Configuring Audio Decoding
Decoding Windows Media Audio content is much easier than encoding it. After creating an audio decoder object, set the input type by using the IMediaObject::SetInputType or IMFTransform::SetInputType method. The media type that you use for the decoder input must match the output type that was used when the content was encoded. This includes the extended format data appended to the WAVEFORMATEX structure. You must ensure that this data is correct, because the decoder cannot process samples without it.
After setting the input type, you can configure any decoder features you want to use. Decoder features, like those used for encoding, are set using the methods of IPropertyBag or IPropertyStore.
After the input type is set and all decoder features are configured, you can enumerate the output types supported by the decoder by making calls to IMediaObject::GetOutputType or IMFTransform::GetOutputType.