
}
SetEncodingType
HRESULT CWmaEncoder::SetEncodingType(EncodeMode mode)
{
if (!m_pMFT)
{
return MF_E_NOT_INITIALIZED;
}
IPropertyStore* pProp = NULL;
PROPVARIANT var;
//Query the encoder for its property store
HRESULT hr = m_pMFT->QueryInterface(IID_PPV_ARGS(&pProp));
if (FAILED(hr))
{
goto done;
}
switch (mode)
{
case EncodeMode_CBR:
//Set the VBR property to FALSE, which indicates CBR encoding
//By default, encoding mode is set to CBR
var.vt = VT_BOOL;
var.boolVal = FALSE;
hr = pProp->SetValue(MFPKEY_VBRENABLED, var);
break;
default:
hr = E_NOTIMPL;
}
done:
SafeRelease(&pProp);
return hr;
}
SetInputType
HRESULT CWmaEncoder::SetInputType(IMFMediaType* pMediaType)
{
if (!m_pMFT)
{
return MF_E_NOT_INITIALIZED;
}
SafeRelease(&m_pOutputType);
IMFMediaType *pOutputType = NULL;
HRESULT hr = m_pMFT->GetStreamIDs(1, &m_dwInputID, 1, &m_dwOutputID);
if (hr == E_NOTIMPL)
{
// The stream identifiers are zero-based.
m_dwInputID = 0;
m_dwOutputID = 0;
hr = S_OK;
}
else if (FAILED(hr))
{
goto done;
}
// Set the input type to the one passed by the application
hr = m_pMFT->SetInputType(m_dwInputID, pMediaType, 0);
if (FAILED(hr))
{
goto done;
}
// Loop through the available output types
for (DWORD iType = 0; ; iType++)
{
hr = m_pMFT->GetOutputAvailableType(m_dwOutputID, iType, &pOutputType);
if (FAILED(hr))
{
goto done;
}
hr = m_pMFT->SetOutputType(m_dwOutputID, pOutputType, 0);
if (SUCCEEDED(hr))
{
m_pOutputType = pOutputType;
m_pOutputType->AddRef();
break;
}
SafeRelease(&pOutputType);
}
done:
SafeRelease(&pOutputType);
return hr;
}
GetOutputType
HRESULT CWmaEncoder::GetOutputType(IMFMediaType** ppMediaType)
{
if (m_pOutputType == NULL)
{
return MF_E_TRANSFORM_TYPE_NOT_SET;
}
*ppMediaType = m_pOutputType;
(*ppMediaType)->AddRef();
return S_OK;
};
GetLeakyBucket1
HRESULT CWmaEncoder::GetLeakyBucket1(LeakyBucket *pBucket)
{
if (m_pMFT == NULL || m_pOutputType == NULL)
{
return MF_E_NOT_INITIALIZED;
}
ZeroMemory(pBucket, sizeof(*pBucket));
// Get the bit rate.
pBucket->dwBitrate = 8 * MFGetAttributeUINT32(
m_pOutputType, MF_MT_AUDIO_AVG_BYTES_PER_SECOND, 0);
// Get the buffer window.
IWMCodecLeakyBucket *pLeakyBuckets = NULL;
HRESULT hr = m_pMFT->QueryInterface(IID_PPV_ARGS(&pLeakyBuckets));
if (SUCCEEDED(hr))
{
ULONG ulBuffer = 0;
hr = pLeakyBuckets->GetBufferSizeBits(&ulBuffer);
if (SUCCEEDED(hr))
{
pBucket->msBufferSize = ulBuffer / (pBucket->dwBitrate / 1000);
}
pLeakyBuckets->Release();
}
return S_OK;
}
ProcessInput
HRESULT CWmaEncoder::ProcessInput(IMFSample* pSample)
{
if (m_pMFT == NULL)
{
return MF_E_NOT_INITIALIZED;
}
return m_pMFT->ProcessInput(m_dwInputID, pSample, 0);
}
ProcessOutput
HRESULT CWmaEncoder::ProcessOutput(IMFSample **ppSample)
{
if (m_pMFT == NULL)
{
return MF_E_NOT_INITIALIZED;
}
*ppSample = NULL;
IMFMediaBuffer* pBufferOut = NULL;
IMFSample* pSampleOut = NULL;
DWORD dwStatus;
MFT_OUTPUT_STREAM_INFO mftStreamInfo = { 0 };
MFT_OUTPUT_DATA_BUFFER mftOutputData = { 0 };
HRESULT hr = m_pMFT->GetOutputStreamInfo(m_dwOutputID, &mftStreamInfo);
if (FAILED(hr))
{
goto done;
}
//create a buffer for the output sample
hr = MFCreateMemoryBuffer(mftStreamInfo.cbSize, &pBufferOut);
if (FAILED(hr))
{
goto done;
}
//Create the output sample
hr = MFCreateSample(&pSampleOut);
if (FAILED(hr))
{
goto done;
}
//Add the output buffer
hr = pSampleOut->AddBuffer(pBufferOut);
if (FAILED(hr))
{
goto done;
}
//Set the output sample
mftOutputData.pSample = pSampleOut;
//Set the output id
mftOutputData.dwStreamID = m_dwOutputID;
//Generate the output sample
hr = m_pMFT->ProcessOutput(0, 1, &mftOutputData, &dwStatus);
if (hr == MF_E_TRANSFORM_NEED_MORE_INPUT)
{
hr = S_OK;
goto done;
}
// TODO: Handle MF_E_TRANSFORM_STREAM_CHANGE
if (FAILED(hr))
{
goto done;
}
*ppSample = pSampleOut;
(*ppSample)->AddRef();
done:
SafeRelease(&pBufferOut);
SafeRelease(&pSampleOut);
return hr;
};
清空
HRESULT CWmaEncoder::Drain()
{
if (m_pMFT == NULL)
{
return MF_E_NOT_INITIALIZED;
}
return m_pMFT->ProcessMessage(MFT_MESSAGE_COMMAND_DRAIN, m_dwInputID);
}
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