MFSampleExtension_Encryption_ProtectionScheme attribute

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Specifies the protection scheme for encrypted samples.

Data type

UINT32

Remarks

The value of this attribute is a member of the MFSampleEncryptionProtectionScheme enumeration. In cases where the media source is MP4-based, the value is set based off the value of the scheme_type field within the scheme type box (‘schm’) in the MP4 header (‘moov’ or ‘moof’).

If the scheme_type field in an MP4-based file, or stream, is set to ‘cenc’ or ‘cbc1’, then the MFSampleExtension_Encryption_ProtectionScheme attribute should be set to PROTECTION_SCHEME_AES_CTR or PROTECTION_SCHEME_CBC, respectively, and no values should be set for MFSampleExtension_Encryption_CryptByteBlock and MFSampleExtension_Encryption_SkipByteBlock.

If the scheme_type field in an MP4-based file, or stream, is set to ‘cens’ or ‘cbcs’, then the MFSampleExtension_Encryption_ProtectionScheme attribute should be set to PROTECTION_SCHEME_AES_CTR or PROTECTION_SCHEME_CBC, respectively, and MFSampleExtension_Encryption_CryptByteBlock and MFSampleExtension_Encryption_SkipByteBlock must be set using the values in the ‘tenc’ box.

Examples

The following example shows how to set the MFSampleExtension_Encryption_ProtectionScheme and the associated MFSampleExtension_Encryption_CryptByteBlock and MFSampleExtension_Encryption_SkipByteBlock attributes.

HRESULT AddEncryptionAttributes(_In_ IMFSample* pSample, _In_ bool fIsEncrypted)
{
      HRESULT hr = S_OK;

      if (fIsEncrypted)
	{
		//Set Encryption Protection Scheme
		hr = pSample->UINT32(MFSampleExtension_Encryption_ProtectionScheme,
			SAMPLE_ENCRYPTION_PROTECTION_SCHEME_AES_CBC);
            if (FAILED(hr))
                return hr;

		//Set the Initialization Vector (IV)
  //(spSampleEncryptionData is omitted from this example for simplicity.) 
		hr = pSample->SetBlob(MFSampleExtension_Encryption_SampleID, 
			(BYTE*)(spSampleEncryptionData->m_pInitializationVector),
			spSampleEncryptionData->m_bIVSize);
            if (FAILED(hr))
                return hr;

		//Set crypt and skip byte blocks for pattern encryption
		hr = pSample->SetUINT32(MFSampleExtension_Encryption_CryptByteBlock, 1);
            if (FAILED(hr))
                return hr;

		hr = pSample->SetUINT32(MFSampleExtension_Encryption_SkipByteBlock, 9);
            if (FAILED(hr))
                return hr;
	}
      return hr;
}

Requirements