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Using the Windows Media Audio 9 Lossless Codec

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The Windows Media Audio 9 Lossless codec provides lossless audio encoding, which means that the uncompressed data delivered by the decoder contains all of the data that was in the original content.

The Windows Media Audio 9 Lossless codec is implemented in the encoder object with the class identifier CLSID_CWMAEncMediaObject, and in the decoder object with the class identifier CLSID_CWMADecMediaObject. The format tag of media types using this codec is 0x163.

Configuring the Encoder

Configure the lossless encoder in the same way that you configure the standard audio encoder. For more information, see Configuring Audio Encoding.

The only encoding mode supported by the lossless codec is quality based VBR. No output types with the lossless sub type are reported by the audio encoder object for any other encoding mode. For more information about enumerating types for encoding modes, see Enumerating Audio Types for Specific Encoding Modes.

Like the Windows Media Audio 10 Professional codec, the encoder input type must use the WAVEFORMATEXTENSIBLE structure, even if the content is stereo. For more information, see Using High-Definition Audio.

Decoding

Decoding audio compressed with the Windows Media Audio 9 Lossless codec is in most ways procedurally identical to decoding standard audio. However, the decoder enumerates output types with two channels and 16 bits per sample as a default. You must explicitly enable high-definition decoding. For more information, see Using High-Definition Audio

See Also