MFTranscodeGetAudioOutputAvailableTypes function (mfidl.h)

Gets a list of output formats from an audio encoder.

Syntax

HRESULT MFTranscodeGetAudioOutputAvailableTypes(
  [in]  REFGUID       guidSubType,
  [in]  DWORD         dwMFTFlags,
  [in]  IMFAttributes *pCodecConfig,
  [out] IMFCollection **ppAvailableTypes
);

Parameters

[in] guidSubType

Specifies the subtype of the output media. The encoder uses this value as a filter when it is enumerating the available output types. For information about the audio subtypes, see Audio Subtype GUIDs.

[in] dwMFTFlags

Bitwise OR of zero or more flags from the _MFT_ENUM_FLAG enumeration.

[in] pCodecConfig

A pointer to the IMFAttributes interface of an attribute store. The attribute store specifies the encoder configuration settings. This parameter can be NULL. The attribute store can hold any of the following attributes.

[out] ppAvailableTypes

Receives a pointer to the IMFCollection interface of a collection object that contains a list of preferred audio media types. The collection contains IMFMediaType pointers. The caller must release the interface pointer.

Return value

The function returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Remarks

This function assumes the encoder will be used in its default encoding mode, which is typically constant bit-rate (CBR) encoding. Therefore, the types returned by the function might not work with other modes, such as variable bit-rate (VBR) encoding.

Internally, this function works by calling MFTEnumEx to find a matching encoder, and then calling IMFTransform::GetOutputAvailableType to get the encoder's output types.

Examples

The following example creates a transcode profile for Windows Media Audio (WMA).

template <class Q>
HRESULT GetCollectionObject(IMFCollection *pCollection, DWORD index, Q **ppObj)
{
    IUnknown *pUnk;
    HRESULT hr = pCollection->GetElement(index, &pUnk);
    if (SUCCEEDED(hr))
    {
        hr = pUnk->QueryInterface(IID_PPV_ARGS(ppObj));
        pUnk->Release();
    }
    return hr;
}

HRESULT CreateTranscodeProfile(IMFTranscodeProfile **ppProfile)
{
    IMFTranscodeProfile *pProfile = NULL;     // Transcode profile.
    IMFCollection   *pAvailableTypes = NULL;  // List of audio media types.
    IMFMediaType    *pAudioType = NULL;       // Audio media type.
    IMFAttributes   *pAudioAttrs = NULL;      // Copy of the audio media type.
    IMFAttributes   *pContainer = NULL;       // Container attributes.

    DWORD dwMTCount = 0;
    
    // Create an empty transcode profile.
    HRESULT hr = MFCreateTranscodeProfile(&pProfile);
    if (FAILED(hr))
    {
        goto done;
    }

    // Get output media types for the Windows Media audio encoder.

    // Enumerate all codecs except for codecs with field-of-use restrictions.
    // Sort the results.

    DWORD dwFlags = 
        (MFT_ENUM_FLAG_ALL & (~MFT_ENUM_FLAG_FIELDOFUSE)) | 
        MFT_ENUM_FLAG_SORTANDFILTER;

    hr = MFTranscodeGetAudioOutputAvailableTypes(MFAudioFormat_WMAudioV9, 
        dwFlags, NULL, &pAvailableTypes);
    if (FAILED(hr))
    {
        goto done;
    }

    hr = pAvailableTypes->GetElementCount(&dwMTCount);
    if (FAILED(hr))
    {
        goto done;
    }
    if (dwMTCount == 0)
    {
        hr = E_FAIL;
        goto done;
    }

    // Get the first audio type in the collection and make a copy.
    hr = GetCollectionObject(pAvailableTypes, 0, &pAudioType);
    if (FAILED(hr))
    {
        goto done;
    }

    hr = MFCreateAttributes(&pAudioAttrs, 0);       
    if (FAILED(hr))
    {
        goto done;
    }

    hr = pAudioType->CopyAllItems(pAudioAttrs);
    if (FAILED(hr))
    {
        goto done;
    }

    // Set the audio attributes on the profile.
    hr = pProfile->SetAudioAttributes(pAudioAttrs);
    if (FAILED(hr))
    {
        goto done;
    }

    // Set the container attributes.
    hr = MFCreateAttributes(&pContainer, 1);
    if (FAILED(hr))
    {
        goto done;
    }

    hr = pContainer->SetGUID(MF_TRANSCODE_CONTAINERTYPE, MFTranscodeContainerType_ASF);
    if (FAILED(hr))
    {
        goto done;
    }

    hr = pProfile->SetContainerAttributes(pContainer);
    if (FAILED(hr))
    {
        goto done;
    }

    *ppProfile = pProfile;
    (*ppProfile)->AddRef();

done:
    SafeRelease(&pProfile);
    SafeRelease(&pAvailableTypes);
    SafeRelease(&pAudioType);
    SafeRelease(&pAudioAttrs);
    SafeRelease(&pContainer);
    return hr;
}

Requirements

See also

IMFCollection::GetElement

MFCreateTranscodeProfile

Media Foundation Functions

Tutorial: Encoding a WMA File